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  <xs:element id="prax_FollowOnOfferingMember" abstract="true" name="FollowOnOfferingMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="prax_LicenseAndCollaborationAgreementMember" abstract="true" name="LicenseAndCollaborationAgreementMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="prax_StockIssuedDuringPeriodSharesExerciseOfWarrants" abstract="false" name="StockIssuedDuringPeriodSharesExerciseOfWarrants" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="xbrli:sharesItemType"/>
  <xs:element id="prax_StockIssuanceCosts" abstract="false" name="StockIssuanceCosts" nillable="true" xbrli:periodType="duration" xbrli:balance="debit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="prax_CollaborationAndLicenseAgreementNoncashExpense" abstract="false" name="CollaborationAndLicenseAgreementNoncashExpense" nillable="true" xbrli:periodType="duration" xbrli:balance="debit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="prax_IncreaseDecreaseInOperatingLeaseLiabilities" abstract="false" name="IncreaseDecreaseInOperatingLeaseLiabilities" nillable="true" xbrli:periodType="duration" xbrli:balance="debit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="prax_StockIssuanceCostsIncurredButNotYetPaid" abstract="false" name="StockIssuanceCostsIncurredButNotYetPaid" nillable="true" xbrli:periodType="duration" xbrli:balance="credit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="prax_UnauditedInterimCondensedConsolidatedFinancialInformationPolicyTextBlock" abstract="false" name="UnauditedInterimCondensedConsolidatedFinancialInformationPolicyTextBlock" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:textBlockItemType"/>
  <xs:element id="prax_CommonStockWarrantsPolicyTextBlock" abstract="false" name="CommonStockWarrantsPolicyTextBlock" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:textBlockItemType"/>
  <xs:element id="prax_ScheduleOfCommonStockReservedForFutureIssuanceTableTextBlock" abstract="false" name="ScheduleOfCommonStockReservedForFutureIssuanceTableTextBlock" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:textBlockItemType"/>
  <xs:element id="prax_NumberOfPlatforms" abstract="false" name="NumberOfPlatforms" nillable="true" xbrli:periodType="instant" substitutionGroup="xbrli:item" type="xbrli:integerItemType"/>
  <xs:element id="prax_NumberOfProductCandidates" abstract="false" name="NumberOfProductCandidates" nillable="true" xbrli:periodType="instant" substitutionGroup="xbrli:item" type="xbrli:integerItemType"/>
  <xs:element id="prax_CashEquivalentsAccumulatedGrossUnrealizedGainCurrentBeforeTax" abstract="false" name="CashEquivalentsAccumulatedGrossUnrealizedGainCurrentBeforeTax" nillable="true" xbrli:periodType="instant" xbrli:balance="credit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="prax_CashEquivalentsAccumulatedGrossUnrealizedLossCurrentBeforeTax" abstract="false" name="CashEquivalentsAccumulatedGrossUnrealizedLossCurrentBeforeTax" nillable="true" xbrli:periodType="instant" xbrli:balance="debit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="prax_CashEquivalentsFairValueDisclosure" abstract="false" name="CashEquivalentsFairValueDisclosure" nillable="true" xbrli:periodType="instant" xbrli:balance="debit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="prax_DebtSecuritiesAvailableForSaleAccumulatedGrossUnrealizedGainCurrentBeforeTax" abstract="false" name="DebtSecuritiesAvailableForSaleAccumulatedGrossUnrealizedGainCurrentBeforeTax" nillable="true" xbrli:periodType="instant" xbrli:balance="credit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="prax_DebtSecuritiesAvailableForSaleAccumulatedGrossUnrealizedLossCurrentBeforeTax" abstract="false" name="DebtSecuritiesAvailableForSaleAccumulatedGrossUnrealizedLossCurrentBeforeTax" nillable="true" xbrli:periodType="instant" xbrli:balance="debit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="prax_CashEquivalentsAtCarryingValueAndDebtSecuritiesAvailableForSaleAmortizedCost" abstract="false" name="CashEquivalentsAtCarryingValueAndDebtSecuritiesAvailableForSaleAmortizedCost" nillable="true" xbrli:periodType="instant" xbrli:balance="debit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="prax_CashEquivalentsAndDebtSecuritiesAvailableForSaleAccumulatedGrossUnrealizedGainCurrentBeforeTax" abstract="false" name="CashEquivalentsAndDebtSecuritiesAvailableForSaleAccumulatedGrossUnrealizedGainCurrentBeforeTax" nillable="true" xbrli:periodType="instant" xbrli:balance="credit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="prax_CashEquivalentsAndDebtSecuritiesAvailableForSaleAccumulatedGrossUnrealizedLossCurrentBeforeTax" abstract="false" name="CashEquivalentsAndDebtSecuritiesAvailableForSaleAccumulatedGrossUnrealizedLossCurrentBeforeTax" nillable="true" xbrli:periodType="instant" xbrli:balance="debit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="prax_CashEquivalentsAndDebtSecuritiesAvailableForSaleFairValueDisclosure" abstract="false" name="CashEquivalentsAndDebtSecuritiesAvailableForSaleFairValueDisclosure" nillable="true" xbrli:periodType="instant" xbrli:balance="debit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="prax_AccruedExternalResearchAndDevelopmentExpensesCurrent" abstract="false" name="AccruedExternalResearchAndDevelopmentExpensesCurrent" nillable="true" xbrli:periodType="instant" xbrli:balance="credit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="prax_AccruedPersonnelRelatedExpensesCurrent" abstract="false" name="AccruedPersonnelRelatedExpensesCurrent" nillable="true" xbrli:periodType="instant" xbrli:balance="credit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="prax_OfficeSpaceInBostonMassachusettsMember" abstract="true" name="OfficeSpaceInBostonMassachusettsMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="prax_PercentageIncreaseInAnnualBaseRent" abstract="false" name="PercentageIncreaseInAnnualBaseRent" nillable="true" xbrli:periodType="instant" substitutionGroup="xbrli:item" type="dtr-types:percentItemType"/>
  <xs:element id="prax_UCBMember" abstract="true" name="UCBMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="prax_TenaciaMember" abstract="true" name="TenaciaMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="prax_OptionExerciseFeeMember" abstract="true" name="OptionExerciseFeeMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="prax_UpfrontPaymentMember" abstract="true" name="UpfrontPaymentMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="prax_RevenueRemainingPerformanceObligationVariableConsiderationAmount" abstract="false" name="RevenueRemainingPerformanceObligationVariableConsiderationAmount" nillable="true" xbrli:periodType="instant" xbrli:balance="credit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="prax_NumberOfPerformanceObligations" abstract="false" name="NumberOfPerformanceObligations" nillable="true" xbrli:periodType="instant" substitutionGroup="xbrli:item" type="xbrli:integerItemType"/>
  <xs:element id="prax_SaleOfStockVolumeWeightedAveragePricePremium" abstract="false" name="SaleOfStockVolumeWeightedAveragePricePremium" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:percentItemType"/>
  <xs:element id="prax_SaleOfStockVolumeWeightedAveragePriceDuration" abstract="false" name="SaleOfStockVolumeWeightedAveragePriceDuration" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="xbrli:durationItemType"/>
  <xs:element id="prax_ProceedsFromCollaborationArrangement" abstract="false" name="ProceedsFromCollaborationArrangement" nillable="true" xbrli:periodType="duration" xbrli:balance="credit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="prax_SaleOfStockValueTransferred" abstract="false" name="SaleOfStockValueTransferred" nillable="true" xbrli:periodType="duration" xbrli:balance="debit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="prax_SaleOfStockValueTransferredInExcessOfConsiderationReceived" abstract="false" name="SaleOfStockValueTransferredInExcessOfConsiderationReceived" nillable="true" xbrli:periodType="duration" xbrli:balance="credit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="prax_ScheduleOfCommonStockReservedForFutureIssuanceTable" abstract="true" name="ScheduleOfCommonStockReservedForFutureIssuanceTable" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrldt:hypercubeItem" type="xbrli:stringItemType"/>
  <xs:element id="prax_January2024FollowOnOfferingMember" abstract="true" name="January2024FollowOnOfferingMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="prax_January2024PublicOfferingMember" abstract="true" name="January2024PublicOfferingMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="prax_April2024PublicOfferingMember" abstract="true" name="April2024PublicOfferingMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="prax_PreFundedWarrantMember" abstract="true" name="PreFundedWarrantMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="prax_ScheduleOfCommonStockReservedForFutureIssuanceLineItems" abstract="true" name="ScheduleOfCommonStockReservedForFutureIssuanceLineItems" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="xbrli:stringItemType"/>
  <xs:element id="prax_SaleOfStockSharesAggregateAuthorizedAmount" abstract="false" name="SaleOfStockSharesAggregateAuthorizedAmount" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="xbrli:sharesItemType"/>
  <xs:element id="prax_PercentageOfOwnershipHeldBySoleOwner" abstract="false" name="PercentageOfOwnershipHeldBySoleOwner" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:percentItemType"/>
  <xs:element id="prax_PercentageOfOwnershipHeldBySoleOwnerAndAffiliates" abstract="false" name="PercentageOfOwnershipHeldBySoleOwnerAndAffiliates" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:percentItemType"/>
  <xs:element id="prax_ChangeInPercentageOfOwnership" abstract="false" name="ChangeInPercentageOfOwnership" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:percentItemType"/>
  <xs:element id="prax_NoticeOfChangeTerm" abstract="false" name="NoticeOfChangeTerm" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="xbrli:durationItemType"/>
  <xs:element id="prax_ClassOfWarrantsOrRightsExercised" abstract="false" name="ClassOfWarrantsOrRightsExercised" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="xbrli:sharesItemType"/>
  <xs:element id="prax_TwentyTwentyEmployeeStockIncentivePlanMember" abstract="true" name="TwentyTwentyEmployeeStockIncentivePlanMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="prax_TwentyTwentyEmployeeStockPurchasePlanMember" abstract="true" name="TwentyTwentyEmployeeStockPurchasePlanMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="prax_InducementPlanMember" abstract="true" name="InducementPlanMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="prax_April2024FollowOnOfferingMember" abstract="true" name="April2024FollowOnOfferingMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="prax_A2020EmployeeStockIncentivePlanMember" abstract="true" name="A2020EmployeeStockIncentivePlanMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="prax_A2017EmployeeStockIncentivePlanMember" abstract="true" name="A2017EmployeeStockIncentivePlanMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="prax_UnvestedRestrictedStockUnitsMember" abstract="true" name="UnvestedRestrictedStockUnitsMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="prax_ShareBasedCompensationArrangementByShareBasedPaymentAwardIncreaseDecreaseInSharesAuthorized" abstract="false" name="ShareBasedCompensationArrangementByShareBasedPaymentAwardIncreaseDecreaseInSharesAuthorized" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="xbrli:sharesItemType"/>
  <xs:element id="prax_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsIssuedInPeriod" abstract="false" name="ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsIssuedInPeriod" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="xbrli:sharesItemType"/>
  <xs:element id="prax_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsIssuedInPeriodWeightedAverageGrantDateFairValue" abstract="false" name="ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsIssuedInPeriodWeightedAverageGrantDateFairValue" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:perShareItemType"/>
  <xs:element id="prax_ReportableSegmentMember" abstract="true" name="ReportableSegmentMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="prax_UlixacaltamideMember" abstract="true" name="UlixacaltamideMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="prax_VormatrigineMember" abstract="true" name="VormatrigineMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="prax_RelutrigineMember" abstract="true" name="RelutrigineMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="prax_ElsunersenMember" abstract="true" name="ElsunersenMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="prax_OtherEarlyStateAssetsMember" abstract="true" name="OtherEarlyStateAssetsMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
</xs:schema>
