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          <link:loc xlink:type="locator" xlink:href="bcab-20260331.xsd#bcab_AmendedLicenseAgreementFirstPayableAmount" xlink:label="bcab_AmendedLicenseAgreementFirstPayableAmount"/>
          <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"/>
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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_LesseeOperatingLeaseLiabilityPaymentsDueYearFour" xlink:label="us-gaap_LesseeOperatingLeaseLiabilityPaymentsDueYearFour"/>
          <link:loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd#us-gaap_CashAndCashEquivalentsMember" xlink:label="us-gaap_CashAndCashEquivalentsMember"/>
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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_DebtConversionDescription" xlink:label="us-gaap_DebtConversionDescription"/>
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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_ScheduleOfAccountsPayableAndAccruedLiabilitiesTableTextBlock" xlink:label="us-gaap_ScheduleOfAccountsPayableAndAccruedLiabilitiesTableTextBlock"/>
          <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="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="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_ScheduleOfCashFlowSupplementalDisclosuresTableTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Schedule of Cash Flow, Supplemental Disclosures [Table Text Block]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ScheduleOfCashFlowSupplementalDisclosuresTableTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Supplemental Cash Flow Information Related to Leases</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">Restructuring Reserve, 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">Restructuring Reserve, Beginning 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/totalLabel">Restructuring Reserve, Total</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="bcab_CollaborationLicenseAndOptionAgreementsAbstract_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Collaboration, license and option agreements.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="bcab_CollaborationLicenseAndOptionAgreementsAbstract_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Collaboration License And Option Agreements [Abstract]</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 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/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="us-gaap_PreferredStockSharesIssued_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel">Preferred Stock, Shares Issued, Total</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_PreferredStockSharesIssued_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Preferred Stock, Shares Issued</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_PreferredStockSharesIssued_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Preferred stock, shares issued (in shares)</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_PreferredStockSharesIssued_lbl" xlink:role="http://www.xbrl.org/2003/role/verboseLabel">Issuance of Series D convertible preferred stock for cash, net of $4,317 of issuance costs, Shares</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_OperatingLeasesFutureMinimumPaymentsRemainderOfFiscalYear_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Operating Leases, Future Minimum Payments, Remainder of Fiscal Year</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_OperatingLeasesFutureMinimumPaymentsRemainderOfFiscalYear_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">2021 (3 months)</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="us-gaap_EquityAbstract_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Equity [Abstract]</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="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_OperatingExpensesAbstract_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Operating expenses:</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 (in shares)</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/verboseLabel">Common stock authorized for issuance under plan</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_DebtInstrumentInterestRateStatedPercentage_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Debt Instrument, Interest Rate, Stated Percentage</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DebtInstrumentInterestRateStatedPercentage_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Interest rate</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_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="us-gaap_OtherAccruedLiabilitiesCurrent_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Other accrued expenses</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="bcab_ExclusiveLicenseAgreementAbstract_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Exclusive license agreement abstract.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="bcab_ExclusiveLicenseAgreementAbstract_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Exclusive License Agreement [Abstract]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="bcab_ConstructionInProcessMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Construction in process.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="bcab_ConstructionInProcessMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Construction In Process [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="bcab_ConstructionInProcessMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Construction In Process</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/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/periodEndLabel">Cash and cash equivalents, end of period</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, beginning of period</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="bcab_IssuanceOfCommonStockUnderPre-PaidAdvanceAgreementValue_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Issuance of Common Stock Under Pre-Paid Advance Agreement, Value</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="bcab_IssuanceOfCommonStockUnderPre-PaidAdvanceAgreementValue_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Issuance of Common Stock Under Pre-Paid Advance Agreement, Value</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="bcab_IssuanceOfCommonStockUnderPre-PaidAdvanceAgreementValue_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Issuance of common stock under PPAs, value</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ResearchAndDevelopmentArrangementContractToPerformForOthersByTypeAxis_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Research and Development Arrangement, Contract to Perform for Others, Type [Axis]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_StockIssuedDuringPeriodSharesConversionOfUnits_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Stock Issued During Period, Shares, Conversion of Units</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_StockIssuedDuringPeriodSharesConversionOfUnits_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Conversion of Class B common stock, shares</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="bcab_PlacementAgentFees_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Placement Agent Fees</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="bcab_PlacementAgentFees_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Placement Agent Fees</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="bcab_PlacementAgentFees_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Placement agent fees</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="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 (in shares)</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_FairValueAssetsMeasuredOnRecurringBasisUnobservableInputReconciliationByAssetClassDomain_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Asset Class [Domain]</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_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriodWeightedAverageGrantDateFairValue_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Share-Based Compensation Arrangement by Share-Based Payment Award, Options, Grants in Period, Weighted Average Grant Date Fair Value</link:label>
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          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="bcab_RestructuringChargesIncludedInAccountsPayableAndAccruedExpenses_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Restructuring Charges Included In Accounts Payable and Accrued Expenses</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="bcab_RestructuringChargesIncludedInAccountsPayableAndAccruedExpenses_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Restructuring Charges Included In Accounts Payable and Accrued Expenses</link:label>
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          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_InvestmentOwnedBalancePrincipalAmount_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Investment Owned, Balance, Principal Amount</link:label>
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          <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="us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardOptionsExpirationsInPeriodWeightedAverageExercisePrice_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Share-Based Compensation Arrangements by Share-Based Payment Award, Options, Expirations in Period, Weighted Average Exercise Price</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 [Member]</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="bcab_Pre-PaidAdvanceAgreementLiability_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Pre-Paid Advance Agreement Liability</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="bcab_Pre-PaidAdvanceAgreementLiability_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Pre-Paid Advance Agreement Liability</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="bcab_Pre-PaidAdvanceAgreementLiability_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">PPAs liability</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="bcab_Pre-PaidAdvanceAgreementLiability_lbl" xlink:role="http://www.xbrl.org/2003/role/periodStartLabel">PPAs Liability, Beginning Balance</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="bcab_Pre-PaidAdvanceAgreementLiability_lbl" xlink:role="http://www.xbrl.org/2003/role/periodEndLabel">PPAs Liability, Ending Balance</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_LiabilitiesAndStockholdersEquity_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel">Total liabilities and stockholders&#8217; equity</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DebtInstrumentLineItems_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Debt Instrument [Line Items]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DebtInstrumentLineItems_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Debt Instrument [Line Items]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="bcab_CommonSockWrantsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Common Stock Warrants</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="bcab_CommonSockWrantsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Common stock warrants.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="bcab_CommonSockWrantsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Common Sock Wrants [Member]</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 per Share</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="bcab_RestructuringCostsLineItems_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Restructuring Costs [Line Items]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="bcab_RestructuringCostsLineItems_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Restructuring Costs [Line Items]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="bcab_ScheduleOfTheChangesInTheFairValueOfLiabilitiesTableTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Schedule of the Changes in the Fair Value of liabilities</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="bcab_ScheduleOfTheChangesInTheFairValueOfLiabilitiesTableTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Schedule of the Changes in the Fair Value of liabilities [Table Text Block]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="bcab_ScheduleOfTheChangesInTheFairValueOfLiabilitiesTableTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Schedule of the Changes in the Fair Value of liabilities [Table 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/label">Restructuring and Related Costs [Table 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">Schedule of Changes in Restructuring Liability</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="bcab_ProceedsFromIssuanceOfCommonStockUnderStandByEquityPurchaseAgreementNet_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Proceeds From Issuance Of Common Stock Under Stand by Equity Purchase Agreement Net</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="bcab_ProceedsFromIssuanceOfCommonStockUnderStandByEquityPurchaseAgreementNet_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Proceeds From Issuance Of Common Stock Under Stand by Equity Purchase Agreement Net</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="bcab_ProceedsFromIssuanceOfCommonStockUnderStandByEquityPurchaseAgreementNet_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Proceeds from issuance of common stock under SEPA</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="bcab_NumberOfRsusUnvestedOnModificationDateNumberOfShares_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Number of RSUs unvested on modification date, number of shares</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="bcab_NumberOfRsusUnvestedOnModificationDateNumberOfShares_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Number Of RSUs Unvested On Modification Date, Number of shares</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="bcab_NumberOfRsusUnvestedOnModificationDateNumberOfShares_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Number Of RSUs Unvested On Modification Date, Number of shares</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_InvestmentIncomeInterest_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_InvestmentIncomeInterest_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Investment Income, Interest</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="bcab_ModificationOfTwoThousandTwentyEquityIncentivePlanAndCertainAwardsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Modification of Two Thousand Twenty Equity Incentive Plan and certain awards [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="bcab_ModificationOfTwoThousandTwentyEquityIncentivePlanAndCertainAwardsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Modification of Two Thousand Twenty Equity Incentive Plan and certain awards [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="bcab_ModificationOfTwoThousandTwentyEquityIncentivePlanAndCertainAwardsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Modification of Two Thousand Twenty Equity Incentive Plan and certain awards [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="bcab_EffectiveBusinessDays_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Effective Business Days</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="bcab_EffectiveBusinessDays_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Effective Business Days</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="bcab_EffectiveBusinessDays_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Effective Business Days</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="bcab_AccruedResearchAndDevelopmentIncludesRelatedPartyAmount_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Accrued Research And Development Includes Related Party Amount</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="bcab_AccruedResearchAndDevelopmentIncludesRelatedPartyAmount_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Accrued Research And Development Includes Related Party Amount</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="bcab_AccruedResearchAndDevelopmentIncludesRelatedPartyAmount_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Accrued research and development includes related party amounts</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="bcab_FurnitureFixturesAndOfficeEquipmentMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Furniture, fixtures and office equipment.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="bcab_FurnitureFixturesAndOfficeEquipmentMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Furniture Fixtures And Office Equipment [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="bcab_FurnitureFixturesAndOfficeEquipmentMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Furniture Fixtures And Office Equipment</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DerivativeAssetFairValueGrossLiability_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Derivative Asset, Subject to Master Netting Arrangement, Liability Offset</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DerivativeAssetFairValueGrossLiability_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Liability measured at fair value</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_RestrictedCashEquivalents_lbl" xlink:role="http://www.xbrl.org/2003/role/verboseLabel">Cash and Cash Equivalents</link:label>
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          <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, Number of Shares</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="bcab_TwoThousandTwentyPlanMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">2020 Plan [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="bcab_TwoThousandTwentyPlanMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Two Thousand Twenty Plan [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="bcab_TwoThousandTwentyPlanMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">2020 Plan [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="bcab_PercentageOfAverageDailyTradingVolume_lbl" xlink:role="http://www.xbrl.org/2003/role/label">percentage of average daily trading volume</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="bcab_PercentageOfAverageDailyTradingVolume_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">percentage of average daily trading volume</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="bcab_PercentageOfAverageDailyTradingVolume_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Percentage of average daily trading volume</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">Net loss per common share, basic</link:label>
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          <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_PensionAndOtherPostretirementBenefitsDisclosureTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Retirement Benefits [Text Block]</link:label>
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          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_LineOfCreditFacilityCovenantTerms_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Line of Credit Facility, Covenant Terms</link:label>
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          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="bcab_DebtInstrumentCarryingAmountPercentageOfFaceAmount_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Debt Instrument Carrying Amount Percentage Of Face Amount</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="bcab_DebtInstrumentCarryingAmountPercentageOfFaceAmount_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Debt Instrument Carrying Amount Percentage Of Face Amount</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="bcab_DebtInstrumentCarryingAmountPercentageOfFaceAmount_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Purchase price discount</link:label>
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          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingNumber_lbl" xlink:role="http://www.xbrl.org/2009/role/negatedTerseLabel">Stock Options Outstanding, Number of Shares</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/terseLabel">Stock Options Outstanding, Number of Shares</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/verboseLabel">Stock Options Outstanding, Number of Shares</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">Number of Shares, Ending Balance</link:label>
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          <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="bcab_AdjustmentOfWarrants_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Adjustment of warrants per share</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="bcab_AdjustmentOfWarrants_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Adjustment Of Warrants</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="bcab_AdjustmentOfWarrants_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Adjustment Of Warrants</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="bcab_StandbyEquityPurchaseAgreementFees_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Standby Equity Purchase Agreement Fees</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="bcab_StandbyEquityPurchaseAgreementFees_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Standby Equity Purchase Agreement Fees</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="bcab_StandbyEquityPurchaseAgreementFees_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Standby equity purchase agreement fees</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_PaymentsOfDebtIssuanceCosts_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Payments of Debt Issuance Costs</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_PaymentsOfDebtIssuanceCosts_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Issuance costs</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="bcab_AmendmentLicenseAgreementMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Amendment License Agreement [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="bcab_AmendmentLicenseAgreementMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Amendment License Agreement [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="bcab_AmendmentLicenseAgreementMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Amendment License Agreement [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_PaymentsToAcquireMachineryAndEquipment_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Payments to Acquire Machinery and Equipment</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_PaymentsToAcquireMachineryAndEquipment_lbl" xlink:role="http://www.xbrl.org/2009/role/negatedLabel">Purchases of property and equipment</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="srt_ConsolidationItemsDomain_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Consolidation Items [Domain]</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="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="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/periodEndLabel">Retained Earnings (Accumulated Deficit), Ending 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/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/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/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/2009/role/negatedLabel">Accumulated deficit</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="bcab_HimalayaTherapeuticsSEZCMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Himalaya therapeutics sezc member</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="bcab_HimalayaTherapeuticsSEZCMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Himalaya Therapeutics S E Z C [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="bcab_HimalayaTherapeuticsSEZCMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Himalaya Therapeutics SEZC</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="bcab_GainLossOnWarrantLiability_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Gain (Loss) On Warrant Liability</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="bcab_GainLossOnWarrantLiability_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Gain (Loss) On Warrant Liability</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="bcab_GainLossOnWarrantLiability_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Gain on warrant liability</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, Number of Shares</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/terseLabel">Forfeited, Number of Shares</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="bcab_FacilitiesAndOtherMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Facilities And Other [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="bcab_FacilitiesAndOtherMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Facilities And Other [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="bcab_FacilitiesAndOtherMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Facilities and other</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_SaleOfStockPricePerShare_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Common stock price</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_SaleOfStockPricePerShare_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Sale of Stock, Price Per Share</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="bcab_SharesAvailableForAwardsDescription_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Shares available for awards, description.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="bcab_SharesAvailableForAwardsDescription_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Shares Available For Awards Description</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="bcab_SharesAvailableForAwardsDescription_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Shares available for awards, description</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="bcab_AccruedSeveranceIncludedInAccountsPayableAndAccruedExpenses_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Accrued severance included in accounts payable and accrued expenses</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="bcab_AccruedSeveranceIncludedInAccountsPayableAndAccruedExpenses_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Accrued Severance Included in Accounts Payable and Accrued Expenses</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="bcab_AccruedSeveranceIncludedInAccountsPayableAndAccruedExpenses_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Accrued Severance Included in Accounts Payable and Accrued Expenses</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="bcab_ReductionInWorkforce_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Reduction in Workforce</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="bcab_ReductionInWorkforce_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Reduction in Workforce</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="bcab_ReductionInWorkforce_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Reduction in workforce</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="bcab_AmendedBeiGeneCollaborationMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Amended BeiGene Collaboration.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="bcab_AmendedBeiGeneCollaborationMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Amended Bei Gene Collaboration [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="bcab_AmendedBeiGeneCollaborationMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Amended BeiGene Collaboration</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="bcab_AmendedBeiGeneCollaborationMember_lbl" xlink:role="http://www.xbrl.org/2003/role/verboseLabel">BeiGene</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_ClassOfWarrantOrRightNumberOfSecuritiesCalledByWarrantsOrRights_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Purchase of common stock by warrants</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_OrganizationConsolidationBasisOfPresentationBusinessDescriptionAndAccountingPoliciesTextBlock_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_OrganizationConsolidationBasisOfPresentationBusinessDescriptionAndAccountingPoliciesTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Organization, Consolidation, Basis of Presentation, Business Description and Accounting Policies [Text Block]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_EarningsPerSharePolicyTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Earnings Per Share, Policy [Policy Text Block]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_EarningsPerSharePolicyTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Net Loss Per Share</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="us-gaap_LiabilitiesAndStockholdersEquityAbstract_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Liabilities and Stockholders&#8217; Equity</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="bcab_PartialConversionOfPrePaidAdvanceIntoCommonStock_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Partial Conversion of Pre Paid Advance into Common Stock</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="bcab_PartialConversionOfPrePaidAdvanceIntoCommonStock_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Partial Conversion of Pre Paid Advance into Common Stock</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="bcab_PartialConversionOfPrePaidAdvanceIntoCommonStock_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Conversion of Pre-Paid Advance into common stock</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_IncreaseDecreaseInOperatingLeaseLiability_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Increase (Decrease) in Operating Lease Liability</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_IncreaseDecreaseInOperatingLeaseLiability_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Right-of-use assets and lease liabilities, net</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="bcab_EmployeesStockPurchasePlanMember_lbl" xlink:role="http://www.xbrl.org/2003/role/verboseLabel">ESPP Shares</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="bcab_EmployeesStockPurchasePlanMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Employees stock purchase plan member.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="bcab_EmployeesStockPurchasePlanMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Employees Stock Purchase Plan [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="bcab_EmployeesStockPurchasePlanMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Employees Stock Purchase Plan [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="bcab_WarrantForThePurchaseOfCommonStock_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Warrant For The Purchase Of Common Stock</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="bcab_WarrantForThePurchaseOfCommonStock_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Warrant For The Purchase Of Common Stock</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="bcab_WarrantForThePurchaseOfCommonStock_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Warrants for the purchase of common stock</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="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 per Share</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">2028</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="bcab_IssuanceOfCommonStockUnderStandbyEquityPurchaseAgreementShares_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Issuance of Common Stock Under Standby Equity Purchase Agreement, Shares</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="bcab_IssuanceOfCommonStockUnderStandbyEquityPurchaseAgreementShares_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Issuance of Common Stock Under Standby Equity Purchase Agreement, Shares</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="bcab_IssuanceOfCommonStockUnderStandbyEquityPurchaseAgreementShares_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Issuance of common stock under SEPA, share</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/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_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/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_ResearchAndDevelopmentArrangementContractToPerformForOthersTypeDomain_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Research and Development Arrangement, Contract to Perform for Others, Type [Domain]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="bcab_LicenseTerminationInformationDescription_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">License termination information, Description</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="bcab_LicenseTerminationInformationDescription_lbl" xlink:role="http://www.xbrl.org/2003/role/label">License termination information, Description</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="bcab_LicenseTerminationInformationDescription_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">License termination information, Description</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>
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          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="bcab_EXUMAMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">EXUMA Member.</link:label>
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          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="dei_DocumentType_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">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/label">Document Type</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="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>
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          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="bcab_FairValueOfCommonStockRelatedToPre-PaidAdvanceAgreementLiabiliity_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Fair Value Of Common Stock Related To Pre-Paid Advance Agreement Liabiliity</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="bcab_FairValueOfCommonStockRelatedToPre-PaidAdvanceAgreementLiabiliity_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Fair value of common stock issued in satisfaction of PPAs liability</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>
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          <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>
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          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="bcab_LiquidityAndGoingConcernPolicyTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Liquidity and Going Concern.</link:label>
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          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="bcab_LiquidityAndGoingConcernPolicyTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Liquidity and Going Concern</link:label>
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          <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 (in dollars per share)</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="bcab_CompanyFormationDate_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Company formation date</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="bcab_CompanyFormationDate_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Company Formation Date</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="bcab_CompanyFormationDate_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Company formation date.</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 (years)</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/2003/role/terseLabel">Exercised, Number of Shares</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/verboseLabel">Issuance of common stock upon exercise of options, net, shares</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="bcab_RecalculatedCompensationCostOnTheModifiedRsus_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Recalculated compensation cost on the modified RSUs</link:label>
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          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="bcab_RecalculatedCompensationCostOnTheModifiedRsus_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Recalculated Compensation Cost On The Modified RSUs</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DebtDisclosureAbstract_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Debt Disclosure [Abstract]</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_DebtInstrumentTable_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Schedule of Long-Term Debt Instruments [Table]</link:label>
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          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="bcab_AmendedLicenseAgreementSecondPayableAmount_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Amended License Agreement Second Payable Amount</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="bcab_AmendedLicenseAgreementSecondPayableAmount_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Amended License Agreement Second Payable Amount</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>
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          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="bcab_OtherPrepaidExpensesAndCurrentAssets_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Other prepaid expenses and current assets.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="bcab_OtherPrepaidExpensesAndCurrentAssets_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Other Prepaid Expenses And Current Assets</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="bcab_OtherPrepaidExpensesAndCurrentAssets_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Other prepaid expenses and current assets</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="bcab_RestructuringCostsPolicyTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Restructuring Costs [Policy Text Block]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="bcab_RestructuringCostsPolicyTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Restructuring Costs [Policy Text Block]</link:label>
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          <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_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/periodEndLabel">Number of Outstanding Shares, Ending Balance</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">Number of Outstanding Shares, Beginning Balance</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_OperatingLeasesFutureMinimumPaymentsDueThereafter_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Operating Leases, Future Minimum Payments, Due Thereafter</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_OperatingLeasesFutureMinimumPaymentsDueThereafter_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Thereafter</link:label>
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          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="bcab_ScheduleOfTheChangeInTheFairValueOfPPAsLiabilitiesTableTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Schedule Of The Change In The Fair Value Of PPAs Liabilities [TableTextBlock]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="bcab_ScheduleOfTheChangeInTheFairValueOfPPAsLiabilitiesTableTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Schedule Of The Change In The Fair Value Of PPAs Liabilities [TableTextBlock]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="bcab_ScheduleOfTheChangeInTheFairValueOfPPAsLiabilitiesTableTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Schedule Of The Change In The Fair Value Of PPAs Liabilities</link:label>
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          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_OperatingLeasesFutureMinimumPaymentsDueInThreeYears_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">2024</link:label>
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          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_InterestAndOtherIncome_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Interest and Other Income</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_InterestAndOtherIncome_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Interest and other income/(expense)</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_StockOptionMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Equity Option [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_StockOptionMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Equity Option</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="us-gaap_DeferredRevenueCurrent_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel">Deferred Revenue, Current, Total</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DeferredRevenueCurrent_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Deferred Revenue, Current</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DeferredRevenueCurrent_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Current portion of deferred revenue</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="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="bcab_ReimbursementOfManufacturingCosts_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Reimbursement of manufacturing costs.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="bcab_ReimbursementOfManufacturingCosts_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Reimbursement Of Manufacturing Costs</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="bcab_ReimbursementOfManufacturingCosts_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Reimbursement Of Manufacturing Costs</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_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsExpirationsInPeriod_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Share-Based Compensation Arrangement by Share-Based Payment Award, Options, Expirations in Period</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsExpirationsInPeriod_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Expired, Number of Shares</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsExpirationsInPeriod_lbl" xlink:role="http://www.xbrl.org/2009/role/negatedLabel">Expired, Number of Shares</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardAwardVestingRightsPercentage_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Share-Based Compensation Arrangement by Share-Based Payment Award, Award Vesting Rights, Percentage</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardAwardVestingRightsPercentage_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Vesting percentage</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="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/verboseLabel">Total fair value of options vested</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisAbstract_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Abstract]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_RelatedPartyTransactionAxis_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Related Party Transaction [Axis]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="bcab_IssuanceOfCommonStockUnderStandbyEquityPurchaseAgreementValue_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Issuance of common stock under SEPA, value</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="bcab_IssuanceOfCommonStockUnderStandbyEquityPurchaseAgreementValue_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Issuance of Common Stock Under Standby Equity Purchase Agreement, Value</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="bcab_IssuanceOfCommonStockUnderStandbyEquityPurchaseAgreementValue_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Issuance of Common Stock Under Standby Equity Purchase Agreement, Value</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="bcab_IssuanceOfCommonStockForDirectorCompensationValue_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Issuance of common stock for director compensation(value)</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="bcab_IssuanceOfCommonStockForDirectorCompensationValue_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Issuance of common stock for director compensation(value)</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="bcab_IssuanceOfCommonStockForDirectorCompensationValue_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Issuance of common stock for director compensation</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_PreferredStockValue_lbl" xlink:role="http://www.xbrl.org/2003/role/periodEndLabel">Preferred Stock, Value, Issued, Ending Balance</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_PreferredStockValue_lbl" xlink:role="http://www.xbrl.org/2003/role/periodStartLabel">Preferred Stock, Value, Issued, Beginning Balance</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_PreferredStockValue_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel">Preferred Stock, Value, Issued, Total</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_PreferredStockValue_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Preferred Stock, Value, Issued</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_PreferredStockValue_lbl" xlink:role="http://www.xbrl.org/2003/role/verboseLabel">Issuance of Series D convertible preferred stock for cash, net of $4,317 of issuance costs</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_PreferredStockValue_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Preferred stock, $0.0001 par value; 200,000,000 shares authorized at March 31, 2026 and December 31, 2025; 0 shares issued and outstanding at March 31, 2026 and December 31, 2025</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/terseLabel">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/terseLabel">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_DerivativeFairValueOfDerivativeAsset_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel">Derivative Asset, Fair Value, Gross Asset, Total</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DerivativeFairValueOfDerivativeAsset_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Derivative Asset, Subject to Master Netting Arrangement, before Offset</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DerivativeFairValueOfDerivativeAsset_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Assets measured at fair value</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_CommonClassBMember_lbl" xlink:role="http://www.xbrl.org/2003/role/verboseLabel">Common Class B</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_CommonClassBMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Common Class B [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_CommonClassBMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Class B Common Stock</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_FairValueInputsLevel3Member_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Level 3</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_FairValueInputsLevel3Member_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Fair Value, Inputs, Level 3 [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_SegmentReportingAbstract_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Segment Reporting [Abstract]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ScheduleOfFairValueAssetsAndLiabilitiesMeasuredOnRecurringBasisTableTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Schedule of Fair Value, Assets and Liabilities Measured on Recurring Basis [Table Text Block]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ScheduleOfFairValueAssetsAndLiabilitiesMeasuredOnRecurringBasisTableTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Schedule Of Fair Value Assets And Liabilities Measured On Recurring Basis</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="bcab_RsusUnvestedOnModificationDateNumberOfShares_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">RSUs unvested on modification date, number of shares</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="bcab_RsusUnvestedOnModificationDateNumberOfShares_lbl" xlink:role="http://www.xbrl.org/2003/role/label">RSUs Unvested On Modification Date, Number of shares</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="bcab_RsusUnvestedOnModificationDateNumberOfShares_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">RSUs Unvested On Modification Date, Number of shares</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="us-gaap_RelatedPartyTransactionsAbstract_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Related Party Transactions [Abstract]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="bcab_TotalNumberOfModifiedUnvestedRestrictedStockUnits_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Total Number of Modified Unvested Restricted Stock Units</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="bcab_TotalNumberOfModifiedUnvestedRestrictedStockUnits_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Total Number of Modified Unvested Restricted Stock Units</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="bcab_TotalNumberOfModifiedUnvestedRestrictedStockUnits_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Total Number of Modified Unvested Restricted Stock Units</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, share</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, share</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 6)</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_LesseeLeasesPolicyTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Lessee, Leases [Policy Text Block]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_LesseeLeasesPolicyTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Leases</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/periodEndLabel">Weighted Average Grant Date Fair Value, Ending Balance</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">Weighted Average Grant Date Fair Value, Beginning Balance</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_StockIssuedDuringPeriodSharesShareBasedCompensation_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Shares Issued, Shares, Share-Based Payment Arrangement, after Forfeiture</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_StockIssuedDuringPeriodSharesShareBasedCompensation_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel">Shares Issued, Shares, Share-based Payment Arrangement, after Forfeiture, Total</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_StockIssuedDuringPeriodSharesShareBasedCompensation_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Issuance of common stock under equity incentive plans, net of shares withheld for taxes, shares</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 Expense</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/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/terseLabel">Total operating lease liabilities</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="bcab_LiquidityAndGoingConcernMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Liquidity and Going Concern [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="bcab_LiquidityAndGoingConcernMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Liquidity and Going Concern [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="bcab_EquityBasedCompensationMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Equity-based compensation</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="bcab_EquityBasedCompensationMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Equity Based Compensation [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="bcab_EquityBasedCompensationMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Equity Based Compensation [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="bcab_AmendmentLicenseAgreementSecondMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Amendment License Agreement Second [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="bcab_AmendmentLicenseAgreementSecondMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Amendment License Agreement Second [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="bcab_AmendmentLicenseAgreementSecondMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Amendment License Agreement Second [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="bcab_DecemberTwoThousandTwentyFourMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">December Two Thousand Twenty Four [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="bcab_DecemberTwoThousandTwentyFourMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">December Two Thousand Twenty Four [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="bcab_DecemberTwoThousandTwentyFourMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">December 2024 Offering and Warrant Issuance</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="bcab_NumberOfModifiedFullyVestedOptions_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Number of Modified Fully Vested Options</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="bcab_NumberOfModifiedFullyVestedOptions_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Number of Modified Fully Vested Options</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="bcab_NumberOfModifiedFullyVestedOptions_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Number of Modified Fully Vested Options</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">Weighted-average shares of common stock 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="bcab_CommonStockWarrantsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Common stock warrants [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="bcab_CommonStockWarrantsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Common stock warrants [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="bcab_CommonStockWarrantsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Common stock warrants</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="bcab_NumberOfOptionsUnvestedOnModificationDateNumberOfShares_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Number of options unvested on modification date, number of shares</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="bcab_NumberOfOptionsUnvestedOnModificationDateNumberOfShares_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Number Of Options Unvested On Modification Date, Number of shares</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="bcab_NumberOfOptionsUnvestedOnModificationDateNumberOfShares_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Number Of Options Unvested On Modification Date, Number of shares</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="dei_DocumentInformationLineItems_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Document Information [Line Items]</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_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="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>
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          <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 Events</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="bcab_ContextTherapeuticsIncMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Context Therapeutics Inc</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="bcab_ContextTherapeuticsIncMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Context Therapeutics Inc Member</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="bcab_ContextTherapeuticsIncMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Context Therapeutics Inc [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_RelatedPartyTransactionsDisclosureTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Related Party Transactions Disclosure [Text Block]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_RelatedPartyTransactionsDisclosureTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Related party transactions</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="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_StockholdersEquity_lbl" xlink:role="http://www.xbrl.org/2009/role/negatedPeriodEndLabel">Ending balances</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/terseLabel">Beginning balances</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_StockholdersEquity_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel">Total stockholders&#8217; equity</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 (in dollars per share)</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="bcab_TotalNumberOfModifiedUnvestedOptions_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Total Number of Modified Unvested Options</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="bcab_TotalNumberOfModifiedUnvestedOptions_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Total Number of Modified Unvested Options</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="bcab_TotalNumberOfModifiedUnvestedOptions_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Total Number of Modified Unvested Options</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="bcab_StockIssuedDuringPeriodSharesConversionOfClassBCommonStock_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Stock Issued During Period Shares Conversion Of Class B Common Stock</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="bcab_StockIssuedDuringPeriodSharesConversionOfClassBCommonStock_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Stock Issued During Period Shares Conversion Of Class B Common Stock</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="bcab_StockIssuedDuringPeriodSharesConversionOfClassBCommonStock_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Conversion of Class B common stock</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="us-gaap_FairValueLiabilitiesMeasuredOnRecurringBasisUnobservableInputReconciliationLineItems_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]</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_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="bcab_CommonSharesAuthorizedForIssuance_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Common shares authorized for issuance</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="bcab_CommonSharesAuthorizedForIssuance_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Common shares authorized for issuance.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="bcab_CommonSharesAuthorizedForIssuance_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Common Shares Authorized for Issuance</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</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_FairValueDisclosuresTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Fair Value Disclosures [Text Block]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_FairValueDisclosuresTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Fair Value Measurements</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_NoncashInvestingAndFinancingItemsAbstract_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Noncash Investing and Financing Items [Abstract]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_NoncashInvestingAndFinancingItemsAbstract_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Supplemental disclosure of non-cash investing and financing activities</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="bcab_CollaborationAgreementStartDate_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Collaboration Amendment Date</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="bcab_CollaborationAgreementStartDate_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Collaboration agreement start date.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="bcab_CollaborationAgreementStartDate_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Collaboration Agreement Start Date</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="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/terseLabel">Interest Payable</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/negatedLabel">Interest expense</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_StockIssuedDuringPeriodValueOther_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Stock Issued During Period, Value, Other</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_StockIssuedDuringPeriodValueOther_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Issuance of common stock under equity incentive plans, net of shares withheld for taxes</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardAwardVestingRights_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Share-Based Compensation Arrangement by Share-Based Payment Award, Award Vesting Rights</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardAwardVestingRights_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Vesting terms, description</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="bcab_PercentageOfAnnualIncreasedShares_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Percentage of Annual increased Shares</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="bcab_PercentageOfAnnualIncreasedShares_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Percentage of Annual increased Shares</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_SettlementLiabilitiesCurrent_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Settlement Liabilities, Current</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_SettlementLiabilitiesCurrent_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Settlement of principal and accrued interest</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="bcab_EvalstotugBAThreeZeroSevenOneMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Evalstotug, BA3071</link:label>
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          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="bcab_EvalstotugBAThreeZeroSevenOneMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Evalstotug BA Three Zero Seven One [Member]</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_DebtMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Debt [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DebtMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Outstanding Debt [Member]</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_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="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/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/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, plant and equipment, gross</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, Number of Shares</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="bcab_MergerAndRelatedShareConsolidationPolicyTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Merger and Related Share Consolidation</link:label>
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          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="bcab_MergerAndRelatedShareConsolidationPolicyTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Merger And Related Share Consolidation Policy TextBlock</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_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="bcab_TwoThousandTwentyEquityIncentivePlanMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Two thousand twenty equity incentive plan.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="bcab_TwoThousandTwentyEquityIncentivePlanMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Two Thousand Twenty Equity Incentive Plan [Member]</link:label>
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          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_StockholdersEquityNoteAbstract_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Stockholders' Equity Note [Abstract]</link:label>
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          <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/periodStartLabel">Cash and cash equivalents, 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/periodEndLabel">Cash and cash equivalents, end of period</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="bcab_CompensationCostForTheModifiedUnvestedOptions_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Compensation Cost for the Modified Unvested Options</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="bcab_CompensationCostForTheModifiedUnvestedOptions_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Compensation Cost for the Modified Unvested Options</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="bcab_CompensationCostForTheModifiedUnvestedOptions_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Compensation Cost for the Modified Unvested Options</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/terseLabel">Warrants excercise 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/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_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/terseLabel">Equity-based compensation expense</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_AllocatedShareBasedCompensationExpense_lbl" xlink:role="http://www.xbrl.org/2009/role/negatedLabel">Equity-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="srt_TitleOfIndividualAxis_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Title and Position [Axis]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="srt_TitleOfIndividualAxis_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Title of Individual</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_DefinedContributionPlanCostRecognized_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Defined Contribution Plan, Cost</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DefinedContributionPlanCostRecognized_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Contributions made by company</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, Number of Shares</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsExercisableNumber_lbl" xlink:role="http://www.xbrl.org/2009/role/negatedLabel">Exercisable, Number of Shares</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="bcab_PersonnelAndRelatedMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Personnel and related</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="bcab_PersonnelAndRelatedMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Personnel And Related [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="bcab_PersonnelAndRelatedMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Personnel And Related [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_AccruedSalariesCurrent_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Accrued Salaries, Current</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_AccruedSalariesCurrent_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_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/verboseLabel">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/terseLabel">Restricted Stock Units and Stock Options</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_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="us-gaap_StatementClassOfStockAxis_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Class of Stock</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="bcab_LessorOperatingLeasesOptionToExtend_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Lessor Operating Leases Option To Extend.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="bcab_LessorOperatingLeasesOptionToExtend_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Lessor Operating Leases Option To Extend</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/terseLabel">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="bcab_RecalculatedCompensationCostOfTheModifiedOptions_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Recalculated compensation cost of the modified options</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="bcab_RecalculatedCompensationCostOfTheModifiedOptions_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Recalculated Compensation Cost Of The Modified Options</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="bcab_RecalculatedCompensationCostOfTheModifiedOptions_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Recalculated Compensation Cost Of The Modified Options</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="bcab_CommonStockOptionsAndRestrictedStockUnitsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Common stock options and restricted stock units.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="bcab_CommonStockOptionsAndRestrictedStockUnitsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Common Stock Options and Restricted Stock Units [Member]</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="bcab_GainLossOnPre-PaidAdvanceAgreementLiability_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Gain Loss On Pre-Paid Advance Agreement Liability</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="bcab_GainLossOnPre-PaidAdvanceAgreementLiability_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Gain Loss On Pre-Paid Advance Agreement Liability</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="bcab_GainLossOnPre-PaidAdvanceAgreementLiability_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Gain on PPAs liability</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">2027</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="bcab_OrganizationPolicyTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Organization.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="bcab_OrganizationPolicyTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Organization Policy [Text Block]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="bcab_OrganizationPolicyTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Organization</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">Weighted-average shares of common stock 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/totalLabel">Weighted Average Number of Shares Outstanding, Diluted, Total</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="bcab_TotalProgramExpensesMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Total Program Expenses [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="bcab_TotalProgramExpensesMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Total Program Expenses [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="bcab_TotalProgramExpensesMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Total program expenses</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="bcab_ClassOfWarrantOrRightOutstandingAndExercisable_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Class of Warrant or Right, Outstanding and Exercisable</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="bcab_ClassOfWarrantOrRightOutstandingAndExercisable_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Class of Warrant or Right, Outstanding and Exercisable</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="bcab_ClassOfWarrantOrRightOutstandingAndExercisable_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Class of Warrant or Right, Outstanding and Exercisable</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="us-gaap_OtherExpenses_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Other Expenses</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_OtherExpenses_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Other expense</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_OtherExpenses_lbl" xlink:role="http://www.xbrl.org/2009/role/negatedTerseLabel">Other expense</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_IncreaseDecreaseInAccountsPayableAndAccruedLiabilities_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel">Increase (Decrease) in Accounts Payable and Accrued Liabilities, Total</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_IncreaseDecreaseInAccountsPayableAndAccruedLiabilities_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Increase (Decrease) in Accounts Payable and Accrued Liabilities</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_IncreaseDecreaseInAccountsPayableAndAccruedLiabilities_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Accounts payable and accrued expenses</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_FairValueNetDerivativeAssetLiabilityMeasuredOnRecurringBasisUnobservableInputReconciliationTableTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Fair Value, Net Derivative Asset (Liability) Measured on Recurring Basis, Unobservable Input Reconciliation [Table Text Block]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_FairValueNetDerivativeAssetLiabilityMeasuredOnRecurringBasisUnobservableInputReconciliationTableTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Schedule of Fair Value, Net Derivative Asset (Liability) Measured on Recurring Basis, Unobservable Input Reconciliation</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_PrepaidExpenseAndOtherAssetsCurrent_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Prepaid Expense and Other Assets, Current</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_PrepaidExpenseAndOtherAssetsCurrent_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_PrepaidExpenseAndOtherAssetsCurrent_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel">Total</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/2003/role/terseLabel">Number of Shares, Forfeited</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">Number of Shares, Forfeited</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardPercentageOfOutstandingStockMaximum_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Share-Based Compensation Arrangement by Share-Based Payment Award, Percentage of Outstanding Stock Maximum</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardPercentageOfOutstandingStockMaximum_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Share Based Compensation Arrangement By Share Based Payment Award Percentage Of Outstanding Stock Maximum</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_SupplementalBalanceSheetDisclosuresTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Balance Sheet Details</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_SegmentReportingDisclosureTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Segment Reporting Disclosure [Text Block]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_SegmentReportingDisclosureTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Segment Information</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_GeneralAndAdministrativeExpense_lbl" xlink:role="http://www.xbrl.org/2009/role/negatedLabel">General and administrative expense (includes related party amounts of $0 and $[ ], respectively)</link:label>
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          <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/terseLabel">General and administrative expense</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="bcab_Pre-PaidAdvance_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Pre-Paid Advance</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="bcab_Pre-PaidAdvance_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Pre-Paid Advance</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="bcab_Pre-PaidAdvance_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Pre-Paid Advance</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOtherIncreasesDecreasesInPeriod_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Increase in issuance of common stock</link:label>
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          <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>
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          <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>
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          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="bcab_CompensationCostForTheModifiedUnvestedRestrictedStockUnits_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Compensation Cost for the Modified Unvested Restricted Stock Units</link:label>
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          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="bcab_OrganizationAndSummaryOfSignificantAccountingPoliciesLineItems_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Organization and Summary of Significant Accounting Policies.</link:label>
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          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_CollaborativeArrangementsAndNoncollaborativeArrangementTransactionsLineItems_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DepreciationDepletionAndAmortization_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel">Depreciation, Depletion and Amortization, Total</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DepreciationDepletionAndAmortization_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Depreciation, Depletion and Amortization</link:label>
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          <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>
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          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ConvertiblePreferredStockMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Convertible Preferred Stock [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ConvertiblePreferredStockMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Convertible Preferred Stock [Member]</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="us-gaap_ScheduleOfInterestRateDerivativesTableTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Schedule of Interest Rate Derivatives [Table Text Block]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ScheduleOfInterestRateDerivativesTableTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Summary of Weighted Average Remaining Lease Term and Weighted Average Discount Rate</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="bcab_StandbyEquityPurchaseAgreementMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Standby Equity Purchase Agreement [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="bcab_StandbyEquityPurchaseAgreementMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Standby Equity Purchase Agreement [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="bcab_StandbyEquityPurchaseAgreementMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Standby Equity Purchase Agreement [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_StockIssuedDuringPeriodValueNewIssues_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Stock Issued During Period, Value, New Issues</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_StockIssuedDuringPeriodValueNewIssues_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Issuance of common stock, net of issuance costs</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="us-gaap_OperatingLeasesFutureMinimumPaymentsDueCurrent_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">2022</link:label>
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          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="bcab_Pre-PaidAdvanceAgreementPPAsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Pre-Paid Advance Agreement PPAs [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="bcab_Pre-PaidAdvanceAgreementPPAsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">PPAs [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ScheduleOfShareBasedCompensationRestrictedStockUnitsAwardActivityTableTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Share-Based Payment Arrangement, Restricted Stock Unit, Activity [Table Text Block]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ScheduleOfShareBasedCompensationRestrictedStockUnitsAwardActivityTableTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Summary of Restricted Stock Units</link:label>
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          <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/periodStartLabel">Outstanding, Aggregate 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">Outstanding, Aggregate Intrinsic Value</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="bcab_Pre-PaidAdvanceRemainingPrincipalAmount_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Pre-Paid Advance Remaining Principal Amount</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="bcab_Pre-PaidAdvanceRemainingPrincipalAmount_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Pre-Paid Advance Remaining Principal Amount</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>
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          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_WarrantsAndRightsOutstandingTerm_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Warrants and Rights Outstanding, Term</link:label>
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          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsExpectedDividendRate_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Expected dividend yield</link:label>
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          <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>
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          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="bcab_AwardsAvailableForFutureIssuanceUnderTheTwoThousandTwentyPlan_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Awards Available For Future Issuance Under The Two Thousand Twenty Plan</link:label>
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          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsRiskFreeInterestRate_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Share-Based Compensation Arrangement by Share-Based Payment Award, Fair Value Assumptions, Risk Free Interest Rate</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsRiskFreeInterestRate_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Risk-free interest rate</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsRiskFreeInterestRate_lbl" xlink:role="http://www.xbrl.org/2003/role/verboseLabel">Risk-free rate</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_IncreaseDecreaseInPrepaidDeferredExpenseAndOtherAssets_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel">Increase (Decrease) in Prepaid Expense and Other Assets, Total</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_IncreaseDecreaseInPrepaidDeferredExpenseAndOtherAssets_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Increase (Decrease) in Prepaid Expense and Other Assets</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_IncreaseDecreaseInPrepaidDeferredExpenseAndOtherAssets_lbl" xlink:role="http://www.xbrl.org/2009/role/negatedLabel">Prepaid expenses and other assets</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>
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          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="bcab_UpfrontNonRefundablePayment_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Upfront non-refundable payment.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="bcab_UpfrontNonRefundablePayment_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Upfront Non Refundable Payment</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="bcab_UpfrontNonRefundablePayment_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Upfront Non-Refundable Payment</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="bcab_TaxesRelatedToNetShareSettlementOfEquityAwards_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Taxes related to net share settlement of equity awards</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="bcab_TaxesRelatedToNetShareSettlementOfEquityAwards_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Taxes related to net share settlement of equity awards</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="bcab_TaxesRelatedToNetShareSettlementOfEquityAwards_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Taxes related to net share settlement of equity awards</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">Cash flows from investing activities</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_CompensationAndRetirementDisclosureAbstract_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Retirement Benefits [Abstract]</link:label>
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          <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/verboseLabel">Accounts payable</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsVestedInPeriodFairValue1_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Share-Based Compensation Arrangement by Share-Based Payment Award, Options, Vested in Period, Fair Value</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsVestedInPeriodFairValue1_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Total fair value of options vested</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>
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          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="bcab_IssuanceOfCommonStockUnderPre-PaidAdvanceAgreementShares_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Issuance Of Common Stock Under Pre-Paid Advance Agreement, Shares</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="bcab_IssuanceOfCommonStockUnderPre-PaidAdvanceAgreementShares_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Issuance Of Common Stock Under Pre-Paid Advance Agreement, Shares</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="bcab_IssuanceOfCommonStockUnderPre-PaidAdvanceAgreementShares_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Issuance of common stock under PPAs, share</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_RevenueRecognitionRevenueReductions_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Revenue Recognition</link:label>
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          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_FairValueMeasurementPolicyPolicyTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Fair Value Option</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_FairValueMeasurementPolicyPolicyTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Fair Value Measurement, Policy [Policy Text Block]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_FairValueDisclosuresAbstract_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Fair Value Disclosures [Abstract]</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="us-gaap_OtherDebtSecuritiesMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Other Debt Obligations [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_OtherDebtSecuritiesMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Other Debt Obligations [Member]</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">Nine months ending December 31, 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="bcab_CommonSockOtionsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Common Stock Options</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="bcab_CommonSockOtionsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Common stock options.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="bcab_CommonSockOtionsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Common Sock Otions [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="bcab_PrepaidResearchAndDevelopmentExpense_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Prepaid research and development expense.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="bcab_PrepaidResearchAndDevelopmentExpense_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Prepaid Research And Development Expense</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="bcab_PrepaidResearchAndDevelopmentExpense_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Prepaid research and development</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="bcab_RestructuringLiability_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Restructuring liability</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="bcab_RestructuringLiability_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Restructuring liability</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="bcab_RestructuringLiability_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Accrued severance</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="bcab_CompensationExpenseOnIssuanceOfDirectorCompensation_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Compensation Expense On Issuance Of Director Compensation</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="bcab_CompensationExpenseOnIssuanceOfDirectorCompensation_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Compensation Expense On Issuance Of Director Compensation</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="bcab_CompensationExpenseOnIssuanceOfDirectorCompensation_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Compensation expense on issuance of director compensation</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DerivativeInstrumentRiskAxis_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Derivative Instrument [Axis]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DerivativeInstrumentRiskAxis_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Derivative Instrument</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="us-gaap_LesseeOperatingLeaseLiabilityPaymentsDueAfterYearFive_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Thereafter</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_FairValueOfAssetsAcquired_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Fair Value of Assets Acquired</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_FairValueOfAssetsAcquired_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_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_ProceedsFromIssuanceOfSharesUnderIncentiveAndShareBasedCompensationPlans_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Proceeds from issuance of common stock under SEPA</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ProceedsFromIssuanceOfSharesUnderIncentiveAndShareBasedCompensationPlans_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Proceeds, Issuance of Shares, Share-Based Payment Arrangement, Excluding Option Exercised</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/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/terseLabel">Revenues</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="bcab_AccruedResearchAndDevelopmentExpenseCurrent_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Accrued research and development expense current.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="bcab_AccruedResearchAndDevelopmentExpenseCurrent_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Accrued Research And Development Expense Current</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="bcab_AccruedResearchAndDevelopmentExpenseCurrent_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Accrued research and development</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 investing activities</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_ScheduleOfSegmentReportingInformationBySegmentTable_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Schedule of Segment Reporting Information, by Segment [Table]</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, Weighted-Average Exercise Price per Share</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_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_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="bcab_WarrantLiability_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Warrant Liability</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="bcab_WarrantLiability_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Warrant Liability</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="bcab_WarrantLiability_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Warrant liability</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="bcab_WarrantLiability_lbl" xlink:role="http://www.xbrl.org/2003/role/periodStartLabel">Balance at December 31, 2025</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="bcab_WarrantLiability_lbl" xlink:role="http://www.xbrl.org/2003/role/periodEndLabel">Balance at March 31, 2026</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ScheduleOfCollaborativeArrangementsAndNoncollaborativeArrangementTransactionsTable_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Collaborative Arrangement and Arrangement Other than Collaborative [Table]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ScheduleOfCollaborativeArrangementsAndNoncollaborativeArrangementTransactionsTable_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Schedule Of Collaborative Arrangements And Noncollaborative Arrangement Transactions [Table]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="dei_DocumentInformationTable_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Document Information [Table]</link:label>
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          <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, Ending Balance, Weighted-Average Exercise Price per Share | $ / shares</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, Beginning Balance, Weighted-Average Exercise Price per Share</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Fair Value, Recurring and Nonrecurring [Table]</link:label>
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          <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="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="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="us-gaap_ScheduleOfRelatedPartyTransactionsByRelatedPartyTable_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Related Party Transaction [Table]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ScheduleOfRelatedPartyTransactionsByRelatedPartyTable_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Schedule Of Related Party Transactions By Related Party [Table]</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_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">Cash flows from financing activities</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardFairValueAssumptionsExpectedTerm1_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Share-Based Compensation Arrangement by Share-Based Payment Award, Fair Value Assumptions, Expected Term</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardFairValueAssumptionsExpectedTerm1_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Expected term</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardFairValueAssumptionsExpectedTerm1_lbl" xlink:role="http://www.xbrl.org/2003/role/verboseLabel">Expected term (in years)</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="dei_EntityExTransitionPeriod_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Entity Ex Transition Period</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="dei_EntityExTransitionPeriod_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Entity Ex Transition Period</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="us-gaap_LesseeOperatingLeaseLiabilityPaymentsDue_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Total future lease 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/totalLabel">Total future lease payments</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="us-gaap_LesseeOperatingLeaseLiabilityUndiscountedExcessAmount_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Less: imputed interest</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: imputed interest</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="bcab_PercentageOfOutstandingCommonStock_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Percentage Of Outstanding Common Stock</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="bcab_PercentageOfOutstandingCommonStock_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Percentage of outstanding common stock</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="bcab_PercentageOfOutstandingCommonStock_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Percentage of outstanding common stock</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_AccountsPayableCurrentAndNoncurrent_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Accounts payble includes related party amounts</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_AccountsPayableCurrentAndNoncurrent_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel">Accounts Payable, Total</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_AccountsPayableCurrentAndNoncurrent_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Accounts Payable</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_OperatingLeasesFutureMinimumPaymentsDueInTwoYears_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Operating Leases, Future Minimum Payments, Due in Two Years</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_OperatingLeasesFutureMinimumPaymentsDueInTwoYears_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">2023</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="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_FairValueByAssetClassAxis_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Asset Class [Axis]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="bcab_AwardsAvailableForFutureIssuanceUnderESPP_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Awards Available For Future Issuance Under ESPP</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="bcab_AwardsAvailableForFutureIssuanceUnderESPP_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Awards Available For Future Issuance Under ESPP</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="bcab_AwardsAvailableForFutureIssuanceUnderESPP_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Awards available for future issuance under the ESPP</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ScheduleOfFutureMinimumRentalPaymentsForOperatingLeasesTableTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Schedule of Future Minimum Rental Payments for Operating Leases [Table Text Block]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ScheduleOfFutureMinimumRentalPaymentsForOperatingLeasesTableTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Schedule of Expected Future Minimum Payments Under The Non Cancelable Operating Lease</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_PrepaidInsurance_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Prepaid insurance</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_PrepaidInsurance_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Prepaid Insurance</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_IPOMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">IPO [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_IPOMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">IPO [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="bcab_CarolynAndersonShortMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Carolyn Anderson Short.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="bcab_CarolynAndersonShortMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Carolyn Anderson Short [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="bcab_CarolynAndersonShortMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Carolyn Anderson Short</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_StockIssuedDuringPeriodSharesEmployeeStockPurchasePlans_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Issuance of common stock for Employee Stock Purchase Plan, shares</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_StockIssuedDuringPeriodSharesEmployeeStockPurchasePlans_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Stock Issued During Period, Shares, Employee Stock Purchase Plans</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="bcab_ProfitsInterestIncentivePlanTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Profits interest incentive plan text block.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="bcab_ProfitsInterestIncentivePlanTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Profits Interest Incentive Plan [Text Block]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="bcab_ProfitsInterestIncentivePlanTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Profits Interest Incentive Plan</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="bcab_RsusFullyVestedOnTheModificationDateNumberOfShares_lbl" xlink:role="http://www.xbrl.org/2003/role/verboseLabel">Options Fully Vested On The Modification Date, Number of shares</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="bcab_RsusFullyVestedOnTheModificationDateNumberOfShares_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">RSUs fully vested on the modification date, number of shares</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="bcab_RsusFullyVestedOnTheModificationDateNumberOfShares_lbl" xlink:role="http://www.xbrl.org/2003/role/label">RSUs Fully Vested On The Modification Date, Number of shares</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="bcab_RsusFullyVestedOnTheModificationDateNumberOfShares_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">RSUs Fully Vested On The Modification Date, Number of shares</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="bcab_IncreaseInCompensationCostOfFullyVestedOptions_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Increase In Compensation Cost Of Fully Vested Options</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="bcab_IncreaseInCompensationCostOfFullyVestedOptions_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Increase In Compensation Cost Of Fully Vested Options</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="bcab_IncreaseInCompensationCostOfFullyVestedOptions_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Increase In Compensation Cost Of Fully Vested Options</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_MaximumMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Maximum</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="bcab_UnpaidDeferredFinancingCost_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Unpaid Deferred Financing Cost</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="bcab_UnpaidDeferredFinancingCost_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">UnpaidDeferredFinancingCosts</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="bcab_UnpaidDeferredFinancingCost_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Unpaid deferred financing costs</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="bcab_RestructuringCostsTable_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Restructuring Costs [Table]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="bcab_RestructuringCostsTable_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Restructuring Costs [Table]</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 per Share</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 value</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/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/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/label">Common Stock, Value, Issued</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ConsolidationPolicyTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Merger and Related Share Consolidation</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ConsolidationPolicyTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Consolidation, Policy [Policy Text Block]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_StockholdersEquityIncludingPortionAttributableToNoncontrollingInterest_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel">Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest, Total</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_StockholdersEquityIncludingPortionAttributableToNoncontrollingInterest_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Equity, Including Portion Attributable to Noncontrolling Interest</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_StockholdersEquityIncludingPortionAttributableToNoncontrollingInterest_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_StockholdersEquityIncludingPortionAttributableToNoncontrollingInterest_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="bcab_LiabilityToLicensor_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Liability to licensor</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="bcab_LiabilityToLicensor_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Liability to licensor</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="bcab_LiabilityToLicensor_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Liability to licensor</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_RelatedPartyTransactionAmountsOfTransaction_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Related party amounts</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_RelatedPartyTransactionAmountsOfTransaction_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Related Party Transaction, Amounts of Transaction</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_RelatedPartyTransactionAmountsOfTransaction_lbl" xlink:role="http://www.xbrl.org/2003/role/verboseLabel">Related party amounts</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="bcab_MilestonePaymentReceived_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Milestone payment received</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="bcab_MilestonePaymentReceived_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Milestone Payment Received</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="bcab_MilestonePaymentReceived_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Milestone Payment Received</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="bcab_TaxRelatedToNetSettlementOfEquityAwardIncludedInAccountsPayableAndAccruedExpenses_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Tax related to net settlement of equity award included in accounts payable and accrued expenses</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="bcab_TaxRelatedToNetSettlementOfEquityAwardIncludedInAccountsPayableAndAccruedExpenses_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Tax related to net settlement of equity award included in accounts payable and accrued expenses</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="bcab_TaxRelatedToNetSettlementOfEquityAwardIncludedInAccountsPayableAndAccruedExpenses_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Tax related to net settlement of equity awards included in accounts payable and accrued expenses</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsExpectedVolatilityRate_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Share-Based Compensation Arrangement by Share-Based Payment Award, Fair Value Assumptions, Expected Volatility Rate</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsExpectedVolatilityRate_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Expected volatility</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 (in shares)</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_FairValueBalanceSheetGroupingFinancialStatementCaptionsLineItems_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_RelatedPartyTransactionLineItems_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Related Party Transaction [Line Items]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_RelatedPartyTransactionLineItems_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Related Party Transaction [Line Items]</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="us-gaap_DebtDisclosureTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Debt Disclosure [Text Block]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DebtDisclosureTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Debt</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DebtDisclosureTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/verboseLabel">Pre-Paid Advance</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_RestructuringCostsAbstract_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Restructuring Costs [Abstract]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_LesseeDisclosureAbstract_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Lessee Disclosure [Abstract]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_FairValueLiabilitiesMeasuredOnRecurringBasisUnobservableInputReconciliationTable_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Table]</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">Total other income</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_AdditionalPaidInCapital_lbl" xlink:role="http://www.xbrl.org/2003/role/periodEndLabel">Additional Paid in Capital, Ending Balance</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_AdditionalPaidInCapital_lbl" xlink:role="http://www.xbrl.org/2003/role/periodStartLabel">Additional Paid in Capital, Beginning Balance</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_AdditionalPaidInCapital_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel">Additional Paid in Capital, Total</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_AdditionalPaidInCapital_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Additional Paid in Capital</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_AdditionalPaidInCapital_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_SharebasedCompensationSharesAuthorizedUnderStockOptionPlansExercisePriceRangeExercisableOptionsWeightedAverageExercisePrice1_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Contractual Exercise Price</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_SharebasedCompensationSharesAuthorizedUnderStockOptionPlansExercisePriceRangeExercisableOptionsWeightedAverageExercisePrice1_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Share-Based Payment Arrangement, Option, Exercise Price Range, Exercisable, Weighted Average Exercise Price</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="us-gaap_AccountsPayableAndAccruedLiabilitiesCurrent_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Accounts Payable and Accrued Liabilities, Current</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_AccountsPayableAndAccruedLiabilitiesCurrent_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel">Total</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_AccountsPayableAndAccruedLiabilitiesCurrent_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Accounts payable and accrued expenses</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="bcab_CommonStockOptionsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Common stock options.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="bcab_CommonStockOptionsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Common Stock Options [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="bcab_CommonStockOptionsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Common Stock Options</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">Aggregate potential future gross sale proceeds</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/verboseLabel">Gross proceeds to the Company</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="srt_ConsolidationItemsAxis_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Consolidation Items [Axis]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_SubsequentEventsDate_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Subsequent Event, Date</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_SubsequentEventsDate_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Subsequent Event, Date</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</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">Number of Shares, Granted</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/terseLabel">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 (years)</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="bcab_BAThreeOneEightTwoMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">BA Three One Eight Two [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="bcab_BAThreeOneEightTwoMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">BA Three One Eight Two [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="bcab_BAThreeOneEightTwoMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">BA3182</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ShareBasedCompensationOptionAndIncentivePlansPolicy_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Share-Based Payment Arrangement [Policy Text Block]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ShareBasedCompensationOptionAndIncentivePlansPolicy_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Stock-Based Compensation</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="bcab_OzuriftamabVedotinBAThreeZeroTwoOneMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Ozuriftamab Vedotin BA Three Zero Two One [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="bcab_OzuriftamabVedotinBAThreeZeroTwoOneMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Ozuriftamab Vedotin BA Three Zero Two One [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="bcab_OzuriftamabVedotinBAThreeZeroTwoOneMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Ozuriftamab vedotin, BA3021</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="bcab_OtherCABProgramsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Other CAB Programs [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="bcab_OtherCABProgramsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Other CAB Programs [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="bcab_OtherCABProgramsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Other CAB Programs</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="bcab_MaximumPotentialAggregatePayments_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Maximum Potential Aggregate Payments</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="bcab_MaximumPotentialAggregatePayments_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Maximum Potential Aggregate Payments</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="bcab_MaximumPotentialAggregatePayments_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Maximum Potential Aggregate Payments</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="bcab_MecbotamabVedotinBAThreeZeroOneOneMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Mecbotamab vedotin, BA3011</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="bcab_MecbotamabVedotinBAThreeZeroOneOneMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Mecbotamab Vedotin BA Three Zero One One [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="bcab_MecbotamabVedotinBAThreeZeroOneOneMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Mecbotamab Vedotin BA Three Zero One One [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_SaleOfStockNumberOfSharesIssuedInTransaction_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Number of shares sold under transaction</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_SaleOfStockNumberOfSharesIssuedInTransaction_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Sale of Stock, Number of Shares Issued in Transaction</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/terseLabel">Issuance of common stock, net of issuance costs, shares</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 under ESPP</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="bcab_PPPLoanMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">PPP Loan</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="bcab_PPPLoanMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">P P P Loan [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="bcab_PPPLoanMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">PPP Loan.</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/2003/role/terseLabel">Number of Shares, Vested</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">Number of Shares, Vested</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ConsolidationVariableInterestEntityPolicy_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Consolidation, Variable Interest Entity, Policy [Policy Text Block]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ConsolidationVariableInterestEntityPolicy_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Variable Interest Entities</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">Net loss per common 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/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_ScheduleOfSegmentReportingInformationBySegmentTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Schedule of Segment expenses reviewed by the CDMO</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ScheduleOfSegmentReportingInformationBySegmentTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Schedule of Segment Reporting Information, by Segment [Table Text Block]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_OperatingSegmentsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Operating Segments [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="srt_TitleOfIndividualWithRelationshipToEntityDomain_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Title and Position [Domain]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="srt_TitleOfIndividualWithRelationshipToEntityDomain_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Title of Individual</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="bcab_ChangeInFairValueOfPre-PaidAdvance_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Change in Fair Value of Pre-Paid Advance</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="bcab_ChangeInFairValueOfPre-PaidAdvance_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Change in Fair Value of Pre-Paid Advance</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="bcab_ChangeInFairValueOfPre-PaidAdvance_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Change in fair value of PPAs liability</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="bcab_PrePaidAdvancePrincipalAmount_lbl" xlink:role="http://www.xbrl.org/2003/role/label">PrePaid Advance Principal Amount</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="bcab_PrePaidAdvancePrincipalAmount_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">PrePaid Advance Principal Amount</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="bcab_PrePaidAdvancePrincipalAmount_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Prepaid advance principal amount</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DebtInstrumentFaceAmount_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Aggregate principal amount</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DebtInstrumentFaceAmount_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Debt Instrument, Face Amount</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="bcab_Pre-PaidAdvanceAgreementsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Pre-Paid Advance Agreements [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="bcab_Pre-PaidAdvanceAgreementsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Pre-Paid Advance Agreements [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="bcab_Pre-PaidAdvanceAgreementsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Pre-Paid Advance Agreements [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="bcab_AmendedLicenseAgreementSecondPaymentDueDate_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Amended License Agreement Second Payment Due Date</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="bcab_AmendedLicenseAgreementSecondPaymentDueDate_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Amended License Agreement Second Payment Due Date</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_VariableLeaseCost_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Variable Lease, Cost</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_VariableLeaseCost_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Variable lease expense</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_StockIssuedDuringPeriodValueEmployeeStockPurchasePlan_lbl" xlink:role="http://www.xbrl.org/2009/role/negatedLabel">Issuance of common stock for Employee Stock Purchase Plan</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_StockIssuedDuringPeriodValueEmployeeStockPurchasePlan_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Issuance of common stock for Employee Stock Purchase Plan</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_StockIssuedDuringPeriodValueEmployeeStockPurchasePlan_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Stock Issued During Period, Value, Employee Stock Purchase Plan</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_StockIssuedDuringPeriodValueEmployeeStockPurchasePlan_lbl" xlink:role="http://www.xbrl.org/2009/role/negatedTerseLabel">Proceeds from issuance of common stock under Employee Stock Purchase Plan</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_StockIssuedDuringPeriodValueEmployeeStockPurchasePlan_lbl" xlink:role="http://www.xbrl.org/2003/role/verboseLabel">Proceeds from issuance of common stock under Employee Stock Purchase Plan</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="bcab_AggregateGrossProceeds_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Aggregate Gross Proceeds</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="bcab_AggregateGrossProceeds_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Aggregate Gross Proceeds</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="bcab_AggregateGrossProceeds_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Aggregate gross proceeds</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="bcab_TaxesrelatedtonetsharesettlementofequityawardsShares_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Taxes Related To Net Share Settlement Of Equity Awards Shares</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="bcab_TaxesrelatedtonetsharesettlementofequityawardsShares_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Taxes Related To Net Share Settlement Of Equity Awards Shares</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="bcab_TaxesrelatedtonetsharesettlementofequityawardsShares_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Taxes related to net share settlement of equity awards, Share</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_OperatingLeaseWeightedAverageRemainingLeaseTerm1_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Weighted average remaining lease term (in years)</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_SegmentReportingInformationLineItems_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Segment Reporting Information [Line Items]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_LessorOperatingLeaseOptionToExtend_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Lessor, Operating Lease, Option to Extend</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_LessorOperatingLeaseOptionToExtend_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Option to extend the term of the lease</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_StockholdersEquityNoteStockSplitConversionRatio1_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Stockholders' Equity Note, Stock Split, Conversion Ratio</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="bcab_OrganizationAndSummaryOfSignificantAccountingPoliciesTable_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Organization And Summary Of Significant Accounting Policies [Table]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="bcab_OrganizationAndSummaryOfSignificantAccountingPoliciesTable_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Organization And Summary Of Significant Accounting Policies [Table]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="bcab_OrganizationAndSummaryOfSignificantAccountingPoliciesTable_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Organization and Summary of Significant Accounting Policies.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_LeaseCost_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Lease, Cost</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_LeaseCost_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Total lease expense, net</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_LeaseCost_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel">Total lease expense, net</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_CashAndCashEquivalentsPolicyTextBlock_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_CashAndCashEquivalentsPolicyTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Cash and Cash Equivalents, Policy [Policy Text Block]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="bcab_GrossProceedsFromPre-PaidAdvanceAgreements_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Gross proceeds to the Company</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="bcab_GrossProceedsFromPre-PaidAdvanceAgreements_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Gross Proceeds From Pre-Paid Advance Agreements</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="bcab_GrossProceedsFromPre-PaidAdvanceAgreements_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Gross Proceeds From Pre-Paid Advance Agreements</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_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/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">Total</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="bcab_ClassOfWarrantExercisePriceAsAdjusted_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Class Of Warrant Exercise Price As Adjusted</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="bcab_ClassOfWarrantExercisePriceAsAdjusted_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Class Of Warrant Exercise Price As Adjusted</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="bcab_ClassOfWarrantExercisePriceAsAdjusted_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Adjustment of warrants per share</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">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">Accumulate 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/totalLabel">Share-based Payment Arrangement, Noncash Expense, Total</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</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/verboseLabel">Non-cash stock-based compensation charges</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="us-gaap_OperatingLeaseWeightedAverageDiscountRatePercent_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Weighted average discount rate percentage</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, less current portion</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_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_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 (used in) financing activities</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="bcab_AmendedLicenseAgreementFirstPaymentDueDate_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Amended License Agreement First Payment Due Date</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="bcab_AmendedLicenseAgreementFirstPaymentDueDate_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Amended License Agreement First Payment Due Date</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="us-gaap_LeaseCostTableTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Components of Lease Expense</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_NonoperatingIncomeExpenseAbstract_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Nonoperating Income (Expense) [Abstract]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_NonoperatingIncomeExpenseAbstract_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Other income (expense):</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DerivativeContractTypeDomain_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Derivative Contract [Domain]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DerivativeContractTypeDomain_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Derivative Contract</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="bcab_PrivatePlacementOfCommonStockMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Private Placement of Common Stock.</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="bcab_PrivatePlacementOfCommonStockMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Private Placement of Common Stock [Member]</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">Schedule of Anti-dilutive Securities Excluded from Calculation of Diluted Net Loss Per Share</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="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="bcab_LaboratoryEquipmentMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Laboratory Equipment</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="bcab_LaboratoryEquipmentMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Laboratory Equipment [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="bcab_LaboratoryEquipmentMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Laboratory equipment [Member]</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="bcab_SharesAvailableForFutureIssuanceUnderSEPA_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Shares Available For Future Issuance Under SEPA</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="bcab_SharesAvailableForFutureIssuanceUnderSEPA_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Shares Available For Future Issuance Under SEPA</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="bcab_SharesAvailableForFutureIssuanceUnderSEPA_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Shares available for future issuance under the SEPA</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">Cash flows from operating activities</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="bcab_PaymentsForTaxesRelatedToNetSettlementOfEquityAwards1_lbl" xlink:role="http://www.xbrl.org/2009/role/negatedLabel">Payments for taxes related to net settlement of equity awards</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="bcab_PaymentsForTaxesRelatedToNetSettlementOfEquityAwards1_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Payments for taxes related to net settlement of equity awards</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="bcab_PaymentsForTaxesRelatedToNetSettlementOfEquityAwards1_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Payments for taxes related to net settlement of equity awards1</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="bcab_PaymentsForTaxesRelatedToNetSettlementOfEquityAwards1_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Payments For Taxes Related To Net Settlement Of Equity Awards1</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="bcab_ChangeInFairValueOfPre-PaidAdvanceAgreement_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Change in Fair Value of Pre-Paid Advance Agreement</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="bcab_ChangeInFairValueOfPre-PaidAdvanceAgreement_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Change in Fair Value of Pre-Paid Advance Agreement</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="bcab_ChangeInFairValueOfPre-PaidAdvanceAgreement_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Change in fair value of PPAs</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="bcab_DueToRelatedParty_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Due to Related Party</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="bcab_DueToRelatedParty_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Due to Related Party</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="bcab_DueToRelatedParty_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Due to related party</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="bcab_FairValueWarrantLiability_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Fair Value Warrant Liability</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="bcab_FairValueWarrantLiability_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Fair Value Warrant Liability</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="bcab_FairValueWarrantLiability_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Warrants</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="bcab_LicenseAgreementPaybleAmount_lbl" xlink:role="http://www.xbrl.org/2003/role/label">License Agreement Payble Amount</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="bcab_LicenseAgreementPaybleAmount_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">License Agreement Payble Amount</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="bcab_LicenseAgreementPaybleAmount_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">License agreement payble amount</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="bcab_SharesAvailableForFutureConversions_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Shares Available For Future Conversions</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="bcab_SharesAvailableForFutureConversions_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Shares Available For Future Conversions</link:label>
          <link:label xml:lang="en-US" xlink:type="resource" xlink:label="bcab_SharesAvailableForFutureConversions_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Shares available for future conversions of PPAs</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">Proceeds from sale common of stock</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>
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  <xsd:element id="bcab_EmployeesStockPurchasePlanMember" name="EmployeesStockPurchasePlanMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="bcab_AmendmentEffectiveDate" name="AmendmentEffectiveDate" type="xbrli:dateItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false"/>
  <xsd:element id="bcab_OzuriftamabVedotinBAThreeZeroTwoOneMember" name="OzuriftamabVedotinBAThreeZeroTwoOneMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="bcab_CompensationCostForTheModifiedUnvestedRestrictedStockUnits" name="CompensationCostForTheModifiedUnvestedRestrictedStockUnits" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false" xbrli:balance="debit"/>
  <xsd:element id="bcab_NumberOfShareSold" name="NumberOfShareSold" type="xbrli:sharesItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false"/>
  <xsd:element id="bcab_ClassOfWarrantExercisePriceAsAdjusted" name="ClassOfWarrantExercisePriceAsAdjusted" type="dtr-types:perShareItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false"/>
  <xsd:element id="bcab_PlacementAgentFees" name="PlacementAgentFees" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="instant" nillable="true" abstract="false" xbrli:balance="debit"/>
  <xsd:element id="bcab_CommonSockOtionsMember" name="CommonSockOtionsMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="bcab_EvalstotugBAThreeZeroSevenOneMember" name="EvalstotugBAThreeZeroSevenOneMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="bcab_TotalProgramExpensesMember" name="TotalProgramExpensesMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="bcab_NumberOfModifiedFullyVestedOptions" name="NumberOfModifiedFullyVestedOptions" type="xbrli:sharesItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false"/>
  <xsd:element id="bcab_PercentageOfOutstandingCommonStock" name="PercentageOfOutstandingCommonStock" type="dtr-types:percentItemType" substitutionGroup="xbrli:item" xbrli:periodType="instant" nillable="true" abstract="false"/>
  <xsd:element id="bcab_LicenseTerminationInformationDescription" name="LicenseTerminationInformationDescription" type="xbrli:stringItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false"/>
  <xsd:element id="bcab_ScheduleOfPrepaidExpensesOtherCurrentAssetsTableTextBlock" name="ScheduleOfPrepaidExpensesOtherCurrentAssetsTableTextBlock" type="dtr-types:textBlockItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false"/>
  <xsd:element id="bcab_EquityBasedCompensationMember" name="EquityBasedCompensationMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="bcab_ScheduleOfTheChangesInTheFairValueOfLiabilitiesTableTextBlock" name="ScheduleOfTheChangesInTheFairValueOfLiabilitiesTableTextBlock" type="dtr-types:textBlockItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false"/>
  <xsd:element id="bcab_CompanyFormationDate" name="CompanyFormationDate" type="xbrli:gYearMonthItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false"/>
  <xsd:element id="bcab_IssuanceOfCommonStockUnderStandbyEquityPurchaseAgreementValue" name="IssuanceOfCommonStockUnderStandbyEquityPurchaseAgreementValue" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false" xbrli:balance="debit"/>
  <xsd:element id="bcab_Pre-PaidAdvanceAgreementPPAsMember" name="Pre-PaidAdvanceAgreementPPAsMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="bcab_CommonStockWarrantsMember" name="CommonStockWarrantsMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="bcab_DescriptionOfAgreementWithRelatedParty" name="DescriptionOfAgreementWithRelatedParty" type="xbrli:stringItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false"/>
  <xsd:element id="bcab_MilestonePaymentReceived" name="MilestonePaymentReceived" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="instant" nillable="true" abstract="false" xbrli:balance="debit"/>
  <xsd:element id="bcab_HimalayaTherapeuticsSEZCMember" name="HimalayaTherapeuticsSEZCMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="bcab_LessorOperatingLeasesOptionToExtend" name="LessorOperatingLeasesOptionToExtend" type="xbrli:durationItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false"/>
  <xsd:element id="bcab_EXUMAMember" name="EXUMAMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="bcab_OrganizationAndSummaryOfSignificantAccountingPoliciesTable" name="OrganizationAndSummaryOfSignificantAccountingPoliciesTable" type="xbrli:stringItemType" substitutionGroup="xbrldt:hypercubeItem" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="bcab_ProfitsInterestIncentivePlanTextBlock" name="ProfitsInterestIncentivePlanTextBlock" type="dtr-types:textBlockItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false"/>
  <xsd:element id="bcab_TaxesrelatedtonetsharesettlementofequityawardsShares" name="TaxesrelatedtonetsharesettlementofequityawardsShares" type="xbrli:sharesItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false"/>
  <xsd:element id="bcab_NumberOfRsusUnvestedOnModificationDateNumberOfShares" name="NumberOfRsusUnvestedOnModificationDateNumberOfShares" type="xbrli:sharesItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false"/>
  <xsd:element id="bcab_MecbotamabVedotinBAThreeZeroOneOneMember" name="MecbotamabVedotinBAThreeZeroOneOneMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="bcab_RsusUnvestedOnModificationDateNumberOfShares" name="RsusUnvestedOnModificationDateNumberOfShares" type="xbrli:sharesItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false"/>
  <xsd:element id="bcab_StandbyEquityPurchaseAgreementMember" name="StandbyEquityPurchaseAgreementMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="bcab_TotalNumberOfModifiedUnvestedOptions" name="TotalNumberOfModifiedUnvestedOptions" type="xbrli:sharesItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false"/>
  <xsd:element id="bcab_AwardsAvailableForFutureIssuanceUnderTheTwoThousandTwentyPlan" name="AwardsAvailableForFutureIssuanceUnderTheTwoThousandTwentyPlan" type="xbrli:sharesItemType" substitutionGroup="xbrli:item" xbrli:periodType="instant" nillable="true" abstract="false"/>
  <xsd:element id="bcab_StockIssuedDuringPeriodSharesConversionOfClassBCommonStock" name="StockIssuedDuringPeriodSharesConversionOfClassBCommonStock" type="xbrli:sharesItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false"/>
  <xsd:element id="bcab_DecemberTwoThousandTwentyFourMember" name="DecemberTwoThousandTwentyFourMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="bcab_GainLossOnWarrantLiability" name="GainLossOnWarrantLiability" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false" xbrli:balance="credit"/>
  <xsd:element id="bcab_MergerAndRelatedShareConsolidationPolicyTextBlock" name="MergerAndRelatedShareConsolidationPolicyTextBlock" type="dtr-types:textBlockItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false"/>
  <xsd:element id="bcab_ScheduleOfTheChangeInTheFairValueOfPPAsLiabilitiesTableTextBlock" name="ScheduleOfTheChangeInTheFairValueOfPPAsLiabilitiesTableTextBlock" type="dtr-types:textBlockItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false"/>
  <xsd:element id="bcab_CompensationExpenseOnIssuanceOfDirectorCompensation" name="CompensationExpenseOnIssuanceOfDirectorCompensation" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false" xbrli:balance="credit"/>
  <xsd:element id="bcab_UpfrontNonRefundablePayment" name="UpfrontNonRefundablePayment" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false" xbrli:balance="credit"/>
  <xsd:element id="bcab_AmendedBeiGeneCollaborationMember" name="AmendedBeiGeneCollaborationMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="bcab_AccruedSeveranceIncludedInAccountsPayableAndAccruedExpenses" name="AccruedSeveranceIncludedInAccountsPayableAndAccruedExpenses" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false" xbrli:balance="debit"/>
  <xsd:element id="bcab_WarrantForThePurchaseOfCommonStock" name="WarrantForThePurchaseOfCommonStock" type="xbrli:sharesItemType" substitutionGroup="xbrli:item" xbrli:periodType="instant" nillable="true" abstract="false"/>
  <xsd:element id="bcab_RecalculatedCompensationCostOnTheModifiedRsus" name="RecalculatedCompensationCostOnTheModifiedRsus" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false" xbrli:balance="debit"/>
  <xsd:element id="bcab_SharesAvailableForAwardsDescription" name="SharesAvailableForAwardsDescription" type="xbrli:stringItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false"/>
  <xsd:element id="bcab_AmendedLicenseAgreementFirstPayableAmount" name="AmendedLicenseAgreementFirstPayableAmount" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="instant" nillable="true" abstract="false" xbrli:balance="debit"/>
  <xsd:element id="bcab_DebtInstrumentCarryingAmountPercentageOfFaceAmount" name="DebtInstrumentCarryingAmountPercentageOfFaceAmount" type="dtr-types:percentItemType" substitutionGroup="xbrli:item" xbrli:periodType="instant" nillable="true" abstract="false"/>
  <xsd:element id="bcab_IssuanceOfCommonStockForDirectorCompensationValue" name="IssuanceOfCommonStockForDirectorCompensationValue" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false" xbrli:balance="credit"/>
  <xsd:element id="bcab_LicenseAgreementPaybleAmount" name="LicenseAgreementPaybleAmount" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="instant" nillable="true" abstract="false" xbrli:balance="debit"/>
  <xsd:element id="bcab_FairValueOfCommonStockRelatedToPre-PaidAdvanceAgreementLiabiliity" name="FairValueOfCommonStockRelatedToPre-PaidAdvanceAgreementLiabiliity" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false" xbrli:balance="debit"/>
  <xsd:element id="bcab_PrepaidResearchAndDevelopmentExpense" name="PrepaidResearchAndDevelopmentExpense" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="instant" nillable="true" abstract="false" xbrli:balance="debit"/>
  <xsd:element id="bcab_Pre-PaidAdvanceAgreementLiability" name="Pre-PaidAdvanceAgreementLiability" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="instant" nillable="true" abstract="false" xbrli:balance="credit"/>
  <xsd:element id="bcab_AccruedResearchAndDevelopmentExpenseCurrent" name="AccruedResearchAndDevelopmentExpenseCurrent" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="instant" nillable="true" abstract="false" xbrli:balance="credit"/>
  <xsd:element id="bcab_GainLossOnPre-PaidAdvanceAgreementLiability" name="GainLossOnPre-PaidAdvanceAgreementLiability" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false" xbrli:balance="credit"/>
  <xsd:element id="bcab_TaxRelatedToNetSettlementOfEquityAwardIncludedInAccountsPayableAndAccruedExpenses" name="TaxRelatedToNetSettlementOfEquityAwardIncludedInAccountsPayableAndAccruedExpenses" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false" xbrli:balance="debit"/>
  <xsd:element id="bcab_LiquidityAndGoingConcernPolicyTextBlock" name="LiquidityAndGoingConcernPolicyTextBlock" type="dtr-types:textBlockItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false"/>
  <xsd:element id="bcab_ScheduleOfCommonStockReservedForFutureIssuanceTableTextBlock" name="ScheduleOfCommonStockReservedForFutureIssuanceTableTextBlock" type="dtr-types:textBlockItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false"/>
  <xsd:element id="bcab_EffectiveBusinessDays" name="EffectiveBusinessDays" type="xbrli:durationItemType" substitutionGroup="xbrli:item" xbrli:periodType="instant" nillable="true" abstract="false"/>
  <xsd:element id="bcab_SharesAvailableForFutureIssuanceUnderSEPA" name="SharesAvailableForFutureIssuanceUnderSEPA" type="xbrli:sharesItemType" substitutionGroup="xbrli:item" xbrli:periodType="instant" nillable="true" abstract="false"/>
  <xsd:element id="bcab_RestructuringCostsTable" name="RestructuringCostsTable" type="xbrli:stringItemType" substitutionGroup="xbrldt:hypercubeItem" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="bcab_OrganizationAndSummaryOfSignificantAccountingPoliciesLineItems" name="OrganizationAndSummaryOfSignificantAccountingPoliciesLineItems" type="xbrli:stringItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="bcab_RestructuringCostsLineItems" name="RestructuringCostsLineItems" type="xbrli:stringItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="bcab_Pre-PaidAdvance" name="Pre-PaidAdvance" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false" xbrli:balance="credit"/>
  <xsd:element id="bcab_CollaborationLicenseAndOptionAgreementsAbstract" name="CollaborationLicenseAndOptionAgreementsAbstract" type="xbrli:stringItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="bcab_AggregateGrossProceeds" name="AggregateGrossProceeds" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false" xbrli:balance="credit"/>
  <xsd:element id="bcab_IssuanceOfCommonStockUnderPre-PaidAdvanceAgreementShares" name="IssuanceOfCommonStockUnderPre-PaidAdvanceAgreementShares" type="xbrli:sharesItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false"/>
  <xsd:element id="bcab_AmendmentLicenseAgreementSecondMember" name="AmendmentLicenseAgreementSecondMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="bcab_ProceedsFromIssuanceOfCommonStockUnderStandByEquityPurchaseAgreementNet" name="ProceedsFromIssuanceOfCommonStockUnderStandByEquityPurchaseAgreementNet" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false" xbrli:balance="debit"/>
  <xsd:element id="bcab_DebtInstrumentOutstandingPrincipalAmount" name="DebtInstrumentOutstandingPrincipalAmount" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="instant" nillable="true" abstract="false" xbrli:balance="debit"/>
  <xsd:element id="bcab_NumberOfOptionsUnvestedOnModificationDateNumberOfShares" name="NumberOfOptionsUnvestedOnModificationDateNumberOfShares" type="xbrli:sharesItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false"/>
  <xsd:element id="bcab_TaxesRelatedToNetShareSettlementOfEquityAwards" name="TaxesRelatedToNetShareSettlementOfEquityAwards" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false" xbrli:balance="debit"/>
  <xsd:element id="bcab_FairValueWarrantLiability" name="FairValueWarrantLiability" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false" xbrli:balance="credit"/>
  <xsd:element id="bcab_PrivatePlacementOfCommonStockMember" name="PrivatePlacementOfCommonStockMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="bcab_RestructuringChargesIncludedInAccountsPayableAndAccruedExpenses" name="RestructuringChargesIncludedInAccountsPayableAndAccruedExpenses" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false" xbrli:balance="debit"/>
  <xsd:element id="bcab_ExclusiveLicenseAgreementWithEXUMABiotechCorpTextBlock" name="ExclusiveLicenseAgreementWithEXUMABiotechCorpTextBlock" type="dtr-types:textBlockItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false"/>
  <xsd:element id="bcab_StandbyEquityPurchaseAgreementFees" name="StandbyEquityPurchaseAgreementFees" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false" xbrli:balance="credit"/>
  <xsd:element id="bcab_PercentageOfAnnualIncreasedShares" name="PercentageOfAnnualIncreasedShares" type="dtr-types:percentItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false"/>
  <xsd:element id="bcab_IssuanceOfCommonStockUnderStandbyEquityPurchaseAgreementShares" name="IssuanceOfCommonStockUnderStandbyEquityPurchaseAgreementShares" type="xbrli:sharesItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false"/>
  <xsd:element id="bcab_ChangeInFairValueOfPre-PaidAdvance" name="ChangeInFairValueOfPre-PaidAdvance" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false" xbrli:balance="debit"/>
  <xsd:element id="bcab_CommonSharesAuthorizedForIssuance" name="CommonSharesAuthorizedForIssuance" type="xbrli:sharesItemType" substitutionGroup="xbrli:item" xbrli:periodType="instant" nillable="true" abstract="false"/>
  <xsd:element id="bcab_BAThreeOneEightTwoMember" name="BAThreeOneEightTwoMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="bcab_RecalculatedCompensationCostOfTheModifiedOptions" name="RecalculatedCompensationCostOfTheModifiedOptions" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false" xbrli:balance="credit"/>
  <xsd:element id="bcab_WarrantLiability" name="WarrantLiability" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="instant" nillable="true" abstract="false" xbrli:balance="credit"/>
  <xsd:element id="bcab_OtherPrepaidExpensesAndCurrentAssets" name="OtherPrepaidExpensesAndCurrentAssets" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="instant" nillable="true" abstract="false" xbrli:balance="debit"/>
  <xsd:element id="bcab_ContextTherapeuticsIncMember" name="ContextTherapeuticsIncMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="bcab_ClassOfWarrantOrRightOutstandingAndExercisable" name="ClassOfWarrantOrRightOutstandingAndExercisable" type="xbrli:sharesItemType" substitutionGroup="xbrli:item" xbrli:periodType="instant" nillable="true" abstract="false"/>
  <xsd:element id="bcab_LiquidityAndGoingConcernMember" name="LiquidityAndGoingConcernMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="bcab_CommonStockOptionsAndRestrictedStockUnitsMember" name="CommonStockOptionsAndRestrictedStockUnitsMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="bcab_UnpaidDeferredFinancingCost" name="UnpaidDeferredFinancingCost" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false" xbrli:balance="debit"/>
</xsd:schema>
