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          <link:loc xlink:type="locator" xlink:href="atra-20260630.xsd#atra_InterestRateOfRoyaltiesPercentage" xlink:label="atra_InterestRateOfRoyaltiesPercentage"/>
          <link:loc xlink:type="locator" xlink:href="atra-20260630.xsd#atra_SupplementalBalanceSheetInformationAbstract" xlink:label="atra_SupplementalBalanceSheetInformationAbstract"/>
          <link:loc xlink:type="locator" xlink:href="atra-20260630.xsd#atra_FujifilmMasterServicesAndSupplyAgreementMember" xlink:label="atra_FujifilmMasterServicesAndSupplyAgreementMember"/>
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          <link:loc xlink:type="locator" xlink:href="atra-20260630.xsd#atra_TwoThousandTwentyThreeATMFacilityMember" xlink:label="atra_TwoThousandTwentyThreeATMFacilityMember"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_IncreaseDecreaseInOtherNoncurrentLiabilities" xlink:label="us-gaap_IncreaseDecreaseInOtherNoncurrentLiabilities"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_PaymentsToAcquireLeaseReceivables" xlink:label="us-gaap_PaymentsToAcquireLeaseReceivables"/>
          <link:loc xlink:type="locator" xlink:href="atra-20260630.xsd#atra_MinimumPurchaseCommitmentsAccrued" xlink:label="atra_MinimumPurchaseCommitmentsAccrued"/>
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          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_AvailableForSaleSecuritiesDebtMaturitiesSingleMaturityDateAmortizedCostBasisAbstract" xlink:label="us-gaap_AvailableForSaleSecuritiesDebtMaturitiesSingleMaturityDateAmortizedCostBasisAbstract"/>
          <link:loc xlink:type="locator" xlink:href="atra-20260630.xsd#atra_LiabilityRelatedToTheSalesOfFutureRevenuesTableTextBlock" xlink:label="atra_LiabilityRelatedToTheSalesOfFutureRevenuesTableTextBlock"/>
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          <link:loc xlink:type="locator" xlink:href="atra-20260630.xsd#atra_MinimumCommitmentsExpense" xlink:label="atra_MinimumCommitmentsExpense"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ProceedsFromIssuanceOrSaleOfEquity" xlink:label="us-gaap_ProceedsFromIssuanceOrSaleOfEquity"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.sec.gov/dei/2025/dei-2025.xsd#dei_LocalPhoneNumber" xlink:label="dei_LocalPhoneNumber"/>
          <link:loc xlink:type="locator" xlink:href="atra-20260630.xsd#atra_TerritoryDomain" xlink:label="atra_TerritoryDomain"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_OtherLiabilitiesCurrent" xlink:label="us-gaap_OtherLiabilitiesCurrent"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognizedStockOptions" xlink:label="us-gaap_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognizedStockOptions"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ShortTermLeaseCost" xlink:label="us-gaap_ShortTermLeaseCost"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_FinanceLeaseLiabilityPaymentsDueYearTwo" xlink:label="us-gaap_FinanceLeaseLiabilityPaymentsDueYearTwo"/>
          <link:loc xlink:type="locator" xlink:href="atra-20260630.xsd#atra_MilestoneTypeNameDomain" xlink:label="atra_MilestoneTypeNameDomain"/>
          <link:loc xlink:type="locator" xlink:href="atra-20260630.xsd#atra_DecreaseIncreaseInOperatingLeaseAssetsAndLiabilitiesUponDerecognition" xlink:label="atra_DecreaseIncreaseInOperatingLeaseAssetsAndLiabilitiesUponDerecognition"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_AccountingPoliciesAbstract" xlink:label="us-gaap_AccountingPoliciesAbstract"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_DeferredRevenueByArrangementDisclosureTextBlock" xlink:label="us-gaap_DeferredRevenueByArrangementDisclosureTextBlock"/>
          <link:loc xlink:type="locator" xlink:href="atra-20260630.xsd#atra_RoyaltyEligibleToReceiveTermAfterFirstCommercialSale" xlink:label="atra_RoyaltyEligibleToReceiveTermAfterFirstCommercialSale"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ScheduleOfEarningsPerShareBasicByCommonClassTable" xlink:label="us-gaap_ScheduleOfEarningsPerShareBasicByCommonClassTable"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_LesseeOperatingLeaseLiabilityPaymentsDueYearFour" xlink:label="us-gaap_LesseeOperatingLeaseLiabilityPaymentsDueYearFour"/>
          <link:loc xlink:type="locator" xlink:href="atra-20260630.xsd#atra_IssuanceOfCommonStockNetOfCommissionsAndOfferingCostsShares" xlink:label="atra_IssuanceOfCommonStockNetOfCommissionsAndOfferingCostsShares"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ClassOfStockDomain" xlink:label="us-gaap_ClassOfStockDomain"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_CommercialPaperMember" xlink:label="us-gaap_CommercialPaperMember"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfSharesAvailableForGrant" xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfSharesAvailableForGrant"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognizedPeriodForRecognition1" xlink:label="us-gaap_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognizedPeriodForRecognition1"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_CashCashEquivalentsAndShortTermInvestments" xlink:label="us-gaap_CashCashEquivalentsAndShortTermInvestments"/>
          <link:loc xlink:type="locator" xlink:href="atra-20260630.xsd#atra_AdditionalTerritoryMember" xlink:label="atra_AdditionalTerritoryMember"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_ScheduleOfStockByClassTable" xlink:label="us-gaap_ScheduleOfStockByClassTable"/>
          <link:loc xlink:type="locator" xlink:href="atra-20260630.xsd#atra_Leaseagreementareaofofficelabandmanufacturingspace" xlink:label="atra_Leaseagreementareaofofficelabandmanufacturingspace"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.sec.gov/dei/2025/dei-2025.xsd#dei_EntityEmergingGrowthCompany" xlink:label="dei_EntityEmergingGrowthCompany"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsVestedAndExpectedToVestOutstandingWeightedAverageRemainingContractualTerm1" xlink:label="us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsVestedAndExpectedToVestOutstandingWeightedAverageRemainingContractualTerm1"/>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="atra_CommonStockCapitalAdditionalSharesReservedForFutureIssuance_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Common stock capital additional shares reserved for future issuance.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="atra_CommonStockCapitalAdditionalSharesReservedForFutureIssuance_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Common Stock Capital Additional Shares Reserved For Future Issuance</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="atra_CommonStockCapitalAdditionalSharesReservedForFutureIssuance_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Additional shares of common stock, reserved for issuance</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriodWeightedAverageGrantDateFairValue_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Share-Based Compensation Arrangement by Share-Based Payment Award, Equity Instruments Other than Options, Vested in Period, Weighted Average Grant Date Fair Value</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriodWeightedAverageGrantDateFairValue_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Weighted Average Grant Date Fair Value, Vested</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ProceedsFromSaleOfPropertyPlantAndEquipment_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Proceeds from sale of property and equipment</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ProceedsFromSaleOfPropertyPlantAndEquipment_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Proceeds from Sale of Property, Plant, and Equipment</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ProceedsFromSaleOfPropertyPlantAndEquipment_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel">Proceeds from Sale of Property, Plant, and Equipment, Total</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_RestructuringReserve_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel">Restructuring Reserve, Total</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_RestructuringReserve_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Restructuring Reserve</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_RestructuringReserve_lbl" xlink:role="http://www.xbrl.org/2003/role/periodEndLabel">Liability balance, ending balance</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_RestructuringReserve_lbl" xlink:role="http://www.xbrl.org/2003/role/periodStartLabel">Liability balance, beginning balance</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="atra_FinanceLeaseOtherLongTermLiabilities_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Finance Lease Other Long Term Liabilities</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="atra_FinanceLeaseOtherLongTermLiabilities_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Finance Lease Other Long Term Liabilities</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="atra_FinanceLeaseOtherLongTermLiabilities_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Finance Lease Other Long Term Liabilities</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_FinanceLeaseLiability_lbl" xlink:role="http://www.xbrl.org/2003/role/verboseLabel">Total</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_FinanceLeaseLiability_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Present value of lease liabilities</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_FinanceLeaseLiability_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Finance Lease, Liability</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_FinanceLeaseLiability_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel">Finance Lease, Liability, Total</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="dei_EntityIncorporationStateCountryCode_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Entity Incorporation, State or Country Code</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="dei_EntityIncorporationStateCountryCode_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Entity Incorporation, State or Country Code</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="dei_EntityIncorporationStateCountryCode_lbl" xlink:role="http://www.xbrl.org/2003/role/verboseLabel">Entity incorporation state</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_FinanceLeaseLiabilityPaymentsDueYearFour_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Finance Lease, Liability, to be Paid, Year Four</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_FinanceLeaseLiabilityPaymentsDueYearFour_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Finance leases, 2028</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="atra_ProcessingRoomsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Processing Rooms</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="atra_ProcessingRoomsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Processing Rooms [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="atra_ProcessingRoomsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Processing rooms member.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="atra_DirectRegisteredOfferingMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Direct Registered Offering [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="atra_DirectRegisteredOfferingMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Direct Registered Offering [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="atra_DirectRegisteredOfferingMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Direct Registered Offering</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_IncreaseDecreaseInAccountsPayable_lbl" xlink:role="http://www.xbrl.org/2009/role/negatedTerseLabel">Accounts payable</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_IncreaseDecreaseInAccountsPayable_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Increase (Decrease) in Accounts Payable</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_IncreaseDecreaseInAccountsPayable_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Accounts payable</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_IncreaseDecreaseInAccountsPayable_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel">Increase (Decrease) in Accounts Payable, Total</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_CashFlowNoncashInvestingAndFinancingActivitiesDisclosureAbstract_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Cash Flow, Noncash Investing and Financing Activities Disclosure [Abstract]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_CashFlowNoncashInvestingAndFinancingActivitiesDisclosureAbstract_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Non-cash financing activities</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_AvailableForSaleSecuritiesDebtMaturitiesWithinOneYearFairValue_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Debt Securities, Available-for-Sale, Fair Value, Maturity, Allocated and Single Maturity Date, Year One</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_AvailableForSaleSecuritiesDebtMaturitiesWithinOneYearFairValue_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Maturing within one year, Estimated fair value</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="atra_ContractualObligationsDueToLicensors_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Contractual obligations due to licensors.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="atra_ContractualObligationsDueToLicensors_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Contractual Obligations Due To Licensors</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="atra_ContractualObligationsDueToLicensors_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Contractual obligations due to Bayer, MSK and QIMR</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_PlanNameAxis_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Plan Name [Axis]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_PlanNameAxis_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Plan Name</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="atra_IncreaseDecreaseMilestonePayment_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Increase Decrease Milestone Payment</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="atra_IncreaseDecreaseMilestonePayment_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Increase Decrease Milestone Payment</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="atra_IncreaseDecreaseMilestonePayment_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Reduce Milestone Payment</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="dei_EntityCurrentReportingStatus_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Entity Current Reporting Status</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="dei_EntityCurrentReportingStatus_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Entity Current Reporting Status</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="atra_ReconciliationOfShareAmountUsedInComputingEarningsPerShareTableTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Reconciliation of Share Amount used in Computing Earnings Per Share [Table Text Block]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="atra_ReconciliationOfShareAmountUsedInComputingEarningsPerShareTableTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Reconciliation of share amount used in computing earnings per share.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="atra_ReconciliationOfShareAmountUsedInComputingEarningsPerShareTableTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Reconciliation of Computing of EPS</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="atra_FromDateOfGrantMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Expire from date of grant.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="atra_FromDateOfGrantMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">From Date Of Grant [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="atra_FromDateOfGrantMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">From Date Of Grant</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_OperatingExpensesAbstract_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Costs and operating expenses:</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_OperatingExpensesAbstract_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Operating Expenses [Abstract]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_FairValueInputsLevel2Member_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Level 2</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_FairValueInputsLevel2Member_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Fair Value, Inputs, Level 2 [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_CommitmentsAndContingenciesDisclosureTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Commitments and Contingencies Disclosure [Text Block]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_CommitmentsAndContingenciesDisclosureTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Commitments and Contingencies</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_CommonStockSharesAuthorized_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Common Stock, Shares Authorized</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_CommonStockSharesAuthorized_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Common stock, shares authorized</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="srt_ProductOrServiceAxis_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Product and Service [Axis]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="dei_DocumentFiscalPeriodFocus_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Document Fiscal Period Focus</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="dei_DocumentFiscalPeriodFocus_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Document Fiscal Period Focus</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_FinanceLeaseLiabilityPaymentsDue_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel">Finance leases, Total minimum payments</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_FinanceLeaseLiabilityPaymentsDue_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Finance Lease, Liability, to be Paid</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="dei_EntityShellCompany_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Entity Shell Company</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="dei_EntityShellCompany_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Entity Shell Company</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ContractualObligation_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Contractual obligations</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ContractualObligation_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Contractual Obligation</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ContractualObligation_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel">Contractual Obligation, Total</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_OtherAccruedLiabilitiesCurrent_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Other accrued liabilities</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_OtherAccruedLiabilitiesCurrent_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Other Accrued Liabilities, Current</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="atra_AllMilestonesMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">All Milestones [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="atra_AllMilestonesMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">All Milestones [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="atra_AllMilestonesMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">All Milestones [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="atra_May2020WarrantsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">May 2020 [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="atra_May2020WarrantsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">May 2020 Warrants [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ShortTermInvestmentsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Short-Term Investments [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ShortTermInvestmentsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Amounts Classified As Short-Term Investments</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_SegmentReportingPolicyPolicyTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Segment Reporting, Policy [Policy Text Block]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_SegmentReportingPolicyPolicyTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Segment and Geographic Information</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_CashAndCashEquivalentsAtCarryingValue_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Cash and Cash Equivalent</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_CashAndCashEquivalentsAtCarryingValue_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Cash and cash equivalents</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_CashAndCashEquivalentsAtCarryingValue_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel">Cash and Cash Equivalents, at Carrying Value, Total</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_CashAndCashEquivalentsAtCarryingValue_lbl" xlink:role="http://www.xbrl.org/2003/role/periodStartLabel">Cash and Cash Equivalents, at Carrying Value, Beginning Balance</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_CashAndCashEquivalentsAtCarryingValue_lbl" xlink:role="http://www.xbrl.org/2003/role/periodEndLabel">Cash and Cash Equivalents, at Carrying Value, Ending Balance</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_OperatingLeaseImpairmentLoss_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Operating Lease, Impairment Loss</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_OperatingLeaseImpairmentLoss_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Loss on impairment of lease right-of-use asset</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="atra_RegulatoryMilestone_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Regulatory Milestone</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="atra_RegulatoryMilestone_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Regulatory Milestone</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="atra_RegulatoryMilestone_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Regulatory Milestone</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="atra_RSUReleasesSharesDuringPeriod_lbl" xlink:role="http://www.xbrl.org/2003/role/label">RSU Releases Shares During Period</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="atra_RSUReleasesSharesDuringPeriod_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">RSU Releases Shares During Period</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="atra_RSUReleasesSharesDuringPeriod_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">RSU releases</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_CommonStockSharesIssued_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Common Stock, Shares, Issued</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_CommonStockSharesIssued_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Common stock, shares issued</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_CommonStockSharesIssued_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel">Common Stock, Shares, Issued, Total</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="atra_RecordedUnconditionalServiceObligationsTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Schedule of Minimum Commitments</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="atra_RecordedUnconditionalServiceObligationsTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Recorded unconditional service obligations.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="atra_RecordedUnconditionalServiceObligationsTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Recorded Unconditional Service Obligations [Text Block]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_StatementTable_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Statement [Table]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_StatementTable_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Statement [Table]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_RestrictedCashNoncurrent_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Restricted cash - long term</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_RestrictedCashNoncurrent_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Restricted Cash, Noncurrent</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_RightOfUseAssetObtainedInExchangeForOperatingLeaseLiability_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Operating lease assets obtained in exchange for lease obligations:</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_RightOfUseAssetObtainedInExchangeForOperatingLeaseLiability_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Right-of-Use Asset Obtained in Exchange for Operating Lease Liability</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="atra_ProceedsFromIssuanceOfCommonStockGross_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Proceeds from issuance of common stock gross.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="atra_ProceedsFromIssuanceOfCommonStockGross_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Proceeds From Issuance Of Common Stock Gross</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="atra_ProceedsFromIssuanceOfCommonStockGross_lbl" xlink:role="http://www.xbrl.org/2003/role/verboseLabel">Proceeds from sale of pre-funded warrants to purchase common stock, gross</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_InterestReceivable_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Interest Receivable</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_InterestReceivable_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Accrued interest receivable</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="atra_MedicalAndSafetyExpense_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Medical and Safety Expense</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="atra_MedicalAndSafetyExpense_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Medical and Safety Expense</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="atra_MedicalAndSafetyExpense_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Medical and safety expense</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_LongTermPurchaseCommitmentCategoryOfItemPurchasedDomain_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Long-Term Purchase Commitment, Category of Item Purchased [Domain]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="atra_CashPayment_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Cash Payment</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="atra_CashPayment_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Cash Payment</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="atra_CashPayment_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Cash Payment</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardPurchasePriceOfCommonStockPercent_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Share-Based Compensation Arrangement by Share-Based Payment Award, Purchase Price of Common Stock, Percent</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardPurchasePriceOfCommonStockPercent_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Percentage of employees purchase price of common stock</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="atra_TotalOtherIncomeExpenseNet_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel">Total other income (expense), net</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="atra_TotalOtherIncomeExpenseNet_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Total other income (expense), net</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="atra_TotalOtherIncomeExpenseNet_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Total other income (expense), net</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_StatementLineItems_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Statement [Line Items]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_StatementLineItems_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Statement [Line Items]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="atra_December2020WarrantsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">December 2020 Warrants [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="atra_December2020WarrantsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">December 2020 Warrants [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_WarrantMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Warrant [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_WarrantMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Warrant</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="dei_EntityFilerCategory_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Entity Filer Category</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="dei_EntityFilerCategory_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Entity Filer Category</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="atra_MaterialRightsTerm_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Material rights, term</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="atra_MaterialRightsTerm_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Material Rights, Term</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="atra_MaterialRightsTerm_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Material rights, term</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_LiabilitiesAndStockholdersEquity_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel">Total liabilities and stockholders' equity (deficit)</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_LiabilitiesAndStockholdersEquity_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Liabilities and Equity</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_IncreaseDecreaseInEmployeeRelatedLiabilities_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Increase (Decrease) in Employee Related Liabilities</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_IncreaseDecreaseInEmployeeRelatedLiabilities_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Accrued compensation</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_IncreaseDecreaseInEmployeeRelatedLiabilities_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel">Increase (Decrease) in Employee Related Liabilities, Total</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_IncreaseDecreaseInEmployeeRelatedLiabilities_lbl" xlink:role="http://www.xbrl.org/2009/role/negatedLabel">Accounts compensation</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsExercisableWeightedAverageExercisePrice_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Share-Based Compensation Arrangement by Share-Based Payment Award, Options, Exercisable, Weighted Average Exercise Price</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsExercisableWeightedAverageExercisePrice_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Exercisable, Weighted Average Exercise Price</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_RestructuringCostAndReserveAxis_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Restructuring Type [Axis]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_PropertyPlantAndEquipmentByTypeAxis_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Long-Lived Tangible Asset [Axis]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_PropertyPlantAndEquipmentByTypeAxis_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Long-Lived Tangible Asset</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_SeveranceCosts1_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Severance Costs</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_SeveranceCosts1_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Severance Costs</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_FinanceLeaseLiabilityPaymentsDueYearThree_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Finance Lease, Liability, to be Paid, Year Three</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_FinanceLeaseLiabilityPaymentsDueYearThree_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Finance leases, 2027</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="atra_BayerManufacturingAgreementMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Bayer Manufacturing Agreement.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="atra_BayerManufacturingAgreementMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Bayer Manufacturing Agreement [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="atra_BayerManufacturingAgreementMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Bayer Manufacturing Agreement</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_FinancialInstrumentsDisclosureTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Financial Instruments</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_FinancialInstrumentsDisclosureTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Financial Instruments Disclosure [Text Block]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ScheduleOfRestructuringAndRelatedCostsTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Summarizes of future termination benefit payments</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ScheduleOfRestructuringAndRelatedCostsTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Restructuring and Related Costs [Table Text Block]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_LiabilityForFuturePolicyBenefitAfterReinsuranceAbstract_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Liability for Future Policy Benefit, after Reinsurance [Abstract]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_SharesIssuedPricePerShare_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Shares Issued, Price Per Share</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_SharesIssuedPricePerShare_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Shares Issued, Price per Share</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_SubsequentEventLineItems_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Subsequent Event [Line Items]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_FinanceLeaseLiabilityCurrentStatementOfFinancialPositionExtensibleList_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Finance Lease, Liability, Current, Statement of Financial Position [Extensible Enumeration]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="atra_Scheduleofmaturitiesofleaseliabilitiesunderoperatingandfinanceleasestabletextblock_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Schedule of Maturities of Lease Liabilities Under Operating and Finance Leases</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="atra_Scheduleofmaturitiesofleaseliabilitiesunderoperatingandfinanceleasestabletextblock_lbl" xlink:role="http://www.xbrl.org/2003/role/label">ScheduleOfMaturitiesOfLeaseLiabilitiesUnderOperatingAndFinanceLeasesTableTextBlock</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="atra_Scheduleofmaturitiesofleaseliabilitiesunderoperatingandfinanceleasestabletextblock_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">ScheduleOfMaturitiesOfLeaseLiabilitiesUnderOperatingAndFinanceLeasesTableTextBlock</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="srt_SegmentGeographicalDomain_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Geographical [Domain]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_AssetBackedSecuritiesMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Asset-Backed Securities [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_AssetBackedSecuritiesMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Asset-Backed Securities</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="atra_OfficeSpaceMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Office Space</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="atra_OfficeSpaceMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Office Space [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="atra_OfficeSpaceMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Office Space member.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ScheduleOfInventoryCurrentTableTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Schedule of Inventories</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ScheduleOfInventoryCurrentTableTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Schedule of Inventory, Current [Table Text Block]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="atra_LeaseAgreementAreaOfOfficeLabAndWarehouseSpace_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Lease agreement area of office lab and warehouse space.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="atra_LeaseAgreementAreaOfOfficeLabAndWarehouseSpace_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Lease Agreement Area Of Office Lab And Warehouse Space</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="atra_LeaseAgreementAreaOfOfficeLabAndWarehouseSpace_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Lease agreement area of square feet of office, lab and warehouse space</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_AdditionalPaidInCapitalCommonStock_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Additional Paid in Capital, Common Stock</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_AdditionalPaidInCapitalCommonStock_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Additional paid-in capital</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_AdditionalPaidInCapitalCommonStock_lbl" xlink:role="http://www.xbrl.org/2003/role/periodStartLabel">Additional Paid in Capital, Common Stock, Beginning Balance</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_AdditionalPaidInCapitalCommonStock_lbl" xlink:role="http://www.xbrl.org/2003/role/periodEndLabel">Additional Paid in Capital, Common Stock, Ending Balance</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_SignificantAccountingPoliciesTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Significant Accounting Policies [Text Block]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_SignificantAccountingPoliciesTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Summary of Significant Accounting Policies</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_PropertyPlantAndEquipmentLineItems_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Property, Plant and Equipment [Line Items]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_PropertyPlantAndEquipmentLineItems_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Property Plant And Equipment [Line Items]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardTermsOfAward_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Share-Based Compensation Arrangement by Share-Based Payment Award, Terms of Award</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardTermsOfAward_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Stock option granted description terms</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_LiabilityForFuturePolicyBenefitsAndUnpaidClaimsDisclosureTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Liability Related to the Sale of Future Revenues</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_LiabilityForFuturePolicyBenefitsAndUnpaidClaimsDisclosureTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Liability for Future Policy Benefits and Unpaid Claims Disclosure [Text Block]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriodGross_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Share-Based Compensation Arrangement by Share-Based Payment Award, Options, Grants in Period, Gross</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriodGross_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Granted, Shares</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ProceedsFromSaleOfOtherAssets1_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Proceeds from Sale of Other Assets</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ProceedsFromSaleOfOtherAssets1_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Payment Received form Sale of Assets</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="atra_ProceedsFromSaleOfFutureRoyaltiesGross_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Proceeds from sale of future royalties, gross</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="atra_ProceedsFromSaleOfFutureRoyaltiesGross_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Proceeds from sale of future royalties, gross</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="atra_ProceedsFromSaleOfFutureRoyaltiesGross_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Proceeds from sale of future royalties, gross</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_InvestmentsClassifiedByContractualMaturityDateTableTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Investments Classified by Contractual Maturity Date [Table Text Block]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_InvestmentsClassifiedByContractualMaturityDateTableTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Amortized Cost and Fair Value of Available for Sale Securities by Contractual Maturity</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_EarningsPerShareBasic_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Earnings Per Share, Basic</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_EarningsPerShareBasic_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel">Earnings Per Share, Basic, Total</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_EarningsPerShareBasic_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Basic (loss) earnings per common share</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="atra_TwoThousandNineteenWarrantsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Two thousand nineteen warrants.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="atra_TwoThousandNineteenWarrantsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Two Thousand Nineteen Warrants [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="atra_TwoThousandNineteenWarrantsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">2019 Warrants</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="atra_MilestoneTypeAxis_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Milestone Type [Axis]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="atra_MilestoneTypeAxis_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Milestone Type [Axis]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingNumber_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Share-Based Compensation Arrangement by Share-Based Payment Award, Options, Outstanding, Number</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingNumber_lbl" xlink:role="http://www.xbrl.org/2003/role/periodEndLabel">Outstanding, Shares, ending balance</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingNumber_lbl" xlink:role="http://www.xbrl.org/2003/role/periodStartLabel">Outstanding, Shares, beginning balance</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_LiabilitiesCurrent_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Liabilities, Current</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_LiabilitiesCurrent_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel">Total current liabilities</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_IncreaseDecreaseInAccountsReceivable_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Accounts receivable</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_IncreaseDecreaseInAccountsReceivable_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Increase (Decrease) in Accounts Receivable</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_IncreaseDecreaseInAccountsReceivable_lbl" xlink:role="http://www.xbrl.org/2009/role/negatedLabel">Accounts receivable</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_AdjustmentsToReconcileNetIncomeLossToCashProvidedByUsedInOperatingActivitiesAbstract_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Adjustments to reconcile net income (loss) to net cash used in operating activities:</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_AdjustmentsToReconcileNetIncomeLossToCashProvidedByUsedInOperatingActivitiesAbstract_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Adjustment to Reconcile Net Income to Cash Provided by (Used in) Operating Activity [Abstract]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_LesseeOperatingLeaseLiabilityPaymentsDueYearFive_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Lessee, Operating Lease, Liability, to be Paid, Year Five</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_LesseeOperatingLeaseLiabilityPaymentsDueYearFive_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Operating leases, 2030</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="atra_CashEquivalentsAmortizedCost_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Cash equivalents, amortized cost.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="atra_CashEquivalentsAmortizedCost_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Cash Equivalents Amortized Cost</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="atra_CashEquivalentsAmortizedCost_lbl" xlink:role="http://www.xbrl.org/2009/role/negatedTotalLabel">Total Amortized Cost</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="atra_CashEquivalentsAmortizedCost_lbl" xlink:role="http://www.xbrl.org/2009/role/negatedLabel">Total Amortized Cost</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_AvailableForSaleSecuritiesDebtMaturitiesFairValueAbstract_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Debt Securities, Available-for-Sale, Fair Value, Fiscal Year Maturity [Abstract]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_AvailableForSaleSecuritiesDebtMaturitiesFairValueAbstract_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Estimated Fair value</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="atra_Weightedaverageremainingleasetermabstract_lbl" xlink:role="http://www.xbrl.org/2003/role/label">WeightedAverageRemainingLeaseTermAbstract</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="atra_Weightedaverageremainingleasetermabstract_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">WeightedAverageRemainingLeaseTermAbstract</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="atra_Weightedaverageremainingleasetermabstract_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Weighted Average Remaining Lease Term</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="atra_Non-CashImpairmentOfLeaseRight-Of-UseAsset_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Non-Cash Impairment of Lease Right-of-Use Asset</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="atra_Non-CashImpairmentOfLeaseRight-Of-UseAsset_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Non-Cash Impairment of Lease Right-of-Use Asset</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="atra_Non-CashImpairmentOfLeaseRight-Of-UseAsset_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Non-cash impairment of the right-of-use asset</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_StockholdersEquityAbstract_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Stockholders' equity (deficit):</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_StockholdersEquityAbstract_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Equity, Attributable to Parent [Abstract]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="dei_EntitySmallBusiness_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Entity Small Business</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="dei_EntitySmallBusiness_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Entity Small Business</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_RetainedEarningsAccumulatedDeficit_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Retained Earnings (Accumulated Deficit)</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_RetainedEarningsAccumulatedDeficit_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Accumulated deficit</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_RetainedEarningsAccumulatedDeficit_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel">Retained Earnings (Accumulated Deficit), Total</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_RetainedEarningsAccumulatedDeficit_lbl" xlink:role="http://www.xbrl.org/2003/role/periodStartLabel">Retained Earnings (Accumulated Deficit), Beginning Balance</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_RetainedEarningsAccumulatedDeficit_lbl" xlink:role="http://www.xbrl.org/2003/role/periodEndLabel">Retained Earnings (Accumulated Deficit), Ending Balance</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_AccretionExpense_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Accretion of liability related to sale of future revenues</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_AccretionExpense_lbl" xlink:role="http://www.xbrl.org/2003/role/verboseLabel">Accretion of interest expense on liability related to sale of future revenues</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_AccretionExpense_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Accretion Expense</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_RestrictedStockValueSharesIssuedNetOfTaxWithholdings_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Restricted Stock, Value, Shares Issued Net of Tax Withholdings</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_RestrictedStockValueSharesIssuedNetOfTaxWithholdings_lbl" xlink:role="http://www.xbrl.org/2009/role/negatedLabel">RSU settlements, net of shares withheld</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="atra_Less_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Less:</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="atra_Less_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Less</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsForfeituresInPeriod_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Share-Based Compensation Arrangement by Share-Based Payment Award, Options, Forfeitures in Period</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsForfeituresInPeriod_lbl" xlink:role="http://www.xbrl.org/2009/role/negatedLabel">Forfeited or expired, Shares</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="atra_ClassOfWarrantOrRightNumberOfWarrantsIssued_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Class of warrant or right number of warrants issued.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="atra_ClassOfWarrantOrRightNumberOfWarrantsIssued_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Class Of Warrant Or Right Number Of Warrants Issued</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="atra_ClassOfWarrantOrRightNumberOfWarrantsIssued_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Number of warrants issued</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_PaymentsToAcquireShortTermInvestments_lbl" xlink:role="http://www.xbrl.org/2009/role/negatedLabel">Purchases of short-term investments</link:label>
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          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_PaymentsToAcquireShortTermInvestments_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Purchases of short-term investments</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="atra_IssuanceOfCommonStockPursuantToEmployeeStockAwardsValue_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Issuance of common stock pursuant to employee stock awards value.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="atra_IssuanceOfCommonStockPursuantToEmployeeStockAwardsValue_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Issuance Of Common Stock Pursuant To Employee Stock Awards Value</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="atra_IssuanceOfCommonStockPursuantToEmployeeStockAwardsValue_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Issuance of common stock pursuant to employee stock awards</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="atra_Financeleasecost_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">FinanceLeaseCost</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="atra_Financeleasecost_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel">Total finance lease cost</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="atra_Financeleasecost_lbl" xlink:role="http://www.xbrl.org/2003/role/label">FinanceLeaseCost</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_LeasesAbstract_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Leases [Abstract]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ContractWithCustomerLiability_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Contract with Customer, Liability</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ContractWithCustomerLiability_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Deferred revenue</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ContractWithCustomerLiability_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel">Contract with Customer, Liability, Total</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ContractWithCustomerLiability_lbl" xlink:role="http://www.xbrl.org/2003/role/periodStartLabel">Deferred revenue, January 1, 2026</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ContractWithCustomerLiability_lbl" xlink:role="http://www.xbrl.org/2003/role/periodEndLabel">Deferred revenue June 30, 2026</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_LesseeLeaseDescriptionLineItems_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Lessee, Lease, Description [Line Items]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="dei_AmendmentFlag_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Amendment Flag</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="dei_AmendmentFlag_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Amendment Flag</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="atra_OperatingLeaseRight-Of-UseAssetAcceleratedAmortizationExpense_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Operating Lease Right-of-Use Asset, Accelerated Amortization Expense</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="atra_OperatingLeaseRight-Of-UseAssetAcceleratedAmortizationExpense_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Operating Lease Right-of-Use Asset, Accelerated Amortization Expense</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="atra_OperatingLeaseRight-Of-UseAssetAcceleratedAmortizationExpense_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Accelerated amortization expense on right-of-use asset</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="srt_ProductsAndServicesDomain_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Product and Service [Domain]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_LossContingenciesLineItems_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Loss Contingencies [Line Items]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_LossContingenciesLineItems_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Loss Contingencies [Line Items]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="atra_CashEquivalentsAccumulatedGrossUnrealizedGainBeforeTax_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Cash equivalents, accumulated gross unrealized gain, before tax.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="atra_CashEquivalentsAccumulatedGrossUnrealizedGainBeforeTax_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Cash Equivalents Accumulated Gross Unrealized Gain Before Tax</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="atra_CashEquivalentsAccumulatedGrossUnrealizedGainBeforeTax_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Total Unrealized Gain</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="atra_EmployeesCount_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Employees Count</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="atra_EmployeesCount_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Employees Count</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="atra_SupplyAgreementMaximumExtensionTerm_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Supply agreement maximum extension term.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="atra_SupplyAgreementMaximumExtensionTerm_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Supply Agreement Maximum Extension Term</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="atra_SupplyAgreementMaximumExtensionTerm_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Supply agreement maximum extension term</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="atra_BusinessDescriptionTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">The entire disclosure for the business description concept. Business description describes the nature and type of organization including but not limited to organizational structure as may be applicable to holding companies, parent and subsidiary relationships, business divisions, business units, business segments, affiliates and information about significant ownership of the reporting entity.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="atra_BusinessDescriptionTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Business Description [Text Block]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="atra_BusinessDescriptionTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Description of Business</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ClassOfWarrantOrRightNumberOfSecuritiesCalledByWarrantsOrRights_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Warrants issued to purchase common stock</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ClassOfWarrantOrRightNumberOfSecuritiesCalledByWarrantsOrRights_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Class of Warrant or Right, Number of Securities Called by Warrants or Rights</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_FinanceLeaseInterestExpense_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Interest on lease liabilities</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_FinanceLeaseInterestExpense_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Finance Lease, Interest Expense</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="atra_ProceedsFromTransactionCost_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Proceeds from transaction cost</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="atra_ProceedsFromTransactionCost_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Proceeds from transaction cost</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_LiabilitiesAndStockholdersEquityAbstract_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Liabilities and stockholders' equity (deficit)</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_LiabilitiesAndStockholdersEquityAbstract_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Liabilities and Equity [Abstract]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="dei_EntityAddressPostalZipCode_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Entity Address, Postal Zip Code</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="dei_EntityAddressPostalZipCode_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Entity Address, Postal Zip Code</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_NetCashProvidedByUsedInOperatingActivities_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Cash Provided by (Used in) Operating Activity, Including Discontinued Operation</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_NetCashProvidedByUsedInOperatingActivities_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel">Net cash used in operating activities</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_CommonStockMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Common Stock [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_CommonStockMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Common Stock</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="atra_ClassOfWarrantOrRightTerm_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Class of warrant or right, term.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="atra_ClassOfWarrantOrRightTerm_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Class Of Warrant Or Right Term</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="atra_ClassOfWarrantOrRightTerm_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Warrants, term</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="atra_May2025Pre-FundedWarrantsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">May 2025 Pre-funded Warrants [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="atra_May2025Pre-FundedWarrantsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">May 2025 Pre-funded Warrants [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardOptionsGrantsInPeriodWeightedAverageExercisePrice_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Share-Based Compensation Arrangements by Share-Based Payment Award, Options, Grants in Period, Weighted Average Exercise Price</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardOptionsGrantsInPeriodWeightedAverageExercisePrice_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Granted, Weighted Average Exercise Price</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_LesseeOperatingLeaseLiabilityPaymentsDueYearThree_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Lessee, Operating Lease, Liability, to be Paid, Year Three</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_LesseeOperatingLeaseLiabilityPaymentsDueYearThree_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Operating leases, 2028</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_AccumulatedDepreciationDepletionAndAmortizationPropertyPlantAndEquipment_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Accumulated Depreciation, Depletion and Amortization, Property, Plant, and Equipment</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_AccumulatedDepreciationDepletionAndAmortizationPropertyPlantAndEquipment_lbl" xlink:role="http://www.xbrl.org/2009/role/negatedLabel">Less: accumulated depreciation and amortization</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_AccumulatedDepreciationDepletionAndAmortizationPropertyPlantAndEquipment_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel">Accumulated Depreciation, Depletion and Amortization, Property, Plant, and Equipment, Total</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_AccumulatedDepreciationDepletionAndAmortizationPropertyPlantAndEquipment_lbl" xlink:role="http://www.xbrl.org/2003/role/periodStartLabel">Accumulated Depreciation, Depletion and Amortization, Property, Plant, and Equipment, Beginning Balance</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_AccumulatedDepreciationDepletionAndAmortizationPropertyPlantAndEquipment_lbl" xlink:role="http://www.xbrl.org/2003/role/periodEndLabel">Accumulated Depreciation, Depletion and Amortization, Property, Plant, and Equipment, Ending Balance</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_OtherOperatingIncomeExpenseNet_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Other Operating Income (Expense), Net</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_OtherOperatingIncomeExpenseNet_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Other segment items</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ScheduleOfAvailableForSaleSecuritiesLineItems_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Debt Securities, Available-for-Sale [Line Items]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ScheduleOfAvailableForSaleSecuritiesLineItems_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Schedule of Available-for-sale Securities [Line Items]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="atra_JanuaryTwentyThousandTwentyFiveReductionMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">January Twenty Thousand Twenty Five Reduction [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="atra_JanuaryTwentyThousandTwentyFiveReductionMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">January Twenty Thousand Twenty Five Reduction [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="atra_JanuaryTwentyThousandTwentyFiveReductionMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">January 2025</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="atra_PaymentExchangeReductionAmount_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Payment exchange reduction amount</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="atra_PaymentExchangeReductionAmount_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Payment exchange reduction Amount</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="atra_PaymentExchangeReductionAmount_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Payment exchange reduction Amount</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="dei_EntityAddressAddressLine1_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Entity Address, Address Line One</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="dei_EntityAddressAddressLine1_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Entity Address, Address Line One</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_FairValueByFairValueHierarchyLevelAxis_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Fair Value Hierarchy and NAV [Axis]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_EarningsPerShareAbstract_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Net earnings (loss) per common share:</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_EarningsPerShareAbstract_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Earnings Per Share [Abstract]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_AvailableForSaleSecuritiesDebtMaturitiesSingleMaturityDateAmortizedCostBasis_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Debt Securities, Available-for-Sale, Maturity, Allocated and Single Maturity Date, Amortized Cost</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_AvailableForSaleSecuritiesDebtMaturitiesSingleMaturityDateAmortizedCostBasis_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel">Total available-for-sale securities, Amortized cost</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_SupplementalCashFlowInformationAbstract_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Supplemental Cash Flow Information [Abstract]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_SupplementalCashFlowInformationAbstract_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Supplemental cash flow disclosure</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="atra_CostsIncurredRelatedtoPerformanceObligationsIncludedinRD_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Costs Incurred Relatedto Performance Obligations Includedin R&amp;D</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="atra_CostsIncurredRelatedtoPerformanceObligationsIncludedinRD_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Costs Incurred Relatedto Performance Obligations Includedin R&amp;D</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="atra_CostsIncurredRelatedtoPerformanceObligationsIncludedinRD_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Costs Incurred Relatedto Performance Obligations Includedin R&amp;D</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="atra_NonCashOperatingLeaseExpense_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Non cash operating lease expense.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="atra_NonCashOperatingLeaseExpense_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Non Cash Operating Lease Expense</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="atra_NonCashOperatingLeaseExpense_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Non-cash operating lease expense</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_OperatingLeaseRightOfUseAsset_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Operating Lease, Right-of-Use Asset</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_OperatingLeaseRightOfUseAsset_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Operating lease assets</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_FinanceLeaseLiabilityUndiscountedExcessAmount_lbl" xlink:role="http://www.xbrl.org/2009/role/negatedLabel">Less: amount representing interest</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_FinanceLeaseLiabilityUndiscountedExcessAmount_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Less: amount representing interest</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_FinanceLeaseLiabilityUndiscountedExcessAmount_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Finance Lease, Liability, Undiscounted Excess Amount</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_GainLossOnSaleOfInvestments_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel">Gain on sale of ATOM Facility</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_GainLossOnSaleOfInvestments_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Gain on sale of ATOM Facility</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_GainLossOnSaleOfInvestments_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Gain (Loss) on Sale of Investments</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_IncreaseDecreaseInOtherOperatingAssetsAndLiabilitiesNetAbstract_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Increase (Decrease) in Other Operating Assets and Liabilities, Net [Abstract]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_IncreaseDecreaseInOtherOperatingAssetsAndLiabilitiesNetAbstract_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Changes in operating assets and liabilities:</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ClassOfWarrantOrRightAxis_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Class of Warrant or Right [Axis]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ClassOfWarrantOrRightAxis_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Class of Warrant or Right</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="dei_DocumentType_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Document Type</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="dei_DocumentType_lbl" xlink:role="http://www.xbrl.org/2003/role/verboseLabel">Document Type</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="atra_AtTheMarketOfferingMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">At the market offering.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="atra_AtTheMarketOfferingMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">At The Market Offering [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="atra_AtTheMarketOfferingMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">At The Market Offering</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_IncomeTaxesPaidNet_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Income Taxes Paid, Net</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_IncomeTaxesPaidNet_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel">Income Taxes Paid, Net, Total</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_IncomeTaxesPaidNet_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Cash paid for income taxes</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_TypeOfArrangementAxis_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Collaborative Arrangement and Arrangement Other than Collaborative [Axis]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_TypeOfArrangementAxis_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Collaborative Arrangement and Arrangement Other than Collaborative</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="atra_DecreaseIncreaseInFinanceLeaseAssetsAndLiabilitiesUponDerecognition_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Decrease Increase in Finance Lease Assets and Liabilities Upon Derecognition</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="atra_DecreaseIncreaseInFinanceLeaseAssetsAndLiabilitiesUponDerecognition_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Decrease Increase in Finance Lease Assets and Liabilities Upon Derecognition</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="atra_DecreaseIncreaseInFinanceLeaseAssetsAndLiabilitiesUponDerecognition_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Decrease in finance lease liabilities upon derecognition</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ArrangementsAndNonarrangementTransactionsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Collaborative Arrangement and Arrangement Other than Collaborative [Domain]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ArrangementsAndNonarrangementTransactionsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Collaborative Arrangement and Arrangement Other than Collaborative</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="dei_EntityCentralIndexKey_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Entity Central Index Key</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="dei_EntityCentralIndexKey_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Entity Central Index Key</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalentsPeriodIncreaseDecreaseExcludingExchangeRateEffect_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel">Increase (decrease) in cash, cash equivalents and restricted cash</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalentsPeriodIncreaseDecreaseExcludingExchangeRateEffect_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Cash, Cash Equivalent, Restricted Cash, and Restricted Cash Equivalent, Period Increase (Decrease), Excluding Exchange Rate Effect, Including Discontinued Operation</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_SubsequentEventTypeDomain_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Subsequent Event Type [Domain]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="atra_PlatformSciencesDevelopmentAndOperationsExpense_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Platform Sciences Development and Operations Expense</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="atra_PlatformSciencesDevelopmentAndOperationsExpense_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Platform Sciences Development and Operations Expense</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="atra_PlatformSciencesDevelopmentAndOperationsExpense_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Technical operations and quality expense</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_InterestIncomeOperating_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Interest income</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_InterestIncomeOperating_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Interest Income, Operating</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_InterestIncomeOperating_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel">Interest Income, Operating, Total</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="atra_IncreaseDecreaseInAccruedResearchAndDevelopment_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Increase (decrease) in accrued research and development.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="atra_IncreaseDecreaseInAccruedResearchAndDevelopment_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Increase Decrease In Accrued Research And Development</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="atra_IncreaseDecreaseInAccruedResearchAndDevelopment_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Accrued research and development expenses</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="atra_IncreaseDecreaseInAccruedResearchAndDevelopment_lbl" xlink:role="http://www.xbrl.org/2009/role/negatedLabel">Accrued research and development expenses</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareAmount_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Antidilutive Securities Excluded from Computation of Earnings Per Share, Amount</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareAmount_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Antidilutive securities excluded from computation of earnings per share</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="atra_ReceivedTieredRoyaltiesOnNetSales_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Received tiered royalties on net sales, percentage</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="atra_ReceivedTieredRoyaltiesOnNetSales_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Received Tiered Royalties On Net Sales</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="atra_ReceivedTieredRoyaltiesOnNetSales_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Received Tiered Royalties On Net Sales</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="atra_SupplementalBalanceSheetInformationTable_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Supplemental Balance Sheet Information [Table]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="atra_SupplementalBalanceSheetInformationTable_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Supplemental Balance Sheet Information [Table]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_CommonStockParOrStatedValuePerShare_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Common Stock, Par or Stated Value Per Share</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_CommonStockParOrStatedValuePerShare_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Common stock, par value</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_CommonStockParOrStatedValuePerShare_lbl" xlink:role="http://www.xbrl.org/2003/role/verboseLabel">Common stock exercise price</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_OperatingLeaseRightOfUseAssetAmortizationExpense_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Operating Lease, Right-of-Use Asset, Periodic Reduction</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_OperatingLeaseRightOfUseAssetAmortizationExpense_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Amortization expense on right-of-use asset</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsOutstandingWeightedAverageRemainingContractualTerm2_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Share-Based Compensation Arrangement by Share-Based Payment Award, Options, Outstanding, Weighted Average Remaining Contractual Term</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsOutstandingWeightedAverageRemainingContractualTerm2_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Outstanding, Weighted Average Remaining Contractual Term</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_AvailableForSaleDebtSecuritiesAmortizedCostBasis_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Debt Securities, Available-for-Sale, Amortized Cost</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_AvailableForSaleDebtSecuritiesAmortizedCostBasis_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel">Total Amortized Cost</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_AvailableForSaleDebtSecuritiesAmortizedCostBasis_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Total Amortized Cost</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_AvailableForSaleSecuritiesDebtSecurities_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Debt Securities, Available-for-Sale</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_AvailableForSaleSecuritiesDebtSecurities_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Total Fair Value</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_AvailableForSaleSecuritiesDebtSecurities_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel">Total Fair Value</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_GainLossOnTerminationOfLease_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Gain (Loss) on Termination of Lease</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_GainLossOnTerminationOfLease_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Gain on derecognition of lease liabilities</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_GainLossOnTerminationOfLease_lbl" xlink:role="http://www.xbrl.org/2009/role/negatedLabel">Gain on derecognition of lease liabilities</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_StockIssuedDuringPeriodSharesStockOptionsExercised_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Share-Based Compensation Arrangement by Share-Based Payment Award, Options, Exercises in Period</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_StockIssuedDuringPeriodSharesStockOptionsExercised_lbl" xlink:role="http://www.xbrl.org/2009/role/negatedLabel">Exercised, Shares</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_AccruedLiabilitiesCurrent_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Accrued operating expenses</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_AccruedLiabilitiesCurrent_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Accrued Liabilities, Current</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_AccruedLiabilitiesCurrent_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel">Accrued Liabilities, Current, Total</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_EmployeeServiceShareBasedCompensationAllocationOfRecognizedPeriodCostsLineItems_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Share-Based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_EmployeeServiceShareBasedCompensationAllocationOfRecognizedPeriodCostsLineItems_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Employee Service Share Based Compensation Allocation Of Recognized Period Costs [Line Items]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="dei_CurrentFiscalYearEndDate_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Current Fiscal Year End Date</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="dei_CurrentFiscalYearEndDate_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Current Fiscal Year End Date</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_RestrictedCashAndCashEquivalentsNoncurrent_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Letter of credit issued, classified as long-term restricted cash</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_RestrictedCashAndCashEquivalentsNoncurrent_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Restricted Cash and Cash Equivalent, Noncurrent</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_RestrictedCashAndCashEquivalentsNoncurrent_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel">Restricted Cash and Cash Equivalents, Noncurrent, Total</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="dei_DocumentQuarterlyReport_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Document Quarterly Report</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="dei_DocumentQuarterlyReport_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Document Quarterly Report</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="atra_HCRxRoyaltiesMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">HCRx Royalties [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="atra_HCRxRoyaltiesMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">HCRx Royalties [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="dei_EntityAddressStateOrProvince_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Entity Address, State or Province</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="dei_EntityAddressStateOrProvince_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Entity Address, State or Province</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_InvestmentIncomeNetAmortizationOfDiscountAndPremium_lbl" xlink:role="http://www.xbrl.org/2009/role/negatedLabel">Amortization (accretion) of investment premiums (discounts)</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_InvestmentIncomeNetAmortizationOfDiscountAndPremium_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Investment Income, Net, Amortization of Discount and Premium</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_InvestmentIncomeNetAmortizationOfDiscountAndPremium_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel">Investment Income, Net, Amortization of Discount and Premium, Total</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedNumber_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Share-Based Compensation Arrangement by Share-Based Payment Award, Equity Instruments Other than Options, Nonvested, Number</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedNumber_lbl" xlink:role="http://www.xbrl.org/2003/role/periodStartLabel">Balance as of December 31, 2025</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedNumber_lbl" xlink:role="http://www.xbrl.org/2003/role/periodEndLabel">Balance as of June 30, 2026</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="atra_LiabilityRelatedToTheSaleOfFutureRoyalties_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Liability Related To The Sale Of Future Royalties</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="atra_LiabilityRelatedToTheSaleOfFutureRoyalties_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Liability Related To The Sale Of Future Royalties</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="atra_LiabilityRelatedToTheSaleOfFutureRoyalties_lbl" xlink:role="http://www.xbrl.org/2003/role/periodStartLabel">Liability related to sale of future revenues as of January 1, 2026</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="atra_LiabilityRelatedToTheSaleOfFutureRoyalties_lbl" xlink:role="http://www.xbrl.org/2003/role/periodEndLabel">Liability related to the sale of future revenues as of June 30, 2026</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="atra_EquityWarrantsAsACharge_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Equity Warrants As A Charge</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="atra_EquityWarrantsAsACharge_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Equity Warrants As A Charge</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_PreferredStockSharesOutstanding_lbl" xlink:role="http://www.xbrl.org/2003/role/periodEndLabel">Preferred Stock, Shares Outstanding, Ending Balance</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_PreferredStockSharesOutstanding_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Preferred Stock, Shares Outstanding</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_PreferredStockSharesOutstanding_lbl" xlink:role="http://www.xbrl.org/2003/role/verboseLabel">Preferred stock, shares outstanding</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_PreferredStockSharesOutstanding_lbl" xlink:role="http://www.xbrl.org/2003/role/periodStartLabel">Preferred Stock, Shares Outstanding, Beginning Balance</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ComprehensiveIncomeNetOfTax_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel">Comprehensive income (loss)</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ComprehensiveIncomeNetOfTax_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Comprehensive Income (Loss), Net of Tax, Attributable to Parent</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_AvailableForSaleDebtSecuritiesAccumulatedGrossUnrealizedGainBeforeTax_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Debt Securities, Available-for-Sale, Accumulated Gross Unrealized Gain, before Tax</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_AvailableForSaleDebtSecuritiesAccumulatedGrossUnrealizedGainBeforeTax_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Total Unrealized Gain</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_CommonStockCapitalSharesReservedForFutureIssuance_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Common Stock, Capital Shares Reserved for Future Issuance</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_CommonStockCapitalSharesReservedForFutureIssuance_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Total reserved shares of common stock</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_CommonStockCapitalSharesReservedForFutureIssuance_lbl" xlink:role="http://www.xbrl.org/2003/role/verboseLabel">Shares of common stock, reserved for issuance</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DisposalGroupsIncludingDiscontinuedOperationsDisclosureTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Sale of ATOM Facility</link:label>
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          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ClassOfWarrantOrRightDomain_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Class of Warrant or Right [Domain]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ClassOfWarrantOrRightDomain_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Class of Warrant or Right</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="srt_StatementGeographicalAxis_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Geographical [Axis]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="atra_Weightedaveragediscountrateabstract_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Weighted Average Discount Rate</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="atra_Weightedaveragediscountrateabstract_lbl" xlink:role="http://www.xbrl.org/2003/role/label">WeightedAverageDiscountRateAbstract</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="atra_Weightedaveragediscountrateabstract_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">WeightedAverageDiscountRateAbstract</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="atra_NonCashInvestingAndFinancingActivitiesAccruedCostsRelatedToDirectRegisteredOffering_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Non-cash Investing and Financing Activities Accrued Costs Related to Direct Registered Offering</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="atra_NonCashInvestingAndFinancingActivitiesAccruedCostsRelatedToDirectRegisteredOffering_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Non-cash Investing and Financing Activities Accrued Costs Related to Direct Registered Offering.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="atra_NonCashInvestingAndFinancingActivitiesAccruedCostsRelatedToDirectRegisteredOffering_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Accrued costs related to underwritten registered direct offering</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="atra_LiabilityRelatedToTheSaleOfFutureRoyaltiesLongTerm_lbl" xlink:role="http://www.xbrl.org/2003/role/verboseLabel">Liability related to sale of future revenues - long-term</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="atra_LiabilityRelatedToTheSaleOfFutureRoyaltiesLongTerm_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Liability related to the sale of future revenues - long-term</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="atra_LiabilityRelatedToTheSaleOfFutureRoyaltiesLongTerm_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Liability related to the sale of future royalties - long-term</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="atra_LiabilityRelatedToTheSaleOfFutureRoyaltiesLongTerm_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Liability related to the sale of future royalties - long-term</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="atra_LiabilityRelatedToTheSaleOfFutureRoyaltiesLongTerm_lbl" xlink:role="http://www.xbrl.org/2003/role/periodEndLabel">Liability related to the sale of future revenues - long-term</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="atra_LiabilityRelatedToTheSaleOfFutureRoyaltiesLongTerm_lbl" xlink:role="http://www.xbrl.org/2003/role/periodStartLabel">Liability related to sale of future revenues as of January 1, 2024</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="atra_AccruedResearchAndDevelopmentExpensesCurrent_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Accrued research and development expenses current.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="atra_AccruedResearchAndDevelopmentExpensesCurrent_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Accrued Research And Development Expenses Current</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="atra_AccruedResearchAndDevelopmentExpensesCurrent_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Accrued research and development expenses</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_InventoryRawMaterials_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Raw Materials</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_InventoryRawMaterials_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Inventory, Raw Materials, Gross</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_PaymentsForRoyalties_lbl" xlink:role="http://www.xbrl.org/2003/role/verboseLabel">Payments for royalties</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_PaymentsForRoyalties_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Repayment of the liability</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_PaymentsForRoyalties_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Payments for Royalties</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_PaymentsForRoyalties_lbl" xlink:role="http://www.xbrl.org/2009/role/negatedLabel">Repayment of the liability</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="atra_WarrantsExercised_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Warrants Exercised</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="atra_WarrantsExercised_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Warrants Exercised</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="atra_WarrantsExercised_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Warrants exercised</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ScheduleOfEmployeeServiceShareBasedCompensationAllocationOfRecognizedPeriodCostsTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Share-Based Payment Arrangement, Expensed and Capitalized, Amount [Table Text Block]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ScheduleOfEmployeeServiceShareBasedCompensationAllocationOfRecognizedPeriodCostsTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Schedule of Stock-based Compensation, Related to Employee and Nonemployee Stock Awards</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_FinanceLeaseLiabilityPaymentsDueAfterYearFive_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Finance leases, Thereafter</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_FinanceLeaseLiabilityPaymentsDueAfterYearFive_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Finance Lease, Liability, to be Paid, after Year Five</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ProceedsFromRoyaltiesReceived_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Proceeds from royalties</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ProceedsFromRoyaltiesReceived_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Proceeds from Royalties Received</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="atra_EmployeesAndNonEmployeesMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Employees and non-employees.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="atra_EmployeesAndNonEmployeesMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Employees And Non Employees [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="atra_EmployeesAndNonEmployeesMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Employees And Non Employees</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_OtherComprehensiveIncomeLossNetOfTaxPeriodIncreaseDecreaseAbstract_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Other Comprehensive Income (Loss), Net of Tax [Abstract]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_OtherComprehensiveIncomeLossNetOfTaxPeriodIncreaseDecreaseAbstract_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Other comprehensive gain (loss):</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_SubsequentEventMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Subsequent Event [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_SubsequentEventMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Subsequent Event [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="atra_CashEquivalentsFairValue_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Cash equivalents, fair value.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="atra_CashEquivalentsFairValue_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Cash Equivalents Fair Value</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="atra_CashEquivalentsFairValue_lbl" xlink:role="http://www.xbrl.org/2009/role/negatedLabel">Total Fair Value</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="atra_CashEquivalentsFairValue_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel">Cash Equivalents Fair Value, Total</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="atra_CashEquivalentsFairValue_lbl" xlink:role="http://www.xbrl.org/2009/role/negatedTotalLabel">Total Fair Value</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_PropertyPlantAndEquipmentAbstract_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Property, Plant and Equipment [Abstract]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="atra_IssuanceOfCommonStockThroughATMFacilitiesNetOfCommissionsAndOfferingCostsValue_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Issuance Of Common Stock Through A T M Facilities Net Of Commissions And Offering Costs Value</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="atra_IssuanceOfCommonStockThroughATMFacilitiesNetOfCommissionsAndOfferingCostsValue_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Issuance Of Common Stock Through A T M Facilities Net Of Commissions And Offering Costs Value</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_OtherAssetsNoncurrent_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Other Assets, Noncurrent</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_OtherAssetsNoncurrent_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Other assets</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_OtherAssetsNoncurrent_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel">Other Assets, Noncurrent, Total</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="atra_PriorNoticePeriodToIncreaseOrDecreaseMaximumOwnershipPercentage_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Prior notice period to increase or decrease maximum ownership percentage.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="atra_PriorNoticePeriodToIncreaseOrDecreaseMaximumOwnershipPercentage_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Prior Notice Period To Increase Or Decrease Maximum Ownership Percentage</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="atra_PriorNoticePeriodToIncreaseOrDecreaseMaximumOwnershipPercentage_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Prior notice period</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="atra_PierreFabreMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Pierre Fabre [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="atra_PierreFabreMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Pierre Fabre [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="atra_PierreFabreMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Pierre Fabre</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareByAntidilutiveSecuritiesAxis_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Antidilutive Securities [Axis]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareByAntidilutiveSecuritiesAxis_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Antidilutive Securities</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsVestedAndExpectedToVestOutstandingAggregateIntrinsicValue_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Vested and expected to vest, Aggregate Intrinsic Value</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsVestedAndExpectedToVestOutstandingAggregateIntrinsicValue_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Share-Based Compensation Arrangement by Share-Based Payment Award, Options, Vested and Expected to Vest, Outstanding, Aggregate Intrinsic Value</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="atra_CommonStockAveragePrice_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Common stock average price.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="atra_CommonStockAveragePrice_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Common Stock Average Price</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="atra_CommonStockAveragePrice_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Common stock average price</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="atra_LabEquipmentMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Lab equipment [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="atra_LabEquipmentMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Lab Equipment [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="atra_LabEquipmentMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Lab Equipment [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="atra_ScheduleOfLicenseCollaborationAndManufacturingAgreementsTable_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Schedule of license, collaboration and manufacturing agreements.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="atra_ScheduleOfLicenseCollaborationAndManufacturingAgreementsTable_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Schedule Of License Collaboration And Manufacturing Agreements [Table]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="atra_ScheduleOfLicenseCollaborationAndManufacturingAgreementsTable_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Schedule Of License Collaboration And Manufacturing Agreements [Table]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_AccumulatedOtherComprehensiveIncomeMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">AOCI Attributable to Parent [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_AccumulatedOtherComprehensiveIncomeMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Accumulated Other Comprehensive Income (Loss)</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="atra_CashReceived_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Cash Received</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="atra_CashReceived_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Cash Received</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_AssetAcquisitionContingentConsiderationTableTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Summary of the carrying amount assets sold and the gain on sale</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_AssetAcquisitionContingentConsiderationTableTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Asset Acquisition, Contingent Consideration [Table Text Block]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_LesseeOperatingLeaseOptionToExtend_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Lease option to extend additional term</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_LesseeOperatingLeaseOptionToExtend_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Lessee, Operating Lease, Option to Extend</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="atra_LeasePremisesTerminated_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Lease Premises Terminated</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="atra_LeasePremisesTerminated_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Lease Premises Terminated</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="atra_LeasePremisesTerminated_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Lease Premises Terminated</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="srt_MinimumMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Minimum [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="srt_MinimumMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Minimum [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="srt_MinimumMember_lbl" xlink:role="http://www.xbrl.org/2003/role/verboseLabel">Minimum</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriodWeightedAverageGrantDateFairValue_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Share-Based Compensation Arrangement by Share-Based Payment Award, Equity Instruments Other than Options, Grants in Period, Weighted Average Grant Date Fair Value</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriodWeightedAverageGrantDateFairValue_lbl" xlink:role="http://www.xbrl.org/2003/role/verboseLabel">Weighted Average Grant Date Fair Value, Granted</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_FinancialInstrumentAxis_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Financial Instrument [Axis]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_AssetsCurrentAbstract_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Assets, Current [Abstract]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_AssetsCurrentAbstract_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Current assets:</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_CommonStockIncludingAdditionalPaidInCapitalNetOfDiscountAbstract_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Common Stocks, Including Additional Paid in Capital, Net of Discount [Abstract]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_OtherComprehensiveIncomeLossTax_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Other comprehensive loss</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_OtherComprehensiveIncomeLossTax_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Other Comprehensive Income (Loss), Tax</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_OtherComprehensiveIncomeLossTax_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel">Other Comprehensive Income (Loss), Tax, Total</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_GainLossOnSalesOfAssetsAndAssetImpairmentCharges_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Gain (Loss) on Sale of Assets and Asset Impairment Charges</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_GainLossOnSalesOfAssetsAndAssetImpairmentCharges_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Impairment loss</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ClassOfWarrantOrRightNumberOfSecuritiesCalledByEachWarrantOrRight_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Class of Warrant or Right, Number of Securities Called by Each Warrant or Right</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ClassOfWarrantOrRightNumberOfSecuritiesCalledByEachWarrantOrRight_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Number of securities called by each warrant</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DisposalGroupIncludingDiscontinuedOperationOtherCurrentLiabilities_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Other assets</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DisposalGroupIncludingDiscontinuedOperationOtherCurrentLiabilities_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Disposal Group, Including Discontinued Operation, Other Liabilities, Current</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_LiabilitiesCurrentAbstract_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Liabilities, Current [Abstract]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_LiabilitiesCurrentAbstract_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Current liabilities:</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_RestructuringAndRelatedActivitiesDisclosureTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Restructuring and Related Activities Disclosure [Text Block]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_RestructuringAndRelatedActivitiesDisclosureTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Restructuring</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="atra_PaymentsReceivedFromSaleOfInventory_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Payments Received from Sale of Inventory</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="atra_PaymentsReceivedFromSaleOfInventory_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Payments Received from Sale of Inventory</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="atra_PaymentsReceivedFromSaleOfInventory_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Payments received from sale of inventory</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_OtherCurrentLiabilitiesTableTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Schedule of Other Current Liabilities</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_OtherCurrentLiabilitiesTableTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Other Current Liabilities [Table Text Block]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="atra_EmbeddedLeasesMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Embedded Leases</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="atra_EmbeddedLeasesMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Embedded Leases Member</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="atra_EmbeddedLeasesMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Embedded Leases Member</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_SharesOutstanding_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Shares, Outstanding</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_SharesOutstanding_lbl" xlink:role="http://www.xbrl.org/2003/role/periodEndLabel">Ending balance (in shares)</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_SharesOutstanding_lbl" xlink:role="http://www.xbrl.org/2003/role/periodStartLabel">Beginning balance (in shares)</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_AccountsReceivableNetCurrent_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Accounts Receivable, after Allowance for Credit Loss, Current</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_AccountsReceivableNetCurrent_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Accounts receivable</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_AccountsReceivableNetCurrent_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel">Accounts Receivable, after Allowance for Credit Loss, Current, Total</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="atra_LiabilitiesRelatedToIndemnificationAgreements_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Liabilities related to indemnification agreements.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="atra_LiabilitiesRelatedToIndemnificationAgreements_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Liabilities Related To Indemnification Agreements</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="atra_LiabilitiesRelatedToIndemnificationAgreements_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Liabilities related to indemnification agreements</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_RestrictedCashAndCashEquivalents_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Letter of credit maintained</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_RestrictedCashAndCashEquivalents_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Restricted Cash and Cash Equivalent</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_RestrictedCashAndCashEquivalents_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel">Restricted Cash and Cash Equivalents, Total</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ProceedsFromStockPlans_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Proceeds from Stock Plans</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ProceedsFromStockPlans_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Proceeds from employee stock awards</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="atra_SubLicensingFees_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Sub Licensing Fees</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="atra_SubLicensingFees_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Sub Licensing Fees</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="atra_SubLicensingFees_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Sub Licensing Fees</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_CommitmentsAndContingencies_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Commitments and Contingencies</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_CommitmentsAndContingencies_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Commitments and contingencies (Note 9)</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValue_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Share-Based Compensation Arrangement by Share-Based Payment Award, Equity Instruments Other than Options, Nonvested, Weighted Average Grant Date Fair Value</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValue_lbl" xlink:role="http://www.xbrl.org/2003/role/periodStartLabel">Balance as of December 31, 2025</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValue_lbl" xlink:role="http://www.xbrl.org/2003/role/periodEndLabel">Balance as of June 30, 2026</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_InventoryWorkInProcess_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Work-in-process</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_InventoryWorkInProcess_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Inventory, Work in Process, Gross</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="atra_Non-CashSettlementsAdjustments_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Non-Cash Settlements Adjustments</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="atra_Non-CashSettlementsAdjustments_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Non-Cash Settlements Adjustments</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="atra_Non-CashSettlementsAdjustments_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Non-cash settlements/adjustments</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="atra_MinimumCashRepayment_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Minimum cash repayment</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="atra_MinimumCashRepayment_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Minimum Cash Repayment</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="atra_MinimumCashRepayment_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Minimum cash repayment.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_GeneralAndAdministrativeExpenseMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">General and Administrative Expense [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_GeneralAndAdministrativeExpenseMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">General and administrative</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_OperatingLeaseLiability_lbl" xlink:role="http://www.xbrl.org/2003/role/verboseLabel">Total</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_OperatingLeaseLiability_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Operating Lease, Liability</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_OperatingLeaseLiability_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel">Operating Lease, Liability, Total</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_OperatingLeaseLiability_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Operating lease, liability</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DeferredIncomeCurrent_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Deferred Income, Current</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DeferredIncomeCurrent_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Deferred revenue</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_StockholdersEquityReverseStockSplit_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Stockholders' Equity, Reverse Stock Split</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_StockholdersEquityReverseStockSplit_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Reverse Stock Split</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_RestrictedCashCurrent_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Restricted cash</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_RestrictedCashCurrent_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Restricted Cash, Current</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_RestrictedCashCurrent_lbl" xlink:role="http://www.xbrl.org/2003/role/verboseLabel">Restricted cash - short term</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="atra_InducementPlanMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Inducement plan.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="atra_InducementPlanMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Inducement Plan [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="atra_InducementPlanMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Inducement Plan</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_LongTermPurchaseCommitmentByCategoryOfItemPurchasedAxis_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Category of Item Purchased [Axis]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="atra_SouthSanFranciscoCaliforniaMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">South San Francisco California.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="atra_SouthSanFranciscoCaliforniaMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">South San Francisco California [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="atra_SouthSanFranciscoCaliforniaMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">South San Francisco California</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_FinanceLeaseLiabilityCurrent_lbl" xlink:role="http://www.xbrl.org/2003/role/verboseLabel">Current portion of finance lease liabilities</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_FinanceLeaseLiabilityCurrent_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Other current liabilities</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_FinanceLeaseLiabilityCurrent_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Finance Lease, Liability, Current</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_LesseeLeaseDescriptionTable_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Lessee, Lease, Description [Table]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_FinanceLeaseWeightedAverageDiscountRatePercent_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Finance leases</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_FinanceLeaseWeightedAverageDiscountRatePercent_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Finance Lease, Weighted Average Discount Rate, Percent</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ProfitLoss_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Net income (loss)</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ProfitLoss_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Net Income (Loss), Including Portion Attributable to Noncontrolling Interest</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ProfitLoss_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel">Net Income (Loss), Including Portion Attributable to Noncontrolling Interest, Total</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="atra_TechnicalOperationsAndQualityExpense_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Technical operations and quality expense</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="atra_TechnicalOperationsAndQualityExpense_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Technical Operations And Quality Expense</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="atra_TechnicalOperationsAndQualityExpense_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Technical Operations And Quality Expense</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_LossContingenciesTable_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Loss Contingencies [Table]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_LossContingenciesTable_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Loss Contingencies [Table]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="atra_IncreaseDecreaseInOtherCurrentAsset_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Other current assets</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="atra_IncreaseDecreaseInOtherCurrentAsset_lbl" xlink:role="http://www.xbrl.org/2009/role/negatedLabel">Other current assets</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="atra_IncreaseDecreaseInOtherCurrentAsset_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Increase (Decrease) in Other Current Asset</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="atra_IncreaseDecreaseInOtherCurrentAsset_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Increase (Decrease) in Other Current Asset</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_WeightedAverageNumberOfSharesOutstandingBasic_lbl" xlink:role="http://www.xbrl.org/2003/role/verboseLabel">Weighted average shares outstanding - Basic</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_WeightedAverageNumberOfSharesOutstandingBasic_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Weighted Average Number of Shares Outstanding, Basic</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_WeightedAverageNumberOfSharesOutstandingBasic_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel">Weighted Average Number of Shares Outstanding, Basic, Total</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_WeightedAverageNumberOfSharesOutstandingBasic_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Basic weighted-average shares outstanding</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="atra_PercentageOfCommissionToBePaidOnGrossSalesProceedsOfCommonStockSold_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Percentage of commission to be paid on gross sales proceeds of common stock sold.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="atra_PercentageOfCommissionToBePaidOnGrossSalesProceedsOfCommonStockSold_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Percentage Of Commission To Be Paid On Gross Sales Proceeds Of Common Stock Sold</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="atra_PercentageOfCommissionToBePaidOnGrossSalesProceedsOfCommonStockSold_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Percentage of commission to be paid on gross sales proceeds of common stock sold</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsExercisableIntrinsicValue1_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Share-Based Compensation Arrangement by Share-Based Payment Award, Options, Exercisable, Intrinsic Value</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsExercisableIntrinsicValue1_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Exercisable, Aggregate Intrinsic Value</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_IncreaseDecreaseInOtherCurrentLiabilities_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Increase (Decrease) in Other Current Liabilities</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_IncreaseDecreaseInOtherCurrentLiabilities_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Other current liabilities</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_IncreaseDecreaseInOtherCurrentLiabilities_lbl" xlink:role="http://www.xbrl.org/2009/role/negatedLabel">Other current liabilities</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Schedule of Share-Based Compensation Arrangements by Share-Based Payment Award [Table]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Schedule Of Share Based Compensation Arrangements By Share Based Payment Award [Table]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="atra_IssuanceOfCommonStockNetOfCommissionsAndOfferingCostsValue_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Issuance of common stock, net of commissions and offering costs, value.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="atra_IssuanceOfCommonStockNetOfCommissionsAndOfferingCostsValue_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Issuance Of Common Stock Net Of Commissions And Offering Costs Value</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="atra_IssuanceOfCommonStockNetOfCommissionsAndOfferingCostsValue_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Issuance of common stock through ATM facilities, net of commissions and offering costs, value</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_PropertyPlantAndEquipmentTypeDomain_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Long-Lived Tangible Asset [Domain]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_PropertyPlantAndEquipmentTypeDomain_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Long-Lived Tangible Asset</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="atra_FinancialInstrumentsDisclosureAbstract_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">financial instruments disclosure.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="atra_FinancialInstrumentsDisclosureAbstract_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Financial Instruments Disclosure [Abstract]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_SubsequentEventsTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Subsequent Event</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_SubsequentEventsTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Subsequent Events [Text Block]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_AdjustmentsToAdditionalPaidInCapitalSharebasedCompensationRequisiteServicePeriodRecognitionValue_lbl" xlink:role="http://www.xbrl.org/2003/role/label">APIC, Share-Based Payment Arrangement, Increase for Cost Recognition</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_AdjustmentsToAdditionalPaidInCapitalSharebasedCompensationRequisiteServicePeriodRecognitionValue_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Stock-based compensation expense</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_AdjustmentsToAdditionalPaidInCapitalSharebasedCompensationRequisiteServicePeriodRecognitionValue_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel">APIC, Share-based Payment Arrangement, Increase for Cost Recognition, Total</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="atra_September2024Pre-FundedWarrantsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">September 2024 Pre-Funded Warrants [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="atra_September2024Pre-FundedWarrantsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">September 2024 Pre-Funded Warrants [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="atra_TerritoryAxis_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Territory [Axis]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="atra_TerritoryAxis_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Territory [Axis]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_StockholdersEquity_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel">Total stockholders' equity (deficit)</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_StockholdersEquity_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Equity, Attributable to Parent</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_StockholdersEquity_lbl" xlink:role="http://www.xbrl.org/2003/role/periodEndLabel">Ending balance</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_StockholdersEquity_lbl" xlink:role="http://www.xbrl.org/2003/role/periodStartLabel">Beginning balance</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_PreferredStockParOrStatedValuePerShare_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Preferred Stock, Par or Stated Value Per Share</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_PreferredStockParOrStatedValuePerShare_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Preferred stock, par value</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_BasisOfAccountingPolicyPolicyTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Basis of Accounting, Policy [Policy Text Block]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_BasisOfAccountingPolicyPolicyTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Basis of Presentation</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_StatementOfStockholdersEquityAbstract_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Statement of Stockholders' Equity [Abstract]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="atra_NetOfTransactionCosts_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Net of transaction costs</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="atra_NetOfTransactionCosts_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Net of Transaction Costs</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="atra_NetOfTransactionCosts_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Net of Transaction Costs</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_TypeOfRestructuringDomain_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Type of Restructuring [Domain]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="atra_PierreFabreCommercializationAgreementMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Pierre Fabre commercialization agreement.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="atra_PierreFabreCommercializationAgreementMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Pierre Fabre Commercialization Agreement [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="atra_PierreFabreCommercializationAgreementMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Pierre Fabre Commercialization Agreement</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_CashEquivalentsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Cash Equivalents [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_CashEquivalentsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Amounts Classified As Cash Equivalents</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_UseOfEstimates_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Use of Estimates</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_UseOfEstimates_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Use of Estimates, Policy [Policy Text Block]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_LeaseholdImprovementsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Leasehold Improvements [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_LeaseholdImprovementsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Leasehold Improvements [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="dei_EntityAddressAddressLine2_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Entity Address, Address Line Two</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="dei_EntityAddressAddressLine2_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Entity Address, Address Line Two</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="atra_LeaseCommencementDate_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Lease commencement date.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="atra_LeaseCommencementDate_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Lease Commencement Date</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="atra_LeaseCommencementDate_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Lease commencement date</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="dei_EntityIncorporationDateOfIncorporation_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Entity Incorporation, Date of Incorporation</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="dei_EntityIncorporationDateOfIncorporation_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Entity incorporation date</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_OtherAssetsCurrent_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Other current assets</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_OtherAssetsCurrent_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Other Assets, Current</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_PlanNameDomain_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Plan Name [Domain]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_PlanNameDomain_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Plan Name</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_IncreaseDecreaseInOtherOperatingAssets_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Other assets</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_IncreaseDecreaseInOtherOperatingAssets_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Increase (Decrease) in Other Operating Assets</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_IncreaseDecreaseInOtherOperatingAssets_lbl" xlink:role="http://www.xbrl.org/2009/role/negatedLabel">Other assets</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_IncreaseDecreaseInOtherOperatingAssets_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel">Increase (Decrease) in Other Operating Assets, Total</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_InterestExpense_lbl" xlink:role="http://www.xbrl.org/2009/role/negatedTerseLabel">Interest expense</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_InterestExpense_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Interest expense</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_InterestExpense_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Interest Expense, Operating and Nonoperating</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_InterestExpense_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel">Interest Expense, Total</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="atra_CommonStockValueRemainedAvailableToBeSold_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Common stock value remained available to be sold.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="atra_CommonStockValueRemainedAvailableToBeSold_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Common Stock Value Remained Available To Be Sold</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="atra_CommonStockValueRemainedAvailableToBeSold_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Common stock value remaining to be sold</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_FinanceLeaseLiabilityPaymentsDueNextTwelveMonths_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Finance Lease, Liability, to be Paid, Year One</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_FinanceLeaseLiabilityPaymentsDueNextTwelveMonths_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Finance leases, 2025</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ClassOfWarrantOrRightOutstanding_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Class of Warrant or Right, Outstanding</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ClassOfWarrantOrRightOutstanding_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Warrants outstanding</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ClassOfWarrantOrRightOutstanding_lbl" xlink:role="http://www.xbrl.org/2003/role/verboseLabel">Warrants outstanding</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="atra_MaximumCashRepayment_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Maximum cash repayment</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="atra_MaximumCashRepayment_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Maximum Cash Repayment</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="atra_MaximumCashRepayment_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Maximum cash repayment.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_RestrictedStockSharesIssuedNetOfSharesForTaxWithholdings_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Restricted Stock, Shares Issued Net of Shares for Tax Withholdings</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_RestrictedStockSharesIssuedNetOfSharesForTaxWithholdings_lbl" xlink:role="http://www.xbrl.org/2003/role/verboseLabel">RSU settlements, net of shares withheld, shares</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_RestructuringPlanAxis_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Restructuring Plan [Axis]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="atra_NonCashInvestingAndFinancingActivitiesAccruedCostsRelatedToAtTheMarketFacility_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Non Cash Investing And Financing Activities Accrued Costs Related To At The Market Facility</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="atra_NonCashInvestingAndFinancingActivitiesAccruedCostsRelatedToAtTheMarketFacility_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Non cash investing and financing activities accrued costs related to at the market facility.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="atra_NonCashInvestingAndFinancingActivitiesAccruedCostsRelatedToAtTheMarketFacility_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Accrued costs related to ATM facility</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="atra_IssuanceOfPreFundedWarrantsNetOfOfferingCosts_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Issuance Of Pre Funded Warrants Net Of Offering Costs</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="atra_IssuanceOfPreFundedWarrantsNetOfOfferingCosts_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Issuance Of Pre Funded Warrants Net Of Offering Costs</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="atra_IssuanceOfPreFundedWarrantsNetOfOfferingCosts_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Issuance of pre-funded warrants net of offering costs</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="dei_EntityAddressCityOrTown_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Entity Address, City or Town</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="dei_EntityAddressCityOrTown_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Entity Address, City or Town</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ScheduleOfEarningsPerShareDilutedByCommonClassTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Schedule of Earnings Per Share, Diluted, by Common Class, Including Two Class Method [Table Text Block]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ScheduleOfEarningsPerShareDilutedByCommonClassTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Schedule of Diluted net (loss) earnings per common share</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="atra_ARCommercializationAgreementMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">A&amp;R Commercialization Agreement [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="atra_ARCommercializationAgreementMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">A&amp;R Commercialization Agreement [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="atra_ARCommercializationAgreementMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">AR Commercialization Agreement [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_NumberOfReportableSegments_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Number of Reportable Segments</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_NumberOfReportableSegments_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Number of Reportable Segments</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="atra_TwoThousandEighteenInducementPlanMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Two thousand eighteen inducement plan.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="atra_TwoThousandEighteenInducementPlanMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Two Thousand Eighteen Inducement Plan [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="atra_TwoThousandEighteenInducementPlanMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">2018 Inducement Plan</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="dei_SecurityExchangeName_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Security Exchange Name</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="dei_SecurityExchangeName_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Security Exchange Name</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_LiabilityForFuturePolicyBenefitActivityTable_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Liability for Future Policy Benefit Activity [Table]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_PropertyPlantAndEquipmentGross_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Property, Plant and Equipment, Gross</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_PropertyPlantAndEquipmentGross_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Property and equipment, gross</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_PropertyPlantAndEquipmentGross_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel">Property, Plant and Equipment, Gross, Total</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_PropertyPlantAndEquipmentGross_lbl" xlink:role="http://www.xbrl.org/2003/role/periodStartLabel">Property, Plant and Equipment, Gross, Beginning Balance</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_PropertyPlantAndEquipmentGross_lbl" xlink:role="http://www.xbrl.org/2003/role/periodEndLabel">Property, Plant and Equipment, Gross, Ending Balance</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="srt_CounterpartyNameAxis_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Counterparty Name [Axis]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="srt_CounterpartyNameAxis_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Counterparty Name</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Income (Loss) from Continuing Operations before Income Taxes, Noncontrolling Interest</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel">Income (loss) before provision for (benefit from) income taxes</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsVestedAndExpectedToVestOutstandingNumber_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Share-Based Compensation Arrangement by Share-Based Payment Award, Options, Vested and Expected to Vest, Outstanding, Number</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsVestedAndExpectedToVestOutstandingNumber_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Vested and expected to vest, Shares</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_FinanceLeaseLiabilityPaymentsDueYearFive_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Finance Lease, Liability, to be Paid, Year Five</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_FinanceLeaseLiabilityPaymentsDueYearFive_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Finance leases, 2029</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_AntidilutiveSecuritiesNameDomain_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Antidilutive Securities, Name [Domain]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_AntidilutiveSecuritiesNameDomain_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Antidilutive Securities, Name</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_InventoryNet_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Inventory, Net</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_InventoryNet_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel">Total inventories</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_InventoryNet_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Inventories</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalents_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Cash, Cash Equivalent, Restricted Cash, and Restricted Cash Equivalent, Continuing Operation</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalents_lbl" xlink:role="http://www.xbrl.org/2003/role/periodEndLabel">Cash, cash equivalents and restricted cash at end of period</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalents_lbl" xlink:role="http://www.xbrl.org/2003/role/periodStartLabel">Cash, cash equivalents and restricted cash at beginning of period</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalents_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel">Total cash, cash equivalents and restricted cash</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_InterestPaidNet_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Interest Paid, Excluding Capitalized Interest, Operating Activity</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_InterestPaidNet_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Cash paid for interest</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ScheduleOfEmployeeServiceShareBasedCompensationAllocationOfRecognizedPeriodCostsTable_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Share-Based Payment Arrangement, Expensed and Capitalized, Amount [Table]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ScheduleOfEmployeeServiceShareBasedCompensationAllocationOfRecognizedPeriodCostsTable_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Schedule Of Employee Service Share Based Compensation Allocation Of Recognized Period Costs [Table]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="atra_AuroraColoradoMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Aurora Colorado</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="atra_AuroraColoradoMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Aurora Colorado Member</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="atra_AuroraColoradoMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Aurora Colorado Member</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="srt_RangeMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Statistical Measurement [Domain]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="srt_RangeMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Statistical Measurement</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ClassOfWarrantOrRightExercisePriceOfWarrantsOrRights1_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Class of Warrant or Right, Exercise Price of Warrants or Rights</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ClassOfWarrantOrRightExercisePriceOfWarrantsOrRights1_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Warrants, exercise price</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ClassOfWarrantOrRightExercisePriceOfWarrantsOrRights1_lbl" xlink:role="http://www.xbrl.org/2003/role/verboseLabel">Warrants, exercise price</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_AssetsCurrent_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Assets, Current</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_AssetsCurrent_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel">Total current assets</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_AllocatedShareBasedCompensationExpense_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Share-Based Payment Arrangement, Expense</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_AllocatedShareBasedCompensationExpense_lbl" xlink:role="http://www.xbrl.org/2003/role/verboseLabel">Total stock-based compensation expense</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="dei_DocumentPeriodEndDate_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Document Period End Date</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="dei_DocumentPeriodEndDate_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Document Period End Date</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_FairValueMeasurementsFairValueHierarchyDomain_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Fair Value Hierarchy and NAV [Domain]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsExercisableNumber_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Share-Based Compensation Arrangement by Share-Based Payment Award, Options, Exercisable, Number</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsExercisableNumber_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Exercisable, Shares</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="atra_TwoThousandFourteenEmployeeStockPurchasePlanMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Two thousand fourteen employee stock purchase plan.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="atra_TwoThousandFourteenEmployeeStockPurchasePlanMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Two Thousand Fourteen Employee Stock Purchase Plan [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="atra_TwoThousandFourteenEmployeeStockPurchasePlanMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">2014 Employee Stock Purchase Plan</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_FinanceLeaseLiabilityNoncurrentStatementOfFinancialPositionExtensibleList_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Finance Lease, Liability, Noncurrent, Statement of Financial Position [Extensible Enumeration]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_OperatingLeaseLiabilityCurrentStatementOfFinancialPositionExtensibleList_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Operating Lease, Liability, Current, Statement of Financial Position [Extensible Enumeration]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="atra_FreezersMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Freezers member.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="atra_FreezersMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Freezers</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="atra_FreezersMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Freezers [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_StatementOfFinancialPositionAbstract_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Statement of Financial Position [Abstract]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_RestrictedStockUnitsRSUMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Restricted Stock Units (RSUs) [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_RestrictedStockUnitsRSUMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Restricted Stock Units (RSUs)</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_RestrictedStockUnitsRSUMember_lbl" xlink:role="http://www.xbrl.org/2003/role/verboseLabel">Unvested RSUs</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="atra_IssuanceOfPreFundedWarrantsRegisteredDirectOfferingValue_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Issuance Of Pre Funded Warrants Registered Direct Offering Value</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="atra_IssuanceOfPreFundedWarrantsRegisteredDirectOfferingValue_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Issuance Of Pre Funded Warrants Registered Direct Offering Value</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="atra_IssuanceOfPreFundedWarrantsRegisteredDirectOfferingValue_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Issuance of pre-funded warrants to purchase common stock through an underwritten registered direct offering</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="atra_CommonStockReservedForFutureIssuanceTableTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Common stock reserved for future issuance.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="atra_CommonStockReservedForFutureIssuanceTableTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Common Stock Reserved For Future Issuance Table [Text Block]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="atra_CommonStockReservedForFutureIssuanceTableTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Schedule of Common Stock Reserved for Future Issuance Under Equity Incentive Plans</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="atra_AggregateMilestonePaymentsEntitleToReceiveUponAchievingCertainRegulatoryAndCommercialMilestones_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Aggregate milestone payments entitle to receive upon achieving certain regulatory and commercial milestones.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="atra_AggregateMilestonePaymentsEntitleToReceiveUponAchievingCertainRegulatoryAndCommercialMilestones_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Aggregate Milestone Payments Entitle To Receive Upon Achieving Certain Regulatory And Commercial Milestones</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="atra_AggregateMilestonePaymentsEntitleToReceiveUponAchievingCertainRegulatoryAndCommercialMilestones_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Aggregate milestone payments entitle to receive upon achieving certain regulatory and commercial milestones</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="atra_AdditionalMilestonePayments_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Additional milestone payments</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="atra_AdditionalMilestonePayments_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Additional Milestone Payments</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="atra_AdditionalMilestonePayments_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Additional Milestone Payments</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DisposalGroupNotDiscontinuedOperationGainLossOnDisposal_lbl" xlink:role="http://www.xbrl.org/2003/role/verboseLabel">Pre-tax gain on sale of business</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DisposalGroupNotDiscontinuedOperationGainLossOnDisposal_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Disposal Group, Not Discontinued Operation, Gain (Loss) on Disposal</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DisposalGroupNotDiscontinuedOperationGainLossOnDisposal_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Gain on sale of ATOM Facility</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ScheduleOfAntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareTable_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Antidilutive Security, Excluded EPS Calculation [Table]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ScheduleOfAntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareTable_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Schedule Of Antidilutive Securities Excluded From Computation Of Earnings Per Share [Table]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_StatementClassOfStockAxis_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Class of Stock [Axis]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="atra_SupplementalBalanceSheetInformationLineItems_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Supplemental Balance Sheet Information [Line Items]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="atra_SupplementalBalanceSheetInformationLineItems_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Supplemental Balance Sheet Information [Line Items]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="atra_ReductionOfDebtInExchangeForPre-FundedWarrants_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Reduction of debt in exchange for pre-funded warrants</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="atra_ReductionOfDebtInExchangeForPre-FundedWarrants_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Reduction of Debt in Exchange for Pre-Funded Warrants</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="atra_ReductionOfDebtInExchangeForPre-FundedWarrants_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Reduction of Debt in Exchange for Pre-Funded Warrants</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="atra_ReductionOfDebtInExchangeForPre-FundedWarrants_lbl" xlink:role="http://www.xbrl.org/2009/role/negatedLabel">Reduction of debt in exchange for pre-funded warrants</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ScheduleOfChangeInAssetRetirementObligationTableTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Summary of Activity for ARO Liabilities</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ScheduleOfChangeInAssetRetirementObligationTableTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Schedule of Change in Asset Retirement Obligation [Table Text Block]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_Liabilities_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Liabilities</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_Liabilities_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel">Total liabilities</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_EquityBasedArrangementsIndividualContractsTypeOfDeferredCompensationDomain_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Equity-Based Arrangements, Individual Contracts, Type of Deferred Compensation [Domain]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_EquityBasedArrangementsIndividualContractsTypeOfDeferredCompensationDomain_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Equity-Based Arrangements, Individual Contracts, Type of Deferred Compensation</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_USGovernmentAgenciesShorttermDebtSecuritiesMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">US Government Agencies Short-Term Debt Securities [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_USGovernmentAgenciesShorttermDebtSecuritiesMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Government Agency Obligations</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Financial Instruments [Domain]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_CapitalUnitsAuthorized_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Capital Units, Authorized</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_CapitalUnitsAuthorized_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Authorized capital stock</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_IncreaseDecreaseInDeferredRevenue_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Increase (Decrease) in Deferred Revenue</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_IncreaseDecreaseInDeferredRevenue_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Deferred revenue</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="atra_January2024WarrantsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">January 2024 Warrants [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="atra_January2024WarrantsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">January 2024 Warrants [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_LesseeOperatingLeaseLiabilityPaymentsDueYearTwo_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Lessee, Operating Lease, Liability, to be Paid, Year Two</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_LesseeOperatingLeaseLiabilityPaymentsDueYearTwo_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Operating leases, 2027</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsTable_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Disposal Groups, Including Discontinued Operations [Table]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_FinanceLeaseRightOfUseAssetAmortization_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Amortization expense</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_FinanceLeaseRightOfUseAssetAmortization_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Finance Lease, Right-of-Use Asset, Amortization</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_WeightedAverageNumberOfDilutedSharesOutstanding_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel">Weighted Average Number of Shares Outstanding, Diluted, Total</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_WeightedAverageNumberOfDilutedSharesOutstanding_lbl" xlink:role="http://www.xbrl.org/2003/role/verboseLabel">Weighted average shares outstanding - Diluted</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_WeightedAverageNumberOfDilutedSharesOutstanding_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Weighted Average Number of Shares Outstanding, Diluted</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_WeightedAverageNumberOfDilutedSharesOutstanding_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Diluted weighted-average shares outstanding</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_PropertyPlantAndEquipmentNetByTypeAbstract_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Property, Plant and Equipment, Net, by Type [Abstract]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="dei_EntityFileNumber_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Securities Act File Number</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="dei_EntityFileNumber_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Entity File Number</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_OtherComprehensiveIncomeUnrealizedHoldingGainLossOnSecuritiesArisingDuringPeriodNetOfTax_lbl" xlink:role="http://www.xbrl.org/2009/role/negatedLabel">Unrealized gain (loss) on available-for-sale securities</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_OtherComprehensiveIncomeUnrealizedHoldingGainLossOnSecuritiesArisingDuringPeriodNetOfTax_lbl" xlink:role="http://www.xbrl.org/2003/role/label">OCI, Debt Securities, Available-for-Sale, Unrealized Holding Gain (Loss), before Adjustment, after Tax</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_OtherComprehensiveIncomeUnrealizedHoldingGainLossOnSecuritiesArisingDuringPeriodNetOfTax_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Unrealized gain (loss) on available-for-sale securities</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="atra_OutLicenseAgreementsDisclosureTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Out-license Agreements.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="atra_OutLicenseAgreementsDisclosureTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Out License Agreements Disclosure [Text Block]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="atra_OutLicenseAgreementsDisclosureTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Out-license Agreements</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ProceedsFromSaleMaturityAndCollectionOfShorttermInvestments_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Proceeds from Sale, Maturity and Collection of Short-Term Investments</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ProceedsFromSaleMaturityAndCollectionOfShorttermInvestments_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Proceeds from maturities and sales of short-term investments</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ProceedsFromSaleMaturityAndCollectionOfShorttermInvestments_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel">Proceeds from Sale, Maturity and Collection of Short-term Investments, Total</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="dei_CoverAbstract_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Cover [Abstract]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="atra_LiabilityRelatedToTheSaleOfFutureRevenueCurrent_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Less: current portion classified within other accrued liabilities</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="atra_LiabilityRelatedToTheSaleOfFutureRevenueCurrent_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Liability Related To The Sale Of Future Revenue Current</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="atra_LiabilityRelatedToTheSaleOfFutureRevenueCurrent_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Liability related to the sale of future revenue current.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="atra_LiabilityRelatedToTheSaleOfFutureRevenueCurrent_lbl" xlink:role="http://www.xbrl.org/2003/role/verboseLabel">Liability related to the sale of future revenues - current portion</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="atra_LiabilityRelatedToTheSaleOfFutureRevenueCurrent_lbl" xlink:role="http://www.xbrl.org/2009/role/negatedLabel">Less: current portion</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="atra_CommonStockReservedForFutureIssuanceValue_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Common stock, reserved for future issuance value</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="atra_CommonStockReservedForFutureIssuanceValue_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Common Stock, Reserved for Future Issuance Value</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="atra_CommonStockReservedForFutureIssuanceValue_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Common stock, reserved for future issuance value</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsForfeitedInPeriod_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Share-Based Compensation Arrangement by Share-Based Payment Award, Equity Instruments Other than Options, Forfeited in Period</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsForfeitedInPeriod_lbl" xlink:role="http://www.xbrl.org/2009/role/negatedLabel">Shares, Forfeited</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_SupplementalBalanceSheetDisclosuresTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Supplemental Balance Sheet Information</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_SupplementalBalanceSheetDisclosuresTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Supplemental Balance Sheet Disclosures [Text Block]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_USTreasurySecuritiesMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">US Treasury Securities [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_USTreasurySecuritiesMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">U.S. Treasury Obligations</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfSharesAuthorized_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Share-Based Compensation Arrangement by Share-Based Payment Award, Number of Shares Authorized</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfSharesAuthorized_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Aggregate number of shares authorized</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_SaleOfStockNameOfTransactionDomain_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Sale of Stock [Domain]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_SaleOfStockNameOfTransactionDomain_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Sale of Stock</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_GeneralAndAdministrativeExpense_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">General and administrative expenses</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_GeneralAndAdministrativeExpense_lbl" xlink:role="http://www.xbrl.org/2003/role/label">General and Administrative Expense</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_GeneralAndAdministrativeExpense_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel">General and Administrative Expense, Total</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DeferredIncomeRevenueRecognized_lbl" xlink:role="http://www.xbrl.org/2009/role/negatedLabel">Recognized into commercialization revenue</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DeferredIncomeRevenueRecognized_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Recognized into commercialization revenue</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DeferredIncomeRevenueRecognized_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Deferred Income, Revenue Recognized</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_SubsequentEventTable_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Subsequent Event [Table]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="atra_MaximumPotentialMilestonePayments_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Maximum Potential Milestone Payments</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="atra_MaximumPotentialMilestonePayments_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Maximum Potential Milestone Payments</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="atra_MaximumPotentialMilestonePayments_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Maximum potential milestone payments</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="atra_Cashpaidforamountsincludedinmeasurementofleaseliabilitiesabstract_lbl" xlink:role="http://www.xbrl.org/2003/role/label">CashPaidForAmountsIncludedInMeasurementOfLeaseLiabilitiesAbstract</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="atra_Cashpaidforamountsincludedinmeasurementofleaseliabilitiesabstract_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">CashPaidForAmountsIncludedInMeasurementOfLeaseLiabilitiesAbstract</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="atra_Cashpaidforamountsincludedinmeasurementofleaseliabilitiesabstract_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Cash paid for amounts included in the measurement of lease liabilities:</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ShortTermDebtTypeDomain_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Short-Term Debt, Type [Domain]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsVestedAndExpectedToVestOutstandingWeightedAverageExercisePrice_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Share-Based Compensation Arrangement by Share-Based Payment Award, Options, Vested and Expected to Vest, Outstanding, Weighted Average Exercise Price</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsVestedAndExpectedToVestOutstandingWeightedAverageExercisePrice_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Stock options vested and expected to vest, Weighted Average Exercise Price</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_RestructuringCharges_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Restructuring Charges</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_RestructuringCharges_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel">Total restructuring charges</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_RestructuringCharges_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Restructuring charges</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ShortTermDebtTypeAxis_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Short-Term Debt, Type [Axis]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_NewAccountingPronouncementsPolicyPolicyTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/label">New Accounting Pronouncements, Policy [Policy Text Block]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_NewAccountingPronouncementsPolicyPolicyTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Recent Accounting Pronouncements</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareLineItems_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareLineItems_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ScheduleOfSharebasedCompensationRestrictedStockAndRestrictedStockUnitsActivityTableTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Share-Based Payment Arrangement, Restricted Stock and Restricted Stock Unit, Activity [Table Text Block]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ScheduleOfSharebasedCompensationRestrictedStockAndRestrictedStockUnitsActivityTableTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Summary of RSU Activity</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ContractWithCustomerLiabilityCurrent_lbl" xlink:role="http://www.xbrl.org/2009/role/negatedTerseLabel">Less: deferred revenue - current portion</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ContractWithCustomerLiabilityCurrent_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Less: deferred revenue - current portion</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ContractWithCustomerLiabilityCurrent_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Contract with Customer, Liability, Current</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ScheduleOfComprehensiveIncomeLossTableTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Comprehensive Income (Loss) [Table Text Block]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ScheduleOfComprehensiveIncomeLossTableTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Schedule Of Comprehensive Income Loss</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardAwardVestingPeriod1_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Share-Based Compensation Arrangement by Share-Based Payment Award, Award Vesting Period</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardAwardVestingPeriod1_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Share based compensation, vesting period</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_EmployeeSeveranceMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Employee Severance [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DisposalGroupIncludingDiscontinuedOperationConsideration_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Disposal Group, Including Discontinued Operation, Consideration</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DisposalGroupIncludingDiscontinuedOperationConsideration_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Cash consideration pursuant to asset purchase agreement</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_Depreciation_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Depreciation</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_Depreciation_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel">Depreciation, Total</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_Depreciation_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Depreciation expense</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognizedShareBasedAwardsOtherThanOptions_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Share-Based Payment Arrangement, Nonvested Award, Excluding Option, Cost Not yet Recognized, Amount</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognizedShareBasedAwardsOtherThanOptions_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Unrecognized stock-based compensation expense</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="atra_LiquidityRiskPolicyTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Liquidity risk.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="atra_LiquidityRiskPolicyTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Liquidity Risk Policy [Text Block]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="atra_LiquidityRiskPolicyTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Liquidity Risk</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_CommonStockSharesOutstanding_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Common Stock, Shares, Outstanding</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_CommonStockSharesOutstanding_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Common stock, shares outstanding</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_CommonStockSharesOutstanding_lbl" xlink:role="http://www.xbrl.org/2003/role/periodStartLabel">Common Stock, Shares, Outstanding, Beginning Balance</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_CommonStockSharesOutstanding_lbl" xlink:role="http://www.xbrl.org/2003/role/periodEndLabel">Common Stock, Shares, Outstanding, Ending Balance</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_OperatingLeaseLiabilityCurrent_lbl" xlink:role="http://www.xbrl.org/2003/role/verboseLabel">Current portion of operating lease liabilities</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_OperatingLeaseLiabilityCurrent_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Other current liabilities</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_OperatingLeaseLiabilityCurrent_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Operating Lease, Liability, Current</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="dei_DocumentTransitionReport_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Document Transition Report</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="dei_DocumentTransitionReport_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Document Transition Report</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ShortTermInvestments_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Short-term investments</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ShortTermInvestments_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Short-Term Investments</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ShortTermInvestments_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel">Short-Term Investments, Total</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DisposalGroupIncludingDiscontinuedOperationPropertyPlantAndEquipmentNoncurrent_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Property and equipment, net</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DisposalGroupIncludingDiscontinuedOperationPropertyPlantAndEquipmentNoncurrent_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Disposal Group, Including Discontinued Operation, Property, Plant and Equipment, Noncurrent</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ResearchAndDevelopmentExpense_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Research and development expenses</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ResearchAndDevelopmentExpense_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Research and Development Expense</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ResearchAndDevelopmentExpense_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel">Research and Development Expense, Total</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="atra_NumberOfTransacationCost_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Number Of transaction cost</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="atra_NumberOfTransacationCost_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Number Of Transacation Cost</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="atra_NumberOfTransacationCost_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Number Of Transacation Cost</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_StatementOfCashFlowsAbstract_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Statement of Cash Flows [Abstract]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="atra_TwoThousandAndFourteenEquityIncentivePlanMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Two thousand and fourteen equity incentive plan.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="atra_TwoThousandAndFourteenEquityIncentivePlanMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Two Thousand And Fourteen Equity Incentive Plan [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="atra_TwoThousandAndFourteenEquityIncentivePlanMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">2014 Equity Incentive Plan</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="atra_DevelopmentOrSalesBasedMilestonePaymentsEarnedOrReceived_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Development or sales-based milestone payments earned or received.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="atra_DevelopmentOrSalesBasedMilestonePaymentsEarnedOrReceived_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Development Or Sales Based Milestone Payments Earned Or Received</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="atra_DevelopmentOrSalesBasedMilestonePaymentsEarnedOrReceived_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Development or sales-based milestone payments earned or received</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="atra_LiabilityRelatedToTheSaleOfFutureRevenuesTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Liability Related to the Sale of Future Revenues</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="atra_LiabilityRelatedToTheSaleOfFutureRevenuesTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Liability Related to the Sale of Future Revenues Text Block</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="atra_LiabilityRelatedToTheSaleOfFutureRevenuesTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Liability Related to the Sale of Future Revenues Text Block</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ScheduleOfShareBasedCompensationStockOptionsActivityTableTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Share-Based Payment Arrangement, Option, Activity [Table Text Block]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ScheduleOfShareBasedCompensationStockOptionsActivityTableTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Summary of Stock Option Activity</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="atra_LicenseCollaborationAndManufacturingAgreementsLineItems_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">License, collaboration and manufacturing agreements.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="atra_LicenseCollaborationAndManufacturingAgreementsLineItems_lbl" xlink:role="http://www.xbrl.org/2003/role/label">License Collaboration And Manufacturing Agreements [Line Items]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="atra_LicenseCollaborationAndManufacturingAgreementsLineItems_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">License Collaboration And Manufacturing Agreements [Line Items]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="atra_ScheduleOfInformationProvidedToCODMTableTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Schedule of Information Provided to CODM [Table Text Block]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="atra_ScheduleOfInformationProvidedToCODMTableTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Schedule of Information Provided to CODM [Table Text Block]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="atra_ScheduleOfInformationProvidedToCODMTableTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Schedule of Information Provided to CODM</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_StockholdersEquityNoteDisclosureTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Stockholders' Equity (Deficit)</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_StockholdersEquityNoteDisclosureTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Equity [Text Block]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="atra_WorkforceRetaining_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Workforce Retaining</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="atra_WorkforceRetaining_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Workforce Retaining</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="atra_WorkforceRetaining_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Workforce Retaining</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="atra_RevenueRecognitionPerformanceObligation_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Revenue Recognition Performance Obligation</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="atra_RevenueRecognitionPerformanceObligation_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Revenue Recognition Performance Obligation</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="atra_RevenueRecognitionPerformanceObligation_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Revenue recognition, performance obligation</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_EarningsPerShareTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Earnings Per Share [Text Block]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_EarningsPerShareTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Net Income (Loss) per Common Share</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DiscontinuedOperationsAndDisposalGroupsAbstract_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Discontinued Operations and Disposal Groups [Abstract]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ComputerEquipmentMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Computer Equipment [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ComputerEquipmentMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Computer equipment and software [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_NetIncomeLoss_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel">Net income (loss)</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_NetIncomeLoss_lbl" xlink:role="http://www.xbrl.org/2003/role/verboseLabel">Net (loss) income</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingIntrinsicValue_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Share-Based Compensation Arrangement by Share-Based Payment Award, Options, Outstanding, Intrinsic Value</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingIntrinsicValue_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Aggregate intrinsic value</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_IncreaseDecreaseInInventories_lbl" xlink:role="http://www.xbrl.org/2009/role/negatedTerseLabel">Inventories</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_IncreaseDecreaseInInventories_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Increase (Decrease) in Inventories</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_IncreaseDecreaseInInventories_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel">Increase (Decrease) in Inventories, Total</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_OperatingLeaseCost_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Operating lease cost</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_OperatingLeaseCost_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Operating Lease, Cost</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ProceedsFromPaymentsForOtherFinancingActivities_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Proceeds from (Payment for) Other Financing Activity</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ProceedsFromPaymentsForOtherFinancingActivities_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Other financing activities, net</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_EarningsPerShareBasicLineItems_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Earnings Per Share, Basic, by Common Class, Including Two Class Method [Line Items]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="atra_MilestonePayments_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Milestone Payments</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="atra_MilestonePayments_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Milestone payments</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="atra_MilestonePayments_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Milestone payments</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_OperatingLeasePayments_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Operating cash flows for operating leases</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_OperatingLeasePayments_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Operating Lease, Payments</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_LiabilityForFuturePolicyBenefitActivityLineItems_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Liability for Future Policy Benefit, Activity [Line Items]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="atra_GoingConcernPolicyTextblock_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Going Concern [Policy TextBlock]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="atra_GoingConcernPolicyTextblock_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Going Concern [Policy TextBlock]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="atra_GoingConcernPolicyTextblock_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Going Concern</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ProceedsFromDivestitureOfBusinesses_lbl" xlink:role="http://www.xbrl.org/2003/role/verboseLabel">Net proceeds from sale of ATOM Facility</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ProceedsFromDivestitureOfBusinesses_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Proceeds from Divestiture of Businesses</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ProceedsFromDivestitureOfBusinesses_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Cash received on closing of Fujifilm Transaction</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="atra_ReceivableForEarlyContract_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Receivable for early contract</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="atra_ReceivableForEarlyContract_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Receivable for early contract</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_AssetsAbstract_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Assets [Abstract]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_AssetsAbstract_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Assets</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ResearchAndDevelopmentArrangementMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Research and Development Arrangement [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ConstructionInProgressMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Construction in Progress [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ConstructionInProgressMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Construction in Progress [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_RestructuringAndRelatedActivitiesAbstract_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Restructuring and Related Activities [Abstract]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="atra_Leaseoptiontoextendadditionalterm_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Lease option to extend additional term</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="atra_Leaseoptiontoextendadditionalterm_lbl" xlink:role="http://www.xbrl.org/2003/role/label">LeaseOptionToExtendAdditionalTerm</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="atra_Leaseoptiontoextendadditionalterm_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">LeaseOptionToExtendAdditionalTerm</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="dei_DocumentFiscalYearFocus_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Document Fiscal Year Focus</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="dei_DocumentFiscalYearFocus_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Document Fiscal Year Focus</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="atra_ThousandOaksCaliforniaMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Thousand Oaks California.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="atra_ThousandOaksCaliforniaMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Thousand Oaks California [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="atra_ThousandOaksCaliforniaMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Thousand Oaks California</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DeferredCompensationArrangementWithIndividualShareBasedPaymentsByTypeOfDeferredCompensationAxis_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Equity-Based Arrangements, Individual Contracts, Type of Deferred Compensation [Axis]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DeferredCompensationArrangementWithIndividualShareBasedPaymentsByTypeOfDeferredCompensationAxis_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Equity-Based Arrangements, Individual Contracts, Type of Deferred Compensation</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_NetCashProvidedByUsedInInvestingActivitiesAbstract_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Cash Provided by (Used in) Investing Activity, Including Discontinued Operation [Abstract]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_NetCashProvidedByUsedInInvestingActivitiesAbstract_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Investing activities</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_AccountsPayableCurrent_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Accounts Payable, Current</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_AccountsPayableCurrent_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Accounts payable</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_AccountsPayableCurrent_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel">Accounts Payable, Current, Total</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="atra_CarryingValueOfAssetsSoldAndGainOnSaleTableTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Summary of the carrying amount assets sold and the gain on sale</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="atra_CarryingValueOfAssetsSoldAndGainOnSaleTableTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Carrying Value Of Assets Sold And Gain On Sale [Table Text Block]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="atra_CarryingValueOfAssetsSoldAndGainOnSaleTableTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Carrying Value Of Assets Sold And Gain On Sale [Table Text Block]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ResearchAndDevelopmentExpenseMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Research and Development Expense [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ResearchAndDevelopmentExpenseMember_lbl" xlink:role="http://www.xbrl.org/2003/role/verboseLabel">Research and development</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="atra_ProceedsFromIssuanceOfCommonStockNet_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Proceeds from issuance of common stock net.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="atra_ProceedsFromIssuanceOfCommonStockNet_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Proceeds From Issuance Of Common Stock Net</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="atra_ProceedsFromIssuanceOfCommonStockNet_lbl" xlink:role="http://www.xbrl.org/2003/role/verboseLabel">Proceeds from sale of pre-funded warrants to purchase common stock, net</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_RestructuringCostAndReserveLineItems_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Restructuring Cost and Reserve [Line Items]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="atra_LicenseCollaborationAndManufacturingAgreementsAbstract_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">License, collaboration and manufacturing agreements.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="atra_LicenseCollaborationAndManufacturingAgreementsAbstract_lbl" xlink:role="http://www.xbrl.org/2003/role/label">License Collaboration And Manufacturing Agreements [Abstract]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="atra_UpfrontAndMilestonePayments_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Upfront and milestone payments</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="atra_UpfrontAndMilestonePayments_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Upfront and Milestone Payments</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="atra_UpfrontAndMilestonePayments_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Upfront and Milestone Payments</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_CommitmentsAndContingenciesDisclosureAbstract_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Commitments and Contingencies Disclosure [Abstract]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="atra_LicenseAndCollaborationRevenue_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">License and collaboration revenue.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="atra_LicenseAndCollaborationRevenue_lbl" xlink:role="http://www.xbrl.org/2003/role/label">License And Collaboration Revenue</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="atra_LicenseAndCollaborationRevenue_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">License and collaboration revenue</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_LesseeOperatingLeaseLiabilityPaymentsDueNextTwelveMonths_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Lessee, Operating Lease, Liability, to be Paid, Year One</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_LesseeOperatingLeaseLiabilityPaymentsDueNextTwelveMonths_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Operating leases, 2026</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ProceedsFromLicenseFeesReceived_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Proceeds from License Fees Received</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ProceedsFromLicenseFeesReceived_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Proceeds from License Fees Received</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="atra_IssuanceOfPreFundedWarrantsRegisteredDirectOfferingShares_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Issuance of pre-funded warrants to purchase common stock through an underwritten registered direct offering, Shares</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="atra_IssuanceOfPreFundedWarrantsRegisteredDirectOfferingShares_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Issuance Of Pre Funded Warrants Registered Direct Offering Shares</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="atra_IssuanceOfPreFundedWarrantsRegisteredDirectOfferingShares_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Issuance Of Pre Funded Warrants Registered Direct Offering Shares</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_LesseeOperatingLeaseLiabilityPaymentsDueAfterYearFive_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Operating leases, Thereafter</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_LesseeOperatingLeaseLiabilityPaymentsDueAfterYearFive_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Lessee, Operating Lease, Liability, to be Paid, after Year Five</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="atra_UnderwrittenPublicOfferingMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Underwritten public offering.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="atra_UnderwrittenPublicOfferingMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Underwritten Public Offering [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="atra_UnderwrittenPublicOfferingMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Underwritten Public Offering</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DisclosureOfCompensationRelatedCostsSharebasedPaymentsAbstract_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Share-Based Payment Arrangement [Abstract]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_SubsidiarySaleOfStockAxis_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Sale of Stock [Axis]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_SubsidiarySaleOfStockAxis_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Sale of Stock</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_Revenues_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Revenues</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_Revenues_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel">Revenues, Total</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_Revenues_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Revenue</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_NetCashProvidedByUsedInInvestingActivities_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Cash Provided by (Used in) Investing Activity, Including Discontinued Operation</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_NetCashProvidedByUsedInInvestingActivities_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel">Net cash (used in) provided by investing activities</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="atra_WarrantMaximumOwnershipMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Warrant Maximum Ownership [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="atra_WarrantMaximumOwnershipMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Warrant Maximum Ownership [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="atra_WarrantMaximumOwnershipMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Warrant maximum ownership [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_FinanceLeaseWeightedAverageRemainingLeaseTerm1_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Finance leases</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_FinanceLeaseWeightedAverageRemainingLeaseTerm1_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Finance Lease, Weighted Average Remaining Lease Term</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="dei_Security12bTitle_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Title of 12(b) Security</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="dei_Security12bTitle_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Title of 12(b) Security</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardOptionsForfeituresInPeriodWeightedAverageExercisePrice_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Share-Based Compensation Arrangements by Share-Based Payment Award, Options, Forfeitures in Period, Weighted Average Exercise Price</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardOptionsForfeituresInPeriodWeightedAverageExercisePrice_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Forfeited or expired, Weighted Average Exercise price</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsForfeituresWeightedAverageGrantDateFairValue_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Share-Based Compensation Arrangement by Share-Based Payment Award, Equity Instruments Other than Options, Forfeitures, Weighted Average Grant Date Fair Value</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsForfeituresWeightedAverageGrantDateFairValue_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Weighted Average Grant Date Fair Value, Forfeited</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_AvailableForSaleSecuritiesDebtMaturitiesAfterOneThroughFiveYearsAmortizedCost_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Debt Securities, Available-for-Sale, Amortized Cost, Maturity, Allocated and Single Maturity Date, after Year One Through Five</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_AvailableForSaleSecuritiesDebtMaturitiesAfterOneThroughFiveYearsAmortizedCost_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Maturing in one to five years, Amortized cost</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_MoneyMarketFundsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Money Market Funds [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_MoneyMarketFundsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Money Market Funds</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="atra_RegulatoryAndQualityExpense_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Regulatory and Quality Expense</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="atra_RegulatoryAndQualityExpense_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Regulatory and Quality Expense</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="atra_RegulatoryAndQualityExpense_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Regulatory expense</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="atra_StockIssuedDuringPeriodSharesStockOptionsExercisedOfPreFundedWarrants_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Exercise of pre-funded warrants, Share</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="atra_StockIssuedDuringPeriodSharesStockOptionsExercisedOfPreFundedWarrants_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Stock Issued During Period Shares Stock Options Exercised Of Pre Funded Warrants</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="atra_StockIssuedDuringPeriodSharesStockOptionsExercisedOfPreFundedWarrants_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Stock issued during period shares stock options exercised of pre-funded warrants.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="atra_MskLicenseAgreementsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">MSK License Agreements [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="atra_MskLicenseAgreementsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">MSK License Agreements [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="atra_MskLicenseAgreementsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">MSK License Agreements</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_OtherLiabilitiesNoncurrent_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Other Liabilities, Noncurrent</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_OtherLiabilitiesNoncurrent_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Other long-term liabilities</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_OtherLiabilitiesNoncurrent_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel">Other Liabilities, Noncurrent, Total</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_RestructuringPlanDomain_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Restructuring Plan [Domain]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="atra_DescriptionOfBusinessAbstract_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Description of business.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="atra_DescriptionOfBusinessAbstract_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Description Of Business [Abstract]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_AvailableForSaleSecuritiesDebtMaturitiesAfterOneThroughFiveYearsFairValue_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Debt Securities, Available-for-Sale, Fair Value, Maturity, Allocated and Single Maturity Date, after Year One Through Five</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_AvailableForSaleSecuritiesDebtMaturitiesAfterOneThroughFiveYearsFairValue_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Maturing in one to five years, Estimated fair value</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_PropertyPlantAndEquipmentTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Property, Plant and Equipment [Table Text Block]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_PropertyPlantAndEquipmentTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Schedule of Property and Equipment</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingWeightedAverageExercisePrice_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Share-Based Compensation Arrangement by Share-Based Payment Award, Options, Outstanding, Weighted Average Exercise Price</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingWeightedAverageExercisePrice_lbl" xlink:role="http://www.xbrl.org/2003/role/periodEndLabel">Outstanding, Weighted Average Exercise Price, ending balance</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingWeightedAverageExercisePrice_lbl" xlink:role="http://www.xbrl.org/2003/role/periodStartLabel">Outstanding, Weighted Average Exercise Price, beginning balance</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_AdditionalPaidInCapitalMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Additional Paid-in Capital [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_AdditionalPaidInCapitalMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Additional Paid-in Capital</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="atra_OperatingLeaseCostIncludingShortTermLease_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Operating lease cost including short term lease.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="atra_OperatingLeaseCostIncludingShortTermLease_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Operating Lease Cost Including Short Term Lease</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="atra_OperatingLeaseCostIncludingShortTermLease_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel">Total operating lease cost</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_FairValueMeasurementFrequencyDomain_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Measurement Frequency [Domain]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_FairValueMeasurementFrequencyDomain_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Measurement Frequency</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_OperatingLeaseLiabilityNoncurrentStatementOfFinancialPositionExtensibleList_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Operating Lease, Liability, Noncurrent, Statement of Financial Position [Extensible Enumeration]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_IncomeStatementLocationAxis_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Statement of Income Location, Balance [Axis]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_IncomeStatementLocationAxis_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Income Statement Location</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="atra_MsaMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">MSA</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="atra_MsaMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">MSA [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="atra_MsaMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">MSA member.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="dei_TradingSymbol_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Trading Symbol</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="dei_TradingSymbol_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Trading Symbol</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_PropertyPlantAndEquipmentDisclosureTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Property, Plant and Equipment Disclosure [Text Block]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_PropertyPlantAndEquipmentDisclosureTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Property and Equipment</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_AvailableForSaleSecuritiesDebtMaturitiesWithinOneYearAmortizedCost_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Debt Securities, Available-for-Sale, Amortized Cost, Maturity, Allocated and Single Maturity Date, Year One</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_AvailableForSaleSecuritiesDebtMaturitiesWithinOneYearAmortizedCost_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Maturing within one year, Amortized cost</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="atra_Operatingleasecostabstract_lbl" xlink:role="http://www.xbrl.org/2003/role/label">OperatingLeaseCostAbstract</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="atra_Operatingleasecostabstract_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">OperatingLeaseCostAbstract</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="atra_Operatingleasecostabstract_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Operating lease cost:</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="atra_CommercializationRevenue_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Commercialization revenue</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="atra_CommercializationRevenue_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Commercialization Revenue</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="atra_CommercializationRevenue_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Commercialization Revenue</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_SubsequentEventTypeAxis_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Subsequent Event Type [Axis]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DisposalGroupIncludingDiscontinuedOperationPrepaidAndOtherAssetsCurrent_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Prepaid expenses and other current assets</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DisposalGroupIncludingDiscontinuedOperationPrepaidAndOtherAssetsCurrent_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Disposal Group, Including Discontinued Operation, Prepaid and Other Assets, Current</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_EmployeeRelatedLiabilitiesCurrent_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Employee-related Liabilities, Current</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_EmployeeRelatedLiabilitiesCurrent_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Accrued compensation</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_EmployeeRelatedLiabilitiesCurrent_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel">Employee-related Liabilities, Current, Total</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_NetCashProvidedByUsedInFinancingActivitiesAbstract_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Cash Provided by (Used in) Financing Activity, Including Discontinued Operation [Abstract]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_NetCashProvidedByUsedInFinancingActivitiesAbstract_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Financing activities</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_LesseeFinanceLeaseTermOfContract1_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Lease initial term</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_LesseeFinanceLeaseTermOfContract1_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Lessee, Finance Lease, Term of Contract</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_FairValueMeasurementsRecurringMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Fair Value, Recurring [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_FairValueMeasurementsRecurringMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Fair Value, Measurements, Recurring</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="atra_SummaryOfEstimatedFairValueAndRelatedValuationInputHierarchyOfAvailableForSaleSecuritiesTableTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Summary of estimated fair value and related valuation input hierarchy of available-for-sale securities.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="atra_SummaryOfEstimatedFairValueAndRelatedValuationInputHierarchyOfAvailableForSaleSecuritiesTableTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Summary Of Estimated Fair Value And Related Valuation Input Hierarchy Of Available For Sale Securities Table [Text Block]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="atra_SummaryOfEstimatedFairValueAndRelatedValuationInputHierarchyOfAvailableForSaleSecuritiesTableTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Summary of Estimated Fair Value and Related Valuation Input Hierarchy of Available-for-Sale Securities</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_LesseeOperatingLeaseLiabilityPaymentsDue_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel">Operating leases, Total minimum payments</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_LesseeOperatingLeaseLiabilityPaymentsDue_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Lessee, Operating Lease, Liability, to be Paid</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="atra_GainOnDerecognitionOfTheFinanceLeaseLiability_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Gain on Derecognition of the Finance Lease Liability</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="atra_GainOnDerecognitionOfTheFinanceLeaseLiability_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Gain on Derecognition of the Finance Lease Liability</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="atra_GainOnDerecognitionOfTheFinanceLeaseLiability_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Gain on derecognition of finance lease liability</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_LesseeOperatingLeaseLiabilityUndiscountedExcessAmount_lbl" xlink:role="http://www.xbrl.org/2009/role/negatedLabel">Less: amount representing interest</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_LesseeOperatingLeaseLiabilityUndiscountedExcessAmount_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Less: amount representing interest</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_LesseeOperatingLeaseLiabilityUndiscountedExcessAmount_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Lessee, Operating Lease, Liability, Undiscounted Excess Amount</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="atra_CostOfCommercializationRevenue_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Cost of commercialization revenue</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="atra_CostOfCommercializationRevenue_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Cost of Commercialization Revenue</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="atra_CostOfCommercializationRevenue_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Cost of Commercialization Revenue</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_OtherRestructuringMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Other Restructuring [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_OtherRestructuringMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Restructuring [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_StatementEquityComponentsAxis_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Equity Components [Axis]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_StatementEquityComponentsAxis_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Equity Components</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_EquityComponentDomain_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Equity Component [Domain]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_EquityComponentDomain_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Equity Component</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="atra_UpfrontCashPaymentReceived_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Upfront cash payment received.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="atra_UpfrontCashPaymentReceived_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Upfront Cash Payment Received</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="atra_UpfrontCashPaymentReceived_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Upfront cash payment received</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="atra_RestructuringLabialityActivityTableTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Restructuring Labiality Activity Table Text Block</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="atra_RestructuringLabialityActivityTableTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Restructuring Labiality Activity Table Text Block</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="atra_RestructuringLabialityActivityTableTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Restructuring of Labiality Activity</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="atra_ComputerEquipmentAndSoftwareMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Computer equipment and software.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="atra_ComputerEquipmentAndSoftwareMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Computer Equipment And Software [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="atra_ComputerEquipmentAndSoftwareMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Computer Equipment and Software</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_MachineryAndEquipmentMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Machinery and Equipment [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_MachineryAndEquipmentMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Machinery and Equipment [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardExpirationPeriod_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Share-Based Compensation Arrangement by Share-Based Payment Award, Expiration Period</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardExpirationPeriod_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Share based compensation award expiration period</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_RestructuringIncurredCostStatementOfIncomeOrComprehensiveIncomeExtensibleEnumeration_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Restructuring Charges, Statement of Income or Comprehensive Income [Extensible Enumeration]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DepreciationAndAmortization_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Depreciation, Depletion and Amortization, Nonproduction</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DepreciationAndAmortization_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Depreciation and amortization expense</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DepreciationAndAmortization_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel">Depreciation, Depletion and Amortization, Nonproduction, Total</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="srt_MaximumMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Maximum [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="srt_MaximumMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Maximum [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="srt_RangeAxis_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Statistical Measurement [Axis]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="srt_RangeAxis_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Statistical Measurement</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardOptionsExercisesInPeriodWeightedAverageExercisePrice_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Share-Based Compensation Arrangements by Share-Based Payment Award, Options, Exercises in Period, Weighted Average Exercise Price</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardOptionsExercisesInPeriodWeightedAverageExercisePrice_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Exercised, Weighted Average Exercise Price</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ContractWithCustomerLiabilityNoncurrent_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Contract with Customer, Liability, Noncurrent</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ContractWithCustomerLiabilityNoncurrent_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Deferred revenue - long-term</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ContractWithCustomerLiabilityNoncurrent_lbl" xlink:role="http://www.xbrl.org/2003/role/verboseLabel">Deferred revenue - long-term, June 30, 2026</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_CommonStockValue_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Common Stock, Value, Issued</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_CommonStockValue_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel">Common Stock, Value, Issued, Total</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_CommonStockValue_lbl" xlink:role="http://www.xbrl.org/2003/role/periodStartLabel">Common Stock, Value, Issued, Beginning Balance</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_CommonStockValue_lbl" xlink:role="http://www.xbrl.org/2003/role/periodEndLabel">Common Stock, Value, Issued, Ending Balance</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_CommonStockValue_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Common stock - $0.0001 par value, 500,000 shares authorized as of June 30, 2026 and December 31, 2025; 9,443 and 7,324 shares issued and outstanding as of June 30, 2026 and December 31, 2025, respectively</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_OtherLongTermDebtCurrent_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Other long-term liabilities</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_OtherLongTermDebtCurrent_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Other Long-Term Debt, Current</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_FinanceLeasePrincipalPayments_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Financing cash flows for finance leases</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_FinanceLeasePrincipalPayments_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Finance Lease, Principal Payments</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_FinanceLeasePrincipalPayments_lbl" xlink:role="http://www.xbrl.org/2009/role/negatedTerseLabel">Principal payments on finance lease obligations</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_FinanceLeasePrincipalPayments_lbl" xlink:role="http://www.xbrl.org/2009/role/negatedLabel">Financing cash flows for finance leases</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_LiabilitiesSubjectToCompromiseEarlyContractTerminationFees_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Agreement early termination liability</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_LiabilitiesSubjectToCompromiseEarlyContractTerminationFees_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Liabilities Subject to Compromise, Early Contract Termination Fees</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_EquipmentMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Equipment [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_EquipmentMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Lab Equipment</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="atra_MaximumOwnershipPercentage_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Maximum ownership percentage.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="atra_MaximumOwnershipPercentage_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Maximum Ownership Percentage</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="atra_MaximumOwnershipPercentage_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Maximum ownership Percentage</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="atra_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOptionsAndRestrictedStockUnitsOutstanding_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Share based compensation arrangement by share based payment award equity instruments options and restricted stock units outstanding.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="atra_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOptionsAndRestrictedStockUnitsOutstanding_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Share Based Compensation Arrangement By Share Based Payment Award Equity Instruments Options And Restricted Stock Units Outstanding</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="atra_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOptionsAndRestrictedStockUnitsOutstanding_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Outstanding options and RSUs</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_AmortizationOfFinancingCosts_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Amortization of debt discount and debt issuance costs</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_AmortizationOfFinancingCosts_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Amortization of Debt Issuance Costs</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="atra_Incrementalcontractualobligationsunderleaseamendment_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Incremental contractual obligations under lease amendment</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="atra_Incrementalcontractualobligationsunderleaseamendment_lbl" xlink:role="http://www.xbrl.org/2003/role/label">IncrementalContractualObligationsUnderLeaseAmendment</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="atra_Incrementalcontractualobligationsunderleaseamendment_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">IncrementalContractualObligationsUnderLeaseAmendment</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_OtherNonoperatingIncomeExpenseAbstract_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Other income (expense), net:</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_OtherNonoperatingIncomeExpenseAbstract_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Other Nonoperating Income (Expense) [Abstract]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="atra_CowenAndCompanyLimitedLiabilityCompanyMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Cowen and Company Limited Liability Company.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="atra_CowenAndCompanyLimitedLiabilityCompanyMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Cowen And Company Limited Liability Company [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="atra_CowenAndCompanyLimitedLiabilityCompanyMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Cowen</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_PreferredStockSharesAuthorized_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Preferred Stock, Shares Authorized</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_PreferredStockSharesAuthorized_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Preferred stock, shares authorized</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_CostsAndExpenses_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel">Total costs and operating expenses</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_CostsAndExpenses_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Costs and Expenses</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="atra_EffectOfDilutiveSecuritiesShares_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Effect of Dilutive Securities Shares</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="atra_EffectOfDilutiveSecuritiesShares_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Effect of Dilutive Securities Shares</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="atra_EffectOfDilutiveSecuritiesShares_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Effect of dilutive securities</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="dei_EntityRegistrantName_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Entity Registrant Name</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="dei_EntityRegistrantName_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Entity Registrant Name</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="atra_RevenueRecognitionPerformanceSatisfiedOrPartiallySatisfiedPriorPeriod_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Revenue Recognition Performance Satisfied or Partially Satisfied Prior Period</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="atra_RevenueRecognitionPerformanceSatisfiedOrPartiallySatisfiedPriorPeriod_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Revenue Recognition Performance Satisfied or Partially Satisfied Prior Period</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="atra_RevenueRecognitionPerformanceSatisfiedOrPartiallySatisfiedPriorPeriod_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Revenue recognition, performance satisfied or partially satisfied prior period</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_AvailableForSaleDebtSecuritiesAccumulatedGrossUnrealizedLossBeforeTax_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Debt Securities, Available-for-Sale, Accumulated Gross Unrealized Loss, before Tax</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_AvailableForSaleDebtSecuritiesAccumulatedGrossUnrealizedLossBeforeTax_lbl" xlink:role="http://www.xbrl.org/2009/role/negatedLabel">Total Unrealized Loss</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_AvailableForSaleDebtSecuritiesAccumulatedGrossUnrealizedLossBeforeTax_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Total Unrealized Loss</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="atra_CommercializationRevenueMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Commercialization Revenue [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="atra_CommercializationRevenueMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Commercialization Revenue [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="atra_CommercializationRevenueMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Commercialization Revenue [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_OtherNonoperatingIncomeExpense_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Other income (expense), net</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_OtherNonoperatingIncomeExpense_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Other Nonoperating Income (Expense)</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_OtherNonoperatingIncomeExpense_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel">Other Nonoperating Income (Expense), Total</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_SubsequentEventsAbstract_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Subsequent Events [Abstract]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="atra_GainOnDerecognitionOfTheOperatingLeaseLiability_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Gain on derecognition of operating lease liability</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="atra_GainOnDerecognitionOfTheOperatingLeaseLiability_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Gain on Derecognition of the Operating Lease Liability</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="atra_GainOnDerecognitionOfTheOperatingLeaseLiability_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Gain on Derecognition of the Operating Lease Liability</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="atra_ReductionInCurrentWorkforcePercentage_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Reduction in current workforce</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="atra_ReductionInCurrentWorkforcePercentage_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Reduction In Current Workforce Percentage</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="atra_ReductionInCurrentWorkforcePercentage_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Reduction in current workforce percentage</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_IncomeTaxExpenseBenefit_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Provision for (benefit from) income taxes</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_IncomeTaxExpenseBenefit_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Income Tax Expense (Benefit)</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_IncomeTaxExpenseBenefit_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel">Income Tax Expense (Benefit), Total</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_FairValueByMeasurementFrequencyAxis_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Measurement Frequency [Axis]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_FairValueByMeasurementFrequencyAxis_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Measurement Frequency</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="atra_AggregateOfferingPriceOfCommonStock_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Aggregate Offering Price of common stock.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="atra_AggregateOfferingPriceOfCommonStock_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Aggregate Offering Price Of Common Stock</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="atra_AggregateOfferingPriceOfCommonStock_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Common stock aggregate offering price</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ProceedsFromIssuanceOfCommonStock_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Proceeds from Issuance of Common Stock</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ProceedsFromIssuanceOfCommonStock_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Proceeds from issuance of common stock through ATM facilities, net</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="atra_OtherNonCashItemsNet_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Other non-cash items, net</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="atra_OtherNonCashItemsNet_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Other non-cash items, net</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="atra_OtherNonCashItemsNet_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Other non-cash items, net</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Share-Based Compensation Arrangement by Share-Based Payment Award [Line Items]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Share Based Compensation Arrangement By Share Based Payment Award [Line Items]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="dei_EntityCommonStockSharesOutstanding_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Entity Common Stock, Shares Outstanding</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="dei_EntityCommonStockSharesOutstanding_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Entity Common Stock, Shares Outstanding</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DeferredRevenueRevenueRecognized1_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Deferred Revenue, Revenue Recognized</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DeferredRevenueRevenueRecognized1_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Deferred revenue, revenue recognized</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_AccumulatedOtherComprehensiveIncomeLossNetOfTax_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Accumulated Other Comprehensive Income (Loss), Net of Tax</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_AccumulatedOtherComprehensiveIncomeLossNetOfTax_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel">Accumulated Other Comprehensive Income (Loss), Net of Tax, Total</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_AccumulatedOtherComprehensiveIncomeLossNetOfTax_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Accumulated other comprehensive income (loss)</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_SupplementalUnemploymentBenefitsSeveranceBenefits_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Supplemental Unemployment Benefits, Severance Benefits</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_SupplementalUnemploymentBenefitsSeveranceBenefits_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Supplemental Unemployment Benefits, Severance Benefits</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="atra_DeterminedUpfrontPaymentConstitutedEntireConsiderationIncludedInTransactionPrice_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Determined upfront payment constituted entire consideration included in transaction price.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="atra_DeterminedUpfrontPaymentConstitutedEntireConsiderationIncludedInTransactionPrice_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Determined Upfront Payment Constituted Entire Consideration Included In Transaction Price</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="atra_DeterminedUpfrontPaymentConstitutedEntireConsiderationIncludedInTransactionPrice_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Determined upfront payment constituted entire consideration included in transaction price</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="atra_LeasesDisclosureTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Leases</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="atra_LeasesDisclosureTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Leases Disclosure [Text Block</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="atra_LeasesDisclosureTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Leases disclosure.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_PaymentsForRestructuring_lbl" xlink:role="http://www.xbrl.org/2009/role/negatedLabel">Cash payments</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_PaymentsForRestructuring_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Payments for Restructuring</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_PaymentsForRestructuring_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Cash payments restructuring</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_GainLossOnInvestments_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Gain (Loss) on Investments</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_GainLossOnInvestments_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel">Gain (Loss) on Investments, Total</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_GainLossOnInvestments_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Gain (Loss) on Investments,</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriod_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Share-Based Compensation Arrangement by Share-Based Payment Award, Equity Instruments Other than Options, Grants in Period</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriod_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Shares, Granted</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="atra_AccruedTerminationCharges_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Accrued termination charges.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="atra_AccruedTerminationCharges_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Accrued Termination Charges</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="atra_AccruedTerminationCharges_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Accrued termination charges</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_Assets_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Assets</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_Assets_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel">Total assets</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ScheduleOfPropertyPlantAndEquipmentTable_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Property, Plant and Equipment [Table]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ScheduleOfPropertyPlantAndEquipmentTable_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Schedule Of Property Plant And Equipment [Table]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsExercisableWeightedAverageRemainingContractualTerm1_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Share-Based Compensation Arrangement by Share-Based Payment Award, Options, Exercisable, Weighted Average Remaining Contractual Term</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsExercisableWeightedAverageRemainingContractualTerm1_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Exercisable, Weighted Average Remaining Contractual Term</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_IncomeStatementAbstract_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Income Statement [Abstract]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ScheduleOfRestructuringAndRelatedCostsTable_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Restructuring Cost [Table]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="atra_GrossProceedsFromSale_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Gross proceeds from sale</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="atra_GrossProceedsFromSale_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Gross Proceeds From Sale</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="atra_GrossProceedsFromSale_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Gross Proceeds From Sale</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_FinanceLeaseInterestPaymentOnLiability_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Operating cash flows for finance leases</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_FinanceLeaseInterestPaymentOnLiability_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Finance Lease, Interest Payment on Liability</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="atra_AccruedExpenseRestructuring_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Accrued expense restructuring</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="atra_AccruedExpenseRestructuring_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Accrued expense restructuring</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="atra_AccruedExpenseRestructuring_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Accrued expense restructuring</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="atra_IssuanceOfPreFundedWarrantsInConnectionWithADebtModification_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Issuance of Pre Funded Warrants in Connection With a Debt Modification</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="atra_IssuanceOfPreFundedWarrantsInConnectionWithADebtModification_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Issuance of Pre Funded Warrants in Connection With a Debt Modification</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="atra_IssuanceOfPreFundedWarrantsInConnectionWithADebtModification_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Issuance of pre-funded warrants in connection with HCRx Amendment</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="atra_AdditionalUpfrontPaymentIncludedIntransactionPrice_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Additional Upfront Payment Included inTransaction Price</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="atra_AdditionalUpfrontPaymentIncludedIntransactionPrice_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Additional Upfront Payment Included inTransaction Price</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="atra_AdditionalUpfrontPaymentIncludedIntransactionPrice_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Additional Upfront Payment Included inTransaction Price</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_StockIssuedDuringPeriodSharesNewIssues_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Stock Issued During Period, Shares, New Issues</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_StockIssuedDuringPeriodSharesNewIssues_lbl" xlink:role="http://www.xbrl.org/2003/role/verboseLabel">Common stock, shares issued</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriod_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Share-Based Compensation Arrangement by Share-Based Payment Award, Equity Instruments Other than Options, Vested in Period</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriod_lbl" xlink:role="http://www.xbrl.org/2009/role/negatedLabel">Shares, Vested</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="atra_WriteOffOfAccruedInterestReceivable_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Write off of accrued interest receivable.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="atra_WriteOffOfAccruedInterestReceivable_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Write Off Of Accrued Interest Receivable</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="atra_WriteOffOfAccruedInterestReceivable_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Write off, of accrued interest receivable</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_EarningsPerShareDiluted_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Earnings Per Share, Diluted</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_EarningsPerShareDiluted_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel">Earnings Per Share, Diluted, Total</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_EarningsPerShareDiluted_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Diluted (loss) earnings per common share</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DeferredIncomeAddition_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Additions</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DeferredIncomeAddition_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Deferred Income, Addition</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DeferredIncomeAddition_lbl" xlink:role="http://www.xbrl.org/2009/role/negatedTerseLabel">Additions</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="dei_CityAreaCode_lbl" xlink:role="http://www.xbrl.org/2003/role/label">City Area Code</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="dei_CityAreaCode_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">City Area Code</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="atra_IncreaseDecreaseInOperatingLeaseLiabilities_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Increase (decrease) in operating lease liabilities.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="atra_IncreaseDecreaseInOperatingLeaseLiabilities_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Increase Decrease In Operating Lease Liabilities</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="atra_IncreaseDecreaseInOperatingLeaseLiabilities_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Operating lease liabilities</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="atra_IncreaseDecreaseInOperatingLeaseLiabilities_lbl" xlink:role="http://www.xbrl.org/2009/role/negatedLabel">Operating lease liabilities</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="atra_TwoThousandFourteenEquityIncentivePlanAndInducementPlanMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">2014 EIP and Inducement Plan.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="atra_TwoThousandFourteenEquityIncentivePlanAndInducementPlanMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Two Thousand Fourteen Equity Incentive Plan And Inducement Plan [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="atra_TwoThousandFourteenEquityIncentivePlanAndInducementPlanMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">2014 EIP and Inducement Plan</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="srt_RepurchaseAgreementCounterpartyNameDomain_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Counterparty Name</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="srt_RepurchaseAgreementCounterpartyNameDomain_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Counterparty Name [Domain]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="atra_CashEquivalentsAccumulatedGrossUnrealizedLossBeforeTax_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Cash equivalents, accumulated gross unrealized loss, before tax.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="atra_CashEquivalentsAccumulatedGrossUnrealizedLossBeforeTax_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Cash Equivalents Accumulated Gross Unrealized Loss Before Tax</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="atra_CashEquivalentsAccumulatedGrossUnrealizedLossBeforeTax_lbl" xlink:role="http://www.xbrl.org/2009/role/negatedLabel">Total Unrealized Loss</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="atra_CashEquivalentsAccumulatedGrossUnrealizedLossBeforeTax_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Total Unrealized Loss</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="atra_ProceedsFromSaleOfPreFundedWarrantsToPurchaseCommonStockInARegisteredDirectOfferingNet_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Proceeds from Sale of Pre-funded Warrants to Purchase Common Stock in a Registered Direct Offering, Net</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="atra_ProceedsFromSaleOfPreFundedWarrantsToPurchaseCommonStockInARegisteredDirectOfferingNet_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Proceeds from sale of pre-funded warrants to purchase common stock in a registered direct offering, net.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="atra_ProceedsFromSaleOfPreFundedWarrantsToPurchaseCommonStockInARegisteredDirectOfferingNet_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Proceeds from sale of pre-funded warrants to purchase common stock in an underwritten registered direct offering or registered direct offering, net</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_OperatingLeaseWeightedAverageRemainingLeaseTerm1_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Operating leases</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_OperatingLeaseWeightedAverageRemainingLeaseTerm1_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Operating Lease, Weighted Average Remaining Lease Term</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_LeaseExpirationDate1_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Lease expiration date</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_LeaseExpirationDate1_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Lease Expiration Date</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_PrepaidRoyalties_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Liability related to sale of future royalties</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_PrepaidRoyalties_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Prepaid Royalties</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_PrepaidRoyalties_lbl" xlink:role="http://www.xbrl.org/2003/role/periodStartLabel">Liability related to sale of future revenues as of January 1, 2024</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_PrepaidRoyalties_lbl" xlink:role="http://www.xbrl.org/2003/role/periodEndLabel">Liability related to sale of future revenues as of March 31, 2024</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="atra_Financeleasecostsabstract_lbl" xlink:role="http://www.xbrl.org/2003/role/label">FinanceLeaseCostsAbstract</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="atra_Financeleasecostsabstract_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">FinanceLeaseCostsAbstract</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="atra_Financeleasecostsabstract_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Finance lease cost:</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_LetterOfCreditMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Line of credit</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_LetterOfCreditMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Letter of Credit [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_PropertyPlantAndEquipmentNet_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Property, Plant and Equipment, Net</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_PropertyPlantAndEquipmentNet_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Property and equipment, net</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_PropertyPlantAndEquipmentNet_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel">Property and equipment, net</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_PropertyPlantAndEquipmentNet_lbl" xlink:role="http://www.xbrl.org/2003/role/periodStartLabel">Property, Plant and Equipment, Net, Beginning Balance</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_PropertyPlantAndEquipmentNet_lbl" xlink:role="http://www.xbrl.org/2003/role/periodEndLabel">Property, Plant and Equipment, Net, Ending Balance</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_RightOfUseAssetObtainedInExchangeForFinanceLeaseLiability_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Operating lease assets obtained in exchange for lease obligations</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_RightOfUseAssetObtainedInExchangeForFinanceLeaseLiability_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Right-of-Use Asset Obtained in Exchange for Finance Lease Liability</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="atra_Summaryofotherinformationrelatedtoleasestabletextblock_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Summary of Other Information Related to Leases</link:label>
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          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="atra_Summaryofotherinformationrelatedtoleasestabletextblock_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">SummaryOfOtherInformationRelatedToLeasesTableTextBlock</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="atra_Lesseeoperatingleasepercentageofannualincreaseinbaserent_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Percentage of annual increase in base rent</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="atra_Lesseeoperatingleasepercentageofannualincreaseinbaserent_lbl" xlink:role="http://www.xbrl.org/2003/role/label">LesseeOperatingLeasePercentageOfAnnualIncreaseInBaseRent</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="atra_Lesseeoperatingleasepercentageofannualincreaseinbaserent_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">LesseeOperatingLeasePercentageOfAnnualIncreaseInBaseRent</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_OperatingIncomeLoss_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Operating Income (Loss)</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_OperatingIncomeLoss_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel">Income (loss) from operations</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_RetainedEarningsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Retained Earnings [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_RetainedEarningsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Accumulated Deficit</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ShareBasedCompensation_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Share-Based Payment Arrangement, Noncash Expense</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ShareBasedCompensation_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Stock-based compensation expense</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ShareBasedCompensation_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel">Share-based Payment Arrangement, Noncash Expense, Total</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="atra_TwoThousandAndTwentyFourEquityIncentivePlanMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">2024 Equity Incentive Plan</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="atra_TwoThousandAndTwentyFourEquityIncentivePlanMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Two Thousand And Twenty Four Equity Incentive Plan [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="atra_TwoThousandAndTwentyFourEquityIncentivePlanMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Two Thousand And Twenty Four Equity Incentive Plan [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="atra_NetAssetsSold_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel">Net assets sold, Total</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="atra_NetAssetsSold_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Net assets sold</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="atra_NetAssetsSold_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Net assets sold</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="atra_IssuanceOfCommonStockPursuantToEmployeeStockAwardsShares_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Issuance of common stock pursuant to employee stock awards shares.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="atra_IssuanceOfCommonStockPursuantToEmployeeStockAwardsShares_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Issuance Of Common Stock Pursuant To Employee Stock Awards Shares</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="atra_IssuanceOfCommonStockPursuantToEmployeeStockAwardsShares_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Issuance of common stock pursuant to employee stock awards, shares</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_OperatingLeaseWeightedAverageDiscountRatePercent_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Operating leases</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_OperatingLeaseWeightedAverageDiscountRatePercent_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Operating Lease, Weighted Average Discount Rate, Percent</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="atra_SeveranceAndRelatedBenefitsCosts_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Severance and related benefits costs</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="atra_SeveranceAndRelatedBenefitsCosts_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Severance And Related Benefits Costs</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="atra_SeveranceAndRelatedBenefitsCosts_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Severance And Related Benefits Costs</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_OperatingLeaseLiabilityNoncurrent_lbl" xlink:role="http://www.xbrl.org/2003/role/verboseLabel">Operating lease liabilities - long-term</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_OperatingLeaseLiabilityNoncurrent_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Operating Lease, Liability, Noncurrent</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_OperatingLeaseLiabilityNoncurrent_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Operating lease liabilities - long-term</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_FairValueInputsLevel1Member_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Level 1</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_FairValueInputsLevel1Member_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Fair Value, Inputs, Level 1 [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ClassOfStockLineItems_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Class of Stock [Line Items]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ClassOfStockLineItems_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Class Of Stock [Line Items]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_NetCashProvidedByUsedInFinancingActivities_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Cash Provided by (Used in) Financing Activity, Including Discontinued Operation</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_NetCashProvidedByUsedInFinancingActivities_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel">Net cash provided by financing activities</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_LeaseCostTableTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Components of Lease Cost</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_LeaseCostTableTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Lease, Cost [Table Text Block]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="atra_HcrxAgreementMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">HCRx Agreement [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="atra_HcrxAgreementMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">HCRx Agreement [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="atra_HcrxAgreementMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">HCRx Agreement [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="atra_InterestRateOfRoyaltiesPercentage_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Interest rate of royalties, percentage</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="atra_InterestRateOfRoyaltiesPercentage_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Interest Rate of Royalties, percentage</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="atra_InterestRateOfRoyaltiesPercentage_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Interest rate of royalties, percentage</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="atra_SupplementalBalanceSheetInformationAbstract_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Supplemental Balance Sheet Information [Abstract]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="atra_SupplementalBalanceSheetInformationAbstract_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Supplemental Balance Sheet Information [Abstract]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="atra_FujifilmMasterServicesAndSupplyAgreementMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Fujifilm master services and supply agreement.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="atra_FujifilmMasterServicesAndSupplyAgreementMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Fujifilm Master Services And Supply Agreement [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="atra_FujifilmMasterServicesAndSupplyAgreementMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Fujifilm Master Services and Supply Agreement</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsLineItems_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ScheduleOfAntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Schedule of Antidilutive Securities Excluded from Computation of Earnings Per Share [Table Text Block]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ScheduleOfAntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Antidilutive Securities Excluded From Computation of Diluted Net Loss per Common Share</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_CorporateDebtSecuritiesMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Corporate Debt Securities [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_CorporateDebtSecuritiesMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Corporate Debt Obligations</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DebtSecuritiesAvailableForSaleTable_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Debt Securities, Available-for-Sale [Table]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="dei_EntityInteractiveDataCurrent_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Entity Interactive Data Current</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="dei_EntityInteractiveDataCurrent_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Entity Interactive Data Current</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_IncomeStatementLocationDomain_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Statement of Income Location, Balance [Domain]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_IncomeStatementLocationDomain_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Income Statement Location</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_NetCashProvidedByUsedInOperatingActivitiesAbstract_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Cash Provided by (Used in) Operating Activity, Including Discontinued Operation [Abstract]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_NetCashProvidedByUsedInOperatingActivitiesAbstract_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Operating activities</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_FurnitureAndFixturesMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Furniture and Fixtures [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_FurnitureAndFixturesMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Furniture and Fixtures [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="atra_TwoThousandTwentyThreeATMFacilityMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Two Thousand Twenty Three ATM Facility [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="atra_TwoThousandTwentyThreeATMFacilityMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Two Thousand Twenty Three ATM Facility [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="atra_TwoThousandTwentyThreeATMFacilityMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">2023 ATM [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_IncreaseDecreaseInOtherNoncurrentLiabilities_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Increase (Decrease) in Other Noncurrent Liabilities</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_IncreaseDecreaseInOtherNoncurrentLiabilities_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Other long-term liabilities</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_PaymentsToAcquireLeaseReceivables_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Payments to acquire lease receivables</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_PaymentsToAcquireLeaseReceivables_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Payments to Acquire Lease Receivables</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_PaymentsToAcquireLeaseReceivables_lbl" xlink:role="http://www.xbrl.org/2003/role/verboseLabel">Investment amount</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="atra_MinimumPurchaseCommitmentsAccrued_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Minimum purchase commitments accrued</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="atra_MinimumPurchaseCommitmentsAccrued_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Minimum purchase commitments accrued</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="atra_MinimumPurchaseCommitmentsAccrued_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Minimum purchase commitments accrued</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="dei_EntityTaxIdentificationNumber_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Entity Tax Identification Number</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="dei_EntityTaxIdentificationNumber_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Entity Tax Identification Number</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_AvailableForSaleSecuritiesDebtMaturitiesSingleMaturityDateAmortizedCostBasisAbstract_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Debt Securities, Available-for-Sale, Maturity, Allocated and Single Maturity Date, Amortized Cost [Abstract]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_AvailableForSaleSecuritiesDebtMaturitiesSingleMaturityDateAmortizedCostBasisAbstract_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Amortized cost</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="atra_LiabilityRelatedToTheSalesOfFutureRevenuesTableTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Liability Related To The Sales Of Future Revenues Table Text Block</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="atra_LiabilityRelatedToTheSalesOfFutureRevenuesTableTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Liability Related To The Sales Of Future Revenues Table Text Block</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="atra_LiabilityRelatedToTheSalesOfFutureRevenuesTableTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Schedule of Liability Related to the Sale of Future Revenues</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="atra_EmployeeStockPurchasePlanMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Employee stock purchase plan.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="atra_EmployeeStockPurchasePlanMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Employee Stock Purchase Plan [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="atra_EmployeeStockPurchasePlanMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">ESPP Share Purchase Rights</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="atra_MinimumCommitmentsExpense_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Minimum commitments Expense</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="atra_MinimumCommitmentsExpense_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Minimum commitments Expense</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="atra_MinimumCommitmentsExpense_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Minimum commitments Expense</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ProceedsFromIssuanceOrSaleOfEquity_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Issuance and sale of shares of common stock for total proceeds</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ProceedsFromIssuanceOrSaleOfEquity_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Proceeds from Issuance or Sale of Equity</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ProceedsFromIssuanceOrSaleOfEquity_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel">Proceeds from Issuance or Sale of Equity, Total</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="dei_LocalPhoneNumber_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Local Phone Number</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="dei_LocalPhoneNumber_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Local Phone Number</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="atra_TerritoryDomain_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Territory [Domain]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="atra_TerritoryDomain_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Territory [Domain]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_OtherLiabilitiesCurrent_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel">Total other current liabilities</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_OtherLiabilitiesCurrent_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Other Liabilities, Current</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_OtherLiabilitiesCurrent_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Other current liabilities</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognizedStockOptions_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Share-Based Payment Arrangement, Nonvested Award, Option, Cost Not yet Recognized, Amount</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognizedStockOptions_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Unrecognized stock-based compensation</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ShortTermLeaseCost_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Short-term lease cost</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ShortTermLeaseCost_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Short-Term Lease, Cost</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_FinanceLeaseLiabilityPaymentsDueYearTwo_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Finance Lease, Liability, to be Paid, Year Two</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_FinanceLeaseLiabilityPaymentsDueYearTwo_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Finance leases, 2026</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="atra_MilestoneTypeNameDomain_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Milestone Type, Name [Domain]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="atra_MilestoneTypeNameDomain_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Milestone Type, Name [Domain]</link:label>
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  <xsd:element id="atra_LeaseCommencementDate" name="LeaseCommencementDate" type="xbrli:dateItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false"/>
  <xsd:element id="atra_Financeleasecostsabstract" name="Financeleasecostsabstract" type="xbrli:stringItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="atra_GrossProceedsFromSale" name="GrossProceedsFromSale" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false" xbrli:balance="debit"/>
  <xsd:element id="atra_EmployeesAndNonEmployeesMember" name="EmployeesAndNonEmployeesMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="atra_DevelopmentOrSalesBasedMilestonePaymentsEarnedOrReceived" name="DevelopmentOrSalesBasedMilestonePaymentsEarnedOrReceived" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false" xbrli:balance="debit"/>
  <xsd:element id="atra_HCRxRoyaltiesMember" name="HCRxRoyaltiesMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="atra_RestructuringLabialityActivityTableTextBlock" name="RestructuringLabialityActivityTableTextBlock" type="dtr-types:textBlockItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false"/>
  <xsd:element id="atra_NumberOfTransacationCost" name="NumberOfTransacationCost" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false" xbrli:balance="debit"/>
  <xsd:element id="atra_Incrementalcontractualobligationsunderleaseamendment" name="Incrementalcontractualobligationsunderleaseamendment" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false" xbrli:balance="credit"/>
  <xsd:element id="atra_September2024Pre-FundedWarrantsMember" name="September2024Pre-FundedWarrantsMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="atra_CashEquivalentsAccumulatedGrossUnrealizedLossBeforeTax" name="CashEquivalentsAccumulatedGrossUnrealizedLossBeforeTax" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="instant" nillable="true" abstract="false" xbrli:balance="debit"/>
  <xsd:element id="atra_OperatingLeaseRight-Of-UseAssetAcceleratedAmortizationExpense" name="OperatingLeaseRight-Of-UseAssetAcceleratedAmortizationExpense" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false" xbrli:balance="debit"/>
  <xsd:element id="atra_FujifilmMasterServicesAndSupplyAgreementMember" name="FujifilmMasterServicesAndSupplyAgreementMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="atra_InducementPlanMember" name="InducementPlanMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="atra_PercentageOfCommissionToBePaidOnGrossSalesProceedsOfCommonStockSold" name="PercentageOfCommissionToBePaidOnGrossSalesProceedsOfCommonStockSold" type="dtr-types:percentItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false"/>
  <xsd:element id="atra_SubLicensingFees" name="SubLicensingFees" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false" xbrli:balance="debit"/>
  <xsd:element id="atra_Weightedaveragediscountrateabstract" name="Weightedaveragediscountrateabstract" type="xbrli:stringItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="atra_TwoThousandNineteenWarrantsMember" name="TwoThousandNineteenWarrantsMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="atra_MinimumCashRepayment" name="MinimumCashRepayment" type="dtr-types:percentItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false"/>
  <xsd:element id="atra_SupplementalBalanceSheetInformationTable" name="SupplementalBalanceSheetInformationTable" type="xbrli:stringItemType" substitutionGroup="xbrldt:hypercubeItem" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="atra_InterestRateOfRoyaltiesPercentage" name="InterestRateOfRoyaltiesPercentage" type="dtr-types:percentItemType" substitutionGroup="xbrli:item" xbrli:periodType="instant" nillable="true" abstract="false"/>
  <xsd:element id="atra_IssuanceOfCommonStockNetOfCommissionsAndOfferingCostsShares" name="IssuanceOfCommonStockNetOfCommissionsAndOfferingCostsShares" type="xbrli:sharesItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false"/>
  <xsd:element id="atra_Non-CashImpairmentOfLeaseRight-Of-UseAsset" name="Non-CashImpairmentOfLeaseRight-Of-UseAsset" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false" xbrli:balance="debit"/>
  <xsd:element id="atra_ProceedsFromTransactionCost" name="ProceedsFromTransactionCost" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false" xbrli:balance="credit"/>
  <xsd:element id="atra_IssuanceOfCommonStockNetOfCommissionsAndOfferingCostsValue" name="IssuanceOfCommonStockNetOfCommissionsAndOfferingCostsValue" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false" xbrli:balance="credit"/>
  <xsd:element id="atra_AggregateOfferingPriceOfCommonStock" name="AggregateOfferingPriceOfCommonStock" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="instant" nillable="true" abstract="false" xbrli:balance="debit"/>
  <xsd:element id="atra_MedicalAndSafetyExpense" name="MedicalAndSafetyExpense" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false" xbrli:balance="debit"/>
  <xsd:element id="atra_ScheduleOfLicenseCollaborationAndManufacturingAgreementsTable" name="ScheduleOfLicenseCollaborationAndManufacturingAgreementsTable" type="xbrli:stringItemType" substitutionGroup="xbrldt:hypercubeItem" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="atra_CommercializationRevenue" name="CommercializationRevenue" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false" xbrli:balance="credit"/>
  <xsd:element id="atra_AdditionalUpfrontPaymentIncludedIntransactionPrice" name="AdditionalUpfrontPaymentIncludedIntransactionPrice" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="instant" nillable="true" abstract="false" xbrli:balance="debit"/>
  <xsd:element id="atra_UnderwrittenPublicOfferingMember" name="UnderwrittenPublicOfferingMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="atra_CashEquivalentsFairValue" name="CashEquivalentsFairValue" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="instant" nillable="true" abstract="false" xbrli:balance="debit"/>
  <xsd:element id="atra_Leaseagreementareaofofficelabandmanufacturingspace" name="Leaseagreementareaofofficelabandmanufacturingspace" type="dtr-types:areaItemType" substitutionGroup="xbrli:item" xbrli:periodType="instant" nillable="true" abstract="false"/>
  <xsd:element id="atra_HcrxAgreementMember" name="HcrxAgreementMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="atra_WarrantMaximumOwnershipMember" name="WarrantMaximumOwnershipMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="atra_Financeleasecost" name="Financeleasecost" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false" xbrli:balance="debit"/>
  <xsd:element id="atra_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOptionsAndRestrictedStockUnitsOutstanding" name="ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOptionsAndRestrictedStockUnitsOutstanding" type="xbrli:sharesItemType" substitutionGroup="xbrli:item" xbrli:periodType="instant" nillable="true" abstract="false"/>
  <xsd:element id="atra_AdditionalMilestonePayments" name="AdditionalMilestonePayments" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false" xbrli:balance="debit"/>
  <xsd:element id="atra_EmployeesCount" name="EmployeesCount" type="xbrli:integerItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false"/>
  <xsd:element id="atra_LiabilityRelatedToTheSaleOfFutureRoyalties" name="LiabilityRelatedToTheSaleOfFutureRoyalties" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="instant" nillable="true" abstract="false" xbrli:balance="credit"/>
  <xsd:element id="atra_RecordedUnconditionalServiceObligationsTextBlock" name="RecordedUnconditionalServiceObligationsTextBlock" type="dtr-types:textBlockItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false"/>
  <xsd:element id="atra_ScheduleOfInformationProvidedToCODMTableTextBlock" name="ScheduleOfInformationProvidedToCODMTableTextBlock" type="dtr-types:textBlockItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false"/>
  <xsd:element id="atra_NonCashInvestingAndFinancingActivitiesAccruedCostsRelatedToAtTheMarketFacility" name="NonCashInvestingAndFinancingActivitiesAccruedCostsRelatedToAtTheMarketFacility" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false" xbrli:balance="debit"/>
  <xsd:element id="atra_LiabilityRelatedToTheSaleOfFutureRoyaltiesLongTerm" name="LiabilityRelatedToTheSaleOfFutureRoyaltiesLongTerm" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="instant" nillable="true" abstract="false" xbrli:balance="credit"/>
  <xsd:element id="atra_EmbeddedLeasesMember" name="EmbeddedLeasesMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="atra_ContractualObligationsDueToLicensors" name="ContractualObligationsDueToLicensors" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="instant" nillable="true" abstract="false" xbrli:balance="credit"/>
  <xsd:element id="atra_GoingConcernPolicyTextblock" name="GoingConcernPolicyTextblock" type="dtr-types:textBlockItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false"/>
  <xsd:element id="atra_May2020WarrantsMember" name="May2020WarrantsMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="atra_NetAssetsSold" name="NetAssetsSold" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="instant" nillable="true" abstract="false" xbrli:balance="credit"/>
  <xsd:element id="atra_TerritoryAxis" name="TerritoryAxis" type="xbrli:stringItemType" substitutionGroup="xbrldt:dimensionItem" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="atra_ComputerEquipmentAndSoftwareMember" name="ComputerEquipmentAndSoftwareMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="atra_CashPayment" name="CashPayment" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="instant" nillable="true" abstract="false" xbrli:balance="debit"/>
  <xsd:element id="atra_CashEquivalentsAccumulatedGrossUnrealizedGainBeforeTax" name="CashEquivalentsAccumulatedGrossUnrealizedGainBeforeTax" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="instant" nillable="true" abstract="false" xbrli:balance="credit"/>
  <xsd:element id="atra_FromDateOfGrantMember" name="FromDateOfGrantMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="atra_LicenseCollaborationAndManufacturingAgreementsAbstract" name="LicenseCollaborationAndManufacturingAgreementsAbstract" type="xbrli:stringItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="atra_IncreaseDecreaseMilestonePayment" name="IncreaseDecreaseMilestonePayment" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false" xbrli:balance="credit"/>
  <xsd:element id="atra_IssuanceOfPreFundedWarrantsRegisteredDirectOfferingValue" name="IssuanceOfPreFundedWarrantsRegisteredDirectOfferingValue" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false" xbrli:balance="credit"/>
  <xsd:element id="atra_AccruedExpenseRestructuring" name="AccruedExpenseRestructuring" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="instant" nillable="true" abstract="false" xbrli:balance="credit"/>
  <xsd:element id="atra_TwoThousandAndTwentyFourEquityIncentivePlanMember" name="TwoThousandAndTwentyFourEquityIncentivePlanMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="atra_CommonStockValueRemainedAvailableToBeSold" name="CommonStockValueRemainedAvailableToBeSold" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="instant" nillable="true" abstract="false" xbrli:balance="credit"/>
  <xsd:element id="atra_NonCashInvestingAndFinancingActivitiesAccruedCostsRelatedToDirectRegisteredOffering" name="NonCashInvestingAndFinancingActivitiesAccruedCostsRelatedToDirectRegisteredOffering" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false" xbrli:balance="debit"/>
  <xsd:element id="atra_Cashpaidforamountsincludedinmeasurementofleaseliabilitiesabstract" name="Cashpaidforamountsincludedinmeasurementofleaseliabilitiesabstract" type="xbrli:stringItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="atra_IncreaseDecreaseInOperatingLeaseLiabilities" name="IncreaseDecreaseInOperatingLeaseLiabilities" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false" xbrli:balance="debit"/>
  <xsd:element id="atra_ProceedsFromIssuanceOfCommonStockGross" name="ProceedsFromIssuanceOfCommonStockGross" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false" xbrli:balance="debit"/>
  <xsd:element id="atra_TwoThousandFourteenEmployeeStockPurchasePlanMember" name="TwoThousandFourteenEmployeeStockPurchasePlanMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="atra_LeaseAgreementAreaOfOfficeLabAndWarehouseSpace" name="LeaseAgreementAreaOfOfficeLabAndWarehouseSpace" type="dtr-types:areaItemType" substitutionGroup="xbrli:item" xbrli:periodType="instant" nillable="true" abstract="false"/>
  <xsd:element id="atra_StockIssuedDuringPeriodSharesStockOptionsExercisedOfPreFundedWarrants" name="StockIssuedDuringPeriodSharesStockOptionsExercisedOfPreFundedWarrants" type="xbrli:sharesItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false"/>
  <xsd:element id="atra_AccruedResearchAndDevelopmentExpensesCurrent" name="AccruedResearchAndDevelopmentExpensesCurrent" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="instant" nillable="true" abstract="false" xbrli:balance="credit"/>
  <xsd:element id="atra_Non-CashSettlementsAdjustments" name="Non-CashSettlementsAdjustments" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false" xbrli:balance="credit"/>
  <xsd:element id="atra_OperatingLeaseCostIncludingShortTermLease" name="OperatingLeaseCostIncludingShortTermLease" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false" xbrli:balance="debit"/>
  <xsd:element id="atra_DecreaseIncreaseInOperatingLeaseAssetsAndLiabilitiesUponDerecognition" name="DecreaseIncreaseInOperatingLeaseAssetsAndLiabilitiesUponDerecognition" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false" xbrli:balance="credit"/>
  <xsd:element id="atra_PaymentExchangeReductionAmount" name="PaymentExchangeReductionAmount" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false" xbrli:balance="debit"/>
  <xsd:element id="atra_RegulatoryAndQualityExpense" name="RegulatoryAndQualityExpense" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false" xbrli:balance="debit"/>
  <xsd:element id="atra_LeasesDisclosureTextBlock" name="LeasesDisclosureTextBlock" type="dtr-types:textBlockItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false"/>
  <xsd:element id="atra_IssuanceOfCommonStockPursuantToEmployeeStockAwardsValue" name="IssuanceOfCommonStockPursuantToEmployeeStockAwardsValue" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false" xbrli:balance="credit"/>
  <xsd:element id="atra_MaximumCashRepayment" name="MaximumCashRepayment" type="dtr-types:percentItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false"/>
  <xsd:element id="atra_FinancialInstrumentsDisclosureAbstract" name="FinancialInstrumentsDisclosureAbstract" type="xbrli:stringItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="atra_TwoThousandEighteenInducementPlanMember" name="TwoThousandEighteenInducementPlanMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="atra_TwoThousandTwentyThreeATMFacilityMember" name="TwoThousandTwentyThreeATMFacilityMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="atra_DecreaseIncreaseInFinanceLeaseAssetsAndLiabilitiesUponDerecognition" name="DecreaseIncreaseInFinanceLeaseAssetsAndLiabilitiesUponDerecognition" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false" xbrli:balance="credit"/>
  <xsd:element id="atra_LeasePremisesTerminated" name="LeasePremisesTerminated" type="dtr-types:areaItemType" substitutionGroup="xbrli:item" xbrli:periodType="instant" nillable="true" abstract="false"/>
  <xsd:element id="atra_DescriptionOfBusinessAbstract" name="DescriptionOfBusinessAbstract" type="xbrli:stringItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="atra_RevenueRecognitionPerformanceObligation" name="RevenueRecognitionPerformanceObligation" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false" xbrli:balance="credit"/>
  <xsd:element id="atra_December2020WarrantsMember" name="December2020WarrantsMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="atra_EffectOfDilutiveSecuritiesShares" name="EffectOfDilutiveSecuritiesShares" type="xbrli:sharesItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false"/>
  <xsd:element id="atra_SupplementalBalanceSheetInformationAbstract" name="SupplementalBalanceSheetInformationAbstract" type="xbrli:stringItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="atra_IssuanceOfPreFundedWarrantsNetOfOfferingCosts" name="IssuanceOfPreFundedWarrantsNetOfOfferingCosts" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false" xbrli:balance="debit"/>
  <xsd:element id="atra_LicenseAndCollaborationRevenue" name="LicenseAndCollaborationRevenue" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false" xbrli:balance="credit"/>
  <xsd:element id="atra_MinimumCommitmentsExpense" name="MinimumCommitmentsExpense" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false" xbrli:balance="debit"/>
  <xsd:element id="atra_MaximumOwnershipPercentage" name="MaximumOwnershipPercentage" type="dtr-types:percentItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false"/>
  <xsd:element id="atra_ReceivableForEarlyContract" name="ReceivableForEarlyContract" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="instant" nillable="true" abstract="false" xbrli:balance="credit"/>
  <xsd:element id="atra_ReductionInCurrentWorkforcePercentage" name="ReductionInCurrentWorkforcePercentage" type="dtr-types:percentItemType" substitutionGroup="xbrli:item" xbrli:periodType="instant" nillable="true" abstract="false"/>
  <xsd:element id="atra_SummaryOfEstimatedFairValueAndRelatedValuationInputHierarchyOfAvailableForSaleSecuritiesTableTextBlock" name="SummaryOfEstimatedFairValueAndRelatedValuationInputHierarchyOfAvailableForSaleSecuritiesTableTextBlock" type="dtr-types:textBlockItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false"/>
  <xsd:element id="atra_WorkforceRetaining" name="WorkforceRetaining" type="dtr-types:percentItemType" substitutionGroup="xbrli:item" xbrli:periodType="instant" nillable="true" abstract="false"/>
  <xsd:element id="atra_CashReceived" name="CashReceived" type="dtr-types:percentItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false"/>
  <xsd:element id="atra_TwoThousandAndFourteenEquityIncentivePlanMember" name="TwoThousandAndFourteenEquityIncentivePlanMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="atra_AuroraColoradoMember" name="AuroraColoradoMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="atra_RegulatoryMilestone" name="RegulatoryMilestone" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="instant" nillable="true" abstract="false" xbrli:balance="credit"/>
  <xsd:element id="atra_MilestoneTypeNameDomain" name="MilestoneTypeNameDomain" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="atra_AdditionalTerritoryMember" name="AdditionalTerritoryMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="atra_Less" name="Less" type="xbrli:stringItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="atra_ReceivedTieredRoyaltiesOnNetSales" name="ReceivedTieredRoyaltiesOnNetSales" type="dtr-types:percentItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false"/>
  <xsd:element id="atra_SupplementalBalanceSheetInformationLineItems" name="SupplementalBalanceSheetInformationLineItems" type="xbrli:stringItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="atra_AllMilestonesMember" name="AllMilestonesMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="atra_ThousandOaksCaliforniaMember" name="ThousandOaksCaliforniaMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="atra_NonCashOperatingLeaseExpense" name="NonCashOperatingLeaseExpense" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false" xbrli:balance="debit"/>
  <xsd:element id="atra_LiabilityRelatedToTheSaleOfFutureRevenueCurrent" name="LiabilityRelatedToTheSaleOfFutureRevenueCurrent" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="instant" nillable="true" abstract="false" xbrli:balance="credit"/>
  <xsd:element id="atra_Scheduleofmaturitiesofleaseliabilitiesunderoperatingandfinanceleasestabletextblock" name="Scheduleofmaturitiesofleaseliabilitiesunderoperatingandfinanceleasestabletextblock" type="dtr-types:textBlockItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false"/>
  <xsd:element id="atra_RSUReleasesSharesDuringPeriod" name="RSUReleasesSharesDuringPeriod" type="xbrli:sharesItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false"/>
  <xsd:element id="atra_MsaMember" name="MsaMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="atra_OtherNonCashItemsNet" name="OtherNonCashItemsNet" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false" xbrli:balance="debit"/>
  <xsd:element id="atra_CommonStockAveragePrice" name="CommonStockAveragePrice" type="dtr-types:perShareItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false"/>
  <xsd:element id="atra_TwoThousandFourteenEquityIncentivePlanAndInducementPlanMember" name="TwoThousandFourteenEquityIncentivePlanAndInducementPlanMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="atra_LiabilityRelatedToTheSaleOfFutureRevenuesTextBlock" name="LiabilityRelatedToTheSaleOfFutureRevenuesTextBlock" type="dtr-types:textBlockItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false"/>
  <xsd:element id="atra_TotalOtherIncomeExpenseNet" name="TotalOtherIncomeExpenseNet" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false" xbrli:balance="credit"/>
  <xsd:element id="atra_Summaryofotherinformationrelatedtoleasestabletextblock" name="Summaryofotherinformationrelatedtoleasestabletextblock" type="dtr-types:textBlockItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false"/>
  <xsd:element id="atra_CashEquivalentsAmortizedCost" name="CashEquivalentsAmortizedCost" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="instant" nillable="true" abstract="false" xbrli:balance="debit"/>
  <xsd:element id="atra_RoyaltyEligibleToReceiveTermAfterFirstCommercialSale" name="RoyaltyEligibleToReceiveTermAfterFirstCommercialSale" type="xbrli:durationItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false"/>
  <xsd:element id="atra_ReconciliationOfShareAmountUsedInComputingEarningsPerShareTableTextBlock" name="ReconciliationOfShareAmountUsedInComputingEarningsPerShareTableTextBlock" type="dtr-types:textBlockItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false"/>
  <xsd:element id="atra_ReductionOfDebtInExchangeForPre-FundedWarrants" name="ReductionOfDebtInExchangeForPre-FundedWarrants" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false" xbrli:balance="credit"/>
  <xsd:element id="atra_LiquidityRiskPolicyTextBlock" name="LiquidityRiskPolicyTextBlock" type="dtr-types:textBlockItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false"/>
  <xsd:element id="atra_WriteOffOfAccruedInterestReceivable" name="WriteOffOfAccruedInterestReceivable" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false" xbrli:balance="debit"/>
  <xsd:element id="atra_BusinessDescriptionTextBlock" name="BusinessDescriptionTextBlock" type="dtr-types:textBlockItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false"/>
  <xsd:element id="atra_LiabilityRelatedToTheSalesOfFutureRevenuesTableTextBlock" name="LiabilityRelatedToTheSalesOfFutureRevenuesTableTextBlock" type="dtr-types:textBlockItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false"/>
  <xsd:element id="atra_CarryingValueOfAssetsSoldAndGainOnSaleTableTextBlock" name="CarryingValueOfAssetsSoldAndGainOnSaleTableTextBlock" type="dtr-types:textBlockItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false"/>
  <xsd:element id="atra_AtTheMarketOfferingMember" name="AtTheMarketOfferingMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="atra_JanuaryTwentyThousandTwentyFiveReductionMember" name="JanuaryTwentyThousandTwentyFiveReductionMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="atra_BayerManufacturingAgreementMember" name="BayerManufacturingAgreementMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="atra_Weightedaverageremainingleasetermabstract" name="Weightedaverageremainingleasetermabstract" type="xbrli:stringItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="atra_IssuanceOfPreFundedWarrantsInConnectionWithADebtModification" name="IssuanceOfPreFundedWarrantsInConnectionWithADebtModification" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false" xbrli:balance="debit"/>
  <xsd:element id="atra_LabEquipmentMember" name="LabEquipmentMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="atra_Lesseeoperatingleasepercentageofannualincreaseinbaserent" name="Lesseeoperatingleasepercentageofannualincreaseinbaserent" type="dtr-types:percentItemType" substitutionGroup="xbrli:item" xbrli:periodType="instant" nillable="true" abstract="false"/>
  <xsd:element id="atra_FinanceLeaseOtherLongTermLiabilities" name="FinanceLeaseOtherLongTermLiabilities" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="instant" nillable="true" abstract="false" xbrli:balance="credit"/>
  <xsd:element id="atra_AccruedTerminationCharges" name="AccruedTerminationCharges" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="instant" nillable="true" abstract="false" xbrli:balance="credit"/>
  <xsd:element id="atra_DirectRegisteredOfferingMember" name="DirectRegisteredOfferingMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="atra_EmployeeStockPurchasePlanMember" name="EmployeeStockPurchasePlanMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="atra_MilestoneTypeAxis" name="MilestoneTypeAxis" type="xbrli:stringItemType" substitutionGroup="xbrldt:dimensionItem" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="atra_Operatingleasecostabstract" name="Operatingleasecostabstract" type="xbrli:stringItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="atra_IncreaseDecreaseInAccruedResearchAndDevelopment" name="IncreaseDecreaseInAccruedResearchAndDevelopment" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false" xbrli:balance="debit"/>
  <xsd:element id="atra_RevenueRecognitionPerformanceSatisfiedOrPartiallySatisfiedPriorPeriod" name="RevenueRecognitionPerformanceSatisfiedOrPartiallySatisfiedPriorPeriod" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false" xbrli:balance="credit"/>
  <xsd:element id="atra_CostsIncurredRelatedtoPerformanceObligationsIncludedinRD" name="CostsIncurredRelatedtoPerformanceObligationsIncludedinRD" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false" xbrli:balance="credit"/>
  <xsd:element id="atra_WarrantsExercised" name="WarrantsExercised" type="xbrli:sharesItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false"/>
  <xsd:element id="atra_SupplyAgreementMaximumExtensionTerm" name="SupplyAgreementMaximumExtensionTerm" type="xbrli:durationItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false"/>
  <xsd:element id="atra_AggregateMilestonePaymentsEntitleToReceiveUponAchievingCertainRegulatoryAndCommercialMilestones" name="AggregateMilestonePaymentsEntitleToReceiveUponAchievingCertainRegulatoryAndCommercialMilestones" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="instant" nillable="true" abstract="false" xbrli:balance="debit"/>
  <xsd:element id="atra_IssuanceOfPreFundedWarrantsRegisteredDirectOfferingShares" name="IssuanceOfPreFundedWarrantsRegisteredDirectOfferingShares" type="xbrli:sharesItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false"/>
  <xsd:element id="atra_OfficeSpaceMember" name="OfficeSpaceMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="atra_CommonStockCapitalAdditionalSharesReservedForFutureIssuance" name="CommonStockCapitalAdditionalSharesReservedForFutureIssuance" type="xbrli:sharesItemType" substitutionGroup="xbrli:item" xbrli:periodType="instant" nillable="true" abstract="false"/>
  <xsd:element id="atra_ClassOfWarrantOrRightNumberOfWarrantsIssued" name="ClassOfWarrantOrRightNumberOfWarrantsIssued" type="xbrli:sharesItemType" substitutionGroup="xbrli:item" xbrli:periodType="instant" nillable="true" abstract="false"/>
  <xsd:element id="atra_ProceedsFromSaleOfFutureRoyaltiesGross" name="ProceedsFromSaleOfFutureRoyaltiesGross" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false" xbrli:balance="debit"/>
  <xsd:element id="atra_ClassOfWarrantOrRightTerm" name="ClassOfWarrantOrRightTerm" type="xbrli:durationItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false"/>
  <xsd:element id="atra_EquityWarrantsAsACharge" name="EquityWarrantsAsACharge" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="instant" nillable="true" abstract="false" xbrli:balance="debit"/>
  <xsd:element id="atra_CommercializationRevenueMember" name="CommercializationRevenueMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="atra_FreezersMember" name="FreezersMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="atra_PriorNoticePeriodToIncreaseOrDecreaseMaximumOwnershipPercentage" name="PriorNoticePeriodToIncreaseOrDecreaseMaximumOwnershipPercentage" type="xbrli:durationItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false"/>
  <xsd:element id="atra_PaymentsReceivedFromSaleOfInventory" name="PaymentsReceivedFromSaleOfInventory" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false" xbrli:balance="debit"/>
  <xsd:element id="atra_PierreFabreMember" name="PierreFabreMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="atra_LiabilitiesRelatedToIndemnificationAgreements" name="LiabilitiesRelatedToIndemnificationAgreements" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="instant" nillable="true" abstract="false" xbrli:balance="credit"/>
  <xsd:element id="atra_ProceedsFromSaleOfPreFundedWarrantsToPurchaseCommonStockInARegisteredDirectOfferingNet" name="ProceedsFromSaleOfPreFundedWarrantsToPurchaseCommonStockInARegisteredDirectOfferingNet" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false" xbrli:balance="debit"/>
  <xsd:element id="atra_January2024WarrantsMember" name="January2024WarrantsMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="atra_IssuanceOfCommonStockThroughATMFacilitiesNetOfCommissionsAndOfferingCostsValue" name="IssuanceOfCommonStockThroughATMFacilitiesNetOfCommissionsAndOfferingCostsValue" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false" xbrli:balance="debit"/>
  <xsd:element id="atra_OutLicenseAgreementsDisclosureTextBlock" name="OutLicenseAgreementsDisclosureTextBlock" type="dtr-types:textBlockItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false"/>
  <xsd:element id="atra_MaximumPotentialMilestonePayments" name="MaximumPotentialMilestonePayments" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false" xbrli:balance="debit"/>
  <xsd:element id="atra_SeveranceAndRelatedBenefitsCosts" name="SeveranceAndRelatedBenefitsCosts" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="instant" nillable="true" abstract="false" xbrli:balance="debit"/>
  <xsd:element id="atra_MinimumPurchaseCommitmentsAccrued" name="MinimumPurchaseCommitmentsAccrued" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="instant" nillable="true" abstract="false" xbrli:balance="credit"/>
  <xsd:element id="atra_UpfrontAndMilestonePayments" name="UpfrontAndMilestonePayments" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false" xbrli:balance="debit"/>
  <xsd:element id="atra_TerritoryDomain" name="TerritoryDomain" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="atra_ProcessingRoomsMember" name="ProcessingRoomsMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="atra_LicenseCollaborationAndManufacturingAgreementsLineItems" name="LicenseCollaborationAndManufacturingAgreementsLineItems" type="xbrli:stringItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="atra_ARCommercializationAgreementMember" name="ARCommercializationAgreementMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="atra_GainOnDerecognitionOfTheFinanceLeaseLiability" name="GainOnDerecognitionOfTheFinanceLeaseLiability" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false" xbrli:balance="credit"/>
  <xsd:element id="atra_ProceedsFromIssuanceOfCommonStockNet" name="ProceedsFromIssuanceOfCommonStockNet" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false" xbrli:balance="debit"/>
  <xsd:element id="atra_UpfrontCashPaymentReceived" name="UpfrontCashPaymentReceived" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false" xbrli:balance="credit"/>
  <xsd:element id="atra_PierreFabreCommercializationAgreementMember" name="PierreFabreCommercializationAgreementMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="atra_DeterminedUpfrontPaymentConstitutedEntireConsiderationIncludedInTransactionPrice" name="DeterminedUpfrontPaymentConstitutedEntireConsiderationIncludedInTransactionPrice" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false" xbrli:balance="credit"/>
  <xsd:element id="atra_IncreaseDecreaseInOtherCurrentAsset" name="IncreaseDecreaseInOtherCurrentAsset" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false" xbrli:balance="credit"/>
  <xsd:element id="atra_TechnicalOperationsAndQualityExpense" name="TechnicalOperationsAndQualityExpense" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false" xbrli:balance="debit"/>
  <xsd:element id="atra_GainOnDerecognitionOfTheOperatingLeaseLiability" name="GainOnDerecognitionOfTheOperatingLeaseLiability" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false" xbrli:balance="credit"/>
  <xsd:element id="atra_SouthSanFranciscoCaliforniaMember" name="SouthSanFranciscoCaliforniaMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="atra_MskLicenseAgreementsMember" name="MskLicenseAgreementsMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="atra_IssuanceOfCommonStockPursuantToEmployeeStockAwardsShares" name="IssuanceOfCommonStockPursuantToEmployeeStockAwardsShares" type="xbrli:sharesItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false"/>
  <xsd:element id="atra_NetOfTransactionCosts" name="NetOfTransactionCosts" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="instant" nillable="true" abstract="false" xbrli:balance="debit"/>
  <xsd:element id="atra_May2025Pre-FundedWarrantsMember" name="May2025Pre-FundedWarrantsMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="atra_MilestonePayments" name="MilestonePayments" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="instant" nillable="true" abstract="false" xbrli:balance="debit"/>
  <xsd:element id="atra_CowenAndCompanyLimitedLiabilityCompanyMember" name="CowenAndCompanyLimitedLiabilityCompanyMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="atra_Leaseoptiontoextendadditionalterm" name="Leaseoptiontoextendadditionalterm" type="xbrli:durationItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false"/>
  <xsd:element id="atra_CommonStockReservedForFutureIssuanceTableTextBlock" name="CommonStockReservedForFutureIssuanceTableTextBlock" type="dtr-types:textBlockItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false"/>
  <xsd:element id="atra_CommonStockReservedForFutureIssuanceValue" name="CommonStockReservedForFutureIssuanceValue" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="instant" nillable="true" abstract="false" xbrli:balance="debit"/>
</xsd:schema>
