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<!-- Creation Date :2022-03-01T13:48:35.0691+00:00 -->
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  <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_StockIssuedDuringPeriodSharesExerciseOfWarrants" name="StockIssuedDuringPeriodSharesExerciseOfWarrants" type="xbrli:sharesItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false"/>
  <xsd:element id="phat_StockIssuedDuringPeriodValueExerciseOfWarrants" name="StockIssuedDuringPeriodValueExerciseOfWarrants" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false" xbrli:balance="credit"/>
  <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_UnpaidUnderwrittenPublicOfferingCosts" name="UnpaidUnderwrittenPublicOfferingCosts" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false" xbrli:balance="credit"/>
  <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_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_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_DrugProductOrSubstanceMember" name="DrugProductOrSubstanceMember" 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_LenderWarrantsMember" name="LenderWarrantsMember" 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_OpenMarketSaleAgreementWithJefferiesLLCMember" name="OpenMarketSaleAgreementWithJefferiesLLCMember" 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_PrepaidLeasePaymentsMember" name="PrepaidLeasePaymentsMember" 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_StockOptionsAndPerformanceBasedAwardsMember" name="StockOptionsAndPerformanceBasedAwardsMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="phat_StockOptionsAndPerformanceBasedUnitsMember" name="StockOptionsAndPerformanceBasedUnitsMember" 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_TakedaWarrantsMember" name="TakedaWarrantsMember" 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_TermLoansAggregatePrincipalAmountTranchesFourMember" name="TermLoansAggregatePrincipalAmountTranchesFourMember" 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_TermLoansAggregatePrincipalAmountTranchesThreeMember" name="TermLoansAggregatePrincipalAmountTranchesThreeMember" 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_WarrantsLiabilitiesMember" name="WarrantsLiabilitiesMember" 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_SummaryOfSupplementalBalanceSheetInformationRelatedToOperatingLeasesTableTextBlock" name="SummaryOfSupplementalBalanceSheetInformationRelatedToOperatingLeasesTableTextBlock" type="dtr-types:textBlockItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false"/>
</xsd:schema>
