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  <xs:element id="plrx_ClassOfWarrantOrRightExercisableAfterBeneficialOwnershipThresholdAnnouncementNumberOfDays" abstract="false" name="ClassOfWarrantOrRightExercisableAfterBeneficialOwnershipThresholdAnnouncementNumberOfDays" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="xbrli:durationItemType"/>
  <xs:element id="plrx_ClassOfWarrantOrRightAcquiringPersonsBeneficialOwnershipThresholdPassiveInvestor" abstract="false" name="ClassOfWarrantOrRightAcquiringPersonsBeneficialOwnershipThresholdPassiveInvestor" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:percentItemType"/>
  <xs:element id="plrx_ClassOfWarrantOrRightAcquiringPersonsBeneficialOwnershipThresholdNonPassiveInvestor" abstract="false" name="ClassOfWarrantOrRightAcquiringPersonsBeneficialOwnershipThresholdNonPassiveInvestor" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:percentItemType"/>
  <xs:element id="plrx_TwoThousandAndTwentyStockOptionsAndIncentivePlanAndTwoThousandTwentyTwoInducementPlanMember" abstract="true" name="TwoThousandAndTwentyStockOptionsAndIncentivePlanAndTwoThousandTwentyTwoInducementPlanMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="plrx_PercentOfOutstandingSharesSharesAddedPerYearToPlan" abstract="false" name="PercentOfOutstandingSharesSharesAddedPerYearToPlan" nillable="true" xbrli:periodType="instant" substitutionGroup="xbrli:item" type="dtr-types:percentItemType"/>
  <xs:element id="plrx_ShareBasedCompensationOptionsUnderPlanMayBeGrantedForPeriods" abstract="false" name="ShareBasedCompensationOptionsUnderPlanMayBeGrantedForPeriods" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="xbrli:durationItemType"/>
  <xs:element id="plrx_ShareBasedCompensationArrangementByShareBasedPaymentAwardExercisePriceWithPurchasePriceOfCommonStockPercentageOfEstimatedGrantDateFairValueForShareholders" abstract="false" name="ShareBasedCompensationArrangementByShareBasedPaymentAwardExercisePriceWithPurchasePriceOfCommonStockPercentageOfEstimatedGrantDateFairValueForShareholders" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:percentItemType"/>
  <xs:element id="plrx_TwoThousandFifteenAndTwoThousandTwentyEquityIncentivePlansAndTwoThousandTwentyTwoInducementPlanMember" abstract="true" name="TwoThousandFifteenAndTwoThousandTwentyEquityIncentivePlansAndTwoThousandTwentyTwoInducementPlanMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="plrx_IncentiveStockOptionsAndNonqualifiedStockOptionsMember" abstract="true" name="IncentiveStockOptionsAndNonqualifiedStockOptionsMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="plrx_UnderlyingCommonStockFairValue" abstract="false" name="UnderlyingCommonStockFairValue" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:perShareItemType"/>
  <xs:element id="plrx_TwoThousandFifteenAndTwoThousandTwentyEquityIncentivePlanMember" abstract="true" name="TwoThousandFifteenAndTwoThousandTwentyEquityIncentivePlanMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="plrx_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsReleasesInPeriod" abstract="false" name="ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsReleasesInPeriod" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="xbrli:sharesItemType"/>
  <xs:element id="plrx_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsReleasedWeightedAverageGrantDateFairValue" abstract="false" name="ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsReleasedWeightedAverageGrantDateFairValue" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:perShareItemType"/>
  <xs:element id="plrx_PerformanceBasedRestrictedStockUnitsMember" abstract="true" name="PerformanceBasedRestrictedStockUnitsMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="plrx_PerformanceBasedRestrictedStockUnitsTSRGoalMember" abstract="true" name="PerformanceBasedRestrictedStockUnitsTSRGoalMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="plrx_EmployeeStockPurchasePlanOfferingPeriod" abstract="false" name="EmployeeStockPurchasePlanOfferingPeriod" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="xbrli:durationItemType"/>
  <xs:element id="plrx_CommonStockFairMarketValuePercentage" abstract="false" name="CommonStockFairMarketValuePercentage" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:percentItemType"/>
  <xs:element id="plrx_EmployeeStockOptionAndPurchasePlanMember" abstract="true" name="EmployeeStockOptionAndPurchasePlanMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="plrx_ValuationAllowanceAsPercentageOnDeferredTaxAssets" abstract="false" name="ValuationAllowanceAsPercentageOnDeferredTaxAssets" nillable="true" xbrli:periodType="instant" substitutionGroup="xbrli:item" type="dtr-types:percentItemType"/>
  <xs:element id="plrx_IncomeTaxExaminationNumberOfExaminationsPending" abstract="false" name="IncomeTaxExaminationNumberOfExaminationsPending" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="xbrli:integerItemType"/>
  <xs:element id="plrx_EffectiveIncomeTaxRateReconciliationNondeductibleExecutiveCompensationSection162mLimitationAmount" abstract="false" name="EffectiveIncomeTaxRateReconciliationNondeductibleExecutiveCompensationSection162mLimitationAmount" nillable="true" xbrli:periodType="duration" xbrli:balance="debit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="plrx_EffectiveIncomeTaxRateReconciliationNondeductibleExecutiveCompensationSection162mLimitation" abstract="false" name="EffectiveIncomeTaxRateReconciliationNondeductibleExecutiveCompensationSection162mLimitation" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:percentItemType"/>
  <xs:element id="plrx_EffectiveIncomeTaxRateReconciliationGeneralBusinessTaxCreditsFederal" abstract="false" name="EffectiveIncomeTaxRateReconciliationGeneralBusinessTaxCreditsFederal" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:percentItemType"/>
  <xs:element id="plrx_DeferredTaxAssetsCapitalizedResearchAndDevelopment" abstract="false" name="DeferredTaxAssetsCapitalizedResearchAndDevelopment" nillable="true" xbrli:periodType="instant" xbrli:balance="debit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="plrx_DeferredTaxAssetsLeaseLiability" abstract="false" name="DeferredTaxAssetsLeaseLiability" nillable="true" xbrli:periodType="instant" xbrli:balance="debit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="plrx_StartingFromJanuary12018Member" abstract="true" name="StartingFromJanuary12018Member" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="plrx_BeforeJanuary12018Member" abstract="true" name="BeforeJanuary12018Member" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="plrx_DeferredTaxAssetsValuationAllowanceRollForward" abstract="true" name="DeferredTaxAssetsValuationAllowanceRollForward" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="xbrli:stringItemType"/>
  <xs:element id="plrx_ReportableSegmentMember" abstract="true" name="ReportableSegmentMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="plrx_ClinicalTrialAndOutsideServiceThirdPartyContractingCosts" abstract="false" name="ClinicalTrialAndOutsideServiceThirdPartyContractingCosts" nillable="true" xbrli:periodType="duration" xbrli:balance="debit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="plrx_ResearchAndDevelopmentExpenseAdjusted" abstract="false" name="ResearchAndDevelopmentExpenseAdjusted" nillable="true" xbrli:periodType="duration" xbrli:balance="debit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="plrx_GeneralAndAdministrativeExpenseAdjusted" abstract="false" name="GeneralAndAdministrativeExpenseAdjusted" nillable="true" xbrli:periodType="duration" xbrli:balance="debit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="plrx_ContractualArrangementsCancellationPeriod" abstract="false" name="ContractualArrangementsCancellationPeriod" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="xbrli:durationItemType"/>
  <xs:element id="plrx_LandlordMember" abstract="true" name="LandlordMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="plrx_PliantTherapeuticsMember" abstract="true" name="PliantTherapeuticsMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="plrx_LeasedSpaceUnderNonCancellableOperatingLease" abstract="false" name="LeasedSpaceUnderNonCancellableOperatingLease" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:areaItemType"/>
  <xs:element id="plrx_LesseeOperatingLeaseLiabilityToBePaidAfterYearFour" abstract="false" name="LesseeOperatingLeaseLiabilityToBePaidAfterYearFour" nillable="true" xbrli:periodType="instant" xbrli:balance="credit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
</xs:schema>
