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    <element id="bcab_PaidAdvanceRemainingPrincipalAmount" name="PaidAdvanceRemainingPrincipalAmount" nillable="true" xbrli:periodType="instant" xbrli:balance="debit" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" />
    <element id="bcab_DefaultInterestRatePercentage" name="DefaultInterestRatePercentage" nillable="true" xbrli:periodType="instant" type="dtr-types:percentItemType" substitutionGroup="xbrli:item" />
    <element id="bcab_DebtInstrumentPrepaymentPremiumPercentage" name="DebtInstrumentPrepaymentPremiumPercentage" nillable="true" xbrli:periodType="instant" type="dtr-types:percentItemType" substitutionGroup="xbrli:item" />
    <element id="bcab_PrePaidAdvanceVolumeWeightedAveragePricePercent" name="PrePaidAdvanceVolumeWeightedAveragePricePercent" nillable="true" xbrli:periodType="instant" type="dtr-types:percentItemType" substitutionGroup="xbrli:item" />
    <element id="bcab_PercentageOfOutstandingCommonStock" name="PercentageOfOutstandingCommonStock" nillable="true" xbrli:periodType="instant" type="dtr-types:percentItemType" substitutionGroup="xbrli:item" />
    <element id="bcab_PrePaidAdvanceAgreementsAmortizationEventDescripton" name="PrePaidAdvanceAgreementsAmortizationEventDescripton" nillable="true" xbrli:periodType="duration" type="xbrli:stringItemType" substitutionGroup="xbrli:item" />
    <element id="bcab_PrePaidAdvanceRemainingPrincipalAmount" name="PrePaidAdvanceRemainingPrincipalAmount" nillable="true" xbrli:periodType="instant" xbrli:balance="debit" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" />
    <element id="bcab_WarrantForThePurchaseOfCommonStock" name="WarrantForThePurchaseOfCommonStock" nillable="true" xbrli:periodType="instant" type="xbrli:sharesItemType" substitutionGroup="xbrli:item" />
    <element id="bcab_AwardsAvailableForFutureIssuanceUnderTheTwoThousandTwentyPlan" name="AwardsAvailableForFutureIssuanceUnderTheTwoThousandTwentyPlan" nillable="true" xbrli:periodType="instant" type="xbrli:sharesItemType" substitutionGroup="xbrli:item" />
    <element id="bcab_AwardsAvailableForFutureIssuanceUnderTheESPP" name="AwardsAvailableForFutureIssuanceUnderTheESPP" nillable="true" xbrli:periodType="instant" type="xbrli:sharesItemType" substitutionGroup="xbrli:item" />
    <element id="bcab_SharesAvailableForFutureConversionsOfPpas" name="SharesAvailableForFutureConversionsOfPpas" nillable="true" xbrli:periodType="instant" type="xbrli:sharesItemType" substitutionGroup="xbrli:item" />
    <element id="bcab_PercentageOfAverageDailyTradingVolume" name="PercentageOfAverageDailyTradingVolume" nillable="true" xbrli:periodType="instant" type="dtr-types:percentItemType" substitutionGroup="xbrli:item" />
    <element id="bcab_StandbyEquityPurchaseAgreementFees" name="StandbyEquityPurchaseAgreementFees" nillable="true" xbrli:periodType="duration" xbrli:balance="credit" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" />
    <element id="bcab_NumberOfShareSold" name="NumberOfShareSold" nillable="true" xbrli:periodType="duration" type="xbrli:sharesItemType" substitutionGroup="xbrli:item" />
    <element id="bcab_ClassOfWarrantExercisePriceAsAdjusted" name="ClassOfWarrantExercisePriceAsAdjusted" nillable="true" xbrli:periodType="duration" type="dtr-types:perShareItemType" substitutionGroup="xbrli:item" />
    <element id="bcab_ClassOfWarrantOrRightOutstandingAndExercisable" name="ClassOfWarrantOrRightOutstandingAndExercisable" nillable="true" xbrli:periodType="instant" type="xbrli:sharesItemType" substitutionGroup="xbrli:item" />
    <element id="bcab_PercentageOfAnnualIncreasedShares" name="PercentageOfAnnualIncreasedShares" nillable="true" xbrli:periodType="duration" type="dtr-types:percentItemType" substitutionGroup="xbrli:item" />
    <element id="bcab_PeriodRelatedToChangingOfOwnershipLimitationPercentageDesignatedByClassBCommonStockHolder" name="PeriodRelatedToChangingOfOwnershipLimitationPercentageDesignatedByClassBCommonStockHolder" nillable="true" xbrli:periodType="duration" type="xbrli:durationItemType" substitutionGroup="xbrli:item" />
    <element id="bcab_PercentageOfOutstandingCommonStockForExchangeCap" name="PercentageOfOutstandingCommonStockForExchangeCap" nillable="true" xbrli:periodType="instant" type="dtr-types:percentItemType" substitutionGroup="xbrli:item" />
    <element id="bcab_AggregateGrossProceeds" name="AggregateGrossProceeds" nillable="true" xbrli:periodType="duration" xbrli:balance="credit" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" />
    <element id="bcab_PlacementAgentFees" name="PlacementAgentFees" nillable="true" xbrli:periodType="instant" xbrli:balance="debit" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" />
    <element id="bcab_CommonSharesAuthorizedForIssuance" name="CommonSharesAuthorizedForIssuance" nillable="true" xbrli:periodType="instant" type="xbrli:sharesItemType" substitutionGroup="xbrli:item" />
    <element id="bcab_UpfrontNonRefundablePayment" name="UpfrontNonRefundablePayment" nillable="true" xbrli:periodType="duration" xbrli:balance="credit" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" />
    <element id="bcab_MaximumPotentialAggregatePayments" name="MaximumPotentialAggregatePayments" nillable="true" xbrli:periodType="instant" xbrli:balance="credit" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" />
    <element id="bcab_AmendedLicenseAgreementFirstPayableAmount" name="AmendedLicenseAgreementFirstPayableAmount" nillable="true" xbrli:periodType="instant" xbrli:balance="debit" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" />
    <element id="bcab_AmendedLicenseAgreementSecondPayableAmount" name="AmendedLicenseAgreementSecondPayableAmount" nillable="true" xbrli:periodType="instant" xbrli:balance="debit" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" />
    <element id="bcab_CollaborationAgreementStartDate" name="CollaborationAgreementStartDate" nillable="true" xbrli:periodType="duration" type="xbrli:durationItemType" substitutionGroup="xbrli:item" />
    <element id="bcab_DescriptionOfAgreementWithRelatedParty" name="DescriptionOfAgreementWithRelatedParty" nillable="true" xbrli:periodType="duration" type="xbrli:stringItemType" substitutionGroup="xbrli:item" />
    <element id="bcab_DueToRelatedParty" name="DueToRelatedParty" nillable="true" xbrli:periodType="instant" xbrli:balance="debit" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" />
    <element id="bcab_OptionsGrantsRelatedToRoyaltyPaymentPeriod" name="OptionsGrantsRelatedToRoyaltyPaymentPeriod" nillable="true" xbrli:periodType="duration" type="xbrli:durationItemType" substitutionGroup="xbrli:item" />
    <element id="bcab_ShareOfRoyaltiesUnderRoyaltySharingAgreement" name="ShareOfRoyaltiesUnderRoyaltySharingAgreement" nillable="true" xbrli:periodType="instant" type="dtr-types:percentItemType" substitutionGroup="xbrli:item" />
    <element id="bcab_SharebasedCompensationArrangementBySharebasedPaymentAwardFairValueAssumptionsExpectedTerm" name="SharebasedCompensationArrangementBySharebasedPaymentAwardFairValueAssumptionsExpectedTerm" nillable="true" xbrli:periodType="duration" type="xbrli:durationItemType" substitutionGroup="xbrli:item" />
    <element id="bcab_AmendedLicenseAgreementPaymentReceived" name="AmendedLicenseAgreementPaymentReceived" nillable="true" xbrli:periodType="instant" xbrli:balance="credit" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" />
    <element id="bcab_SaleOfStockMaximumCommitmentAmount" name="SaleOfStockMaximumCommitmentAmount" nillable="true" xbrli:periodType="instant" xbrli:balance="credit" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" />
    <element id="bcab_CommitmentFeeAmount" name="CommitmentFeeAmount" nillable="true" xbrli:periodType="instant" xbrli:balance="credit" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" />
    <element id="bcab_EffectiveIncomeTaxRateReconciliationTaxCreditOrphanDrugCeditAmount" name="EffectiveIncomeTaxRateReconciliationTaxCreditOrphanDrugCeditAmount" nillable="true" xbrli:periodType="duration" xbrli:balance="credit" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" />
    <element id="bcab_EffectiveIncomeTaxRateReconciliationTaxCreditOrphanDrugCreditPercent" name="EffectiveIncomeTaxRateReconciliationTaxCreditOrphanDrugCreditPercent" nillable="true" xbrli:periodType="duration" type="dtr-types:percentItemType" substitutionGroup="xbrli:item" />
    <element id="bcab_EffectiveIncomeTaxRateReconciliationNondeductibleExpensePermanentItemsAmount" name="EffectiveIncomeTaxRateReconciliationNondeductibleExpensePermanentItemsAmount" nillable="true" xbrli:periodType="duration" xbrli:balance="debit" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" />
    <element id="bcab_EffectiveIncomeTaxRateReconciliationNondeductibleExpensePermanentItemsPercent" name="EffectiveIncomeTaxRateReconciliationNondeductibleExpensePermanentItemsPercent" nillable="true" xbrli:periodType="duration" type="dtr-types:percentItemType" substitutionGroup="xbrli:item" />
    <element id="bcab_LeaseLiability" name="LeaseLiability" nillable="true" xbrli:periodType="instant" xbrli:balance="debit" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" />
    <element id="bcab_Section174CostCapitalization" name="Section174CostCapitalization" nillable="true" xbrli:periodType="instant" xbrli:balance="debit" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" />
    <element id="bcab_Section59ECostCapitalization" name="Section59ECostCapitalization" nillable="true" xbrli:periodType="instant" xbrli:balance="debit" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" />
    <element id="bcab_DeferredTaxAssetsFixedAssets" name="DeferredTaxAssetsFixedAssets" nillable="true" xbrli:periodType="instant" xbrli:balance="debit" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" />
    <element id="bcab_FederalNetOperatingLossCarryforward" name="FederalNetOperatingLossCarryforward" nillable="true" xbrli:periodType="duration" xbrli:balance="debit" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" />
    <element id="bcab_StateNetOperatingLossCarryforwards" name="StateNetOperatingLossCarryforwards" nillable="true" xbrli:periodType="duration" xbrli:balance="debit" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" />
    <element id="bcab_TaxCreditCarryforwardExpirationPeriod" name="TaxCreditCarryforwardExpirationPeriod" nillable="true" xbrli:periodType="duration" type="xbrli:durationItemType" substitutionGroup="xbrli:item" />
    <element id="bcab_OrphanDrugCredit" name="OrphanDrugCredit" nillable="true" xbrli:periodType="duration" xbrli:balance="debit" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" />
    <element id="bcab_OrphanDrugCreditCarryforwardsExpirationPeriod" name="OrphanDrugCreditCarryforwardsExpirationPeriod" nillable="true" xbrli:periodType="duration" type="xbrli:durationItemType" substitutionGroup="xbrli:item" />
    <element id="bcab_AnnualOperatingLossCarryforwardsUse" name="AnnualOperatingLossCarryforwardsUse" nillable="true" xbrli:periodType="duration" type="xbrli:stringItemType" substitutionGroup="xbrli:item" />
    <element id="bcab_PaidAdvanceAgreementLiability" name="PaidAdvanceAgreementLiability" nillable="true" xbrli:periodType="instant" xbrli:balance="credit" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" />
    <element id="bcab_ResearchAndDevelopmentExpensesMember" name="ResearchAndDevelopmentExpensesMember" nillable="true" xbrli:periodType="duration" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" />
    <element id="bcab_AccruedResearchAndDevelopment" name="AccruedResearchAndDevelopment" nillable="true" xbrli:periodType="instant" xbrli:balance="credit" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" />
    <element id="bcab_WarrantLiabilityMember" name="WarrantLiabilityMember" nillable="true" xbrli:periodType="duration" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" />
    <element id="bcab_PPAsLiabilityMember" name="PPAsLiabilityMember" nillable="true" xbrli:periodType="duration" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" />
    <element id="bcab_ClassOfStockAxis" name="ClassOfStockAxis" abstract="true" nillable="true" xbrli:periodType="duration" type="xbrli:stringItemType" substitutionGroup="xbrldt:dimensionItem" />
    <element id="bcab_DerivativeInstrumentAxis" name="DerivativeInstrumentAxis" abstract="true" nillable="true" xbrli:periodType="duration" type="xbrli:stringItemType" substitutionGroup="xbrldt:dimensionItem" />
    <element id="bcab_EquityOptionMember" name="EquityOptionMember" nillable="true" xbrli:periodType="duration" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" />
    <element id="bcab_HimalayaMember" name="HimalayaMember" nillable="true" xbrli:periodType="duration" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" />
</schema>
