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  <xsd:element id="atha_ProceedsFromExerciseOfCommonStockOptionsAndCommonStockWarrants" name="ProceedsFromExerciseOfCommonStockOptionsAndCommonStockWarrants" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false" xbrli:balance="debit"/>
  <xsd:element id="atha_ProceedsFromIssuanceFollowOnPublicOffering" name="ProceedsFromIssuanceFollowOnPublicOffering" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false" xbrli:balance="debit"/>
  <xsd:element id="atha_ProceedsFromIssuanceOfConvertiblePreferredStockAndCommonStockWarrants" name="ProceedsFromIssuanceOfConvertiblePreferredStockAndCommonStockWarrants" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false" xbrli:balance="debit"/>
  <xsd:element id="atha_ProceedsFromSalesOfConvertiblePreferredStockAndStockWarrantsNetOfIssuanceCosts" name="ProceedsFromSalesOfConvertiblePreferredStockAndStockWarrantsNetOfIssuanceCosts" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false" xbrli:balance="debit"/>
  <xsd:element id="atha_ProceedsToCommonStockWarrantsIssuedInConvertiblePreferredStockFinancing" name="ProceedsToCommonStockWarrantsIssuedInConvertiblePreferredStockFinancing" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false" xbrli:balance="debit"/>
  <xsd:element id="atha_RecognitionOfDerivativeLiabilityUponIssuanceOfConvertibleNotes" name="RecognitionOfDerivativeLiabilityUponIssuanceOfConvertibleNotes" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false" xbrli:balance="credit"/>
  <xsd:element id="atha_RecognitionOfWarrantLiabilityInConnectionWithConvertiblePreferredStockFinancing" name="RecognitionOfWarrantLiabilityInConnectionWithConvertiblePreferredStockFinancing" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false" xbrli:balance="credit"/>
  <xsd:element id="atha_RemainingGrantAmount" name="RemainingGrantAmount" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false" xbrli:balance="credit"/>
  <xsd:element id="atha_RoyaltyObligation" name="RoyaltyObligation" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="instant" nillable="true" abstract="false" xbrli:balance="credit"/>
  <xsd:element id="atha_ShareBasedCompensationArrangementByShareBasedPaymentAwardMaximumPercentageOfPayrollDeductionsForQualifyingWagesOrStatutoryLimit" name="ShareBasedCompensationArrangementByShareBasedPaymentAwardMaximumPercentageOfPayrollDeductionsForQualifyingWagesOrStatutoryLimit" type="dtr-types:percentItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false"/>
  <xsd:element id="atha_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsAndRestrictedStockUnitGranted" name="ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsAndRestrictedStockUnitGranted" type="xbrli:sharesItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false"/>
  <xsd:element id="atha_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsAndRestrictedStockUnitsForfeitedCancelledOrExpired" name="ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsAndRestrictedStockUnitsForfeitedCancelledOrExpired" type="xbrli:sharesItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false"/>
  <xsd:element id="atha_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriodFairValue" name="ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriodFairValue" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false" xbrli:balance="credit"/>
  <xsd:element id="atha_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsWeightedAverageGrantDateFairValueOfOptionsGranted" name="ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsWeightedAverageGrantDateFairValueOfOptionsGranted" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false" xbrli:balance="debit"/>
  <xsd:element id="atha_ShareBasedCompensationArrangementByShareBasedPaymentAwardOtherThanOptionsGrantDateFairValue" name="ShareBasedCompensationArrangementByShareBasedPaymentAwardOtherThanOptionsGrantDateFairValue" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false" xbrli:balance="debit"/>
  <xsd:element id="atha_ShareBasedCompensationArrangementByShareBasedPaymentAwardSubjectToRepurchaseUponDiscontinuedService" name="ShareBasedCompensationArrangementByShareBasedPaymentAwardSubjectToRepurchaseUponDiscontinuedService" type="xbrli:sharesItemType" substitutionGroup="xbrli:item" xbrli:periodType="instant" nillable="true" abstract="false"/>
  <xsd:element id="atha_ShareBasedCompensationMaximumAnnualIncreaseInNumberOfSharesThatMayBeIssuedUnderPlan" name="ShareBasedCompensationMaximumAnnualIncreaseInNumberOfSharesThatMayBeIssuedUnderPlan" type="xbrli:sharesItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false"/>
  <xsd:element id="atha_ShareBasedCompensationPercentageOfNumberSharesOfCommonStockIssuedAndOutstandingOnImmediateProceeding" name="ShareBasedCompensationPercentageOfNumberSharesOfCommonStockIssuedAndOutstandingOnImmediateProceeding" type="dtr-types:percentItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false"/>
  <xsd:element id="atha_ShareBasedCompensationSharesAuthorizedUnderStockOptionPlansExercisePrice" name="ShareBasedCompensationSharesAuthorizedUnderStockOptionPlansExercisePrice" type="dtr-types:perShareItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false"/>
  <xsd:element id="atha_ShortTermInvestmentsMaturityTerm" name="ShortTermInvestmentsMaturityTerm" type="xbrli:durationItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false"/>
  <xsd:element id="atha_StockIssuedDuringPeriodSharesConversionOfConvertiblePreferredStock" name="StockIssuedDuringPeriodSharesConversionOfConvertiblePreferredStock" type="xbrli:sharesItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false"/>
  <xsd:element id="atha_StockIssuedDuringPeriodSharesWarrantsExercised" name="StockIssuedDuringPeriodSharesWarrantsExercised" type="xbrli:sharesItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false"/>
  <xsd:element id="atha_StockIssuedDuringPeriodValueConversionOfConvertiblePreferredStock" name="StockIssuedDuringPeriodValueConversionOfConvertiblePreferredStock" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false" xbrli:balance="credit"/>
  <xsd:element id="atha_StockIssuedDuringPeriodValueWarrantsExercised" name="StockIssuedDuringPeriodValueWarrantsExercised" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false" xbrli:balance="credit"/>
  <xsd:element id="atha_TemporaryEquityStockAndWarrantsIssuedDuringPeriodSharesPreferredStockAndWarrants" name="TemporaryEquityStockAndWarrantsIssuedDuringPeriodSharesPreferredStockAndWarrants" type="xbrli:sharesItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false"/>
  <xsd:element id="atha_TemporaryEquityStockAndWarrantsIssuedDuringPeriodValuePreferredStockAndWarrants" name="TemporaryEquityStockAndWarrantsIssuedDuringPeriodValuePreferredStockAndWarrants" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false" xbrli:balance="credit"/>
  <xsd:element id="atha_TemporaryEquityStockIssuedDuringPeriodSharesConversionOfConvertiblePreferredStock" name="TemporaryEquityStockIssuedDuringPeriodSharesConversionOfConvertiblePreferredStock" type="xbrli:sharesItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false"/>
  <xsd:element id="atha_TemporaryEquityStockIssuedDuringPeriodSharesConversionOfConvertibleSecurities" name="TemporaryEquityStockIssuedDuringPeriodSharesConversionOfConvertibleSecurities" type="xbrli:sharesItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false"/>
  <xsd:element id="atha_TemporaryEquityStockIssuedDuringPeriodValueConversionOfConvertiblePreferredStock" name="TemporaryEquityStockIssuedDuringPeriodValueConversionOfConvertiblePreferredStock" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false" xbrli:balance="debit"/>
  <xsd:element id="atha_TemporaryEquityStockIssuedDuringPeriodValueConversionOfConvertibleSecurities" name="TemporaryEquityStockIssuedDuringPeriodValueConversionOfConvertibleSecurities" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false" xbrli:balance="credit"/>
  <xsd:element id="atha_TenantImprovementAllowanceReceivable" name="TenantImprovementAllowanceReceivable" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="instant" nillable="true" abstract="false" xbrli:balance="credit"/>
  <xsd:element id="atha_UnbilledGrantReceivableCurrent" name="UnbilledGrantReceivableCurrent" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="instant" nillable="true" abstract="false" xbrli:balance="debit"/>
  <xsd:element id="atha_BasisOfPresentationAndSignificantAccountingPoliciesLineItems" name="BasisOfPresentationAndSignificantAccountingPoliciesLineItems" type="xbrli:stringItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="atha_CommitmentsAndContingenciesLineItems" name="CommitmentsAndContingenciesLineItems" type="xbrli:stringItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="atha_DescriptionOfBusinessLineItems" name="DescriptionOfBusinessLineItems" type="xbrli:stringItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="atha_AdvisorsMember" name="AdvisorsMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="atha_AlzheimersAssociationMember" name="AlzheimersAssociationMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="atha_AlzheimerSAssociationPartCloudResearchGrantMember" name="AlzheimerSAssociationPartCloudResearchGrantMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="atha_BothellWashingtonMember" name="BothellWashingtonMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="atha_ClassOfWarrantOrRightPurchasePriceOneMember" name="ClassOfWarrantOrRightPurchasePriceOneMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="atha_CommonStockWarrantsMember" name="CommonStockWarrantsMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="atha_ConvertiblePreferredStockCommonStockWarrantsOrSeriesBConvertiblePreferredStockWarrantsMember" name="ConvertiblePreferredStockCommonStockWarrantsOrSeriesBConvertiblePreferredStockWarrantsMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="atha_ConvertiblePreferredStockOnConvertedBasisMember" name="ConvertiblePreferredStockOnConvertedBasisMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="atha_ConvertiblePreferredStockWarrantLiabilityMember" name="ConvertiblePreferredStockWarrantLiabilityMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="atha_EmployeesAndDirectorsMember" name="EmployeesAndDirectorsMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="atha_EmployeeStockPurchasePlanMember" name="EmployeeStockPurchasePlanMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="atha_ExercisePriceFourMember" name="ExercisePriceFourMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="atha_ExercisePriceOneMember" name="ExercisePriceOneMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="atha_ExercisePriceThreeMember" name="ExercisePriceThreeMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="atha_ExercisePriceTwoMember" name="ExercisePriceTwoMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="atha_FollowOnPublicOfferingMember" name="FollowOnPublicOfferingMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="atha_FurnitureFixturesAndComputerEquipmentMember" name="FurnitureFixturesAndComputerEquipmentMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="atha_GrantLiabilityMember" name="GrantLiabilityMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="atha_JawandhaVAthiraPharmaIncMember" name="JawandhaVAthiraPharmaIncMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="atha_LaboratoryAndOfficeFacilitiesMember" name="LaboratoryAndOfficeFacilitiesMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="atha_LaboratoryEquipmentMember" name="LaboratoryEquipmentMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="atha_LicensedProductsMember" name="LicensedProductsMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="atha_LongTermInvestmentsMember" name="LongTermInvestmentsMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="atha_NationalInstituteOnAgingOfTheNationalInstitutesOfHealthMember" name="NationalInstituteOnAgingOfTheNationalInstitutesOfHealthMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="atha_NationalInstitutesOfHealthGrantMember" name="NationalInstitutesOfHealthGrantMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="atha_NonEmployeesMember" name="NonEmployeesMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="atha_NonVestedRestrictedStockUnitsMember" name="NonVestedRestrictedStockUnitsMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="atha_PhaseThreeClinicalTrailInitiationOfLicenseAgreementMember" name="PhaseThreeClinicalTrailInitiationOfLicenseAgreementMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="atha_PhaseTwoClinicalTrailInitiationOfLicenseAgreementMember" name="PhaseTwoClinicalTrailInitiationOfLicenseAgreementMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="atha_SeriesB1ConvertiblePreferredStockMember" name="SeriesB1ConvertiblePreferredStockMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="atha_SeriesBConvertiblePreferredStockMember" name="SeriesBConvertiblePreferredStockMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="atha_SeriesBConvertiblePreferredStockWarrantMember" name="SeriesBConvertiblePreferredStockWarrantMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="atha_SharesAvailableForFutureGrantUnderEmployeeStockPurchasePlanMember" name="SharesAvailableForFutureGrantUnderEmployeeStockPurchasePlanMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="atha_SharesAvailableForFutureGrantUnderTwoThousandTwentyEquityIncentivePlanMember" name="SharesAvailableForFutureGrantUnderTwoThousandTwentyEquityIncentivePlanMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="atha_SharesIssuableUponTheExerciseOfOutstandingCommonStockOptionsAndTheVestingOfOutstandingCommonRestrictedStockUnitsGrantedMember" name="SharesIssuableUponTheExerciseOfOutstandingCommonStockOptionsAndTheVestingOfOutstandingCommonRestrictedStockUnitsGrantedMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="atha_SlyneVAthiraPharmaIncMember" name="SlyneVAthiraPharmaIncMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="atha_StockOptionsToPurchaseCommonStockMember" name="StockOptionsToPurchaseCommonStockMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="atha_TowThousandAndTwentyEmployeeStockPurchasePlanMember" name="TowThousandAndTwentyEmployeeStockPurchasePlanMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="atha_TwoThousandAndTwentyEquityIncentivePlanMember" name="TwoThousandAndTwentyEquityIncentivePlanMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="atha_TwoThousandTwentyEmployeeStockPurchasePlanMember" name="TwoThousandTwentyEmployeeStockPurchasePlanMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="atha_UnsecuredConvertibleNotesMember" name="UnsecuredConvertibleNotesMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="atha_UnvestedRestrictedStockAwardsMember" name="UnvestedRestrictedStockAwardsMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="atha_WangVAthiraPharmaIncMember" name="WangVAthiraPharmaIncMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="atha_WashingtonLifeServicesDiscoveryFundGrantAgreementMember" name="WashingtonLifeServicesDiscoveryFundGrantAgreementMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="atha_WashingtonStateUniversityLicenseAgreementMember" name="WashingtonStateUniversityLicenseAgreementMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="atha_ConvertiblePreferredStockWarrantLiabilityPolicyTextBlock" name="ConvertiblePreferredStockWarrantLiabilityPolicyTextBlock" type="dtr-types:textBlockItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false"/>
  <xsd:element id="atha_EmergingGrowthCompanyStatusPolicyTextBlock" name="EmergingGrowthCompanyStatusPolicyTextBlock" type="dtr-types:textBlockItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false"/>
  <xsd:element id="atha_GrantIncomePolicyTextBlock" name="GrantIncomePolicyTextBlock" type="dtr-types:textBlockItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false"/>
  <xsd:element id="atha_BasisOfPresentationAndSignificantAccountingPoliciesTable" name="BasisOfPresentationAndSignificantAccountingPoliciesTable" type="xbrli:stringItemType" substitutionGroup="xbrldt:hypercubeItem" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="atha_CommitmentsAndContingenciesTable" name="CommitmentsAndContingenciesTable" type="xbrli:stringItemType" substitutionGroup="xbrldt:hypercubeItem" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="atha_DescriptionOfBusinessTable" name="DescriptionOfBusinessTable" type="xbrli:stringItemType" substitutionGroup="xbrldt:hypercubeItem" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="atha_ScheduleOfGrantIncomeTableTextBlock" name="ScheduleOfGrantIncomeTableTextBlock" type="dtr-types:textBlockItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false"/>
  <xsd:element id="atha_ScheduleOfReservedSharesOfCommonStockForFutureIssuanceTableTextBlock" name="ScheduleOfReservedSharesOfCommonStockForFutureIssuanceTableTextBlock" type="dtr-types:textBlockItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false"/>
  <xsd:element id="atha_ScheduleOfShareBasedCompensationArrangementSharesAvailableForGrantTableTextBlock" name="ScheduleOfShareBasedCompensationArrangementSharesAvailableForGrantTableTextBlock" type="dtr-types:textBlockItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false"/>
  <xsd:element id="atha_ScheduleOfUnbilledGrantReceivablesTableTextBlock" name="ScheduleOfUnbilledGrantReceivablesTableTextBlock" type="dtr-types:textBlockItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false"/>
  <xsd:element id="atha_DerivativeLiabilityConvertibleNotesDiscountAndAmortizationPolicyTextBlock" name="DerivativeLiabilityConvertibleNotesDiscountAndAmortizationPolicyTextBlock" type="dtr-types:textBlockItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false"/>
  <xsd:element id="atha_GrantLiabilityPolicyTextBlock" name="GrantLiabilityPolicyTextBlock" type="dtr-types:textBlockItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false"/>
</xsd:schema>
