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  <xsd:element id="mbio_CommonUnspecifiedClassMember" name="CommonUnspecifiedClassMember" nillable="true" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" abstract="true" xbrli:periodType="duration" />
  <xsd:element id="mbio_IncreaseDecreaseInAccountsPayableAndAccruedExpensesExcludingAmountsDueToRelatedParties" name="IncreaseDecreaseInAccountsPayableAndAccruedExpensesExcludingAmountsDueToRelatedParties" nillable="true" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" xbrli:balance="debit" />
  <xsd:element id="mbio_ClassOfWarrantOrRightWeightedAverageRemainingContractualLife" name="ClassOfWarrantOrRightWeightedAverageRemainingContractualLife" nillable="true" type="xbrli:durationItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" />
  <xsd:element id="mbio_AtMarketOfferingMember" name="AtMarketOfferingMember" nillable="true" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" abstract="true" xbrli:periodType="duration" />
  <xsd:element id="mbio_AccruedCompensationCurrent" name="AccruedCompensationCurrent" nillable="true" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="instant" xbrli:balance="credit" />
  <xsd:element id="mbio_ResearchAndDevelopmentCurrent" name="ResearchAndDevelopmentCurrent" nillable="true" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="instant" xbrli:balance="credit" />
  <xsd:element id="mbio_EmployeeStockPurchasePlanPredeterminedOfferingPeriodLowerFairMarketValuePercentage" name="EmployeeStockPurchasePlanPredeterminedOfferingPeriodLowerFairMarketValuePercentage" nillable="true" type="dtr-types:percentItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" />
  <xsd:element id="mbio_PercentageOfAnnualFeesExpensesRelatedToManagementServicesAgreementRecordedInResearchAndDevelopmentExpenses" name="PercentageOfAnnualFeesExpensesRelatedToManagementServicesAgreementRecordedInResearchAndDevelopmentExpenses" nillable="true" type="dtr-types:percentItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" />
  <xsd:element id="mbio_PercentageOfAnnualFeesExpenseRelatedToManagementServicesAgreementRecordedInGeneralAndAdministrativeExpenses" name="PercentageOfAnnualFeesExpenseRelatedToManagementServicesAgreementRecordedInGeneralAndAdministrativeExpenses" nillable="true" type="dtr-types:percentItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" />
  <xsd:element id="mbio_RegistrationStatementsMember" name="RegistrationStatementsMember" nillable="true" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" abstract="true" xbrli:periodType="duration" />
  <xsd:element id="mbio_SummaryOfWarrantActivitiesTableTextBlock" name="SummaryOfWarrantActivitiesTableTextBlock" nillable="true" type="dtr-types:textBlockItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" />
  <xsd:element id="mbio_SaleOfStockAggregateOfferingPricePermittedByAgreement" name="SaleOfStockAggregateOfferingPricePermittedByAgreement" nillable="true" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="instant" xbrli:balance="credit" />
  <xsd:element id="mbio_CommonStockSharesAvailableForFutureIssuanceValue" name="CommonStockSharesAvailableForFutureIssuanceValue" nillable="true" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="instant" xbrli:balance="credit" />
  <xsd:element name="AdditionsReductionsToAdditionalPaidInCapitalReverseStockSplits" id="mbio_AdditionsReductionsToAdditionalPaidInCapitalReverseStockSplits" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" nillable="true" xbrli:periodType="duration" abstract="false" xbrli:balance="credit" />
  <xsd:element name="GainOnLeaseModification" id="mbio_GainOnLeaseModification" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" nillable="true" xbrli:periodType="duration" abstract="false" xbrli:balance="credit" />
  <xsd:element name="ManagementServicesAgreementMember" id="mbio_ManagementServicesAgreementMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" nillable="true" xbrli:periodType="duration" abstract="true" />
  <xsd:element name="SecondAmendedAndRestatedFoundersAgreementMember" id="mbio_SecondAmendedAndRestatedFoundersAgreementMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" nillable="true" xbrli:periodType="duration" abstract="true" />
  <xsd:element name="PrefundedWarrantsMember" id="mbio_PrefundedWarrantsMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" nillable="true" xbrli:periodType="duration" abstract="true" />
  <xsd:element name="PlacementAgentsWarrantsMember" id="mbio_PlacementAgentsWarrantsMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" nillable="true" xbrli:periodType="duration" abstract="true" />
  <xsd:element name="SeriesA3WarrantMember" id="mbio_SeriesA3WarrantMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" nillable="true" xbrli:periodType="duration" abstract="true" />
  <xsd:element name="ClassOfWarrantConverted" id="mbio_ClassOfWarrantConverted" type="xbrli:sharesItemType" substitutionGroup="xbrli:item" nillable="true" xbrli:periodType="instant" abstract="false" />
  <xsd:element name="RegistrationStatements2024S3Member" id="mbio_RegistrationStatements2024S3Member" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" nillable="true" xbrli:periodType="duration" abstract="true" />
  <xsd:element name="AssetPurchaseAgreementWithUbrigeneBiosciencesMember" id="mbio_AssetPurchaseAgreementWithUbrigeneBiosciencesMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" nillable="true" xbrli:periodType="duration" abstract="true" />
  <xsd:element name="AssetAcquisitionConsiderationTransferredUpfrontPayment" id="mbio_AssetAcquisitionConsiderationTransferredUpfrontPayment" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" nillable="true" xbrli:periodType="duration" abstract="false" xbrli:balance="credit" />
  <xsd:element name="AssetAcquisitionConsiderationTransferredDeferredPaymentDuePeriodFromClosingDate" id="mbio_AssetAcquisitionConsiderationTransferredDeferredPaymentDuePeriodFromClosingDate" type="xbrli:durationItemType" substitutionGroup="xbrli:item" nillable="true" xbrli:periodType="duration" abstract="false" />
  <xsd:element name="AssetAcquisitionConsiderationTransferredDeferredPaymentExtensionTerm" id="mbio_AssetAcquisitionConsiderationTransferredDeferredPaymentExtensionTerm" type="xbrli:durationItemType" substitutionGroup="xbrli:item" nillable="true" xbrli:periodType="duration" abstract="false" />
  <xsd:element name="AssetAcquisitionConsiderationTransferredDeferredPaymentInterestRateOnOutstandingLiability" id="mbio_AssetAcquisitionConsiderationTransferredDeferredPaymentInterestRateOnOutstandingLiability" type="dtr-types:percentItemType" substitutionGroup="xbrli:item" nillable="true" xbrli:periodType="duration" abstract="false" />
  <xsd:element name="AssetAcquisitionConsiderationTransferredSubsequentPayment" id="mbio_AssetAcquisitionConsiderationTransferredSubsequentPayment" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" nillable="true" xbrli:periodType="duration" abstract="false" xbrli:balance="credit" />
  <xsd:element name="NetAssetsThresholdToDelayConsiderationPaymentObligation" id="mbio_NetAssetsThresholdToDelayConsiderationPaymentObligation" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" nillable="true" xbrli:periodType="instant" abstract="false" xbrli:balance="debit" />
  <xsd:element name="CashFeeAsPercentageOfAggregateGrossProceeds" id="mbio_CashFeeAsPercentageOfAggregateGrossProceeds" type="dtr-types:percentItemType" substitutionGroup="xbrli:item" nillable="true" xbrli:periodType="duration" abstract="false" />
  <xsd:element name="ManagementFeeAsPercentageOfGrossProceeds" id="mbio_ManagementFeeAsPercentageOfGrossProceeds" type="dtr-types:percentItemType" substitutionGroup="xbrli:item" nillable="true" xbrli:periodType="duration" abstract="false" />
  <xsd:element name="IssuanceOfCommonSharesEquityFeeOnEquityOffering" id="mbio_IssuanceOfCommonSharesEquityFeeOnEquityOffering" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" nillable="true" xbrli:periodType="duration" abstract="false" xbrli:balance="debit" />
  <xsd:element name="StockIssuedDuringPeriodValueEquityOffering" id="mbio_StockIssuedDuringPeriodValueEquityOffering" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" nillable="true" xbrli:periodType="duration" abstract="false" xbrli:balance="credit" />
  <xsd:element name="StockIssuedDuringPeriodSharesEquityOffering" id="mbio_StockIssuedDuringPeriodSharesEquityOffering" type="xbrli:sharesItemType" substitutionGroup="xbrli:item" nillable="true" xbrli:periodType="duration" abstract="false" />
  <xsd:element name="AbeyanceSharesReleased" id="mbio_AbeyanceSharesReleased" type="xbrli:sharesItemType" substitutionGroup="xbrli:item" nillable="true" xbrli:periodType="duration" abstract="false" />
  <xsd:element name="NumberOfSharesReverseStockSplit" id="mbio_NumberOfSharesReverseStockSplit" type="xbrli:sharesItemType" substitutionGroup="xbrli:item" nillable="true" xbrli:periodType="duration" abstract="false" />
  <xsd:element name="February2025PublicOfferingMember" id="mbio_February2025PublicOfferingMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" nillable="true" xbrli:periodType="duration" abstract="true" />
  <xsd:element name="SeriesC2WarrantMember" id="mbio_SeriesC2WarrantMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" nillable="true" xbrli:periodType="duration" abstract="true" />
  <xsd:element name="SeriesC1WarrantMember" id="mbio_SeriesC1WarrantMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" nillable="true" xbrli:periodType="duration" abstract="true" />
  <xsd:element name="FeesAndOtherRelatedExpenses" id="mbio_FeesAndOtherRelatedExpenses" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" nillable="true" xbrli:periodType="duration" abstract="false" xbrli:balance="debit" />
  <xsd:element name="NonAccountableExpenseAllowance" id="mbio_NonAccountableExpenseAllowance" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" nillable="true" xbrli:periodType="duration" abstract="false" xbrli:balance="debit" />
  <xsd:element name="RoadShowExpenses" id="mbio_RoadShowExpenses" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" nillable="true" xbrli:periodType="duration" abstract="false" xbrli:balance="debit" />
  <xsd:element name="ClearingExpenses" id="mbio_ClearingExpenses" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" nillable="true" xbrli:periodType="duration" abstract="false" xbrli:balance="debit" />
  <xsd:element name="CombinedOfferingPricePercentage" id="mbio_CombinedOfferingPricePercentage" type="dtr-types:percentItemType" substitutionGroup="xbrli:item" nillable="true" xbrli:periodType="instant" abstract="false" />
  <xsd:element name="ClassOfWarrantOrRightExpiryTerm" id="mbio_ClassOfWarrantOrRightExpiryTerm" type="xbrli:durationItemType" substitutionGroup="xbrli:item" nillable="true" xbrli:periodType="duration" abstract="false" />
  <xsd:element name="PrefundedWarrantAndShareSoldInOfferingPercentage" id="mbio_PrefundedWarrantAndShareSoldInOfferingPercentage" type="dtr-types:percentItemType" substitutionGroup="xbrli:item" nillable="true" xbrli:periodType="instant" abstract="false" />
  <xsd:element name="ConvertibleStockNumberOfSharesUponConversion" id="mbio_ConvertibleStockNumberOfSharesUponConversion" type="xbrli:sharesItemType" substitutionGroup="xbrli:item" nillable="true" xbrli:periodType="instant" abstract="false" />
  <xsd:element name="ProceedsFromIssuanceOfCommonStockNetOfIssuanceCostsAtEquityOffering" id="mbio_ProceedsFromIssuanceOfCommonStockNetOfIssuanceCostsAtEquityOffering" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" nillable="true" xbrli:periodType="duration" abstract="false" xbrli:balance="debit" />
  <xsd:element name="ResearchAndDevelopmentExpenseExcludingAcquiredInProcessCostNet" id="mbio_ResearchAndDevelopmentExpenseExcludingAcquiredInProcessCostNet" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" nillable="true" xbrli:periodType="duration" abstract="false" xbrli:balance="debit" />
  <xsd:element name="UnpaidOfferingCostsForIssuanceOfEquityOffering" id="mbio_UnpaidOfferingCostsForIssuanceOfEquityOffering" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" nillable="true" xbrli:periodType="duration" abstract="false" xbrli:balance="credit" />
  <xsd:element name="NoncashSettlementOfPayables" id="mbio_NoncashSettlementOfPayables" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" nillable="true" xbrli:periodType="duration" abstract="false" xbrli:balance="credit" />
  <xsd:element name="EquityIncentivePlanMember" id="mbio_EquityIncentivePlanMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" nillable="true" xbrli:periodType="duration" abstract="true" />
  <xsd:element name="WarrantExercisePriceExpiredDuringPeriod" id="mbio_WarrantExercisePriceExpiredDuringPeriod" type="xbrli:sharesItemType" substitutionGroup="xbrli:item" nillable="true" xbrli:periodType="duration" abstract="false" />
  <xsd:element name="NewYorkCityMember" id="mbio_NewYorkCityMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" nillable="true" xbrli:periodType="duration" abstract="true" />
  <xsd:element name="IncomeTaxEffectChangeInLawAxis" id="mbio_IncomeTaxEffectChangeInLawAxis" type="xbrli:stringItemType" substitutionGroup="xbrldt:dimensionItem" nillable="true" xbrli:periodType="duration" abstract="true" />
  <xsd:element name="IncomeTaxEffectChangeInLawDomain" id="mbio_IncomeTaxEffectChangeInLawDomain" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" nillable="true" xbrli:periodType="duration" abstract="true" />
  <xsd:element name="AssetAcquisitionAccruedInterestOnDeferredPurchaseConsideration" id="mbio_AssetAcquisitionAccruedInterestOnDeferredPurchaseConsideration" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" nillable="true" xbrli:periodType="instant" abstract="false" xbrli:balance="credit" />
  <xsd:element name="AccountsPayableAndAccruedExpensesTable" id="mbio_AccountsPayableAndAccruedExpensesTable" type="xbrli:stringItemType" substitutionGroup="xbrldt:hypercubeItem" nillable="true" xbrli:periodType="duration" abstract="true" />
  <xsd:element name="AccountsPayableAndAccruedExpensesLineItems" id="mbio_AccountsPayableAndAccruedExpensesLineItems" type="xbrli:stringItemType" substitutionGroup="xbrli:item" nillable="true" xbrli:periodType="duration" abstract="true" />
  <xsd:element name="ClassOfWarrantOrRightWarrantsExercisedAndExpiredDuringPeriod" id="mbio_ClassOfWarrantOrRightWarrantsExercisedAndExpiredDuringPeriod" type="xbrli:sharesItemType" substitutionGroup="xbrli:item" nillable="true" xbrli:periodType="duration" abstract="false" />
  <xsd:element name="RentExpense" id="mbio_RentExpense" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" nillable="true" xbrli:periodType="duration" abstract="false" xbrli:balance="debit" />
</xsd:schema>
