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  <xs:element id="plrx_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriodFairValue" abstract="false" name="ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriodFairValue" nillable="true" xbrli:periodType="duration" xbrli:balance="credit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="plrx_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsRepurchasesInPeriod" abstract="false" name="ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsRepurchasesInPeriod" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="xbrli:sharesItemType"/>
  <xs:element id="plrx_NovartisAgreementRDForIntegrinResearchTargetsMember" abstract="true" name="NovartisAgreementRDForIntegrinResearchTargetsMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="plrx_LicenseAgreementsLineItems" abstract="true" name="LicenseAgreementsLineItems" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="xbrli:stringItemType"/>
  <xs:element id="plrx_ShareBasedCompensationOptionsUnderPlanMayBeGrantedForPeriods" abstract="false" name="ShareBasedCompensationOptionsUnderPlanMayBeGrantedForPeriods" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="xbrli:durationItemType"/>
  <xs:element id="plrx_OtherLosses" abstract="false" name="OtherLosses" nillable="true" xbrli:periodType="duration" xbrli:balance="debit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="plrx_TwoThousandAndTwentyEmployeeStockPurchasePlanMember" abstract="true" name="TwoThousandAndTwentyEmployeeStockPurchasePlanMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="plrx_NovartisAgreementMember" abstract="true" name="NovartisAgreementMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="plrx_TwoThousandTwentyEquityIncentivePlanMember" abstract="true" name="TwoThousandTwentyEquityIncentivePlanMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="plrx_TwoThousandFifteenEquityIncentivePlanMember" abstract="true" name="TwoThousandFifteenEquityIncentivePlanMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="plrx_PaymentsOfDeferredOfferingCosts" abstract="false" name="PaymentsOfDeferredOfferingCosts" nillable="true" xbrli:periodType="duration" xbrli:balance="credit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="plrx_PrepaidResearchAndDevelopmentCurrent" abstract="false" name="PrepaidResearchAndDevelopmentCurrent" nillable="true" xbrli:periodType="instant" xbrli:balance="debit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="plrx_LeaseTermExtensionNoticePeriod" abstract="false" name="LeaseTermExtensionNoticePeriod" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="xbrli:durationItemType"/>
  <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_AccruedResearchAndDevelopmentExpensesCurrent" abstract="false" name="AccruedResearchAndDevelopmentExpensesCurrent" nillable="true" xbrli:periodType="instant" xbrli:balance="credit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="plrx_BaseRentAbatedAmount" abstract="false" name="BaseRentAbatedAmount" nillable="true" xbrli:periodType="duration" xbrli:balance="debit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="plrx_CollaborationAndLicenseAgreementIntegrinResearchTargetsAmount" abstract="false" name="CollaborationAndLicenseAgreementIntegrinResearchTargetsAmount" nillable="true" xbrli:periodType="duration" xbrli:balance="debit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <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_SupplementalCashFlowDisclosuresAbstract" abstract="true" name="SupplementalCashFlowDisclosuresAbstract" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="xbrli:stringItemType"/>
  <xs:element id="plrx_TermLoanFacilityMember" abstract="true" name="TermLoanFacilityMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="plrx_DebtDrawPeriodDomain" abstract="true" name="DebtDrawPeriodDomain" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
</xs:schema>
