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  <xs:element id="prax_ScheduleOfCommonStockReservedForFutureIssuanceLineItems" abstract="true" name="ScheduleOfCommonStockReservedForFutureIssuanceLineItems" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="xbrli:stringItemType"/>
  <xs:element id="prax_SaleOfStockAggregateAuthorizedAmount" abstract="false" name="SaleOfStockAggregateAuthorizedAmount" nillable="true" xbrli:periodType="duration" xbrli:balance="debit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="prax_NumberOfVotesPerOneShare" abstract="false" name="NumberOfVotesPerOneShare" nillable="true" xbrli:periodType="instant" substitutionGroup="xbrli:item" type="xbrli:integerItemType"/>
  <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_April2024FollowOnOfferingMember" abstract="true" name="April2024FollowOnOfferingMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="prax_October2025FollowOnOfferingMember" abstract="true" name="October2025FollowOnOfferingMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <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_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_A2024EmployeeStockIncentivePlanMember" abstract="true" name="A2024EmployeeStockIncentivePlanMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="prax_A2020EmployeeStockPurchasePlanMember" abstract="true" name="A2020EmployeeStockPurchasePlanMember" 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_LicensingAgreementsProfitSharePaymentsMember" abstract="true" name="LicensingAgreementsProfitSharePaymentsMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="prax_MilestonePaymentMember" abstract="true" name="MilestonePaymentMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="prax_RogconMember" abstract="true" name="RogconMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="prax_IonisMember" abstract="true" name="IonisMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="prax_EffectiveIncomeTaxRateReconciliationNondeductibleExpenseExecutiveCompensationAmount" abstract="false" name="EffectiveIncomeTaxRateReconciliationNondeductibleExpenseExecutiveCompensationAmount" nillable="true" xbrli:periodType="duration" xbrli:balance="debit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="prax_EffectiveIncomeTaxRateReconciliationNondeductibleExpenseExecutiveCompensationPercent" abstract="false" name="EffectiveIncomeTaxRateReconciliationNondeductibleExpenseExecutiveCompensationPercent" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:percentItemType"/>
  <xs:element id="prax_DeferredTaxAssetsTaxDeferredExpenseAmortization" abstract="false" name="DeferredTaxAssetsTaxDeferredExpenseAmortization" nillable="true" xbrli:periodType="instant" xbrli:balance="debit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="prax_DeferredTaxAssetsOperatingLeaseRightOfUseAsset" abstract="false" name="DeferredTaxAssetsOperatingLeaseRightOfUseAsset" nillable="true" xbrli:periodType="instant" xbrli:balance="debit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="prax_DeferredTaxLiabilitiesOperatingLeaseRightOfUseAsset" abstract="false" name="DeferredTaxLiabilitiesOperatingLeaseRightOfUseAsset" nillable="true" xbrli:periodType="instant" xbrli:balance="credit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <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:element id="prax_January2026PublicOfferingMember" abstract="true" name="January2026PublicOfferingMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
</xs:schema>
