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  <xsd:element id="phat_AccruedInterestOnRevenueInterestFinancingLiability" name="AccruedInterestOnRevenueInterestFinancingLiability" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false" xbrli:balance="debit"/>
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  <xsd:element id="phat_PercentageOfInvestorShareOfRoyaltyInNetSales" name="PercentageOfInvestorShareOfRoyaltyInNetSales" type="dtr-types:percentItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false"/>
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  <xsd:element id="phat_PurchaseObligationDueInFirstTwentyFourMonths" name="PurchaseObligationDueInFirstTwentyFourMonths" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="instant" nillable="true" abstract="false" xbrli:balance="credit"/>
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  <xsd:element id="phat_RelatedPartyTransactionSharedOperatingExpensesDueToTransactionsWithRelatedParty" name="RelatedPartyTransactionSharedOperatingExpensesDueToTransactionsWithRelatedParty" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false" xbrli:balance="debit"/>
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  <xsd:element id="phat_RepurchaseRightLapseShares" name="RepurchaseRightLapseShares" type="xbrli:decimalItemType" substitutionGroup="xbrli:item" xbrli:periodType="instant" nillable="true" abstract="false"/>
  <xsd:element id="phat_ResearchAndDevelopmentExpenseRelatedParty" name="ResearchAndDevelopmentExpenseRelatedParty" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false" xbrli:balance="debit"/>
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  <xsd:element id="phat_RevenueInterestFinancingLiabilityCurrent" name="RevenueInterestFinancingLiabilityCurrent" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="instant" nillable="true" abstract="false" xbrli:balance="credit"/>
  <xsd:element id="phat_RevenueInterestFinancingLiabilityNoncurrent" name="RevenueInterestFinancingLiabilityNoncurrent" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="instant" nillable="true" abstract="false" xbrli:balance="credit"/>
  <xsd:element id="phat_RoyaltyPaymentsAndPayables" name="RoyaltyPaymentsAndPayables" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false" xbrli:balance="credit"/>
  <xsd:element id="phat_SalesCommissionPayableAsAPercentageOfSaleOfGrossSalesPricePerShare" name="SalesCommissionPayableAsAPercentageOfSaleOfGrossSalesPricePerShare" type="dtr-types:percentItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false"/>
  <xsd:element id="phat_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsShareVesting" name="ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsShareVesting" type="xbrli:sharesItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false"/>
  <xsd:element id="phat_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfSharesAvailableForGrantAnnualIncrease" name="ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfSharesAvailableForGrantAnnualIncrease" type="xbrli:sharesItemType" substitutionGroup="xbrli:item" xbrli:periodType="instant" nillable="true" abstract="false"/>
  <xsd:element id="phat_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsAndOtherThanOptionsForfeituresAndExpirationsInPeriod" name="ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsAndOtherThanOptionsForfeituresAndExpirationsInPeriod" type="xbrli:sharesItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false"/>
  <xsd:element id="phat_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsAndOtherThanOptionsGrantsInPeriodGross" name="ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsAndOtherThanOptionsGrantsInPeriodGross" type="xbrli:sharesItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false"/>
  <xsd:element id="phat_ShareBasedCompensationArrangementByShareBasedPaymentAwardStockOptionsExercisedAndSharesVested" name="ShareBasedCompensationArrangementByShareBasedPaymentAwardStockOptionsExercisedAndSharesVested" type="xbrli:sharesItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false"/>
  <xsd:element id="phat_ShareBasedCompensationArrangementsByShareBasedPaymentAwardOptionsExercisesAndSharesVestedInPeriodWeightedAverageExercisePrice" name="ShareBasedCompensationArrangementsByShareBasedPaymentAwardOptionsExercisesAndSharesVestedInPeriodWeightedAverageExercisePrice" type="dtr-types:perShareItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false"/>
  <xsd:element id="phat_SharesAggregateRepurchasePrice" name="SharesAggregateRepurchasePrice" type="dtr-types:perShareItemType" substitutionGroup="xbrli:item" xbrli:periodType="instant" nillable="true" abstract="false"/>
  <xsd:element id="phat_SharesIssuedPricePerShareAfterDeductions" name="SharesIssuedPricePerShareAfterDeductions" type="dtr-types:perShareItemType" substitutionGroup="xbrli:item" xbrli:periodType="instant" nillable="true" abstract="false"/>
  <xsd:element id="phat_StockIssuedDuringPeriodSharesCashlessExerciseOfCommonStockWarrants" name="StockIssuedDuringPeriodSharesCashlessExerciseOfCommonStockWarrants" type="xbrli:sharesItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false"/>
  <xsd:element id="phat_StockRepurchaseProgramExpirationMonthAndYear" name="StockRepurchaseProgramExpirationMonthAndYear" type="xbrli:gYearMonthItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false"/>
  <xsd:element id="phat_StockRepurchaseProgramNumberOfSharesRightLapse" name="StockRepurchaseProgramNumberOfSharesRightLapse" type="xbrli:sharesItemType" substitutionGroup="xbrli:item" xbrli:periodType="instant" nillable="true" abstract="false"/>
  <xsd:element id="phat_TaxCutsAndJobsActResearchAndDevelopmentExpendituresAmortizationPeriod" name="TaxCutsAndJobsActResearchAndDevelopmentExpendituresAmortizationPeriod" type="xbrli:durationItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false"/>
  <xsd:element id="phat_WarrantsExpirationDate" name="WarrantsExpirationDate" type="xbrli:dateItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false"/>
  <xsd:element id="phat_CommitmentsAndContingenciesLineItems" name="CommitmentsAndContingenciesLineItems" type="xbrli:stringItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="phat_OrganizationBasisOfPresentationAndSummaryOfSignificantAccountingPoliciesLineItems" name="OrganizationBasisOfPresentationAndSummaryOfSignificantAccountingPoliciesLineItems" type="xbrli:stringItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="phat_AmendmentToLoanAgreementMember" name="AmendmentToLoanAgreementMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="phat_ATMOfferingProgramMember" name="ATMOfferingProgramMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="phat_ClinicalManufacturingServicesMember" name="ClinicalManufacturingServicesMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="phat_CommercialSupplyAgreementAndTemporaryServicesAgreementMember" name="CommercialSupplyAgreementAndTemporaryServicesAgreementMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="phat_CommercialSupplyAgreementsMember" name="CommercialSupplyAgreementsMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="phat_CommonStockWarrantMember" name="CommonStockWarrantMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="phat_ComputerEquipmentAndSoftwareMember" name="ComputerEquipmentAndSoftwareMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="phat_DrugProductsMember" name="DrugProductsMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="phat_EmployeesMember" name="EmployeesMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="phat_EmployeeStockPurchasePlanMember" name="EmployeeStockPurchasePlanMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="phat_FollowOnPublicOfferingMember" name="FollowOnPublicOfferingMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="phat_FoundersMember" name="FoundersMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="phat_FrazierLifeSciencesIXLimitedPartnerMember" name="FrazierLifeSciencesIXLimitedPartnerMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="phat_HerculesAndSvbTermLoanMember" name="HerculesAndSvbTermLoanMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="phat_HerculesLoanAgreementAndSiliconValleyBankTermLoanMember" name="HerculesLoanAgreementAndSiliconValleyBankTermLoanMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="phat_HerculesLoanAgreementMember" name="HerculesLoanAgreementMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="phat_InitialInvestorsNqSagardAndHerculesMember" name="InitialInvestorsNqSagardAndHerculesMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="phat_LoanAgreementMember" name="LoanAgreementMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="phat_OfficeSpaceMember" name="OfficeSpaceMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="phat_OpenMarketSaleAgreementWithJefferiesLLCMember" name="OpenMarketSaleAgreementWithJefferiesLLCMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="phat_PassengerVehiclesMember" name="PassengerVehiclesMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="phat_PaymentInKindPikInterestRateMember" name="PaymentInKindPikInterestRateMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="phat_PCIPharmaServicesMember" name="PCIPharmaServicesMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="phat_RevenueInterestFinancingAgreementFundingCommitmentOnOrBeforeMarchThirtyOneTwoThousandAndTwentyFourMember" name="RevenueInterestFinancingAgreementFundingCommitmentOnOrBeforeMarchThirtyOneTwoThousandAndTwentyFourMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="phat_RevenueInterestFinancingAgreementFundingUponAchievementOfSalesMilestoneAtAnyTimePriorToJuneThirtyTwoThousandAndTwentyFourMember" name="RevenueInterestFinancingAgreementFundingUponAchievementOfSalesMilestoneAtAnyTimePriorToJuneThirtyTwoThousandAndTwentyFourMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="phat_RevenueInterestFinancingAgreementFundingUponFdaApprovalAtAnyTimePriorToDecemberThirtyOneTwoThousandAndTwentyTwoMember" name="RevenueInterestFinancingAgreementFundingUponFdaApprovalAtAnyTimePriorToDecemberThirtyOneTwoThousandAndTwentyTwoMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="phat_RevenueInterestFinancingAgreementMember" name="RevenueInterestFinancingAgreementMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="phat_RevenueInterestFinancingAgreementPercentageOnInvestmentAmountOnDecemberThirtyOneTwoThousandAndThirtySevenMember" name="RevenueInterestFinancingAgreementPercentageOnInvestmentAmountOnDecemberThirtyOneTwoThousandAndThirtySevenMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="phat_RevenueInterestFinancingAgreementPercentageOnInvestmentAmountOnDecemberThirtyOneTwoThousandAndTwentyEightMember" name="RevenueInterestFinancingAgreementPercentageOnInvestmentAmountOnDecemberThirtyOneTwoThousandAndTwentyEightMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="phat_RevenueInterestFinancingAgreementUponOccurrenceOfAChangeInControlEventEarlierOfAprilOneTwoThousandAndTwentyFourOrFdaApprovalIfOccurrenceIsThereafterToMayThreeTwoThousandAndTwentyThreeMember" name="RevenueInterestFinancingAgreementUponOccurrenceOfAChangeInControlEventEarlierOfAprilOneTwoThousandAndTwentyFourOrFdaApprovalIfOccurrenceIsThereafterToMayThreeTwoThousandAndTwentyThreeMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="phat_RevenueInterestFinancingAgreementUponOccurrenceOfAChangeInControlEventEarlierOfAprilOneTwoThousandAndTwentyFourOrFdaApprovalIfOccurrencePriorToMayThreeTwoThousandAndTwentyThreeMember" name="RevenueInterestFinancingAgreementUponOccurrenceOfAChangeInControlEventEarlierOfAprilOneTwoThousandAndTwentyFourOrFdaApprovalIfOccurrencePriorToMayThreeTwoThousandAndTwentyThreeMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="phat_RevenueInterestFinancingAgreementUponOccurrenceOfAChangeInControlEventEarlierOfAprilOneTwoThousandAndTwentyFourOrFdaApprovalMember" name="RevenueInterestFinancingAgreementUponOccurrenceOfAChangeInControlEventEarlierOfAprilOneTwoThousandAndTwentyFourOrFdaApprovalMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="phat_RevenueInterestFinancingAgreementUponOccurrenceOfEventOfDefaultAfterAprilOneTwoThousandAndTwentyEightMember" name="RevenueInterestFinancingAgreementUponOccurrenceOfEventOfDefaultAfterAprilOneTwoThousandAndTwentyEightMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="phat_RevenueInterestFinancingAgreementUponOccurrenceOfEventOfDefaultBetweenAprilOneTwoThousandAndTwentyFiveAndAprilOneTwoThousandAndTwentyEightMember" name="RevenueInterestFinancingAgreementUponOccurrenceOfEventOfDefaultBetweenAprilOneTwoThousandAndTwentyFiveAndAprilOneTwoThousandAndTwentyEightMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="phat_RevenueInterestFinancingAgreementUponOccurrenceOfEventOfDefaultPriorToAprilOneTwoThousandAndTwentyFiveMember" name="RevenueInterestFinancingAgreementUponOccurrenceOfEventOfDefaultPriorToAprilOneTwoThousandAndTwentyFiveMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="phat_ShareBasedPaymentArrangementEmployeeAndNonemployeeMember" name="ShareBasedPaymentArrangementEmployeeAndNonemployeeMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="phat_SiliconValleyBankTermLoanMember" name="SiliconValleyBankTermLoanMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="phat_StockOptionPerformanceBasedUnitAndRestrictedStockUnitMember" name="StockOptionPerformanceBasedUnitAndRestrictedStockUnitMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="phat_StockOptionsAndPerformanceBasedAwardsMember" name="StockOptionsAndPerformanceBasedAwardsMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="phat_TakedaLicenseAgreementMember" name="TakedaLicenseAgreementMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="phat_TakedaPharmaceuticalCompanyLimitedMember" name="TakedaPharmaceuticalCompanyLimitedMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="phat_TemporaryServicesAgreementMember" name="TemporaryServicesAgreementMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="phat_TermLoanAdvanceMember" name="TermLoanAdvanceMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="phat_TermLoanFirstAdvanceMember" name="TermLoanFirstAdvanceMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="phat_TermLoanMember" name="TermLoanMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="phat_TermLoansAggregatePrincipalAmountTranchesOneMember" name="TermLoansAggregatePrincipalAmountTranchesOneMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="phat_TermLoansAggregatePrincipalAmountTranchesThreeAndFourMember" name="TermLoansAggregatePrincipalAmountTranchesThreeAndFourMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="phat_TermLoansAggregatePrincipalAmountTranchesTwoMember" name="TermLoansAggregatePrincipalAmountTranchesTwoMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="phat_TwoThousandNineteenEquityIncentivePlanMember" name="TwoThousandNineteenEquityIncentivePlanMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="phat_TwoThousandNineteenIncentiveAwardPlanMember" name="TwoThousandNineteenIncentiveAwardPlanMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="phat_UnvestedSharesMember" name="UnvestedSharesMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="phat_CommitmentsAndContingenciesTable" name="CommitmentsAndContingenciesTable" type="xbrli:stringItemType" substitutionGroup="xbrldt:hypercubeItem" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="phat_OrganizationBasisOfPresentationAndSummaryOfSignificantAccountingPoliciesTable" name="OrganizationBasisOfPresentationAndSummaryOfSignificantAccountingPoliciesTable" type="xbrli:stringItemType" substitutionGroup="xbrldt:hypercubeItem" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="phat_CommonStockReservedForFutureIssuancesTableTableTextBlock" name="CommonStockReservedForFutureIssuancesTableTableTextBlock" type="dtr-types:textBlockItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false"/>
  <xsd:element id="phat_ComponentOfBalanceSheetDisclosureTextBlock" name="ComponentOfBalanceSheetDisclosureTextBlock" type="dtr-types:textBlockItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false"/>
  <xsd:element id="phat_LiquidityAndCapitalResourcesPolicyTextBlock" name="LiquidityAndCapitalResourcesPolicyTextBlock" type="dtr-types:textBlockItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false"/>
  <xsd:element id="phat_OrganizationAndBasisOfPresentationPolicyTextBlock" name="OrganizationAndBasisOfPresentationPolicyTextBlock" type="dtr-types:textBlockItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false"/>
  <xsd:element id="phat_RevenueInterestFinancingLiabilityPolicyTextBlock" name="RevenueInterestFinancingLiabilityPolicyTextBlock" type="dtr-types:textBlockItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false"/>
  <xsd:element id="phat_RevenueInterestFinancingLiabilityTextBlock" name="RevenueInterestFinancingLiabilityTextBlock" type="dtr-types:textBlockItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false"/>
  <xsd:element id="phat_ScheduleOfRevenueInterestFinancingLiabilityTableTextBlock" name="ScheduleOfRevenueInterestFinancingLiabilityTableTextBlock" type="dtr-types:textBlockItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false"/>
  <xsd:element id="phat_SummaryOfSupplementalBalanceSheetInformationRelatedToOperatingLeasesTableTextBlock" name="SummaryOfSupplementalBalanceSheetInformationRelatedToOperatingLeasesTableTextBlock" type="dtr-types:textBlockItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false"/>
</xsd:schema>
