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  <xs:element id="mgnx_ProceedsfromRoyaltiesPercent" abstract="false" name="ProceedsfromRoyaltiesPercent" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:percentItemType"/>
  <xs:element id="mgnx_ProventionLicenseAgreementMember" abstract="true" name="ProventionLicenseAgreementMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="mgnx_A2018ZaiLabCollaborationAndLicenseAgreementMember" abstract="true" name="A2018ZaiLabCollaborationAndLicenseAgreementMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="mgnx_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfSharesAuthorizedAfterIncrease" abstract="false" name="ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfSharesAuthorizedAfterIncrease" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="xbrli:sharesItemType"/>
  <xs:element id="mgnx_ScheduleOfSupplementalBalanceSheetInformationOperatingLeasesTableTextBlock" abstract="false" name="ScheduleOfSupplementalBalanceSheetInformationOperatingLeasesTableTextBlock" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:textBlockItemType"/>
  <xs:element id="mgnx_StockOptionsAndRestrictedStockUnitsMember" abstract="true" name="StockOptionsAndRestrictedStockUnitsMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="mgnx_AuditorInformationAbstract" abstract="true" name="AuditorInformationAbstract" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="xbrli:stringItemType"/>
  <xs:element id="mgnx_EffectiveIncomeTaxRateReconciliationDeferredTaxAdjustmentsAmount" abstract="false" name="EffectiveIncomeTaxRateReconciliationDeferredTaxAdjustmentsAmount" nillable="true" xbrli:periodType="duration" xbrli:balance="debit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="mgnx_ImabMember" abstract="true" name="ImabMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="mgnx_NationalInstituteOfAllergyAndInfectiousDiseasesMember" abstract="true" name="NationalInstituteOfAllergyAndInfectiousDiseasesMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="mgnx_JanssenCollaborationAndLicenseAgreementMember" abstract="true" name="JanssenCollaborationAndLicenseAgreementMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="mgnx_ZaiLabsCollaborationAndLicenseAgreementMargetuximabMember" abstract="true" name="ZaiLabsCollaborationAndLicenseAgreementMargetuximabMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="mgnx_TotalPotentialValueUnderAgreement" abstract="false" name="TotalPotentialValueUnderAgreement" nillable="true" xbrli:periodType="duration" xbrli:balance="credit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="mgnx_StockIncentivePlan2013Member" abstract="true" name="StockIncentivePlan2013Member" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="mgnx_IncyteCorporationMember" abstract="true" name="IncyteCorporationMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="mgnx_UpfrontAndFixedPayments" abstract="false" name="UpfrontAndFixedPayments" nillable="true" xbrli:periodType="instant" xbrli:balance="debit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="mgnx_ZaiLabsCollaborationAndLicenseAgreementTRIDENTMoleculeMember" abstract="true" name="ZaiLabsCollaborationAndLicenseAgreementTRIDENTMoleculeMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="mgnx_GileadMember" abstract="true" name="GileadMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="mgnx_RevenueFromVariableConsiderationRecognize" abstract="false" name="RevenueFromVariableConsiderationRecognize" nillable="true" xbrli:periodType="duration" xbrli:balance="credit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="mgnx_CollaborativeArrangementTerm" abstract="false" name="CollaborativeArrangementTerm" nillable="true" xbrli:periodType="instant" substitutionGroup="xbrli:item" type="xbrli:durationItemType"/>
  <xs:element id="mgnx_TwoThousandSixteenEmployeeStockPurchasePlanMember" abstract="true" name="TwoThousandSixteenEmployeeStockPurchasePlanMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="mgnx_IMabBiopharmaMember" abstract="true" name="IMabBiopharmaMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="mgnx_OperatingLossCarryforwardsAnnualLimitationAmount" abstract="false" name="OperatingLossCarryforwardsAnnualLimitationAmount" nillable="true" xbrli:periodType="instant" xbrli:balance="debit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="mgnx_RevenuesFromLicenseAgreementsMember" abstract="true" name="RevenuesFromLicenseAgreementsMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="mgnx_PremiumReceivedOnStockPurchase" abstract="false" name="PremiumReceivedOnStockPurchase" nillable="true" xbrli:periodType="duration" xbrli:balance="debit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="mgnx_PotentialDevelopmentandRegulatoryMilestonePaymentsUnderAgreement" abstract="false" name="PotentialDevelopmentandRegulatoryMilestonePaymentsUnderAgreement" nillable="true" xbrli:periodType="instant" xbrli:balance="credit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="mgnx_ASDHealthcareAndOncologySupplyMember" abstract="true" name="ASDHealthcareAndOncologySupplyMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="mgnx_OperatingLossCarryforwardsLimitationsOnUseAmount" abstract="false" name="OperatingLossCarryforwardsLimitationsOnUseAmount" nillable="true" xbrli:periodType="duration" xbrli:balance="debit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="mgnx_EstimatedReimbursementForResearchAndDevelopmentT" abstract="false" name="EstimatedReimbursementForResearchAndDevelopmentT" nillable="true" xbrli:periodType="instant" xbrli:balance="debit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="mgnx_RightOfUseAssetAndLeaseLiabilityIncrease" abstract="false" name="RightOfUseAssetAndLeaseLiabilityIncrease" nillable="true" xbrli:periodType="instant" xbrli:balance="credit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="mgnx_StockIssuedDuringPeriodSharesStockPlanActivity" abstract="false" name="StockIssuedDuringPeriodSharesStockPlanActivity" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="xbrli:sharesItemType"/>
  <xs:element id="mgnx_FutureRevenue" abstract="false" name="FutureRevenue" nillable="true" xbrli:periodType="duration" xbrli:balance="debit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="mgnx_ExercisePriceRangeFromDollars2501To4021MemberMember" abstract="true" name="ExercisePriceRangeFromDollars2501To4021MemberMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
</xs:schema>
