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  <xs:element id="mgnx_NoncashRoyaltyRevenuePayable" abstract="false" name="NoncashRoyaltyRevenuePayable" nillable="true" xbrli:periodType="duration" xbrli:balance="credit" 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-types:domainItemType"/>
  <xs:element id="mgnx_TaxYear2027To2028Member" abstract="true" name="TaxYear2027To2028Member" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="mgnx_IndefiniteMember" abstract="true" name="IndefiniteMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types: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_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_EffectiveIncomeTaxRateReconciliationNondeductibleExpenseOfficerCompensationAmount" abstract="false" name="EffectiveIncomeTaxRateReconciliationNondeductibleExpenseOfficerCompensationAmount" nillable="true" xbrli:periodType="duration" xbrli:balance="debit" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType"/>
  <xs:element id="mgnx_EffectiveIncomeTaxRateReconciliationTaxCreditOrphanDrugPercent" abstract="false" name="EffectiveIncomeTaxRateReconciliationTaxCreditOrphanDrugPercent" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:percentItemType"/>
  <xs:element id="mgnx_EffectiveIncomeTaxRateReconciliationNondeductibleExpenseOfficerCompensationPercent" abstract="false" name="EffectiveIncomeTaxRateReconciliationNondeductibleExpenseOfficerCompensationPercent" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:percentItemType"/>
  <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"/>
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  <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_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-types: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_LorigerlimabMember" abstract="true" name="LorigerlimabMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
  <xs:element id="mgnx_MGC030Member" abstract="true" name="MGC030Member" 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_VobramitanmabDuocarmazineMember" abstract="true" name="VobramitanmabDuocarmazineMember" 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_NextGenerationTCellEngagersMember" abstract="true" name="NextGenerationTCellEngagersMember" 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_ADCMember" abstract="true" name="ADCMember" 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_OtherProgramsMember" abstract="true" name="OtherProgramsMember" nillable="true" xbrli:periodType="duration" substitutionGroup="xbrli:item" type="dtr-types:domainItemType"/>
</xs:schema>
