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  <xs:element id="bcax_InvestmentCategorizationAxisDomain" abstract="true" name="InvestmentCategorizationAxisDomain" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="bcax_InvestmentsWithMaturityOfOneYearOrLessMember" abstract="true" name="InvestmentsWithMaturityOfOneYearOrLessMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="bcax_InvestmentsWithMaturityOfOneToTwoYearsMember" abstract="true" name="InvestmentsWithMaturityOfOneToTwoYearsMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="bcax_DebtSecuritiesAvailableForSaleNumberOfSecuritiesInUnrealizedLossPosition" abstract="false" name="DebtSecuritiesAvailableForSaleNumberOfSecuritiesInUnrealizedLossPosition" nillable="true" xbrli:periodType="instant" substitutionGroup="xbrli:item" type="xbrli:integerItemType"/>
  <xs:element id="bcax_LesseeOperatingLeaseArea" abstract="false" name="LesseeOperatingLeaseArea" nillable="true" xbrli:periodType="instant" substitutionGroup="xbrli:item" type="dtr-types:areaItemType"/>
  <xs:element id="bcax_AccruedResearchAndDevelopmentExpenseCurrent" abstract="false" name="AccruedResearchAndDevelopmentExpenseCurrent" nillable="true" xbrli:periodType="instant" xbrli:balance="credit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="bcax_AccruedManufacturingExpensesCurrent" abstract="false" name="AccruedManufacturingExpensesCurrent" nillable="true" xbrli:periodType="instant" xbrli:balance="credit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="bcax_ClassOfWarrantOrRightCommonStockExercisePriceOfWarrantsOrRightsDifference" abstract="false" name="ClassOfWarrantOrRightCommonStockExercisePriceOfWarrantsOrRightsDifference" nillable="true" xbrli:periodType="instant" substitutionGroup="xbrli:item" type="dtr-types:perShareItemType"/>
  <xs:element id="bcax_SaleOfStockCommissionFeePercentage" abstract="false" name="SaleOfStockCommissionFeePercentage" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:percentItemType"/>
  <xs:element id="bcax_A2024StockOptionAndGrantPlanMember" abstract="true" name="A2024StockOptionAndGrantPlanMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="bcax_A2026InducementPlanMember" abstract="true" name="A2026InducementPlanMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="bcax_IncentiveStockOptionsAndNonQualifiedStockOptionsMember" abstract="true" name="IncentiveStockOptionsAndNonQualifiedStockOptionsMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="bcax_ShareBasedCompensationArrangementByShareBasedPaymentAwardAutomaticShareAuthorizationIncreasePercentage" abstract="false" name="ShareBasedCompensationArrangementByShareBasedPaymentAwardAutomaticShareAuthorizationIncreasePercentage" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:percentItemType"/>
  <xs:element id="bcax_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfAdditionalSharesAllowableUnderThePlan" abstract="false" name="ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfAdditionalSharesAllowableUnderThePlan" nillable="true" xbrli:periodType="instant" substitutionGroup="xbrli:item" type="xbrli:sharesItemType"/>
  <xs:element id="bcax_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsDuringPeriodExercisePrice" abstract="false" name="ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsDuringPeriodExercisePrice" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:perShareItemType"/>
  <xs:element id="bcax_MasterServicesAgreementMember" abstract="true" name="MasterServicesAgreementMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="bcax_BBLAgreementsMember" abstract="true" name="BBLAgreementsMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="bcax_SyngeneAgreementsMember" abstract="true" name="SyngeneAgreementsMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="bcax_IQVIARDSIncMember" abstract="true" name="IQVIARDSIncMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="bcax_MasterClinicalContractServicesAgreementMember" abstract="true" name="MasterClinicalContractServicesAgreementMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="bcax_MasterClinicalContractServicesAgreementRefundableDepositMember" abstract="true" name="MasterClinicalContractServicesAgreementRefundableDepositMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="bcax_MasterClinicalServicesAgreementInvestigatorGrantPaymentMember" abstract="true" name="MasterClinicalServicesAgreementInvestigatorGrantPaymentMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="bcax_MasterClinicalContractServicesAgreementAdditionalRefundableDepositMember" abstract="true" name="MasterClinicalContractServicesAgreementAdditionalRefundableDepositMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="bcax_MasterClinicalContractServicesAgreementDepositsForServicesMember" abstract="true" name="MasterClinicalContractServicesAgreementDepositsForServicesMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="bcax_MasterClinicalContractServicesAgreementDepositForPassThroughCostsMember" abstract="true" name="MasterClinicalContractServicesAgreementDepositForPassThroughCostsMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="bcax_MasterClinicalContractServicesAgreementIncrementalReturnMember" abstract="true" name="MasterClinicalContractServicesAgreementIncrementalReturnMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="bcax_OtherCommitmentLiabilityRefundableDepositAmount" abstract="false" name="OtherCommitmentLiabilityRefundableDepositAmount" nillable="true" xbrli:periodType="instant" xbrli:balance="debit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="bcax_OtherCommitmentPercentage" abstract="false" name="OtherCommitmentPercentage" nillable="true" xbrli:periodType="instant" substitutionGroup="xbrli:item" type="xbrli:pureItemType"/>
  <xs:element id="bcax_PaymentsForOtherCommitments" abstract="false" name="PaymentsForOtherCommitments" nillable="true" xbrli:periodType="duration" xbrli:balance="credit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="bcax_ReportableSegmentMember" abstract="true" name="ReportableSegmentMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="bcax_ClinicalOperationsAndDevelopmentExpense" abstract="false" name="ClinicalOperationsAndDevelopmentExpense" nillable="true" xbrli:periodType="duration" xbrli:balance="debit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="bcax_ManufacturingAndProcessDevelopmentExpense" abstract="false" name="ManufacturingAndProcessDevelopmentExpense" nillable="true" xbrli:periodType="duration" xbrli:balance="debit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="bcax_ResearchAndDevelopmentPersonnelCostIncludingShareBasedPaymentArrangementExpense" abstract="false" name="ResearchAndDevelopmentPersonnelCostIncludingShareBasedPaymentArrangementExpense" nillable="true" xbrli:periodType="duration" xbrli:balance="debit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="bcax_GeneralAndAdministrativePersonnelCostsIncludingStockBasedCompensation" abstract="false" name="GeneralAndAdministrativePersonnelCostsIncludingStockBasedCompensation" nillable="true" xbrli:periodType="duration" xbrli:balance="debit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="bcax_FacilityITOfficeAndOtherExpense" abstract="false" name="FacilityITOfficeAndOtherExpense" nillable="true" xbrli:periodType="duration" xbrli:balance="debit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="bcax_IncomeTaxExpenseBenefitIncludingAdjustments" abstract="false" name="IncomeTaxExpenseBenefitIncludingAdjustments" nillable="true" xbrli:periodType="duration" xbrli:balance="debit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="bcax_ClaireMazumdanMember" abstract="true" name="ClaireMazumdanMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="bcax_RyanCohlheppMember" abstract="true" name="RyanCohlheppMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="bcax_IvanHyepMember" abstract="true" name="IvanHyepMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="bcax_LaraMeisnerMember" abstract="true" name="LaraMeisnerMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="bcax_DavidRabenMember" abstract="true" name="DavidRabenMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
</xs:schema>
