<?xml version="1.0" encoding="utf-8"?>
<!--XBRL document created with Toppan Merrill Bridge  11.2.0.5 -->
<!--Based on XBRL 2.1-->
<!--Created on: 3/16/2026 10:36:50 PM-->
<!--Modified on: 3/16/2026 10:36:50 PM-->
<xsd:schema targetNamespace="http://www.bicycletherapeutics.com/20251231" attributeFormDefault="unqualified" elementFormDefault="qualified" xmlns:xsd="http://www.w3.org/2001/XMLSchema" xmlns:link="http://www.xbrl.org/2003/linkbase" xmlns:ref="http://www.xbrl.org/2006/ref" xmlns:xbrldt="http://xbrl.org/2005/xbrldt" xmlns:negated="http://www.xbrl.org/2009/role/negated" xmlns:xl="http://www.xbrl.org/2003/XLink" xmlns:us-gaap="http://fasb.org/us-gaap/2025" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:xbrli="http://www.xbrl.org/2003/instance" xmlns:country="http://xbrl.sec.gov/country/2025" xmlns:utr="http://www.xbrl.org/2009/utr" xmlns:xlink="http://www.w3.org/1999/xlink" xmlns:bcyc="http://www.bicycletherapeutics.com/20251231" xmlns:enum2="http://xbrl.org/2020/extensible-enumerations-2.0" xmlns:dtr-types="http://www.xbrl.org/dtr/type/2024-01-31" xmlns:us-roles="http://fasb.org/us-roles/2025" xmlns:attributeFormDefault="unqualified" xmlns:srt="http://fasb.org/srt/2025" xmlns:deprecated="http://www.xbrl.org/2009/role/deprecated" xmlns:net="http://www.xbrl.org/2009/role/net" xmlns:dei="http://xbrl.sec.gov/dei/2025" xmlns:dtr="http://www.xbrl.org/2009/dtr" xmlns:xbrldi="http://xbrl.org/2006/xbrldi" xmlns:ecd="http://xbrl.sec.gov/ecd/2025" xmlns:ecd-sub="http://xbrl.sec.gov/ecd-sub/2025" xmlns:cyd-af-sub="http://xbrl.sec.gov/cyd-af-sub/2025" xmlns:cyd="http://xbrl.sec.gov/cyd/2025">
  <xsd:annotation>
    <xsd:appinfo>
      <link:roleType roleURI="http://www.bicycletherapeutics.com/role/DisclosureStandardAndCustomAxisDomainDefaults" id="DisclosureStandardAndCustomAxisDomainDefaults">
        <link:definition>99900 - Disclosure - Standard And Custom Axis Domain Defaults</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType roleURI="http://www.bicycletherapeutics.com/role/StatementConsolidatedBalanceSheets" id="StatementConsolidatedBalanceSheets">
        <link:definition>995200100 - Statement - Consolidated Balance Sheets</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType roleURI="http://www.bicycletherapeutics.com/role/StatementConsolidatedStatementsOfOperationsAndComprehensiveLoss" id="StatementConsolidatedStatementsOfOperationsAndComprehensiveLoss">
        <link:definition>995200200 - Statement - Consolidated Statements of Operations and Comprehensive Loss</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType roleURI="http://www.bicycletherapeutics.com/role/StatementConsolidatedStatementsOfCashFlows" id="StatementConsolidatedStatementsOfCashFlows">
        <link:definition>995200400 - Statement - Consolidated Statements of Cash Flows</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType roleURI="http://www.bicycletherapeutics.com/role/DisclosurePropertyAndEquipmentNetDetails" id="DisclosurePropertyAndEquipmentNetDetails">
        <link:definition>99940401 - Disclosure - Property and equipment, net (Details)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType roleURI="http://www.bicycletherapeutics.com/role/DisclosureAccruedExpensesAndOtherCurrentLiabilitiesDetails" id="DisclosureAccruedExpensesAndOtherCurrentLiabilitiesDetails">
        <link:definition>99940501 - Disclosure - Accrued expenses and other current liabilities (Details)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType roleURI="http://www.bicycletherapeutics.com/role/DisclosureSignificantAgreementsRevenueRecognitionDueToChangesInContractAssetsAndLiabilitiesDetails" id="DisclosureSignificantAgreementsRevenueRecognitionDueToChangesInContractAssetsAndLiabilitiesDetails">
        <link:definition>99940912 - Disclosure - Significant agreements - Revenue recognition due to changes in contract assets and liabilities (Details)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType roleURI="http://www.bicycletherapeutics.com/role/DisclosureIncomeTaxesComponentsOfNetLossBeforeTaxProvisionFromIncomeTaxesDetails" id="DisclosureIncomeTaxesComponentsOfNetLossBeforeTaxProvisionFromIncomeTaxesDetails">
        <link:definition>99941001 - Disclosure - Income taxes - Components of net loss before tax provision from income taxes (Details)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType roleURI="http://www.bicycletherapeutics.com/role/DisclosureIncomeTaxesComponentsOfBenefitForIncomeTaxesDetails" id="DisclosureIncomeTaxesComponentsOfBenefitForIncomeTaxesDetails">
        <link:definition>99941002 - Disclosure - Income taxes - Components of benefit for income taxes (Details)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType roleURI="http://www.bicycletherapeutics.com/role/DisclosureIncomeTaxesReconciliationOfBenefitForIncomeTaxesDetails" id="DisclosureIncomeTaxesReconciliationOfBenefitForIncomeTaxesDetails">
        <link:definition>99941003 - Disclosure - Income taxes - Reconciliation of benefit for income taxes (Details)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType roleURI="http://www.bicycletherapeutics.com/role/DisclosureIncomeTaxesComponentsOfCompanySCurrentAndDeferredTaxAssetsDetails" id="DisclosureIncomeTaxesComponentsOfCompanySCurrentAndDeferredTaxAssetsDetails">
        <link:definition>99941004 - Disclosure - Income taxes - Components of the company's current and deferred tax assets (Details)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType roleURI="http://www.bicycletherapeutics.com/role/DisclosureIncomeTaxesCashPaidDetails" id="DisclosureIncomeTaxesCashPaidDetails">
        <link:definition>99941005 - Disclosure - Income taxes - Cash paid (Details)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType roleURI="http://www.bicycletherapeutics.com/role/DisclosureCommitmentsAndContingenciesComponentsOfLeaseExpenseDetails" id="DisclosureCommitmentsAndContingenciesComponentsOfLeaseExpenseDetails">
        <link:definition>99941102 - Disclosure - Commitments and contingencies - Components of lease expense (Details)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType roleURI="http://www.bicycletherapeutics.com/role/DisclosureCommitmentsAndContingenciesLeasesMaturitiesOfLeaseLiabilitiesCalc2" id="DisclosureCommitmentsAndContingenciesLeasesMaturitiesOfLeaseLiabilitiesCalc2">
        <link:definition>41103 - Disclosure - Commitments and contingencies - Leases, Maturities of Lease Liabilities Calc2</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType roleURI="http://www.bicycletherapeutics.com/role/DisclosureCommitmentsAndContingenciesLeasesMaturitiesOfOperatingLeasesDetails" id="DisclosureCommitmentsAndContingenciesLeasesMaturitiesOfOperatingLeasesDetails">
        <link:definition>99941103 - Disclosure - Commitments and contingencies - Leases, Maturities of Operating Leases (Details)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType roleURI="http://www.bicycletherapeutics.com/role/DisclosureSegmentsAndGeographicInformationSignificantSegmentExpensesDetails" id="DisclosureSegmentsAndGeographicInformationSignificantSegmentExpensesDetails">
        <link:definition>99941502 - Disclosure - Segments and geographic information - Significant segment expenses (Details)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType roleURI="http://www.bicycletherapeutics.com/role/DocumentDocumentAndEntityInformation" id="DocumentDocumentAndEntityInformation">
        <link:definition>995200090 - Document - Document and Entity Information</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType roleURI="http://www.bicycletherapeutics.com/role/StatementConsolidatedBalanceSheetsParenthetical" id="StatementConsolidatedBalanceSheetsParenthetical">
        <link:definition>995200105 - Statement - Consolidated Balance Sheets (Parenthetical)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType roleURI="http://www.bicycletherapeutics.com/role/StatementConsolidatedStatementsOfShareholdersEquity" id="StatementConsolidatedStatementsOfShareholdersEquity">
        <link:definition>995200300 - Statement - Consolidated Statements of Shareholders' Equity</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType roleURI="http://www.bicycletherapeutics.com/role/DisclosureShareBasedCompensationTables" id="DisclosureShareBasedCompensationTables">
        <link:definition>99930803 - Disclosure - Share-based compensation (Tables)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType roleURI="http://www.bicycletherapeutics.com/role/DisclosureSignificantAgreementsTables" id="DisclosureSignificantAgreementsTables">
        <link:definition>99930903 - Disclosure - Significant agreements (Tables)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType roleURI="http://www.bicycletherapeutics.com/role/DisclosureNatureOfBusinessAndBasisOfPresentationLiquidityDetails" id="DisclosureNatureOfBusinessAndBasisOfPresentationLiquidityDetails">
        <link:definition>99940101 - Disclosure - Nature of the business and basis of presentation - Liquidity (Details)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType roleURI="http://www.bicycletherapeutics.com/role/DisclosureNatureOfBusinessAndBasisOfPresentationShareActivityDetails" id="DisclosureNatureOfBusinessAndBasisOfPresentationShareActivityDetails">
        <link:definition>99940102 - Disclosure - Nature of the business and basis of presentation - Share activity (Details)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType roleURI="http://www.bicycletherapeutics.com/role/DisclosureSummaryOfSignificantAccountingPoliciesPropertyAndEquipmentGeographicDetails" id="DisclosureSummaryOfSignificantAccountingPoliciesPropertyAndEquipmentGeographicDetails">
        <link:definition>99940204 - Disclosure - Summary of significant accounting policies - Property and equipment, Geographic (Details)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType roleURI="http://www.bicycletherapeutics.com/role/DisclosureSummaryOfSignificantAccountingPoliciesResearchAndDevelopmentIncentivesAndReceivableDetails" id="DisclosureSummaryOfSignificantAccountingPoliciesResearchAndDevelopmentIncentivesAndReceivableDetails">
        <link:definition>99940205 - Disclosure - Summary of significant accounting policies - Research and development incentives and receivable (Details)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType roleURI="http://www.bicycletherapeutics.com/role/DisclosureFairValueOfFinancialAssetsAndLiabilitiesFinancialAssetsAndLiabilitiesMeasuredAtFairValueDetails" id="DisclosureFairValueOfFinancialAssetsAndLiabilitiesFinancialAssetsAndLiabilitiesMeasuredAtFairValueDetails">
        <link:definition>99940301 - Disclosure - Fair value of financial assets and liabilities - Financial assets and liabilities measured at fair value (Details)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType roleURI="http://www.bicycletherapeutics.com/role/DisclosureAccruedExpensesAndOtherCurrentLiabilitiesAdditionalInformationDetails" id="DisclosureAccruedExpensesAndOtherCurrentLiabilitiesAdditionalInformationDetails">
        <link:definition>99940502 - Disclosure - Accrued expenses and other current liabilities - Additional information (Details)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType roleURI="http://www.bicycletherapeutics.com/role/DisclosureDebtDetails" id="DisclosureDebtDetails">
        <link:definition>99940601 - Disclosure - Debt (Details)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType roleURI="http://www.bicycletherapeutics.com/role/DisclosureOrdinarySharesDetails" id="DisclosureOrdinarySharesDetails">
        <link:definition>99940701 - Disclosure - Ordinary shares (Details)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType roleURI="http://www.bicycletherapeutics.com/role/DisclosureShareBasedCompensationDetails" id="DisclosureShareBasedCompensationDetails">
        <link:definition>99940801 - Disclosure - Share-based compensation (Details)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType roleURI="http://www.bicycletherapeutics.com/role/DisclosureShareBasedCompensationShareBasedCompensationExpenseDetails" id="DisclosureShareBasedCompensationShareBasedCompensationExpenseDetails">
        <link:definition>99940802 - Disclosure - Share-based compensation - Share based compensation expense (Details)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType roleURI="http://www.bicycletherapeutics.com/role/DisclosureShareBasedCompensationShareOptionsDetails" id="DisclosureShareBasedCompensationShareOptionsDetails">
        <link:definition>99940803 - Disclosure - Share-based compensation - Share options (Details)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType roleURI="http://www.bicycletherapeutics.com/role/DisclosureShareBasedCompensationAssumptionsUsedInBlackScholesOptionPricingModelToDetermineFairValueOfShareOptionsDetails" id="DisclosureShareBasedCompensationAssumptionsUsedInBlackScholesOptionPricingModelToDetermineFairValueOfShareOptionsDetails">
        <link:definition>99940804 - Disclosure - Share-based compensation - Assumptions used in the Black Scholes option pricing model to determine the fair value of share options (Details)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType roleURI="http://www.bicycletherapeutics.com/role/DisclosureShareBasedCompensationRestrictedShareUnitsDetails" id="DisclosureShareBasedCompensationRestrictedShareUnitsDetails">
        <link:definition>99940805 - Disclosure - Share-based compensation - Restricted share units (Details)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType roleURI="http://www.bicycletherapeutics.com/role/DisclosureSignificantAgreementsCollaborationRevenuesDetails" id="DisclosureSignificantAgreementsCollaborationRevenuesDetails">
        <link:definition>99940901 - Disclosure - Significant agreements - Collaboration revenues (Details)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType roleURI="http://www.bicycletherapeutics.com/role/DisclosureSignificantAgreementsBayerCollaborationAgreementDetails" id="DisclosureSignificantAgreementsBayerCollaborationAgreementDetails">
        <link:definition>99940902 - Disclosure - Significant agreements - Bayer Collaboration Agreement (Details)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType roleURI="http://www.bicycletherapeutics.com/role/DisclosureSignificantAgreementsBayerCollaborationAgreementAccountingAnalysisDetails" id="DisclosureSignificantAgreementsBayerCollaborationAgreementAccountingAnalysisDetails">
        <link:definition>99940903 - Disclosure - Significant agreements - Bayer Collaboration Agreement - Accounting Analysis (Details)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType roleURI="http://www.bicycletherapeutics.com/role/DisclosureSignificantAgreementsNovartisCollaborationAgreementDetails" id="DisclosureSignificantAgreementsNovartisCollaborationAgreementDetails">
        <link:definition>99940904 - Disclosure - Significant agreements - Novartis Collaboration Agreement (Details)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType roleURI="http://www.bicycletherapeutics.com/role/DisclosureSignificantAgreementsIonisEvaluationAndOptionAgreementDetails" id="DisclosureSignificantAgreementsIonisEvaluationAndOptionAgreementDetails">
        <link:definition>99940906 - Disclosure - Significant agreements - Ionis Evaluation and Option Agreement (Details)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType roleURI="http://www.bicycletherapeutics.com/role/DisclosureSignificantAgreementsIonisCollaborationAgreementDetails" id="DisclosureSignificantAgreementsIonisCollaborationAgreementDetails">
        <link:definition>99940907 - Disclosure - Significant agreements - Ionis Collaboration Agreement (Details)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType roleURI="http://www.bicycletherapeutics.com/role/DisclosureSignificantAgreementsIonisSharePurchaseAgreementDetails" id="DisclosureSignificantAgreementsIonisSharePurchaseAgreementDetails">
        <link:definition>99940908 - Disclosure - Significant agreements - Ionis Share Purchase Agreement (Details)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType roleURI="http://www.bicycletherapeutics.com/role/DisclosureSignificantAgreementsIonisAccountingAnalysisDetails" id="DisclosureSignificantAgreementsIonisAccountingAnalysisDetails">
        <link:definition>99940909 - Disclosure - Significant agreements - Ionis Accounting Analysis (Details)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType roleURI="http://www.bicycletherapeutics.com/role/DisclosureSignificantAgreementsGenentechCollaborationAgreementDetails" id="DisclosureSignificantAgreementsGenentechCollaborationAgreementDetails">
        <link:definition>99940910 - Disclosure - Significant agreements - Genentech Collaboration Agreement (Details)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType roleURI="http://www.bicycletherapeutics.com/role/DisclosureSignificantAgreementsSummaryOfContractAssetsAndLiabilitiesDetails" id="DisclosureSignificantAgreementsSummaryOfContractAssetsAndLiabilitiesDetails">
        <link:definition>99940911 - Disclosure - Significant agreements - Summary of Contract Assets and Liabilities (Details)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType roleURI="http://www.bicycletherapeutics.com/role/DisclosureSignificantAgreementsCancerResearchUkDetails" id="DisclosureSignificantAgreementsCancerResearchUkDetails">
        <link:definition>99940913 - Disclosure - Significant agreements - Cancer Research UK (Details)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType roleURI="http://www.bicycletherapeutics.com/role/DisclosureIncomeTaxesDetails" id="DisclosureIncomeTaxesDetails">
        <link:definition>99941006 - Disclosure - Income taxes (Details)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType roleURI="http://www.bicycletherapeutics.com/role/DisclosureCommitmentsAndContingenciesOperatingLeasesAndFinanceLeasesDetails" id="DisclosureCommitmentsAndContingenciesOperatingLeasesAndFinanceLeasesDetails">
        <link:definition>99941101 - Disclosure - Commitments and contingencies - Operating Leases and Finance Leases (Details)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType roleURI="http://www.bicycletherapeutics.com/role/DisclosureNetLossPerShareSecuritiesExcludedFromDilutedPerShareCalculationDetails" id="DisclosureNetLossPerShareSecuritiesExcludedFromDilutedPerShareCalculationDetails">
        <link:definition>99941202 - Disclosure - Net loss per share - Securities excluded from the diluted per share calculation (Details)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType roleURI="http://www.bicycletherapeutics.com/role/DisclosureBenefitPlansDetails" id="DisclosureBenefitPlansDetails">
        <link:definition>99941301 - Disclosure - Benefit plans (Details)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType roleURI="http://www.bicycletherapeutics.com/role/DisclosureRelatedPartyTransactionsDetails" id="DisclosureRelatedPartyTransactionsDetails">
        <link:definition>99941401 - Disclosure - Related party transactions (Details)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType roleURI="http://www.bicycletherapeutics.com/role/DisclosureSegmentsAndGeographicInformationDetails" id="DisclosureSegmentsAndGeographicInformationDetails">
        <link:definition>99941501 - Disclosure - Segments and geographic information (Details)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType roleURI="http://www.bicycletherapeutics.com/role/DisclosureSubsequentEventsDetails" id="DisclosureSubsequentEventsDetails">
        <link:definition>99941601 - Disclosure - Subsequent events (Details)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType roleURI="http://www.bicycletherapeutics.com/role/StatementConsolidatedStatementsOfShareholdersEquityParenthetical" id="StatementConsolidatedStatementsOfShareholdersEquityParenthetical">
        <link:definition>995200305 - Statement - Consolidated Statements of Shareholders' Equity (Parenthetical)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType roleURI="http://www.bicycletherapeutics.com/role/DisclosureNatureOfBusinessAndBasisOfPresentation" id="DisclosureNatureOfBusinessAndBasisOfPresentation">
        <link:definition>995210101 - Disclosure - Nature of the business and basis of presentation</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType roleURI="http://www.bicycletherapeutics.com/role/DisclosureSummaryOfSignificantAccountingPolicies" id="DisclosureSummaryOfSignificantAccountingPolicies">
        <link:definition>995210201 - Disclosure - Summary of significant accounting policies</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType roleURI="http://www.bicycletherapeutics.com/role/DisclosureFairValueOfFinancialAssetsAndLiabilities" id="DisclosureFairValueOfFinancialAssetsAndLiabilities">
        <link:definition>995210301 - Disclosure - Fair value of financial assets and liabilities</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType roleURI="http://www.bicycletherapeutics.com/role/DisclosurePropertyAndEquipmentNet" id="DisclosurePropertyAndEquipmentNet">
        <link:definition>995210401 - Disclosure - Property and equipment, net</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType roleURI="http://www.bicycletherapeutics.com/role/DisclosureAccruedExpensesAndOtherCurrentLiabilities" id="DisclosureAccruedExpensesAndOtherCurrentLiabilities">
        <link:definition>995210501 - Disclosure - Accrued expenses and other current liabilities</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType roleURI="http://www.bicycletherapeutics.com/role/DisclosureDebt" id="DisclosureDebt">
        <link:definition>995210601 - Disclosure - Debt</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType roleURI="http://www.bicycletherapeutics.com/role/DisclosureOrdinaryShares" id="DisclosureOrdinaryShares">
        <link:definition>995210701 - Disclosure - Ordinary shares</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType roleURI="http://www.bicycletherapeutics.com/role/DisclosureShareBasedCompensation" id="DisclosureShareBasedCompensation">
        <link:definition>995210801 - Disclosure - Share-based compensation</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType roleURI="http://www.bicycletherapeutics.com/role/DisclosureSignificantAgreements" id="DisclosureSignificantAgreements">
        <link:definition>995210901 - Disclosure - Significant agreements</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType roleURI="http://www.bicycletherapeutics.com/role/DisclosureIncomeTaxes" id="DisclosureIncomeTaxes">
        <link:definition>995211001 - Disclosure - Income taxes</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType roleURI="http://www.bicycletherapeutics.com/role/DisclosureCommitmentsAndContingencies" id="DisclosureCommitmentsAndContingencies">
        <link:definition>995211101 - Disclosure - Commitments and contingencies</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType roleURI="http://www.bicycletherapeutics.com/role/DisclosureNetLossPerShare" id="DisclosureNetLossPerShare">
        <link:definition>995211201 - Disclosure - Net loss per share</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType roleURI="http://www.bicycletherapeutics.com/role/DisclosureBenefitPlans" id="DisclosureBenefitPlans">
        <link:definition>995211301 - Disclosure - Benefit plans</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType roleURI="http://www.bicycletherapeutics.com/role/DisclosureRelatedPartyTransactions" id="DisclosureRelatedPartyTransactions">
        <link:definition>995211401 - Disclosure - Related party transactions</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType roleURI="http://www.bicycletherapeutics.com/role/DisclosureSegmentsAndGeographicInformation" id="DisclosureSegmentsAndGeographicInformation">
        <link:definition>995211501 - Disclosure - Segments and geographic information</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType roleURI="http://www.bicycletherapeutics.com/role/DisclosureSubsequentEvents" id="DisclosureSubsequentEvents">
        <link:definition>995211601 - Disclosure - Subsequent events</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType roleURI="http://www.bicycletherapeutics.com/role/DisclosureSummaryOfSignificantAccountingPoliciesPolicies" id="DisclosureSummaryOfSignificantAccountingPoliciesPolicies">
        <link:definition>99920202 - Disclosure - Summary of significant accounting policies (Policies)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType roleURI="http://www.bicycletherapeutics.com/role/DisclosureSummaryOfSignificantAccountingPoliciesTables" id="DisclosureSummaryOfSignificantAccountingPoliciesTables">
        <link:definition>99930203 - Disclosure - Summary of significant accounting policies (Tables)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType roleURI="http://www.bicycletherapeutics.com/role/DisclosurePropertyAndEquipmentNetTables" id="DisclosurePropertyAndEquipmentNetTables">
        <link:definition>99930403 - Disclosure - Property and equipment, net (Tables)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType roleURI="http://www.bicycletherapeutics.com/role/DisclosureAccruedExpensesAndOtherCurrentLiabilitiesTables" id="DisclosureAccruedExpensesAndOtherCurrentLiabilitiesTables">
        <link:definition>99930503 - Disclosure - Accrued expenses and other current liabilities (Tables)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType roleURI="http://www.bicycletherapeutics.com/role/DisclosureIncomeTaxesTables" id="DisclosureIncomeTaxesTables">
        <link:definition>99931003 - Disclosure - Income taxes (Tables)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType roleURI="http://www.bicycletherapeutics.com/role/DisclosureCommitmentsAndContingenciesTables" id="DisclosureCommitmentsAndContingenciesTables">
        <link:definition>99931103 - Disclosure - Commitments and contingencies (Tables)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType roleURI="http://www.bicycletherapeutics.com/role/DisclosureNetLossPerShareTables" id="DisclosureNetLossPerShareTables">
        <link:definition>99931203 - Disclosure - Net loss per share (Tables)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType roleURI="http://www.bicycletherapeutics.com/role/DisclosureSegmentsAndGeographicInformationTables" id="DisclosureSegmentsAndGeographicInformationTables">
        <link:definition>99931503 - Disclosure - Segments and geographic information (Tables)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType roleURI="http://www.bicycletherapeutics.com/role/DisclosureSummaryOfSignificantAccountingPoliciesForeignCurrencyAndCurrencyTranslationDetails" id="DisclosureSummaryOfSignificantAccountingPoliciesForeignCurrencyAndCurrencyTranslationDetails">
        <link:definition>99940201 - Disclosure - Summary of significant accounting policies - Foreign currency and currency translation (Details)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType roleURI="http://www.bicycletherapeutics.com/role/DisclosureSummaryOfSignificantAccountingPoliciesConcentrationsOfCreditRiskAndOfSignificantSuppliersDetails" id="DisclosureSummaryOfSignificantAccountingPoliciesConcentrationsOfCreditRiskAndOfSignificantSuppliersDetails">
        <link:definition>99940202 - Disclosure - Summary of significant accounting policies - Concentrations of credit risk and of significant suppliers (Details)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType roleURI="http://www.bicycletherapeutics.com/role/DisclosureSummaryOfSignificantAccountingPoliciesCashAndCashEquivalentsDetails" id="DisclosureSummaryOfSignificantAccountingPoliciesCashAndCashEquivalentsDetails">
        <link:definition>99940203 - Disclosure - Summary of significant accounting policies - Cash and cash equivalents (Details)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType roleURI="http://www.bicycletherapeutics.com/role/DisclosureSummaryOfSignificantAccountingPoliciesShareBasedCompensationDetails" id="DisclosureSummaryOfSignificantAccountingPoliciesShareBasedCompensationDetails">
        <link:definition>99940206 - Disclosure - Summary of significant accounting policies - Share based compensation (Details)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType roleURI="http://www.bicycletherapeutics.com/role/DisclosureNetLossPerShareBasicAndDilutedNetLossPerShareDetails" id="DisclosureNetLossPerShareBasicAndDilutedNetLossPerShareDetails">
        <link:definition>99941201 - Disclosure - Net loss per share - Basic and diluted net loss per share (Details)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:linkbaseRef xlink:type="simple" xlink:href="bcyc-20251231_pre.xml" xlink:role="http://www.xbrl.org/2003/role/presentationLinkbaseRef" xlink:arcrole="http://www.w3.org/1999/xlink/properties/linkbase" />
      <link:linkbaseRef xlink:type="simple" xlink:href="bcyc-20251231_def.xml" xlink:role="http://www.xbrl.org/2003/role/definitionLinkbaseRef" xlink:arcrole="http://www.w3.org/1999/xlink/properties/linkbase" />
      <link:linkbaseRef xlink:type="simple" xlink:href="bcyc-20251231_lab.xml" xlink:role="http://www.xbrl.org/2003/role/labelLinkbaseRef" xlink:arcrole="http://www.w3.org/1999/xlink/properties/linkbase" />
      <link:linkbaseRef xlink:type="simple" xlink:href="bcyc-20251231_cal.xml" xlink:role="http://www.xbrl.org/2003/role/calculationLinkbaseRef" xlink:arcrole="http://www.w3.org/1999/xlink/properties/linkbase" xlink:title="Calculation Links, all" />
    </xsd:appinfo>
  </xsd:annotation>
  <xsd:import namespace="https://xbrl.org/2023/calculation-1.1" schemaLocation="https://www.xbrl.org/2023/calculation-1.1.xsd" />
  <xsd:import namespace="http://xbrl.sec.gov/ecd/2025" schemaLocation="https://xbrl.sec.gov/ecd/2025/ecd-2025.xsd" />
  <xsd:import namespace="http://xbrl.sec.gov/dei/2025" schemaLocation="https://xbrl.sec.gov/dei/2025/dei-2025.xsd" />
  <xsd:import namespace="http://www.xbrl.org/dtr/type/2024-01-31" schemaLocation="https://www.xbrl.org/dtr/type/2024-01-31/types.xsd" />
  <xsd:import namespace="http://www.xbrl.org/2009/role/negated" schemaLocation="http://www.xbrl.org/lrr/role/negated-2009-12-16.xsd" />
  <xsd:import namespace="http://www.xbrl.org/2003/instance" schemaLocation="http://www.xbrl.org/2003/xbrl-instance-2003-12-31.xsd" />
  <xsd:import namespace="http://xbrl.org/2005/xbrldt" schemaLocation="http://www.xbrl.org/2005/xbrldt-2005.xsd" />
  <xsd:import namespace="http://fasb.org/us-roles/2025" schemaLocation="https://xbrl.fasb.org/us-gaap/2025/elts/us-roles-2025.xsd" />
  <import namespace="http://fasb.org/us-gaap/2025" schemaLocation="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd" xmlns="http://www.w3.org/2001/XMLSchema" />
  <import namespace="http://fasb.org/srt/2025" schemaLocation="https://xbrl.fasb.org/srt/2025/elts/srt-2025.xsd" xmlns="http://www.w3.org/2001/XMLSchema" />
  <import namespace="http://xbrl.sec.gov/country/2025" schemaLocation="https://xbrl.sec.gov/country/2025/country-2025.xsd" xmlns="http://www.w3.org/2001/XMLSchema" />
  <xsd:import namespace="http://xbrl.sec.gov/ecd-sub/2025" schemaLocation="https://xbrl.sec.gov/ecd/2025/ecd-sub-2025.xsd" />
  <xsd:import namespace="http://xbrl.sec.gov/cyd/2025" schemaLocation="https://xbrl.sec.gov/cyd/2025/cyd-2025.xsd" />
  <xsd:import namespace="http://xbrl.sec.gov/cyd-af-sub/2025" schemaLocation="https://xbrl.sec.gov/cyd/2025/cyd-af-sub-2025.xsd" />
  <element id="bcyc_ResearchAndDevelopmentIncentivesReceivableCurrent" name="ResearchAndDevelopmentIncentivesReceivableCurrent" nillable="true" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="instant" xbrli:balance="debit" xmlns="http://www.w3.org/2001/XMLSchema" />
  <element id="bcyc_IncreaseDecreaseInResearchAndDevelopmentIncentivesReceivable" name="IncreaseDecreaseInResearchAndDevelopmentIncentivesReceivable" nillable="true" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" xbrli:balance="credit" xmlns="http://www.w3.org/2001/XMLSchema" />
  <element id="bcyc_IncreaseDecreaseInOperatingLeaseRightOfUseAssets" name="IncreaseDecreaseInOperatingLeaseRightOfUseAssets" nillable="true" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" xbrli:balance="credit" xmlns="http://www.w3.org/2001/XMLSchema" />
  <element id="bcyc_AccruedLiabilitiesAndOtherCurrentLiabilitiesAbstract" name="AccruedLiabilitiesAndOtherCurrentLiabilitiesAbstract" nillable="true" type="xbrli:stringItemType" substitutionGroup="xbrli:item" abstract="true" xbrli:periodType="duration" xmlns="http://www.w3.org/2001/XMLSchema" />
  <element id="bcyc_AccruedLiabilitiesAndOtherLiabilitiesDisclosureCurrentTextBlock" name="AccruedLiabilitiesAndOtherLiabilitiesDisclosureCurrentTextBlock" nillable="true" type="dtr-types:textBlockItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" xmlns="http://www.w3.org/2001/XMLSchema" />
  <element id="bcyc_AccruedLiabilitiesAndOtherCurrentLiabilitiesTableTextBlock" name="AccruedLiabilitiesAndOtherCurrentLiabilitiesTableTextBlock" nillable="true" type="dtr-types:textBlockItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" xmlns="http://www.w3.org/2001/XMLSchema" />
  <element id="bcyc_AccruedExternalResearchAndDevelopmentExpenses" name="AccruedExternalResearchAndDevelopmentExpenses" nillable="true" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="instant" xbrli:balance="credit" xmlns="http://www.w3.org/2001/XMLSchema" />
  <element id="bcyc_RevenuePerformanceObligationAllocationOfTransactionPriceTableTextBlock" name="RevenuePerformanceObligationAllocationOfTransactionPriceTableTextBlock" nillable="true" type="dtr-types:textBlockItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" xmlns="http://www.w3.org/2001/XMLSchema" />
  <element id="bcyc_RevenueChangeInContractWithCustomerAssetAndLiabilityTableTextBlock" name="RevenueChangeInContractWithCustomerAssetAndLiabilityTableTextBlock" nillable="true" type="dtr-types:textBlockItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" xmlns="http://www.w3.org/2001/XMLSchema" />
  <element id="bcyc_AstrazenecaCollaborationAgreementMember" name="AstrazenecaCollaborationAgreementMember" nillable="true" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" abstract="true" xbrli:periodType="duration" xmlns="http://www.w3.org/2001/XMLSchema" />
  <element id="bcyc_AchievementOfMilestoneAxis" name="AchievementOfMilestoneAxis" nillable="true" type="xbrli:stringItemType" substitutionGroup="xbrldt:dimensionItem" abstract="true" xbrli:periodType="duration" xmlns="http://www.w3.org/2001/XMLSchema" />
  <element id="bcyc_AchievementOfMilestoneDomain" name="AchievementOfMilestoneDomain" nillable="true" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" abstract="true" xbrli:periodType="duration" xmlns="http://www.w3.org/2001/XMLSchema" />
  <element id="bcyc_PerformanceObligationAxis" name="PerformanceObligationAxis" nillable="true" type="xbrli:stringItemType" substitutionGroup="xbrldt:dimensionItem" abstract="true" xbrli:periodType="duration" xmlns="http://www.w3.org/2001/XMLSchema" />
  <element id="bcyc_PerformanceObligationDomain" name="PerformanceObligationDomain" nillable="true" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" abstract="true" xbrli:periodType="duration" xmlns="http://www.w3.org/2001/XMLSchema" />
  <element id="bcyc_CollaborativeArrangementUpfrontCashPaymentReceived" name="CollaborativeArrangementUpfrontCashPaymentReceived" nillable="true" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" xbrli:balance="credit" xmlns="http://www.w3.org/2001/XMLSchema" abstract="false" />
  <element id="bcyc_ContractWithCustomerLiabilityAdditions" name="ContractWithCustomerLiabilityAdditions" nillable="true" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" xbrli:balance="credit" xmlns="http://www.w3.org/2001/XMLSchema" />
  <element id="bcyc_ContractWithCustomerLiabilityDeductions" name="ContractWithCustomerLiabilityDeductions" nillable="true" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" xbrli:balance="debit" xmlns="http://www.w3.org/2001/XMLSchema" />
  <element id="bcyc_ContractWithCustomerLiabilityRevenueRecognizedProportionalPerformanceObligation" name="ContractWithCustomerLiabilityRevenueRecognizedProportionalPerformanceObligation" nillable="true" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" xbrli:balance="credit" xmlns="http://www.w3.org/2001/XMLSchema" />
  <element id="bcyc_EffectiveIncomeTaxRateReconciliationNetLossesSurrenderedForResearchCredit" name="EffectiveIncomeTaxRateReconciliationNetLossesSurrenderedForResearchCredit" nillable="true" type="dtr-types:percentItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" xmlns="http://www.w3.org/2001/XMLSchema" />
  <element id="bcyc_OfficeAndLaboratorySpaceInBuilding900BabrahamResearchCampusCambridgeMember" name="OfficeAndLaboratorySpaceInBuilding900BabrahamResearchCampusCambridgeMember" nillable="true" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" abstract="true" xbrli:periodType="duration" xmlns="http://www.w3.org/2001/XMLSchema" />
  <element id="bcyc_MaximumDaysAllowedForCancellationOfContractsPriorWrittenNotice" name="MaximumDaysAllowedForCancellationOfContractsPriorWrittenNotice" nillable="true" type="xbrli:durationItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" xmlns="http://www.w3.org/2001/XMLSchema" />
  <element id="bcyc_ShareOptionPlan2019Member" name="ShareOptionPlan2019Member" nillable="true" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" abstract="true" xbrli:periodType="duration" xmlns="http://www.w3.org/2001/XMLSchema" />
  <element id="bcyc_PreIpoShareOptionsAndRestrictedSharesMember" name="PreIpoShareOptionsAndRestrictedSharesMember" nillable="true" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" abstract="true" xbrli:periodType="duration" xmlns="http://www.w3.org/2001/XMLSchema" />
  <element id="bcyc_ShareBasedCompensationArrangementByShareBasedPaymentAwardAnnualIncreasePercentage" name="ShareBasedCompensationArrangementByShareBasedPaymentAwardAnnualIncreasePercentage" nillable="true" type="dtr-types:percentItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" xmlns="http://www.w3.org/2001/XMLSchema" />
  <element id="bcyc_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingWeightedAverageContractualTermAbstract" name="ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingWeightedAverageContractualTermAbstract" nillable="true" type="xbrli:stringItemType" substitutionGroup="xbrli:item" abstract="true" xbrli:periodType="duration" xmlns="http://www.w3.org/2001/XMLSchema" />
  <element id="bcyc_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingAggregateIntrinsicValueAbstract" name="ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingAggregateIntrinsicValueAbstract" nillable="true" type="xbrli:stringItemType" substitutionGroup="xbrli:item" abstract="true" xbrli:periodType="duration" xmlns="http://www.w3.org/2001/XMLSchema" />
  <element id="bcyc_EmployeeAndDirectorMember" name="EmployeeAndDirectorMember" nillable="true" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" abstract="true" xbrli:periodType="duration" xmlns="http://www.w3.org/2001/XMLSchema" />
  <element id="bcyc_Plan401KMember" name="Plan401KMember" nillable="true" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" abstract="true" xbrli:periodType="duration" xmlns="http://www.w3.org/2001/XMLSchema" />
  <element id="bcyc_UKPlanMember" name="UKPlanMember" nillable="true" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" abstract="true" xbrli:periodType="duration" xmlns="http://www.w3.org/2001/XMLSchema" />
  <element id="bcyc_RevenueRecognitionAllocatedDeterminedTransactionPrice" name="RevenueRecognitionAllocatedDeterminedTransactionPrice" nillable="true" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="instant" xbrli:balance="credit" xmlns="http://www.w3.org/2001/XMLSchema" />
  <element id="bcyc_ResearchAndDevelopmentArrangementObligationToRepayOtherPartiesAbstract" name="ResearchAndDevelopmentArrangementObligationToRepayOtherPartiesAbstract" nillable="true" type="xbrli:stringItemType" substitutionGroup="xbrli:item" abstract="true" xbrli:periodType="duration" xmlns="http://www.w3.org/2001/XMLSchema" />
  <element id="bcyc_ScheduleOfComponentsOfNetIncomeLossBeforeIncomeTaxProvisionTableTextBlock" name="ScheduleOfComponentsOfNetIncomeLossBeforeIncomeTaxProvisionTableTextBlock" nillable="true" type="dtr-types:textBlockItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" xmlns="http://www.w3.org/2001/XMLSchema" />
  <element id="bcyc_ResearchAndManufacturingContractCostsAndAccrualsPolicyTextBlock" name="ResearchAndManufacturingContractCostsAndAccrualsPolicyTextBlock" nillable="true" type="dtr-types:textBlockItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" xmlns="http://www.w3.org/2001/XMLSchema" abstract="false" />
  <element id="bcyc_ResearchAndDevelopmentIncentivesAndReceivablePolicyTextBlock" name="ResearchAndDevelopmentIncentivesAndReceivablePolicyTextBlock" nillable="true" type="dtr-types:textBlockItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" xmlns="http://www.w3.org/2001/XMLSchema" />
  <element id="bcyc_ScheduleOfPropertyPlantAndEquipmentUsefulLifeTableTextBlock" name="ScheduleOfPropertyPlantAndEquipmentUsefulLifeTableTextBlock" nillable="true" type="dtr-types:textBlockItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" xmlns="http://www.w3.org/2001/XMLSchema" />
  <element id="bcyc_ConsultancyServicesWithStoneSunnyIslesInc.Member" name="ConsultancyServicesWithStoneSunnyIslesInc.Member" nillable="true" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" abstract="true" xbrli:periodType="duration" xmlns="http://www.w3.org/2001/XMLSchema" />
  <element id="bcyc_DeferredTaxAssetsOperatingLeaseLiability" name="DeferredTaxAssetsOperatingLeaseLiability" nillable="true" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="instant" xbrli:balance="debit" xmlns="http://www.w3.org/2001/XMLSchema" />
  <element id="bcyc_ReductionOfResearchAndDevelopmentExpense" name="ReductionOfResearchAndDevelopmentExpense" nillable="true" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" xbrli:balance="credit" xmlns="http://www.w3.org/2001/XMLSchema" />
  <element id="bcyc_NumberOfPotentialDevelopmentCandidates" name="NumberOfPotentialDevelopmentCandidates" nillable="true" type="xbrli:integerItemType" substitutionGroup="xbrli:item" xbrli:periodType="instant" xmlns="http://www.w3.org/2001/XMLSchema" />
  <element id="bcyc_NumberOfImmunoOncologyTargets" name="NumberOfImmunoOncologyTargets" nillable="true" type="xbrli:integerItemType" substitutionGroup="xbrli:item" xbrli:periodType="instant" xmlns="http://www.w3.org/2001/XMLSchema" />
  <element id="bcyc_AdditionalNumberOfImmunoOncologyTargets" name="AdditionalNumberOfImmunoOncologyTargets" nillable="true" type="xbrli:integerItemType" substitutionGroup="xbrli:item" xbrli:periodType="instant" xmlns="http://www.w3.org/2001/XMLSchema" />
  <element id="bcyc_ExpansionFeePerAdditionalCollaborationProgram" name="ExpansionFeePerAdditionalCollaborationProgram" nillable="true" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" xbrli:balance="debit" xmlns="http://www.w3.org/2001/XMLSchema" />
  <element id="bcyc_CollaborationAgreementSalesMilestonePaymentsReceivable" name="CollaborationAgreementSalesMilestonePaymentsReceivable" nillable="true" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="instant" xbrli:balance="debit" xmlns="http://www.w3.org/2001/XMLSchema" abstract="false" />
  <element id="bcyc_CancerResearchUkBtOneSevenOneEightMember" name="CancerResearchUkBtOneSevenOneEightMember" nillable="true" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" abstract="true" xbrli:periodType="duration" xmlns="http://www.w3.org/2001/XMLSchema" />
  <element id="bcyc_SpecifiedTargetingArmMaterialRightArmProgramOneMember" name="SpecifiedTargetingArmMaterialRightArmProgramOneMember" nillable="true" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" abstract="true" xbrli:periodType="duration" xmlns="http://www.w3.org/2001/XMLSchema" />
  <element id="bcyc_TwoMaterialRightsAssociatedWithLsrGoOptionForCollaborationProgramsOneAndTwoMember" name="TwoMaterialRightsAssociatedWithLsrGoOptionForCollaborationProgramsOneAndTwoMember" nillable="true" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" abstract="true" xbrli:periodType="duration" xmlns="http://www.w3.org/2001/XMLSchema" />
  <element id="bcyc_NumberOfExpansionOptionCollaborationProgramsDevGo" name="NumberOfExpansionOptionCollaborationProgramsDevGo" nillable="true" type="xbrli:integerItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" xmlns="http://www.w3.org/2001/XMLSchema" />
  <element id="bcyc_NumberOfCollaborationPrograms" name="NumberOfCollaborationPrograms" nillable="true" type="xbrli:integerItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" xmlns="http://www.w3.org/2001/XMLSchema" />
  <element id="bcyc_MaterialRightsMember" name="MaterialRightsMember" nillable="true" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" abstract="true" xbrli:periodType="duration" xmlns="http://www.w3.org/2001/XMLSchema" />
  <element id="bcyc_SignificantRisksAndUncertaintiesPolicyTextBlock" name="SignificantRisksAndUncertaintiesPolicyTextBlock" nillable="true" type="dtr-types:textBlockItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" xmlns="http://www.w3.org/2001/XMLSchema" />
  <element id="bcyc_NumberOfYearsOverWhichRoyaltyIsPayable" name="NumberOfYearsOverWhichRoyaltyIsPayable" nillable="true" type="xbrli:durationItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" xmlns="http://www.w3.org/2001/XMLSchema" />
  <element id="bcyc_MaterialRightsExerciseOrExpiryTerm" name="MaterialRightsExerciseOrExpiryTerm" nillable="true" type="xbrli:durationItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" xmlns="http://www.w3.org/2001/XMLSchema" />
  <element id="bcyc_PeriodOverWhichPerformanceObligationsWillBePerformed" name="PeriodOverWhichPerformanceObligationsWillBePerformed" nillable="true" type="xbrli:durationItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" xmlns="http://www.w3.org/2001/XMLSchema" />
  <element id="bcyc_AtMarketOfferingMember" name="AtMarketOfferingMember" nillable="true" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" abstract="true" xbrli:periodType="duration" xmlns="http://www.w3.org/2001/XMLSchema" />
  <element id="bcyc_ShareOptionPlan2020Member" name="ShareOptionPlan2020Member" nillable="true" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" abstract="true" xbrli:periodType="duration" xmlns="http://www.w3.org/2001/XMLSchema" />
  <element id="bcyc_LoanAndSecurityAgreementMember" name="LoanAndSecurityAgreementMember" nillable="true" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" abstract="true" xbrli:periodType="duration" xmlns="http://www.w3.org/2001/XMLSchema" />
  <element id="bcyc_TermLoanMember" name="TermLoanMember" nillable="true" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" abstract="true" xbrli:periodType="duration" xmlns="http://www.w3.org/2001/XMLSchema" />
  <element id="bcyc_InitialTermLoanMember" name="InitialTermLoanMember" nillable="true" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" abstract="true" xbrli:periodType="duration" xmlns="http://www.w3.org/2001/XMLSchema" />
  <element id="bcyc_DebtInstrumentEndOfTermChargeRate" name="DebtInstrumentEndOfTermChargeRate" nillable="true" type="dtr-types:percentItemType" substitutionGroup="xbrli:item" xbrli:periodType="instant" xmlns="http://www.w3.org/2001/XMLSchema" />
  <element id="bcyc_DebtEndOfTermCharge" name="DebtEndOfTermCharge" nillable="true" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="instant" xbrli:balance="credit" xmlns="http://www.w3.org/2001/XMLSchema" />
  <element id="bcyc_TotalRevenueRecognizedFromBothBeginningBalanceAndCurrentPeriodIncreaseInContractLiability" name="TotalRevenueRecognizedFromBothBeginningBalanceAndCurrentPeriodIncreaseInContractLiability" nillable="true" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" xbrli:balance="credit" xmlns="http://www.w3.org/2001/XMLSchema" />
  <element id="bcyc_NonCashInterestExpense" name="NonCashInterestExpense" nillable="true" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" xbrli:balance="debit" xmlns="http://www.w3.org/2001/XMLSchema" />
  <element id="bcyc_GenentechMember" name="GenentechMember" nillable="true" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" abstract="true" xbrli:periodType="duration" xmlns="http://www.w3.org/2001/XMLSchema" />
  <element id="bcyc_DeferredRevenueMaterialRightsOptionMember" name="DeferredRevenueMaterialRightsOptionMember" nillable="true" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" abstract="true" xbrli:periodType="duration" xmlns="http://www.w3.org/2001/XMLSchema" />
  <xsd:element name="IonisCollaborationAgreementMember" id="bcyc_IonisCollaborationAgreementMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" nillable="true" xbrli:periodType="duration" abstract="true" />
  <xsd:element name="CollaborationAgreementNumberOfTargets" id="bcyc_CollaborationAgreementNumberOfTargets" type="xbrli:integerItemType" substitutionGroup="xbrli:item" nillable="true" xbrli:periodType="instant" abstract="false" />
  <xsd:element name="IonisEvaluationAndOptionAgreementMember" id="bcyc_IonisEvaluationAndOptionAgreementMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" nillable="true" xbrli:periodType="duration" abstract="true" />
  <xsd:element name="NumberOfPaymentsOfMidSingleDigitMillionDollarFailingToAchieveSpecifiedDevelopmentDiligenceMilestone" id="bcyc_NumberOfPaymentsOfMidSingleDigitMillionDollarFailingToAchieveSpecifiedDevelopmentDiligenceMilestone" type="xbrli:integerItemType" substitutionGroup="xbrli:item" nillable="true" xbrli:periodType="instant" abstract="false" />
  <xsd:element name="EstimatedAmountOfReimbursementPayableToContractResearchOrganizations" id="bcyc_EstimatedAmountOfReimbursementPayableToContractResearchOrganizations" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" nillable="true" xbrli:periodType="instant" abstract="false" xbrli:balance="credit" />
  <xsd:element name="UnderwrittenPublicOfferingMember" id="bcyc_UnderwrittenPublicOfferingMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" nillable="true" xbrli:periodType="duration" abstract="true" />
  <xsd:element name="FairValueOfSharesHeld" id="bcyc_FairValueOfSharesHeld" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" nillable="true" xbrli:periodType="instant" abstract="false" xbrli:balance="credit" />
  <xsd:element name="IonisSharePurchaseAgreementMember" id="bcyc_IonisSharePurchaseAgreementMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" nillable="true" xbrli:periodType="duration" abstract="true" />
  <xsd:element name="AmendedIonisCollaborationAgreementMember" id="bcyc_AmendedIonisCollaborationAgreementMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" nillable="true" xbrli:periodType="duration" abstract="true" />
  <xsd:element name="CollaborationProgramThreePerformanceObligationMember" id="bcyc_CollaborationProgramThreePerformanceObligationMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" nillable="true" xbrli:periodType="duration" abstract="true" />
  <xsd:element name="LesseeOperatingLeaseContractualTerm" id="bcyc_LesseeOperatingLeaseContractualTerm" type="xbrli:durationItemType" substitutionGroup="xbrli:item" nillable="true" xbrli:periodType="duration" abstract="false" />
  <xsd:element name="ShareBasedCompensationArrangementByShareBasedPaymentAwardsShareConversionRatio" id="bcyc_ShareBasedCompensationArrangementByShareBasedPaymentAwardsShareConversionRatio" type="xbrli:sharesItemType" substitutionGroup="xbrli:item" nillable="true" xbrli:periodType="duration" abstract="false" />
  <xsd:element name="ShareBasedCompensationArrangementsByShareBasedPaymentAwardVestingNumberOfEqualQuarterlyInstallments" id="bcyc_ShareBasedCompensationArrangementsByShareBasedPaymentAwardVestingNumberOfEqualQuarterlyInstallments" type="xbrli:integerItemType" substitutionGroup="xbrli:item" nillable="true" xbrli:periodType="duration" abstract="false" />
  <xsd:element name="ShareBasedCompensationArrangementsByShareBasedPaymentAwardVestingNumberOfEqualMonthlyInstallments" id="bcyc_ShareBasedCompensationArrangementsByShareBasedPaymentAwardVestingNumberOfEqualMonthlyInstallments" type="xbrli:integerItemType" substitutionGroup="xbrli:item" nillable="true" xbrli:periodType="duration" abstract="false" />
  <xsd:element name="NumberOfMaterialRightsAssociatedWithFuturePayments" id="bcyc_NumberOfMaterialRightsAssociatedWithFuturePayments" type="xbrli:integerItemType" substitutionGroup="xbrli:item" nillable="true" xbrli:periodType="duration" abstract="false" />
  <xsd:element name="ContractWithCustomerLiabilityForeignCurrencyAdjustment" id="bcyc_ContractWithCustomerLiabilityForeignCurrencyAdjustment" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" nillable="true" xbrli:periodType="duration" abstract="false" xbrli:balance="debit" />
  <xsd:element name="NewOfficeAndLaboratorySpaceInCambridgeUnitedKingdomMember" id="bcyc_NewOfficeAndLaboratorySpaceInCambridgeUnitedKingdomMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" nillable="true" xbrli:periodType="duration" abstract="true" />
  <xsd:element name="NumberOfJurisdictions" id="bcyc_NumberOfJurisdictions" type="xbrli:integerItemType" substitutionGroup="xbrli:item" nillable="true" xbrli:periodType="duration" abstract="false" />
  <xsd:element name="EstimatedVariableConsiderationNoLongerConstrained" id="bcyc_EstimatedVariableConsiderationNoLongerConstrained" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" nillable="true" xbrli:periodType="duration" abstract="false" xbrli:balance="credit" />
  <xsd:element name="OfficeAndLaboratorySpaceInCambridgeMassachusettsMember" id="bcyc_OfficeAndLaboratorySpaceInCambridgeMassachusettsMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" nillable="true" xbrli:periodType="duration" abstract="true" />
  <xsd:element name="NovartisCollaborationAgreementMember" id="bcyc_NovartisCollaborationAgreementMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" nillable="true" xbrli:periodType="duration" abstract="true" />
  <xsd:element name="CollaborationAgreementTieredSalesMilestonePaymentsReceivable" id="bcyc_CollaborationAgreementTieredSalesMilestonePaymentsReceivable" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" nillable="true" xbrli:periodType="instant" abstract="false" xbrli:balance="debit" />
  <xsd:element name="NumberOfCombinedPerformanceObligations" id="bcyc_NumberOfCombinedPerformanceObligations" type="xbrli:integerItemType" substitutionGroup="xbrli:item" nillable="true" xbrli:periodType="duration" abstract="false" />
  <xsd:element name="TwoMaterialRightsAssociatedWithLimitedSubstitutionRightsMember" id="bcyc_TwoMaterialRightsAssociatedWithLimitedSubstitutionRightsMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" nillable="true" xbrli:periodType="duration" abstract="true" />
  <xsd:element name="TwoMaterialRightsAssociatedWithOptionsToProgressDevelopmentCandidatesIncorporatingRadionuclidesMember" id="bcyc_TwoMaterialRightsAssociatedWithOptionsToProgressDevelopmentCandidatesIncorporatingRadionuclidesMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" nillable="true" xbrli:periodType="duration" abstract="true" />
  <xsd:element name="TwoMaterialRightsAssociatedWithOptionsToProgressDevelopmentCandidatesNotIncorporatingRadionuclidesMember" id="bcyc_TwoMaterialRightsAssociatedWithOptionsToProgressDevelopmentCandidatesNotIncorporatingRadionuclidesMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" nillable="true" xbrli:periodType="duration" abstract="true" />
  <xsd:element name="MaterialRightsAssociatedWithLsrGoOptionForCollaborationProgramsOneMember" id="bcyc_MaterialRightsAssociatedWithLsrGoOptionForCollaborationProgramsOneMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" nillable="true" xbrli:periodType="duration" abstract="true" />
  <xsd:element name="AgreementWithThirdPartyMember" id="bcyc_AgreementWithThirdPartyMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" nillable="true" xbrli:periodType="duration" abstract="true" />
  <xsd:element name="IncreaseDecreaseCapitalExpendituresIncurredButNotYetPaid" id="bcyc_IncreaseDecreaseCapitalExpendituresIncurredButNotYetPaid" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" nillable="true" xbrli:periodType="duration" abstract="false" xbrli:balance="credit" />
  <xsd:element name="CollaborationAndLicenseAgreementNumberOfCandidateCompoundsIntoFurtherDevelopment" id="bcyc_CollaborationAndLicenseAgreementNumberOfCandidateCompoundsIntoFurtherDevelopment" type="xbrli:integerItemType" substitutionGroup="xbrli:item" nillable="true" xbrli:periodType="instant" abstract="false" />
  <xsd:element name="BayerMember" id="bcyc_BayerMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" nillable="true" xbrli:periodType="duration" abstract="true" />
  <xsd:element name="DevelopmentAndRegulatoryMilestoneMember" id="bcyc_DevelopmentAndRegulatoryMilestoneMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" nillable="true" xbrli:periodType="duration" abstract="true" />
  <xsd:element name="CollaborationAgreementFutureMilestoneContingentPaymentsPayable" id="bcyc_CollaborationAgreementFutureMilestoneContingentPaymentsPayable" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" nillable="true" xbrli:periodType="instant" abstract="false" xbrli:balance="credit" />
  <xsd:element name="MilestoneAcrossAllPotentialTargetProgramsMember" id="bcyc_MilestoneAcrossAllPotentialTargetProgramsMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" nillable="true" xbrli:periodType="duration" abstract="true" />
  <xsd:element name="TwoCombinedPerformanceObligationsRelatedToLicensesAndResearchAndDevelopmentServicesAssociatedWithRadiopharmaceuticalCompoundsDirectedToFirstAndSecondTargetsMember" id="bcyc_TwoCombinedPerformanceObligationsRelatedToLicensesAndResearchAndDevelopmentServicesAssociatedWithRadiopharmaceuticalCompoundsDirectedToFirstAndSecondTargetsMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" nillable="true" xbrli:periodType="duration" abstract="true" />
  <xsd:element name="MaterialRightAssociatedWithLimitedSubstitutionRightsForEitherFirstOrSecondTargetMember" id="bcyc_MaterialRightAssociatedWithLimitedSubstitutionRightsForEitherFirstOrSecondTargetMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" nillable="true" xbrli:periodType="duration" abstract="true" />
  <xsd:element name="TwoMaterialRightsAssociatedWithOptionToProgressRadiopharmaceuticalCandidatesDirectedToFirstAndSecondTargetsIntoFurtherDevelopmentMember" id="bcyc_TwoMaterialRightsAssociatedWithOptionToProgressRadiopharmaceuticalCandidatesDirectedToFirstAndSecondTargetsIntoFurtherDevelopmentMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" nillable="true" xbrli:periodType="duration" abstract="true" />
  <xsd:element name="TwoMaterialRightsAssociatedWithOptionToProgressNonRadiopharmaceuticalCompoundDirectedToFirstAndSecondTargetsMember" id="bcyc_TwoMaterialRightsAssociatedWithOptionToProgressNonRadiopharmaceuticalCompoundDirectedToFirstAndSecondTargetsMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" nillable="true" xbrli:periodType="duration" abstract="true" />
  <xsd:element name="MaterialRightForOptionToExpandCollaborationToIncludeThirdTargetAndUnderlyingAdditionalOptionRightsMember" id="bcyc_MaterialRightForOptionToExpandCollaborationToIncludeThirdTargetAndUnderlyingAdditionalOptionRightsMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" nillable="true" xbrli:periodType="duration" abstract="true" />
  <xsd:element name="NonVotingOrdinarySharesMember" id="bcyc_NonVotingOrdinarySharesMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" nillable="true" xbrli:periodType="duration" abstract="true" />
  <xsd:element name="NumberOfMaterialRights" id="bcyc_NumberOfMaterialRights" type="xbrli:integerItemType" substitutionGroup="xbrli:item" nillable="true" xbrli:periodType="duration" abstract="false" />
  <xsd:element name="VotingOrdinarySharesMember" id="bcyc_VotingOrdinarySharesMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" nillable="true" xbrli:periodType="duration" abstract="true" />
  <xsd:element name="ContractWithCustomerLiabilityRevenueRecognizedChangesInTransactionPrice" id="bcyc_ContractWithCustomerLiabilityRevenueRecognizedChangesInTransactionPrice" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" nillable="true" xbrli:periodType="duration" abstract="false" xbrli:balance="credit" />
  <xsd:element name="NumberOfQuarterlyInstallments" id="bcyc_NumberOfQuarterlyInstallments" type="xbrli:integerItemType" substitutionGroup="xbrli:item" nillable="true" xbrli:periodType="duration" abstract="false" />
  <xsd:element name="CertainResearchAndDevelopmentExpendituresIncurredThereafterApril12023Member" id="bcyc_CertainResearchAndDevelopmentExpendituresIncurredThereafterApril12023Member" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" nillable="true" xbrli:periodType="duration" abstract="true" />
  <xsd:element name="ResearchAndDevelopmentTaxReliefsProgramPercentageOfTaxCreditOnSurrenderableLosses" id="bcyc_ResearchAndDevelopmentTaxReliefsProgramPercentageOfTaxCreditOnSurrenderableLosses" type="dtr-types:percentItemType" substitutionGroup="xbrli:item" nillable="true" xbrli:periodType="duration" abstract="false" />
  <xsd:element name="ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedAndSettledInPeriod" id="bcyc_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedAndSettledInPeriod" type="xbrli:sharesItemType" substitutionGroup="xbrli:item" nillable="true" xbrli:periodType="duration" abstract="false" />
  <xsd:element name="ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedAndDeferredInPeriod" id="bcyc_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedAndDeferredInPeriod" type="xbrli:sharesItemType" substitutionGroup="xbrli:item" nillable="true" xbrli:periodType="duration" abstract="false" />
  <xsd:element name="ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriodSubjectToDeferredSettlement" id="bcyc_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriodSubjectToDeferredSettlement" type="xbrli:sharesItemType" substitutionGroup="xbrli:item" nillable="true" xbrli:periodType="instant" abstract="false" />
  <xsd:element name="ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedAndSettledInPeriodWeightedAverageGrantDateFairValue" id="bcyc_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedAndSettledInPeriodWeightedAverageGrantDateFairValue" type="dtr-types:perShareItemType" substitutionGroup="xbrli:item" nillable="true" xbrli:periodType="duration" abstract="false" />
  <xsd:element name="ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedAndDeferredInPeriodWeightedAverageGrantDateFairValue" id="bcyc_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedAndDeferredInPeriodWeightedAverageGrantDateFairValue" type="dtr-types:perShareItemType" substitutionGroup="xbrli:item" nillable="true" xbrli:periodType="duration" abstract="false" />
  <xsd:element name="ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriodSubjectToDeferredSettlementWeightedAverageGrantDateFairValue" id="bcyc_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriodSubjectToDeferredSettlementWeightedAverageGrantDateFairValue" type="dtr-types:perShareItemType" substitutionGroup="xbrli:item" nillable="true" xbrli:periodType="instant" abstract="false" />
  <xsd:element name="CertainResearchAndDevelopmentExpendituresIncurredThereafterApril12024Member" id="bcyc_CertainResearchAndDevelopmentExpendituresIncurredThereafterApril12024Member" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" nillable="true" xbrli:periodType="duration" abstract="true" />
  <xsd:element name="ResearchAndDevelopmentPercentageOfTaxCreditOnTotalExpenditure" id="bcyc_ResearchAndDevelopmentPercentageOfTaxCreditOnTotalExpenditure" type="dtr-types:percentItemType" substitutionGroup="xbrli:item" nillable="true" xbrli:periodType="duration" abstract="false" />
  <xsd:element name="ShareBasedCompensationArrangementsByShareBasedPaymentAwardVestingNumberOfEqualAnnualInstallments" id="bcyc_ShareBasedCompensationArrangementsByShareBasedPaymentAwardVestingNumberOfEqualAnnualInstallments" type="xbrli:integerItemType" substitutionGroup="xbrli:item" nillable="true" xbrli:periodType="duration" abstract="false" />
  <xsd:element name="ShareBasedPaymentArrangementThreeYearVestMember" id="bcyc_ShareBasedPaymentArrangementThreeYearVestMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" nillable="true" xbrli:periodType="duration" abstract="true" />
  <xsd:element name="NumberOfVotePerShare" id="bcyc_NumberOfVotePerShare" type="xbrli:integerItemType" substitutionGroup="xbrli:item" nillable="true" xbrli:periodType="duration" abstract="false" />
  <xsd:element name="BakerBrothersAdvisorsLpMember" id="bcyc_BakerBrothersAdvisorsLpMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" nillable="true" xbrli:periodType="duration" abstract="true" />
  <xsd:element name="DebtInstrumentPrepaymentCharges" id="bcyc_DebtInstrumentPrepaymentCharges" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" nillable="true" xbrli:periodType="duration" abstract="false" xbrli:balance="debit" />
  <xsd:element name="InducementPlan2024Member" id="bcyc_InducementPlan2024Member" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" nillable="true" xbrli:periodType="duration" abstract="true" />
  <xsd:element name="ExpirationOfTwoMaterialRightsAssociateWithLimitedSubstitutionRightsMember" id="bcyc_ExpirationOfTwoMaterialRightsAssociateWithLimitedSubstitutionRightsMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" nillable="true" xbrli:periodType="duration" abstract="true" />
  <xsd:element name="IncrementalIncomeTaxBenefitOnCompletionOfResearchAndDevelopmentTaxCreditStudy" id="bcyc_IncrementalIncomeTaxBenefitOnCompletionOfResearchAndDevelopmentTaxCreditStudy" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" nillable="true" xbrli:periodType="duration" abstract="false" xbrli:balance="credit" />
  <xsd:element name="NumberOfGeographicRegionsInWhichOperating" id="bcyc_NumberOfGeographicRegionsInWhichOperating" type="xbrli:integerItemType" substitutionGroup="xbrli:item" nillable="true" xbrli:periodType="duration" abstract="false" />
  <xsd:element name="InvestorsPurchaseAgreementMember" id="bcyc_InvestorsPurchaseAgreementMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" nillable="true" xbrli:periodType="duration" abstract="true" />
  <xsd:element name="GainLossOnExtinguishmentOfResearchAndDevelopmentFundingLiability" id="bcyc_GainLossOnExtinguishmentOfResearchAndDevelopmentFundingLiability" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" nillable="true" xbrli:periodType="duration" abstract="false" xbrli:balance="credit" />
  <xsd:element name="FinanceLeaseCost" id="bcyc_FinanceLeaseCost" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" nillable="true" xbrli:periodType="duration" abstract="false" xbrli:balance="debit" />
  <xsd:element name="DeferredTaxAssetDepreciationAndAmortization" id="bcyc_DeferredTaxAssetDepreciationAndAmortization" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" nillable="true" xbrli:periodType="instant" abstract="false" xbrli:balance="debit" />
  <xsd:element name="ResearchAndDevelopmentArrangementUpfrontCashPayment" id="bcyc_ResearchAndDevelopmentArrangementUpfrontCashPayment" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" nillable="true" xbrli:periodType="duration" abstract="false" xbrli:balance="debit" />
  <xsd:element name="SingleReportableSegmentMember" id="bcyc_SingleReportableSegmentMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" nillable="true" xbrli:periodType="duration" abstract="true" />
  <xsd:element name="InternalProgramProductCandidateBicycleToxinConjugateMoleculeBT8009Member" id="bcyc_InternalProgramProductCandidateBicycleToxinConjugateMoleculeBT8009Member" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" nillable="true" xbrli:periodType="duration" abstract="true" />
  <xsd:element name="InternalProgramProductCandidateBicycleToxinConjugateMoleculeBT5528Member" id="bcyc_InternalProgramProductCandidateBicycleToxinConjugateMoleculeBT5528Member" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" nillable="true" xbrli:periodType="duration" abstract="true" />
  <xsd:element name="InternalProgramBicycleTumorTargetedImmuneCellAgonistsBT7480Member" id="bcyc_InternalProgramBicycleTumorTargetedImmuneCellAgonistsBT7480Member" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" nillable="true" xbrli:periodType="duration" abstract="true" />
  <xsd:element name="ProjectSpecificCosts" id="bcyc_ProjectSpecificCosts" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" nillable="true" xbrli:periodType="duration" abstract="false" xbrli:balance="debit" />
  <xsd:element name="ResearchAndDevelopmentDiscoveryPlatformAndOtherExpenses" id="bcyc_ResearchAndDevelopmentDiscoveryPlatformAndOtherExpenses" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" nillable="true" xbrli:periodType="duration" abstract="false" xbrli:balance="debit" />
  <xsd:element name="ResearchAndDevelopmentEmployeeAndContractorRelatedExpenses" id="bcyc_ResearchAndDevelopmentEmployeeAndContractorRelatedExpenses" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" nillable="true" xbrli:periodType="duration" abstract="false" xbrli:balance="debit" />
  <xsd:element name="ResearchAndDevelopmentShareBasedPaymentArrangementExpense" id="bcyc_ResearchAndDevelopmentShareBasedPaymentArrangementExpense" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" nillable="true" xbrli:periodType="duration" abstract="false" xbrli:balance="debit" />
  <xsd:element name="FacilityExpenses" id="bcyc_FacilityExpenses" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" nillable="true" xbrli:periodType="duration" abstract="false" xbrli:balance="debit" />
  <xsd:element name="ResearchAndDevelopmentTaxCreditsIncentivesAndGovernmentGrants" id="bcyc_ResearchAndDevelopmentTaxCreditsIncentivesAndGovernmentGrants" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" nillable="true" xbrli:periodType="duration" abstract="false" xbrli:balance="credit" />
  <xsd:element name="GeneralAndAdministrativeShareBasedPaymentArrangementExpense" id="bcyc_GeneralAndAdministrativeShareBasedPaymentArrangementExpense" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" nillable="true" xbrli:periodType="duration" abstract="false" xbrli:balance="debit" />
  <xsd:element name="ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsOutstandingNumber" id="bcyc_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsOutstandingNumber" type="xbrli:sharesItemType" substitutionGroup="xbrli:item" nillable="true" xbrli:periodType="instant" abstract="false" />
  <xsd:element name="ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsOutstandingWeightedAverageGrantDateFairValue" id="bcyc_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsOutstandingWeightedAverageGrantDateFairValue" type="dtr-types:perShareItemType" substitutionGroup="xbrli:item" nillable="true" xbrli:periodType="instant" abstract="false" />
  <xsd:element name="AlethiaYoungMember" id="bcyc_AlethiaYoungMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" nillable="true" xbrli:periodType="duration" abstract="true" />
  <xsd:element name="CostReductionInitiativesMember" id="bcyc_CostReductionInitiativesMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" nillable="true" xbrli:periodType="duration" abstract="true" />
  <xsd:element name="DiscoveryResearchActivitiesConsolidationMember" id="bcyc_DiscoveryResearchActivitiesConsolidationMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" nillable="true" xbrli:periodType="duration" abstract="true" />
  <xsd:element name="EffectiveIncomeTaxReconciliationNetLossesSurrenderedForResearchCredit" id="bcyc_EffectiveIncomeTaxReconciliationNetLossesSurrenderedForResearchCredit" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" nillable="true" xbrli:periodType="duration" abstract="false" xbrli:balance="debit" />
  <xsd:element name="CharlesSwantonMember" id="bcyc_CharlesSwantonMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" nillable="true" xbrli:periodType="duration" abstract="true" />
  <xsd:element name="NumberOfResearchProgramsNoticeOfTerminationReceived" id="bcyc_NumberOfResearchProgramsNoticeOfTerminationReceived" type="xbrli:integerItemType" substitutionGroup="xbrli:item" nillable="true" xbrli:periodType="duration" abstract="false" />
  <xsd:element name="CollaborativeResearchPlanResearchAndDiscoveryActivitiesTerm" id="bcyc_CollaborativeResearchPlanResearchAndDiscoveryActivitiesTerm" type="xbrli:durationItemType" substitutionGroup="xbrli:item" nillable="true" xbrli:periodType="duration" abstract="false" />
  <xsd:element name="LeaseRentFreePeriod" id="bcyc_LeaseRentFreePeriod" type="xbrli:durationItemType" substitutionGroup="xbrli:item" nillable="true" xbrli:periodType="duration" abstract="false" />
  <xsd:element name="RestructuringAndRelatedCostExpectedCostReductionPercent" id="bcyc_RestructuringAndRelatedCostExpectedCostReductionPercent" type="dtr-types:percentItemType" substitutionGroup="xbrli:item" nillable="true" xbrli:periodType="duration" abstract="false" />
  <xsd:element name="ContractWithCustomerLiabilityRevenueRecognizedContractModificationsAndExpirationOfMaterialRights" id="bcyc_ContractWithCustomerLiabilityRevenueRecognizedContractModificationsAndExpirationOfMaterialRights" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" nillable="true" xbrli:periodType="duration" abstract="false" xbrli:balance="credit" />
</xsd:schema>
