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  <xs:element id="mgnx_DrScottKoenigMember" abstract="true" name="DrScottKoenigMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="mgnx_EmployeeStockPurchasePlanMaximumAnnualContributionsPerEmployeePercent" abstract="false" name="EmployeeStockPurchasePlanMaximumAnnualContributionsPerEmployeePercent" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types1:percentItemType"/>
  <xs:element id="mgnx_ShareBasedCompensationArrangementByShareBasedPaymentAwardOfferingPeriod" abstract="false" name="ShareBasedCompensationArrangementByShareBasedPaymentAwardOfferingPeriod" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="xbrli:durationItemType"/>
  <xs:element id="mgnx_ShareBasedCompensationArrangementByShareBasedPaymentAwardAcceleratedVestingPercentageOfUnvestedAwards" abstract="false" name="ShareBasedCompensationArrangementByShareBasedPaymentAwardAcceleratedVestingPercentageOfUnvestedAwards" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:percentItemType"/>
  <xs:element id="mgnx_CombinedServicesAgreementMember" abstract="true" name="CombinedServicesAgreementMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="mgnx_FutureMilestone" abstract="false" name="FutureMilestone" nillable="true" xbrli:periodType="duration" xbrli:balance="debit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="mgnx_DomesticTaxAuthorityandStateandLocalJurisdictionMemberMember" abstract="true" name="DomesticTaxAuthorityandStateandLocalJurisdictionMemberMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types1:domainItemType"/>
  <xs:element id="mgnx_TaxYear2027To2028Member" abstract="true" name="TaxYear2027To2028Member" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types1:domainItemType"/>
  <xs:element id="mgnx_IndefiniteMember" abstract="true" name="IndefiniteMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types1:domainItemType"/>
  <xs:element id="mgnx_TaxYear2027To2044Member" abstract="true" name="TaxYear2027To2044Member" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="mgnx_DeferredTaxAssetsOperatingLossCarryforwardsSubjectToExpirationAmountUtilizableOnAnnualBasis" abstract="false" name="DeferredTaxAssetsOperatingLossCarryforwardsSubjectToExpirationAmountUtilizableOnAnnualBasis" nillable="true" xbrli:periodType="instant" xbrli:balance="debit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="mgnx_DeferredTaxAssetsOperatingLeaseLiabilities" abstract="false" name="DeferredTaxAssetsOperatingLeaseLiabilities" nillable="true" xbrli:periodType="instant" xbrli:balance="debit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="mgnx_Section174DeferredTaxAsset" abstract="false" name="Section174DeferredTaxAsset" nillable="true" xbrli:periodType="instant" xbrli:balance="debit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="mgnx_DeferredTaxLiabilitiesOperatingLeaseRightOfUseAssets" abstract="false" name="DeferredTaxLiabilitiesOperatingLeaseRightOfUseAssets" nillable="true" xbrli:periodType="instant" xbrli:balance="credit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="mgnx_ValuationAllowanceRollForward" abstract="true" name="ValuationAllowanceRollForward" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="xbrli:stringItemType"/>
  <xs:element id="mgnx_ValuationAllowanceDeferredTaxAssetIncreaseAmount" abstract="false" name="ValuationAllowanceDeferredTaxAssetIncreaseAmount" nillable="true" xbrli:periodType="duration" xbrli:balance="credit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="mgnx_ValuationAllowanceDeferredTaxAssetDecreaseAmount" abstract="false" name="ValuationAllowanceDeferredTaxAssetDecreaseAmount" nillable="true" xbrli:periodType="duration" xbrli:balance="debit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <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_EffectiveIncomeTaxRateReconciliationDeferredStateBlendedRateAdjustmentsAmount" abstract="false" name="EffectiveIncomeTaxRateReconciliationDeferredStateBlendedRateAdjustmentsAmount" nillable="true" xbrli:periodType="duration" xbrli:balance="debit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="mgnx_EffectiveIncomeTaxRateReconciliationTaxCreditOrphanDrugAmount" abstract="false" name="EffectiveIncomeTaxRateReconciliationTaxCreditOrphanDrugAmount" nillable="true" xbrli:periodType="duration" xbrli:balance="credit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="mgnx_UnrecognizedTaxBenefitsIncreaseDecreaseResultingFromPriorPeriodTaxPositions" abstract="false" name="UnrecognizedTaxBenefitsIncreaseDecreaseResultingFromPriorPeriodTaxPositions" nillable="true" xbrli:periodType="duration" xbrli:balance="debit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="mgnx_EmployeesEligibleAgeToParticipateInBenefitPlan" abstract="false" name="EmployeesEligibleAgeToParticipateInBenefitPlan" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="xbrli:durationItemType"/>
  <xs:element id="mgnx_DefinedContributionPlanEmployeesContributionVestedPercentage" abstract="false" name="DefinedContributionPlanEmployeesContributionVestedPercentage" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types1:percentItemType"/>
  <xs:element id="mgnx_MainSegmentMember" abstract="true" name="MainSegmentMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="mgnx_VobramitanmabDuocarmazineMember" abstract="true" name="VobramitanmabDuocarmazineMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="mgnx_LorigerlimabMember" abstract="true" name="LorigerlimabMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="mgnx_MGC028Member" abstract="true" name="MGC028Member" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="mgnx_ADCMember" abstract="true" name="ADCMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="mgnx_MGC026Member" abstract="true" name="MGC026Member" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="mgnx_MargetuximabMember" abstract="true" name="MargetuximabMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="mgnx_MGD024Member" abstract="true" name="MGD024Member" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="mgnx_NextGenerationTCellEngagersMember" abstract="true" name="NextGenerationTCellEngagersMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="mgnx_RetifanlimabMember" abstract="true" name="RetifanlimabMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="mgnx_EnoblituzumabMember" abstract="true" name="EnoblituzumabMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="mgnx_OtherProgramsMember" abstract="true" name="OtherProgramsMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="mgnx_JamesKarrelsMember" abstract="true" name="JamesKarrelsMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="mgnx_JeffreyPetersMember" abstract="true" name="JeffreyPetersMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
</xs:schema>
