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  <xsd:element id="alxo_RightOfUseAssetAcquiredUnderLeasesAbstract" name="RightOfUseAssetAcquiredUnderLeasesAbstract" type="xbrli:stringItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="alxo_AccruedClinicalAndNonClinicalCostsCurrent" name="AccruedClinicalAndNonClinicalCostsCurrent" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="instant" nillable="true" abstract="false" xbrli:balance="credit"/>
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  <xsd:element id="alxo_AdditionalCommonStockCapitalSharesReservedForFutureIssuance" name="AdditionalCommonStockCapitalSharesReservedForFutureIssuance" type="xbrli:sharesItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false"/>
  <xsd:element id="alxo_AnnualInterestRateOfAdditionalPaymentsOverLifeOfLease" name="AnnualInterestRateOfAdditionalPaymentsOverLifeOfLease" type="dtr-types:percentItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false"/>
  <xsd:element id="alxo_CashEquivalentsAvailableForSale" name="CashEquivalentsAvailableForSale" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="instant" nillable="true" abstract="false" xbrli:balance="debit"/>
  <xsd:element id="alxo_FairValueAssetsAndLiabilitiesTransfersAmount" name="FairValueAssetsAndLiabilitiesTransfersAmount" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false" xbrli:balance="credit"/>
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  <xsd:element id="alxo_LeaseOperatingLeaseCommencementPeriodTwo" name="LeaseOperatingLeaseCommencementPeriodTwo" type="xbrli:gYearMonthItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false"/>
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  <xsd:element id="alxo_LesseeOperatingLeaseLeaseholdImprovements" name="LesseeOperatingLeaseLeaseholdImprovements" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false" xbrli:balance="debit"/>
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  <xsd:element id="alxo_NumberOfPendingOrThreatenedLitigation" name="NumberOfPendingOrThreatenedLitigation" type="xbrli:integerItemType" substitutionGroup="xbrli:item" xbrli:periodType="instant" nillable="true" abstract="false"/>
  <xsd:element id="alxo_OperatingFinanceLeaseRightOfUseAssetAmortizationExpense" name="OperatingFinanceLeaseRightOfUseAssetAmortizationExpense" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false" xbrli:balance="debit"/>
  <xsd:element id="alxo_OperatingLeaseAnnualLeaseExpense" name="OperatingLeaseAnnualLeaseExpense" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false" xbrli:balance="debit"/>
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  <xsd:element id="alxo_RelatedPartyAgreementAutomaticallyRenewalAdditionalTermUnlessTerminated" name="RelatedPartyAgreementAutomaticallyRenewalAdditionalTermUnlessTerminated" type="xbrli:durationItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false"/>
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  <xsd:element id="alxo_EmployeeStockPurchasePlanSharesAuthorizedForFutureIssuanceMember" name="EmployeeStockPurchasePlanSharesAuthorizedForFutureIssuanceMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="alxo_LongTermInvestmentCorporateDebtSecuritiesMember" name="LongTermInvestmentCorporateDebtSecuritiesMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="alxo_LongTermInvestmentsMember" name="LongTermInvestmentsMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="alxo_MasterServiceAgreementMember" name="MasterServiceAgreementMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="alxo_OfficeAndLaboratorySpaceOneMember" name="OfficeAndLaboratorySpaceOneMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="alxo_OfficeSpaceOneMember" name="OfficeSpaceOneMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
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  <xsd:element id="alxo_PrepaidContractManufacturingCostsMember" name="PrepaidContractManufacturingCostsMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
  <xsd:element id="alxo_ResearchAndDevelopmentServicesAgreementMember" name="ResearchAndDevelopmentServicesAgreementMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
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  <xsd:element id="alxo_StockOptionsIssuedAndOutstandingMember" name="StockOptionsIssuedAndOutstandingMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true"/>
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  <xsd:element id="alxo_LesseeOperatingAndFinancingLeasesTextBlock" name="LesseeOperatingAndFinancingLeasesTextBlock" type="dtr-types:textBlockItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false"/>
  <xsd:element id="alxo_ScheduleOfAccruedExpensesAndOtherCurrentLiabilitiesTableTextBlock" name="ScheduleOfAccruedExpensesAndOtherCurrentLiabilitiesTableTextBlock" type="dtr-types:textBlockItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false"/>
  <xsd:element id="alxo_ScheduleOfCommonStockReservedForFutureIssuanceTableTextBlock" name="ScheduleOfCommonStockReservedForFutureIssuanceTableTextBlock" type="dtr-types:textBlockItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false"/>
  <xsd:element id="alxo_SupplementalCashFlowInformationRelatedToLeasesTableTextBlock" name="SupplementalCashFlowInformationRelatedToLeasesTableTextBlock" type="dtr-types:textBlockItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false"/>
</xsd:schema>
