<?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-20181231.xsd#AustraliaResearchAndDevelopmentTaxIncentive" xlink:type="simple" />
  <link:roleRef roleURI="http://www.anaptysbio.com/role/AustraliaResearchAndDevelopmentTaxIncentiveDetails" xlink:href="anab-20181231.xsd#AustraliaResearchAndDevelopmentTaxIncentiveDetails" xlink:type="simple" />
  <link:roleRef roleURI="http://www.anaptysbio.com/role/BalanceSheetAccountsAndSupplementalDisclosures" xlink:href="anab-20181231.xsd#BalanceSheetAccountsAndSupplementalDisclosures" xlink:type="simple" />
  <link:roleRef roleURI="http://www.anaptysbio.com/role/BalanceSheetAccountsAndSupplementalDisclosuresAccruedExpensesDetails" xlink:href="anab-20181231.xsd#BalanceSheetAccountsAndSupplementalDisclosuresAccruedExpensesDetails" xlink:type="simple" />
  <link:roleRef roleURI="http://www.anaptysbio.com/role/BalanceSheetAccountsAndSupplementalDisclosuresPropertyAndEquipmentDetails" xlink:href="anab-20181231.xsd#BalanceSheetAccountsAndSupplementalDisclosuresPropertyAndEquipmentDetails" xlink:type="simple" />
  <link:roleRef roleURI="http://www.anaptysbio.com/role/BalanceSheetAccountsAndSupplementalDisclosuresTables" xlink:href="anab-20181231.xsd#BalanceSheetAccountsAndSupplementalDisclosuresTables" xlink:type="simple" />
  <link:roleRef roleURI="http://www.anaptysbio.com/role/CollaborativeResearchAndDevelopmentAgreements" xlink:href="anab-20181231.xsd#CollaborativeResearchAndDevelopmentAgreements" xlink:type="simple" />
  <link:roleRef roleURI="http://www.anaptysbio.com/role/CollaborativeResearchAndDevelopmentAgreementsDetails" xlink:href="anab-20181231.xsd#CollaborativeResearchAndDevelopmentAgreementsDetails" xlink:type="simple" />
  <link:roleRef roleURI="http://www.anaptysbio.com/role/CollaborativeResearchAndDevelopmentAgreementsTables" xlink:href="anab-20181231.xsd#CollaborativeResearchAndDevelopmentAgreementsTables" xlink:type="simple" />
  <link:roleRef roleURI="http://www.anaptysbio.com/role/CommitmentsAndContingencies" xlink:href="anab-20181231.xsd#CommitmentsAndContingencies" xlink:type="simple" />
  <link:roleRef roleURI="http://www.anaptysbio.com/role/CommitmentsAndContingenciesLicensingAgreementsDetails" xlink:href="anab-20181231.xsd#CommitmentsAndContingenciesLicensingAgreementsDetails" xlink:type="simple" />
  <link:roleRef roleURI="http://www.anaptysbio.com/role/CommitmentsAndContingenciesOperatingLeasesDetails" xlink:href="anab-20181231.xsd#CommitmentsAndContingenciesOperatingLeasesDetails" xlink:type="simple" />
  <link:roleRef roleURI="http://www.anaptysbio.com/role/CommitmentsAndContingenciesTables" xlink:href="anab-20181231.xsd#CommitmentsAndContingenciesTables" xlink:type="simple" />
  <link:roleRef roleURI="http://www.anaptysbio.com/role/ConsolidatedBalanceSheets" xlink:href="anab-20181231.xsd#ConsolidatedBalanceSheets" xlink:type="simple" />
  <link:roleRef roleURI="http://www.anaptysbio.com/role/ConsolidatedBalanceSheetsParenthetical" xlink:href="anab-20181231.xsd#ConsolidatedBalanceSheetsParenthetical" xlink:type="simple" />
  <link:roleRef roleURI="http://www.anaptysbio.com/role/ConsolidatedStatementsOfCashFlows" xlink:href="anab-20181231.xsd#ConsolidatedStatementsOfCashFlows" xlink:type="simple" />
  <link:roleRef roleURI="http://www.anaptysbio.com/role/ConsolidatedStatementsOfConvertiblePreferredStockAndStockholdersEquityDeficit" xlink:href="anab-20181231.xsd#ConsolidatedStatementsOfConvertiblePreferredStockAndStockholdersEquityDeficit" xlink:type="simple" />
  <link:roleRef roleURI="http://www.anaptysbio.com/role/ConsolidatedStatementsOfOperationsAndComprehensiveLoss" xlink:href="anab-20181231.xsd#ConsolidatedStatementsOfOperationsAndComprehensiveLoss" xlink:type="simple" />
  <link:roleRef roleURI="http://www.anaptysbio.com/role/DescriptionOfBusiness" xlink:href="anab-20181231.xsd#DescriptionOfBusiness" xlink:type="simple" />
  <link:roleRef roleURI="http://www.anaptysbio.com/role/DescriptionOfBusinessDetails" xlink:href="anab-20181231.xsd#DescriptionOfBusinessDetails" xlink:type="simple" />
  <link:roleRef roleURI="http://www.anaptysbio.com/role/DocumentAndEntityInformation" xlink:href="anab-20181231.xsd#DocumentAndEntityInformation" xlink:type="simple" />
  <link:roleRef roleURI="http://www.anaptysbio.com/role/EmployeeBenefitPlan" xlink:href="anab-20181231.xsd#EmployeeBenefitPlan" xlink:type="simple" />
  <link:roleRef roleURI="http://www.anaptysbio.com/role/EmployeeBenefitPlanDetails" xlink:href="anab-20181231.xsd#EmployeeBenefitPlanDetails" xlink:type="simple" />
  <link:roleRef roleURI="http://www.anaptysbio.com/role/EquityIncentivePlans" xlink:href="anab-20181231.xsd#EquityIncentivePlans" xlink:type="simple" />
  <link:roleRef roleURI="http://www.anaptysbio.com/role/EquityIncentivePlansAllocationOfShareBasedCompensationExpenseDetails" xlink:href="anab-20181231.xsd#EquityIncentivePlansAllocationOfShareBasedCompensationExpenseDetails" xlink:type="simple" />
  <link:roleRef roleURI="http://www.anaptysbio.com/role/EquityIncentivePlansNarrativeDetails" xlink:href="anab-20181231.xsd#EquityIncentivePlansNarrativeDetails" xlink:type="simple" />
  <link:roleRef roleURI="http://www.anaptysbio.com/role/EquityIncentivePlansOptionActivityDetails" xlink:href="anab-20181231.xsd#EquityIncentivePlansOptionActivityDetails" xlink:type="simple" />
  <link:roleRef roleURI="http://www.anaptysbio.com/role/EquityIncentivePlansOptionFairValueAssumptionsDetails" xlink:href="anab-20181231.xsd#EquityIncentivePlansOptionFairValueAssumptionsDetails" xlink:type="simple" />
  <link:roleRef roleURI="http://www.anaptysbio.com/role/EquityIncentivePlansTables" xlink:href="anab-20181231.xsd#EquityIncentivePlansTables" xlink:type="simple" />
  <link:roleRef roleURI="http://www.anaptysbio.com/role/FairValueMeasurementsAndAvailableForSaleInvestments" xlink:href="anab-20181231.xsd#FairValueMeasurementsAndAvailableForSaleInvestments" xlink:type="simple" />
  <link:roleRef roleURI="http://www.anaptysbio.com/role/FairValueMeasurementsAndAvailableForSaleInvestmentsAssetsAndLiabilitiesMeasuredAtFairValueOnRecurringBasisDetails" xlink:href="anab-20181231.xsd#FairValueMeasurementsAndAvailableForSaleInvestmentsAssetsAndLiabilitiesMeasuredAtFairValueOnRecurringBasisDetails" xlink:type="simple" />
  <link:roleRef roleURI="http://www.anaptysbio.com/role/FairValueMeasurementsAndAvailableForSaleInvestmentsAvailableForSaleInvestmentsDetails" xlink:href="anab-20181231.xsd#FairValueMeasurementsAndAvailableForSaleInvestmentsAvailableForSaleInvestmentsDetails" xlink:type="simple" />
  <link:roleRef roleURI="http://www.anaptysbio.com/role/FairValueMeasurementsAndAvailableForSaleInvestmentsFairValueAssumptionsDetails" xlink:href="anab-20181231.xsd#FairValueMeasurementsAndAvailableForSaleInvestmentsFairValueAssumptionsDetails" xlink:type="simple" />
  <link:roleRef roleURI="http://www.anaptysbio.com/role/FairValueMeasurementsAndAvailableForSaleInvestmentsFairValueOfOtherFinancialInstrumentsDetails" xlink:href="anab-20181231.xsd#FairValueMeasurementsAndAvailableForSaleInvestmentsFairValueOfOtherFinancialInstrumentsDetails" xlink:type="simple" />
  <link:roleRef roleURI="http://www.anaptysbio.com/role/FairValueMeasurementsAndAvailableForSaleInvestmentsLiabilitiesWithSignificantUnobservableInputsDetails" xlink:href="anab-20181231.xsd#FairValueMeasurementsAndAvailableForSaleInvestmentsLiabilitiesWithSignificantUnobservableInputsDetails" xlink:type="simple" />
  <link:roleRef roleURI="http://www.anaptysbio.com/role/FairValueMeasurementsAndAvailableForSaleInvestmentsTables" xlink:href="anab-20181231.xsd#FairValueMeasurementsAndAvailableForSaleInvestmentsTables" xlink:type="simple" />
  <link:roleRef roleURI="http://www.anaptysbio.com/role/IncomeTaxes" xlink:href="anab-20181231.xsd#IncomeTaxes" xlink:type="simple" />
  <link:roleRef roleURI="http://www.anaptysbio.com/role/IncomeTaxesAdditionalInformationDetails" xlink:href="anab-20181231.xsd#IncomeTaxesAdditionalInformationDetails" xlink:type="simple" />
  <link:roleRef roleURI="http://www.anaptysbio.com/role/IncomeTaxesComponentsOfIncomeLossBeforeIncomeTaxProvisionBenefitDetails" xlink:href="anab-20181231.xsd#IncomeTaxesComponentsOfIncomeLossBeforeIncomeTaxProvisionBenefitDetails" xlink:type="simple" />
  <link:roleRef roleURI="http://www.anaptysbio.com/role/IncomeTaxesDeferredTaxAssetsAndLiabilitiesDetails" xlink:href="anab-20181231.xsd#IncomeTaxesDeferredTaxAssetsAndLiabilitiesDetails" xlink:type="simple" />
  <link:roleRef roleURI="http://www.anaptysbio.com/role/IncomeTaxesReconciliationOfIncomeTaxesDetails" xlink:href="anab-20181231.xsd#IncomeTaxesReconciliationOfIncomeTaxesDetails" xlink:type="simple" />
  <link:roleRef roleURI="http://www.anaptysbio.com/role/IncomeTaxesTables" xlink:href="anab-20181231.xsd#IncomeTaxesTables" xlink:type="simple" />
  <link:roleRef roleURI="http://www.anaptysbio.com/role/IncomeTaxesUnrecognizedTaxBenefitsDetails" xlink:href="anab-20181231.xsd#IncomeTaxesUnrecognizedTaxBenefitsDetails" xlink:type="simple" />
  <link:roleRef roleURI="http://www.anaptysbio.com/role/NotesPayable" xlink:href="anab-20181231.xsd#NotesPayable" xlink:type="simple" />
  <link:roleRef roleURI="http://www.anaptysbio.com/role/NotesPayableDetails" xlink:href="anab-20181231.xsd#NotesPayableDetails" xlink:type="simple" />
  <link:roleRef roleURI="http://www.anaptysbio.com/role/SelectedQuarterlyFinancialDataUnaudited" xlink:href="anab-20181231.xsd#SelectedQuarterlyFinancialDataUnaudited" xlink:type="simple" />
  <link:roleRef roleURI="http://www.anaptysbio.com/role/SelectedQuarterlyFinancialDataUnauditedDetails" xlink:href="anab-20181231.xsd#SelectedQuarterlyFinancialDataUnauditedDetails" xlink:type="simple" />
  <link:roleRef roleURI="http://www.anaptysbio.com/role/SelectedQuarterlyFinancialDataUnauditedTables" xlink:href="anab-20181231.xsd#SelectedQuarterlyFinancialDataUnauditedTables" xlink:type="simple" />
  <link:roleRef roleURI="http://www.anaptysbio.com/role/StockholdersEquity" xlink:href="anab-20181231.xsd#StockholdersEquity" xlink:type="simple" />
  <link:roleRef roleURI="http://www.anaptysbio.com/role/StockholdersEquityAdditionalInformationDetails" xlink:href="anab-20181231.xsd#StockholdersEquityAdditionalInformationDetails" xlink:type="simple" />
  <link:roleRef roleURI="http://www.anaptysbio.com/role/StockholdersEquitySummaryOfCommonStockReservedForFutureIssuanceDetails" xlink:href="anab-20181231.xsd#StockholdersEquitySummaryOfCommonStockReservedForFutureIssuanceDetails" xlink:type="simple" />
  <link:roleRef roleURI="http://www.anaptysbio.com/role/StockholdersEquityTables" xlink:href="anab-20181231.xsd#StockholdersEquityTables" xlink:type="simple" />
  <link:roleRef roleURI="http://www.anaptysbio.com/role/SummaryOfSignificantAccountingPolicies" xlink:href="anab-20181231.xsd#SummaryOfSignificantAccountingPolicies" xlink:type="simple" />
  <link:roleRef roleURI="http://www.anaptysbio.com/role/SummaryOfSignificantAccountingPoliciesAdditionalInformationDetails" xlink:href="anab-20181231.xsd#SummaryOfSignificantAccountingPoliciesAdditionalInformationDetails" xlink:type="simple" />
  <link:roleRef roleURI="http://www.anaptysbio.com/role/SummaryOfSignificantAccountingPoliciesPolicies" xlink:href="anab-20181231.xsd#SummaryOfSignificantAccountingPoliciesPolicies" xlink:type="simple" />
  <link:roleRef roleURI="http://www.anaptysbio.com/role/SummaryOfSignificantAccountingPoliciesSummaryOfPotentiallyDilutiveSecuritiesDetails" xlink:href="anab-20181231.xsd#SummaryOfSignificantAccountingPoliciesSummaryOfPotentiallyDilutiveSecuritiesDetails" xlink:type="simple" />
  <link:roleRef roleURI="http://www.anaptysbio.com/role/SummaryOfSignificantAccountingPoliciesTables" xlink:href="anab-20181231.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_4C1B0E41996A9AB45E00E924A38B6FD5" 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_F05AC87557CD397F6AF9E924A38862F5" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_TaxCreditCarryforwardLineItems_4C1B0E41996A9AB45E00E924A38B6FD5" xlink:to="loc_us-gaap_TaxCreditCarryforwardTable_F05AC87557CD397F6AF9E924A38862F5" 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_E3AA0C6E034F01437175E924A389684C" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_TaxCreditCarryforwardTable_F05AC87557CD397F6AF9E924A38862F5" xlink:to="loc_us-gaap_IncomeTaxAuthorityNameAxis_E3AA0C6E034F01437175E924A389684C" 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_90C796F89BF42C8B9A6EE924A3898BEB_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_IncomeTaxAuthorityNameAxis_E3AA0C6E034F01437175E924A389684C" xlink:to="loc_us-gaap_IncomeTaxAuthorityNameDomain_90C796F89BF42C8B9A6EE924A3898BEB_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_90C796F89BF42C8B9A6EE924A3898BEB" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_IncomeTaxAuthorityNameAxis_E3AA0C6E034F01437175E924A389684C" xlink:to="loc_us-gaap_IncomeTaxAuthorityNameDomain_90C796F89BF42C8B9A6EE924A3898BEB" 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_463BDCA752EF47DE8F71E924A3898A46" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncomeTaxAuthorityNameDomain_90C796F89BF42C8B9A6EE924A3898BEB" xlink:to="loc_us-gaap_AustralianTaxationOfficeMember_463BDCA752EF47DE8F71E924A3898A46" 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_D2333F5F8A8A7BEF330DE924A38A12FA" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_TaxCreditCarryforwardTable_F05AC87557CD397F6AF9E924A38862F5" xlink:to="loc_srt_ConsolidatedEntitiesAxis_D2333F5F8A8A7BEF330DE924A38A12FA" 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_35D20196A2D56679F5DDE924A38A6D73_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_ConsolidatedEntitiesAxis_D2333F5F8A8A7BEF330DE924A38A12FA" xlink:to="loc_srt_ConsolidatedEntitiesDomain_35D20196A2D56679F5DDE924A38A6D73_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_35D20196A2D56679F5DDE924A38A6D73" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_ConsolidatedEntitiesAxis_D2333F5F8A8A7BEF330DE924A38A12FA" xlink:to="loc_srt_ConsolidatedEntitiesDomain_35D20196A2D56679F5DDE924A38A6D73" 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_6A2B872DF9638574BB1AE924A38AF56F" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ConsolidatedEntitiesDomain_35D20196A2D56679F5DDE924A38A6D73" xlink:to="loc_srt_SubsidiariesMember_6A2B872DF9638574BB1AE924A38AF56F" xlink:type="arc" />
    <link:loc xlink:href="anab-20181231.xsd#anab_ResearchAndDevelopmentTaxIncentiveCreditPercentage" xlink:label="loc_anab_ResearchAndDevelopmentTaxIncentiveCreditPercentage_F333EB104C53BD0F699FE924A38B6102" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TaxCreditCarryforwardLineItems_4C1B0E41996A9AB45E00E924A38B6FD5" xlink:to="loc_anab_ResearchAndDevelopmentTaxIncentiveCreditPercentage_F333EB104C53BD0F699FE924A38B6102" xlink:type="arc" />
    <link:loc xlink:href="anab-20181231.xsd#anab_ResearchAndDevelopmentTaxIncentiveCredit" xlink:label="loc_anab_ResearchAndDevelopmentTaxIncentiveCredit_E5BB040DFD796F13C4C8E924A38B7C85" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TaxCreditCarryforwardLineItems_4C1B0E41996A9AB45E00E924A38B6FD5" xlink:to="loc_anab_ResearchAndDevelopmentTaxIncentiveCredit_E5BB040DFD796F13C4C8E924A38B7C85" xlink:type="arc" />
    <link:loc xlink:href="anab-20181231.xsd#anab_ResearchAndDevelopmentTaxIncentiveCreditReceivableCurrent" xlink:label="loc_anab_ResearchAndDevelopmentTaxIncentiveCreditReceivableCurrent_9B039CD84D411F76A01AE924A38C9F0D" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TaxCreditCarryforwardLineItems_4C1B0E41996A9AB45E00E924A38B6FD5" xlink:to="loc_anab_ResearchAndDevelopmentTaxIncentiveCreditReceivableCurrent_9B039CD84D411F76A01AE924A38C9F0D" xlink:type="arc" />
    <link:loc xlink:href="anab-20181231.xsd#anab_ResearchAndDevelopmentTaxIncentiveCreditReceivedDuringPeriod" xlink:label="loc_anab_ResearchAndDevelopmentTaxIncentiveCreditReceivedDuringPeriod_7A9089FB001E91FF6432E924A38CB38D" xlink:type="locator" />
    <link:definitionArc order="4" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TaxCreditCarryforwardLineItems_4C1B0E41996A9AB45E00E924A38B6FD5" xlink:to="loc_anab_ResearchAndDevelopmentTaxIncentiveCreditReceivedDuringPeriod_7A9089FB001E91FF6432E924A38CB38D" 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_A8BBD92A1C696FAF13D8E8E1C2E121F0" 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_04D89F5378538A417F7AE8E1C2DEE64A" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentLineItems_A8BBD92A1C696FAF13D8E8E1C2E121F0" xlink:to="loc_us-gaap_ScheduleOfPropertyPlantAndEquipmentTable_04D89F5378538A417F7AE8E1C2DEE64A" 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_5D040BC863FAF474D09DE8E1C2DF1B47" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfPropertyPlantAndEquipmentTable_04D89F5378538A417F7AE8E1C2DEE64A" xlink:to="loc_us-gaap_PropertyPlantAndEquipmentByTypeAxis_5D040BC863FAF474D09DE8E1C2DF1B47" 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_8987C7DA49CDD44B3127E8E1C2DF805F_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentByTypeAxis_5D040BC863FAF474D09DE8E1C2DF1B47" xlink:to="loc_us-gaap_PropertyPlantAndEquipmentTypeDomain_8987C7DA49CDD44B3127E8E1C2DF805F_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_8987C7DA49CDD44B3127E8E1C2DF805F" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentByTypeAxis_5D040BC863FAF474D09DE8E1C2DF1B47" xlink:to="loc_us-gaap_PropertyPlantAndEquipmentTypeDomain_8987C7DA49CDD44B3127E8E1C2DF805F" xlink:type="arc" />
    <link:loc xlink:href="anab-20181231.xsd#anab_LaboratoryEquipmentMember" xlink:label="loc_anab_LaboratoryEquipmentMember_D1F3AB8E2E172669EB07E8E1C2E0F5EB" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentTypeDomain_8987C7DA49CDD44B3127E8E1C2DF805F" xlink:to="loc_anab_LaboratoryEquipmentMember_D1F3AB8E2E172669EB07E8E1C2E0F5EB" 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_1003F604FCE2B184AF25E8E1C2E08B9E" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentTypeDomain_8987C7DA49CDD44B3127E8E1C2DF805F" xlink:to="loc_us-gaap_OfficeEquipmentMember_1003F604FCE2B184AF25E8E1C2E08B9E" 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_C7505B2AD7160DA9D8CCE8E1C2E0D063" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentTypeDomain_8987C7DA49CDD44B3127E8E1C2DF805F" xlink:to="loc_us-gaap_LeaseholdImprovementsMember_C7505B2AD7160DA9D8CCE8E1C2E0D063" 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_FC75423312746BAEBE7EE8E1C2E1B435" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentLineItems_A8BBD92A1C696FAF13D8E8E1C2E121F0" xlink:to="loc_us-gaap_PropertyPlantAndEquipmentGross_FC75423312746BAEBE7EE8E1C2E1B435" 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_D3CDFB356C7F762E033EE8E1C2E2CCCD" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentLineItems_A8BBD92A1C696FAF13D8E8E1C2E121F0" xlink:to="loc_us-gaap_AccumulatedDepreciationDepletionAndAmortizationPropertyPlantAndEquipment_D3CDFB356C7F762E033EE8E1C2E2CCCD" 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_E9ECB1DE5212DAA96AAFE8E1C2E2B9C3" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentLineItems_A8BBD92A1C696FAF13D8E8E1C2E121F0" xlink:to="loc_us-gaap_PropertyPlantAndEquipmentNet_E9ECB1DE5212DAA96AAFE8E1C2E2B9C3" 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_CollaborativeArrangementsAndNoncollaborativeArrangementTransactionsLineItems" xlink:label="loc_us-gaap_CollaborativeArrangementsAndNoncollaborativeArrangementTransactionsLineItems_D531020A6B6A9ED6904CE924A48048F4" xlink:type="locator" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_ScheduleOfCollaborativeArrangementsAndNoncollaborativeArrangementTransactionsTable" xlink:label="loc_us-gaap_ScheduleOfCollaborativeArrangementsAndNoncollaborativeArrangementTransactionsTable_B6424EE1CC48BC5E8D13E924A47B7596" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_CollaborativeArrangementsAndNoncollaborativeArrangementTransactionsLineItems_D531020A6B6A9ED6904CE924A48048F4" xlink:to="loc_us-gaap_ScheduleOfCollaborativeArrangementsAndNoncollaborativeArrangementTransactionsTable_B6424EE1CC48BC5E8D13E924A47B7596" 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_B250824C9A7BAF91711EE924A47B9D52" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfCollaborativeArrangementsAndNoncollaborativeArrangementTransactionsTable_B6424EE1CC48BC5E8D13E924A47B7596" xlink:to="loc_srt_CounterpartyNameAxis_B250824C9A7BAF91711EE924A47B9D52" 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_00DD5B3BA86B1725882AE924A47C29C2_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_CounterpartyNameAxis_B250824C9A7BAF91711EE924A47B9D52" xlink:to="loc_srt_RepurchaseAgreementCounterpartyNameDomain_00DD5B3BA86B1725882AE924A47C29C2_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_00DD5B3BA86B1725882AE924A47C29C2" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_CounterpartyNameAxis_B250824C9A7BAF91711EE924A47B9D52" xlink:to="loc_srt_RepurchaseAgreementCounterpartyNameDomain_00DD5B3BA86B1725882AE924A47C29C2" xlink:type="arc" />
    <link:loc xlink:href="anab-20181231.xsd#anab_TESAROInc.AndTESARODevelopmentInc.Member" xlink:label="loc_anab_TESAROInc.AndTESARODevelopmentInc.Member_68FECA614CCA1F81426FE924A47C53BB" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_RepurchaseAgreementCounterpartyNameDomain_00DD5B3BA86B1725882AE924A47C29C2" xlink:to="loc_anab_TESAROInc.AndTESARODevelopmentInc.Member_68FECA614CCA1F81426FE924A47C53BB" xlink:type="arc" />
    <link:loc xlink:href="anab-20181231.xsd#anab_CelgeneCorporationMember" xlink:label="loc_anab_CelgeneCorporationMember_F31E48BF55406AF5FDE0E924A47C03C0" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_RepurchaseAgreementCounterpartyNameDomain_00DD5B3BA86B1725882AE924A47C29C2" xlink:to="loc_anab_CelgeneCorporationMember_F31E48BF55406AF5FDE0E924A47C03C0" 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_3D25177F2EF15C0BFC3AE924A47CA6D0" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfCollaborativeArrangementsAndNoncollaborativeArrangementTransactionsTable_B6424EE1CC48BC5E8D13E924A47B7596" xlink:to="loc_us-gaap_TypeOfArrangementAxis_3D25177F2EF15C0BFC3AE924A47CA6D0" 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_15E0E9C0765A3DB77436E924A47DA37C_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_TypeOfArrangementAxis_3D25177F2EF15C0BFC3AE924A47CA6D0" xlink:to="loc_us-gaap_ArrangementsAndNonarrangementTransactionsMember_15E0E9C0765A3DB77436E924A47DA37C_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_15E0E9C0765A3DB77436E924A47DA37C" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_TypeOfArrangementAxis_3D25177F2EF15C0BFC3AE924A47CA6D0" xlink:to="loc_us-gaap_ArrangementsAndNonarrangementTransactionsMember_15E0E9C0765A3DB77436E924A47DA37C" 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_FA2CE4DA52529B5F621AE924A47D4E7F" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ArrangementsAndNonarrangementTransactionsMember_15E0E9C0765A3DB77436E924A47DA37C" xlink:to="loc_us-gaap_CollaborativeArrangementMember_FA2CE4DA52529B5F621AE924A47D4E7F" xlink:type="arc" />
    <link:loc xlink:href="anab-20181231.xsd#anab_InVivoToxicologyStudiesMember" xlink:label="loc_anab_InVivoToxicologyStudiesMember_B243EE1968AC00370E12E924A47DC27F" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CollaborativeArrangementMember_FA2CE4DA52529B5F621AE924A47D4E7F" xlink:to="loc_anab_InVivoToxicologyStudiesMember_B243EE1968AC00370E12E924A47DC27F" xlink:type="arc" />
    <link:loc xlink:href="anab-20181231.xsd#anab_ClearanceOfInvestigationalNewDrugFromFDAMember" xlink:label="loc_anab_ClearanceOfInvestigationalNewDrugFromFDAMember_6E871721B6546621F8A3E924A47E1293" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CollaborativeArrangementMember_FA2CE4DA52529B5F621AE924A47D4E7F" xlink:to="loc_anab_ClearanceOfInvestigationalNewDrugFromFDAMember_6E871721B6546621F8A3E924A47E1293" xlink:type="arc" />
    <link:loc xlink:href="anab-20181231.xsd#anab_Phase2ClinicalTrialInitiationMember" xlink:label="loc_anab_Phase2ClinicalTrialInitiationMember_68E0628DEC2657211FABE924A47E9E1E" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CollaborativeArrangementMember_FA2CE4DA52529B5F621AE924A47D4E7F" xlink:to="loc_anab_Phase2ClinicalTrialInitiationMember_68E0628DEC2657211FABE924A47E9E1E" xlink:type="arc" />
    <link:loc xlink:href="anab-20181231.xsd#anab_Phase1ClinicalTrialInitiationMember" xlink:label="loc_anab_Phase1ClinicalTrialInitiationMember_792D3E5D47D8C928B2D3E924A47EEECD" xlink:type="locator" />
    <link:definitionArc order="4" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CollaborativeArrangementMember_FA2CE4DA52529B5F621AE924A47D4E7F" xlink:to="loc_anab_Phase1ClinicalTrialInitiationMember_792D3E5D47D8C928B2D3E924A47EEECD" xlink:type="arc" />
    <link:loc xlink:href="anab-20181231.xsd#anab_Phase3ClinicalTrialInitiationMember" xlink:label="loc_anab_Phase3ClinicalTrialInitiationMember_4227BAC0082299AC1BF4E924A47E67E6" xlink:type="locator" />
    <link:definitionArc order="5" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CollaborativeArrangementMember_FA2CE4DA52529B5F621AE924A47D4E7F" xlink:to="loc_anab_Phase3ClinicalTrialInitiationMember_4227BAC0082299AC1BF4E924A47E67E6" 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_451E7D991CF2BBDDD77FE924A47FF34A" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfCollaborativeArrangementsAndNoncollaborativeArrangementTransactionsTable_B6424EE1CC48BC5E8D13E924A47B7596" xlink:to="loc_srt_ProductOrServiceAxis_451E7D991CF2BBDDD77FE924A47FF34A" 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_B259C2850920E16E3250E924A47FFCFA_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_ProductOrServiceAxis_451E7D991CF2BBDDD77FE924A47FF34A" xlink:to="loc_srt_ProductsAndServicesDomain_B259C2850920E16E3250E924A47FFCFA_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_B259C2850920E16E3250E924A47FFCFA" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_ProductOrServiceAxis_451E7D991CF2BBDDD77FE924A47FF34A" xlink:to="loc_srt_ProductsAndServicesDomain_B259C2850920E16E3250E924A47FFCFA" xlink:type="arc" />
    <link:loc xlink:href="anab-20181231.xsd#anab_AnaptysBiogeneratedAntiPD1AntagonistAntibodyTSR042Member" xlink:label="loc_anab_AnaptysBiogeneratedAntiPD1AntagonistAntibodyTSR042Member_9BFD1D72786664A14DBCE924A47FA3DD" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ProductsAndServicesDomain_B259C2850920E16E3250E924A47FFCFA" xlink:to="loc_anab_AnaptysBiogeneratedAntiPD1AntagonistAntibodyTSR042Member_9BFD1D72786664A14DBCE924A47FA3DD" xlink:type="arc" />
    <link:loc xlink:href="anab-20181231.xsd#anab_AnaptysBioGeneratedAntiTIM3AntagonistAntibodyTSR022Member" xlink:label="loc_anab_AnaptysBioGeneratedAntiTIM3AntagonistAntibodyTSR022Member_4FE68603AC62F3FE1FDEE924A47F064B" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ProductsAndServicesDomain_B259C2850920E16E3250E924A47FFCFA" xlink:to="loc_anab_AnaptysBioGeneratedAntiTIM3AntagonistAntibodyTSR022Member_4FE68603AC62F3FE1FDEE924A47F064B" xlink:type="arc" />
    <link:loc xlink:href="anab-20181231.xsd#anab_AnaptysBioGeneratedAntiLAG3AntagonistAntibodyTSR033Member" xlink:label="loc_anab_AnaptysBioGeneratedAntiLAG3AntagonistAntibodyTSR033Member_31D92B2CC3285066D5EEE924A480CA6A" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ProductsAndServicesDomain_B259C2850920E16E3250E924A47FFCFA" xlink:to="loc_anab_AnaptysBioGeneratedAntiLAG3AntagonistAntibodyTSR033Member_31D92B2CC3285066D5EEE924A480CA6A" xlink:type="arc" />
    <link:loc xlink:href="anab-20181231.xsd#anab_AnaptysBioGeneratedAntiPD1AntagonistAntibodyCC90006Member" xlink:label="loc_anab_AnaptysBioGeneratedAntiPD1AntagonistAntibodyCC90006Member_EBB7F6EC51E8C12DCEBEE924A4803A5C" xlink:type="locator" />
    <link:definitionArc order="4" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ProductsAndServicesDomain_B259C2850920E16E3250E924A47FFCFA" xlink:to="loc_anab_AnaptysBioGeneratedAntiPD1AntagonistAntibodyCC90006Member_EBB7F6EC51E8C12DCEBEE924A4803A5C" xlink:type="arc" />
    <link:loc xlink:href="anab-20181231.xsd#anab_RevenueRecognitionMultipledeliverableArrangementsUpfrontFeeReceived" xlink:label="loc_anab_RevenueRecognitionMultipledeliverableArrangementsUpfrontFeeReceived_261CC4708F0B300FAC3CE924A48081E8" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CollaborativeArrangementsAndNoncollaborativeArrangementTransactionsLineItems_D531020A6B6A9ED6904CE924A48048F4" xlink:to="loc_anab_RevenueRecognitionMultipledeliverableArrangementsUpfrontFeeReceived_261CC4708F0B300FAC3CE924A48081E8" xlink:type="arc" />
    <link:loc xlink:href="anab-20181231.xsd#anab_RevenueRecognitionMilestoneMethodNumberOfOutstandingResearchAndDevelopmentTargets" xlink:label="loc_anab_RevenueRecognitionMilestoneMethodNumberOfOutstandingResearchAndDevelopmentTargets_E080EA6288925C594E9CE924A4811A54" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CollaborativeArrangementsAndNoncollaborativeArrangementTransactionsLineItems_D531020A6B6A9ED6904CE924A48048F4" xlink:to="loc_anab_RevenueRecognitionMilestoneMethodNumberOfOutstandingResearchAndDevelopmentTargets_E080EA6288925C594E9CE924A4811A54" xlink:type="arc" />
    <link:loc xlink:href="anab-20181231.xsd#anab_RevenueRecognitionMilestoneMethodContingentUponPreclinicalAndClinicalTrialEvents" xlink:label="loc_anab_RevenueRecognitionMilestoneMethodContingentUponPreclinicalAndClinicalTrialEvents_74CD0D121A7CFFA56624E924A48163E1" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CollaborativeArrangementsAndNoncollaborativeArrangementTransactionsLineItems_D531020A6B6A9ED6904CE924A48048F4" xlink:to="loc_anab_RevenueRecognitionMilestoneMethodContingentUponPreclinicalAndClinicalTrialEvents_74CD0D121A7CFFA56624E924A48163E1" xlink:type="arc" />
    <link:loc xlink:href="anab-20181231.xsd#anab_RevenueRecognitionMilestoneMethodContingentUponCertainUnitedStatesAndEuropeanRegulatorySubmissionsAndApprovals" xlink:label="loc_anab_RevenueRecognitionMilestoneMethodContingentUponCertainUnitedStatesAndEuropeanRegulatorySubmissionsAndApprovals_BBD3DB6BE2063EAABA2CE924A481EF42" xlink:type="locator" />
    <link:definitionArc order="4" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CollaborativeArrangementsAndNoncollaborativeArrangementTransactionsLineItems_D531020A6B6A9ED6904CE924A48048F4" xlink:to="loc_anab_RevenueRecognitionMilestoneMethodContingentUponCertainUnitedStatesAndEuropeanRegulatorySubmissionsAndApprovals_BBD3DB6BE2063EAABA2CE924A481EF42" xlink:type="arc" />
    <link:loc xlink:href="anab-20181231.xsd#anab_RevenueRecognitionMilestoneMethodContingentUponAchievementOfSpecifiedLevelsOfWorldwideSales" xlink:label="loc_anab_RevenueRecognitionMilestoneMethodContingentUponAchievementOfSpecifiedLevelsOfWorldwideSales_14201466F283CDEF875BE924A4827153" xlink:type="locator" />
    <link:definitionArc order="5" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CollaborativeArrangementsAndNoncollaborativeArrangementTransactionsLineItems_D531020A6B6A9ED6904CE924A48048F4" xlink:to="loc_anab_RevenueRecognitionMilestoneMethodContingentUponAchievementOfSpecifiedLevelsOfWorldwideSales_14201466F283CDEF875BE924A4827153" xlink:type="arc" />
    <link:loc xlink:href="anab-20181231.xsd#anab_RevenueRecognitionMilestoneMethodAgreementTermFollowingFirstCommercialSaleOrExpirationOfTheLastToExpirePatent" xlink:label="loc_anab_RevenueRecognitionMilestoneMethodAgreementTermFollowingFirstCommercialSaleOrExpirationOfTheLastToExpirePatent_32495A902C62CDEC98CEE924A4820CAA" xlink:type="locator" />
    <link:definitionArc order="6" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CollaborativeArrangementsAndNoncollaborativeArrangementTransactionsLineItems_D531020A6B6A9ED6904CE924A48048F4" xlink:to="loc_anab_RevenueRecognitionMilestoneMethodAgreementTermFollowingFirstCommercialSaleOrExpirationOfTheLastToExpirePatent_32495A902C62CDEC98CEE924A4820CAA" 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_AAD44794316A3CFA6B26E924A48234BC" xlink:type="locator" />
    <link:definitionArc order="7" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CollaborativeArrangementsAndNoncollaborativeArrangementTransactionsLineItems_D531020A6B6A9ED6904CE924A48048F4" xlink:to="loc_us-gaap_RevenueFromContractWithCustomerIncludingAssessedTax_AAD44794316A3CFA6B26E924A48234BC" xlink:type="arc" />
    <link:loc xlink:href="anab-20181231.xsd#anab_RevenueRecognitionMilestoneMethodMilestonesAchievedDuringThePeriodAmount" xlink:label="loc_anab_RevenueRecognitionMilestoneMethodMilestonesAchievedDuringThePeriodAmount_C83C5852A596917EC81AE924A482CFE3" xlink:type="locator" />
    <link:definitionArc order="8" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CollaborativeArrangementsAndNoncollaborativeArrangementTransactionsLineItems_D531020A6B6A9ED6904CE924A48048F4" xlink:to="loc_anab_RevenueRecognitionMilestoneMethodMilestonesAchievedDuringThePeriodAmount_C83C5852A596917EC81AE924A482CFE3" xlink:type="arc" />
    <link:loc xlink:href="anab-20181231.xsd#anab_RevenueRecognitionMilestoneMethodNumberOfMilestonesAchievedDuringPeriod" xlink:label="loc_anab_RevenueRecognitionMilestoneMethodNumberOfMilestonesAchievedDuringPeriod_8D6AE7F0928BA00B1459E924A483CE2D" xlink:type="locator" />
    <link:definitionArc order="9" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CollaborativeArrangementsAndNoncollaborativeArrangementTransactionsLineItems_D531020A6B6A9ED6904CE924A48048F4" xlink:to="loc_anab_RevenueRecognitionMilestoneMethodNumberOfMilestonesAchievedDuringPeriod_8D6AE7F0928BA00B1459E924A483CE2D" xlink:type="arc" />
    <link:loc xlink:href="anab-20181231.xsd#anab_RevenueRecognitionMilestoneMethodResearchAndDevelopmentServicesRevenueRecognized" xlink:label="loc_anab_RevenueRecognitionMilestoneMethodResearchAndDevelopmentServicesRevenueRecognized_AD044118C42E4E28C77BE924A483D8C0" xlink:type="locator" />
    <link:definitionArc order="10" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CollaborativeArrangementsAndNoncollaborativeArrangementTransactionsLineItems_D531020A6B6A9ED6904CE924A48048F4" xlink:to="loc_anab_RevenueRecognitionMilestoneMethodResearchAndDevelopmentServicesRevenueRecognized_AD044118C42E4E28C77BE924A483D8C0" xlink:type="arc" />
    <link:loc xlink:href="anab-20181231.xsd#anab_RevenueRecognitionMilestoneMethodAmortizationOfUpfrontFeeRevenueRecognized" xlink:label="loc_anab_RevenueRecognitionMilestoneMethodAmortizationOfUpfrontFeeRevenueRecognized_40ECAC7146D38F26FF2CE924A4838553" xlink:type="locator" />
    <link:definitionArc order="11" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CollaborativeArrangementsAndNoncollaborativeArrangementTransactionsLineItems_D531020A6B6A9ED6904CE924A48048F4" xlink:to="loc_anab_RevenueRecognitionMilestoneMethodAmortizationOfUpfrontFeeRevenueRecognized_40ECAC7146D38F26FF2CE924A4838553" xlink:type="arc" />
    <link:loc xlink:href="anab-20181231.xsd#anab_RevenueRecognitionMilestoneMethodMaximumRevenuePerMilestone" xlink:label="loc_anab_RevenueRecognitionMilestoneMethodMaximumRevenuePerMilestone_AD5CD2F811FD5FE3A273E924A484B9EB" xlink:type="locator" />
    <link:definitionArc order="12" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CollaborativeArrangementsAndNoncollaborativeArrangementTransactionsLineItems_D531020A6B6A9ED6904CE924A48048F4" xlink:to="loc_anab_RevenueRecognitionMilestoneMethodMaximumRevenuePerMilestone_AD5CD2F811FD5FE3A273E924A484B9EB" xlink:type="arc" />
    <link:loc xlink:href="anab-20181231.xsd#anab_RevenueRecognizedMilestoneMethodMilestonePaymentEarned" xlink:label="loc_anab_RevenueRecognizedMilestoneMethodMilestonePaymentEarned_F3D7C18B422AE88EC823E924A484F40C" xlink:type="locator" />
    <link:definitionArc order="13" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CollaborativeArrangementsAndNoncollaborativeArrangementTransactionsLineItems_D531020A6B6A9ED6904CE924A48048F4" xlink:to="loc_anab_RevenueRecognizedMilestoneMethodMilestonePaymentEarned_F3D7C18B422AE88EC823E924A484F40C" xlink:type="arc" />
    <link:loc xlink:href="anab-20181231.xsd#anab_RevenueRecognitionMilestoneMethodMilestonesAchievedDuringThePeriod" xlink:label="loc_anab_RevenueRecognitionMilestoneMethodMilestonesAchievedDuringThePeriod_9F5280118B1EAA91A8EDE98322F7FDB3" xlink:type="locator" />
    <link:definitionArc order="14" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CollaborativeArrangementsAndNoncollaborativeArrangementTransactionsLineItems_D531020A6B6A9ED6904CE924A48048F4" xlink:to="loc_anab_RevenueRecognitionMilestoneMethodMilestonesAchievedDuringThePeriod_9F5280118B1EAA91A8EDE98322F7FDB3" 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/CommitmentsAndContingenciesLicensingAgreementsDetails" xlink:type="extended">
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_FiniteLivedIntangibleAssetsLineItems" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetsLineItems_91A0024F65581802C223E8556141CFE7" xlink:type="locator" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_ScheduleOfFiniteLivedIntangibleAssetsTable" xlink:label="loc_us-gaap_ScheduleOfFiniteLivedIntangibleAssetsTable_264A722247592F276AA9E855613FD768" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsLineItems_91A0024F65581802C223E8556141CFE7" xlink:to="loc_us-gaap_ScheduleOfFiniteLivedIntangibleAssetsTable_264A722247592F276AA9E855613FD768" 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_CreditFacilityAxis" xlink:label="loc_us-gaap_CreditFacilityAxis_33E34F611864DABEB64EE8556140241D" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfFiniteLivedIntangibleAssetsTable_264A722247592F276AA9E855613FD768" xlink:to="loc_us-gaap_CreditFacilityAxis_33E34F611864DABEB64EE8556140241D" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_CreditFacilityDomain" xlink:label="loc_us-gaap_CreditFacilityDomain_45FFC24424EA9B0C334AE85561401B2D_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_CreditFacilityAxis_33E34F611864DABEB64EE8556140241D" xlink:to="loc_us-gaap_CreditFacilityDomain_45FFC24424EA9B0C334AE85561401B2D_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_CreditFacilityDomain" xlink:label="loc_us-gaap_CreditFacilityDomain_45FFC24424EA9B0C334AE85561401B2D" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_CreditFacilityAxis_33E34F611864DABEB64EE8556140241D" xlink:to="loc_us-gaap_CreditFacilityDomain_45FFC24424EA9B0C334AE85561401B2D" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_StandbyLettersOfCreditMember" xlink:label="loc_us-gaap_StandbyLettersOfCreditMember_D6A501C029E321DA2B46E8556141C323" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CreditFacilityDomain_45FFC24424EA9B0C334AE85561401B2D" xlink:to="loc_us-gaap_StandbyLettersOfCreditMember_D6A501C029E321DA2B46E8556141C323" xlink:type="arc" />
    <link:loc xlink:href="anab-20181231.xsd#anab_CollaborationLicenseAgreementMaximumTerm" xlink:label="loc_anab_CollaborationLicenseAgreementMaximumTerm_79B2051C9B52453C14B7E8556142973F" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsLineItems_91A0024F65581802C223E8556141CFE7" xlink:to="loc_anab_CollaborationLicenseAgreementMaximumTerm_79B2051C9B52453C14B7E8556142973F" xlink:type="arc" />
    <link:loc xlink:href="anab-20181231.xsd#anab_CollaborationLicenseAgreementUpfrontMilestoneAndRoyaltyExpense" xlink:label="loc_anab_CollaborationLicenseAgreementUpfrontMilestoneAndRoyaltyExpense_29684388EB9A48E32156E85561421E9F" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsLineItems_91A0024F65581802C223E8556141CFE7" xlink:to="loc_anab_CollaborationLicenseAgreementUpfrontMilestoneAndRoyaltyExpense_29684388EB9A48E32156E85561421E9F" xlink:type="arc" />
    <link:loc xlink:href="anab-20181231.xsd#anab_PaymentsForUpfrontMilestoneAndRoyaltyPayments" xlink:label="loc_anab_PaymentsForUpfrontMilestoneAndRoyaltyPayments_2918FC9D41708ABF63A8E85561430EA6" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsLineItems_91A0024F65581802C223E8556141CFE7" xlink:to="loc_anab_PaymentsForUpfrontMilestoneAndRoyaltyPayments_2918FC9D41708ABF63A8E85561430EA6" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_OtherCommitmentDueInNextTwelveMonths" xlink:label="loc_us-gaap_OtherCommitmentDueInNextTwelveMonths_815C29076B0A108C22D2E85561438BCC" xlink:type="locator" />
    <link:definitionArc order="4" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsLineItems_91A0024F65581802C223E8556141CFE7" xlink:to="loc_us-gaap_OtherCommitmentDueInNextTwelveMonths_815C29076B0A108C22D2E85561438BCC" xlink:type="arc" />
    <link:loc xlink:href="anab-20181231.xsd#anab_OtherCommitmentsDueAfterYearOne" xlink:label="loc_anab_OtherCommitmentsDueAfterYearOne_B0B2D4D349F142AE7868E85561436AF0" xlink:type="locator" />
    <link:definitionArc order="5" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsLineItems_91A0024F65581802C223E8556141CFE7" xlink:to="loc_anab_OtherCommitmentsDueAfterYearOne_B0B2D4D349F142AE7868E85561436AF0" xlink:type="arc" />
    <link:loc xlink:href="anab-20181231.xsd#anab_CollaborationLicenseAgreementObligationPayablePeriod" xlink:label="loc_anab_CollaborationLicenseAgreementObligationPayablePeriod_E1E085EB84EE3C0FA64EE85561448532" xlink:type="locator" />
    <link:definitionArc order="6" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsLineItems_91A0024F65581802C223E8556141CFE7" xlink:to="loc_anab_CollaborationLicenseAgreementObligationPayablePeriod_E1E085EB84EE3C0FA64EE85561448532" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_LettersOfCreditOutstandingAmount" xlink:label="loc_us-gaap_LettersOfCreditOutstandingAmount_CC23C77800A0C2966E36E85561440977" xlink:type="locator" />
    <link:definitionArc order="7" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsLineItems_91A0024F65581802C223E8556141CFE7" xlink:to="loc_us-gaap_LettersOfCreditOutstandingAmount_CC23C77800A0C2966E36E85561440977" xlink:type="arc" />
  </link:definitionLink>
  <link:definitionLink xlink:role="http://www.anaptysbio.com/role/CommitmentsAndContingenciesOperatingLeasesDetails" 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_89A575FD16BA225F48E316F9CF01609D" 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_C1E4FD963448F8E8B23C16F9CEFA87A8" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_OperatingLeasedAssetsLineItems_89A575FD16BA225F48E316F9CF01609D" xlink:to="loc_us-gaap_ScheduleOfOperatingLeasedAssetsTable_C1E4FD963448F8E8B23C16F9CEFA87A8" 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_6E9C8E75C4DEC6638A9F16F9CEFBDE3B" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfOperatingLeasedAssetsTable_C1E4FD963448F8E8B23C16F9CEFA87A8" xlink:to="loc_us-gaap_LeaseArrangementTypeAxis_6E9C8E75C4DEC6638A9F16F9CEFBDE3B" 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_58990AF4F947A205D3CF16F9CEFBBE59_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_LeaseArrangementTypeAxis_6E9C8E75C4DEC6638A9F16F9CEFBDE3B" xlink:to="loc_us-gaap_LeaseArrangementTypeDomain_58990AF4F947A205D3CF16F9CEFBBE59_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_58990AF4F947A205D3CF16F9CEFBBE59" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_LeaseArrangementTypeAxis_6E9C8E75C4DEC6638A9F16F9CEFBDE3B" xlink:to="loc_us-gaap_LeaseArrangementTypeDomain_58990AF4F947A205D3CF16F9CEFBBE59" xlink:type="arc" />
    <link:loc xlink:href="anab-20181231.xsd#anab_NewSubleaseAgreementMember" xlink:label="loc_anab_NewSubleaseAgreementMember_94B2DAB2929D1B26FF9216F9CEFBC793" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LeaseArrangementTypeDomain_58990AF4F947A205D3CF16F9CEFBBE59" xlink:to="loc_anab_NewSubleaseAgreementMember_94B2DAB2929D1B26FF9216F9CEFBC793" xlink:type="arc" />
    <link:loc xlink:href="anab-20181231.xsd#anab_OriginalLeaseAgreementMember" xlink:label="loc_anab_OriginalLeaseAgreementMember_914C17E215B216EECE7A16F9CEFCB0E2" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LeaseArrangementTypeDomain_58990AF4F947A205D3CF16F9CEFBBE59" xlink:to="loc_anab_OriginalLeaseAgreementMember_914C17E215B216EECE7A16F9CEFCB0E2" 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_0AA1F25C3B1AC07F201A16F9CF016F2A" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_OperatingLeasedAssetsLineItems_89A575FD16BA225F48E316F9CF01609D" xlink:to="loc_us-gaap_LesseeOperatingLeaseTermOfContract_0AA1F25C3B1AC07F201A16F9CF016F2A" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_AreaOfRealEstateProperty" xlink:label="loc_us-gaap_AreaOfRealEstateProperty_32B7F86DD0296DA7AD8E1707C0D95266" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_OperatingLeasedAssetsLineItems_89A575FD16BA225F48E316F9CF01609D" xlink:to="loc_us-gaap_AreaOfRealEstateProperty_32B7F86DD0296DA7AD8E1707C0D95266" xlink:type="arc" />
    <link:loc xlink:href="anab-20181231.xsd#anab_LesseeOperatingLeaseOneYearRenewalOptionsNumber" xlink:label="loc_anab_LesseeOperatingLeaseOneYearRenewalOptionsNumber_D5C24C0B1EDE559E350916F9CF02D3E5" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_OperatingLeasedAssetsLineItems_89A575FD16BA225F48E316F9CF01609D" xlink:to="loc_anab_LesseeOperatingLeaseOneYearRenewalOptionsNumber_D5C24C0B1EDE559E350916F9CF02D3E5" 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_A3C803D8D7D398D0A8E716F9CF02F5B3" xlink:type="locator" />
    <link:definitionArc order="4" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_OperatingLeasedAssetsLineItems_89A575FD16BA225F48E316F9CF01609D" xlink:to="loc_us-gaap_LesseeOperatingLeaseRenewalTerm_A3C803D8D7D398D0A8E716F9CF02F5B3" 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/ConsolidatedStatementsOfConvertiblePreferredStockAndStockholdersEquityDeficit" xlink:type="extended">
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_StatementLineItems" xlink:label="loc_us-gaap_StatementLineItems_4748EF70D7FCFCAFAEBF0CFC82D9B3B5" xlink:type="locator" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_StatementTable" xlink:label="loc_us-gaap_StatementTable_F4665FABA078D11F16490CFC82C83C6B" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_StatementLineItems_4748EF70D7FCFCAFAEBF0CFC82D9B3B5" xlink:to="loc_us-gaap_StatementTable_F4665FABA078D11F16490CFC82C83C6B" 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_4798D63A0B8DB2393C0F0CFC82D0F107" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_StatementTable_F4665FABA078D11F16490CFC82C83C6B" xlink:to="loc_us-gaap_StatementEquityComponentsAxis_4798D63A0B8DB2393C0F0CFC82D0F107" 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_EA549D36FE04B4E4960F0CFC82D0189B_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_StatementEquityComponentsAxis_4798D63A0B8DB2393C0F0CFC82D0F107" xlink:to="loc_us-gaap_EquityComponentDomain_EA549D36FE04B4E4960F0CFC82D0189B_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_EA549D36FE04B4E4960F0CFC82D0189B" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_StatementEquityComponentsAxis_4798D63A0B8DB2393C0F0CFC82D0F107" xlink:to="loc_us-gaap_EquityComponentDomain_EA549D36FE04B4E4960F0CFC82D0189B" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_PreferredStockMember" xlink:label="loc_us-gaap_PreferredStockMember_93266A912CB8E285BBB90CFC82D11F64" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityComponentDomain_EA549D36FE04B4E4960F0CFC82D0189B" xlink:to="loc_us-gaap_PreferredStockMember_93266A912CB8E285BBB90CFC82D11F64" 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_0704C775927843B3B9C50CFC82D2933A" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityComponentDomain_EA549D36FE04B4E4960F0CFC82D0189B" xlink:to="loc_us-gaap_CommonStockMember_0704C775927843B3B9C50CFC82D2933A" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_AdditionalPaidInCapitalMember" xlink:label="loc_us-gaap_AdditionalPaidInCapitalMember_FA4512E35874A49992BE0CFC82D62220" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityComponentDomain_EA549D36FE04B4E4960F0CFC82D0189B" xlink:to="loc_us-gaap_AdditionalPaidInCapitalMember_FA4512E35874A49992BE0CFC82D62220" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_AccumulatedOtherComprehensiveIncomeMember" xlink:label="loc_us-gaap_AccumulatedOtherComprehensiveIncomeMember_2034A92963C5714CC6CA0CFC82D6C6A6" xlink:type="locator" />
    <link:definitionArc order="4" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityComponentDomain_EA549D36FE04B4E4960F0CFC82D0189B" xlink:to="loc_us-gaap_AccumulatedOtherComprehensiveIncomeMember_2034A92963C5714CC6CA0CFC82D6C6A6" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_RetainedEarningsMember" xlink:label="loc_us-gaap_RetainedEarningsMember_109215829828B78735150CFC82D75E77" xlink:type="locator" />
    <link:definitionArc order="5" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityComponentDomain_EA549D36FE04B4E4960F0CFC82D0189B" xlink:to="loc_us-gaap_RetainedEarningsMember_109215829828B78735150CFC82D75E77" 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_15EA59137A744E8DBED40CFC82D7B2AB" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_StatementTable_F4665FABA078D11F16490CFC82C83C6B" xlink:to="loc_us-gaap_StatementClassOfStockAxis_15EA59137A744E8DBED40CFC82D7B2AB" 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_B78ACF5589F8ABBA95F70CFC82D78F89_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_StatementClassOfStockAxis_15EA59137A744E8DBED40CFC82D7B2AB" xlink:to="loc_us-gaap_ClassOfStockDomain_B78ACF5589F8ABBA95F70CFC82D78F89_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_B78ACF5589F8ABBA95F70CFC82D78F89" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_StatementClassOfStockAxis_15EA59137A744E8DBED40CFC82D7B2AB" xlink:to="loc_us-gaap_ClassOfStockDomain_B78ACF5589F8ABBA95F70CFC82D78F89" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_SeriesBPreferredStockMember" xlink:label="loc_us-gaap_SeriesBPreferredStockMember_737802FA3BC7602789CC0CFC82D88A11" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockDomain_B78ACF5589F8ABBA95F70CFC82D78F89" xlink:to="loc_us-gaap_SeriesBPreferredStockMember_737802FA3BC7602789CC0CFC82D88A11" 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_93E7B18FB2302F8ED4BD0CFC82D8E179" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockDomain_B78ACF5589F8ABBA95F70CFC82D78F89" xlink:to="loc_us-gaap_SeriesCPreferredStockMember_93E7B18FB2302F8ED4BD0CFC82D8E179" xlink:type="arc" />
    <link:loc xlink:href="anab-20181231.xsd#anab_SeriesC1PreferredStockMember" xlink:label="loc_anab_SeriesC1PreferredStockMember_D351559E7DBE318C74090CFC82D8EE2F" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockDomain_B78ACF5589F8ABBA95F70CFC82D78F89" xlink:to="loc_anab_SeriesC1PreferredStockMember_D351559E7DBE318C74090CFC82D8EE2F" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_SeriesDPreferredStockMember" xlink:label="loc_us-gaap_SeriesDPreferredStockMember_6E477DBC1FD649E559630CFC82D963EC" xlink:type="locator" />
    <link:definitionArc order="4" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockDomain_B78ACF5589F8ABBA95F70CFC82D78F89" xlink:to="loc_us-gaap_SeriesDPreferredStockMember_6E477DBC1FD649E559630CFC82D963EC" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_IncreaseDecreaseInStockholdersEquityRollForward" xlink:label="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_0DEA8CF23E03CE4358CB0CFC82DEA2DD" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_4748EF70D7FCFCAFAEBF0CFC82D9B3B5" xlink:to="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_0DEA8CF23E03CE4358CB0CFC82DEA2DD" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_StockholdersEquity" xlink:label="loc_us-gaap_StockholdersEquity_C488FEE1A49BD9812B3D0CFC82DE253E" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_0DEA8CF23E03CE4358CB0CFC82DEA2DD" xlink:to="loc_us-gaap_StockholdersEquity_C488FEE1A49BD9812B3D0CFC82DE253E" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_SharesOutstanding" xlink:label="loc_us-gaap_SharesOutstanding_F73E0DBB4BF4514F942D0CFC82DF75D1" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_0DEA8CF23E03CE4358CB0CFC82DEA2DD" xlink:to="loc_us-gaap_SharesOutstanding_F73E0DBB4BF4514F942D0CFC82DF75D1" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_StockIssuedDuringPeriodValueNewIssues" xlink:label="loc_us-gaap_StockIssuedDuringPeriodValueNewIssues_098742B9459E228A44020CFC82DFE769" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_0DEA8CF23E03CE4358CB0CFC82DEA2DD" xlink:to="loc_us-gaap_StockIssuedDuringPeriodValueNewIssues_098742B9459E228A44020CFC82DFE769" 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_4C187263D0E3B5D1152F0CFC82DFB22E" xlink:type="locator" />
    <link:definitionArc order="4" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_0DEA8CF23E03CE4358CB0CFC82DEA2DD" xlink:to="loc_us-gaap_StockIssuedDuringPeriodSharesNewIssues_4C187263D0E3B5D1152F0CFC82DFB22E" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_StockIssuedDuringPeriodValueStockOptionsExercised" xlink:label="loc_us-gaap_StockIssuedDuringPeriodValueStockOptionsExercised_4E0DD8BD2B8F2C9D665D0CFC82E0D952" xlink:type="locator" />
    <link:definitionArc order="5" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_0DEA8CF23E03CE4358CB0CFC82DEA2DD" xlink:to="loc_us-gaap_StockIssuedDuringPeriodValueStockOptionsExercised_4E0DD8BD2B8F2C9D665D0CFC82E0D952" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_StockIssuedDuringPeriodSharesStockOptionsExercised" xlink:label="loc_us-gaap_StockIssuedDuringPeriodSharesStockOptionsExercised_54FCCF2D754F37694BBD0CFC82E05E49" xlink:type="locator" />
    <link:definitionArc order="6" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_0DEA8CF23E03CE4358CB0CFC82DEA2DD" xlink:to="loc_us-gaap_StockIssuedDuringPeriodSharesStockOptionsExercised_54FCCF2D754F37694BBD0CFC82E05E49" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_StockRepurchasedDuringPeriodValue" xlink:label="loc_us-gaap_StockRepurchasedDuringPeriodValue_055595D9FE36A57249340CFC82E00E5E" xlink:type="locator" />
    <link:definitionArc order="7" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_0DEA8CF23E03CE4358CB0CFC82DEA2DD" xlink:to="loc_us-gaap_StockRepurchasedDuringPeriodValue_055595D9FE36A57249340CFC82E00E5E" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_StockRepurchasedDuringPeriodShares" xlink:label="loc_us-gaap_StockRepurchasedDuringPeriodShares_66CB4DBBD14CF920AA350CFC82E0F3C2" xlink:type="locator" />
    <link:definitionArc order="8" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_0DEA8CF23E03CE4358CB0CFC82DEA2DD" xlink:to="loc_us-gaap_StockRepurchasedDuringPeriodShares_66CB4DBBD14CF920AA350CFC82E0F3C2" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_AdjustmentsToAdditionalPaidInCapitalStockIssuedIssuanceCosts" xlink:label="loc_us-gaap_AdjustmentsToAdditionalPaidInCapitalStockIssuedIssuanceCosts_5B591546FD91C76D15A80CFC82E091AE" xlink:type="locator" />
    <link:definitionArc order="9" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_0DEA8CF23E03CE4358CB0CFC82DEA2DD" xlink:to="loc_us-gaap_AdjustmentsToAdditionalPaidInCapitalStockIssuedIssuanceCosts_5B591546FD91C76D15A80CFC82E091AE" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_StockIssuedDuringPeriodValueConversionOfConvertibleSecurities" xlink:label="loc_us-gaap_StockIssuedDuringPeriodValueConversionOfConvertibleSecurities_7B50BD318214BA3508910CFC82E0F24E" xlink:type="locator" />
    <link:definitionArc order="10" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_0DEA8CF23E03CE4358CB0CFC82DEA2DD" xlink:to="loc_us-gaap_StockIssuedDuringPeriodValueConversionOfConvertibleSecurities_7B50BD318214BA3508910CFC82E0F24E" 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_D5BCE42137839E3A92F60CFC82E11DBD" xlink:type="locator" />
    <link:definitionArc order="11" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_0DEA8CF23E03CE4358CB0CFC82DEA2DD" xlink:to="loc_us-gaap_StockIssuedDuringPeriodSharesConversionOfConvertibleSecurities_D5BCE42137839E3A92F60CFC82E11DBD" xlink:type="arc" />
    <link:loc xlink:href="anab-20181231.xsd#anab_StockIssuedDuringPeriodValueDueToWarrantsExercised" xlink:label="loc_anab_StockIssuedDuringPeriodValueDueToWarrantsExercised_4F91498D3D12FB63F47D0CFC82E1B945" xlink:type="locator" />
    <link:definitionArc order="12" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_0DEA8CF23E03CE4358CB0CFC82DEA2DD" xlink:to="loc_anab_StockIssuedDuringPeriodValueDueToWarrantsExercised_4F91498D3D12FB63F47D0CFC82E1B945" xlink:type="arc" />
    <link:loc xlink:href="anab-20181231.xsd#anab_StockIssuedDuringPeriodSharesDueToWarrantsExercised" xlink:label="loc_anab_StockIssuedDuringPeriodSharesDueToWarrantsExercised_FBE5AD52AAF48058AFCA0CFC82E1F060" xlink:type="locator" />
    <link:definitionArc order="13" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_0DEA8CF23E03CE4358CB0CFC82DEA2DD" xlink:to="loc_anab_StockIssuedDuringPeriodSharesDueToWarrantsExercised_FBE5AD52AAF48058AFCA0CFC82E1F060" xlink:type="arc" />
    <link:loc xlink:href="anab-20181231.xsd#anab_AdjustmentsToAdditionalPaidInCapitalWarrantsReclassified" xlink:label="loc_anab_AdjustmentsToAdditionalPaidInCapitalWarrantsReclassified_BAF9BC986AF836BAADD60CFC82E12889" xlink:type="locator" />
    <link:definitionArc order="14" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_0DEA8CF23E03CE4358CB0CFC82DEA2DD" xlink:to="loc_anab_AdjustmentsToAdditionalPaidInCapitalWarrantsReclassified_BAF9BC986AF836BAADD60CFC82E12889" xlink:type="arc" />
    <link:loc xlink:href="anab-20181231.xsd#anab_AdjustmentstoAdditionalPaidinCapitalForfeitureRateAdjustment" xlink:label="loc_anab_AdjustmentstoAdditionalPaidinCapitalForfeitureRateAdjustment_60579F91CAF655BFB8140CFC82E7B71F" xlink:type="locator" />
    <link:definitionArc order="15" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_0DEA8CF23E03CE4358CB0CFC82DEA2DD" xlink:to="loc_anab_AdjustmentstoAdditionalPaidinCapitalForfeitureRateAdjustment_60579F91CAF655BFB8140CFC82E7B71F" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_AdjustmentsToAdditionalPaidInCapitalShareBasedCompensationStockOptionsRequisiteServicePeriodRecognition" xlink:label="loc_us-gaap_AdjustmentsToAdditionalPaidInCapitalShareBasedCompensationStockOptionsRequisiteServicePeriodRecognition_96F54AB34325159EF9390CFC82E72E03" xlink:type="locator" />
    <link:definitionArc order="16" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_0DEA8CF23E03CE4358CB0CFC82DEA2DD" xlink:to="loc_us-gaap_AdjustmentsToAdditionalPaidInCapitalShareBasedCompensationStockOptionsRequisiteServicePeriodRecognition_96F54AB34325159EF9390CFC82E72E03" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_OtherComprehensiveIncomeLossNetOfTax" xlink:label="loc_us-gaap_OtherComprehensiveIncomeLossNetOfTax_0C72E7AC92CAF92BDF4F0CFC82E7B33E" xlink:type="locator" />
    <link:definitionArc order="17" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_0DEA8CF23E03CE4358CB0CFC82DEA2DD" xlink:to="loc_us-gaap_OtherComprehensiveIncomeLossNetOfTax_0C72E7AC92CAF92BDF4F0CFC82E7B33E" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_NetIncomeLoss" xlink:label="loc_us-gaap_NetIncomeLoss_347A0458180CA25D5FC50CFC82E71C7B" xlink:type="locator" />
    <link:definitionArc order="18" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_0DEA8CF23E03CE4358CB0CFC82DEA2DD" xlink:to="loc_us-gaap_NetIncomeLoss_347A0458180CA25D5FC50CFC82E71C7B" xlink:type="arc" />
  </link:definitionLink>
  <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_2EF0AFE060E8730B14A70CFCB25D2106" 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_2C3B219F690A5B3102CE0CFCB25AE9AF" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_ClassOfWarrantOrRightLineItems_2EF0AFE060E8730B14A70CFCB25D2106" xlink:to="loc_us-gaap_ClassOfWarrantOrRightTable_2C3B219F690A5B3102CE0CFCB25AE9AF" 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_5B1CFEBBB89659BCC4F60CFCB25B318E" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ClassOfWarrantOrRightTable_2C3B219F690A5B3102CE0CFCB25AE9AF" xlink:to="loc_us-gaap_SubsidiarySaleOfStockAxis_5B1CFEBBB89659BCC4F60CFCB25B318E" 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_2A40386F83ABB408A7C10CFCB25BD91E_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_SubsidiarySaleOfStockAxis_5B1CFEBBB89659BCC4F60CFCB25B318E" xlink:to="loc_us-gaap_SaleOfStockNameOfTransactionDomain_2A40386F83ABB408A7C10CFCB25BD91E_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_2A40386F83ABB408A7C10CFCB25BD91E" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_SubsidiarySaleOfStockAxis_5B1CFEBBB89659BCC4F60CFCB25B318E" xlink:to="loc_us-gaap_SaleOfStockNameOfTransactionDomain_2A40386F83ABB408A7C10CFCB25BD91E" 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_85BF9A27EBDCA004FA490CFCB25BBBB5" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SaleOfStockNameOfTransactionDomain_2A40386F83ABB408A7C10CFCB25BD91E" xlink:to="loc_us-gaap_IPOMember_85BF9A27EBDCA004FA490CFCB25BBBB5" 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_5B56503625ED442B44EC0CFCB25BC320" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SaleOfStockNameOfTransactionDomain_2A40386F83ABB408A7C10CFCB25BD91E" xlink:to="loc_us-gaap_OverAllotmentOptionMember_5B56503625ED442B44EC0CFCB25BC320" 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_FFC4A6D3EB96BF1263E40CFCB25C5CC7" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ClassOfWarrantOrRightTable_2C3B219F690A5B3102CE0CFCB25AE9AF" xlink:to="loc_us-gaap_StatementEquityComponentsAxis_FFC4A6D3EB96BF1263E40CFCB25C5CC7" 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_3BA5455DAF28BACC916E0CFCB25CB3E1_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_StatementEquityComponentsAxis_FFC4A6D3EB96BF1263E40CFCB25C5CC7" xlink:to="loc_us-gaap_EquityComponentDomain_3BA5455DAF28BACC916E0CFCB25CB3E1_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_3BA5455DAF28BACC916E0CFCB25CB3E1" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_StatementEquityComponentsAxis_FFC4A6D3EB96BF1263E40CFCB25C5CC7" xlink:to="loc_us-gaap_EquityComponentDomain_3BA5455DAF28BACC916E0CFCB25CB3E1" 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_713549691E28D96E291E0CFCB25C97B4" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityComponentDomain_3BA5455DAF28BACC916E0CFCB25CB3E1" xlink:to="loc_us-gaap_CommonStockMember_713549691E28D96E291E0CFCB25C97B4" 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_A4EC21EDAC6CE88CEB8A0CFCB25D4633" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ClassOfWarrantOrRightTable_2C3B219F690A5B3102CE0CFCB25AE9AF" xlink:to="loc_us-gaap_StatementClassOfStockAxis_A4EC21EDAC6CE88CEB8A0CFCB25D4633" 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_184E47E2DAAF43DA10E10CFCB25D09DA_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_StatementClassOfStockAxis_A4EC21EDAC6CE88CEB8A0CFCB25D4633" xlink:to="loc_us-gaap_ClassOfStockDomain_184E47E2DAAF43DA10E10CFCB25D09DA_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_184E47E2DAAF43DA10E10CFCB25D09DA" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_StatementClassOfStockAxis_A4EC21EDAC6CE88CEB8A0CFCB25D4633" xlink:to="loc_us-gaap_ClassOfStockDomain_184E47E2DAAF43DA10E10CFCB25D09DA" 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_37EF41889CDD372AFDB00CFCB25D4D69" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockDomain_184E47E2DAAF43DA10E10CFCB25D09DA" xlink:to="loc_us-gaap_ConvertiblePreferredStockMember_37EF41889CDD372AFDB00CFCB25D4D69" 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_4B193EEA428885468C830CFCB25D02B8" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfWarrantOrRightLineItems_2EF0AFE060E8730B14A70CFCB25D2106" xlink:to="loc_us-gaap_StockIssuedDuringPeriodSharesNewIssues_4B193EEA428885468C830CFCB25D02B8" 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_139B8106395BA141841F0CFCB25EC4D1" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfWarrantOrRightLineItems_2EF0AFE060E8730B14A70CFCB25D2106" xlink:to="loc_us-gaap_SharesIssuedPricePerShare_139B8106395BA141841F0CFCB25EC4D1" 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_7AE29E55A8697D2FF3D90CFCB25E8C02" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfWarrantOrRightLineItems_2EF0AFE060E8730B14A70CFCB25D2106" xlink:to="loc_us-gaap_ProceedsFromIssuanceInitialPublicOffering_7AE29E55A8697D2FF3D90CFCB25E8C02" 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_CF816C1FF9307B8ED2ED0CFCB25E3D5F" xlink:type="locator" />
    <link:definitionArc order="4" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfWarrantOrRightLineItems_2EF0AFE060E8730B14A70CFCB25D2106" xlink:to="loc_us-gaap_StockIssuedDuringPeriodSharesConversionOfConvertibleSecurities_CF816C1FF9307B8ED2ED0CFCB25E3D5F" 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_77F3F583A69EE9D368EB0CFCB25E7A76" xlink:type="locator" />
    <link:definitionArc order="5" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfWarrantOrRightLineItems_2EF0AFE060E8730B14A70CFCB25D2106" xlink:to="loc_us-gaap_ClassOfWarrantOrRightNumberOfSecuritiesCalledByWarrantsOrRights_77F3F583A69EE9D368EB0CFCB25E7A76" 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_98F168B4AE9DAF41C00B0CFCB25E5218" xlink:type="locator" />
    <link:definitionArc order="6" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfWarrantOrRightLineItems_2EF0AFE060E8730B14A70CFCB25D2106" xlink:to="loc_us-gaap_StockholdersEquityNoteStockSplitConversionRatio1_98F168B4AE9DAF41C00B0CFCB25E5218" 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_7BFFD56892EA0CA7CB050CFCB25F1F54" xlink:type="locator" />
    <link:definitionArc order="7" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfWarrantOrRightLineItems_2EF0AFE060E8730B14A70CFCB25D2106" xlink:to="loc_us-gaap_ProceedsFromIssuanceOfCommonStock_7BFFD56892EA0CA7CB050CFCB25F1F54" 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/EmployeeBenefitPlan" xlink:type="extended" />
  <link:definitionLink xlink:role="http://www.anaptysbio.com/role/EmployeeBenefitPlanDetails" 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_7E8F374855424959AAC513936DCB8B31" 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_C24D9828DB41ACDF3E9E13936DC974CC" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_7E8F374855424959AAC513936DCB8B31" xlink:to="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_C24D9828DB41ACDF3E9E13936DC974CC" 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_4F388488C54A4F6508B013936DCAB54F" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_C24D9828DB41ACDF3E9E13936DC974CC" xlink:to="loc_us-gaap_IncomeStatementLocationAxis_4F388488C54A4F6508B013936DCAB54F" 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_76DFF0410E594FBE8EA513936DCA6DB7_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_IncomeStatementLocationAxis_4F388488C54A4F6508B013936DCAB54F" xlink:to="loc_us-gaap_IncomeStatementLocationDomain_76DFF0410E594FBE8EA513936DCA6DB7_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_76DFF0410E594FBE8EA513936DCA6DB7" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_IncomeStatementLocationAxis_4F388488C54A4F6508B013936DCAB54F" xlink:to="loc_us-gaap_IncomeStatementLocationDomain_76DFF0410E594FBE8EA513936DCA6DB7" 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_A0BA66553F7EB5DE285C13936DCAEDA0" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncomeStatementLocationDomain_76DFF0410E594FBE8EA513936DCA6DB7" xlink:to="loc_us-gaap_ResearchAndDevelopmentExpenseMember_A0BA66553F7EB5DE285C13936DCAEDA0" 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_6C7D479DD2C1ABC750DB13936DCB5B86" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncomeStatementLocationDomain_76DFF0410E594FBE8EA513936DCA6DB7" xlink:to="loc_us-gaap_GeneralAndAdministrativeExpenseMember_6C7D479DD2C1ABC750DB13936DCB5B86" xlink:type="arc" />
    <link:loc xlink:href="anab-20181231.xsd#anab_SharebasedCompensationAndIssuanceOfStockAndWarrantsForServicesOrClaims" xlink:label="loc_anab_SharebasedCompensationAndIssuanceOfStockAndWarrantsForServicesOrClaims_3BC12F56B25F88C67A7A13936DCB7CB5" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_7E8F374855424959AAC513936DCB8B31" xlink:to="loc_anab_SharebasedCompensationAndIssuanceOfStockAndWarrantsForServicesOrClaims_3BC12F56B25F88C67A7A13936DCB7CB5" 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_5364FA61B2584EAA2885EE19539585D9" 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_94BCF3BC40594432E2E0EE195390BAA0" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_5364FA61B2584EAA2885EE19539585D9" xlink:to="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_94BCF3BC40594432E2E0EE195390BAA0" 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_141E646308C7B38B1638EE1953916161" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_94BCF3BC40594432E2E0EE195390BAA0" xlink:to="loc_us-gaap_PlanNameAxis_141E646308C7B38B1638EE1953916161" 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_A2CE1A490FAE3D386957EE195391CE92_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_PlanNameAxis_141E646308C7B38B1638EE1953916161" xlink:to="loc_us-gaap_PlanNameDomain_A2CE1A490FAE3D386957EE195391CE92_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_A2CE1A490FAE3D386957EE195391CE92" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_PlanNameAxis_141E646308C7B38B1638EE1953916161" xlink:to="loc_us-gaap_PlanNameDomain_A2CE1A490FAE3D386957EE195391CE92" xlink:type="arc" />
    <link:loc xlink:href="anab-20181231.xsd#anab_EquityIncentivePlan2017Member" xlink:label="loc_anab_EquityIncentivePlan2017Member_D4C840DB92282B556A90EE19539202E0" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PlanNameDomain_A2CE1A490FAE3D386957EE195391CE92" xlink:to="loc_anab_EquityIncentivePlan2017Member_D4C840DB92282B556A90EE19539202E0" xlink:type="arc" />
    <link:loc xlink:href="anab-20181231.xsd#anab_EmployeeStockPurchasePlan2017Member" xlink:label="loc_anab_EmployeeStockPurchasePlan2017Member_628D8B944848415D5F6FEE195392A8FC" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PlanNameDomain_A2CE1A490FAE3D386957EE195391CE92" xlink:to="loc_anab_EmployeeStockPurchasePlan2017Member_628D8B944848415D5F6FEE195392A8FC" 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_878789B518E1FE547F25EE1953923CE2" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_94BCF3BC40594432E2E0EE195390BAA0" xlink:to="loc_us-gaap_AwardTypeAxis_878789B518E1FE547F25EE1953923CE2" 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_89541136F036E47768D2EE19539366A1_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_AwardTypeAxis_878789B518E1FE547F25EE1953923CE2" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_89541136F036E47768D2EE19539366A1_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_89541136F036E47768D2EE19539366A1" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_AwardTypeAxis_878789B518E1FE547F25EE1953923CE2" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_89541136F036E47768D2EE19539366A1" 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_3E15B7AC115C8B495028EE1953935116" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_89541136F036E47768D2EE19539366A1" xlink:to="loc_us-gaap_EmployeeStockMember_3E15B7AC115C8B495028EE1953935116" xlink:type="arc" />
    <link:loc xlink:href="anab-20181231.xsd#anab_EmployeeAndNonemployeeStockOptionsMember" xlink:label="loc_anab_EmployeeAndNonemployeeStockOptionsMember_E389069AA756F2B83A0AEE195394FFD0" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_89541136F036E47768D2EE19539366A1" xlink:to="loc_anab_EmployeeAndNonemployeeStockOptionsMember_E389069AA756F2B83A0AEE195394FFD0" 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_B68645CF156E3F90434CEE195394944D" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_89541136F036E47768D2EE19539366A1" xlink:to="loc_us-gaap_EmployeeStockOptionMember_B68645CF156E3F90434CEE195394944D" 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_C564A309A678E1F84BF4EE195394C593" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_94BCF3BC40594432E2E0EE195390BAA0" xlink:to="loc_us-gaap_TitleOfIndividualAxis_C564A309A678E1F84BF4EE195394C593" 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_DEE8FE465F50247B0191EE195395A7B2_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_TitleOfIndividualAxis_C564A309A678E1F84BF4EE195394C593" xlink:to="loc_us-gaap_TitleOfIndividualWithRelationshipToEntityDomain_DEE8FE465F50247B0191EE195395A7B2_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_DEE8FE465F50247B0191EE195395A7B2" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_TitleOfIndividualAxis_C564A309A678E1F84BF4EE195394C593" xlink:to="loc_us-gaap_TitleOfIndividualWithRelationshipToEntityDomain_DEE8FE465F50247B0191EE195395A7B2" 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_1E3FDEBF824E0CFAAE33EE195395D0AA" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TitleOfIndividualWithRelationshipToEntityDomain_DEE8FE465F50247B0191EE195395A7B2" xlink:to="loc_us-gaap_DirectorMember_1E3FDEBF824E0CFAAE33EE195395D0AA" xlink:type="arc" />
    <link:loc xlink:href="anab-20181231.xsd#anab_CommonStockCapitalSharesReservedForFutureIssuanceAnnualIncreasePercentOfAggregateSharesOutstanding" xlink:label="loc_anab_CommonStockCapitalSharesReservedForFutureIssuanceAnnualIncreasePercentOfAggregateSharesOutstanding_3CDA6EBDAFCBBD7B285FEE1953963C9E" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_5364FA61B2584EAA2885EE19539585D9" xlink:to="loc_anab_CommonStockCapitalSharesReservedForFutureIssuanceAnnualIncreasePercentOfAggregateSharesOutstanding_3CDA6EBDAFCBBD7B285FEE1953963C9E" xlink:type="arc" />
    <link:loc xlink:href="anab-20181231.xsd#anab_CommonStockCapitalSharesReservedForFutureIssuanceIncrease" xlink:label="loc_anab_CommonStockCapitalSharesReservedForFutureIssuanceIncrease_E7169266C792029B3ECBEE195396A184" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_5364FA61B2584EAA2885EE19539585D9" xlink:to="loc_anab_CommonStockCapitalSharesReservedForFutureIssuanceIncrease_E7169266C792029B3ECBEE195396A184" 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_CAE49EDD85ED79471BBAEE195396700F" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_5364FA61B2584EAA2885EE19539585D9" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardAwardVestingPeriod1_CAE49EDD85ED79471BBAEE195396700F" 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_3655A5860F4248CAF5A1EE1953978673" xlink:type="locator" />
    <link:definitionArc order="4" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_5364FA61B2584EAA2885EE19539585D9" xlink:to="loc_us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardExpirationPeriod_3655A5860F4248CAF5A1EE1953978673" 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_233A2039C955DEA1990FEE195397870A" xlink:type="locator" />
    <link:definitionArc order="5" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_5364FA61B2584EAA2885EE19539585D9" xlink:to="loc_us-gaap_ProceedsFromStockOptionsExercised_233A2039C955DEA1990FEE195397870A" 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_5E8ECB70F51AC947BE10EE1953970095" xlink:type="locator" />
    <link:definitionArc order="6" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_5364FA61B2584EAA2885EE19539585D9" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriodGross_5E8ECB70F51AC947BE10EE1953970095" xlink:type="arc" />
    <link:loc xlink:href="anab-20181231.xsd#anab_EmployeeAndNonemployeeServiceSharebasedCompensationNonvestedAwardsCompensationNotYetRecognizedStockOptions" xlink:label="loc_anab_EmployeeAndNonemployeeServiceSharebasedCompensationNonvestedAwardsCompensationNotYetRecognizedStockOptions_AE17810EB620566374E3EE1953983E41" xlink:type="locator" />
    <link:definitionArc order="7" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_5364FA61B2584EAA2885EE19539585D9" xlink:to="loc_anab_EmployeeAndNonemployeeServiceSharebasedCompensationNonvestedAwardsCompensationNotYetRecognizedStockOptions_AE17810EB620566374E3EE1953983E41" xlink:type="arc" />
    <link:loc xlink:href="anab-20181231.xsd#anab_EmployeeAndNonemployeeServiceSharebasedCompensationNonvestedAwardsCompensationCostNotYetRecognizedPeriodForRecognition" xlink:label="loc_anab_EmployeeAndNonemployeeServiceSharebasedCompensationNonvestedAwardsCompensationCostNotYetRecognizedPeriodForRecognition_9AF4A09FAF3C9C5FCD29EE195398892C" xlink:type="locator" />
    <link:definitionArc order="8" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_5364FA61B2584EAA2885EE19539585D9" xlink:to="loc_anab_EmployeeAndNonemployeeServiceSharebasedCompensationNonvestedAwardsCompensationCostNotYetRecognizedPeriodForRecognition_9AF4A09FAF3C9C5FCD29EE195398892C" 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_BF492C2F00A851C8EAAB13936EDF83AA" 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_EE9EA36FF25DED049BED13936EDE940C" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_BF492C2F00A851C8EAAB13936EDF83AA" xlink:to="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_EE9EA36FF25DED049BED13936EDE940C" 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_96281EEC30A8B2DA6F9613936EDE1D3F" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_EE9EA36FF25DED049BED13936EDE940C" xlink:to="loc_us-gaap_AwardTypeAxis_96281EEC30A8B2DA6F9613936EDE1D3F" 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_17FBF05F78AC95E4FB3C13936EDE18F5_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_AwardTypeAxis_96281EEC30A8B2DA6F9613936EDE1D3F" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_17FBF05F78AC95E4FB3C13936EDE18F5_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_17FBF05F78AC95E4FB3C13936EDE18F5" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_AwardTypeAxis_96281EEC30A8B2DA6F9613936EDE1D3F" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_17FBF05F78AC95E4FB3C13936EDE18F5" 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_80E7EE4691C0871F5F9313936EDFA464" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_17FBF05F78AC95E4FB3C13936EDE18F5" xlink:to="loc_us-gaap_EmployeeStockOptionMember_80E7EE4691C0871F5F9313936EDFA464" 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_508375469793F326A54513936EDF315C" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_BF492C2F00A851C8EAAB13936EDF83AA" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsRiskFreeInterestRate_508375469793F326A54513936EDF315C" 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_3A1DAE1F0948A311737913936EE0C6EE" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_BF492C2F00A851C8EAAB13936EDF83AA" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsExpectedVolatilityRate_3A1DAE1F0948A311737913936EE0C6EE" 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_88A7DD7CC9AD91FC1F9413936EE0AC9C" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_BF492C2F00A851C8EAAB13936EDF83AA" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsExpectedDividendRate_88A7DD7CC9AD91FC1F9413936EE0AC9C" 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_14ACD07B94BE4ACCC89413936EE0806B" xlink:type="locator" />
    <link:definitionArc order="4" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_BF492C2F00A851C8EAAB13936EDF83AA" xlink:to="loc_us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardFairValueAssumptionsExpectedTerm1_14ACD07B94BE4ACCC89413936EE0806B" 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_0B3D6E0057D732F154BA13936EE023A4" xlink:type="locator" />
    <link:definitionArc order="5" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_BF492C2F00A851C8EAAB13936EDF83AA" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriodWeightedAverageGrantDateFairValue_0B3D6E0057D732F154BA13936EE023A4" 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_C8E123305ECF04451746E8E1C25F5BDD" 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_E37AF21B5022E3710E7DE8E1C2586632" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_C8E123305ECF04451746E8E1C25F5BDD" xlink:to="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable_E37AF21B5022E3710E7DE8E1C2586632" 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_B5F6F9B83D22F953E129E8E1C2599F93" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable_E37AF21B5022E3710E7DE8E1C2586632" xlink:to="loc_us-gaap_FairValueByMeasurementFrequencyAxis_B5F6F9B83D22F953E129E8E1C2599F93" 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_CF2518C5A9144571269FE8E1C2591AEE_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_FairValueByMeasurementFrequencyAxis_B5F6F9B83D22F953E129E8E1C2599F93" xlink:to="loc_us-gaap_FairValueMeasurementFrequencyDomain_CF2518C5A9144571269FE8E1C2591AEE_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_CF2518C5A9144571269FE8E1C2591AEE" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_FairValueByMeasurementFrequencyAxis_B5F6F9B83D22F953E129E8E1C2599F93" xlink:to="loc_us-gaap_FairValueMeasurementFrequencyDomain_CF2518C5A9144571269FE8E1C2591AEE" 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_82F4795B2C895BD7D8B6E8E1C2592A03" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueMeasurementFrequencyDomain_CF2518C5A9144571269FE8E1C2591AEE" xlink:to="loc_us-gaap_FairValueMeasurementsRecurringMember_82F4795B2C895BD7D8B6E8E1C2592A03" 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_E608216D1FFCF02EF1EBE8E1C25AA1D4" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable_E37AF21B5022E3710E7DE8E1C2586632" xlink:to="loc_us-gaap_FairValueByFairValueHierarchyLevelAxis_E608216D1FFCF02EF1EBE8E1C25AA1D4" 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_3DC19B914C4FBF5D7013E8E1C25A1B8F_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_FairValueByFairValueHierarchyLevelAxis_E608216D1FFCF02EF1EBE8E1C25AA1D4" xlink:to="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_3DC19B914C4FBF5D7013E8E1C25A1B8F_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_3DC19B914C4FBF5D7013E8E1C25A1B8F" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_FairValueByFairValueHierarchyLevelAxis_E608216D1FFCF02EF1EBE8E1C25AA1D4" xlink:to="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_3DC19B914C4FBF5D7013E8E1C25A1B8F" 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_D9539AD7683E5BADBC11E8E1C25BA328" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_3DC19B914C4FBF5D7013E8E1C25A1B8F" xlink:to="loc_us-gaap_FairValueInputsLevel1Member_D9539AD7683E5BADBC11E8E1C25BA328" 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_84E62A98CF8BB2033A9EE8E1C25BDE78" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_3DC19B914C4FBF5D7013E8E1C25A1B8F" xlink:to="loc_us-gaap_FairValueInputsLevel2Member_84E62A98CF8BB2033A9EE8E1C25BDE78" 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_5FEB699D67804D139F2EE8E1C25C5386" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_3DC19B914C4FBF5D7013E8E1C25A1B8F" xlink:to="loc_us-gaap_FairValueInputsLevel3Member_5FEB699D67804D139F2EE8E1C25C5386" 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_7374E54D717AFE841BFDE8E1C25C8668" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable_E37AF21B5022E3710E7DE8E1C2586632" xlink:to="loc_us-gaap_CashAndCashEquivalentsAxis_7374E54D717AFE841BFDE8E1C25C8668" 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_F3FA69FC1C1566FC89F3E8E1C25C07B1_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_CashAndCashEquivalentsAxis_7374E54D717AFE841BFDE8E1C25C8668" xlink:to="loc_us-gaap_RestrictedCashAndCashEquivalentsCashAndCashEquivalentsMember_F3FA69FC1C1566FC89F3E8E1C25C07B1_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_F3FA69FC1C1566FC89F3E8E1C25C07B1" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_CashAndCashEquivalentsAxis_7374E54D717AFE841BFDE8E1C25C8668" xlink:to="loc_us-gaap_RestrictedCashAndCashEquivalentsCashAndCashEquivalentsMember_F3FA69FC1C1566FC89F3E8E1C25C07B1" 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_C0BAF47AC03685306704E8E1C25D1566" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RestrictedCashAndCashEquivalentsCashAndCashEquivalentsMember_F3FA69FC1C1566FC89F3E8E1C25C07B1" xlink:to="loc_us-gaap_MoneyMarketFundsMember_C0BAF47AC03685306704E8E1C25D1566" 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_794095A8F6CDCFCFD6D2E8E1C25D6A4B" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RestrictedCashAndCashEquivalentsCashAndCashEquivalentsMember_F3FA69FC1C1566FC89F3E8E1C25C07B1" xlink:to="loc_us-gaap_MutualFundMember_794095A8F6CDCFCFD6D2E8E1C25D6A4B" 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_085EAB78D1F8B312DF17E8E1C25D1698" xlink:type="locator" />
    <link:definitionArc order="4" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable_E37AF21B5022E3710E7DE8E1C2586632" xlink:to="loc_us-gaap_FinancialInstrumentAxis_085EAB78D1F8B312DF17E8E1C25D1698" 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_EAB423834CF595734B3DE8E1C25E58E0_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_FinancialInstrumentAxis_085EAB78D1F8B312DF17E8E1C25D1698" xlink:to="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_EAB423834CF595734B3DE8E1C25E58E0_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_EAB423834CF595734B3DE8E1C25E58E0" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_FinancialInstrumentAxis_085EAB78D1F8B312DF17E8E1C25D1698" xlink:to="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_EAB423834CF595734B3DE8E1C25E58E0" 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_3AE5CE9C2DDE6002AB40E8E1C25EE898" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_EAB423834CF595734B3DE8E1C25E58E0" xlink:to="loc_us-gaap_USTreasurySecuritiesMember_3AE5CE9C2DDE6002AB40E8E1C25EE898" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_CertificatesOfDepositMember" xlink:label="loc_us-gaap_CertificatesOfDepositMember_8AFB3562119A38E5E27FE909C3609FB9" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_EAB423834CF595734B3DE8E1C25E58E0" xlink:to="loc_us-gaap_CertificatesOfDepositMember_8AFB3562119A38E5E27FE909C3609FB9" 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_1AD960B02BBD8525E55BE8E1C25E0B5A" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_EAB423834CF595734B3DE8E1C25E58E0" xlink:to="loc_us-gaap_USGovernmentAgenciesDebtSecuritiesMember_1AD960B02BBD8525E55BE8E1C25E0B5A" xlink:type="arc" />
    <link:loc xlink:href="anab-20181231.xsd#anab_CommercialAndCorporateObligationsMember" xlink:label="loc_anab_CommercialAndCorporateObligationsMember_E08E49DE96942624DE81E8E1C25ED5A3" xlink:type="locator" />
    <link:definitionArc order="4" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_EAB423834CF595734B3DE8E1C25E58E0" xlink:to="loc_anab_CommercialAndCorporateObligationsMember_E08E49DE96942624DE81E8E1C25ED5A3" xlink:type="arc" />
    <link:loc xlink:href="anab-20181231.xsd#anab_CashAndCashEquivalentsAndRestrictedCashFairValueDisclosure" xlink:label="loc_anab_CashAndCashEquivalentsAndRestrictedCashFairValueDisclosure_B085C031F078152419A0E8E1C25F04FF" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_C8E123305ECF04451746E8E1C25F5BDD" xlink:to="loc_anab_CashAndCashEquivalentsAndRestrictedCashFairValueDisclosure_B085C031F078152419A0E8E1C25F04FF" 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_AE91DEAA6413DF5214BEE8E1C25F50D4" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_C8E123305ECF04451746E8E1C25F5BDD" xlink:to="loc_us-gaap_AvailableForSaleSecuritiesDebtSecurities_AE91DEAA6413DF5214BEE8E1C25F50D4" 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_A6785203B30A9CBFACA50C3934CE7E39" 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_B6804A783E7CCC050B6A0C3934C9AB1D" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_ScheduleOfAvailableForSaleSecuritiesLineItems_A6785203B30A9CBFACA50C3934CE7E39" xlink:to="loc_us-gaap_DebtSecuritiesAvailableForSaleTable_B6804A783E7CCC050B6A0C3934C9AB1D" 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_9FBBAEE11540790F67330C3934CA714F" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DebtSecuritiesAvailableForSaleTable_B6804A783E7CCC050B6A0C3934C9AB1D" xlink:to="loc_us-gaap_FinancialInstrumentAxis_9FBBAEE11540790F67330C3934CA714F" 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_0804EF8ED485AF8DF0300C3934CB5118_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_FinancialInstrumentAxis_9FBBAEE11540790F67330C3934CA714F" xlink:to="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_0804EF8ED485AF8DF0300C3934CB5118_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_0804EF8ED485AF8DF0300C3934CB5118" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_FinancialInstrumentAxis_9FBBAEE11540790F67330C3934CA714F" xlink:to="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_0804EF8ED485AF8DF0300C3934CB5118" 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_86C53D56D33B4929AB5E0C3934CBBF14" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_0804EF8ED485AF8DF0300C3934CB5118" xlink:to="loc_us-gaap_USGovernmentAgenciesDebtSecuritiesMember_86C53D56D33B4929AB5E0C3934CBBF14" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_CertificatesOfDepositMember" xlink:label="loc_us-gaap_CertificatesOfDepositMember_AF46AC598BCB8C3BD8E20C3934CC6D94" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_0804EF8ED485AF8DF0300C3934CB5118" xlink:to="loc_us-gaap_CertificatesOfDepositMember_AF46AC598BCB8C3BD8E20C3934CC6D94" xlink:type="arc" />
    <link:loc xlink:href="anab-20181231.xsd#anab_CommercialAndCorporateObligationsMember" xlink:label="loc_anab_CommercialAndCorporateObligationsMember_5AB0C7E96270495F2A340C3934CC78DD" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_0804EF8ED485AF8DF0300C3934CB5118" xlink:to="loc_anab_CommercialAndCorporateObligationsMember_5AB0C7E96270495F2A340C3934CC78DD" 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_3CA55298D349DBC494370C3934CCA03F" xlink:type="locator" />
    <link:definitionArc order="4" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_0804EF8ED485AF8DF0300C3934CB5118" xlink:to="loc_us-gaap_USTreasurySecuritiesMember_3CA55298D349DBC494370C3934CCA03F" 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_091B0F49748BD4A096DA0C3934CD9E9B" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DebtSecuritiesAvailableForSaleTable_B6804A783E7CCC050B6A0C3934C9AB1D" xlink:to="loc_srt_RangeAxis_091B0F49748BD4A096DA0C3934CD9E9B" 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_C63B3872A01757E8597D0C3934CDB602_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_RangeAxis_091B0F49748BD4A096DA0C3934CD9E9B" xlink:to="loc_srt_RangeMember_C63B3872A01757E8597D0C3934CDB602_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_C63B3872A01757E8597D0C3934CDB602" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_RangeAxis_091B0F49748BD4A096DA0C3934CD9E9B" xlink:to="loc_srt_RangeMember_C63B3872A01757E8597D0C3934CDB602" 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_AE918CFC8BABA3919BC30C3934CD452A" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_RangeMember_C63B3872A01757E8597D0C3934CDB602" xlink:to="loc_srt_MinimumMember_AE918CFC8BABA3919BC30C3934CD452A" 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_AA782F3A3C725E7533030C3934CDBF49" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_RangeMember_C63B3872A01757E8597D0C3934CDB602" xlink:to="loc_srt_MaximumMember_AA782F3A3C725E7533030C3934CDBF49" 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_6A29B9FD4263C6D57C620C3934CE08C4" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ScheduleOfAvailableForSaleSecuritiesLineItems_A6785203B30A9CBFACA50C3934CE7E39" xlink:to="loc_us-gaap_AvailableForSaleDebtSecuritiesAmortizedCostBasis_6A29B9FD4263C6D57C620C3934CE08C4" 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_D2417A5709FC1CB785440C3934D10A96" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ScheduleOfAvailableForSaleSecuritiesLineItems_A6785203B30A9CBFACA50C3934CE7E39" xlink:to="loc_us-gaap_AvailableForSaleDebtSecuritiesAccumulatedGrossUnrealizedGainBeforeTax_D2417A5709FC1CB785440C3934D10A96" 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_9290EC2EF3DA7DDDC7CB0C3934D1D69A" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ScheduleOfAvailableForSaleSecuritiesLineItems_A6785203B30A9CBFACA50C3934CE7E39" xlink:to="loc_us-gaap_AvailableForSaleDebtSecuritiesAccumulatedGrossUnrealizedLossBeforeTax_9290EC2EF3DA7DDDC7CB0C3934D1D69A" 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_AECBC42B548A66DBE8780C3934D1F9C3" xlink:type="locator" />
    <link:definitionArc order="4" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ScheduleOfAvailableForSaleSecuritiesLineItems_A6785203B30A9CBFACA50C3934CE7E39" xlink:to="loc_us-gaap_AvailableForSaleSecuritiesDebtSecurities_AECBC42B548A66DBE8780C3934D1F9C3" 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_F169537E3E8C48F3DA7E0C3934D1511C" xlink:type="locator" />
    <link:definitionArc order="5" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ScheduleOfAvailableForSaleSecuritiesLineItems_A6785203B30A9CBFACA50C3934CE7E39" xlink:to="loc_us-gaap_AvailableForSaleSecuritiesDebtSecuritiesCurrent_F169537E3E8C48F3DA7E0C3934D1511C" 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_1D884C2B45130CDDFADB0C3934D163EF" xlink:type="locator" />
    <link:definitionArc order="6" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ScheduleOfAvailableForSaleSecuritiesLineItems_A6785203B30A9CBFACA50C3934CE7E39" xlink:to="loc_us-gaap_AvailableForSaleSecuritiesDebtSecuritiesNoncurrent_1D884C2B45130CDDFADB0C3934D163EF" xlink:type="arc" />
    <link:loc xlink:href="anab-20181231.xsd#anab_AvailableforsaleDebtSecuritiesRemainingMaturity" xlink:label="loc_anab_AvailableforsaleDebtSecuritiesRemainingMaturity_58548569F1B0C6BD576C0C3934D15DBB" xlink:type="locator" />
    <link:definitionArc order="7" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ScheduleOfAvailableForSaleSecuritiesLineItems_A6785203B30A9CBFACA50C3934CE7E39" xlink:to="loc_anab_AvailableforsaleDebtSecuritiesRemainingMaturity_58548569F1B0C6BD576C0C3934D15DBB" 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_2DF64BE074224636C42AE99A4A04C6E4" 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_297EC38B1C963B821438E99A49F90E4E" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisValuationTechniquesLineItems_2DF64BE074224636C42AE99A4A04C6E4" xlink:to="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisValuationTechniquesTable_297EC38B1C963B821438E99A49F90E4E" 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_E747200A0DA3EB03F45CE99A49FACDE2" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisValuationTechniquesTable_297EC38B1C963B821438E99A49F90E4E" xlink:to="loc_us-gaap_FairValueByLiabilityClassAxis_E747200A0DA3EB03F45CE99A49FACDE2" 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_ED1F4FF6776FB14DE8DAE99A49FA0160_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_FairValueByLiabilityClassAxis_E747200A0DA3EB03F45CE99A49FACDE2" xlink:to="loc_us-gaap_FairValueLiabilitiesMeasuredOnRecurringBasisUnobservableInputReconciliationByLiabilityClassDomain_ED1F4FF6776FB14DE8DAE99A49FA0160_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_ED1F4FF6776FB14DE8DAE99A49FA0160" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_FairValueByLiabilityClassAxis_E747200A0DA3EB03F45CE99A49FACDE2" xlink:to="loc_us-gaap_FairValueLiabilitiesMeasuredOnRecurringBasisUnobservableInputReconciliationByLiabilityClassDomain_ED1F4FF6776FB14DE8DAE99A49FA0160" 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_56429504E5B705A984CEE99A49FA5755" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueLiabilitiesMeasuredOnRecurringBasisUnobservableInputReconciliationByLiabilityClassDomain_ED1F4FF6776FB14DE8DAE99A49FA0160" xlink:to="loc_us-gaap_DerivativeFinancialInstrumentsLiabilitiesMember_56429504E5B705A984CEE99A49FA5755" 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_E86F28A7DC73884F118CE99A49FB338F" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisValuationTechniquesTable_297EC38B1C963B821438E99A49F90E4E" xlink:to="loc_us-gaap_FairValueByMeasurementFrequencyAxis_E86F28A7DC73884F118CE99A49FB338F" 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_440B849992A8DBED0BEDE99A49FB7625_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_FairValueByMeasurementFrequencyAxis_E86F28A7DC73884F118CE99A49FB338F" xlink:to="loc_us-gaap_FairValueMeasurementFrequencyDomain_440B849992A8DBED0BEDE99A49FB7625_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_440B849992A8DBED0BEDE99A49FB7625" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_FairValueByMeasurementFrequencyAxis_E86F28A7DC73884F118CE99A49FB338F" xlink:to="loc_us-gaap_FairValueMeasurementFrequencyDomain_440B849992A8DBED0BEDE99A49FB7625" 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_7DF18EDE650C8A916FE7E99A49FBB945" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueMeasurementFrequencyDomain_440B849992A8DBED0BEDE99A49FB7625" xlink:to="loc_us-gaap_FairValueMeasurementsRecurringMember_7DF18EDE650C8A916FE7E99A49FBB945" 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_2277E7767F87082799D4E99A49FB3D59" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisValuationTechniquesTable_297EC38B1C963B821438E99A49F90E4E" xlink:to="loc_us-gaap_StatementClassOfStockAxis_2277E7767F87082799D4E99A49FB3D59" 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_5D6758CAF088198422EFE99A49FCCCF6_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_StatementClassOfStockAxis_2277E7767F87082799D4E99A49FB3D59" xlink:to="loc_us-gaap_ClassOfStockDomain_5D6758CAF088198422EFE99A49FCCCF6_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_5D6758CAF088198422EFE99A49FCCCF6" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_StatementClassOfStockAxis_2277E7767F87082799D4E99A49FB3D59" xlink:to="loc_us-gaap_ClassOfStockDomain_5D6758CAF088198422EFE99A49FCCCF6" 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_F1302EEAEB3631CB3E03E99A49FC6EBC" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockDomain_5D6758CAF088198422EFE99A49FCCCF6" xlink:to="loc_us-gaap_SeriesCPreferredStockMember_F1302EEAEB3631CB3E03E99A49FC6EBC" 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_266C060C515131189361E99A49FC9D9E" xlink:type="locator" />
    <link:definitionArc order="4" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisValuationTechniquesTable_297EC38B1C963B821438E99A49F90E4E" xlink:to="loc_us-gaap_MeasurementInputTypeAxis_266C060C515131189361E99A49FC9D9E" 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_3B2D312D3DE3E678AEB3E99A49FC16DC_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_MeasurementInputTypeAxis_266C060C515131189361E99A49FC9D9E" xlink:to="loc_us-gaap_MeasurementInputTypeDomain_3B2D312D3DE3E678AEB3E99A49FC16DC_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_3B2D312D3DE3E678AEB3E99A49FC16DC" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_MeasurementInputTypeAxis_266C060C515131189361E99A49FC9D9E" xlink:to="loc_us-gaap_MeasurementInputTypeDomain_3B2D312D3DE3E678AEB3E99A49FC16DC" 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_FA66D695D7BCA156387FE99A49FD7223" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_MeasurementInputTypeDomain_3B2D312D3DE3E678AEB3E99A49FC16DC" xlink:to="loc_us-gaap_MeasurementInputExercisePriceMember_FA66D695D7BCA156387FE99A49FD7223" 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_F5718CAF48396421B78DE99A49FDAC64" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_MeasurementInputTypeDomain_3B2D312D3DE3E678AEB3E99A49FC16DC" xlink:to="loc_us-gaap_MeasurementInputRiskFreeInterestRateMember_F5718CAF48396421B78DE99A49FDAC64" 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_545FD912352CFF61FE00E99A49FDDB8E" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_MeasurementInputTypeDomain_3B2D312D3DE3E678AEB3E99A49FC16DC" xlink:to="loc_us-gaap_MeasurementInputOptionVolatilityMember_545FD912352CFF61FE00E99A49FDDB8E" 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_2090D6A679EC9486D4CFE99A49FEC4C4" xlink:type="locator" />
    <link:definitionArc order="4" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_MeasurementInputTypeDomain_3B2D312D3DE3E678AEB3E99A49FC16DC" xlink:to="loc_us-gaap_MeasurementInputExpectedDividendRateMember_2090D6A679EC9486D4CFE99A49FEC4C4" 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_48894D6593D388A2D745E99A4A03780B" xlink:type="locator" />
    <link:definitionArc order="5" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_MeasurementInputTypeDomain_3B2D312D3DE3E678AEB3E99A49FC16DC" xlink:to="loc_us-gaap_MeasurementInputExpectedTermMember_48894D6593D388A2D745E99A4A03780B" 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_3B3F5D9DF39AF1603D54E99A4A040154" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisValuationTechniquesLineItems_2DF64BE074224636C42AE99A4A04C6E4" xlink:to="loc_us-gaap_SharePrice_3B3F5D9DF39AF1603D54E99A4A040154" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_WarrantsAndRightsOutstandingMeasurementInput" xlink:label="loc_us-gaap_WarrantsAndRightsOutstandingMeasurementInput_FDFF8C655AB3D412E488E99A4A043323" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisValuationTechniquesLineItems_2DF64BE074224636C42AE99A4A04C6E4" xlink:to="loc_us-gaap_WarrantsAndRightsOutstandingMeasurementInput_FDFF8C655AB3D412E488E99A4A043323" 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_78020170BFA00A619B88E99A4A04F5E2" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisValuationTechniquesLineItems_2DF64BE074224636C42AE99A4A04C6E4" xlink:to="loc_us-gaap_WarrantsAndRightsOutstandingTerm_78020170BFA00A619B88E99A4A04F5E2" xlink:type="arc" />
    <link:loc xlink:href="anab-20181231.xsd#anab_FairValueAssumptionsWeightedAverageGrantDateFairValuePerShare" xlink:label="loc_anab_FairValueAssumptionsWeightedAverageGrantDateFairValuePerShare_BF69D6AC975D38362813E99A4A05665C" xlink:type="locator" />
    <link:definitionArc order="4" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisValuationTechniquesLineItems_2DF64BE074224636C42AE99A4A04C6E4" xlink:to="loc_anab_FairValueAssumptionsWeightedAverageGrantDateFairValuePerShare_BF69D6AC975D38362813E99A4A05665C" 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_09B6F566A016E8D2B564E8E1C2205EC0" 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_A73F9F48576B7905A410E8E1C21E6CB6" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_FairValueBalanceSheetGroupingFinancialStatementCaptionsLineItems_09B6F566A016E8D2B564E8E1C2205EC0" xlink:to="loc_us-gaap_FairValueByBalanceSheetGroupingTable_A73F9F48576B7905A410E8E1C21E6CB6" 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_9D102B0AE94005F3F5AFE8E1C21E7D38" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_FairValueByBalanceSheetGroupingTable_A73F9F48576B7905A410E8E1C21E6CB6" xlink:to="loc_us-gaap_FairValueByMeasurementBasisAxis_9D102B0AE94005F3F5AFE8E1C21E7D38" 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_F086DB7AD93CA84B21E6E8E1C220A118_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_FairValueByMeasurementBasisAxis_9D102B0AE94005F3F5AFE8E1C21E7D38" xlink:to="loc_us-gaap_PortionAtFairValueFairValueDisclosureMember_F086DB7AD93CA84B21E6E8E1C220A118_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_FACCCF123215312F0B1DE8E1C21E12FF" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_FairValueByMeasurementBasisAxis_9D102B0AE94005F3F5AFE8E1C21E7D38" xlink:to="loc_us-gaap_FairValueDisclosureItemAmountsDomain_FACCCF123215312F0B1DE8E1C21E12FF" 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_F086DB7AD93CA84B21E6E8E1C220A118" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueDisclosureItemAmountsDomain_FACCCF123215312F0B1DE8E1C21E12FF" xlink:to="loc_us-gaap_PortionAtFairValueFairValueDisclosureMember_F086DB7AD93CA84B21E6E8E1C220A118" 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_8ABA8A1CABD8C98AC90CE8E1C2202DC8" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueDisclosureItemAmountsDomain_FACCCF123215312F0B1DE8E1C21E12FF" xlink:to="loc_us-gaap_CarryingReportedAmountFairValueDisclosureMember_8ABA8A1CABD8C98AC90CE8E1C2202DC8" 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_571618C2372991902D1BE8E1C220E9A2" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueDisclosureItemAmountsDomain_FACCCF123215312F0B1DE8E1C21E12FF" xlink:to="loc_us-gaap_EstimateOfFairValueFairValueDisclosureMember_571618C2372991902D1BE8E1C220E9A2" 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_022BCD45E8E3C1850DDFE8E1C22184DF" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueBalanceSheetGroupingFinancialStatementCaptionsLineItems_09B6F566A016E8D2B564E8E1C2205EC0" xlink:to="loc_us-gaap_NotesPayableFairValueDisclosure_022BCD45E8E3C1850DDFE8E1C22184DF" 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_1FB347C54B2A4C11C169E8E1C22FA226" 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_8FD22A8270E7BD1DAAE4E8E1C22B2A7E" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_FairValueLiabilitiesMeasuredOnRecurringBasisUnobservableInputReconciliationLineItems_1FB347C54B2A4C11C169E8E1C22FA226" xlink:to="loc_us-gaap_FairValueLiabilitiesMeasuredOnRecurringBasisUnobservableInputReconciliationTable_8FD22A8270E7BD1DAAE4E8E1C22B2A7E" 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_428CF3B38ECB48C56F83E8E1C22B5B1F" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_FairValueLiabilitiesMeasuredOnRecurringBasisUnobservableInputReconciliationTable_8FD22A8270E7BD1DAAE4E8E1C22B2A7E" xlink:to="loc_us-gaap_StatementClassOfStockAxis_428CF3B38ECB48C56F83E8E1C22B5B1F" 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_E1D1D025C87B893500EDE8E1C22C9B32_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_StatementClassOfStockAxis_428CF3B38ECB48C56F83E8E1C22B5B1F" xlink:to="loc_us-gaap_ClassOfStockDomain_E1D1D025C87B893500EDE8E1C22C9B32_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_E1D1D025C87B893500EDE8E1C22C9B32" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_StatementClassOfStockAxis_428CF3B38ECB48C56F83E8E1C22B5B1F" xlink:to="loc_us-gaap_ClassOfStockDomain_E1D1D025C87B893500EDE8E1C22C9B32" 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_A87C146B40455613F6A9E8E1C22C46C4" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockDomain_E1D1D025C87B893500EDE8E1C22C9B32" xlink:to="loc_us-gaap_SeriesCPreferredStockMember_A87C146B40455613F6A9E8E1C22C46C4" 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_7A7FE10B5F5298C58375E8E1C22CEC70" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_FairValueLiabilitiesMeasuredOnRecurringBasisUnobservableInputReconciliationTable_8FD22A8270E7BD1DAAE4E8E1C22B2A7E" xlink:to="loc_us-gaap_FairValueByLiabilityClassAxis_7A7FE10B5F5298C58375E8E1C22CEC70" 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_420190EC37A8F7D2F895E8E1C22D5E2D_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_FairValueByLiabilityClassAxis_7A7FE10B5F5298C58375E8E1C22CEC70" xlink:to="loc_us-gaap_FairValueLiabilitiesMeasuredOnRecurringBasisUnobservableInputReconciliationByLiabilityClassDomain_420190EC37A8F7D2F895E8E1C22D5E2D_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_420190EC37A8F7D2F895E8E1C22D5E2D" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_FairValueByLiabilityClassAxis_7A7FE10B5F5298C58375E8E1C22CEC70" xlink:to="loc_us-gaap_FairValueLiabilitiesMeasuredOnRecurringBasisUnobservableInputReconciliationByLiabilityClassDomain_420190EC37A8F7D2F895E8E1C22D5E2D" 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_899256C6568D2220906FE8E1C22DDDCF" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueLiabilitiesMeasuredOnRecurringBasisUnobservableInputReconciliationByLiabilityClassDomain_420190EC37A8F7D2F895E8E1C22D5E2D" xlink:to="loc_us-gaap_DerivativeFinancialInstrumentsLiabilitiesMember_899256C6568D2220906FE8E1C22DDDCF" 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_AD8DD03E9F2AFF6C4FDEE8E1C22EED7B" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_FairValueLiabilitiesMeasuredOnRecurringBasisUnobservableInputReconciliationTable_8FD22A8270E7BD1DAAE4E8E1C22B2A7E" xlink:to="loc_us-gaap_FairValueByMeasurementFrequencyAxis_AD8DD03E9F2AFF6C4FDEE8E1C22EED7B" 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_DB5734D3E95FC68A5812E8E1C22E2BEC_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_FairValueByMeasurementFrequencyAxis_AD8DD03E9F2AFF6C4FDEE8E1C22EED7B" xlink:to="loc_us-gaap_FairValueMeasurementFrequencyDomain_DB5734D3E95FC68A5812E8E1C22E2BEC_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_DB5734D3E95FC68A5812E8E1C22E2BEC" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_FairValueByMeasurementFrequencyAxis_AD8DD03E9F2AFF6C4FDEE8E1C22EED7B" xlink:to="loc_us-gaap_FairValueMeasurementFrequencyDomain_DB5734D3E95FC68A5812E8E1C22E2BEC" 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_32B4D932A9AEAC941C92E8E1C22EBA20" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueMeasurementFrequencyDomain_DB5734D3E95FC68A5812E8E1C22E2BEC" xlink:to="loc_us-gaap_FairValueMeasurementsRecurringMember_32B4D932A9AEAC941C92E8E1C22EBA20" 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_E697189E77EEB45553D5E8E1C22F804A" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueLiabilitiesMeasuredOnRecurringBasisUnobservableInputReconciliationLineItems_1FB347C54B2A4C11C169E8E1C22FA226" xlink:to="loc_us-gaap_FairValueLiabilitiesMeasuredOnRecurringBasisUnobservableInputReconciliationCalculationRollForward_E697189E77EEB45553D5E8E1C22F804A" 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_A5558253BEBB3B78AEEAE8E1C22FFB49" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueLiabilitiesMeasuredOnRecurringBasisUnobservableInputReconciliationCalculationRollForward_E697189E77EEB45553D5E8E1C22F804A" xlink:to="loc_us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationsRecurringBasisLiabilityValue_A5558253BEBB3B78AEEAE8E1C22FFB49" 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_C19E0F50D109E40EE363E8E1C231ADE0" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueLiabilitiesMeasuredOnRecurringBasisUnobservableInputReconciliationCalculationRollForward_E697189E77EEB45553D5E8E1C22F804A" xlink:to="loc_us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisLiabilityGainLossIncludedInEarnings_C19E0F50D109E40EE363E8E1C231ADE0" 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_09E0880204FB656238C1E8E1C2327D3D" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueLiabilitiesMeasuredOnRecurringBasisUnobservableInputReconciliationCalculationRollForward_E697189E77EEB45553D5E8E1C22F804A" xlink:to="loc_us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationLiabilityTransfersOutOfLevel3_09E0880204FB656238C1E8E1C2327D3D" 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/IncomeTaxes" xlink:type="extended" />
  <link:definitionLink xlink:role="http://www.anaptysbio.com/role/IncomeTaxesAdditionalInformationDetails" xlink:type="extended">
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_OperatingLossCarryforwardsLineItems" xlink:label="loc_us-gaap_OperatingLossCarryforwardsLineItems_CF7D62041398A4919936E924A33BC262" xlink:type="locator" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_OperatingLossCarryforwardsTable" xlink:label="loc_us-gaap_OperatingLossCarryforwardsTable_D58601033887E0A1D6ABE924A338E51C" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_OperatingLossCarryforwardsLineItems_CF7D62041398A4919936E924A33BC262" xlink:to="loc_us-gaap_OperatingLossCarryforwardsTable_D58601033887E0A1D6ABE924A338E51C" 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_IncomeTaxAuthorityAxis" xlink:label="loc_us-gaap_IncomeTaxAuthorityAxis_6ED85AC381C1E1C226E5E924A339C151" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_OperatingLossCarryforwardsTable_D58601033887E0A1D6ABE924A338E51C" xlink:to="loc_us-gaap_IncomeTaxAuthorityAxis_6ED85AC381C1E1C226E5E924A339C151" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_IncomeTaxAuthorityDomain" xlink:label="loc_us-gaap_IncomeTaxAuthorityDomain_C6C3630D69978CAF973DE924A339ED88_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_IncomeTaxAuthorityAxis_6ED85AC381C1E1C226E5E924A339C151" xlink:to="loc_us-gaap_IncomeTaxAuthorityDomain_C6C3630D69978CAF973DE924A339ED88_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_IncomeTaxAuthorityDomain" xlink:label="loc_us-gaap_IncomeTaxAuthorityDomain_C6C3630D69978CAF973DE924A339ED88" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_IncomeTaxAuthorityAxis_6ED85AC381C1E1C226E5E924A339C151" xlink:to="loc_us-gaap_IncomeTaxAuthorityDomain_C6C3630D69978CAF973DE924A339ED88" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_DomesticCountryMember" xlink:label="loc_us-gaap_DomesticCountryMember_25140D6629967682067BE924A339BE5C" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncomeTaxAuthorityDomain_C6C3630D69978CAF973DE924A339ED88" xlink:to="loc_us-gaap_DomesticCountryMember_25140D6629967682067BE924A339BE5C" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_StateAndLocalJurisdictionMember" xlink:label="loc_us-gaap_StateAndLocalJurisdictionMember_9CA22968F81D35F827C2E924A33A7F6D" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncomeTaxAuthorityDomain_C6C3630D69978CAF973DE924A339ED88" xlink:to="loc_us-gaap_StateAndLocalJurisdictionMember_9CA22968F81D35F827C2E924A33A7F6D" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_ForeignCountryMember" xlink:label="loc_us-gaap_ForeignCountryMember_356B52BE6A4029096B6EE924A33A265A" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncomeTaxAuthorityDomain_C6C3630D69978CAF973DE924A339ED88" xlink:to="loc_us-gaap_ForeignCountryMember_356B52BE6A4029096B6EE924A33A265A" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_TaxPeriodAxis" xlink:label="loc_us-gaap_TaxPeriodAxis_007E72FD846594B47F96E95DAE4FBF26" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_OperatingLossCarryforwardsTable_D58601033887E0A1D6ABE924A338E51C" xlink:to="loc_us-gaap_TaxPeriodAxis_007E72FD846594B47F96E95DAE4FBF26" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_TaxPeriodDomain" xlink:label="loc_us-gaap_TaxPeriodDomain_2EDAA8499AB7FA8086C0E95DAE501874_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_TaxPeriodAxis_007E72FD846594B47F96E95DAE4FBF26" xlink:to="loc_us-gaap_TaxPeriodDomain_2EDAA8499AB7FA8086C0E95DAE501874_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_TaxPeriodDomain" xlink:label="loc_us-gaap_TaxPeriodDomain_2EDAA8499AB7FA8086C0E95DAE501874" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_TaxPeriodAxis_007E72FD846594B47F96E95DAE4FBF26" xlink:to="loc_us-gaap_TaxPeriodDomain_2EDAA8499AB7FA8086C0E95DAE501874" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_TaxYear2018Member" xlink:label="loc_us-gaap_TaxYear2018Member_3620B842588E056B2502E95FDE442B3A" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TaxPeriodDomain_2EDAA8499AB7FA8086C0E95DAE501874" xlink:to="loc_us-gaap_TaxYear2018Member_3620B842588E056B2502E95FDE442B3A" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_TaxCreditCarryforwardAxis" xlink:label="loc_us-gaap_TaxCreditCarryforwardAxis_4CA9E38432FF8D611EF7E924A33ABCD4" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_OperatingLossCarryforwardsTable_D58601033887E0A1D6ABE924A338E51C" xlink:to="loc_us-gaap_TaxCreditCarryforwardAxis_4CA9E38432FF8D611EF7E924A33ABCD4" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_TaxCreditCarryforwardNameDomain" xlink:label="loc_us-gaap_TaxCreditCarryforwardNameDomain_D682029037FC7F5EEB06E924A33A6BC8_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_TaxCreditCarryforwardAxis_4CA9E38432FF8D611EF7E924A33ABCD4" xlink:to="loc_us-gaap_TaxCreditCarryforwardNameDomain_D682029037FC7F5EEB06E924A33A6BC8_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_TaxCreditCarryforwardNameDomain" xlink:label="loc_us-gaap_TaxCreditCarryforwardNameDomain_D682029037FC7F5EEB06E924A33A6BC8" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_TaxCreditCarryforwardAxis_4CA9E38432FF8D611EF7E924A33ABCD4" xlink:to="loc_us-gaap_TaxCreditCarryforwardNameDomain_D682029037FC7F5EEB06E924A33A6BC8" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_ResearchMember" xlink:label="loc_us-gaap_ResearchMember_B45DD37C635F733B305FE924A33B2397" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TaxCreditCarryforwardNameDomain_D682029037FC7F5EEB06E924A33A6BC8" xlink:to="loc_us-gaap_ResearchMember_B45DD37C635F733B305FE924A33B2397" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_OperatingLossCarryforwards" xlink:label="loc_us-gaap_OperatingLossCarryforwards_2130EFC10A495724D34FE924A33BF82A" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_OperatingLossCarryforwardsLineItems_CF7D62041398A4919936E924A33BC262" xlink:to="loc_us-gaap_OperatingLossCarryforwards_2130EFC10A495724D34FE924A33BF82A" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_TaxCreditCarryforwardAmount" xlink:label="loc_us-gaap_TaxCreditCarryforwardAmount_8805860303B5EC85C5A4E924A33CFB88" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_OperatingLossCarryforwardsLineItems_CF7D62041398A4919936E924A33BC262" xlink:to="loc_us-gaap_TaxCreditCarryforwardAmount_8805860303B5EC85C5A4E924A33CFB88" xlink:type="arc" />
    <link:loc xlink:href="anab-20181231.xsd#anab_OperatingLossCarryforwardsLimitationsOnUseAmount" xlink:label="loc_anab_OperatingLossCarryforwardsLimitationsOnUseAmount_FF6FC6D8575822F11584E924A33CE86E" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_OperatingLossCarryforwardsLineItems_CF7D62041398A4919936E924A33BC262" xlink:to="loc_anab_OperatingLossCarryforwardsLimitationsOnUseAmount_FF6FC6D8575822F11584E924A33CE86E" xlink:type="arc" />
    <link:loc xlink:href="anab-20181231.xsd#anab_TaxCreditCarryforwardLimitationsOnUseAmount" xlink:label="loc_anab_TaxCreditCarryforwardLimitationsOnUseAmount_F58760F44EA1EA539DF3E924A33C9835" xlink:type="locator" />
    <link:definitionArc order="4" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_OperatingLossCarryforwardsLineItems_CF7D62041398A4919936E924A33BC262" xlink:to="loc_anab_TaxCreditCarryforwardLimitationsOnUseAmount_F58760F44EA1EA539DF3E924A33C9835" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_EffectiveIncomeTaxRateReconciliationShareBasedCompensationExcessTaxBenefitAmount" xlink:label="loc_us-gaap_EffectiveIncomeTaxRateReconciliationShareBasedCompensationExcessTaxBenefitAmount_3B98199EA81A118F84CCE924A33CDF5B" xlink:type="locator" />
    <link:definitionArc order="5" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_OperatingLossCarryforwardsLineItems_CF7D62041398A4919936E924A33BC262" xlink:to="loc_us-gaap_EffectiveIncomeTaxRateReconciliationShareBasedCompensationExcessTaxBenefitAmount_3B98199EA81A118F84CCE924A33CDF5B" xlink:type="arc" />
    <link:loc xlink:href="anab-20181231.xsd#anab_EffectiveIncomeTaxRateReconciliationNondeductibleExpenseSharebasedCompensationCostDisqualifyingDispositionsOfIncentiveStockOptions" xlink:label="loc_anab_EffectiveIncomeTaxRateReconciliationNondeductibleExpenseSharebasedCompensationCostDisqualifyingDispositionsOfIncentiveStockOptions_FEC6229052B0A73077FCE924A33C3B81" xlink:type="locator" />
    <link:definitionArc order="6" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_OperatingLossCarryforwardsLineItems_CF7D62041398A4919936E924A33BC262" xlink:to="loc_anab_EffectiveIncomeTaxRateReconciliationNondeductibleExpenseSharebasedCompensationCostDisqualifyingDispositionsOfIncentiveStockOptions_FEC6229052B0A73077FCE924A33C3B81" xlink:type="arc" />
    <link:loc xlink:href="anab-20181231.xsd#anab_TaxCutsAndJobsActOf2017ChangeInTaxRateDeferredTaxAssetIncomeTaxExpense" xlink:label="loc_anab_TaxCutsAndJobsActOf2017ChangeInTaxRateDeferredTaxAssetIncomeTaxExpense_7805ADB6735E8EE37698E924A33DC7CC" xlink:type="locator" />
    <link:definitionArc order="7" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_OperatingLossCarryforwardsLineItems_CF7D62041398A4919936E924A33BC262" xlink:to="loc_anab_TaxCutsAndJobsActOf2017ChangeInTaxRateDeferredTaxAssetIncomeTaxExpense_7805ADB6735E8EE37698E924A33DC7CC" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_UnrecognizedTaxBenefitsThatWouldImpactEffectiveTaxRate" xlink:label="loc_us-gaap_UnrecognizedTaxBenefitsThatWouldImpactEffectiveTaxRate_8E83AAA6F18BF248651FE924A33D9822" xlink:type="locator" />
    <link:definitionArc order="8" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_OperatingLossCarryforwardsLineItems_CF7D62041398A4919936E924A33BC262" xlink:to="loc_us-gaap_UnrecognizedTaxBenefitsThatWouldImpactEffectiveTaxRate_8E83AAA6F18BF248651FE924A33D9822" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_UnrecognizedTaxBenefitsIncomeTaxPenaltiesAndInterestExpense" xlink:label="loc_us-gaap_UnrecognizedTaxBenefitsIncomeTaxPenaltiesAndInterestExpense_10612C9816B0C70298E0E924A33D0ED5" xlink:type="locator" />
    <link:definitionArc order="9" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_OperatingLossCarryforwardsLineItems_CF7D62041398A4919936E924A33BC262" xlink:to="loc_us-gaap_UnrecognizedTaxBenefitsIncomeTaxPenaltiesAndInterestExpense_10612C9816B0C70298E0E924A33D0ED5" xlink:type="arc" />
  </link:definitionLink>
  <link:definitionLink xlink:role="http://www.anaptysbio.com/role/IncomeTaxesComponentsOfIncomeLossBeforeIncomeTaxProvisionBenefitDetails" xlink:type="extended" />
  <link:definitionLink xlink:role="http://www.anaptysbio.com/role/IncomeTaxesDeferredTaxAssetsAndLiabilitiesDetails" xlink:type="extended" />
  <link:definitionLink xlink:role="http://www.anaptysbio.com/role/IncomeTaxesReconciliationOfIncomeTaxesDetails" xlink:type="extended" />
  <link:definitionLink xlink:role="http://www.anaptysbio.com/role/IncomeTaxesTables" xlink:type="extended" />
  <link:definitionLink xlink:role="http://www.anaptysbio.com/role/IncomeTaxesUnrecognizedTaxBenefitsDetails" 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_5CD80D9A49727436227A08CE2368BC2D" 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_18D1BC3E5B901F9C663908CE236102C4" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_DebtInstrumentLineItems_5CD80D9A49727436227A08CE2368BC2D" xlink:to="loc_us-gaap_DebtInstrumentTable_18D1BC3E5B901F9C663908CE236102C4" 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_A9A8A249C9F49279F58E08CE23611B75" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DebtInstrumentTable_18D1BC3E5B901F9C663908CE236102C4" xlink:to="loc_us-gaap_LongtermDebtTypeAxis_A9A8A249C9F49279F58E08CE23611B75" 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_F6B8207FFC06C4735F7208CE236105AE_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_LongtermDebtTypeAxis_A9A8A249C9F49279F58E08CE23611B75" xlink:to="loc_us-gaap_LongtermDebtTypeDomain_F6B8207FFC06C4735F7208CE236105AE_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_F6B8207FFC06C4735F7208CE236105AE" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_LongtermDebtTypeAxis_A9A8A249C9F49279F58E08CE23611B75" xlink:to="loc_us-gaap_LongtermDebtTypeDomain_F6B8207FFC06C4735F7208CE236105AE" 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_D0294670A8AB1EDD64B808CE2362D755" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LongtermDebtTypeDomain_F6B8207FFC06C4735F7208CE236105AE" xlink:to="loc_us-gaap_NotesPayableToBanksMember_D0294670A8AB1EDD64B808CE2362D755" 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_FB13D22079F02CE6323D08CE23620D98" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DebtInstrumentTable_18D1BC3E5B901F9C663908CE236102C4" xlink:to="loc_us-gaap_DebtInstrumentAxis_FB13D22079F02CE6323D08CE23620D98" 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_29D5655FE411231ED6E208CE2362D4C8_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_DebtInstrumentAxis_FB13D22079F02CE6323D08CE23620D98" xlink:to="loc_us-gaap_DebtInstrumentNameDomain_29D5655FE411231ED6E208CE2362D4C8_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_29D5655FE411231ED6E208CE2362D4C8" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_DebtInstrumentAxis_FB13D22079F02CE6323D08CE23620D98" xlink:to="loc_us-gaap_DebtInstrumentNameDomain_29D5655FE411231ED6E208CE2362D4C8" xlink:type="arc" />
    <link:loc xlink:href="anab-20181231.xsd#anab_LoanAndSecurityAgreementMember" xlink:label="loc_anab_LoanAndSecurityAgreementMember_033C0FF1F21705802F2208CE23636C8F" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_29D5655FE411231ED6E208CE2362D4C8" xlink:to="loc_anab_LoanAndSecurityAgreementMember_033C0FF1F21705802F2208CE23636C8F" xlink:type="arc" />
    <link:loc xlink:href="anab-20181231.xsd#anab_TermLoansMember" xlink:label="loc_anab_TermLoansMember_4081C5EF8113D623C59B08CE2363EFDE" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_anab_LoanAndSecurityAgreementMember_033C0FF1F21705802F2208CE23636C8F" xlink:to="loc_anab_TermLoansMember_4081C5EF8113D623C59B08CE2363EFDE" xlink:type="arc" />
    <link:loc xlink:href="anab-20181231.xsd#anab_TermALoansMember" xlink:label="loc_anab_TermALoansMember_6F22E6F79A47C9E464B708CE23631049" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_anab_TermLoansMember_4081C5EF8113D623C59B08CE2363EFDE" xlink:to="loc_anab_TermALoansMember_6F22E6F79A47C9E464B708CE23631049" xlink:type="arc" />
    <link:loc xlink:href="anab-20181231.xsd#anab_TermBLoansAndTermCLoansMember" xlink:label="loc_anab_TermBLoansAndTermCLoansMember_EB1087B735250F00BA3008CE2364A4F1" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_anab_TermLoansMember_4081C5EF8113D623C59B08CE2363EFDE" xlink:to="loc_anab_TermBLoansAndTermCLoansMember_EB1087B735250F00BA3008CE2364A4F1" 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_6E6D171F217A77DAD32008CE23646EED" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DebtInstrumentTable_18D1BC3E5B901F9C663908CE236102C4" xlink:to="loc_us-gaap_ClassOfWarrantOrRightAxis_6E6D171F217A77DAD32008CE23646EED" 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_53203358E0EBD519C75D08CE23648C31_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_ClassOfWarrantOrRightAxis_6E6D171F217A77DAD32008CE23646EED" xlink:to="loc_us-gaap_ClassOfWarrantOrRightDomain_53203358E0EBD519C75D08CE23648C31_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_53203358E0EBD519C75D08CE23648C31" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_ClassOfWarrantOrRightAxis_6E6D171F217A77DAD32008CE23646EED" xlink:to="loc_us-gaap_ClassOfWarrantOrRightDomain_53203358E0EBD519C75D08CE23648C31" xlink:type="arc" />
    <link:loc xlink:href="anab-20181231.xsd#anab_TermALoanWarrantsMember" xlink:label="loc_anab_TermALoanWarrantsMember_EE3F065283A87C27368408CE2364A830" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfWarrantOrRightDomain_53203358E0EBD519C75D08CE23648C31" xlink:to="loc_anab_TermALoanWarrantsMember_EE3F065283A87C27368408CE2364A830" xlink:type="arc" />
    <link:loc xlink:href="anab-20181231.xsd#anab_TermBAndCLoansWarrantsMember" xlink:label="loc_anab_TermBAndCLoansWarrantsMember_8AD581EFF1A5F7C4D41A08CE23657D4E" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfWarrantOrRightDomain_53203358E0EBD519C75D08CE23648C31" xlink:to="loc_anab_TermBAndCLoansWarrantsMember_8AD581EFF1A5F7C4D41A08CE23657D4E" 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_BE2A2B84B3A69686FC1D08CE236510D1" xlink:type="locator" />
    <link:definitionArc order="4" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DebtInstrumentTable_18D1BC3E5B901F9C663908CE236102C4" xlink:to="loc_us-gaap_StatementClassOfStockAxis_BE2A2B84B3A69686FC1D08CE236510D1" 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_C7D6C7C938772EF6870608CE23650EB4_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_StatementClassOfStockAxis_BE2A2B84B3A69686FC1D08CE236510D1" xlink:to="loc_us-gaap_ClassOfStockDomain_C7D6C7C938772EF6870608CE23650EB4_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_C7D6C7C938772EF6870608CE23650EB4" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_StatementClassOfStockAxis_BE2A2B84B3A69686FC1D08CE236510D1" xlink:to="loc_us-gaap_ClassOfStockDomain_C7D6C7C938772EF6870608CE23650EB4" 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_C779D78CF979327F708308CE23657A6A" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockDomain_C7D6C7C938772EF6870608CE23650EB4" xlink:to="loc_us-gaap_SeriesCPreferredStockMember_C779D78CF979327F708308CE23657A6A" 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_21CC02D49CEF73A3EB5B08CE23657B19" xlink:type="locator" />
    <link:definitionArc order="5" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DebtInstrumentTable_18D1BC3E5B901F9C663908CE236102C4" xlink:to="loc_us-gaap_DerivativeInstrumentRiskAxis_21CC02D49CEF73A3EB5B08CE23657B19" 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_6A127C76003F1499A5A008CE2366FB8D_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_DerivativeInstrumentRiskAxis_21CC02D49CEF73A3EB5B08CE23657B19" xlink:to="loc_us-gaap_DerivativeContractTypeDomain_6A127C76003F1499A5A008CE2366FB8D_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_6A127C76003F1499A5A008CE2366FB8D" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_DerivativeInstrumentRiskAxis_21CC02D49CEF73A3EB5B08CE23657B19" xlink:to="loc_us-gaap_DerivativeContractTypeDomain_6A127C76003F1499A5A008CE2366FB8D" 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_E2C2C12ECD499C8C0F3008CE23662661" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativeContractTypeDomain_6A127C76003F1499A5A008CE2366FB8D" xlink:to="loc_us-gaap_WarrantMember_E2C2C12ECD499C8C0F3008CE23662661" 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_430B17D9C332881CE14E08CE2366C686" xlink:type="locator" />
    <link:definitionArc order="6" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DebtInstrumentTable_18D1BC3E5B901F9C663908CE236102C4" xlink:to="loc_us-gaap_MeasurementInputTypeAxis_430B17D9C332881CE14E08CE2366C686" 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_0D8470DF13AC05A4A6E408CE23673325_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_MeasurementInputTypeAxis_430B17D9C332881CE14E08CE2366C686" xlink:to="loc_us-gaap_MeasurementInputTypeDomain_0D8470DF13AC05A4A6E408CE23673325_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_0D8470DF13AC05A4A6E408CE23673325" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_MeasurementInputTypeAxis_430B17D9C332881CE14E08CE2366C686" xlink:to="loc_us-gaap_MeasurementInputTypeDomain_0D8470DF13AC05A4A6E408CE23673325" 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_68CFF56658BBC53AE75308CE2367FFC5" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_MeasurementInputTypeDomain_0D8470DF13AC05A4A6E408CE23673325" xlink:to="loc_us-gaap_MeasurementInputPriceVolatilityMember_68CFF56658BBC53AE75308CE2367FFC5" 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_BD6D2B719BD3C6D0566D08CE2367F9BB" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_MeasurementInputTypeDomain_0D8470DF13AC05A4A6E408CE23673325" xlink:to="loc_us-gaap_MeasurementInputExpectedTermMember_BD6D2B719BD3C6D0566D08CE2367F9BB" 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_488EB20EAACF9B1FF02908CE23678779" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_MeasurementInputTypeDomain_0D8470DF13AC05A4A6E408CE23673325" xlink:to="loc_us-gaap_MeasurementInputRiskFreeInterestRateMember_488EB20EAACF9B1FF02908CE23678779" 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_D4715309B75BAD71CC4808CE23681C6B" xlink:type="locator" />
    <link:definitionArc order="7" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DebtInstrumentTable_18D1BC3E5B901F9C663908CE236102C4" xlink:to="loc_us-gaap_VariableRateAxis_D4715309B75BAD71CC4808CE23681C6B" 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_667F706E12ADFBE5B75708CE2368F194_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_VariableRateAxis_D4715309B75BAD71CC4808CE23681C6B" xlink:to="loc_us-gaap_VariableRateDomain_667F706E12ADFBE5B75708CE2368F194_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_667F706E12ADFBE5B75708CE2368F194" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_VariableRateAxis_D4715309B75BAD71CC4808CE23681C6B" xlink:to="loc_us-gaap_VariableRateDomain_667F706E12ADFBE5B75708CE2368F194" 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_1F94A0E131C7AC8C2C9208CE236859A9" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_VariableRateDomain_667F706E12ADFBE5B75708CE2368F194" xlink:to="loc_us-gaap_LondonInterbankOfferedRateLIBORMember_1F94A0E131C7AC8C2C9208CE236859A9" xlink:type="arc" />
    <link:loc xlink:href="anab-20181231.xsd#anab_DebtInstrumentMaximumBorrowingCapacity" xlink:label="loc_anab_DebtInstrumentMaximumBorrowingCapacity_FA8DF9465D3010DEA88A08CE2369F559" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_5CD80D9A49727436227A08CE2368BC2D" xlink:to="loc_anab_DebtInstrumentMaximumBorrowingCapacity_FA8DF9465D3010DEA88A08CE2369F559" xlink:type="arc" />
    <link:loc xlink:href="anab-20181231.xsd#anab_DebtInstrumentNumberOfLoanInstallments" xlink:label="loc_anab_DebtInstrumentNumberOfLoanInstallments_853296524604D740E3A408CE23698F4C" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_5CD80D9A49727436227A08CE2368BC2D" xlink:to="loc_anab_DebtInstrumentNumberOfLoanInstallments_853296524604D740E3A408CE23698F4C" 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_1A920419561B1A83E14508CE2369DA6A" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_5CD80D9A49727436227A08CE2368BC2D" xlink:to="loc_us-gaap_DebtInstrumentFaceAmount_1A920419561B1A83E14508CE2369DA6A" 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_228E2E79CAE24D4BE79C08CE2369C59B" xlink:type="locator" />
    <link:definitionArc order="4" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_5CD80D9A49727436227A08CE2368BC2D" xlink:to="loc_us-gaap_ProceedsFromNotesPayable_228E2E79CAE24D4BE79C08CE2369C59B" 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_6A648E16610D6A4D73D608CE2369CC55" xlink:type="locator" />
    <link:definitionArc order="5" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_5CD80D9A49727436227A08CE2368BC2D" xlink:to="loc_us-gaap_DebtInstrumentInterestRateStatedPercentage_6A648E16610D6A4D73D608CE2369CC55" 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_C9DC062D843A36C158CF08CE2369B162" xlink:type="locator" />
    <link:definitionArc order="6" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_5CD80D9A49727436227A08CE2368BC2D" xlink:to="loc_us-gaap_ClassOfWarrantOrRightNumberOfSecuritiesCalledByWarrantsOrRights_C9DC062D843A36C158CF08CE2369B162" 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_47BABF30C56D31F56AF508CE236A6189" xlink:type="locator" />
    <link:definitionArc order="7" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_5CD80D9A49727436227A08CE2368BC2D" xlink:to="loc_us-gaap_ClassOfWarrantOrRightExercisePriceOfWarrantsOrRights1_47BABF30C56D31F56AF508CE236A6189" 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_62CCDA796A950E34881D08CE236A5E5F" xlink:type="locator" />
    <link:definitionArc order="8" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_5CD80D9A49727436227A08CE2368BC2D" xlink:to="loc_us-gaap_DerivativeLiabilities_62CCDA796A950E34881D08CE236A5E5F" 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_BF6ECECA50E0956CB47208CE236A2AA2" xlink:type="locator" />
    <link:definitionArc order="9" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_5CD80D9A49727436227A08CE2368BC2D" xlink:to="loc_us-gaap_DebtInstrumentMeasurementInput_BF6ECECA50E0956CB47208CE236A2AA2" 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_6EBAC171454D0473A55A08CE236A306E" xlink:type="locator" />
    <link:definitionArc order="10" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_5CD80D9A49727436227A08CE2368BC2D" xlink:to="loc_us-gaap_WarrantsAndRightsOutstandingTerm_6EBAC171454D0473A55A08CE236A306E" xlink:type="arc" />
    <link:loc xlink:href="anab-20181231.xsd#anab_DebtInstrumentPeriodicPaymentNumberOfPrincipalAndInterestPayments" xlink:label="loc_anab_DebtInstrumentPeriodicPaymentNumberOfPrincipalAndInterestPayments_25A2FCC191C787332CAB08CE236AE2E2" xlink:type="locator" />
    <link:definitionArc order="11" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_5CD80D9A49727436227A08CE2368BC2D" xlink:to="loc_anab_DebtInstrumentPeriodicPaymentNumberOfPrincipalAndInterestPayments_25A2FCC191C787332CAB08CE236AE2E2" 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_D588A2E921F864F0F53D08CE236B1644" xlink:type="locator" />
    <link:definitionArc order="12" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_5CD80D9A49727436227A08CE2368BC2D" xlink:to="loc_us-gaap_DebtInstrumentBasisSpreadOnVariableRate1_D588A2E921F864F0F53D08CE236B1644" xlink:type="arc" />
    <link:loc xlink:href="anab-20181231.xsd#anab_DebtInstrumentInterestRateAtEndOfPeriod" xlink:label="loc_anab_DebtInstrumentInterestRateAtEndOfPeriod_4026A5A01662BB569BE508CE236B20AD" xlink:type="locator" />
    <link:definitionArc order="13" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_5CD80D9A49727436227A08CE2368BC2D" xlink:to="loc_anab_DebtInstrumentInterestRateAtEndOfPeriod_4026A5A01662BB569BE508CE236B20AD" 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_21B41246881ECDFDADB008CE236BADF0" xlink:type="locator" />
    <link:definitionArc order="14" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_5CD80D9A49727436227A08CE2368BC2D" xlink:to="loc_us-gaap_DebtInstrumentPeriodicPaymentTermsBalloonPaymentToBePaid_21B41246881ECDFDADB008CE236BADF0" 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_ED8482512E5A2E620C0008CE236B343D" xlink:type="locator" />
    <link:definitionArc order="15" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_5CD80D9A49727436227A08CE2368BC2D" xlink:to="loc_us-gaap_NotesPayable_ED8482512E5A2E620C0008CE236B343D" 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_C941375C41A3AFEF263108CE236B3727" xlink:type="locator" />
    <link:definitionArc order="16" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_5CD80D9A49727436227A08CE2368BC2D" xlink:to="loc_us-gaap_DebtInstrumentUnamortizedDiscountPremiumAndDebtIssuanceCostsNet_C941375C41A3AFEF263108CE236B3727" 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_8481E200F031A44AA9C808CE236BA27C" xlink:type="locator" />
    <link:definitionArc order="17" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_5CD80D9A49727436227A08CE2368BC2D" xlink:to="loc_us-gaap_NotesPayableCurrent_8481E200F031A44AA9C808CE236BA27C" 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_8B5DA7C887729B47D18D08CE236C10C9" xlink:type="locator" />
    <link:definitionArc order="18" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_5CD80D9A49727436227A08CE2368BC2D" xlink:to="loc_us-gaap_DebtInstrumentInterestRateEffectivePercentage_8B5DA7C887729B47D18D08CE236C10C9" 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_C2CBDFB87B22D9BA4AF808CE236C4A1D" xlink:type="locator" />
    <link:definitionArc order="19" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_5CD80D9A49727436227A08CE2368BC2D" xlink:to="loc_us-gaap_LongTermDebtByMaturityAbstract_C2CBDFB87B22D9BA4AF808CE236C4A1D" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_LongTermDebtMaturitiesRepaymentsOfPrincipalInNextTwelveMonths" xlink:label="loc_us-gaap_LongTermDebtMaturitiesRepaymentsOfPrincipalInNextTwelveMonths_FE48C57F4C669DF0470108CE236CFDCF" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LongTermDebtByMaturityAbstract_C2CBDFB87B22D9BA4AF808CE236C4A1D" xlink:to="loc_us-gaap_LongTermDebtMaturitiesRepaymentsOfPrincipalInNextTwelveMonths_FE48C57F4C669DF0470108CE236CFDCF" 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_0470ABB877C55CF244E308CE236C22F9" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LongTermDebtByMaturityAbstract_C2CBDFB87B22D9BA4AF808CE236C4A1D" xlink:to="loc_us-gaap_LongTermDebtMaturitiesRepaymentsOfPrincipalInYearTwo_0470ABB877C55CF244E308CE236C22F9" xlink:type="arc" />
  </link:definitionLink>
  <link:definitionLink xlink:role="http://www.anaptysbio.com/role/SelectedQuarterlyFinancialDataUnaudited" xlink:type="extended" />
  <link:definitionLink xlink:role="http://www.anaptysbio.com/role/SelectedQuarterlyFinancialDataUnauditedDetails" xlink:type="extended" />
  <link:definitionLink xlink:role="http://www.anaptysbio.com/role/SelectedQuarterlyFinancialDataUnauditedTables" xlink:type="extended" />
  <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_6B20E158FEECBBEA1E45E924A3E525ED" 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_D38BCD2D8F80380F1E87E924A3E3BD6F" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_ClassOfStockLineItems_6B20E158FEECBBEA1E45E924A3E525ED" xlink:to="loc_us-gaap_ScheduleOfStockByClassTable_D38BCD2D8F80380F1E87E924A3E3BD6F" 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_233E6493D79D8EF64515E924A3E3EA6A" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfStockByClassTable_D38BCD2D8F80380F1E87E924A3E3BD6F" xlink:to="loc_us-gaap_StatementEquityComponentsAxis_233E6493D79D8EF64515E924A3E3EA6A" 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_2C200E0F057C878539FCE924A3E4A627_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_StatementEquityComponentsAxis_233E6493D79D8EF64515E924A3E3EA6A" xlink:to="loc_us-gaap_EquityComponentDomain_2C200E0F057C878539FCE924A3E4A627_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_2C200E0F057C878539FCE924A3E4A627" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_StatementEquityComponentsAxis_233E6493D79D8EF64515E924A3E3EA6A" xlink:to="loc_us-gaap_EquityComponentDomain_2C200E0F057C878539FCE924A3E4A627" 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_3D128BB3430B53E80D49E924A3E47941" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityComponentDomain_2C200E0F057C878539FCE924A3E4A627" xlink:to="loc_us-gaap_CommonStockMember_3D128BB3430B53E80D49E924A3E47941" xlink:type="arc" />
    <link:loc xlink:href="anab-20181231.xsd#anab_ClassOfWarrantOrRightNumberOfSecuritiesCalledByWarrantsOrRightsExercised" xlink:label="loc_anab_ClassOfWarrantOrRightNumberOfSecuritiesCalledByWarrantsOrRightsExercised_3F9E32163A2D7BE477C1E924A3E5AFB5" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockLineItems_6B20E158FEECBBEA1E45E924A3E525ED" xlink:to="loc_anab_ClassOfWarrantOrRightNumberOfSecuritiesCalledByWarrantsOrRightsExercised_3F9E32163A2D7BE477C1E924A3E5AFB5" xlink:type="arc" />
    <link:loc xlink:href="anab-20181231.xsd#anab_ClassOfWarrantOrRightNumberOfSecuritiesCalledByWarrantsOrRightsExercisedNoncashExercise" xlink:label="loc_anab_ClassOfWarrantOrRightNumberOfSecuritiesCalledByWarrantsOrRightsExercisedNoncashExercise_B5E54D3614FE89C4FF3EE924A3E5A80F" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockLineItems_6B20E158FEECBBEA1E45E924A3E525ED" xlink:to="loc_anab_ClassOfWarrantOrRightNumberOfSecuritiesCalledByWarrantsOrRightsExercisedNoncashExercise_B5E54D3614FE89C4FF3EE924A3E5A80F" xlink:type="arc" />
    <link:loc xlink:href="anab-20181231.xsd#anab_StockIssuedDuringPeriodSharesIssuedForWarrants" xlink:label="loc_anab_StockIssuedDuringPeriodSharesIssuedForWarrants_997AE23B03A3E20C0D75E924A3E5812C" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockLineItems_6B20E158FEECBBEA1E45E924A3E525ED" xlink:to="loc_anab_StockIssuedDuringPeriodSharesIssuedForWarrants_997AE23B03A3E20C0D75E924A3E5812C" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_StockRepurchasedDuringPeriodShares" xlink:label="loc_us-gaap_StockRepurchasedDuringPeriodShares_B5D147B9597F55CF0CF8E924A3E652E6" xlink:type="locator" />
    <link:definitionArc order="4" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockLineItems_6B20E158FEECBBEA1E45E924A3E525ED" xlink:to="loc_us-gaap_StockRepurchasedDuringPeriodShares_B5D147B9597F55CF0CF8E924A3E652E6" 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_979E530C97C771ABF150E91ECDEF6B1F" 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_E746645FBDA3DABAB75BE91ECDECE0A7" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_ClassOfStockLineItems_979E530C97C771ABF150E91ECDEF6B1F" xlink:to="loc_us-gaap_ScheduleOfStockByClassTable_E746645FBDA3DABAB75BE91ECDECE0A7" 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_B33307EED40F425CE235E91ECE1C13DB" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfStockByClassTable_E746645FBDA3DABAB75BE91ECDECE0A7" xlink:to="loc_us-gaap_PlanNameAxis_B33307EED40F425CE235E91ECE1C13DB" 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_F342CB7E38A50A3C75DFE91ECE1D70DE_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_PlanNameAxis_B33307EED40F425CE235E91ECE1C13DB" xlink:to="loc_us-gaap_PlanNameDomain_F342CB7E38A50A3C75DFE91ECE1D70DE_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_F342CB7E38A50A3C75DFE91ECE1D70DE" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_PlanNameAxis_B33307EED40F425CE235E91ECE1C13DB" xlink:to="loc_us-gaap_PlanNameDomain_F342CB7E38A50A3C75DFE91ECE1D70DE" xlink:type="arc" />
    <link:loc xlink:href="anab-20181231.xsd#anab_EquityIncentivePlan2017Member" xlink:label="loc_anab_EquityIncentivePlan2017Member_6566D98731A2D5F21E04E91ECFB8C0CB" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PlanNameDomain_F342CB7E38A50A3C75DFE91ECE1D70DE" xlink:to="loc_anab_EquityIncentivePlan2017Member_6566D98731A2D5F21E04E91ECFB8C0CB" xlink:type="arc" />
    <link:loc xlink:href="anab-20181231.xsd#anab_EmployeeStockPurchasePlan2017Member" xlink:label="loc_anab_EmployeeStockPurchasePlan2017Member_7582BE6CCAA8969E2AF0E91ECFCDBAB0" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PlanNameDomain_F342CB7E38A50A3C75DFE91ECE1D70DE" xlink:to="loc_anab_EmployeeStockPurchasePlan2017Member_7582BE6CCAA8969E2AF0E91ECFCDBAB0" 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_D514E53DA0155A2BF12BE8E1C1D8C324" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockLineItems_979E530C97C771ABF150E91ECDEF6B1F" xlink:to="loc_us-gaap_CommonStockNumberOfSharesParValueAndOtherDisclosuresAbstract_D514E53DA0155A2BF12BE8E1C1D8C324" 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_FB5207417A974EF4CD09E8E1C1D95A31" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CommonStockNumberOfSharesParValueAndOtherDisclosuresAbstract_D514E53DA0155A2BF12BE8E1C1D8C324" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingNumber_FB5207417A974EF4CD09E8E1C1D95A31" 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_2B7EA6CB253887D1D3B7E8E1C1D9E30F" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockLineItems_979E530C97C771ABF150E91ECDEF6B1F" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfSharesAvailableForGrant_2B7EA6CB253887D1D3B7E8E1C1D9E30F" 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_ADB14E8FE41892DD39BFE8E1C1DA48D3" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockLineItems_979E530C97C771ABF150E91ECDEF6B1F" xlink:to="loc_us-gaap_CommonStockCapitalSharesReservedForFutureIssuance_ADB14E8FE41892DD39BFE8E1C1DA48D3" 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:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_NewAccountingPronouncementsOrChangeInAccountingPrincipleLineItems" xlink:label="loc_us-gaap_NewAccountingPronouncementsOrChangeInAccountingPrincipleLineItems_5D14C00E3A53BD4D91660CFCB2369CF9" xlink:type="locator" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_NewAccountingPronouncementsOrChangeInAccountingPrincipleTable" xlink:label="loc_us-gaap_NewAccountingPronouncementsOrChangeInAccountingPrincipleTable_AE4AE965E4179FEED07B0CFCB2326CBF" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_NewAccountingPronouncementsOrChangeInAccountingPrincipleLineItems_5D14C00E3A53BD4D91660CFCB2369CF9" xlink:to="loc_us-gaap_NewAccountingPronouncementsOrChangeInAccountingPrincipleTable_AE4AE965E4179FEED07B0CFCB2326CBF" 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_RangeAxis" xlink:label="loc_srt_RangeAxis_9364307534C637B6BC8C0CFCB232D90D" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_NewAccountingPronouncementsOrChangeInAccountingPrincipleTable_AE4AE965E4179FEED07B0CFCB2326CBF" xlink:to="loc_srt_RangeAxis_9364307534C637B6BC8C0CFCB232D90D" 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_C767A2FAC3B27D8F625C0CFCB233AD80_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_RangeAxis_9364307534C637B6BC8C0CFCB232D90D" xlink:to="loc_srt_RangeMember_C767A2FAC3B27D8F625C0CFCB233AD80_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_C767A2FAC3B27D8F625C0CFCB233AD80" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_RangeAxis_9364307534C637B6BC8C0CFCB232D90D" xlink:to="loc_srt_RangeMember_C767A2FAC3B27D8F625C0CFCB233AD80" 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_8B948AFBE6655D44901E0CFCB233186F" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_RangeMember_C767A2FAC3B27D8F625C0CFCB233AD80" xlink:to="loc_srt_MinimumMember_8B948AFBE6655D44901E0CFCB233186F" 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_C1057ECAF501E3AD65F90CFCB2334B4F" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_RangeMember_C767A2FAC3B27D8F625C0CFCB233AD80" xlink:to="loc_srt_MaximumMember_C1057ECAF501E3AD65F90CFCB2334B4F" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_StatementScenarioAxis" xlink:label="loc_us-gaap_StatementScenarioAxis_FE6399EB32587D1576420CFCB234577A" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_NewAccountingPronouncementsOrChangeInAccountingPrincipleTable_AE4AE965E4179FEED07B0CFCB2326CBF" xlink:to="loc_us-gaap_StatementScenarioAxis_FE6399EB32587D1576420CFCB234577A" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_ScenarioUnspecifiedDomain" xlink:label="loc_us-gaap_ScenarioUnspecifiedDomain_1ED4D56081DD1075D1620CFCB23405C5_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_StatementScenarioAxis_FE6399EB32587D1576420CFCB234577A" xlink:to="loc_us-gaap_ScenarioUnspecifiedDomain_1ED4D56081DD1075D1620CFCB23405C5_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_ScenarioUnspecifiedDomain" xlink:label="loc_us-gaap_ScenarioUnspecifiedDomain_1ED4D56081DD1075D1620CFCB23405C5" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_StatementScenarioAxis_FE6399EB32587D1576420CFCB234577A" xlink:to="loc_us-gaap_ScenarioUnspecifiedDomain_1ED4D56081DD1075D1620CFCB23405C5" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_ScenarioForecastMember" xlink:label="loc_us-gaap_ScenarioForecastMember_78B296AF599FF94B3F940CFCB234F4BA" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ScenarioUnspecifiedDomain_1ED4D56081DD1075D1620CFCB23405C5" xlink:to="loc_us-gaap_ScenarioForecastMember_78B296AF599FF94B3F940CFCB234F4BA" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_AdjustmentsForNewAccountingPronouncementsAxis" xlink:label="loc_us-gaap_AdjustmentsForNewAccountingPronouncementsAxis_E05A957A9C967D5FB0EE0CFCB235C4E7" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_NewAccountingPronouncementsOrChangeInAccountingPrincipleTable_AE4AE965E4179FEED07B0CFCB2326CBF" xlink:to="loc_us-gaap_AdjustmentsForNewAccountingPronouncementsAxis_E05A957A9C967D5FB0EE0CFCB235C4E7" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_TypeOfAdoptionMember" xlink:label="loc_us-gaap_TypeOfAdoptionMember_AE8919DA98619B8C31950CFCB235C7B7_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_AdjustmentsForNewAccountingPronouncementsAxis_E05A957A9C967D5FB0EE0CFCB235C4E7" xlink:to="loc_us-gaap_TypeOfAdoptionMember_AE8919DA98619B8C31950CFCB235C7B7_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_TypeOfAdoptionMember" xlink:label="loc_us-gaap_TypeOfAdoptionMember_AE8919DA98619B8C31950CFCB235C7B7" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_AdjustmentsForNewAccountingPronouncementsAxis_E05A957A9C967D5FB0EE0CFCB235C4E7" xlink:to="loc_us-gaap_TypeOfAdoptionMember_AE8919DA98619B8C31950CFCB235C7B7" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_AccountingStandardsUpdate201602Member" xlink:label="loc_us-gaap_AccountingStandardsUpdate201602Member_441B17F6C87637F4C0010CFCB235EC67" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TypeOfAdoptionMember_AE8919DA98619B8C31950CFCB235C7B7" xlink:to="loc_us-gaap_AccountingStandardsUpdate201602Member_441B17F6C87637F4C0010CFCB235EC67" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_PropertyPlantAndEquipmentUsefulLife" xlink:label="loc_us-gaap_PropertyPlantAndEquipmentUsefulLife_62C091A2F202696309130CFCB2367D8E" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_NewAccountingPronouncementsOrChangeInAccountingPrincipleLineItems_5D14C00E3A53BD4D91660CFCB2369CF9" xlink:to="loc_us-gaap_PropertyPlantAndEquipmentUsefulLife_62C091A2F202696309130CFCB2367D8E" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_TangibleAssetImpairmentCharges" xlink:label="loc_us-gaap_TangibleAssetImpairmentCharges_1A84962D574F82BBB08C0CFCB2370BBC" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_NewAccountingPronouncementsOrChangeInAccountingPrincipleLineItems_5D14C00E3A53BD4D91660CFCB2369CF9" xlink:to="loc_us-gaap_TangibleAssetImpairmentCharges_1A84962D574F82BBB08C0CFCB2370BBC" xlink:type="arc" />
    <link:loc xlink:href="anab-20181231.xsd#anab_IncomeTaxIncentiveResearchAndDevelopmentRevenueThresholdForReimbursablePeriod" xlink:label="loc_anab_IncomeTaxIncentiveResearchAndDevelopmentRevenueThresholdForReimbursablePeriod_386DDD4B3A39B0A0E6DF0CFCB2374AB8" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_NewAccountingPronouncementsOrChangeInAccountingPrincipleLineItems_5D14C00E3A53BD4D91660CFCB2369CF9" xlink:to="loc_anab_IncomeTaxIncentiveResearchAndDevelopmentRevenueThresholdForReimbursablePeriod_386DDD4B3A39B0A0E6DF0CFCB2374AB8" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_OperatingLeaseRightOfUseAsset" xlink:label="loc_us-gaap_OperatingLeaseRightOfUseAsset_22C8C4C350B15CBC54930D08B25FC86F" xlink:type="locator" />
    <link:definitionArc order="4" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_NewAccountingPronouncementsOrChangeInAccountingPrincipleLineItems_5D14C00E3A53BD4D91660CFCB2369CF9" xlink:to="loc_us-gaap_OperatingLeaseRightOfUseAsset_22C8C4C350B15CBC54930D08B25FC86F" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_OperatingLeaseLiability" xlink:label="loc_us-gaap_OperatingLeaseLiability_8BF6A75CA6FB2D8D8DB60D08F92B59F8" xlink:type="locator" />
    <link:definitionArc order="5" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_NewAccountingPronouncementsOrChangeInAccountingPrincipleLineItems_5D14C00E3A53BD4D91660CFCB2369CF9" xlink:to="loc_us-gaap_OperatingLeaseLiability_8BF6A75CA6FB2D8D8DB60D08F92B59F8" xlink:type="arc" />
  </link:definitionLink>
  <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_8AE5E46829B1994A12FF13936CC9CBE0" 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_FFB4BD0BD2880E91B45B13936CC1381B" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareLineItems_8AE5E46829B1994A12FF13936CC9CBE0" xlink:to="loc_us-gaap_ScheduleOfAntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareTable_FFB4BD0BD2880E91B45B13936CC1381B" 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_3A3BEDD528EA11C4AF9A13936CC17D79" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfAntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareTable_FFB4BD0BD2880E91B45B13936CC1381B" xlink:to="loc_us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareByAntidilutiveSecuritiesAxis_3A3BEDD528EA11C4AF9A13936CC17D79" 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_41A676F31C1D2815B72713936CC25743_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareByAntidilutiveSecuritiesAxis_3A3BEDD528EA11C4AF9A13936CC17D79" xlink:to="loc_us-gaap_AntidilutiveSecuritiesNameDomain_41A676F31C1D2815B72713936CC25743_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_41A676F31C1D2815B72713936CC25743" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareByAntidilutiveSecuritiesAxis_3A3BEDD528EA11C4AF9A13936CC17D79" xlink:to="loc_us-gaap_AntidilutiveSecuritiesNameDomain_41A676F31C1D2815B72713936CC25743" 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_E54DEAEC8412E83FD51513936CC2F781" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AntidilutiveSecuritiesNameDomain_41A676F31C1D2815B72713936CC25743" xlink:to="loc_us-gaap_ConvertiblePreferredStockMember_E54DEAEC8412E83FD51513936CC2F781" 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_377D9F175B1ED8AC251113936CC382D5" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AntidilutiveSecuritiesNameDomain_41A676F31C1D2815B72713936CC25743" xlink:to="loc_us-gaap_EmployeeStockOptionMember_377D9F175B1ED8AC251113936CC382D5" 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_0D3D9325C5CBB8850E0D13936CC30D47" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AntidilutiveSecuritiesNameDomain_41A676F31C1D2815B72713936CC25743" xlink:to="loc_us-gaap_WarrantMember_0D3D9325C5CBB8850E0D13936CC30D47" 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_50EAC8C00DA414A37F6D13936CC308DB" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfAntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareTable_FFB4BD0BD2880E91B45B13936CC1381B" xlink:to="loc_us-gaap_StatementClassOfStockAxis_50EAC8C00DA414A37F6D13936CC308DB" 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_5F8E1022B39635D6093313936CC3A861_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_StatementClassOfStockAxis_50EAC8C00DA414A37F6D13936CC308DB" xlink:to="loc_us-gaap_ClassOfStockDomain_5F8E1022B39635D6093313936CC3A861_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_5F8E1022B39635D6093313936CC3A861" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_StatementClassOfStockAxis_50EAC8C00DA414A37F6D13936CC308DB" xlink:to="loc_us-gaap_ClassOfStockDomain_5F8E1022B39635D6093313936CC3A861" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2018/elts/us-gaap-2018-01-31.xsd#us-gaap_PreferredStockMember" xlink:label="loc_us-gaap_PreferredStockMember_B86BE2E5B34B17A1D6B813936CC36E31" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockDomain_5F8E1022B39635D6093313936CC3A861" xlink:to="loc_us-gaap_PreferredStockMember_B86BE2E5B34B17A1D6B813936CC36E31" 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_693092CC110A370FD8A913936CC9A7E6" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockDomain_5F8E1022B39635D6093313936CC3A861" xlink:to="loc_us-gaap_CommonStockMember_693092CC110A370FD8A913936CC9A7E6" 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_2109D7497D4252B4C5CF13936CC9636C" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareLineItems_8AE5E46829B1994A12FF13936CC9CBE0" xlink:to="loc_us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareAmount_2109D7497D4252B4C5CF13936CC9636C" xlink:type="arc" />
  </link:definitionLink>
  <link:definitionLink xlink:role="http://www.anaptysbio.com/role/SummaryOfSignificantAccountingPoliciesTables" xlink:type="extended" />
</link:linkbase>
