<?xml version="1.0" encoding="UTF-8"?>

<!--XBRL Document Created with Wdesk from Workiva-->
<!--Copyright 2023 Workiva-->
<!--r:778033de-956c-4b5d-a8a3-d666791c6d0f,g:ce06bd80-0783-4e34-aed8-37c9947f8bff-->
<xs:schema xmlns:xs="http://www.w3.org/2001/XMLSchema" xmlns:link="http://www.xbrl.org/2003/linkbase" xmlns:cccc="http://c4therapeutics.com/20221231" xmlns:xbrli="http://www.xbrl.org/2003/instance" xmlns:dtr-types="http://www.xbrl.org/dtr/type/2020-01-21" xmlns:xbrldt="http://xbrl.org/2005/xbrldt" attributeFormDefault="unqualified" elementFormDefault="qualified" targetNamespace="http://c4therapeutics.com/20221231">
  <xs:import namespace="http://fasb.org/srt/2022" schemaLocation="https://xbrl.fasb.org/srt/2022/elts/srt-2022.xsd"/>
  <xs:import namespace="http://fasb.org/us-gaap/2022" schemaLocation="https://xbrl.fasb.org/us-gaap/2022/elts/us-gaap-2022.xsd"/>
  <xs:import namespace="http://www.w3.org/1999/xlink" schemaLocation="http://www.xbrl.org/2003/xlink-2003-12-31.xsd"/>
  <xs:import namespace="http://www.xbrl.org/2003/instance" schemaLocation="http://www.xbrl.org/2003/xbrl-instance-2003-12-31.xsd"/>
  <xs:import namespace="http://www.xbrl.org/2003/linkbase" schemaLocation="http://www.xbrl.org/2003/xbrl-linkbase-2003-12-31.xsd"/>
  <xs:import namespace="http://www.xbrl.org/dtr/type/2020-01-21" schemaLocation="https://www.xbrl.org/dtr/type/2020-01-21/types.xsd"/>
  <xs:import namespace="http://xbrl.org/2005/xbrldt" schemaLocation="http://www.xbrl.org/2005/xbrldt-2005.xsd"/>
  <xs:import namespace="http://xbrl.sec.gov/dei/2022" schemaLocation="https://xbrl.sec.gov/dei/2022/dei-2022.xsd"/>
  <xs:annotation>
    <xs:appinfo>
      <link:linkbaseRef xmlns:xlink="http://www.w3.org/1999/xlink" xlink:arcrole="http://www.w3.org/1999/xlink/properties/linkbase" xlink:href="cccc-20221231_lab.xml" xlink:role="http://www.xbrl.org/2003/role/labelLinkbaseRef" xlink:type="simple"/>
      <link:linkbaseRef xmlns:xlink="http://www.w3.org/1999/xlink" xlink:arcrole="http://www.w3.org/1999/xlink/properties/linkbase" xlink:href="cccc-20221231_pre.xml" xlink:role="http://www.xbrl.org/2003/role/presentationLinkbaseRef" xlink:type="simple"/>
      <link:linkbaseRef xmlns:xlink="http://www.w3.org/1999/xlink" xlink:arcrole="http://www.w3.org/1999/xlink/properties/linkbase" xlink:href="cccc-20221231_cal.xml" xlink:role="http://www.xbrl.org/2003/role/calculationLinkbaseRef" xlink:type="simple"/>
      <link:linkbaseRef xmlns:xlink="http://www.w3.org/1999/xlink" xlink:arcrole="http://www.w3.org/1999/xlink/properties/linkbase" xlink:href="cccc-20221231_def.xml" xlink:role="http://www.xbrl.org/2003/role/definitionLinkbaseRef" xlink:type="simple"/>
      <link:roleType id="Cover" roleURI="http://c4therapeutics.com/role/Cover">
        <link:definition>0000001 - Document - Cover</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="AuditInformation" roleURI="http://c4therapeutics.com/role/AuditInformation">
        <link:definition>0000002 - Document - Audit 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 id="ConsolidatedBalanceSheets" roleURI="http://c4therapeutics.com/role/ConsolidatedBalanceSheets">
        <link:definition>0000003 - 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 id="ConsolidatedBalanceSheetsParenthetical" roleURI="http://c4therapeutics.com/role/ConsolidatedBalanceSheetsParenthetical">
        <link:definition>0000004 - 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 id="ConsolidatedStatementsofOperationsandComprehensiveLoss" roleURI="http://c4therapeutics.com/role/ConsolidatedStatementsofOperationsandComprehensiveLoss">
        <link:definition>0000005 - 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 id="ConsolidatedStatementsofStockholdersEquity" roleURI="http://c4therapeutics.com/role/ConsolidatedStatementsofStockholdersEquity">
        <link:definition>0000006 - Statement - Consolidated Statements of Stockholders' 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 id="ConsolidatedStatementsofStockholdersEquityParenthetical" roleURI="http://c4therapeutics.com/role/ConsolidatedStatementsofStockholdersEquityParenthetical">
        <link:definition>0000007 - Statement - Consolidated Statements of Stockholders' 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 id="ConsolidatedStatementsofCashFlows" roleURI="http://c4therapeutics.com/role/ConsolidatedStatementsofCashFlows">
        <link:definition>0000008 - 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 id="ConsolidatedStatementsofCashFlowsParenthetical" roleURI="http://c4therapeutics.com/role/ConsolidatedStatementsofCashFlowsParenthetical">
        <link:definition>0000009 - Statement - Consolidated Statements of Cash Flows (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 id="Natureofthebusiness" roleURI="http://c4therapeutics.com/role/Natureofthebusiness">
        <link:definition>0000010 - Disclosure - Nature of the business</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="Summaryofsignificantaccountingpolicies" roleURI="http://c4therapeutics.com/role/Summaryofsignificantaccountingpolicies">
        <link:definition>0000011 - 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 id="Fairvaluemeasurements" roleURI="http://c4therapeutics.com/role/Fairvaluemeasurements">
        <link:definition>0000012 - Disclosure - Fair value measurements</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="Marketablesecurities" roleURI="http://c4therapeutics.com/role/Marketablesecurities">
        <link:definition>0000013 - Disclosure - Marketable securities</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="Propertyandequipment" roleURI="http://c4therapeutics.com/role/Propertyandequipment">
        <link:definition>0000014 - Disclosure - Property and equipment</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="Leases" roleURI="http://c4therapeutics.com/role/Leases">
        <link:definition>0000015 - Disclosure - Leases</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="Accruedexpensesandothercurrentliabilities" roleURI="http://c4therapeutics.com/role/Accruedexpensesandothercurrentliabilities">
        <link:definition>0000016 - 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 id="Collaborationandlicenseagreements" roleURI="http://c4therapeutics.com/role/Collaborationandlicenseagreements">
        <link:definition>0000017 - Disclosure - Collaboration and license 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 id="Longtermdebtandwarrantrelatedparty" roleURI="http://c4therapeutics.com/role/Longtermdebtandwarrantrelatedparty">
        <link:definition>0000018 - Disclosure - Long-term debt and warrant &#8211; related party</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="Stockholdersequity" roleURI="http://c4therapeutics.com/role/Stockholdersequity">
        <link:definition>0000019 - Disclosure - Stockholders 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 id="Stockbasedcompensation" roleURI="http://c4therapeutics.com/role/Stockbasedcompensation">
        <link:definition>0000020 - Disclosure - Stock-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 id="IncomeTaxes" roleURI="http://c4therapeutics.com/role/IncomeTaxes">
        <link:definition>0000021 - 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 id="NetLosspershare" roleURI="http://c4therapeutics.com/role/NetLosspershare">
        <link:definition>0000022 - 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 id="Definedcontributionplan" roleURI="http://c4therapeutics.com/role/Definedcontributionplan">
        <link:definition>0000023 - Disclosure - Defined contribution plan</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
      <link:roleType id="SummaryofsignificantaccountingpoliciesPolicies" roleURI="http://c4therapeutics.com/role/SummaryofsignificantaccountingpoliciesPolicies">
        <link:definition>0000024 - 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 id="SummaryofsignificantaccountingpoliciesTables" roleURI="http://c4therapeutics.com/role/SummaryofsignificantaccountingpoliciesTables">
        <link:definition>0000025 - 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 id="FairvaluemeasurementsTables" roleURI="http://c4therapeutics.com/role/FairvaluemeasurementsTables">
        <link:definition>0000026 - Disclosure - Fair value measurements (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 id="MarketablesecuritiesTables" roleURI="http://c4therapeutics.com/role/MarketablesecuritiesTables">
        <link:definition>0000027 - Disclosure - Marketable securities (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 id="PropertyandequipmentTables" roleURI="http://c4therapeutics.com/role/PropertyandequipmentTables">
        <link:definition>0000028 - Disclosure - Property and equipment (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 id="LeasesTables" roleURI="http://c4therapeutics.com/role/LeasesTables">
        <link:definition>0000029 - Disclosure - Leases (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 id="AccruedexpensesandothercurrentliabilitiesTables" roleURI="http://c4therapeutics.com/role/AccruedexpensesandothercurrentliabilitiesTables">
        <link:definition>0000030 - 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 id="CollaborationandlicenseagreementsTables" roleURI="http://c4therapeutics.com/role/CollaborationandlicenseagreementsTables">
        <link:definition>0000031 - Disclosure - Collaboration and license 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 id="LongtermdebtandwarrantrelatedpartyTables" roleURI="http://c4therapeutics.com/role/LongtermdebtandwarrantrelatedpartyTables">
        <link:definition>0000032 - Disclosure - Long-term debt and warrant &#8211; related party (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 id="StockbasedcompensationTables" roleURI="http://c4therapeutics.com/role/StockbasedcompensationTables">
        <link:definition>0000033 - Disclosure - Stock-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 id="IncomeTaxesTables" roleURI="http://c4therapeutics.com/role/IncomeTaxesTables">
        <link:definition>0000034 - 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 id="NetLosspershareTables" roleURI="http://c4therapeutics.com/role/NetLosspershareTables">
        <link:definition>0000035 - 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 id="NatureofthebusinessDetails" roleURI="http://c4therapeutics.com/role/NatureofthebusinessDetails">
        <link:definition>0000036 - Disclosure - Nature of the business (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 id="SummaryofsignificantaccountingpoliciesNarrativeDetails" roleURI="http://c4therapeutics.com/role/SummaryofsignificantaccountingpoliciesNarrativeDetails">
        <link:definition>0000037 - Disclosure - Summary of significant accounting policies - Narrative (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 id="SummaryofsignificantaccountingpoliciesSummaryofpropertyandequipmentusefullivesDetails" roleURI="http://c4therapeutics.com/role/SummaryofsignificantaccountingpoliciesSummaryofpropertyandequipmentusefullivesDetails">
        <link:definition>0000038 - Disclosure - Summary of significant accounting policies- Summary of property and equipment - useful lives (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 id="FairvaluemeasurementsDetails" roleURI="http://c4therapeutics.com/role/FairvaluemeasurementsDetails">
        <link:definition>0000039 - Disclosure - Fair value measurements (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 id="MarketablesecuritiesSummaryofmarketablesecuritiesDetails" roleURI="http://c4therapeutics.com/role/MarketablesecuritiesSummaryofmarketablesecuritiesDetails">
        <link:definition>0000040 - Disclosure - Marketable securities - Summary of marketable securities (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 id="MarketablesecuritiesSummaryofmarketablesecuritiesDetails_1" roleURI="http://c4therapeutics.com/role/MarketablesecuritiesSummaryofmarketablesecuritiesDetails_1">
        <link:definition>0000040 - Disclosure - Marketable securities - Summary of marketable securities (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 id="MarketablesecuritiesSummaryofmarketablesecuritiesinunrealizedlosspositionDetails" roleURI="http://c4therapeutics.com/role/MarketablesecuritiesSummaryofmarketablesecuritiesinunrealizedlosspositionDetails">
        <link:definition>0000041 - Disclosure - Marketable securities - Summary of marketable securities in unrealized loss position (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 id="MarketablesecuritiesNarrativeDetails" roleURI="http://c4therapeutics.com/role/MarketablesecuritiesNarrativeDetails">
        <link:definition>0000042 - Disclosure - Marketable securities - Narrative (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 id="PropertyandequipmentSummaryofpropertyandequipmentDetails" roleURI="http://c4therapeutics.com/role/PropertyandequipmentSummaryofpropertyandequipmentDetails">
        <link:definition>0000043 - Disclosure - Property and equipment - Summary of property and equipment (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 id="PropertyandequipmentSummaryofdepreciationexpenseDetails" roleURI="http://c4therapeutics.com/role/PropertyandequipmentSummaryofdepreciationexpenseDetails">
        <link:definition>0000044 - Disclosure - Property and equipment - Summary of depreciation 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 id="LeasesNarrativeDetails" roleURI="http://c4therapeutics.com/role/LeasesNarrativeDetails">
        <link:definition>0000045 - Disclosure - Leases - Narrative (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 id="LeasesSummaryofleasecostsDetails" roleURI="http://c4therapeutics.com/role/LeasesSummaryofleasecostsDetails">
        <link:definition>0000046 - Disclosure - Leases - Summary of lease costs (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 id="LeasesSummaryofleasetermandincrementalborrowingrateDetails" roleURI="http://c4therapeutics.com/role/LeasesSummaryofleasetermandincrementalborrowingrateDetails">
        <link:definition>0000047 - Disclosure - Leases - Summary of lease term and incremental borrowing rate (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 id="LeasesSummaryoffutureleasepaymentsDetails" roleURI="http://c4therapeutics.com/role/LeasesSummaryoffutureleasepaymentsDetails">
        <link:definition>0000048 - Disclosure - Leases - Summary of future lease payments (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 id="LeasesSummaryoffutureleasepaymentsDetails_1" roleURI="http://c4therapeutics.com/role/LeasesSummaryoffutureleasepaymentsDetails_1">
        <link:definition>0000048 - Disclosure - Leases - Summary of future lease payments (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 id="AccruedexpensesandothercurrentliabilitiesDetails" roleURI="http://c4therapeutics.com/role/AccruedexpensesandothercurrentliabilitiesDetails">
        <link:definition>0000049 - 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 id="CollaborationandlicenseagreementsNarrativeDetails" roleURI="http://c4therapeutics.com/role/CollaborationandlicenseagreementsNarrativeDetails">
        <link:definition>0000050 - Disclosure - Collaboration and license agreements - Narrative (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 id="CollaborationandlicenseagreementsAllocationoftotaltransactionpriceandunsatisfiedtransactionpriceDetails" roleURI="http://c4therapeutics.com/role/CollaborationandlicenseagreementsAllocationoftotaltransactionpriceandunsatisfiedtransactionpriceDetails">
        <link:definition>0000051 - Disclosure - Collaboration and license agreements - Allocation of total transaction price and unsatisfied transaction price (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 id="CollaborationandlicenseagreementsScheduleofrevenuefromcollaborationagreementsDetails" roleURI="http://c4therapeutics.com/role/CollaborationandlicenseagreementsScheduleofrevenuefromcollaborationagreementsDetails">
        <link:definition>0000052 - Disclosure - Collaboration and license agreements - Schedule of revenue from collaboration agreements (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 id="CollaborationandlicenseagreementsScheduleoffinancialinformationrelatedtocollaborationandlicenseagreementsDetails" roleURI="http://c4therapeutics.com/role/CollaborationandlicenseagreementsScheduleoffinancialinformationrelatedtocollaborationandlicenseagreementsDetails">
        <link:definition>0000053 - Disclosure - Collaboration and license agreements - Schedule of financial information related to collaboration and license agreements (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 id="CollaborationandlicenseagreementsScheduleofsupplementalfinancialinformationrelatedtocollaborationandlicenseagreementsDetails" roleURI="http://c4therapeutics.com/role/CollaborationandlicenseagreementsScheduleofsupplementalfinancialinformationrelatedtocollaborationandlicenseagreementsDetails">
        <link:definition>0000054 - Disclosure - Collaboration and license agreements - Schedule of supplemental financial information related to collaboration and license agreements (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 id="LongtermdebtandwarrantrelatedpartyNarrativeDetails" roleURI="http://c4therapeutics.com/role/LongtermdebtandwarrantrelatedpartyNarrativeDetails">
        <link:definition>0000055 - Disclosure - Long-term debt and warrant &#8211; related party - Narrative (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 id="LongtermdebtandwarrantrelatedpartySummaryoffutureminimumpaymentsDetails" roleURI="http://c4therapeutics.com/role/LongtermdebtandwarrantrelatedpartySummaryoffutureminimumpaymentsDetails">
        <link:definition>0000056 - Disclosure - Long-term debt and warrant &#8211; related party - Summary of future minimum payments (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 id="StockholdersequityDetails" roleURI="http://c4therapeutics.com/role/StockholdersequityDetails">
        <link:definition>0000057 - Disclosure - Stockholder's equity (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 id="StockbasedcompensationNarrativeDetails" roleURI="http://c4therapeutics.com/role/StockbasedcompensationNarrativeDetails">
        <link:definition>0000058 - Disclosure - Stock-based compensation - Narrative (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 id="StockbasedcompensationScheduleofstockbasedcompensationexpenseDetails" roleURI="http://c4therapeutics.com/role/StockbasedcompensationScheduleofstockbasedcompensationexpenseDetails">
        <link:definition>0000059 - Disclosure - Stock-based compensation - Schedule of stock-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 id="StockbasedcompensationSummaryofstockoptionactivityDetails" roleURI="http://c4therapeutics.com/role/StockbasedcompensationSummaryofstockoptionactivityDetails">
        <link:definition>0000060 - Disclosure - Stock-based compensation - Summary of stock option 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 id="StockbasedcompensationSummaryofstockoptionactivityotherinformationDetails" roleURI="http://c4therapeutics.com/role/StockbasedcompensationSummaryofstockoptionactivityotherinformationDetails">
        <link:definition>0000061 - Disclosure - Stock-based compensation - Summary of stock option activity - other 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 id="StockbasedcompensationSummaryofsignificantvaluationassumptionsDetails" roleURI="http://c4therapeutics.com/role/StockbasedcompensationSummaryofsignificantvaluationassumptionsDetails">
        <link:definition>0000062 - Disclosure - Stock-based compensation - Summary of significant valuation assumptions (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 id="StockbasedcompensationSummaryofRSUactivityDetails" roleURI="http://c4therapeutics.com/role/StockbasedcompensationSummaryofRSUactivityDetails">
        <link:definition>0000063 - Disclosure - Stock-based compensation - Summary of RSU 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 id="IncomeTaxesSummaryofincometaxbenefitexpenseDetails" roleURI="http://c4therapeutics.com/role/IncomeTaxesSummaryofincometaxbenefitexpenseDetails">
        <link:definition>0000064 - Disclosure - Income Taxes - Summary of income tax (benefit) 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 id="IncomeTaxesScheduleofeffectiveincometaxratereconciliationDetails" roleURI="http://c4therapeutics.com/role/IncomeTaxesScheduleofeffectiveincometaxratereconciliationDetails">
        <link:definition>0000065 - Disclosure - Income Taxes - Schedule of effective income tax rate reconciliation (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 id="IncomeTaxesScheduleofdeferredtaxassetsandliabilitiesDetails" roleURI="http://c4therapeutics.com/role/IncomeTaxesScheduleofdeferredtaxassetsandliabilitiesDetails">
        <link:definition>0000066 - Disclosure - Income Taxes - Schedule of deferred tax 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 id="IncomeTaxesNarrativeDetails" roleURI="http://c4therapeutics.com/role/IncomeTaxesNarrativeDetails">
        <link:definition>0000067 - Disclosure - Income Taxes - Narrative (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 id="NetLosspershareScheduleofantidilutivesecuritiesexcludedfromcomputationofearningspershareDetails" roleURI="http://c4therapeutics.com/role/NetLosspershareScheduleofantidilutivesecuritiesexcludedfromcomputationofearningspershareDetails">
        <link:definition>0000068 - Disclosure - Net Loss per share - Schedule of antidilutive securities excluded from computation of earnings 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:roleType id="NetLosspershareScheduleofbasicanddilutedlosspershareDetails" roleURI="http://c4therapeutics.com/role/NetLosspershareScheduleofbasicanddilutedlosspershareDetails">
        <link:definition>0000069 - Disclosure - Net Loss per share - Schedule of basic and diluted 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:roleType id="DefinedcontributionplanDetails" roleURI="http://c4therapeutics.com/role/DefinedcontributionplanDetails">
        <link:definition>0000070 - Disclosure - Defined contribution plan (Details)</link:definition>
        <link:usedOn>link:presentationLink</link:usedOn>
        <link:usedOn>link:calculationLink</link:usedOn>
        <link:usedOn>link:definitionLink</link:usedOn>
      </link:roleType>
    </xs:appinfo>
  </xs:annotation>
  <xs:element id="cccc_MilestoneEarnedOnPerformanceObligation" abstract="false" name="MilestoneEarnedOnPerformanceObligation" nillable="true" xbrli:periodType="duration" xbrli:balance="credit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="cccc_AnnualResearchPlanPaymentsReceivables" abstract="false" name="AnnualResearchPlanPaymentsReceivables" nillable="true" xbrli:periodType="instant" xbrli:balance="credit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="cccc_RocheAgreementMember" abstract="true" name="RocheAgreementMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="cccc_CalicoLicenseAgreementMember" abstract="true" name="CalicoLicenseAgreementMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="cccc_NewlyLeasedSpaceMember" abstract="true" name="NewlyLeasedSpaceMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="cccc_RevenueFromCollaborationAgreementsTableTableTextBlock" abstract="false" name="RevenueFromCollaborationAgreementsTableTableTextBlock" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:textBlockItemType"/>
  <xs:element id="cccc_DebtSecuritiesAvailableForSaleAccumulatedGrossUnrealizedLossBeforeTaxNoncurrent" abstract="false" name="DebtSecuritiesAvailableForSaleAccumulatedGrossUnrealizedLossBeforeTaxNoncurrent" nillable="true" xbrli:periodType="instant" xbrli:balance="debit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="cccc_NonRefundableUpfrontPayment" abstract="false" name="NonRefundableUpfrontPayment" nillable="true" xbrli:periodType="duration" xbrli:balance="debit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="cccc_NumberOfPerformanceObligation" abstract="false" name="NumberOfPerformanceObligation" nillable="true" xbrli:periodType="instant" substitutionGroup="xbrli:item" type="xbrli:integerItemType"/>
  <xs:element id="cccc_ScheduleOfDepreciationExpenseTableTableTextBlock" abstract="false" name="ScheduleOfDepreciationExpenseTableTableTextBlock" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:textBlockItemType"/>
  <xs:element id="cccc_OptionRightsMember" abstract="true" name="OptionRightsMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="cccc_TwoThousandFifteenIncentiveStockOptionAndGrantPlanMember" abstract="true" name="TwoThousandFifteenIncentiveStockOptionAndGrantPlanMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="cccc_TransactionPriceUnsatisfiedToPerformanceObligation" abstract="false" name="TransactionPriceUnsatisfiedToPerformanceObligation" nillable="true" xbrli:periodType="instant" xbrli:balance="credit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="cccc_TwoThousandTwentyEmployeeStockPurchasePlanMember" abstract="true" name="TwoThousandTwentyEmployeeStockPurchasePlanMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="cccc_MaximumAuthorizedPayrollDeductionPercentageOfEligibleCompensationForEligibleEmployees" abstract="false" name="MaximumAuthorizedPayrollDeductionPercentageOfEligibleCompensationForEligibleEmployees" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:percentItemType"/>
  <xs:element id="cccc_TransactionPriceAllocatedToPerformanceObligation" abstract="false" name="TransactionPriceAllocatedToPerformanceObligation" nillable="true" xbrli:periodType="instant" xbrli:balance="credit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="cccc_ResearchExtendedTerm" abstract="false" name="ResearchExtendedTerm" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="xbrli:durationItemType"/>
  <xs:element id="cccc_CreditAgreementWithPerceptiveLifeSciencesMasterFundLTDMember" abstract="true" name="CreditAgreementWithPerceptiveLifeSciencesMasterFundLTDMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="cccc_DebtSecuritiesAvailableForSaleCurrentAbstract" abstract="true" name="DebtSecuritiesAvailableForSaleCurrentAbstract" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="xbrli:stringItemType"/>
  <xs:element id="cccc_TermLoanMember" abstract="true" name="TermLoanMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="cccc_DeferredTaxAssetsCapitalizedResearchAndDevelopmentExpenditures" abstract="false" name="DeferredTaxAssetsCapitalizedResearchAndDevelopmentExpenditures" nillable="true" xbrli:periodType="instant" xbrli:balance="debit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="cccc_LongTermDebtAndWarrantRelatedPartyTextBlock" abstract="false" name="LongTermDebtAndWarrantRelatedPartyTextBlock" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:textBlockItemType"/>
  <xs:element id="cccc_BiogenLicenseAgreementMember" abstract="true" name="BiogenLicenseAgreementMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="cccc_NumberOfAdditionalTargets" abstract="false" name="NumberOfAdditionalTargets" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="xbrli:integerItemType"/>
  <xs:element id="cccc_IncomeTaxLineItems" abstract="true" name="IncomeTaxLineItems" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="xbrli:stringItemType"/>
  <xs:element id="cccc_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfCommonSharesIssuablePerVested" abstract="false" name="ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfCommonSharesIssuablePerVested" nillable="true" xbrli:periodType="instant" substitutionGroup="xbrli:item" type="xbrli:sharesItemType"/>
  <xs:element id="cccc_ResearchAndDevelopmentAgreementPeriod" abstract="false" name="ResearchAndDevelopmentAgreementPeriod" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="xbrli:durationItemType"/>
  <xs:element id="cccc_GoingConcernPolicyPolicyTextBlock" abstract="false" name="GoingConcernPolicyPolicyTextBlock" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:textBlockItemType"/>
  <xs:element id="cccc_NoticePeriodForTerminationOfAgreement" abstract="false" name="NoticePeriodForTerminationOfAgreement" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="xbrli:durationItemType"/>
  <xs:element id="cccc_OptionExerciseFee" abstract="false" name="OptionExerciseFee" nillable="true" xbrli:periodType="duration" xbrli:balance="debit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="cccc_AdditionalUpfrontConsideration" abstract="false" name="AdditionalUpfrontConsideration" nillable="true" xbrli:periodType="duration" xbrli:balance="credit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="cccc_CollaborativeArrangementOptionExerciseFeesThroughPhase1Trials" abstract="false" name="CollaborativeArrangementOptionExerciseFeesThroughPhase1Trials" nillable="true" xbrli:periodType="duration" xbrli:balance="debit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="cccc_ResearchAndDevelopmentMilestonesMember" abstract="true" name="ResearchAndDevelopmentMilestonesMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="cccc_ContractualTerm" abstract="false" name="ContractualTerm" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="xbrli:durationItemType"/>
  <xs:element id="cccc_TwoThousandAndTwentyStockOptionAndIncentivePlanMember" abstract="true" name="TwoThousandAndTwentyStockOptionAndIncentivePlanMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="cccc_RestatedRocheAgreementMember" abstract="true" name="RestatedRocheAgreementMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="cccc_CashBalanceToBeMaintainedInBankAccountWhileDebtIsOutstanding" abstract="false" name="CashBalanceToBeMaintainedInBankAccountWhileDebtIsOutstanding" nillable="true" xbrli:periodType="instant" xbrli:balance="debit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="cccc_LeaseTermOfAmendedLeaseTerminatePeriod" abstract="false" name="LeaseTermOfAmendedLeaseTerminatePeriod" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="xbrli:durationItemType"/>
  <xs:element id="cccc_DebtInstrumentPercentageOfPrincipalPaymentUntilMaturity" abstract="false" name="DebtInstrumentPercentageOfPrincipalPaymentUntilMaturity" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:percentItemType"/>
  <xs:element id="cccc_NumberOfTargetProteins" abstract="false" name="NumberOfTargetProteins" nillable="true" xbrli:periodType="instant" substitutionGroup="xbrli:item" type="xbrli:integerItemType"/>
  <xs:element id="cccc_ResearchAndDevelopmentServicesMember" abstract="true" name="ResearchAndDevelopmentServicesMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="cccc_FollowOnOfferingMember" abstract="true" name="FollowOnOfferingMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="cccc_ProceedsFromIssuanceOfFollowOnOffering" abstract="false" name="ProceedsFromIssuanceOfFollowOnOffering" nillable="true" xbrli:periodType="duration" xbrli:balance="debit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="cccc_UpfrontFees" abstract="false" name="UpfrontFees" nillable="true" xbrli:periodType="duration" xbrli:balance="credit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="cccc_DebtInstrumentFloorInterestRate" abstract="false" name="DebtInstrumentFloorInterestRate" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:percentItemType"/>
  <xs:element id="cccc_SupplementalFinancialInformationRelatedToCollaborationAndLicenseAgreementsTableTableTextBlock" abstract="false" name="SupplementalFinancialInformationRelatedToCollaborationAndLicenseAgreementsTableTableTextBlock" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:textBlockItemType"/>
  <xs:element id="cccc_LongTermDebtAndWarrantLiabilityTable" abstract="true" name="LongTermDebtAndWarrantLiabilityTable" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrldt:hypercubeItem" type="xbrli:stringItemType"/>
  <xs:element id="cccc_AggregateExercisePriceOfWarrantNetExercisedRelatedParty" abstract="false" name="AggregateExercisePriceOfWarrantNetExercisedRelatedParty" nillable="true" xbrli:periodType="duration" xbrli:balance="credit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="cccc_LaboratoryEquipmentMember" abstract="true" name="LaboratoryEquipmentMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="cccc_OneTimeSalesBasedPaymentsMember" abstract="true" name="OneTimeSalesBasedPaymentsMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="cccc_AmountPayableForExtendResearchTermOption" abstract="false" name="AmountPayableForExtendResearchTermOption" nillable="true" xbrli:periodType="duration" xbrli:balance="debit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="cccc_LongTermDebtAndWarrantLiabilityLineItems" abstract="true" name="LongTermDebtAndWarrantLiabilityLineItems" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="xbrli:stringItemType"/>
  <xs:element id="cccc_NumberOfTargetedProteinDegradation" abstract="false" name="NumberOfTargetedProteinDegradation" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="xbrli:integerItemType"/>
  <xs:element id="cccc_OptionsToPurchaseCommonStockMember" abstract="true" name="OptionsToPurchaseCommonStockMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="cccc_SummaryOfLeaseTermAndIncrementalBorrowingRateAppliedInArrivingAtLeaseLiabilityTableTableTextBlock" abstract="false" name="SummaryOfLeaseTermAndIncrementalBorrowingRateAppliedInArrivingAtLeaseLiabilityTableTableTextBlock" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:textBlockItemType"/>
  <xs:element id="cccc_FinancialInformationRelatedToCollaborationAndLicenseAgreementsTableTableTextBlock" abstract="false" name="FinancialInformationRelatedToCollaborationAndLicenseAgreementsTableTableTextBlock" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:textBlockItemType"/>
  <xs:element id="cccc_UpfrontPayment" abstract="false" name="UpfrontPayment" nillable="true" xbrli:periodType="duration" xbrli:balance="debit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="cccc_DeferredTaxAssetsOperatingLeaseLiability" abstract="false" name="DeferredTaxAssetsOperatingLeaseLiability" nillable="true" xbrli:periodType="instant" xbrli:balance="debit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="cccc_ResearchAndDevelopmentTargetsMember" abstract="true" name="ResearchAndDevelopmentTargetsMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="cccc_BiogenAgreementMember" abstract="true" name="BiogenAgreementMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="cccc_InterestExpenseAndAmortizationLongTermDebtRelatedParty" abstract="false" name="InterestExpenseAndAmortizationLongTermDebtRelatedParty" nillable="true" xbrli:periodType="duration" xbrli:balance="debit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="cccc_ShareBasedCompensationArrangementByShareBasedPaymentAwardCliffVestingPeriod" abstract="false" name="ShareBasedCompensationArrangementByShareBasedPaymentAwardCliffVestingPeriod" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="xbrli:durationItemType"/>
  <xs:element id="cccc_SummaryOfAllocationOfTotalTransactionPriceAndUnsatisfiedTransactionPriceTableTableTextBlock" abstract="false" name="SummaryOfAllocationOfTotalTransactionPriceAndUnsatisfiedTransactionPriceTableTableTextBlock" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:textBlockItemType"/>
  <xs:element id="cccc_StockIssuedDuringPeriodSharesWarrantExercisedRelatedParty" abstract="false" name="StockIssuedDuringPeriodSharesWarrantExercisedRelatedParty" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="xbrli:sharesItemType"/>
  <xs:element id="cccc_UnderwritersMember" abstract="true" name="UnderwritersMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="cccc_EffectiveIncomeTaxRateReconciliationTaxCutsAndJobsActPercent" abstract="false" name="EffectiveIncomeTaxRateReconciliationTaxCutsAndJobsActPercent" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:percentItemType"/>
  <xs:element id="cccc_EquityDistributionAgreementWithCowenAndCompanyLLCMember" abstract="true" name="EquityDistributionAgreementWithCowenAndCompanyLLCMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="cccc_DebtSecuritiesAvailableForSaleAccumulatedGrossUnrealizedGainBeforeTaxNoncurrent" abstract="false" name="DebtSecuritiesAvailableForSaleAccumulatedGrossUnrealizedGainBeforeTaxNoncurrent" nillable="true" xbrli:periodType="instant" xbrli:balance="credit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="cccc_RestatedRocheAgreementBiogenLicenseAgreementAndCalicoLicenseAgreementMember" abstract="true" name="RestatedRocheAgreementBiogenLicenseAgreementAndCalicoLicenseAgreementMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="cccc_DebtSecuritiesAvailableForSaleAccumulatedGrossUnrealizedGainBeforeTaxCurrent" abstract="false" name="DebtSecuritiesAvailableForSaleAccumulatedGrossUnrealizedGainBeforeTaxCurrent" nillable="true" xbrli:periodType="instant" xbrli:balance="credit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="cccc_BiogenResearchAndLicenseAgreementMember" abstract="true" name="BiogenResearchAndLicenseAgreementMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="cccc_NumberOfPotentialTargets" abstract="false" name="NumberOfPotentialTargets" nillable="true" xbrli:periodType="instant" substitutionGroup="xbrli:item" type="xbrli:integerItemType"/>
  <xs:element id="cccc_InitialContractualTermOnStraightLineBasis" abstract="false" name="InitialContractualTermOnStraightLineBasis" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="xbrli:durationItemType"/>
  <xs:element id="cccc_DebtSecuritiesAvailableForSaleNoncurrentAbstract" abstract="true" name="DebtSecuritiesAvailableForSaleNoncurrentAbstract" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="xbrli:stringItemType"/>
  <xs:element id="cccc_EffectiveIncomeTaxRateReconciliationFederalTaxCredit" abstract="false" name="EffectiveIncomeTaxRateReconciliationFederalTaxCredit" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:percentItemType"/>
  <xs:element id="cccc_ResearchTerm" abstract="false" name="ResearchTerm" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="xbrli:durationItemType"/>
  <xs:element id="cccc_AdditionalTransactionPriceAllocatedToPerformanceObligation" abstract="false" name="AdditionalTransactionPriceAllocatedToPerformanceObligation" nillable="true" xbrli:periodType="duration" xbrli:balance="credit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="cccc_OfficeAndLaboratorySpaceMember" abstract="true" name="OfficeAndLaboratorySpaceMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="cccc_SharesWithholdEquivalentToAggregateExercisePriceValue" abstract="false" name="SharesWithholdEquivalentToAggregateExercisePriceValue" nillable="true" xbrli:periodType="duration" xbrli:balance="credit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="cccc_CommonStockNumberOfVotesEachShare" abstract="false" name="CommonStockNumberOfVotesEachShare" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="xbrli:integerItemType"/>
  <xs:element id="cccc_DebtSecuritiesAvailableForSaleAccumulatedGrossUnrealizedLossBeforeTaxCurrent" abstract="false" name="DebtSecuritiesAvailableForSaleAccumulatedGrossUnrealizedLossBeforeTaxCurrent" nillable="true" xbrli:periodType="instant" xbrli:balance="debit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="cccc_GoodLaboratoryPracticeGlpToxicologyToxStudyPhaseMember" abstract="true" name="GoodLaboratoryPracticeGlpToxicologyToxStudyPhaseMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="cccc_AnnualResearchPlanPaymentsPeriods" abstract="false" name="AnnualResearchPlanPaymentsPeriods" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="xbrli:durationItemType"/>
  <xs:element id="cccc_AccruedResearchAndDevelopmentCurrent" abstract="false" name="AccruedResearchAndDevelopmentCurrent" nillable="true" xbrli:periodType="instant" xbrli:balance="credit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="cccc_OfficeEquipmentFurnitureAndFixturesMember" abstract="true" name="OfficeEquipmentFurnitureAndFixturesMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="cccc_WatertownLeaseMember" abstract="true" name="WatertownLeaseMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="cccc_DeferredTaxLiabilitiesRightOfUseAsset" abstract="false" name="DeferredTaxLiabilitiesRightOfUseAsset" nillable="true" xbrli:periodType="instant" xbrli:balance="credit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="cccc_AnnualPayments" abstract="false" name="AnnualPayments" nillable="true" xbrli:periodType="duration" xbrli:balance="debit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="cccc_PercentageOfOutstandingSharesOfCommonStock" abstract="false" name="PercentageOfOutstandingSharesOfCommonStock" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:percentItemType"/>
  <xs:element id="cccc_NumberOfAmendedLeaseSeparateContracts" abstract="false" name="NumberOfAmendedLeaseSeparateContracts" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="xbrli:integerItemType"/>
  <xs:element id="cccc_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfAnnualOfferingPeriods" abstract="false" name="ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfAnnualOfferingPeriods" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="xbrli:integerItemType"/>
  <xs:element id="cccc_IncomeTaxTable" abstract="true" name="IncomeTaxTable" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrldt:hypercubeItem" type="xbrli:stringItemType"/>
  <xs:element id="cccc_TrancheTwoMember" abstract="true" name="TrancheTwoMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="cccc_ResearchDevelopmentAndCommercialMilestonePaymentsMember" abstract="true" name="ResearchDevelopmentAndCommercialMilestonePaymentsMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="cccc_LesseeOperatingLeaseNumberOfRenewalOptions" abstract="false" name="LesseeOperatingLeaseNumberOfRenewalOptions" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="xbrli:integerItemType"/>
  <xs:element id="cccc_NetOperatingLossCarryforwardsLimitedAndExpiredDueToOwnershipChanges" abstract="false" name="NetOperatingLossCarryforwardsLimitedAndExpiredDueToOwnershipChanges" nillable="true" xbrli:periodType="instant" xbrli:balance="debit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="cccc_EffectiveIncomeTaxRateReconciliationStateTaxCredit" abstract="false" name="EffectiveIncomeTaxRateReconciliationStateTaxCredit" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:percentItemType"/>
  <xs:element id="cccc_TrancheOneMember" abstract="true" name="TrancheOneMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="cccc_AuditInformationAbstract" abstract="true" name="AuditInformationAbstract" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="xbrli:stringItemType"/>
  <xs:element id="cccc_AtmOfferingsMember" abstract="true" name="AtmOfferingsMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="cccc_AdjustmentsToAdditionalPaidInCapitalOtherShares" abstract="false" name="AdjustmentsToAdditionalPaidInCapitalOtherShares" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="xbrli:sharesItemType"/>
  <xs:element id="cccc_NumberOfTargets" abstract="false" name="NumberOfTargets" nillable="true" xbrli:periodType="instant" substitutionGroup="xbrli:item" type="xbrli:integerItemType"/>
  <xs:element id="cccc_CalicoAgreementMember" abstract="true" name="CalicoAgreementMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="cccc_LeadSeriesIdentificationAchievementMember" abstract="true" name="LeadSeriesIdentificationAchievementMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="cccc_PotentialResearchDevelopmentAndCommercialMilestonePaymentsMember" abstract="true" name="PotentialResearchDevelopmentAndCommercialMilestonePaymentsMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="cccc_DeferredTaxAssetsCapitalizedStartUpCosts" abstract="false" name="DeferredTaxAssetsCapitalizedStartUpCosts" nillable="true" xbrli:periodType="instant" xbrli:balance="debit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
</xs:schema>
