<?xml version="1.0" encoding="US-ASCII"?>
<!--XBRL Document Created with Wdesk from Workiva-->
<!-- -->
<link:linkbase xsi:schemaLocation="http://www.xbrl.org/2003/linkbase http://www.xbrl.org/2003/xbrl-linkbase-2003-12-31.xsd" xmlns:link="http://www.xbrl.org/2003/linkbase" xmlns:xbrldt="http://xbrl.org/2005/xbrldt" xmlns:xlink="http://www.w3.org/1999/xlink" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance">
  <link:roleRef roleURI="http://www.anaptysbio.com/role/AustraliaResearchAndDevelopmentTaxIncentive" xlink:href="anab-20180630.xsd#AustraliaResearchAndDevelopmentTaxIncentive" xlink:type="simple" />
  <link:roleRef roleURI="http://www.anaptysbio.com/role/AustraliaResearchAndDevelopmentTaxIncentiveDetails" xlink:href="anab-20180630.xsd#AustraliaResearchAndDevelopmentTaxIncentiveDetails" xlink:type="simple" />
  <link:roleRef roleURI="http://www.anaptysbio.com/role/BalanceSheetAccountsAndSupplementalDisclosures" xlink:href="anab-20180630.xsd#BalanceSheetAccountsAndSupplementalDisclosures" xlink:type="simple" />
  <link:roleRef roleURI="http://www.anaptysbio.com/role/BalanceSheetAccountsAndSupplementalDisclosuresAccruedExpensesDetails" xlink:href="anab-20180630.xsd#BalanceSheetAccountsAndSupplementalDisclosuresAccruedExpensesDetails" xlink:type="simple" />
  <link:roleRef roleURI="http://www.anaptysbio.com/role/BalanceSheetAccountsAndSupplementalDisclosuresPropertyAndEquipmentDetails" xlink:href="anab-20180630.xsd#BalanceSheetAccountsAndSupplementalDisclosuresPropertyAndEquipmentDetails" xlink:type="simple" />
  <link:roleRef roleURI="http://www.anaptysbio.com/role/BalanceSheetAccountsAndSupplementalDisclosuresTables" xlink:href="anab-20180630.xsd#BalanceSheetAccountsAndSupplementalDisclosuresTables" xlink:type="simple" />
  <link:roleRef roleURI="http://www.anaptysbio.com/role/CollaborativeResearchAndDevelopmentAgreements" xlink:href="anab-20180630.xsd#CollaborativeResearchAndDevelopmentAgreements" xlink:type="simple" />
  <link:roleRef roleURI="http://www.anaptysbio.com/role/CollaborativeResearchAndDevelopmentAgreementsDetails" xlink:href="anab-20180630.xsd#CollaborativeResearchAndDevelopmentAgreementsDetails" xlink:type="simple" />
  <link:roleRef roleURI="http://www.anaptysbio.com/role/CollaborativeResearchAndDevelopmentAgreementsTables" xlink:href="anab-20180630.xsd#CollaborativeResearchAndDevelopmentAgreementsTables" xlink:type="simple" />
  <link:roleRef roleURI="http://www.anaptysbio.com/role/CommitmentsAndContingencies" xlink:href="anab-20180630.xsd#CommitmentsAndContingencies" xlink:type="simple" />
  <link:roleRef roleURI="http://www.anaptysbio.com/role/CommitmentsAndContingenciesDetails" xlink:href="anab-20180630.xsd#CommitmentsAndContingenciesDetails" xlink:type="simple" />
  <link:roleRef roleURI="http://www.anaptysbio.com/role/CommitmentsAndContingenciesTables" xlink:href="anab-20180630.xsd#CommitmentsAndContingenciesTables" xlink:type="simple" />
  <link:roleRef roleURI="http://www.anaptysbio.com/role/ConsolidatedBalanceSheets" xlink:href="anab-20180630.xsd#ConsolidatedBalanceSheets" xlink:type="simple" />
  <link:roleRef roleURI="http://www.anaptysbio.com/role/ConsolidatedBalanceSheetsParenthetical" xlink:href="anab-20180630.xsd#ConsolidatedBalanceSheetsParenthetical" xlink:type="simple" />
  <link:roleRef roleURI="http://www.anaptysbio.com/role/ConsolidatedStatementsOfCashFlows" xlink:href="anab-20180630.xsd#ConsolidatedStatementsOfCashFlows" xlink:type="simple" />
  <link:roleRef roleURI="http://www.anaptysbio.com/role/ConsolidatedStatementsOfOperationsAndComprehensiveLoss" xlink:href="anab-20180630.xsd#ConsolidatedStatementsOfOperationsAndComprehensiveLoss" xlink:type="simple" />
  <link:roleRef roleURI="http://www.anaptysbio.com/role/DescriptionOfBusiness" xlink:href="anab-20180630.xsd#DescriptionOfBusiness" xlink:type="simple" />
  <link:roleRef roleURI="http://www.anaptysbio.com/role/DescriptionOfBusinessDetails" xlink:href="anab-20180630.xsd#DescriptionOfBusinessDetails" xlink:type="simple" />
  <link:roleRef roleURI="http://www.anaptysbio.com/role/DocumentAndEntityInformation" xlink:href="anab-20180630.xsd#DocumentAndEntityInformation" xlink:type="simple" />
  <link:roleRef roleURI="http://www.anaptysbio.com/role/EquityIncentivePlans" xlink:href="anab-20180630.xsd#EquityIncentivePlans" xlink:type="simple" />
  <link:roleRef roleURI="http://www.anaptysbio.com/role/EquityIncentivePlansAllocationOfShareBasedCompensationExpenseDetails" xlink:href="anab-20180630.xsd#EquityIncentivePlansAllocationOfShareBasedCompensationExpenseDetails" xlink:type="simple" />
  <link:roleRef roleURI="http://www.anaptysbio.com/role/EquityIncentivePlansNarrativeDetails" xlink:href="anab-20180630.xsd#EquityIncentivePlansNarrativeDetails" xlink:type="simple" />
  <link:roleRef roleURI="http://www.anaptysbio.com/role/EquityIncentivePlansOptionActivityDetails" xlink:href="anab-20180630.xsd#EquityIncentivePlansOptionActivityDetails" xlink:type="simple" />
  <link:roleRef roleURI="http://www.anaptysbio.com/role/EquityIncentivePlansOptionFairValueAssumptionsDetails" xlink:href="anab-20180630.xsd#EquityIncentivePlansOptionFairValueAssumptionsDetails" xlink:type="simple" />
  <link:roleRef roleURI="http://www.anaptysbio.com/role/EquityIncentivePlansTables" xlink:href="anab-20180630.xsd#EquityIncentivePlansTables" xlink:type="simple" />
  <link:roleRef roleURI="http://www.anaptysbio.com/role/FairValueMeasurementsAndAvailableForSaleInvestments" xlink:href="anab-20180630.xsd#FairValueMeasurementsAndAvailableForSaleInvestments" xlink:type="simple" />
  <link:roleRef roleURI="http://www.anaptysbio.com/role/FairValueMeasurementsAndAvailableForSaleInvestmentsAssetsAndLiabilitiesMeasuredAtFairValueOnRecurringBasisDetails" xlink:href="anab-20180630.xsd#FairValueMeasurementsAndAvailableForSaleInvestmentsAssetsAndLiabilitiesMeasuredAtFairValueOnRecurringBasisDetails" xlink:type="simple" />
  <link:roleRef roleURI="http://www.anaptysbio.com/role/FairValueMeasurementsAndAvailableForSaleInvestmentsAvailableForSaleInvestmentsDetails" xlink:href="anab-20180630.xsd#FairValueMeasurementsAndAvailableForSaleInvestmentsAvailableForSaleInvestmentsDetails" xlink:type="simple" />
  <link:roleRef roleURI="http://www.anaptysbio.com/role/FairValueMeasurementsAndAvailableForSaleInvestmentsFairValueAssumptionsDetails" xlink:href="anab-20180630.xsd#FairValueMeasurementsAndAvailableForSaleInvestmentsFairValueAssumptionsDetails" xlink:type="simple" />
  <link:roleRef roleURI="http://www.anaptysbio.com/role/FairValueMeasurementsAndAvailableForSaleInvestmentsFairValueOfOtherFinancialInstrumentsDetails" xlink:href="anab-20180630.xsd#FairValueMeasurementsAndAvailableForSaleInvestmentsFairValueOfOtherFinancialInstrumentsDetails" xlink:type="simple" />
  <link:roleRef roleURI="http://www.anaptysbio.com/role/FairValueMeasurementsAndAvailableForSaleInvestmentsLiabilitiesWithSignificantUnobservableInputsDetails" xlink:href="anab-20180630.xsd#FairValueMeasurementsAndAvailableForSaleInvestmentsLiabilitiesWithSignificantUnobservableInputsDetails" xlink:type="simple" />
  <link:roleRef roleURI="http://www.anaptysbio.com/role/FairValueMeasurementsAndAvailableForSaleInvestmentsTables" xlink:href="anab-20180630.xsd#FairValueMeasurementsAndAvailableForSaleInvestmentsTables" xlink:type="simple" />
  <link:roleRef roleURI="http://www.anaptysbio.com/role/NotesPayable" xlink:href="anab-20180630.xsd#NotesPayable" xlink:type="simple" />
  <link:roleRef roleURI="http://www.anaptysbio.com/role/NotesPayableDetails" xlink:href="anab-20180630.xsd#NotesPayableDetails" xlink:type="simple" />
  <link:roleRef roleURI="http://www.anaptysbio.com/role/StockholdersEquity" xlink:href="anab-20180630.xsd#StockholdersEquity" xlink:type="simple" />
  <link:roleRef roleURI="http://www.anaptysbio.com/role/StockholdersEquityAdditionalInformationDetails" xlink:href="anab-20180630.xsd#StockholdersEquityAdditionalInformationDetails" xlink:type="simple" />
  <link:roleRef roleURI="http://www.anaptysbio.com/role/StockholdersEquitySummaryOfCommonStockReservedForFutureIssuanceDetails" xlink:href="anab-20180630.xsd#StockholdersEquitySummaryOfCommonStockReservedForFutureIssuanceDetails" xlink:type="simple" />
  <link:roleRef roleURI="http://www.anaptysbio.com/role/StockholdersEquityTables" xlink:href="anab-20180630.xsd#StockholdersEquityTables" xlink:type="simple" />
  <link:roleRef roleURI="http://www.anaptysbio.com/role/SummaryOfSignificantAccountingPolicies" xlink:href="anab-20180630.xsd#SummaryOfSignificantAccountingPolicies" xlink:type="simple" />
  <link:roleRef roleURI="http://www.anaptysbio.com/role/SummaryOfSignificantAccountingPoliciesAdditionalInformationDetails" xlink:href="anab-20180630.xsd#SummaryOfSignificantAccountingPoliciesAdditionalInformationDetails" xlink:type="simple" />
  <link:roleRef roleURI="http://www.anaptysbio.com/role/SummaryOfSignificantAccountingPoliciesPolicies" xlink:href="anab-20180630.xsd#SummaryOfSignificantAccountingPoliciesPolicies" xlink:type="simple" />
  <link:roleRef roleURI="http://www.anaptysbio.com/role/SummaryOfSignificantAccountingPoliciesSummaryOfPotentiallyDilutiveSecuritiesDetails" xlink:href="anab-20180630.xsd#SummaryOfSignificantAccountingPoliciesSummaryOfPotentiallyDilutiveSecuritiesDetails" xlink:type="simple" />
  <link:roleRef roleURI="http://www.anaptysbio.com/role/SummaryOfSignificantAccountingPoliciesTables" xlink:href="anab-20180630.xsd#SummaryOfSignificantAccountingPoliciesTables" xlink:type="simple" />
  <link:arcroleRef arcroleURI="http://xbrl.org/int/dim/arcrole/all" xlink:href="http://www.xbrl.org/2005/xbrldt-2005.xsd#all" xlink:type="simple" />
  <link:arcroleRef arcroleURI="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:href="http://www.xbrl.org/2005/xbrldt-2005.xsd#dimension-default" xlink:type="simple" />
  <link:arcroleRef arcroleURI="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:href="http://www.xbrl.org/2005/xbrldt-2005.xsd#dimension-domain" xlink:type="simple" />
  <link:arcroleRef arcroleURI="http://xbrl.org/int/dim/arcrole/domain-member" xlink:href="http://www.xbrl.org/2005/xbrldt-2005.xsd#domain-member" xlink:type="simple" />
  <link:arcroleRef arcroleURI="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:href="http://www.xbrl.org/2005/xbrldt-2005.xsd#hypercube-dimension" xlink:type="simple" />
  <link:definitionLink xlink:role="http://www.anaptysbio.com/role/AustraliaResearchAndDevelopmentTaxIncentive" xlink:type="extended" />
  <link:definitionLink xlink:role="http://www.anaptysbio.com/role/AustraliaResearchAndDevelopmentTaxIncentiveDetails" xlink:type="extended">
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_TaxCreditCarryforwardLineItems" xlink:label="loc_us-gaap_TaxCreditCarryforwardLineItems_BF84125934FF4DB40C22480642D386BC" xlink:type="locator" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_TaxCreditCarryforwardTable" xlink:label="loc_us-gaap_TaxCreditCarryforwardTable_1560FDF38EF75A091C32480642D1D9E8" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_TaxCreditCarryforwardLineItems_BF84125934FF4DB40C22480642D386BC" xlink:to="loc_us-gaap_TaxCreditCarryforwardTable_1560FDF38EF75A091C32480642D1D9E8" xlink:type="arc" xbrldt:closed="true" xbrldt:contextElement="segment" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_IncomeTaxAuthorityNameAxis" xlink:label="loc_us-gaap_IncomeTaxAuthorityNameAxis_ECFFFC356B68DC43FC18480642D22278" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_TaxCreditCarryforwardTable_1560FDF38EF75A091C32480642D1D9E8" xlink:to="loc_us-gaap_IncomeTaxAuthorityNameAxis_ECFFFC356B68DC43FC18480642D22278" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_IncomeTaxAuthorityNameDomain" xlink:label="loc_us-gaap_IncomeTaxAuthorityNameDomain_C16328416C2C39A794BD480642D2F1FE_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_IncomeTaxAuthorityNameAxis_ECFFFC356B68DC43FC18480642D22278" xlink:to="loc_us-gaap_IncomeTaxAuthorityNameDomain_C16328416C2C39A794BD480642D2F1FE_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_IncomeTaxAuthorityNameDomain" xlink:label="loc_us-gaap_IncomeTaxAuthorityNameDomain_C16328416C2C39A794BD480642D2F1FE" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_IncomeTaxAuthorityNameAxis_ECFFFC356B68DC43FC18480642D22278" xlink:to="loc_us-gaap_IncomeTaxAuthorityNameDomain_C16328416C2C39A794BD480642D2F1FE" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_AustralianTaxationOfficeMember" xlink:label="loc_us-gaap_AustralianTaxationOfficeMember_39AEDEBFCC79ABDFECB4480642D2A2A6" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncomeTaxAuthorityNameDomain_C16328416C2C39A794BD480642D2F1FE" xlink:to="loc_us-gaap_AustralianTaxationOfficeMember_39AEDEBFCC79ABDFECB4480642D2A2A6" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/srt/2018/elts/srt-2018-01-31.xsd#srt_ConsolidatedEntitiesAxis" xlink:label="loc_srt_ConsolidatedEntitiesAxis_D7C60984D485AD59DC33480642D26FF5" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_TaxCreditCarryforwardTable_1560FDF38EF75A091C32480642D1D9E8" xlink:to="loc_srt_ConsolidatedEntitiesAxis_D7C60984D485AD59DC33480642D26FF5" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/srt/2018/elts/srt-2018-01-31.xsd#srt_ConsolidatedEntitiesDomain" xlink:label="loc_srt_ConsolidatedEntitiesDomain_1E8C67133A8BA2BA4A9F480642D339C1_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_ConsolidatedEntitiesAxis_D7C60984D485AD59DC33480642D26FF5" xlink:to="loc_srt_ConsolidatedEntitiesDomain_1E8C67133A8BA2BA4A9F480642D339C1_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/srt/2018/elts/srt-2018-01-31.xsd#srt_ConsolidatedEntitiesDomain" xlink:label="loc_srt_ConsolidatedEntitiesDomain_1E8C67133A8BA2BA4A9F480642D339C1" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_ConsolidatedEntitiesAxis_D7C60984D485AD59DC33480642D26FF5" xlink:to="loc_srt_ConsolidatedEntitiesDomain_1E8C67133A8BA2BA4A9F480642D339C1" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/srt/2018/elts/srt-2018-01-31.xsd#srt_SubsidiariesMember" xlink:label="loc_srt_SubsidiariesMember_20B8C755D0A73019C5D5480642D3C7A0" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ConsolidatedEntitiesDomain_1E8C67133A8BA2BA4A9F480642D339C1" xlink:to="loc_srt_SubsidiariesMember_20B8C755D0A73019C5D5480642D3C7A0" xlink:type="arc" />
    <link:loc xlink:href="anab-20180630.xsd#anab_ResearchAndDevelopmentTaxIncentiveCreditPercentage" xlink:label="loc_anab_ResearchAndDevelopmentTaxIncentiveCreditPercentage_D04991DBF8E4CF07FFA7480642D479BD" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TaxCreditCarryforwardLineItems_BF84125934FF4DB40C22480642D386BC" xlink:to="loc_anab_ResearchAndDevelopmentTaxIncentiveCreditPercentage_D04991DBF8E4CF07FFA7480642D479BD" xlink:type="arc" />
    <link:loc xlink:href="anab-20180630.xsd#anab_ResearchAndDevelopmentTaxIncentiveCredit" xlink:label="loc_anab_ResearchAndDevelopmentTaxIncentiveCredit_F9F4EA7E4D9A6164F0FF480642D4F6A8" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TaxCreditCarryforwardLineItems_BF84125934FF4DB40C22480642D386BC" xlink:to="loc_anab_ResearchAndDevelopmentTaxIncentiveCredit_F9F4EA7E4D9A6164F0FF480642D4F6A8" xlink:type="arc" />
    <link:loc xlink:href="anab-20180630.xsd#anab_ResearchAndDevelopmentTaxIncentiveCreditReceivableCurrent" xlink:label="loc_anab_ResearchAndDevelopmentTaxIncentiveCreditReceivableCurrent_759B6001397859BD20C7480642D4E706" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TaxCreditCarryforwardLineItems_BF84125934FF4DB40C22480642D386BC" xlink:to="loc_anab_ResearchAndDevelopmentTaxIncentiveCreditReceivableCurrent_759B6001397859BD20C7480642D4E706" xlink:type="arc" />
    <link:loc xlink:href="anab-20180630.xsd#anab_ResearchAndDevelopmentTaxIncentiveCreditReceivedDuringPeriod" xlink:label="loc_anab_ResearchAndDevelopmentTaxIncentiveCreditReceivedDuringPeriod_0015AE37B3B5E2471082480642D4BAE3" xlink:type="locator" />
    <link:definitionArc order="4" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TaxCreditCarryforwardLineItems_BF84125934FF4DB40C22480642D386BC" xlink:to="loc_anab_ResearchAndDevelopmentTaxIncentiveCreditReceivedDuringPeriod_0015AE37B3B5E2471082480642D4BAE3" xlink:type="arc" />
  </link:definitionLink>
  <link:definitionLink xlink:role="http://www.anaptysbio.com/role/BalanceSheetAccountsAndSupplementalDisclosures" xlink:type="extended" />
  <link:definitionLink xlink:role="http://www.anaptysbio.com/role/BalanceSheetAccountsAndSupplementalDisclosuresAccruedExpensesDetails" xlink:type="extended" />
  <link:definitionLink xlink:role="http://www.anaptysbio.com/role/BalanceSheetAccountsAndSupplementalDisclosuresPropertyAndEquipmentDetails" xlink:type="extended">
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_PropertyPlantAndEquipmentLineItems" xlink:label="loc_us-gaap_PropertyPlantAndEquipmentLineItems_96074E3D526259FA1231480643454DE5" xlink:type="locator" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_ScheduleOfPropertyPlantAndEquipmentTable" xlink:label="loc_us-gaap_ScheduleOfPropertyPlantAndEquipmentTable_9D7EAE0C299AE58BF74A4806434234FD" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentLineItems_96074E3D526259FA1231480643454DE5" xlink:to="loc_us-gaap_ScheduleOfPropertyPlantAndEquipmentTable_9D7EAE0C299AE58BF74A4806434234FD" xlink:type="arc" xbrldt:closed="true" xbrldt:contextElement="segment" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_PropertyPlantAndEquipmentByTypeAxis" xlink:label="loc_us-gaap_PropertyPlantAndEquipmentByTypeAxis_3F32189C2420E3D5517C48064343FC1D" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfPropertyPlantAndEquipmentTable_9D7EAE0C299AE58BF74A4806434234FD" xlink:to="loc_us-gaap_PropertyPlantAndEquipmentByTypeAxis_3F32189C2420E3D5517C48064343FC1D" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_PropertyPlantAndEquipmentTypeDomain" xlink:label="loc_us-gaap_PropertyPlantAndEquipmentTypeDomain_824573395105750627AE480643438654_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentByTypeAxis_3F32189C2420E3D5517C48064343FC1D" xlink:to="loc_us-gaap_PropertyPlantAndEquipmentTypeDomain_824573395105750627AE480643438654_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_PropertyPlantAndEquipmentTypeDomain" xlink:label="loc_us-gaap_PropertyPlantAndEquipmentTypeDomain_824573395105750627AE480643438654" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentByTypeAxis_3F32189C2420E3D5517C48064343FC1D" xlink:to="loc_us-gaap_PropertyPlantAndEquipmentTypeDomain_824573395105750627AE480643438654" xlink:type="arc" />
    <link:loc xlink:href="anab-20180630.xsd#anab_LaboratoryEquipmentMember" xlink:label="loc_anab_LaboratoryEquipmentMember_8176B695A8CE55DCD1E248064343A419" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentTypeDomain_824573395105750627AE480643438654" xlink:to="loc_anab_LaboratoryEquipmentMember_8176B695A8CE55DCD1E248064343A419" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_OfficeEquipmentMember" xlink:label="loc_us-gaap_OfficeEquipmentMember_99576BB4166FB4A1653C4806434435F0" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentTypeDomain_824573395105750627AE480643438654" xlink:to="loc_us-gaap_OfficeEquipmentMember_99576BB4166FB4A1653C4806434435F0" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_LeaseholdImprovementsMember" xlink:label="loc_us-gaap_LeaseholdImprovementsMember_E1F9705EE6D1FFA93E9C480643443EB7" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentTypeDomain_824573395105750627AE480643438654" xlink:to="loc_us-gaap_LeaseholdImprovementsMember_E1F9705EE6D1FFA93E9C480643443EB7" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_PropertyPlantAndEquipmentGross" xlink:label="loc_us-gaap_PropertyPlantAndEquipmentGross_CA9EA94032925C9C178448064345F2CB" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentLineItems_96074E3D526259FA1231480643454DE5" xlink:to="loc_us-gaap_PropertyPlantAndEquipmentGross_CA9EA94032925C9C178448064345F2CB" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_AccumulatedDepreciationDepletionAndAmortizationPropertyPlantAndEquipment" xlink:label="loc_us-gaap_AccumulatedDepreciationDepletionAndAmortizationPropertyPlantAndEquipment_E5C22914E36F79DED98048064345A1E4" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentLineItems_96074E3D526259FA1231480643454DE5" xlink:to="loc_us-gaap_AccumulatedDepreciationDepletionAndAmortizationPropertyPlantAndEquipment_E5C22914E36F79DED98048064345A1E4" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_PropertyPlantAndEquipmentNet" xlink:label="loc_us-gaap_PropertyPlantAndEquipmentNet_074728ECF72EE3E99CEA480643454868" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentLineItems_96074E3D526259FA1231480643454DE5" xlink:to="loc_us-gaap_PropertyPlantAndEquipmentNet_074728ECF72EE3E99CEA480643454868" xlink:type="arc" />
  </link:definitionLink>
  <link:definitionLink xlink:role="http://www.anaptysbio.com/role/BalanceSheetAccountsAndSupplementalDisclosuresTables" xlink:type="extended" />
  <link:definitionLink xlink:role="http://www.anaptysbio.com/role/CollaborativeResearchAndDevelopmentAgreements" xlink:type="extended" />
  <link:definitionLink xlink:role="http://www.anaptysbio.com/role/CollaborativeResearchAndDevelopmentAgreementsDetails" xlink:type="extended">
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_DeferredRevenueArrangementLineItems" xlink:label="loc_us-gaap_DeferredRevenueArrangementLineItems_BE33A275C4830B3AA4F2CCD605AE79B6" xlink:type="locator" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_DeferredRevenueArrangementByTypeTable" xlink:label="loc_us-gaap_DeferredRevenueArrangementByTypeTable_CE18FEAD95FD89DC575ACCD605A8B22B" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_DeferredRevenueArrangementLineItems_BE33A275C4830B3AA4F2CCD605AE79B6" xlink:to="loc_us-gaap_DeferredRevenueArrangementByTypeTable_CE18FEAD95FD89DC575ACCD605A8B22B" xlink:type="arc" xbrldt:closed="true" xbrldt:contextElement="segment" />
    <link:loc xlink:href="http://xbrl.fasb.org/srt/2018/elts/srt-2018-01-31.xsd#srt_CounterpartyNameAxis" xlink:label="loc_srt_CounterpartyNameAxis_3491760ADDC8FAC46940CCD605A9BB09" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DeferredRevenueArrangementByTypeTable_CE18FEAD95FD89DC575ACCD605A8B22B" xlink:to="loc_srt_CounterpartyNameAxis_3491760ADDC8FAC46940CCD605A9BB09" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/srt/2018/elts/srt-2018-01-31.xsd#srt_RepurchaseAgreementCounterpartyNameDomain" xlink:label="loc_srt_RepurchaseAgreementCounterpartyNameDomain_7E1F66AE79C246DE7C43CCD605AAF396_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_CounterpartyNameAxis_3491760ADDC8FAC46940CCD605A9BB09" xlink:to="loc_srt_RepurchaseAgreementCounterpartyNameDomain_7E1F66AE79C246DE7C43CCD605AAF396_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/srt/2018/elts/srt-2018-01-31.xsd#srt_RepurchaseAgreementCounterpartyNameDomain" xlink:label="loc_srt_RepurchaseAgreementCounterpartyNameDomain_7E1F66AE79C246DE7C43CCD605AAF396" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_CounterpartyNameAxis_3491760ADDC8FAC46940CCD605A9BB09" xlink:to="loc_srt_RepurchaseAgreementCounterpartyNameDomain_7E1F66AE79C246DE7C43CCD605AAF396" xlink:type="arc" />
    <link:loc xlink:href="anab-20180630.xsd#anab_TESAROInc.AndTESARODevelopmentInc.Member" xlink:label="loc_anab_TESAROInc.AndTESARODevelopmentInc.Member_ECD87C15FC77FD00773BCCD605AA115B" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_RepurchaseAgreementCounterpartyNameDomain_7E1F66AE79C246DE7C43CCD605AAF396" xlink:to="loc_anab_TESAROInc.AndTESARODevelopmentInc.Member_ECD87C15FC77FD00773BCCD605AA115B" xlink:type="arc" />
    <link:loc xlink:href="anab-20180630.xsd#anab_CelgeneCorporationMember" xlink:label="loc_anab_CelgeneCorporationMember_D184A08F70084343C5F3CCD605AB865F" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_RepurchaseAgreementCounterpartyNameDomain_7E1F66AE79C246DE7C43CCD605AAF396" xlink:to="loc_anab_CelgeneCorporationMember_D184A08F70084343C5F3CCD605AB865F" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_TypeOfArrangementAxis" xlink:label="loc_us-gaap_TypeOfArrangementAxis_AB5CE3267E59C183D476CCD605ABEB40" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DeferredRevenueArrangementByTypeTable_CE18FEAD95FD89DC575ACCD605A8B22B" xlink:to="loc_us-gaap_TypeOfArrangementAxis_AB5CE3267E59C183D476CCD605ABEB40" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_ArrangementsAndNonarrangementTransactionsMember" xlink:label="loc_us-gaap_ArrangementsAndNonarrangementTransactionsMember_0A821B01FF57D68A9765CCD605AC94C5_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_TypeOfArrangementAxis_AB5CE3267E59C183D476CCD605ABEB40" xlink:to="loc_us-gaap_ArrangementsAndNonarrangementTransactionsMember_0A821B01FF57D68A9765CCD605AC94C5_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_ArrangementsAndNonarrangementTransactionsMember" xlink:label="loc_us-gaap_ArrangementsAndNonarrangementTransactionsMember_0A821B01FF57D68A9765CCD605AC94C5" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_TypeOfArrangementAxis_AB5CE3267E59C183D476CCD605ABEB40" xlink:to="loc_us-gaap_ArrangementsAndNonarrangementTransactionsMember_0A821B01FF57D68A9765CCD605AC94C5" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_CollaborativeArrangementMember" xlink:label="loc_us-gaap_CollaborativeArrangementMember_F4DA07F5A5B5698E3865CCD605AC89AD" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ArrangementsAndNonarrangementTransactionsMember_0A821B01FF57D68A9765CCD605AC94C5" xlink:to="loc_us-gaap_CollaborativeArrangementMember_F4DA07F5A5B5698E3865CCD605AC89AD" xlink:type="arc" />
    <link:loc xlink:href="anab-20180630.xsd#anab_InVivoToxicologyStudiesMember" xlink:label="loc_anab_InVivoToxicologyStudiesMember_607EA1D60FEA7E0E176ECCD605AC0EA1" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CollaborativeArrangementMember_F4DA07F5A5B5698E3865CCD605AC89AD" xlink:to="loc_anab_InVivoToxicologyStudiesMember_607EA1D60FEA7E0E176ECCD605AC0EA1" xlink:type="arc" />
    <link:loc xlink:href="anab-20180630.xsd#anab_ClearanceOfInvestigationalNewDrugFromFDAMember" xlink:label="loc_anab_ClearanceOfInvestigationalNewDrugFromFDAMember_C0116A735B96474C0491CCD605AD47B5" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CollaborativeArrangementMember_F4DA07F5A5B5698E3865CCD605AC89AD" xlink:to="loc_anab_ClearanceOfInvestigationalNewDrugFromFDAMember_C0116A735B96474C0491CCD605AD47B5" xlink:type="arc" />
    <link:loc xlink:href="anab-20180630.xsd#anab_Phase2ClinicalTrialInitiationMember" xlink:label="loc_anab_Phase2ClinicalTrialInitiationMember_C7A03D1CC532A2F28B78CCD605AD0672" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CollaborativeArrangementMember_F4DA07F5A5B5698E3865CCD605AC89AD" xlink:to="loc_anab_Phase2ClinicalTrialInitiationMember_C7A03D1CC532A2F28B78CCD605AD0672" xlink:type="arc" />
    <link:loc xlink:href="anab-20180630.xsd#anab_Phase1ClinicalTrialInitiationMember" xlink:label="loc_anab_Phase1ClinicalTrialInitiationMember_13485539B08E3B113524CCD605AD8D17" xlink:type="locator" />
    <link:definitionArc order="4" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CollaborativeArrangementMember_F4DA07F5A5B5698E3865CCD605AC89AD" xlink:to="loc_anab_Phase1ClinicalTrialInitiationMember_13485539B08E3B113524CCD605AD8D17" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/srt/2018/elts/srt-2018-01-31.xsd#srt_ProductOrServiceAxis" xlink:label="loc_srt_ProductOrServiceAxis_2AA05C8165B8495BAEBECCD605ADEE31" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DeferredRevenueArrangementByTypeTable_CE18FEAD95FD89DC575ACCD605A8B22B" xlink:to="loc_srt_ProductOrServiceAxis_2AA05C8165B8495BAEBECCD605ADEE31" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/srt/2018/elts/srt-2018-01-31.xsd#srt_ProductsAndServicesDomain" xlink:label="loc_srt_ProductsAndServicesDomain_9429D4FB6D8116A860EBCCD605AD3120_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_ProductOrServiceAxis_2AA05C8165B8495BAEBECCD605ADEE31" xlink:to="loc_srt_ProductsAndServicesDomain_9429D4FB6D8116A860EBCCD605AD3120_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/srt/2018/elts/srt-2018-01-31.xsd#srt_ProductsAndServicesDomain" xlink:label="loc_srt_ProductsAndServicesDomain_9429D4FB6D8116A860EBCCD605AD3120" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_ProductOrServiceAxis_2AA05C8165B8495BAEBECCD605ADEE31" xlink:to="loc_srt_ProductsAndServicesDomain_9429D4FB6D8116A860EBCCD605AD3120" xlink:type="arc" />
    <link:loc xlink:href="anab-20180630.xsd#anab_AnaptysBiogeneratedAntiPD1AntagonistAntibodyTSR042Member" xlink:label="loc_anab_AnaptysBiogeneratedAntiPD1AntagonistAntibodyTSR042Member_9FCC6EC557812E820E32CCD605ADD855" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ProductsAndServicesDomain_9429D4FB6D8116A860EBCCD605AD3120" xlink:to="loc_anab_AnaptysBiogeneratedAntiPD1AntagonistAntibodyTSR042Member_9FCC6EC557812E820E32CCD605ADD855" xlink:type="arc" />
    <link:loc xlink:href="anab-20180630.xsd#anab_AnaptysBioGeneratedAntiTIM3AntagonistAntibodyTSR022Member" xlink:label="loc_anab_AnaptysBioGeneratedAntiTIM3AntagonistAntibodyTSR022Member_98062CB6ACC1FC8794A9CCD605AEE94D" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ProductsAndServicesDomain_9429D4FB6D8116A860EBCCD605AD3120" xlink:to="loc_anab_AnaptysBioGeneratedAntiTIM3AntagonistAntibodyTSR022Member_98062CB6ACC1FC8794A9CCD605AEE94D" xlink:type="arc" />
    <link:loc xlink:href="anab-20180630.xsd#anab_AnaptysBioGeneratedAntiLAG3AntagonistAntibodyTSR033Member" xlink:label="loc_anab_AnaptysBioGeneratedAntiLAG3AntagonistAntibodyTSR033Member_93854E990E622348026FCCD605AE0F50" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ProductsAndServicesDomain_9429D4FB6D8116A860EBCCD605AD3120" xlink:to="loc_anab_AnaptysBioGeneratedAntiLAG3AntagonistAntibodyTSR033Member_93854E990E622348026FCCD605AE0F50" xlink:type="arc" />
    <link:loc xlink:href="anab-20180630.xsd#anab_AnaptysBioGeneratedAntiPD1AntagonistAntibodyCC90006Member" xlink:label="loc_anab_AnaptysBioGeneratedAntiPD1AntagonistAntibodyCC90006Member_66674721A9C2967FE8F9CCD605AE7711" xlink:type="locator" />
    <link:definitionArc order="4" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ProductsAndServicesDomain_9429D4FB6D8116A860EBCCD605AD3120" xlink:to="loc_anab_AnaptysBioGeneratedAntiPD1AntagonistAntibodyCC90006Member_66674721A9C2967FE8F9CCD605AE7711" xlink:type="arc" />
    <link:loc xlink:href="anab-20180630.xsd#anab_RevenueRecognitionMultipledeliverableArrangementsUpfrontFeeReceived" xlink:label="loc_anab_RevenueRecognitionMultipledeliverableArrangementsUpfrontFeeReceived_A6C5FC17BB91A48CA2ECCCD605AE507B" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DeferredRevenueArrangementLineItems_BE33A275C4830B3AA4F2CCD605AE79B6" xlink:to="loc_anab_RevenueRecognitionMultipledeliverableArrangementsUpfrontFeeReceived_A6C5FC17BB91A48CA2ECCCD605AE507B" xlink:type="arc" />
    <link:loc xlink:href="anab-20180630.xsd#anab_RevenueRecognitionMilestoneMethodNumberOfOutstandingResearchAndDevelopmentTargets" xlink:label="loc_anab_RevenueRecognitionMilestoneMethodNumberOfOutstandingResearchAndDevelopmentTargets_0AD61309530FE4DDFE55CCD605AF12EC" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DeferredRevenueArrangementLineItems_BE33A275C4830B3AA4F2CCD605AE79B6" xlink:to="loc_anab_RevenueRecognitionMilestoneMethodNumberOfOutstandingResearchAndDevelopmentTargets_0AD61309530FE4DDFE55CCD605AF12EC" xlink:type="arc" />
    <link:loc xlink:href="anab-20180630.xsd#anab_RevenueRecognitionMilestoneMethodContingentUponPreclinicalAndClinicalTrialEvents" xlink:label="loc_anab_RevenueRecognitionMilestoneMethodContingentUponPreclinicalAndClinicalTrialEvents_EDFE1D66C72562BACB34CCD605AFCDA4" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DeferredRevenueArrangementLineItems_BE33A275C4830B3AA4F2CCD605AE79B6" xlink:to="loc_anab_RevenueRecognitionMilestoneMethodContingentUponPreclinicalAndClinicalTrialEvents_EDFE1D66C72562BACB34CCD605AFCDA4" xlink:type="arc" />
    <link:loc xlink:href="anab-20180630.xsd#anab_RevenueRecognitionMilestoneMethodContingentUponCertainUnitedStatesAndEuropeanRegulatorySubmissionsAndApprovals" xlink:label="loc_anab_RevenueRecognitionMilestoneMethodContingentUponCertainUnitedStatesAndEuropeanRegulatorySubmissionsAndApprovals_88BAF93F9B95C65DA5DBCCD605AF321D" xlink:type="locator" />
    <link:definitionArc order="4" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DeferredRevenueArrangementLineItems_BE33A275C4830B3AA4F2CCD605AE79B6" xlink:to="loc_anab_RevenueRecognitionMilestoneMethodContingentUponCertainUnitedStatesAndEuropeanRegulatorySubmissionsAndApprovals_88BAF93F9B95C65DA5DBCCD605AF321D" xlink:type="arc" />
    <link:loc xlink:href="anab-20180630.xsd#anab_RevenueRecognitionMilestoneMethodContingentUponAchievementOfSpecifiedLevelsOfWorldwideSales" xlink:label="loc_anab_RevenueRecognitionMilestoneMethodContingentUponAchievementOfSpecifiedLevelsOfWorldwideSales_307EEEA63739FB7F2BF1CCD605AF730A" xlink:type="locator" />
    <link:definitionArc order="5" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DeferredRevenueArrangementLineItems_BE33A275C4830B3AA4F2CCD605AE79B6" xlink:to="loc_anab_RevenueRecognitionMilestoneMethodContingentUponAchievementOfSpecifiedLevelsOfWorldwideSales_307EEEA63739FB7F2BF1CCD605AF730A" xlink:type="arc" />
    <link:loc xlink:href="anab-20180630.xsd#anab_RevenueRecognitionMilestoneMethodAgreementTermFollowingFirstCommercialSaleOrExpirationOfTheLastToExpirePatent" xlink:label="loc_anab_RevenueRecognitionMilestoneMethodAgreementTermFollowingFirstCommercialSaleOrExpirationOfTheLastToExpirePatent_D0E3DDEFFCA764F1FC24CCD605AF7402" xlink:type="locator" />
    <link:definitionArc order="6" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DeferredRevenueArrangementLineItems_BE33A275C4830B3AA4F2CCD605AE79B6" xlink:to="loc_anab_RevenueRecognitionMilestoneMethodAgreementTermFollowingFirstCommercialSaleOrExpirationOfTheLastToExpirePatent_D0E3DDEFFCA764F1FC24CCD605AF7402" xlink:type="arc" />
    <link:loc xlink:href="anab-20180630.xsd#anab_RevenueRecognitionMilestoneMethodMilestonesAchievedDuringThePeriodAmount" xlink:label="loc_anab_RevenueRecognitionMilestoneMethodMilestonesAchievedDuringThePeriodAmount_67CA546E3CFDB55A0048CCD605B0F1B2" xlink:type="locator" />
    <link:definitionArc order="7" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DeferredRevenueArrangementLineItems_BE33A275C4830B3AA4F2CCD605AE79B6" xlink:to="loc_anab_RevenueRecognitionMilestoneMethodMilestonesAchievedDuringThePeriodAmount_67CA546E3CFDB55A0048CCD605B0F1B2" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_RevenueFromContractWithCustomerIncludingAssessedTax" xlink:label="loc_us-gaap_RevenueFromContractWithCustomerIncludingAssessedTax_0BC7457699C57A400C1CCCD605B0FA92" xlink:type="locator" />
    <link:definitionArc order="8" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DeferredRevenueArrangementLineItems_BE33A275C4830B3AA4F2CCD605AE79B6" xlink:to="loc_us-gaap_RevenueFromContractWithCustomerIncludingAssessedTax_0BC7457699C57A400C1CCCD605B0FA92" xlink:type="arc" />
    <link:loc xlink:href="anab-20180630.xsd#anab_RevenueRecognitionMilestoneMethodMaximumRevenuePerMilestone" xlink:label="loc_anab_RevenueRecognitionMilestoneMethodMaximumRevenuePerMilestone_3F5DAB8CAC070EA3ECB2CCD605B0A448" xlink:type="locator" />
    <link:definitionArc order="9" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DeferredRevenueArrangementLineItems_BE33A275C4830B3AA4F2CCD605AE79B6" xlink:to="loc_anab_RevenueRecognitionMilestoneMethodMaximumRevenuePerMilestone_3F5DAB8CAC070EA3ECB2CCD605B0A448" xlink:type="arc" />
    <link:loc xlink:href="anab-20180630.xsd#anab_RevenueRecognizedMilestoneMethodMilestonePaymentEarned" xlink:label="loc_anab_RevenueRecognizedMilestoneMethodMilestonePaymentEarned_1B2043F780C5B9E4018BCCD605B09EE5" xlink:type="locator" />
    <link:definitionArc order="10" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DeferredRevenueArrangementLineItems_BE33A275C4830B3AA4F2CCD605AE79B6" xlink:to="loc_anab_RevenueRecognizedMilestoneMethodMilestonePaymentEarned_1B2043F780C5B9E4018BCCD605B09EE5" xlink:type="arc" />
  </link:definitionLink>
  <link:definitionLink xlink:role="http://www.anaptysbio.com/role/CollaborativeResearchAndDevelopmentAgreementsTables" xlink:type="extended" />
  <link:definitionLink xlink:role="http://www.anaptysbio.com/role/CommitmentsAndContingencies" xlink:type="extended" />
  <link:definitionLink xlink:role="http://www.anaptysbio.com/role/CommitmentsAndContingenciesDetails" xlink:type="extended">
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_OperatingLeasedAssetsLineItems" xlink:label="loc_us-gaap_OperatingLeasedAssetsLineItems_8C6285863743F04D44ACFBACE22A71EC" xlink:type="locator" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_ScheduleOfOperatingLeasedAssetsTable" xlink:label="loc_us-gaap_ScheduleOfOperatingLeasedAssetsTable_F6DE3B7D4158669DAD07FBACE22A4338" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_OperatingLeasedAssetsLineItems_8C6285863743F04D44ACFBACE22A71EC" xlink:to="loc_us-gaap_ScheduleOfOperatingLeasedAssetsTable_F6DE3B7D4158669DAD07FBACE22A4338" xlink:type="arc" xbrldt:closed="true" xbrldt:contextElement="segment" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_LeaseArrangementTypeAxis" xlink:label="loc_us-gaap_LeaseArrangementTypeAxis_83966C4DA5C2C6E4F9E3FBACE22AE05A" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfOperatingLeasedAssetsTable_F6DE3B7D4158669DAD07FBACE22A4338" xlink:to="loc_us-gaap_LeaseArrangementTypeAxis_83966C4DA5C2C6E4F9E3FBACE22AE05A" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_LeaseArrangementTypeDomain" xlink:label="loc_us-gaap_LeaseArrangementTypeDomain_2E1D0ACE4029908F0398FBACE22A51EE_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_LeaseArrangementTypeAxis_83966C4DA5C2C6E4F9E3FBACE22AE05A" xlink:to="loc_us-gaap_LeaseArrangementTypeDomain_2E1D0ACE4029908F0398FBACE22A51EE_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_LeaseArrangementTypeDomain" xlink:label="loc_us-gaap_LeaseArrangementTypeDomain_2E1D0ACE4029908F0398FBACE22A51EE" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_LeaseArrangementTypeAxis_83966C4DA5C2C6E4F9E3FBACE22AE05A" xlink:to="loc_us-gaap_LeaseArrangementTypeDomain_2E1D0ACE4029908F0398FBACE22A51EE" xlink:type="arc" />
    <link:loc xlink:href="anab-20180630.xsd#anab_NewSubleaseAgreementMember" xlink:label="loc_anab_NewSubleaseAgreementMember_CFC380DDAE0349BA277FFBACE22AA3A7" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LeaseArrangementTypeDomain_2E1D0ACE4029908F0398FBACE22A51EE" xlink:to="loc_anab_NewSubleaseAgreementMember_CFC380DDAE0349BA277FFBACE22AA3A7" xlink:type="arc" />
    <link:loc xlink:href="anab-20180630.xsd#anab_OriginalLeaseAgreementMember" xlink:label="loc_anab_OriginalLeaseAgreementMember_85D0CCCF2F1A26B5EDCFFBACE4A41391" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LeaseArrangementTypeDomain_2E1D0ACE4029908F0398FBACE22A51EE" xlink:to="loc_anab_OriginalLeaseAgreementMember_85D0CCCF2F1A26B5EDCFFBACE4A41391" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_LesseeOperatingLeaseTermOfContract" xlink:label="loc_us-gaap_LesseeOperatingLeaseTermOfContract_99E3865BB9464FC6C980FBACE22A2041" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_OperatingLeasedAssetsLineItems_8C6285863743F04D44ACFBACE22A71EC" xlink:to="loc_us-gaap_LesseeOperatingLeaseTermOfContract_99E3865BB9464FC6C980FBACE22A2041" xlink:type="arc" />
    <link:loc xlink:href="anab-20180630.xsd#anab_LesseeOperatingLeaseRentedSquareFeet" xlink:label="loc_anab_LesseeOperatingLeaseRentedSquareFeet_E10ABD581A062E5203E8FBACE22AF3CA" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_OperatingLeasedAssetsLineItems_8C6285863743F04D44ACFBACE22A71EC" xlink:to="loc_anab_LesseeOperatingLeaseRentedSquareFeet_E10ABD581A062E5203E8FBACE22AF3CA" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_LesseeOperatingLeaseRenewalTerm" xlink:label="loc_us-gaap_LesseeOperatingLeaseRenewalTerm_0931F5E475C32825DB6FFBACE23972CD" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_OperatingLeasedAssetsLineItems_8C6285863743F04D44ACFBACE22A71EC" xlink:to="loc_us-gaap_LesseeOperatingLeaseRenewalTerm_0931F5E475C32825DB6FFBACE23972CD" xlink:type="arc" />
  </link:definitionLink>
  <link:definitionLink xlink:role="http://www.anaptysbio.com/role/CommitmentsAndContingenciesTables" xlink:type="extended" />
  <link:definitionLink xlink:role="http://www.anaptysbio.com/role/ConsolidatedBalanceSheets" xlink:type="extended" />
  <link:definitionLink xlink:role="http://www.anaptysbio.com/role/ConsolidatedBalanceSheetsParenthetical" xlink:type="extended" />
  <link:definitionLink xlink:role="http://www.anaptysbio.com/role/ConsolidatedStatementsOfCashFlows" xlink:type="extended" />
  <link:definitionLink xlink:role="http://www.anaptysbio.com/role/ConsolidatedStatementsOfOperationsAndComprehensiveLoss" xlink:type="extended" />
  <link:definitionLink xlink:role="http://www.anaptysbio.com/role/DescriptionOfBusiness" xlink:type="extended" />
  <link:definitionLink xlink:role="http://www.anaptysbio.com/role/DescriptionOfBusinessDetails" xlink:type="extended">
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_ClassOfWarrantOrRightLineItems" xlink:label="loc_us-gaap_ClassOfWarrantOrRightLineItems_D4E1CE8C58A3BF6C1D2E480642A85E48" xlink:type="locator" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_ClassOfWarrantOrRightTable" xlink:label="loc_us-gaap_ClassOfWarrantOrRightTable_87A06E7770DB371AD1F8480642A644D0" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_ClassOfWarrantOrRightLineItems_D4E1CE8C58A3BF6C1D2E480642A85E48" xlink:to="loc_us-gaap_ClassOfWarrantOrRightTable_87A06E7770DB371AD1F8480642A644D0" xlink:type="arc" xbrldt:closed="true" xbrldt:contextElement="segment" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_SubsidiarySaleOfStockAxis" xlink:label="loc_us-gaap_SubsidiarySaleOfStockAxis_7AC32B25209B92E63898480642A614A8" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ClassOfWarrantOrRightTable_87A06E7770DB371AD1F8480642A644D0" xlink:to="loc_us-gaap_SubsidiarySaleOfStockAxis_7AC32B25209B92E63898480642A614A8" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_SaleOfStockNameOfTransactionDomain" xlink:label="loc_us-gaap_SaleOfStockNameOfTransactionDomain_0C603CFE0D03A7C14EF8480642A640BE_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_SubsidiarySaleOfStockAxis_7AC32B25209B92E63898480642A614A8" xlink:to="loc_us-gaap_SaleOfStockNameOfTransactionDomain_0C603CFE0D03A7C14EF8480642A640BE_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_SaleOfStockNameOfTransactionDomain" xlink:label="loc_us-gaap_SaleOfStockNameOfTransactionDomain_0C603CFE0D03A7C14EF8480642A640BE" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_SubsidiarySaleOfStockAxis_7AC32B25209B92E63898480642A614A8" xlink:to="loc_us-gaap_SaleOfStockNameOfTransactionDomain_0C603CFE0D03A7C14EF8480642A640BE" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_IPOMember" xlink:label="loc_us-gaap_IPOMember_EF810FCC02429B04B32F480642A6511B" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SaleOfStockNameOfTransactionDomain_0C603CFE0D03A7C14EF8480642A640BE" xlink:to="loc_us-gaap_IPOMember_EF810FCC02429B04B32F480642A6511B" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_OverAllotmentOptionMember" xlink:label="loc_us-gaap_OverAllotmentOptionMember_5FEF92EDF1CEE802DADF480642A7AC0B" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SaleOfStockNameOfTransactionDomain_0C603CFE0D03A7C14EF8480642A640BE" xlink:to="loc_us-gaap_OverAllotmentOptionMember_5FEF92EDF1CEE802DADF480642A7AC0B" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_StatementEquityComponentsAxis" xlink:label="loc_us-gaap_StatementEquityComponentsAxis_D91900C10CB7C99F5D3A480642A73B62" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ClassOfWarrantOrRightTable_87A06E7770DB371AD1F8480642A644D0" xlink:to="loc_us-gaap_StatementEquityComponentsAxis_D91900C10CB7C99F5D3A480642A73B62" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_EquityComponentDomain" xlink:label="loc_us-gaap_EquityComponentDomain_A310894E5C4AB14ABCFB480642A77DA1_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_StatementEquityComponentsAxis_D91900C10CB7C99F5D3A480642A73B62" xlink:to="loc_us-gaap_EquityComponentDomain_A310894E5C4AB14ABCFB480642A77DA1_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_EquityComponentDomain" xlink:label="loc_us-gaap_EquityComponentDomain_A310894E5C4AB14ABCFB480642A77DA1" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_StatementEquityComponentsAxis_D91900C10CB7C99F5D3A480642A73B62" xlink:to="loc_us-gaap_EquityComponentDomain_A310894E5C4AB14ABCFB480642A77DA1" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_CommonStockMember" xlink:label="loc_us-gaap_CommonStockMember_DB523881C83BCF647412480642A7F006" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityComponentDomain_A310894E5C4AB14ABCFB480642A77DA1" xlink:to="loc_us-gaap_CommonStockMember_DB523881C83BCF647412480642A7F006" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_StatementClassOfStockAxis" xlink:label="loc_us-gaap_StatementClassOfStockAxis_B7DEAF2AD1A603F538F8480642A847EB" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ClassOfWarrantOrRightTable_87A06E7770DB371AD1F8480642A644D0" xlink:to="loc_us-gaap_StatementClassOfStockAxis_B7DEAF2AD1A603F538F8480642A847EB" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_ClassOfStockDomain" xlink:label="loc_us-gaap_ClassOfStockDomain_F4EB1375CAD842A32F53480642A86C5F_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_StatementClassOfStockAxis_B7DEAF2AD1A603F538F8480642A847EB" xlink:to="loc_us-gaap_ClassOfStockDomain_F4EB1375CAD842A32F53480642A86C5F_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_ClassOfStockDomain" xlink:label="loc_us-gaap_ClassOfStockDomain_F4EB1375CAD842A32F53480642A86C5F" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_StatementClassOfStockAxis_B7DEAF2AD1A603F538F8480642A847EB" xlink:to="loc_us-gaap_ClassOfStockDomain_F4EB1375CAD842A32F53480642A86C5F" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_ConvertiblePreferredStockMember" xlink:label="loc_us-gaap_ConvertiblePreferredStockMember_DDA300ECD914D507E750480642A8E24C" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockDomain_F4EB1375CAD842A32F53480642A86C5F" xlink:to="loc_us-gaap_ConvertiblePreferredStockMember_DDA300ECD914D507E750480642A8E24C" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_StockIssuedDuringPeriodSharesNewIssues" xlink:label="loc_us-gaap_StockIssuedDuringPeriodSharesNewIssues_F32504A9A0AC248F952B480642A9022A" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfWarrantOrRightLineItems_D4E1CE8C58A3BF6C1D2E480642A85E48" xlink:to="loc_us-gaap_StockIssuedDuringPeriodSharesNewIssues_F32504A9A0AC248F952B480642A9022A" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_SharesIssuedPricePerShare" xlink:label="loc_us-gaap_SharesIssuedPricePerShare_6AC98283661D87C9C3C9480642A90A4C" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfWarrantOrRightLineItems_D4E1CE8C58A3BF6C1D2E480642A85E48" xlink:to="loc_us-gaap_SharesIssuedPricePerShare_6AC98283661D87C9C3C9480642A90A4C" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_ProceedsFromIssuanceInitialPublicOffering" xlink:label="loc_us-gaap_ProceedsFromIssuanceInitialPublicOffering_6490D9A433872E6B7051480642A9C93B" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfWarrantOrRightLineItems_D4E1CE8C58A3BF6C1D2E480642A85E48" xlink:to="loc_us-gaap_ProceedsFromIssuanceInitialPublicOffering_6490D9A433872E6B7051480642A9C93B" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_StockIssuedDuringPeriodSharesConversionOfConvertibleSecurities" xlink:label="loc_us-gaap_StockIssuedDuringPeriodSharesConversionOfConvertibleSecurities_34663DA340419370DB08480642A9FEE0" xlink:type="locator" />
    <link:definitionArc order="4" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfWarrantOrRightLineItems_D4E1CE8C58A3BF6C1D2E480642A85E48" xlink:to="loc_us-gaap_StockIssuedDuringPeriodSharesConversionOfConvertibleSecurities_34663DA340419370DB08480642A9FEE0" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_ClassOfWarrantOrRightNumberOfSecuritiesCalledByWarrantsOrRights" xlink:label="loc_us-gaap_ClassOfWarrantOrRightNumberOfSecuritiesCalledByWarrantsOrRights_C10428536D6894B2F099480642A947A8" xlink:type="locator" />
    <link:definitionArc order="5" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfWarrantOrRightLineItems_D4E1CE8C58A3BF6C1D2E480642A85E48" xlink:to="loc_us-gaap_ClassOfWarrantOrRightNumberOfSecuritiesCalledByWarrantsOrRights_C10428536D6894B2F099480642A947A8" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_StockholdersEquityNoteStockSplitConversionRatio1" xlink:label="loc_us-gaap_StockholdersEquityNoteStockSplitConversionRatio1_CB6ED3B8BB8C4A773511480642A99F12" xlink:type="locator" />
    <link:definitionArc order="6" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfWarrantOrRightLineItems_D4E1CE8C58A3BF6C1D2E480642A85E48" xlink:to="loc_us-gaap_StockholdersEquityNoteStockSplitConversionRatio1_CB6ED3B8BB8C4A773511480642A99F12" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_ProceedsFromIssuanceOfCommonStock" xlink:label="loc_us-gaap_ProceedsFromIssuanceOfCommonStock_881BE3EC93FCA1FB4187480642AAC6F5" xlink:type="locator" />
    <link:definitionArc order="7" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfWarrantOrRightLineItems_D4E1CE8C58A3BF6C1D2E480642A85E48" xlink:to="loc_us-gaap_ProceedsFromIssuanceOfCommonStock_881BE3EC93FCA1FB4187480642AAC6F5" xlink:type="arc" />
  </link:definitionLink>
  <link:definitionLink xlink:role="http://www.anaptysbio.com/role/DocumentAndEntityInformation" xlink:type="extended" />
  <link:definitionLink xlink:role="http://www.anaptysbio.com/role/EquityIncentivePlans" xlink:type="extended" />
  <link:definitionLink xlink:role="http://www.anaptysbio.com/role/EquityIncentivePlansAllocationOfShareBasedCompensationExpenseDetails" xlink:type="extended">
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_7AC95D0B24FA8A401892480642B1412E" xlink:type="locator" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable" xlink:label="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_EBEE73CD762B943D165F480642B02A28" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_7AC95D0B24FA8A401892480642B1412E" xlink:to="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_EBEE73CD762B943D165F480642B02A28" xlink:type="arc" xbrldt:closed="true" xbrldt:contextElement="segment" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_IncomeStatementLocationAxis" xlink:label="loc_us-gaap_IncomeStatementLocationAxis_22D031CA6636CFF85B07480642B0D73E" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_EBEE73CD762B943D165F480642B02A28" xlink:to="loc_us-gaap_IncomeStatementLocationAxis_22D031CA6636CFF85B07480642B0D73E" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_IncomeStatementLocationDomain" xlink:label="loc_us-gaap_IncomeStatementLocationDomain_CB40751ABA0D4B2CA40C480642B006FC_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_IncomeStatementLocationAxis_22D031CA6636CFF85B07480642B0D73E" xlink:to="loc_us-gaap_IncomeStatementLocationDomain_CB40751ABA0D4B2CA40C480642B006FC_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_IncomeStatementLocationDomain" xlink:label="loc_us-gaap_IncomeStatementLocationDomain_CB40751ABA0D4B2CA40C480642B006FC" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_IncomeStatementLocationAxis_22D031CA6636CFF85B07480642B0D73E" xlink:to="loc_us-gaap_IncomeStatementLocationDomain_CB40751ABA0D4B2CA40C480642B006FC" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_ResearchAndDevelopmentExpenseMember" xlink:label="loc_us-gaap_ResearchAndDevelopmentExpenseMember_472EB4C3F7465271CF54480642B162D2" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncomeStatementLocationDomain_CB40751ABA0D4B2CA40C480642B006FC" xlink:to="loc_us-gaap_ResearchAndDevelopmentExpenseMember_472EB4C3F7465271CF54480642B162D2" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_GeneralAndAdministrativeExpenseMember" xlink:label="loc_us-gaap_GeneralAndAdministrativeExpenseMember_A022E326334886DBD728480642B1B0B7" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncomeStatementLocationDomain_CB40751ABA0D4B2CA40C480642B006FC" xlink:to="loc_us-gaap_GeneralAndAdministrativeExpenseMember_A022E326334886DBD728480642B1B0B7" xlink:type="arc" />
    <link:loc xlink:href="anab-20180630.xsd#anab_SharebasedCompensationAndIssuanceOfStockAndWarrantsForServicesOrClaims" xlink:label="loc_anab_SharebasedCompensationAndIssuanceOfStockAndWarrantsForServicesOrClaims_D5C3F242049F655EFDB2480642B1E92D" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_7AC95D0B24FA8A401892480642B1412E" xlink:to="loc_anab_SharebasedCompensationAndIssuanceOfStockAndWarrantsForServicesOrClaims_D5C3F242049F655EFDB2480642B1E92D" xlink:type="arc" />
  </link:definitionLink>
  <link:definitionLink xlink:role="http://www.anaptysbio.com/role/EquityIncentivePlansNarrativeDetails" xlink:type="extended">
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_BFDBAB68C379B2DE5F7FD8248749B706" xlink:type="locator" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable" xlink:label="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_4E507D327FEFFEBA6DB1D82487454F71" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_BFDBAB68C379B2DE5F7FD8248749B706" xlink:to="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_4E507D327FEFFEBA6DB1D82487454F71" xlink:type="arc" xbrldt:closed="true" xbrldt:contextElement="segment" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_PlanNameAxis" xlink:label="loc_us-gaap_PlanNameAxis_CC8B6CE6B26E02DA03DDD8248745CA53" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_4E507D327FEFFEBA6DB1D82487454F71" xlink:to="loc_us-gaap_PlanNameAxis_CC8B6CE6B26E02DA03DDD8248745CA53" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_PlanNameDomain" xlink:label="loc_us-gaap_PlanNameDomain_CE4BE1E6441263C5A3F2D8248745C8DA_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_PlanNameAxis_CC8B6CE6B26E02DA03DDD8248745CA53" xlink:to="loc_us-gaap_PlanNameDomain_CE4BE1E6441263C5A3F2D8248745C8DA_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_PlanNameDomain" xlink:label="loc_us-gaap_PlanNameDomain_CE4BE1E6441263C5A3F2D8248745C8DA" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_PlanNameAxis_CC8B6CE6B26E02DA03DDD8248745CA53" xlink:to="loc_us-gaap_PlanNameDomain_CE4BE1E6441263C5A3F2D8248745C8DA" xlink:type="arc" />
    <link:loc xlink:href="anab-20180630.xsd#anab_EquityIncentivePlan2017Member" xlink:label="loc_anab_EquityIncentivePlan2017Member_B023046F724DC456C10CD8248745739F" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PlanNameDomain_CE4BE1E6441263C5A3F2D8248745C8DA" xlink:to="loc_anab_EquityIncentivePlan2017Member_B023046F724DC456C10CD8248745739F" xlink:type="arc" />
    <link:loc xlink:href="anab-20180630.xsd#anab_EmployeeStockPurchasePlan2017Member" xlink:label="loc_anab_EmployeeStockPurchasePlan2017Member_B279A47F1857F1E86641D82487466A28" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PlanNameDomain_CE4BE1E6441263C5A3F2D8248745C8DA" xlink:to="loc_anab_EmployeeStockPurchasePlan2017Member_B279A47F1857F1E86641D82487466A28" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_AwardTypeAxis" xlink:label="loc_us-gaap_AwardTypeAxis_5C04595C35D3D2FA15BAD8248746A295" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_4E507D327FEFFEBA6DB1D82487454F71" xlink:to="loc_us-gaap_AwardTypeAxis_5C04595C35D3D2FA15BAD8248746A295" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_9B1CDD229D14015F3B65D8248747006E_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_AwardTypeAxis_5C04595C35D3D2FA15BAD8248746A295" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_9B1CDD229D14015F3B65D8248747006E_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_9B1CDD229D14015F3B65D8248747006E" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_AwardTypeAxis_5C04595C35D3D2FA15BAD8248746A295" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_9B1CDD229D14015F3B65D8248747006E" xlink:type="arc" />
    <link:loc xlink:href="anab-20180630.xsd#anab_FormerlyIssuableCommonSharesMember" xlink:label="loc_anab_FormerlyIssuableCommonSharesMember_832CCA074CCD2AD3D766D82487479ECC" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_9B1CDD229D14015F3B65D8248747006E" xlink:to="loc_anab_FormerlyIssuableCommonSharesMember_832CCA074CCD2AD3D766D82487479ECC" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_EmployeeStockMember" xlink:label="loc_us-gaap_EmployeeStockMember_9EF969601A4322CA356BD82487475FC1" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_9B1CDD229D14015F3B65D8248747006E" xlink:to="loc_us-gaap_EmployeeStockMember_9EF969601A4322CA356BD82487475FC1" xlink:type="arc" />
    <link:loc xlink:href="anab-20180630.xsd#anab_EmployeeAndNonemployeeStockOptionsMember" xlink:label="loc_anab_EmployeeAndNonemployeeStockOptionsMember_BFA671E232463882E650D82487473929" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_9B1CDD229D14015F3B65D8248747006E" xlink:to="loc_anab_EmployeeAndNonemployeeStockOptionsMember_BFA671E232463882E650D82487473929" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_EmployeeStockOptionMember" xlink:label="loc_us-gaap_EmployeeStockOptionMember_FEDCCDE4F43FF843F094D8248748310D" xlink:type="locator" />
    <link:definitionArc order="4" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_9B1CDD229D14015F3B65D8248747006E" xlink:to="loc_us-gaap_EmployeeStockOptionMember_FEDCCDE4F43FF843F094D8248748310D" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_TitleOfIndividualAxis" xlink:label="loc_us-gaap_TitleOfIndividualAxis_057BA530BEAFC9A0E4CAD8248748A66A" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_4E507D327FEFFEBA6DB1D82487454F71" xlink:to="loc_us-gaap_TitleOfIndividualAxis_057BA530BEAFC9A0E4CAD8248748A66A" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_TitleOfIndividualWithRelationshipToEntityDomain" xlink:label="loc_us-gaap_TitleOfIndividualWithRelationshipToEntityDomain_652E94B4D6D1415CE194D8248748B6EB_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_TitleOfIndividualAxis_057BA530BEAFC9A0E4CAD8248748A66A" xlink:to="loc_us-gaap_TitleOfIndividualWithRelationshipToEntityDomain_652E94B4D6D1415CE194D8248748B6EB_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_TitleOfIndividualWithRelationshipToEntityDomain" xlink:label="loc_us-gaap_TitleOfIndividualWithRelationshipToEntityDomain_652E94B4D6D1415CE194D8248748B6EB" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_TitleOfIndividualAxis_057BA530BEAFC9A0E4CAD8248748A66A" xlink:to="loc_us-gaap_TitleOfIndividualWithRelationshipToEntityDomain_652E94B4D6D1415CE194D8248748B6EB" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_DirectorMember" xlink:label="loc_us-gaap_DirectorMember_D2F72959670E69B26542D8248748E4DE" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TitleOfIndividualWithRelationshipToEntityDomain_652E94B4D6D1415CE194D8248748B6EB" xlink:to="loc_us-gaap_DirectorMember_D2F72959670E69B26542D8248748E4DE" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_CommonStockCapitalSharesReservedForFutureIssuance" xlink:label="loc_us-gaap_CommonStockCapitalSharesReservedForFutureIssuance_1BF518BDE739DC3BCD21D824874987EA" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_BFDBAB68C379B2DE5F7FD8248749B706" xlink:to="loc_us-gaap_CommonStockCapitalSharesReservedForFutureIssuance_1BF518BDE739DC3BCD21D824874987EA" xlink:type="arc" />
    <link:loc xlink:href="anab-20180630.xsd#anab_CommonStockCapitalSharesReservedForFutureIssuanceAnnualIncreasePercentOfAggregateSharesOutstanding" xlink:label="loc_anab_CommonStockCapitalSharesReservedForFutureIssuanceAnnualIncreasePercentOfAggregateSharesOutstanding_2D9A6B31913231CAEAA0D8248749AD16" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_BFDBAB68C379B2DE5F7FD8248749B706" xlink:to="loc_anab_CommonStockCapitalSharesReservedForFutureIssuanceAnnualIncreasePercentOfAggregateSharesOutstanding_2D9A6B31913231CAEAA0D8248749AD16" xlink:type="arc" />
    <link:loc xlink:href="anab-20180630.xsd#anab_CommonStockCapitalSharesReservedForFutureIssuanceIncrease" xlink:label="loc_anab_CommonStockCapitalSharesReservedForFutureIssuanceIncrease_6ED77EE798D7A348BD86D824874A0000" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_BFDBAB68C379B2DE5F7FD8248749B706" xlink:to="loc_anab_CommonStockCapitalSharesReservedForFutureIssuanceIncrease_6ED77EE798D7A348BD86D824874A0000" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingNumber" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingNumber_5F1345098B98D331681BD824874A8816" xlink:type="locator" />
    <link:definitionArc order="4" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_BFDBAB68C379B2DE5F7FD8248749B706" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingNumber_5F1345098B98D331681BD824874A8816" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardAwardVestingPeriod1" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardAwardVestingPeriod1_16B268A0872DCE6AEB19D824874AF99D" xlink:type="locator" />
    <link:definitionArc order="5" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_BFDBAB68C379B2DE5F7FD8248749B706" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardAwardVestingPeriod1_16B268A0872DCE6AEB19D824874AF99D" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardExpirationPeriod" xlink:label="loc_us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardExpirationPeriod_59BE6F552F12FCA89426D824874BCA38" xlink:type="locator" />
    <link:definitionArc order="6" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_BFDBAB68C379B2DE5F7FD8248749B706" xlink:to="loc_us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardExpirationPeriod_59BE6F552F12FCA89426D824874BCA38" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_ProceedsFromStockOptionsExercised" xlink:label="loc_us-gaap_ProceedsFromStockOptionsExercised_4CDC1ECCEDC834E777EFD824874B77AA" xlink:type="locator" />
    <link:definitionArc order="7" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_BFDBAB68C379B2DE5F7FD8248749B706" xlink:to="loc_us-gaap_ProceedsFromStockOptionsExercised_4CDC1ECCEDC834E777EFD824874B77AA" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriodGross" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriodGross_751380E18ACEB6B8123ED824874CA92D" xlink:type="locator" />
    <link:definitionArc order="8" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_BFDBAB68C379B2DE5F7FD8248749B706" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriodGross_751380E18ACEB6B8123ED824874CA92D" xlink:type="arc" />
    <link:loc xlink:href="anab-20180630.xsd#anab_EmployeeAndNonemployeeServiceSharebasedCompensationNonvestedAwardsCompensationNotYetRecognizedStockOptions" xlink:label="loc_anab_EmployeeAndNonemployeeServiceSharebasedCompensationNonvestedAwardsCompensationNotYetRecognizedStockOptions_E04B6D6DC55599E95A09D824874C9031" xlink:type="locator" />
    <link:definitionArc order="9" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_BFDBAB68C379B2DE5F7FD8248749B706" xlink:to="loc_anab_EmployeeAndNonemployeeServiceSharebasedCompensationNonvestedAwardsCompensationNotYetRecognizedStockOptions_E04B6D6DC55599E95A09D824874C9031" xlink:type="arc" />
    <link:loc xlink:href="anab-20180630.xsd#anab_EmployeeAndNonemployeeServiceSharebasedCompensationNonvestedAwardsCompensationCostNotYetRecognizedPeriodForRecognition" xlink:label="loc_anab_EmployeeAndNonemployeeServiceSharebasedCompensationNonvestedAwardsCompensationCostNotYetRecognizedPeriodForRecognition_EE2287542CFBDE092A5BD824874C72D6" xlink:type="locator" />
    <link:definitionArc order="10" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_BFDBAB68C379B2DE5F7FD8248749B706" xlink:to="loc_anab_EmployeeAndNonemployeeServiceSharebasedCompensationNonvestedAwardsCompensationCostNotYetRecognizedPeriodForRecognition_EE2287542CFBDE092A5BD824874C72D6" xlink:type="arc" />
  </link:definitionLink>
  <link:definitionLink xlink:role="http://www.anaptysbio.com/role/EquityIncentivePlansOptionActivityDetails" xlink:type="extended" />
  <link:definitionLink xlink:role="http://www.anaptysbio.com/role/EquityIncentivePlansOptionFairValueAssumptionsDetails" xlink:type="extended">
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_EF553BEB78FD00184604480642FCAC9D" xlink:type="locator" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable" xlink:label="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_A5EE212C8A023EEFB35A480642FB51C5" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_EF553BEB78FD00184604480642FCAC9D" xlink:to="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_A5EE212C8A023EEFB35A480642FB51C5" xlink:type="arc" xbrldt:closed="true" xbrldt:contextElement="segment" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_AwardTypeAxis" xlink:label="loc_us-gaap_AwardTypeAxis_D9C28B385E12F6CEF929480642FCEF8A" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_A5EE212C8A023EEFB35A480642FB51C5" xlink:to="loc_us-gaap_AwardTypeAxis_D9C28B385E12F6CEF929480642FCEF8A" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_6E5420A46993B4080EE8480642FCE643_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_AwardTypeAxis_D9C28B385E12F6CEF929480642FCEF8A" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_6E5420A46993B4080EE8480642FCE643_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_6E5420A46993B4080EE8480642FCE643" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_AwardTypeAxis_D9C28B385E12F6CEF929480642FCEF8A" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_6E5420A46993B4080EE8480642FCE643" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_EmployeeStockOptionMember" xlink:label="loc_us-gaap_EmployeeStockOptionMember_F928AC095216589BE7BF480642FC76B3" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_6E5420A46993B4080EE8480642FCE643" xlink:to="loc_us-gaap_EmployeeStockOptionMember_F928AC095216589BE7BF480642FC76B3" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsRiskFreeInterestRate" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsRiskFreeInterestRate_883E0A25A8BFC4E863CA480642FDCA30" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_EF553BEB78FD00184604480642FCAC9D" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsRiskFreeInterestRate_883E0A25A8BFC4E863CA480642FDCA30" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsExpectedVolatilityRate" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsExpectedVolatilityRate_8251E131F5894216208E480642FD0001" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_EF553BEB78FD00184604480642FCAC9D" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsExpectedVolatilityRate_8251E131F5894216208E480642FD0001" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsExpectedDividendRate" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsExpectedDividendRate_DE3C3ABADF1F07BF52A3480642FD5E1C" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_EF553BEB78FD00184604480642FCAC9D" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsExpectedDividendRate_DE3C3ABADF1F07BF52A3480642FD5E1C" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardFairValueAssumptionsExpectedTerm1" xlink:label="loc_us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardFairValueAssumptionsExpectedTerm1_C9F47E09E4F15D63B274480642FD7590" xlink:type="locator" />
    <link:definitionArc order="4" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_EF553BEB78FD00184604480642FCAC9D" xlink:to="loc_us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardFairValueAssumptionsExpectedTerm1_C9F47E09E4F15D63B274480642FD7590" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriodWeightedAverageGrantDateFairValue" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriodWeightedAverageGrantDateFairValue_0C3C6129D14C1CEAB6C2480642FD108C" xlink:type="locator" />
    <link:definitionArc order="5" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_EF553BEB78FD00184604480642FCAC9D" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriodWeightedAverageGrantDateFairValue_0C3C6129D14C1CEAB6C2480642FD108C" xlink:type="arc" />
  </link:definitionLink>
  <link:definitionLink xlink:role="http://www.anaptysbio.com/role/EquityIncentivePlansTables" xlink:type="extended" />
  <link:definitionLink xlink:role="http://www.anaptysbio.com/role/FairValueMeasurementsAndAvailableForSaleInvestments" xlink:type="extended" />
  <link:definitionLink xlink:role="http://www.anaptysbio.com/role/FairValueMeasurementsAndAvailableForSaleInvestmentsAssetsAndLiabilitiesMeasuredAtFairValueOnRecurringBasisDetails" xlink:type="extended">
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems" xlink:label="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_850165E864F78E2C6F774806436EFAA2" xlink:type="locator" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable" xlink:label="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable_BCB6CC86EF0EB4AD9F5F48064369D5A2" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_850165E864F78E2C6F774806436EFAA2" xlink:to="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable_BCB6CC86EF0EB4AD9F5F48064369D5A2" xlink:type="arc" xbrldt:closed="true" xbrldt:contextElement="segment" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_FairValueByMeasurementFrequencyAxis" xlink:label="loc_us-gaap_FairValueByMeasurementFrequencyAxis_C937FAA2FEB1A61F780E48064369933E" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable_BCB6CC86EF0EB4AD9F5F48064369D5A2" xlink:to="loc_us-gaap_FairValueByMeasurementFrequencyAxis_C937FAA2FEB1A61F780E48064369933E" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_FairValueMeasurementFrequencyDomain" xlink:label="loc_us-gaap_FairValueMeasurementFrequencyDomain_AF9D58C5073029DB7AD24806436A5BA8_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_FairValueByMeasurementFrequencyAxis_C937FAA2FEB1A61F780E48064369933E" xlink:to="loc_us-gaap_FairValueMeasurementFrequencyDomain_AF9D58C5073029DB7AD24806436A5BA8_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_FairValueMeasurementFrequencyDomain" xlink:label="loc_us-gaap_FairValueMeasurementFrequencyDomain_AF9D58C5073029DB7AD24806436A5BA8" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_FairValueByMeasurementFrequencyAxis_C937FAA2FEB1A61F780E48064369933E" xlink:to="loc_us-gaap_FairValueMeasurementFrequencyDomain_AF9D58C5073029DB7AD24806436A5BA8" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_FairValueMeasurementsRecurringMember" xlink:label="loc_us-gaap_FairValueMeasurementsRecurringMember_C6E6B90DAC3A63276EDF4806436AB0EA" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueMeasurementFrequencyDomain_AF9D58C5073029DB7AD24806436A5BA8" xlink:to="loc_us-gaap_FairValueMeasurementsRecurringMember_C6E6B90DAC3A63276EDF4806436AB0EA" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_FairValueByFairValueHierarchyLevelAxis" xlink:label="loc_us-gaap_FairValueByFairValueHierarchyLevelAxis_88358E96C808769AC4694806436AF720" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable_BCB6CC86EF0EB4AD9F5F48064369D5A2" xlink:to="loc_us-gaap_FairValueByFairValueHierarchyLevelAxis_88358E96C808769AC4694806436AF720" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_FairValueMeasurementsFairValueHierarchyDomain" xlink:label="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_92C6F01BE5C94D8F27C44806436B9C9D_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_FairValueByFairValueHierarchyLevelAxis_88358E96C808769AC4694806436AF720" xlink:to="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_92C6F01BE5C94D8F27C44806436B9C9D_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_FairValueMeasurementsFairValueHierarchyDomain" xlink:label="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_92C6F01BE5C94D8F27C44806436B9C9D" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_FairValueByFairValueHierarchyLevelAxis_88358E96C808769AC4694806436AF720" xlink:to="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_92C6F01BE5C94D8F27C44806436B9C9D" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_FairValueInputsLevel1Member" xlink:label="loc_us-gaap_FairValueInputsLevel1Member_C019412E9069085045214806436BF0BB" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_92C6F01BE5C94D8F27C44806436B9C9D" xlink:to="loc_us-gaap_FairValueInputsLevel1Member_C019412E9069085045214806436BF0BB" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_FairValueInputsLevel2Member" xlink:label="loc_us-gaap_FairValueInputsLevel2Member_61DA550C1000BEBEE4574806436B86B6" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_92C6F01BE5C94D8F27C44806436B9C9D" xlink:to="loc_us-gaap_FairValueInputsLevel2Member_61DA550C1000BEBEE4574806436B86B6" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_FairValueInputsLevel3Member" xlink:label="loc_us-gaap_FairValueInputsLevel3Member_DE4EC5212433100632864806436C818B" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_92C6F01BE5C94D8F27C44806436B9C9D" xlink:to="loc_us-gaap_FairValueInputsLevel3Member_DE4EC5212433100632864806436C818B" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_CashAndCashEquivalentsAxis" xlink:label="loc_us-gaap_CashAndCashEquivalentsAxis_19DBD096981AD9D2E1564806436CADCF" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable_BCB6CC86EF0EB4AD9F5F48064369D5A2" xlink:to="loc_us-gaap_CashAndCashEquivalentsAxis_19DBD096981AD9D2E1564806436CADCF" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_RestrictedCashAndCashEquivalentsCashAndCashEquivalentsMember" xlink:label="loc_us-gaap_RestrictedCashAndCashEquivalentsCashAndCashEquivalentsMember_BD0F3DBA13B09176BE064806436C798E_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_CashAndCashEquivalentsAxis_19DBD096981AD9D2E1564806436CADCF" xlink:to="loc_us-gaap_RestrictedCashAndCashEquivalentsCashAndCashEquivalentsMember_BD0F3DBA13B09176BE064806436C798E_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_RestrictedCashAndCashEquivalentsCashAndCashEquivalentsMember" xlink:label="loc_us-gaap_RestrictedCashAndCashEquivalentsCashAndCashEquivalentsMember_BD0F3DBA13B09176BE064806436C798E" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_CashAndCashEquivalentsAxis_19DBD096981AD9D2E1564806436CADCF" xlink:to="loc_us-gaap_RestrictedCashAndCashEquivalentsCashAndCashEquivalentsMember_BD0F3DBA13B09176BE064806436C798E" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_MoneyMarketFundsMember" xlink:label="loc_us-gaap_MoneyMarketFundsMember_0AD5205C0C986AA03AA84806436C8654" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RestrictedCashAndCashEquivalentsCashAndCashEquivalentsMember_BD0F3DBA13B09176BE064806436C798E" xlink:to="loc_us-gaap_MoneyMarketFundsMember_0AD5205C0C986AA03AA84806436C8654" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_MutualFundMember" xlink:label="loc_us-gaap_MutualFundMember_6245E0E8E3BBC9B8C5964806436D31CE" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RestrictedCashAndCashEquivalentsCashAndCashEquivalentsMember_BD0F3DBA13B09176BE064806436C798E" xlink:to="loc_us-gaap_MutualFundMember_6245E0E8E3BBC9B8C5964806436D31CE" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_FinancialInstrumentAxis" xlink:label="loc_us-gaap_FinancialInstrumentAxis_C92BDDD780D280E4BC384806436DCABC" xlink:type="locator" />
    <link:definitionArc order="4" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable_BCB6CC86EF0EB4AD9F5F48064369D5A2" xlink:to="loc_us-gaap_FinancialInstrumentAxis_C92BDDD780D280E4BC384806436DCABC" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain" xlink:label="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_5BF193E229422E4AAF8E4806436D03D3_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_FinancialInstrumentAxis_C92BDDD780D280E4BC384806436DCABC" xlink:to="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_5BF193E229422E4AAF8E4806436D03D3_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain" xlink:label="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_5BF193E229422E4AAF8E4806436D03D3" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_FinancialInstrumentAxis_C92BDDD780D280E4BC384806436DCABC" xlink:to="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_5BF193E229422E4AAF8E4806436D03D3" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_USTreasurySecuritiesMember" xlink:label="loc_us-gaap_USTreasurySecuritiesMember_CC8D542766A18ABB94FC4806436D46A1" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_5BF193E229422E4AAF8E4806436D03D3" xlink:to="loc_us-gaap_USTreasurySecuritiesMember_CC8D542766A18ABB94FC4806436D46A1" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_USGovernmentAgenciesDebtSecuritiesMember" xlink:label="loc_us-gaap_USGovernmentAgenciesDebtSecuritiesMember_76F5BBF8646185D4B4B74806436EB490" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_5BF193E229422E4AAF8E4806436D03D3" xlink:to="loc_us-gaap_USGovernmentAgenciesDebtSecuritiesMember_76F5BBF8646185D4B4B74806436EB490" xlink:type="arc" />
    <link:loc xlink:href="anab-20180630.xsd#anab_CommercialAndCorporateObligationsMember" xlink:label="loc_anab_CommercialAndCorporateObligationsMember_6D876503B7736F2FC2334806436E3572" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_5BF193E229422E4AAF8E4806436D03D3" xlink:to="loc_anab_CommercialAndCorporateObligationsMember_6D876503B7736F2FC2334806436E3572" xlink:type="arc" />
    <link:loc xlink:href="anab-20180630.xsd#anab_CashAndCashEquivalentsAndRestrictedCashFairValueDisclosure" xlink:label="loc_anab_CashAndCashEquivalentsAndRestrictedCashFairValueDisclosure_150AA8C6CFF4B0F9616B4806436E0B14" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_850165E864F78E2C6F774806436EFAA2" xlink:to="loc_anab_CashAndCashEquivalentsAndRestrictedCashFairValueDisclosure_150AA8C6CFF4B0F9616B4806436E0B14" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_AvailableForSaleSecuritiesDebtSecurities" xlink:label="loc_us-gaap_AvailableForSaleSecuritiesDebtSecurities_2AC5C399A9D88C82A7304806436EEEC9" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_850165E864F78E2C6F774806436EFAA2" xlink:to="loc_us-gaap_AvailableForSaleSecuritiesDebtSecurities_2AC5C399A9D88C82A7304806436EEEC9" xlink:type="arc" />
  </link:definitionLink>
  <link:definitionLink xlink:role="http://www.anaptysbio.com/role/FairValueMeasurementsAndAvailableForSaleInvestmentsAvailableForSaleInvestmentsDetails" xlink:type="extended">
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_ScheduleOfAvailableForSaleSecuritiesLineItems" xlink:label="loc_us-gaap_ScheduleOfAvailableForSaleSecuritiesLineItems_C87FFC6F869322786471483D5958C077" xlink:type="locator" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_DebtSecuritiesAvailableForSaleTable" xlink:label="loc_us-gaap_DebtSecuritiesAvailableForSaleTable_0A02308F793FFEC7B977483D59552D24" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_ScheduleOfAvailableForSaleSecuritiesLineItems_C87FFC6F869322786471483D5958C077" xlink:to="loc_us-gaap_DebtSecuritiesAvailableForSaleTable_0A02308F793FFEC7B977483D59552D24" xlink:type="arc" xbrldt:closed="true" xbrldt:contextElement="segment" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_FinancialInstrumentAxis" xlink:label="loc_us-gaap_FinancialInstrumentAxis_50B7821EE65BCD90F0A4483D5955B3CD" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DebtSecuritiesAvailableForSaleTable_0A02308F793FFEC7B977483D59552D24" xlink:to="loc_us-gaap_FinancialInstrumentAxis_50B7821EE65BCD90F0A4483D5955B3CD" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain" xlink:label="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_F576E1990F6F399C35F4483D59565DFA_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_FinancialInstrumentAxis_50B7821EE65BCD90F0A4483D5955B3CD" xlink:to="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_F576E1990F6F399C35F4483D59565DFA_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain" xlink:label="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_F576E1990F6F399C35F4483D59565DFA" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_FinancialInstrumentAxis_50B7821EE65BCD90F0A4483D5955B3CD" xlink:to="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_F576E1990F6F399C35F4483D59565DFA" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_USGovernmentAgenciesDebtSecuritiesMember" xlink:label="loc_us-gaap_USGovernmentAgenciesDebtSecuritiesMember_24FC13C8183BE5658F15483D5956C799" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_F576E1990F6F399C35F4483D59565DFA" xlink:to="loc_us-gaap_USGovernmentAgenciesDebtSecuritiesMember_24FC13C8183BE5658F15483D5956C799" xlink:type="arc" />
    <link:loc xlink:href="anab-20180630.xsd#anab_CommercialAndCorporateObligationsMember" xlink:label="loc_anab_CommercialAndCorporateObligationsMember_3882143215AF2600C8F2483D5957A1CA" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_F576E1990F6F399C35F4483D59565DFA" xlink:to="loc_anab_CommercialAndCorporateObligationsMember_3882143215AF2600C8F2483D5957A1CA" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_USTreasurySecuritiesMember" xlink:label="loc_us-gaap_USTreasurySecuritiesMember_0DF44EB08159A2528DEC483D5957B169" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_F576E1990F6F399C35F4483D59565DFA" xlink:to="loc_us-gaap_USTreasurySecuritiesMember_0DF44EB08159A2528DEC483D5957B169" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/srt/2018/elts/srt-2018-01-31.xsd#srt_RangeAxis" xlink:label="loc_srt_RangeAxis_877F9DA56364B8D1FF87483D5957720B" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DebtSecuritiesAvailableForSaleTable_0A02308F793FFEC7B977483D59552D24" xlink:to="loc_srt_RangeAxis_877F9DA56364B8D1FF87483D5957720B" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/srt/2018/elts/srt-2018-01-31.xsd#srt_RangeMember" xlink:label="loc_srt_RangeMember_62838A167F2C319A5963483D595718A5_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_RangeAxis_877F9DA56364B8D1FF87483D5957720B" xlink:to="loc_srt_RangeMember_62838A167F2C319A5963483D595718A5_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/srt/2018/elts/srt-2018-01-31.xsd#srt_RangeMember" xlink:label="loc_srt_RangeMember_62838A167F2C319A5963483D595718A5" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_RangeAxis_877F9DA56364B8D1FF87483D5957720B" xlink:to="loc_srt_RangeMember_62838A167F2C319A5963483D595718A5" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/srt/2018/elts/srt-2018-01-31.xsd#srt_MinimumMember" xlink:label="loc_srt_MinimumMember_5B22C1F11AD1BE45D870483D5958C154" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_RangeMember_62838A167F2C319A5963483D595718A5" xlink:to="loc_srt_MinimumMember_5B22C1F11AD1BE45D870483D5958C154" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/srt/2018/elts/srt-2018-01-31.xsd#srt_MaximumMember" xlink:label="loc_srt_MaximumMember_C0ED767546BE85880797483D595894AF" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_RangeMember_62838A167F2C319A5963483D595718A5" xlink:to="loc_srt_MaximumMember_C0ED767546BE85880797483D595894AF" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_AvailableForSaleDebtSecuritiesAmortizedCostBasis" xlink:label="loc_us-gaap_AvailableForSaleDebtSecuritiesAmortizedCostBasis_BE13A8975C5B2A3F2947483D59582DCF" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ScheduleOfAvailableForSaleSecuritiesLineItems_C87FFC6F869322786471483D5958C077" xlink:to="loc_us-gaap_AvailableForSaleDebtSecuritiesAmortizedCostBasis_BE13A8975C5B2A3F2947483D59582DCF" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_AvailableForSaleDebtSecuritiesAccumulatedGrossUnrealizedGainBeforeTax" xlink:label="loc_us-gaap_AvailableForSaleDebtSecuritiesAccumulatedGrossUnrealizedGainBeforeTax_3F6352A8C08BF8F2F28E483D5959F546" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ScheduleOfAvailableForSaleSecuritiesLineItems_C87FFC6F869322786471483D5958C077" xlink:to="loc_us-gaap_AvailableForSaleDebtSecuritiesAccumulatedGrossUnrealizedGainBeforeTax_3F6352A8C08BF8F2F28E483D5959F546" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_AvailableForSaleDebtSecuritiesAccumulatedGrossUnrealizedLossBeforeTax" xlink:label="loc_us-gaap_AvailableForSaleDebtSecuritiesAccumulatedGrossUnrealizedLossBeforeTax_F27FAA8757034A7F3B2C483D59596672" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ScheduleOfAvailableForSaleSecuritiesLineItems_C87FFC6F869322786471483D5958C077" xlink:to="loc_us-gaap_AvailableForSaleDebtSecuritiesAccumulatedGrossUnrealizedLossBeforeTax_F27FAA8757034A7F3B2C483D59596672" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_AvailableForSaleSecuritiesDebtSecurities" xlink:label="loc_us-gaap_AvailableForSaleSecuritiesDebtSecurities_C9525B76F0BE597F2ED7483D5959B9F1" xlink:type="locator" />
    <link:definitionArc order="4" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ScheduleOfAvailableForSaleSecuritiesLineItems_C87FFC6F869322786471483D5958C077" xlink:to="loc_us-gaap_AvailableForSaleSecuritiesDebtSecurities_C9525B76F0BE597F2ED7483D5959B9F1" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_AvailableForSaleSecuritiesDebtSecuritiesCurrent" xlink:label="loc_us-gaap_AvailableForSaleSecuritiesDebtSecuritiesCurrent_F9DC8A05710F36F6B725483D5959183A" xlink:type="locator" />
    <link:definitionArc order="5" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ScheduleOfAvailableForSaleSecuritiesLineItems_C87FFC6F869322786471483D5958C077" xlink:to="loc_us-gaap_AvailableForSaleSecuritiesDebtSecuritiesCurrent_F9DC8A05710F36F6B725483D5959183A" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_AvailableForSaleSecuritiesDebtSecuritiesNoncurrent" xlink:label="loc_us-gaap_AvailableForSaleSecuritiesDebtSecuritiesNoncurrent_F8D16510320F0D7E53E8483D595A9355" xlink:type="locator" />
    <link:definitionArc order="6" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ScheduleOfAvailableForSaleSecuritiesLineItems_C87FFC6F869322786471483D5958C077" xlink:to="loc_us-gaap_AvailableForSaleSecuritiesDebtSecuritiesNoncurrent_F8D16510320F0D7E53E8483D595A9355" xlink:type="arc" />
    <link:loc xlink:href="anab-20180630.xsd#anab_AvailableforsaleDebtSecuritiesRemainingMaturity" xlink:label="loc_anab_AvailableforsaleDebtSecuritiesRemainingMaturity_17453F16BDDCCA7BB4C7483D595AE3F2" xlink:type="locator" />
    <link:definitionArc order="7" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ScheduleOfAvailableForSaleSecuritiesLineItems_C87FFC6F869322786471483D5958C077" xlink:to="loc_anab_AvailableforsaleDebtSecuritiesRemainingMaturity_17453F16BDDCCA7BB4C7483D595AE3F2" xlink:type="arc" />
  </link:definitionLink>
  <link:definitionLink xlink:role="http://www.anaptysbio.com/role/FairValueMeasurementsAndAvailableForSaleInvestmentsFairValueAssumptionsDetails" xlink:type="extended">
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisValuationTechniquesLineItems" xlink:label="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisValuationTechniquesLineItems_27AB5B6517579EAF99674807C3A844CA" xlink:type="locator" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisValuationTechniquesTable" xlink:label="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisValuationTechniquesTable_AA02F888B1A87B5829DC4807C3A38950" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisValuationTechniquesLineItems_27AB5B6517579EAF99674807C3A844CA" xlink:to="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisValuationTechniquesTable_AA02F888B1A87B5829DC4807C3A38950" xlink:type="arc" xbrldt:closed="true" xbrldt:contextElement="segment" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_FairValueByLiabilityClassAxis" xlink:label="loc_us-gaap_FairValueByLiabilityClassAxis_921543D5EF8B8CB204314807C3A3C3A3" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisValuationTechniquesTable_AA02F888B1A87B5829DC4807C3A38950" xlink:to="loc_us-gaap_FairValueByLiabilityClassAxis_921543D5EF8B8CB204314807C3A3C3A3" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_FairValueLiabilitiesMeasuredOnRecurringBasisUnobservableInputReconciliationByLiabilityClassDomain" xlink:label="loc_us-gaap_FairValueLiabilitiesMeasuredOnRecurringBasisUnobservableInputReconciliationByLiabilityClassDomain_440CE2D89CAD1E03A5A14807C3A4063E_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_FairValueByLiabilityClassAxis_921543D5EF8B8CB204314807C3A3C3A3" xlink:to="loc_us-gaap_FairValueLiabilitiesMeasuredOnRecurringBasisUnobservableInputReconciliationByLiabilityClassDomain_440CE2D89CAD1E03A5A14807C3A4063E_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_FairValueLiabilitiesMeasuredOnRecurringBasisUnobservableInputReconciliationByLiabilityClassDomain" xlink:label="loc_us-gaap_FairValueLiabilitiesMeasuredOnRecurringBasisUnobservableInputReconciliationByLiabilityClassDomain_440CE2D89CAD1E03A5A14807C3A4063E" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_FairValueByLiabilityClassAxis_921543D5EF8B8CB204314807C3A3C3A3" xlink:to="loc_us-gaap_FairValueLiabilitiesMeasuredOnRecurringBasisUnobservableInputReconciliationByLiabilityClassDomain_440CE2D89CAD1E03A5A14807C3A4063E" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_DerivativeFinancialInstrumentsLiabilitiesMember" xlink:label="loc_us-gaap_DerivativeFinancialInstrumentsLiabilitiesMember_5D06055DEA49025DEAC54807C3A4CDF0" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueLiabilitiesMeasuredOnRecurringBasisUnobservableInputReconciliationByLiabilityClassDomain_440CE2D89CAD1E03A5A14807C3A4063E" xlink:to="loc_us-gaap_DerivativeFinancialInstrumentsLiabilitiesMember_5D06055DEA49025DEAC54807C3A4CDF0" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_FairValueByMeasurementFrequencyAxis" xlink:label="loc_us-gaap_FairValueByMeasurementFrequencyAxis_D025DD321B0F1A03E91B4807C3A4A6E4" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisValuationTechniquesTable_AA02F888B1A87B5829DC4807C3A38950" xlink:to="loc_us-gaap_FairValueByMeasurementFrequencyAxis_D025DD321B0F1A03E91B4807C3A4A6E4" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_FairValueMeasurementFrequencyDomain" xlink:label="loc_us-gaap_FairValueMeasurementFrequencyDomain_21621E4A5DE791502F904807C3A5B456_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_FairValueByMeasurementFrequencyAxis_D025DD321B0F1A03E91B4807C3A4A6E4" xlink:to="loc_us-gaap_FairValueMeasurementFrequencyDomain_21621E4A5DE791502F904807C3A5B456_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_FairValueMeasurementFrequencyDomain" xlink:label="loc_us-gaap_FairValueMeasurementFrequencyDomain_21621E4A5DE791502F904807C3A5B456" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_FairValueByMeasurementFrequencyAxis_D025DD321B0F1A03E91B4807C3A4A6E4" xlink:to="loc_us-gaap_FairValueMeasurementFrequencyDomain_21621E4A5DE791502F904807C3A5B456" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_FairValueMeasurementsRecurringMember" xlink:label="loc_us-gaap_FairValueMeasurementsRecurringMember_AFA88909E520A2CF50824807C3A59E31" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueMeasurementFrequencyDomain_21621E4A5DE791502F904807C3A5B456" xlink:to="loc_us-gaap_FairValueMeasurementsRecurringMember_AFA88909E520A2CF50824807C3A59E31" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_StatementClassOfStockAxis" xlink:label="loc_us-gaap_StatementClassOfStockAxis_D5FAAE01916DCE85479F4807C3A657E8" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisValuationTechniquesTable_AA02F888B1A87B5829DC4807C3A38950" xlink:to="loc_us-gaap_StatementClassOfStockAxis_D5FAAE01916DCE85479F4807C3A657E8" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_ClassOfStockDomain" xlink:label="loc_us-gaap_ClassOfStockDomain_BB373DB6F53703D8EDEC4807C3A6343C_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_StatementClassOfStockAxis_D5FAAE01916DCE85479F4807C3A657E8" xlink:to="loc_us-gaap_ClassOfStockDomain_BB373DB6F53703D8EDEC4807C3A6343C_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_ClassOfStockDomain" xlink:label="loc_us-gaap_ClassOfStockDomain_BB373DB6F53703D8EDEC4807C3A6343C" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_StatementClassOfStockAxis_D5FAAE01916DCE85479F4807C3A657E8" xlink:to="loc_us-gaap_ClassOfStockDomain_BB373DB6F53703D8EDEC4807C3A6343C" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_SeriesCPreferredStockMember" xlink:label="loc_us-gaap_SeriesCPreferredStockMember_36F2602CE850C9D7F23D4807C3A70564" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockDomain_BB373DB6F53703D8EDEC4807C3A6343C" xlink:to="loc_us-gaap_SeriesCPreferredStockMember_36F2602CE850C9D7F23D4807C3A70564" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_MeasurementInputTypeAxis" xlink:label="loc_us-gaap_MeasurementInputTypeAxis_DCD4A2984FE64C6124644814893F1AFF" xlink:type="locator" />
    <link:definitionArc order="4" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisValuationTechniquesTable_AA02F888B1A87B5829DC4807C3A38950" xlink:to="loc_us-gaap_MeasurementInputTypeAxis_DCD4A2984FE64C6124644814893F1AFF" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_MeasurementInputTypeDomain" xlink:label="loc_us-gaap_MeasurementInputTypeDomain_A5DBA21C89CFF1976630481489419B78_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_MeasurementInputTypeAxis_DCD4A2984FE64C6124644814893F1AFF" xlink:to="loc_us-gaap_MeasurementInputTypeDomain_A5DBA21C89CFF1976630481489419B78_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_MeasurementInputTypeDomain" xlink:label="loc_us-gaap_MeasurementInputTypeDomain_A5DBA21C89CFF1976630481489419B78" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_MeasurementInputTypeAxis_DCD4A2984FE64C6124644814893F1AFF" xlink:to="loc_us-gaap_MeasurementInputTypeDomain_A5DBA21C89CFF1976630481489419B78" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_MeasurementInputExercisePriceMember" xlink:label="loc_us-gaap_MeasurementInputExercisePriceMember_D875A6D719D1817FF5124814D97BF873" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_MeasurementInputTypeDomain_A5DBA21C89CFF1976630481489419B78" xlink:to="loc_us-gaap_MeasurementInputExercisePriceMember_D875A6D719D1817FF5124814D97BF873" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_MeasurementInputRiskFreeInterestRateMember" xlink:label="loc_us-gaap_MeasurementInputRiskFreeInterestRateMember_89AD2C6F66BE5A31D40B4815C9604A1A" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_MeasurementInputTypeDomain_A5DBA21C89CFF1976630481489419B78" xlink:to="loc_us-gaap_MeasurementInputRiskFreeInterestRateMember_89AD2C6F66BE5A31D40B4815C9604A1A" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_MeasurementInputOptionVolatilityMember" xlink:label="loc_us-gaap_MeasurementInputOptionVolatilityMember_FE55832E7239E16E1F514816BE51355A" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_MeasurementInputTypeDomain_A5DBA21C89CFF1976630481489419B78" xlink:to="loc_us-gaap_MeasurementInputOptionVolatilityMember_FE55832E7239E16E1F514816BE51355A" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_MeasurementInputExpectedDividendRateMember" xlink:label="loc_us-gaap_MeasurementInputExpectedDividendRateMember_2EAFC7DFF9EF4CD2A0B3481849CF1EC3" xlink:type="locator" />
    <link:definitionArc order="4" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_MeasurementInputTypeDomain_A5DBA21C89CFF1976630481489419B78" xlink:to="loc_us-gaap_MeasurementInputExpectedDividendRateMember_2EAFC7DFF9EF4CD2A0B3481849CF1EC3" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_MeasurementInputExpectedTermMember" xlink:label="loc_us-gaap_MeasurementInputExpectedTermMember_CDEEE2D813C6B893ADFE481FFD367603" xlink:type="locator" />
    <link:definitionArc order="5" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_MeasurementInputTypeDomain_A5DBA21C89CFF1976630481489419B78" xlink:to="loc_us-gaap_MeasurementInputExpectedTermMember_CDEEE2D813C6B893ADFE481FFD367603" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_SharePrice" xlink:label="loc_us-gaap_SharePrice_E5766B4E3AD8D577F94C4807C3A8AB48" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisValuationTechniquesLineItems_27AB5B6517579EAF99674807C3A844CA" xlink:to="loc_us-gaap_SharePrice_E5766B4E3AD8D577F94C4807C3A8AB48" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_DebtInstrumentMeasurementInput" xlink:label="loc_us-gaap_DebtInstrumentMeasurementInput_12306B56637E24CECE144814238DB893" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisValuationTechniquesLineItems_27AB5B6517579EAF99674807C3A844CA" xlink:to="loc_us-gaap_DebtInstrumentMeasurementInput_12306B56637E24CECE144814238DB893" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_WarrantsAndRightsOutstandingTerm" xlink:label="loc_us-gaap_WarrantsAndRightsOutstandingTerm_0F3DFBC69597230D0997481E82C59482" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisValuationTechniquesLineItems_27AB5B6517579EAF99674807C3A844CA" xlink:to="loc_us-gaap_WarrantsAndRightsOutstandingTerm_0F3DFBC69597230D0997481E82C59482" xlink:type="arc" />
    <link:loc xlink:href="anab-20180630.xsd#anab_FairValueAssumptionsWeightedAverageGrantDateFairValuePerShare" xlink:label="loc_anab_FairValueAssumptionsWeightedAverageGrantDateFairValuePerShare_4EDD6E3FCF4EE0AF8EB84807C3AAF97B" xlink:type="locator" />
    <link:definitionArc order="4" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisValuationTechniquesLineItems_27AB5B6517579EAF99674807C3A844CA" xlink:to="loc_anab_FairValueAssumptionsWeightedAverageGrantDateFairValuePerShare_4EDD6E3FCF4EE0AF8EB84807C3AAF97B" xlink:type="arc" />
  </link:definitionLink>
  <link:definitionLink xlink:role="http://www.anaptysbio.com/role/FairValueMeasurementsAndAvailableForSaleInvestmentsFairValueOfOtherFinancialInstrumentsDetails" xlink:type="extended">
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_FairValueBalanceSheetGroupingFinancialStatementCaptionsLineItems" xlink:label="loc_us-gaap_FairValueBalanceSheetGroupingFinancialStatementCaptionsLineItems_E2991090753D1B523886480643C2EF8F" xlink:type="locator" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_FairValueByBalanceSheetGroupingTable" xlink:label="loc_us-gaap_FairValueByBalanceSheetGroupingTable_0C97FFB82376E6E75B38480643C0F623" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_FairValueBalanceSheetGroupingFinancialStatementCaptionsLineItems_E2991090753D1B523886480643C2EF8F" xlink:to="loc_us-gaap_FairValueByBalanceSheetGroupingTable_0C97FFB82376E6E75B38480643C0F623" xlink:type="arc" xbrldt:closed="true" xbrldt:contextElement="segment" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_FairValueByMeasurementBasisAxis" xlink:label="loc_us-gaap_FairValueByMeasurementBasisAxis_D18F4135143B72E8E748480643C1C7B3" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_FairValueByBalanceSheetGroupingTable_0C97FFB82376E6E75B38480643C0F623" xlink:to="loc_us-gaap_FairValueByMeasurementBasisAxis_D18F4135143B72E8E748480643C1C7B3" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_PortionAtFairValueFairValueDisclosureMember" xlink:label="loc_us-gaap_PortionAtFairValueFairValueDisclosureMember_6480A104458A33386CCC480643C1DABC_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_FairValueByMeasurementBasisAxis_D18F4135143B72E8E748480643C1C7B3" xlink:to="loc_us-gaap_PortionAtFairValueFairValueDisclosureMember_6480A104458A33386CCC480643C1DABC_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_FairValueDisclosureItemAmountsDomain" xlink:label="loc_us-gaap_FairValueDisclosureItemAmountsDomain_8739E774D142FAE95766480643C1CB86" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_FairValueByMeasurementBasisAxis_D18F4135143B72E8E748480643C1C7B3" xlink:to="loc_us-gaap_FairValueDisclosureItemAmountsDomain_8739E774D142FAE95766480643C1CB86" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_PortionAtFairValueFairValueDisclosureMember" xlink:label="loc_us-gaap_PortionAtFairValueFairValueDisclosureMember_6480A104458A33386CCC480643C1DABC" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueDisclosureItemAmountsDomain_8739E774D142FAE95766480643C1CB86" xlink:to="loc_us-gaap_PortionAtFairValueFairValueDisclosureMember_6480A104458A33386CCC480643C1DABC" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_CarryingReportedAmountFairValueDisclosureMember" xlink:label="loc_us-gaap_CarryingReportedAmountFairValueDisclosureMember_FB5D7D9755AC10128DAB480643C2156C" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueDisclosureItemAmountsDomain_8739E774D142FAE95766480643C1CB86" xlink:to="loc_us-gaap_CarryingReportedAmountFairValueDisclosureMember_FB5D7D9755AC10128DAB480643C2156C" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_EstimateOfFairValueFairValueDisclosureMember" xlink:label="loc_us-gaap_EstimateOfFairValueFairValueDisclosureMember_3077A560C3D86F38FB03480643C25BFD" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueDisclosureItemAmountsDomain_8739E774D142FAE95766480643C1CB86" xlink:to="loc_us-gaap_EstimateOfFairValueFairValueDisclosureMember_3077A560C3D86F38FB03480643C25BFD" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_NotesPayableFairValueDisclosure" xlink:label="loc_us-gaap_NotesPayableFairValueDisclosure_90C8D025CF4E57FA99E3480643C210C6" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueBalanceSheetGroupingFinancialStatementCaptionsLineItems_E2991090753D1B523886480643C2EF8F" xlink:to="loc_us-gaap_NotesPayableFairValueDisclosure_90C8D025CF4E57FA99E3480643C210C6" xlink:type="arc" />
  </link:definitionLink>
  <link:definitionLink xlink:role="http://www.anaptysbio.com/role/FairValueMeasurementsAndAvailableForSaleInvestmentsLiabilitiesWithSignificantUnobservableInputsDetails" xlink:type="extended">
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_FairValueLiabilitiesMeasuredOnRecurringBasisUnobservableInputReconciliationLineItems" xlink:label="loc_us-gaap_FairValueLiabilitiesMeasuredOnRecurringBasisUnobservableInputReconciliationLineItems_617B7F425A8CC8684C84480642BDFB9F" xlink:type="locator" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_FairValueLiabilitiesMeasuredOnRecurringBasisUnobservableInputReconciliationTable" xlink:label="loc_us-gaap_FairValueLiabilitiesMeasuredOnRecurringBasisUnobservableInputReconciliationTable_7CCBB21CD64EA847DAD5480642BA9B52" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_FairValueLiabilitiesMeasuredOnRecurringBasisUnobservableInputReconciliationLineItems_617B7F425A8CC8684C84480642BDFB9F" xlink:to="loc_us-gaap_FairValueLiabilitiesMeasuredOnRecurringBasisUnobservableInputReconciliationTable_7CCBB21CD64EA847DAD5480642BA9B52" xlink:type="arc" xbrldt:closed="true" xbrldt:contextElement="segment" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_StatementClassOfStockAxis" xlink:label="loc_us-gaap_StatementClassOfStockAxis_3331DFC236C167B07578480642BA6ED0" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_FairValueLiabilitiesMeasuredOnRecurringBasisUnobservableInputReconciliationTable_7CCBB21CD64EA847DAD5480642BA9B52" xlink:to="loc_us-gaap_StatementClassOfStockAxis_3331DFC236C167B07578480642BA6ED0" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_ClassOfStockDomain" xlink:label="loc_us-gaap_ClassOfStockDomain_3EFFEEF10702B4E67602480642BA955A_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_StatementClassOfStockAxis_3331DFC236C167B07578480642BA6ED0" xlink:to="loc_us-gaap_ClassOfStockDomain_3EFFEEF10702B4E67602480642BA955A_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_ClassOfStockDomain" xlink:label="loc_us-gaap_ClassOfStockDomain_3EFFEEF10702B4E67602480642BA955A" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_StatementClassOfStockAxis_3331DFC236C167B07578480642BA6ED0" xlink:to="loc_us-gaap_ClassOfStockDomain_3EFFEEF10702B4E67602480642BA955A" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_SeriesCPreferredStockMember" xlink:label="loc_us-gaap_SeriesCPreferredStockMember_EBDF3B480136D5EBFE5B480642BBE90E" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockDomain_3EFFEEF10702B4E67602480642BA955A" xlink:to="loc_us-gaap_SeriesCPreferredStockMember_EBDF3B480136D5EBFE5B480642BBE90E" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_FairValueByLiabilityClassAxis" xlink:label="loc_us-gaap_FairValueByLiabilityClassAxis_09049685B28C0FB0F6A9480642BBB77E" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_FairValueLiabilitiesMeasuredOnRecurringBasisUnobservableInputReconciliationTable_7CCBB21CD64EA847DAD5480642BA9B52" xlink:to="loc_us-gaap_FairValueByLiabilityClassAxis_09049685B28C0FB0F6A9480642BBB77E" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_FairValueLiabilitiesMeasuredOnRecurringBasisUnobservableInputReconciliationByLiabilityClassDomain" xlink:label="loc_us-gaap_FairValueLiabilitiesMeasuredOnRecurringBasisUnobservableInputReconciliationByLiabilityClassDomain_D56160E8B4CAEEC765D3480642BBB2B3_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_FairValueByLiabilityClassAxis_09049685B28C0FB0F6A9480642BBB77E" xlink:to="loc_us-gaap_FairValueLiabilitiesMeasuredOnRecurringBasisUnobservableInputReconciliationByLiabilityClassDomain_D56160E8B4CAEEC765D3480642BBB2B3_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_FairValueLiabilitiesMeasuredOnRecurringBasisUnobservableInputReconciliationByLiabilityClassDomain" xlink:label="loc_us-gaap_FairValueLiabilitiesMeasuredOnRecurringBasisUnobservableInputReconciliationByLiabilityClassDomain_D56160E8B4CAEEC765D3480642BBB2B3" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_FairValueByLiabilityClassAxis_09049685B28C0FB0F6A9480642BBB77E" xlink:to="loc_us-gaap_FairValueLiabilitiesMeasuredOnRecurringBasisUnobservableInputReconciliationByLiabilityClassDomain_D56160E8B4CAEEC765D3480642BBB2B3" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_DerivativeFinancialInstrumentsLiabilitiesMember" xlink:label="loc_us-gaap_DerivativeFinancialInstrumentsLiabilitiesMember_B56DB5F2C03CBDAC5767480642BBCCD6" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueLiabilitiesMeasuredOnRecurringBasisUnobservableInputReconciliationByLiabilityClassDomain_D56160E8B4CAEEC765D3480642BBB2B3" xlink:to="loc_us-gaap_DerivativeFinancialInstrumentsLiabilitiesMember_B56DB5F2C03CBDAC5767480642BBCCD6" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_FairValueByMeasurementFrequencyAxis" xlink:label="loc_us-gaap_FairValueByMeasurementFrequencyAxis_EB87E7A46324830E5D89480642BC9C9B" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_FairValueLiabilitiesMeasuredOnRecurringBasisUnobservableInputReconciliationTable_7CCBB21CD64EA847DAD5480642BA9B52" xlink:to="loc_us-gaap_FairValueByMeasurementFrequencyAxis_EB87E7A46324830E5D89480642BC9C9B" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_FairValueMeasurementFrequencyDomain" xlink:label="loc_us-gaap_FairValueMeasurementFrequencyDomain_22B08CC442F834357656480642BC2591_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_FairValueByMeasurementFrequencyAxis_EB87E7A46324830E5D89480642BC9C9B" xlink:to="loc_us-gaap_FairValueMeasurementFrequencyDomain_22B08CC442F834357656480642BC2591_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_FairValueMeasurementFrequencyDomain" xlink:label="loc_us-gaap_FairValueMeasurementFrequencyDomain_22B08CC442F834357656480642BC2591" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_FairValueByMeasurementFrequencyAxis_EB87E7A46324830E5D89480642BC9C9B" xlink:to="loc_us-gaap_FairValueMeasurementFrequencyDomain_22B08CC442F834357656480642BC2591" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_FairValueMeasurementsRecurringMember" xlink:label="loc_us-gaap_FairValueMeasurementsRecurringMember_AB4C06E532DEE7A83632480642BC4812" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueMeasurementFrequencyDomain_22B08CC442F834357656480642BC2591" xlink:to="loc_us-gaap_FairValueMeasurementsRecurringMember_AB4C06E532DEE7A83632480642BC4812" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_FairValueLiabilitiesMeasuredOnRecurringBasisUnobservableInputReconciliationCalculationRollForward" xlink:label="loc_us-gaap_FairValueLiabilitiesMeasuredOnRecurringBasisUnobservableInputReconciliationCalculationRollForward_344F72333F9AFA63CB30480642BD5A23" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueLiabilitiesMeasuredOnRecurringBasisUnobservableInputReconciliationLineItems_617B7F425A8CC8684C84480642BDFB9F" xlink:to="loc_us-gaap_FairValueLiabilitiesMeasuredOnRecurringBasisUnobservableInputReconciliationCalculationRollForward_344F72333F9AFA63CB30480642BD5A23" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationsRecurringBasisLiabilityValue" xlink:label="loc_us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationsRecurringBasisLiabilityValue_EE19D3EDADAE85A0F9F3480642BEF496" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueLiabilitiesMeasuredOnRecurringBasisUnobservableInputReconciliationCalculationRollForward_344F72333F9AFA63CB30480642BD5A23" xlink:to="loc_us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationsRecurringBasisLiabilityValue_EE19D3EDADAE85A0F9F3480642BEF496" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisLiabilityGainLossIncludedInEarnings" xlink:label="loc_us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisLiabilityGainLossIncludedInEarnings_008BB94D0A1C78F40A1A480642BFE315" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueLiabilitiesMeasuredOnRecurringBasisUnobservableInputReconciliationCalculationRollForward_344F72333F9AFA63CB30480642BD5A23" xlink:to="loc_us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisLiabilityGainLossIncludedInEarnings_008BB94D0A1C78F40A1A480642BFE315" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationLiabilityTransfersOutOfLevel3" xlink:label="loc_us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationLiabilityTransfersOutOfLevel3_D3BE94B03B70259D9549480642BF757A" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueLiabilitiesMeasuredOnRecurringBasisUnobservableInputReconciliationCalculationRollForward_344F72333F9AFA63CB30480642BD5A23" xlink:to="loc_us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationLiabilityTransfersOutOfLevel3_D3BE94B03B70259D9549480642BF757A" xlink:type="arc" />
  </link:definitionLink>
  <link:definitionLink xlink:role="http://www.anaptysbio.com/role/FairValueMeasurementsAndAvailableForSaleInvestmentsTables" xlink:type="extended" />
  <link:definitionLink xlink:role="http://www.anaptysbio.com/role/NotesPayable" xlink:type="extended" />
  <link:definitionLink xlink:role="http://www.anaptysbio.com/role/NotesPayableDetails" xlink:type="extended">
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_DebtInstrumentLineItems" xlink:label="loc_us-gaap_DebtInstrumentLineItems_2343CEC69D9EE2F4BB8F4807C3F5FF97" xlink:type="locator" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_DebtInstrumentTable" xlink:label="loc_us-gaap_DebtInstrumentTable_1436BB381717F5C2B9D24807C3ED0CFE" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_DebtInstrumentLineItems_2343CEC69D9EE2F4BB8F4807C3F5FF97" xlink:to="loc_us-gaap_DebtInstrumentTable_1436BB381717F5C2B9D24807C3ED0CFE" xlink:type="arc" xbrldt:closed="true" xbrldt:contextElement="segment" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_LongtermDebtTypeAxis" xlink:label="loc_us-gaap_LongtermDebtTypeAxis_313FACFF62500E69EF544807C3ED3555" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DebtInstrumentTable_1436BB381717F5C2B9D24807C3ED0CFE" xlink:to="loc_us-gaap_LongtermDebtTypeAxis_313FACFF62500E69EF544807C3ED3555" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_LongtermDebtTypeDomain" xlink:label="loc_us-gaap_LongtermDebtTypeDomain_559B7E0FB226CEE5A1D64807C3EE9D60_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_LongtermDebtTypeAxis_313FACFF62500E69EF544807C3ED3555" xlink:to="loc_us-gaap_LongtermDebtTypeDomain_559B7E0FB226CEE5A1D64807C3EE9D60_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_LongtermDebtTypeDomain" xlink:label="loc_us-gaap_LongtermDebtTypeDomain_559B7E0FB226CEE5A1D64807C3EE9D60" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_LongtermDebtTypeAxis_313FACFF62500E69EF544807C3ED3555" xlink:to="loc_us-gaap_LongtermDebtTypeDomain_559B7E0FB226CEE5A1D64807C3EE9D60" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_NotesPayableToBanksMember" xlink:label="loc_us-gaap_NotesPayableToBanksMember_AF9C0A3399DA0B9600814807C3EEE5D8" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LongtermDebtTypeDomain_559B7E0FB226CEE5A1D64807C3EE9D60" xlink:to="loc_us-gaap_NotesPayableToBanksMember_AF9C0A3399DA0B9600814807C3EEE5D8" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_DebtInstrumentAxis" xlink:label="loc_us-gaap_DebtInstrumentAxis_11A0762E74ECF419356D4807C3EE3934" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DebtInstrumentTable_1436BB381717F5C2B9D24807C3ED0CFE" xlink:to="loc_us-gaap_DebtInstrumentAxis_11A0762E74ECF419356D4807C3EE3934" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_DebtInstrumentNameDomain" xlink:label="loc_us-gaap_DebtInstrumentNameDomain_4FD291D1B26B528D38814807C3EF521F_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_DebtInstrumentAxis_11A0762E74ECF419356D4807C3EE3934" xlink:to="loc_us-gaap_DebtInstrumentNameDomain_4FD291D1B26B528D38814807C3EF521F_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_DebtInstrumentNameDomain" xlink:label="loc_us-gaap_DebtInstrumentNameDomain_4FD291D1B26B528D38814807C3EF521F" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_DebtInstrumentAxis_11A0762E74ECF419356D4807C3EE3934" xlink:to="loc_us-gaap_DebtInstrumentNameDomain_4FD291D1B26B528D38814807C3EF521F" xlink:type="arc" />
    <link:loc xlink:href="anab-20180630.xsd#anab_LoanAndSecurityAgreementMember" xlink:label="loc_anab_LoanAndSecurityAgreementMember_F01FEDCB0ACF543B02514807C3EF3CF3" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_4FD291D1B26B528D38814807C3EF521F" xlink:to="loc_anab_LoanAndSecurityAgreementMember_F01FEDCB0ACF543B02514807C3EF3CF3" xlink:type="arc" />
    <link:loc xlink:href="anab-20180630.xsd#anab_TermALoansMember" xlink:label="loc_anab_TermALoansMember_1730807D5F74F344754C4807C3F0366C" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_anab_LoanAndSecurityAgreementMember_F01FEDCB0ACF543B02514807C3EF3CF3" xlink:to="loc_anab_TermALoansMember_1730807D5F74F344754C4807C3F0366C" xlink:type="arc" />
    <link:loc xlink:href="anab-20180630.xsd#anab_TermBLoansAndTermCLoansMember" xlink:label="loc_anab_TermBLoansAndTermCLoansMember_F296548102F4A7FA7E404807C3F0DA98" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_anab_LoanAndSecurityAgreementMember_F01FEDCB0ACF543B02514807C3EF3CF3" xlink:to="loc_anab_TermBLoansAndTermCLoansMember_F296548102F4A7FA7E404807C3F0DA98" xlink:type="arc" />
    <link:loc xlink:href="anab-20180630.xsd#anab_TermBLoansMember" xlink:label="loc_anab_TermBLoansMember_5C6F5BAF7F50B7D0C0404807C3F09F6A" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_anab_TermBLoansAndTermCLoansMember_F296548102F4A7FA7E404807C3F0DA98" xlink:to="loc_anab_TermBLoansMember_5C6F5BAF7F50B7D0C0404807C3F09F6A" xlink:type="arc" />
    <link:loc xlink:href="anab-20180630.xsd#anab_TermCLoansMember" xlink:label="loc_anab_TermCLoansMember_E88B830969F7DC7E2D4F4807C3F1824B" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_anab_TermBLoansAndTermCLoansMember_F296548102F4A7FA7E404807C3F0DA98" xlink:to="loc_anab_TermCLoansMember_E88B830969F7DC7E2D4F4807C3F1824B" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_StatementClassOfStockAxis" xlink:label="loc_us-gaap_StatementClassOfStockAxis_F313D18332B115DF69394807C3F1AB8D" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DebtInstrumentTable_1436BB381717F5C2B9D24807C3ED0CFE" xlink:to="loc_us-gaap_StatementClassOfStockAxis_F313D18332B115DF69394807C3F1AB8D" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_ClassOfStockDomain" xlink:label="loc_us-gaap_ClassOfStockDomain_4DC32C07CAC8D09AEFB54807C3F140DD_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_StatementClassOfStockAxis_F313D18332B115DF69394807C3F1AB8D" xlink:to="loc_us-gaap_ClassOfStockDomain_4DC32C07CAC8D09AEFB54807C3F140DD_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_ClassOfStockDomain" xlink:label="loc_us-gaap_ClassOfStockDomain_4DC32C07CAC8D09AEFB54807C3F140DD" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_StatementClassOfStockAxis_F313D18332B115DF69394807C3F1AB8D" xlink:to="loc_us-gaap_ClassOfStockDomain_4DC32C07CAC8D09AEFB54807C3F140DD" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_SeriesCPreferredStockMember" xlink:label="loc_us-gaap_SeriesCPreferredStockMember_9B97E84A78B5680B75B34807C3F21AF0" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockDomain_4DC32C07CAC8D09AEFB54807C3F140DD" xlink:to="loc_us-gaap_SeriesCPreferredStockMember_9B97E84A78B5680B75B34807C3F21AF0" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_ClassOfWarrantOrRightAxis" xlink:label="loc_us-gaap_ClassOfWarrantOrRightAxis_7C4CD0EA6BCF4841C2744807C3F20AFC" xlink:type="locator" />
    <link:definitionArc order="4" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DebtInstrumentTable_1436BB381717F5C2B9D24807C3ED0CFE" xlink:to="loc_us-gaap_ClassOfWarrantOrRightAxis_7C4CD0EA6BCF4841C2744807C3F20AFC" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_ClassOfWarrantOrRightDomain" xlink:label="loc_us-gaap_ClassOfWarrantOrRightDomain_50589C1A266BF893EAA04807C3F23325_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_ClassOfWarrantOrRightAxis_7C4CD0EA6BCF4841C2744807C3F20AFC" xlink:to="loc_us-gaap_ClassOfWarrantOrRightDomain_50589C1A266BF893EAA04807C3F23325_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_ClassOfWarrantOrRightDomain" xlink:label="loc_us-gaap_ClassOfWarrantOrRightDomain_50589C1A266BF893EAA04807C3F23325" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_ClassOfWarrantOrRightAxis_7C4CD0EA6BCF4841C2744807C3F20AFC" xlink:to="loc_us-gaap_ClassOfWarrantOrRightDomain_50589C1A266BF893EAA04807C3F23325" xlink:type="arc" />
    <link:loc xlink:href="anab-20180630.xsd#anab_TermALoanWarrantsMember" xlink:label="loc_anab_TermALoanWarrantsMember_9CB4D1FA22F7729B6C184807C3F3F3FC" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfWarrantOrRightDomain_50589C1A266BF893EAA04807C3F23325" xlink:to="loc_anab_TermALoanWarrantsMember_9CB4D1FA22F7729B6C184807C3F3F3FC" xlink:type="arc" />
    <link:loc xlink:href="anab-20180630.xsd#anab_TermBAndCLoansWarrantsMember" xlink:label="loc_anab_TermBAndCLoansWarrantsMember_C26076146FCC010EB1FC4807C3F3637D" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfWarrantOrRightDomain_50589C1A266BF893EAA04807C3F23325" xlink:to="loc_anab_TermBAndCLoansWarrantsMember_C26076146FCC010EB1FC4807C3F3637D" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_DerivativeInstrumentRiskAxis" xlink:label="loc_us-gaap_DerivativeInstrumentRiskAxis_FF0CD8746A41327912144807C3F31167" xlink:type="locator" />
    <link:definitionArc order="5" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DebtInstrumentTable_1436BB381717F5C2B9D24807C3ED0CFE" xlink:to="loc_us-gaap_DerivativeInstrumentRiskAxis_FF0CD8746A41327912144807C3F31167" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_DerivativeContractTypeDomain" xlink:label="loc_us-gaap_DerivativeContractTypeDomain_FD296C92502296A8E5604807C3F3F214_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_DerivativeInstrumentRiskAxis_FF0CD8746A41327912144807C3F31167" xlink:to="loc_us-gaap_DerivativeContractTypeDomain_FD296C92502296A8E5604807C3F3F214_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_DerivativeContractTypeDomain" xlink:label="loc_us-gaap_DerivativeContractTypeDomain_FD296C92502296A8E5604807C3F3F214" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_DerivativeInstrumentRiskAxis_FF0CD8746A41327912144807C3F31167" xlink:to="loc_us-gaap_DerivativeContractTypeDomain_FD296C92502296A8E5604807C3F3F214" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_WarrantMember" xlink:label="loc_us-gaap_WarrantMember_12E89D3D5B31F82C40D74807C3F409DA" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativeContractTypeDomain_FD296C92502296A8E5604807C3F3F214" xlink:to="loc_us-gaap_WarrantMember_12E89D3D5B31F82C40D74807C3F409DA" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_VariableRateAxis" xlink:label="loc_us-gaap_VariableRateAxis_FBAF64BD01300B80832B4807C3F4CEA7" xlink:type="locator" />
    <link:definitionArc order="6" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DebtInstrumentTable_1436BB381717F5C2B9D24807C3ED0CFE" xlink:to="loc_us-gaap_VariableRateAxis_FBAF64BD01300B80832B4807C3F4CEA7" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_VariableRateDomain" xlink:label="loc_us-gaap_VariableRateDomain_49E073B7D4955E1ED0624807C3F59041_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_VariableRateAxis_FBAF64BD01300B80832B4807C3F4CEA7" xlink:to="loc_us-gaap_VariableRateDomain_49E073B7D4955E1ED0624807C3F59041_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_VariableRateDomain" xlink:label="loc_us-gaap_VariableRateDomain_49E073B7D4955E1ED0624807C3F59041" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_VariableRateAxis_FBAF64BD01300B80832B4807C3F4CEA7" xlink:to="loc_us-gaap_VariableRateDomain_49E073B7D4955E1ED0624807C3F59041" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_LondonInterbankOfferedRateLIBORMember" xlink:label="loc_us-gaap_LondonInterbankOfferedRateLIBORMember_172D1E8757F776CF1A434807C3F58E72" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_VariableRateDomain_49E073B7D4955E1ED0624807C3F59041" xlink:to="loc_us-gaap_LondonInterbankOfferedRateLIBORMember_172D1E8757F776CF1A434807C3F58E72" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_MeasurementInputTypeAxis" xlink:label="loc_us-gaap_MeasurementInputTypeAxis_C855CD1333D3006AE08C480A14CE7EEA" xlink:type="locator" />
    <link:definitionArc order="7" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DebtInstrumentTable_1436BB381717F5C2B9D24807C3ED0CFE" xlink:to="loc_us-gaap_MeasurementInputTypeAxis_C855CD1333D3006AE08C480A14CE7EEA" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_MeasurementInputTypeDomain" xlink:label="loc_us-gaap_MeasurementInputTypeDomain_BB09285FF7480C88258E480A796DC0D4_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_MeasurementInputTypeAxis_C855CD1333D3006AE08C480A14CE7EEA" xlink:to="loc_us-gaap_MeasurementInputTypeDomain_BB09285FF7480C88258E480A796DC0D4_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_MeasurementInputTypeDomain" xlink:label="loc_us-gaap_MeasurementInputTypeDomain_BB09285FF7480C88258E480A796DC0D4" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_MeasurementInputTypeAxis_C855CD1333D3006AE08C480A14CE7EEA" xlink:to="loc_us-gaap_MeasurementInputTypeDomain_BB09285FF7480C88258E480A796DC0D4" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_MeasurementInputPriceVolatilityMember" xlink:label="loc_us-gaap_MeasurementInputPriceVolatilityMember_30430DDDA7211E1AF643480B9A909D14" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_MeasurementInputTypeDomain_BB09285FF7480C88258E480A796DC0D4" xlink:to="loc_us-gaap_MeasurementInputPriceVolatilityMember_30430DDDA7211E1AF643480B9A909D14" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_MeasurementInputExpectedTermMember" xlink:label="loc_us-gaap_MeasurementInputExpectedTermMember_660868B7720D10C826B9480FE27695F7" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_MeasurementInputTypeDomain_BB09285FF7480C88258E480A796DC0D4" xlink:to="loc_us-gaap_MeasurementInputExpectedTermMember_660868B7720D10C826B9480FE27695F7" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_MeasurementInputRiskFreeInterestRateMember" xlink:label="loc_us-gaap_MeasurementInputRiskFreeInterestRateMember_E6A84A6FDFE08CDBB41848126534F4C0" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_MeasurementInputTypeDomain_BB09285FF7480C88258E480A796DC0D4" xlink:to="loc_us-gaap_MeasurementInputRiskFreeInterestRateMember_E6A84A6FDFE08CDBB41848126534F4C0" xlink:type="arc" />
    <link:loc xlink:href="anab-20180630.xsd#anab_DebtInstrumentMaximumBorrowingCapacity" xlink:label="loc_anab_DebtInstrumentMaximumBorrowingCapacity_519DBD6ED6F8BD031AFD4807C3F584FE" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_2343CEC69D9EE2F4BB8F4807C3F5FF97" xlink:to="loc_anab_DebtInstrumentMaximumBorrowingCapacity_519DBD6ED6F8BD031AFD4807C3F584FE" xlink:type="arc" />
    <link:loc xlink:href="anab-20180630.xsd#anab_DebtInstrumentNumberOfLoanInstallments" xlink:label="loc_anab_DebtInstrumentNumberOfLoanInstallments_79383B514D6BAFA0EA444807C3F686F0" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_2343CEC69D9EE2F4BB8F4807C3F5FF97" xlink:to="loc_anab_DebtInstrumentNumberOfLoanInstallments_79383B514D6BAFA0EA444807C3F686F0" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_DebtInstrumentFaceAmount" xlink:label="loc_us-gaap_DebtInstrumentFaceAmount_31D5E1E0B0B8522E864A4807C3F65E4A" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_2343CEC69D9EE2F4BB8F4807C3F5FF97" xlink:to="loc_us-gaap_DebtInstrumentFaceAmount_31D5E1E0B0B8522E864A4807C3F65E4A" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_ProceedsFromNotesPayable" xlink:label="loc_us-gaap_ProceedsFromNotesPayable_975F669C709FC08CB7734807C3F76AE8" xlink:type="locator" />
    <link:definitionArc order="4" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_2343CEC69D9EE2F4BB8F4807C3F5FF97" xlink:to="loc_us-gaap_ProceedsFromNotesPayable_975F669C709FC08CB7734807C3F76AE8" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_DebtInstrumentInterestRateStatedPercentage" xlink:label="loc_us-gaap_DebtInstrumentInterestRateStatedPercentage_3D6F14BBD567206810204807C3F77EAD" xlink:type="locator" />
    <link:definitionArc order="5" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_2343CEC69D9EE2F4BB8F4807C3F5FF97" xlink:to="loc_us-gaap_DebtInstrumentInterestRateStatedPercentage_3D6F14BBD567206810204807C3F77EAD" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_ClassOfWarrantOrRightNumberOfSecuritiesCalledByWarrantsOrRights" xlink:label="loc_us-gaap_ClassOfWarrantOrRightNumberOfSecuritiesCalledByWarrantsOrRights_C06704D05926C618F0E04807C3F7F86C" xlink:type="locator" />
    <link:definitionArc order="6" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_2343CEC69D9EE2F4BB8F4807C3F5FF97" xlink:to="loc_us-gaap_ClassOfWarrantOrRightNumberOfSecuritiesCalledByWarrantsOrRights_C06704D05926C618F0E04807C3F7F86C" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_ClassOfWarrantOrRightExercisePriceOfWarrantsOrRights1" xlink:label="loc_us-gaap_ClassOfWarrantOrRightExercisePriceOfWarrantsOrRights1_160226CFB21FF88275E84807C3F7B34D" xlink:type="locator" />
    <link:definitionArc order="7" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_2343CEC69D9EE2F4BB8F4807C3F5FF97" xlink:to="loc_us-gaap_ClassOfWarrantOrRightExercisePriceOfWarrantsOrRights1_160226CFB21FF88275E84807C3F7B34D" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_DerivativeLiabilities" xlink:label="loc_us-gaap_DerivativeLiabilities_D79D7BD4695E24E3A7AC4807C3F755FE" xlink:type="locator" />
    <link:definitionArc order="8" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_2343CEC69D9EE2F4BB8F4807C3F5FF97" xlink:to="loc_us-gaap_DerivativeLiabilities_D79D7BD4695E24E3A7AC4807C3F755FE" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_DebtInstrumentMeasurementInput" xlink:label="loc_us-gaap_DebtInstrumentMeasurementInput_C2D35011568995D5D9B2480DFF344D66" xlink:type="locator" />
    <link:definitionArc order="9" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_2343CEC69D9EE2F4BB8F4807C3F5FF97" xlink:to="loc_us-gaap_DebtInstrumentMeasurementInput_C2D35011568995D5D9B2480DFF344D66" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_WarrantsAndRightsOutstandingTerm" xlink:label="loc_us-gaap_WarrantsAndRightsOutstandingTerm_054881FF5D95C774CD7C48111E921A27" xlink:type="locator" />
    <link:definitionArc order="10" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_2343CEC69D9EE2F4BB8F4807C3F5FF97" xlink:to="loc_us-gaap_WarrantsAndRightsOutstandingTerm_054881FF5D95C774CD7C48111E921A27" xlink:type="arc" />
    <link:loc xlink:href="anab-20180630.xsd#anab_DebtInstrumentPeriodicPaymentNumberOfPrincipalAndInterestPayments" xlink:label="loc_anab_DebtInstrumentPeriodicPaymentNumberOfPrincipalAndInterestPayments_F1151BFBCEB9D28B5C9C4807C3F9785B" xlink:type="locator" />
    <link:definitionArc order="11" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_2343CEC69D9EE2F4BB8F4807C3F5FF97" xlink:to="loc_anab_DebtInstrumentPeriodicPaymentNumberOfPrincipalAndInterestPayments_F1151BFBCEB9D28B5C9C4807C3F9785B" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_DebtInstrumentBasisSpreadOnVariableRate1" xlink:label="loc_us-gaap_DebtInstrumentBasisSpreadOnVariableRate1_7A4D30257408DFB6E5DB4807C3F91FA8" xlink:type="locator" />
    <link:definitionArc order="12" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_2343CEC69D9EE2F4BB8F4807C3F5FF97" xlink:to="loc_us-gaap_DebtInstrumentBasisSpreadOnVariableRate1_7A4D30257408DFB6E5DB4807C3F91FA8" xlink:type="arc" />
    <link:loc xlink:href="anab-20180630.xsd#anab_DebtInstrumentInterestRateAtEndOfPeriod" xlink:label="loc_anab_DebtInstrumentInterestRateAtEndOfPeriod_4B6FDC8CFC5755D9FD474807C3FA4038" xlink:type="locator" />
    <link:definitionArc order="13" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_2343CEC69D9EE2F4BB8F4807C3F5FF97" xlink:to="loc_anab_DebtInstrumentInterestRateAtEndOfPeriod_4B6FDC8CFC5755D9FD474807C3FA4038" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_DebtInstrumentPeriodicPaymentTermsBalloonPaymentToBePaid" xlink:label="loc_us-gaap_DebtInstrumentPeriodicPaymentTermsBalloonPaymentToBePaid_FD91147CFD2E081477634807C3FA5ED4" xlink:type="locator" />
    <link:definitionArc order="14" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_2343CEC69D9EE2F4BB8F4807C3F5FF97" xlink:to="loc_us-gaap_DebtInstrumentPeriodicPaymentTermsBalloonPaymentToBePaid_FD91147CFD2E081477634807C3FA5ED4" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_NotesPayable" xlink:label="loc_us-gaap_NotesPayable_C117960F72FCEACAC26E4807C3FB9BDA" xlink:type="locator" />
    <link:definitionArc order="15" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_2343CEC69D9EE2F4BB8F4807C3F5FF97" xlink:to="loc_us-gaap_NotesPayable_C117960F72FCEACAC26E4807C3FB9BDA" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_DebtInstrumentUnamortizedDiscountPremiumAndDebtIssuanceCostsNet" xlink:label="loc_us-gaap_DebtInstrumentUnamortizedDiscountPremiumAndDebtIssuanceCostsNet_056502C35BE578E676364807C3FB4218" xlink:type="locator" />
    <link:definitionArc order="16" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_2343CEC69D9EE2F4BB8F4807C3F5FF97" xlink:to="loc_us-gaap_DebtInstrumentUnamortizedDiscountPremiumAndDebtIssuanceCostsNet_056502C35BE578E676364807C3FB4218" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_NotesPayableCurrent" xlink:label="loc_us-gaap_NotesPayableCurrent_8720EBB0127414C3BF044807C3FBF3EB" xlink:type="locator" />
    <link:definitionArc order="17" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_2343CEC69D9EE2F4BB8F4807C3F5FF97" xlink:to="loc_us-gaap_NotesPayableCurrent_8720EBB0127414C3BF044807C3FBF3EB" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_DebtInstrumentInterestRateEffectivePercentage" xlink:label="loc_us-gaap_DebtInstrumentInterestRateEffectivePercentage_6F85E8CC19C6C7EC79824807C3FB4CCC" xlink:type="locator" />
    <link:definitionArc order="18" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_2343CEC69D9EE2F4BB8F4807C3F5FF97" xlink:to="loc_us-gaap_DebtInstrumentInterestRateEffectivePercentage_6F85E8CC19C6C7EC79824807C3FB4CCC" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_LongTermDebtByMaturityAbstract" xlink:label="loc_us-gaap_LongTermDebtByMaturityAbstract_7226D81766771DC0691F4807C3FCFC1B" xlink:type="locator" />
    <link:definitionArc order="19" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_2343CEC69D9EE2F4BB8F4807C3F5FF97" xlink:to="loc_us-gaap_LongTermDebtByMaturityAbstract_7226D81766771DC0691F4807C3FCFC1B" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_LongTermDebtMaturitiesRepaymentsOfPrincipalRemainderOfFiscalYear" xlink:label="loc_us-gaap_LongTermDebtMaturitiesRepaymentsOfPrincipalRemainderOfFiscalYear_4DB6C189EC777CC817744807C3FCE8ED" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LongTermDebtByMaturityAbstract_7226D81766771DC0691F4807C3FCFC1B" xlink:to="loc_us-gaap_LongTermDebtMaturitiesRepaymentsOfPrincipalRemainderOfFiscalYear_4DB6C189EC777CC817744807C3FCE8ED" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_LongTermDebtMaturitiesRepaymentsOfPrincipalInYearTwo" xlink:label="loc_us-gaap_LongTermDebtMaturitiesRepaymentsOfPrincipalInYearTwo_C66755B63119072F59D34807C3FC1D40" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LongTermDebtByMaturityAbstract_7226D81766771DC0691F4807C3FCFC1B" xlink:to="loc_us-gaap_LongTermDebtMaturitiesRepaymentsOfPrincipalInYearTwo_C66755B63119072F59D34807C3FC1D40" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_LongTermDebtMaturitiesRepaymentsOfPrincipalInYearThree" xlink:label="loc_us-gaap_LongTermDebtMaturitiesRepaymentsOfPrincipalInYearThree_206C0576113088234F354807C3FC8AC7" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LongTermDebtByMaturityAbstract_7226D81766771DC0691F4807C3FCFC1B" xlink:to="loc_us-gaap_LongTermDebtMaturitiesRepaymentsOfPrincipalInYearThree_206C0576113088234F354807C3FC8AC7" xlink:type="arc" />
  </link:definitionLink>
  <link:definitionLink xlink:role="http://www.anaptysbio.com/role/StockholdersEquity" xlink:type="extended" />
  <link:definitionLink xlink:role="http://www.anaptysbio.com/role/StockholdersEquityAdditionalInformationDetails" xlink:type="extended">
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_ClassOfStockLineItems" xlink:label="loc_us-gaap_ClassOfStockLineItems_AABABB7B91B6B54A2C5A4806430914BB" xlink:type="locator" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_ScheduleOfStockByClassTable" xlink:label="loc_us-gaap_ScheduleOfStockByClassTable_B9EBA55014FEA011D0E0480643084F11" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_ClassOfStockLineItems_AABABB7B91B6B54A2C5A4806430914BB" xlink:to="loc_us-gaap_ScheduleOfStockByClassTable_B9EBA55014FEA011D0E0480643084F11" xlink:type="arc" xbrldt:closed="true" xbrldt:contextElement="segment" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_StatementEquityComponentsAxis" xlink:label="loc_us-gaap_StatementEquityComponentsAxis_B849935176CF6232B3444806430895F9" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfStockByClassTable_B9EBA55014FEA011D0E0480643084F11" xlink:to="loc_us-gaap_StatementEquityComponentsAxis_B849935176CF6232B3444806430895F9" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_EquityComponentDomain" xlink:label="loc_us-gaap_EquityComponentDomain_88735804695E320047F248064308D0AB_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_StatementEquityComponentsAxis_B849935176CF6232B3444806430895F9" xlink:to="loc_us-gaap_EquityComponentDomain_88735804695E320047F248064308D0AB_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_EquityComponentDomain" xlink:label="loc_us-gaap_EquityComponentDomain_88735804695E320047F248064308D0AB" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_StatementEquityComponentsAxis_B849935176CF6232B3444806430895F9" xlink:to="loc_us-gaap_EquityComponentDomain_88735804695E320047F248064308D0AB" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_CommonStockMember" xlink:label="loc_us-gaap_CommonStockMember_479CEA6F3FF39331DB00480643098B39" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityComponentDomain_88735804695E320047F248064308D0AB" xlink:to="loc_us-gaap_CommonStockMember_479CEA6F3FF39331DB00480643098B39" xlink:type="arc" />
    <link:loc xlink:href="anab-20180630.xsd#anab_ClassOfWarrantOrRightNumberOfSecuritiesCalledByWarrantsOrRightsExercised" xlink:label="loc_anab_ClassOfWarrantOrRightNumberOfSecuritiesCalledByWarrantsOrRightsExercised_DA3208A7CA82558236EF48064309220E" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockLineItems_AABABB7B91B6B54A2C5A4806430914BB" xlink:to="loc_anab_ClassOfWarrantOrRightNumberOfSecuritiesCalledByWarrantsOrRightsExercised_DA3208A7CA82558236EF48064309220E" xlink:type="arc" />
    <link:loc xlink:href="anab-20180630.xsd#anab_ClassOfWarrantOrRightNumberOfSecuritiesCalledByWarrantsOrRightsExercisedNoncashExercise" xlink:label="loc_anab_ClassOfWarrantOrRightNumberOfSecuritiesCalledByWarrantsOrRightsExercisedNoncashExercise_D0B281D36FDEB42479FB4806430A369B" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockLineItems_AABABB7B91B6B54A2C5A4806430914BB" xlink:to="loc_anab_ClassOfWarrantOrRightNumberOfSecuritiesCalledByWarrantsOrRightsExercisedNoncashExercise_D0B281D36FDEB42479FB4806430A369B" xlink:type="arc" />
    <link:loc xlink:href="anab-20180630.xsd#anab_StockIssuedDuringPeriodSharesIssuedForWarrants" xlink:label="loc_anab_StockIssuedDuringPeriodSharesIssuedForWarrants_E0D7BE0556547F9333A04806430A47AE" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockLineItems_AABABB7B91B6B54A2C5A4806430914BB" xlink:to="loc_anab_StockIssuedDuringPeriodSharesIssuedForWarrants_E0D7BE0556547F9333A04806430A47AE" xlink:type="arc" />
  </link:definitionLink>
  <link:definitionLink xlink:role="http://www.anaptysbio.com/role/StockholdersEquitySummaryOfCommonStockReservedForFutureIssuanceDetails" xlink:type="extended">
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_ClassOfStockLineItems" xlink:label="loc_us-gaap_ClassOfStockLineItems_22F1E0C407E0DBFFB178D824875CFDD0" xlink:type="locator" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_ScheduleOfStockByClassTable" xlink:label="loc_us-gaap_ScheduleOfStockByClassTable_7C1A77FE185508AD8602D824875A4453" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_ClassOfStockLineItems_22F1E0C407E0DBFFB178D824875CFDD0" xlink:to="loc_us-gaap_ScheduleOfStockByClassTable_7C1A77FE185508AD8602D824875A4453" xlink:type="arc" xbrldt:closed="true" xbrldt:contextElement="segment" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_PlanNameAxis" xlink:label="loc_us-gaap_PlanNameAxis_7CEC70560DD030D89900D824875BE142" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfStockByClassTable_7C1A77FE185508AD8602D824875A4453" xlink:to="loc_us-gaap_PlanNameAxis_7CEC70560DD030D89900D824875BE142" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_PlanNameDomain" xlink:label="loc_us-gaap_PlanNameDomain_321C8BB1FEB8AED4E7E4D824875B3B0F_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_PlanNameAxis_7CEC70560DD030D89900D824875BE142" xlink:to="loc_us-gaap_PlanNameDomain_321C8BB1FEB8AED4E7E4D824875B3B0F_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_PlanNameDomain" xlink:label="loc_us-gaap_PlanNameDomain_321C8BB1FEB8AED4E7E4D824875B3B0F" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_PlanNameAxis_7CEC70560DD030D89900D824875BE142" xlink:to="loc_us-gaap_PlanNameDomain_321C8BB1FEB8AED4E7E4D824875B3B0F" xlink:type="arc" />
    <link:loc xlink:href="anab-20180630.xsd#anab_EquityIncentivePlan2017Member" xlink:label="loc_anab_EquityIncentivePlan2017Member_7528D4B1AA5D4A2498DED824875B835B" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PlanNameDomain_321C8BB1FEB8AED4E7E4D824875B3B0F" xlink:to="loc_anab_EquityIncentivePlan2017Member_7528D4B1AA5D4A2498DED824875B835B" xlink:type="arc" />
    <link:loc xlink:href="anab-20180630.xsd#anab_EmployeeStockPurchasePlan2017Member" xlink:label="loc_anab_EmployeeStockPurchasePlan2017Member_1DE40A9BE17D74C312E4D824875C3B9E" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PlanNameDomain_321C8BB1FEB8AED4E7E4D824875B3B0F" xlink:to="loc_anab_EmployeeStockPurchasePlan2017Member_1DE40A9BE17D74C312E4D824875C3B9E" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_CommonStockNumberOfSharesParValueAndOtherDisclosuresAbstract" xlink:label="loc_us-gaap_CommonStockNumberOfSharesParValueAndOtherDisclosuresAbstract_1B631151548B1C39DB8DD824875CEC14" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockLineItems_22F1E0C407E0DBFFB178D824875CFDD0" xlink:to="loc_us-gaap_CommonStockNumberOfSharesParValueAndOtherDisclosuresAbstract_1B631151548B1C39DB8DD824875CEC14" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingNumber" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingNumber_27FA0EA9DFB01D621914D824875D05A8" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CommonStockNumberOfSharesParValueAndOtherDisclosuresAbstract_1B631151548B1C39DB8DD824875CEC14" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingNumber_27FA0EA9DFB01D621914D824875D05A8" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfSharesAvailableForGrant" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfSharesAvailableForGrant_271F636EB83CF6C74E1CD824875DB036" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockLineItems_22F1E0C407E0DBFFB178D824875CFDD0" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfSharesAvailableForGrant_271F636EB83CF6C74E1CD824875DB036" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_CommonStockCapitalSharesReservedForFutureIssuance" xlink:label="loc_us-gaap_CommonStockCapitalSharesReservedForFutureIssuance_74368F2474BF17616808D824875D24CF" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockLineItems_22F1E0C407E0DBFFB178D824875CFDD0" xlink:to="loc_us-gaap_CommonStockCapitalSharesReservedForFutureIssuance_74368F2474BF17616808D824875D24CF" xlink:type="arc" />
  </link:definitionLink>
  <link:definitionLink xlink:role="http://www.anaptysbio.com/role/StockholdersEquityTables" xlink:type="extended" />
  <link:definitionLink xlink:role="http://www.anaptysbio.com/role/SummaryOfSignificantAccountingPolicies" xlink:type="extended" />
  <link:definitionLink xlink:role="http://www.anaptysbio.com/role/SummaryOfSignificantAccountingPoliciesAdditionalInformationDetails" xlink:type="extended" />
  <link:definitionLink xlink:role="http://www.anaptysbio.com/role/SummaryOfSignificantAccountingPoliciesPolicies" xlink:type="extended" />
  <link:definitionLink xlink:role="http://www.anaptysbio.com/role/SummaryOfSignificantAccountingPoliciesSummaryOfPotentiallyDilutiveSecuritiesDetails" xlink:type="extended">
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareLineItems" xlink:label="loc_us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareLineItems_59929A6F169663D9128748064337E748" xlink:type="locator" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_ScheduleOfAntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareTable" xlink:label="loc_us-gaap_ScheduleOfAntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareTable_54C550CF4E46220B4BAD4806433596B8" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareLineItems_59929A6F169663D9128748064337E748" xlink:to="loc_us-gaap_ScheduleOfAntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareTable_54C550CF4E46220B4BAD4806433596B8" xlink:type="arc" xbrldt:closed="true" xbrldt:contextElement="segment" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareByAntidilutiveSecuritiesAxis" xlink:label="loc_us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareByAntidilutiveSecuritiesAxis_65F014595CAB072E1D634806433518A0" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfAntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareTable_54C550CF4E46220B4BAD4806433596B8" xlink:to="loc_us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareByAntidilutiveSecuritiesAxis_65F014595CAB072E1D634806433518A0" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_AntidilutiveSecuritiesNameDomain" xlink:label="loc_us-gaap_AntidilutiveSecuritiesNameDomain_588CA86529219A52470548064335D2A0_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareByAntidilutiveSecuritiesAxis_65F014595CAB072E1D634806433518A0" xlink:to="loc_us-gaap_AntidilutiveSecuritiesNameDomain_588CA86529219A52470548064335D2A0_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_AntidilutiveSecuritiesNameDomain" xlink:label="loc_us-gaap_AntidilutiveSecuritiesNameDomain_588CA86529219A52470548064335D2A0" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareByAntidilutiveSecuritiesAxis_65F014595CAB072E1D634806433518A0" xlink:to="loc_us-gaap_AntidilutiveSecuritiesNameDomain_588CA86529219A52470548064335D2A0" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_EmployeeStockOptionMember" xlink:label="loc_us-gaap_EmployeeStockOptionMember_D99049822032032BDF6A48064336941D" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AntidilutiveSecuritiesNameDomain_588CA86529219A52470548064335D2A0" xlink:to="loc_us-gaap_EmployeeStockOptionMember_D99049822032032BDF6A48064336941D" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_WarrantMember" xlink:label="loc_us-gaap_WarrantMember_A47B4AE8C2752AF29500480643369AD5" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AntidilutiveSecuritiesNameDomain_588CA86529219A52470548064335D2A0" xlink:to="loc_us-gaap_WarrantMember_A47B4AE8C2752AF29500480643369AD5" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_StatementClassOfStockAxis" xlink:label="loc_us-gaap_StatementClassOfStockAxis_6F36BDE9E5866F0449CF4806433648DD" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfAntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareTable_54C550CF4E46220B4BAD4806433596B8" xlink:to="loc_us-gaap_StatementClassOfStockAxis_6F36BDE9E5866F0449CF4806433648DD" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_ClassOfStockDomain" xlink:label="loc_us-gaap_ClassOfStockDomain_2FDD4C3B08574BA63404480643360CAD_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_StatementClassOfStockAxis_6F36BDE9E5866F0449CF4806433648DD" xlink:to="loc_us-gaap_ClassOfStockDomain_2FDD4C3B08574BA63404480643360CAD_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_ClassOfStockDomain" xlink:label="loc_us-gaap_ClassOfStockDomain_2FDD4C3B08574BA63404480643360CAD" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_StatementClassOfStockAxis_6F36BDE9E5866F0449CF4806433648DD" xlink:to="loc_us-gaap_ClassOfStockDomain_2FDD4C3B08574BA63404480643360CAD" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_CommonStockMember" xlink:label="loc_us-gaap_CommonStockMember_85B55A21D6349DC31A40480643375052" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockDomain_2FDD4C3B08574BA63404480643360CAD" xlink:to="loc_us-gaap_CommonStockMember_85B55A21D6349DC31A40480643375052" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareAmount" xlink:label="loc_us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareAmount_9082A74EFF638CEEA4234806433786A9" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareLineItems_59929A6F169663D9128748064337E748" xlink:to="loc_us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareAmount_9082A74EFF638CEEA4234806433786A9" xlink:type="arc" />
  </link:definitionLink>
  <link:definitionLink xlink:role="http://www.anaptysbio.com/role/SummaryOfSignificantAccountingPoliciesTables" xlink:type="extended" />
</link:linkbase>
