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  <xsd:element name="CollaborationAgreementAssetsAndLiabilitiesAbstract" id="mack_CollaborationAgreementAssetsAndLiabilitiesAbstract" type="xbrli:stringItemType" substitutionGroup="xbrli:item" abstract="true" nillable="true" xbrli:periodType="duration" />
  <xsd:element name="CollaborativeArrangementAbstract" id="mack_CollaborativeArrangementAbstract" type="xbrli:stringItemType" substitutionGroup="xbrli:item" abstract="true" nillable="true" xbrli:periodType="duration" />
  <xsd:element name="CollaborativeArrangementMilestonePaymentsReceived" id="mack_CollaborativeArrangementMilestonePaymentsReceived" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" nillable="true" xbrli:balance="debit" xbrli:periodType="duration" />
  <xsd:element name="OperatingLeaseAmendmentAdditionalSpaceLeaseTerm" id="mack_OperatingLeaseAmendmentAdditionalSpaceLeaseTerm" type="xbrli:durationItemType" substitutionGroup="xbrli:item" nillable="true" xbrli:periodType="duration" />
  <xsd:element name="CollaborativeArrangementExpectedDevelopmentPeriod" id="mack_CollaborativeArrangementExpectedDevelopmentPeriod" type="xbrli:durationItemType" substitutionGroup="xbrli:item" nillable="true" xbrli:periodType="duration" />
  <xsd:element name="OperatingLeasesMaximumReimbursementForTenantImprovements" id="mack_OperatingLeasesMaximumReimbursementForTenantImprovements" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" nillable="true" xbrli:balance="debit" xbrli:periodType="duration" />
  <xsd:element name="OperatingLeasesReimbursementsReceivableForTenantImprovements" id="mack_OperatingLeasesReimbursementsReceivableForTenantImprovements" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" nillable="true" xbrli:balance="debit" xbrli:periodType="instant" />
  <xsd:element name="CollaborativeArrangementsReimbursementOfPreviouslyBilledAmount" id="mack_CollaborativeArrangementsReimbursementOfPreviouslyBilledAmount" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" nillable="true" xbrli:balance="credit" xbrli:periodType="instant" />
  <xsd:element name="CollaborativeArrangementsPreviouslyBilledAmountReimbursed" id="mack_CollaborativeArrangementsPreviouslyBilledAmountReimbursed" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" nillable="true" xbrli:balance="debit" xbrli:periodType="duration" />
  <xsd:element name="CollaborativeArrangementReductionInEarningsDueToReimbursementOfPreviouslyBilledAmount" id="mack_CollaborativeArrangementReductionInEarningsDueToReimbursementOfPreviouslyBilledAmount" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" nillable="true" xbrli:balance="debit" xbrli:periodType="duration" />
  <xsd:element name="OtherNonoperatingIncomeExpensePolicyTextBlock" id="mack_OtherNonoperatingIncomeExpensePolicyTextBlock" type="nonnum:textBlockItemType" substitutionGroup="xbrli:item" nillable="true" xbrli:periodType="duration" />
  <xsd:element name="SilverCreekPharmaceuticalsIncMember" id="mack_SilverCreekPharmaceuticalsIncMember" type="nonnum:domainItemType" substitutionGroup="xbrli:item" abstract="true" nillable="true" xbrli:periodType="duration" />
  <xsd:element name="AvailableForSaleSecuritiesDebtMaturitiesRollingYearOneThroughTwoYearsAmortizedCost" id="mack_AvailableForSaleSecuritiesDebtMaturitiesRollingYearOneThroughTwoYearsAmortizedCost" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" nillable="true" xbrli:balance="debit" xbrli:periodType="instant" />
  <xsd:element name="AvailableForSaleSecuritiesDebtMaturitiesRollingYearTwoThroughThreeYearsAmortizedCost" id="mack_AvailableForSaleSecuritiesDebtMaturitiesRollingYearTwoThroughThreeYearsAmortizedCost" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" nillable="true" xbrli:balance="debit" xbrli:periodType="instant" />
  <xsd:element name="AvailableForSaleSecuritiesDebtMaturitiesNextRollingTwelveMonthsGrossUnrealizedLosses" id="mack_AvailableForSaleSecuritiesDebtMaturitiesNextRollingTwelveMonthsGrossUnrealizedLosses" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" nillable="true" xbrli:balance="credit" xbrli:periodType="instant" />
  <xsd:element name="AvailableForSaleSecuritiesDebtMaturitiesNextRollingTwelveMonthsGrossUnrealizedGain" id="mack_AvailableForSaleSecuritiesDebtMaturitiesNextRollingTwelveMonthsGrossUnrealizedGain" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" nillable="true" xbrli:balance="debit" xbrli:periodType="instant" />
  <xsd:element name="AvailableForSaleSecuritiesDebtMaturitiesAfterRollingYearOneThroughTwoYearsGrossUnrealizedGain" id="mack_AvailableForSaleSecuritiesDebtMaturitiesAfterRollingYearOneThroughTwoYearsGrossUnrealizedGain" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" nillable="true" xbrli:balance="debit" xbrli:periodType="instant" />
  <xsd:element name="AvailableForSaleSecuritiesDebtMaturitiesRollingYearTwoThroughThreeYearsGrossUnrealizedGain" id="mack_AvailableForSaleSecuritiesDebtMaturitiesRollingYearTwoThroughThreeYearsGrossUnrealizedGain" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" nillable="true" xbrli:balance="debit" xbrli:periodType="instant" />
  <xsd:element name="AvailableForSaleSecuritiesDebtMaturitiesAfterRollingYearOneThroughTwoYearsGrossUnrealizedLosses" id="mack_AvailableForSaleSecuritiesDebtMaturitiesAfterRollingYearOneThroughTwoYearsGrossUnrealizedLosses" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" nillable="true" xbrli:balance="credit" xbrli:periodType="instant" />
  <xsd:element name="AvailableForSaleSecuritiesDebtMaturitiesRollingYearTwoThroughThreeYearsGrossUnrealizedLosses" id="mack_AvailableForSaleSecuritiesDebtMaturitiesRollingYearTwoThroughThreeYearsGrossUnrealizedLosses" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" nillable="true" xbrli:balance="credit" xbrli:periodType="instant" />
  <xsd:element name="AvailableForSaleSecuritiesDebtMaturitiesAfterRollingYearOneThroughTwoYearsFairValue" id="mack_AvailableForSaleSecuritiesDebtMaturitiesAfterRollingYearOneThroughTwoYearsFairValue" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" nillable="true" xbrli:balance="debit" xbrli:periodType="instant" />
  <xsd:element name="AvailableForSaleSecuritiesDebtMaturitiesAfterRollingYearTwoThroughThreeYearsFairValue" id="mack_AvailableForSaleSecuritiesDebtMaturitiesAfterRollingYearTwoThroughThreeYearsFairValue" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" nillable="true" xbrli:balance="debit" xbrli:periodType="instant" />
  <xsd:element name="AvailableForSaleSecuritiesDebtMaturitiesGrossUnrealizedGainAbstract" id="mack_AvailableForSaleSecuritiesDebtMaturitiesGrossUnrealizedGainAbstract" type="xbrli:stringItemType" substitutionGroup="xbrli:item" abstract="true" nillable="true" xbrli:periodType="duration" />
  <xsd:element name="AvailableForSaleSecuritiesDebtMaturitiesGrossUnrealizedLossesAbstract" id="mack_AvailableForSaleSecuritiesDebtMaturitiesGrossUnrealizedLossesAbstract" type="xbrli:stringItemType" substitutionGroup="xbrli:item" abstract="true" nillable="true" xbrli:periodType="duration" />
  <xsd:element name="AvailableForSaleSecuritiesContinuousUnrealizedLossPositionAfterOneThroughTwoYearsFairValue" id="mack_AvailableForSaleSecuritiesContinuousUnrealizedLossPositionAfterOneThroughTwoYearsFairValue" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" nillable="true" xbrli:balance="debit" xbrli:periodType="instant" />
  <xsd:element name="AvailableForSaleSecuritiesContinuousUnrealizedLossPositionAfterTwoThroughThreeYearsFairValue" id="mack_AvailableForSaleSecuritiesContinuousUnrealizedLossPositionAfterTwoThroughThreeYearsFairValue" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" nillable="true" xbrli:balance="debit" xbrli:periodType="instant" />
  <xsd:element name="AvailableForSaleSecuritiesContinuousUnrealizedLossPositionAfterOneThroughTwoYearsAggregateLosses" id="mack_AvailableForSaleSecuritiesContinuousUnrealizedLossPositionAfterOneThroughTwoYearsAggregateLosses" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" nillable="true" xbrli:balance="credit" xbrli:periodType="instant" />
  <xsd:element name="AvailableForSaleSecuritiesContinuousUnrealizedLossPositionAfterTwoThroughThreeYearAggregateLosses" id="mack_AvailableForSaleSecuritiesContinuousUnrealizedLossPositionAfterTwoThroughThreeYearAggregateLosses" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" nillable="true" xbrli:balance="credit" xbrli:periodType="instant" />
  <xsd:element name="NoncontrollingInterestEquityPreferredFairValue" id="mack_NoncontrollingInterestEquityPreferredFairValue" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" nillable="true" xbrli:balance="credit" xbrli:periodType="instant" />
  <xsd:element name="ProceedsFromIssuanceInitialPublicOfferingNetOfOfferingCosts" id="mack_ProceedsFromIssuanceInitialPublicOfferingNetOfOfferingCosts" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" nillable="true" xbrli:balance="debit" xbrli:periodType="duration" />
  <xsd:element name="ProceedsFromIssuanceInitialPublicOfferingNetOfOfferingCostsLessDeferredFinancingCostsReclassifiedToEquity" id="mack_ProceedsFromIssuanceInitialPublicOfferingNetOfOfferingCostsLessDeferredFinancingCostsReclassifiedToEquity" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" nillable="true" xbrli:balance="debit" xbrli:periodType="duration" />
  <xsd:element name="ScheduleOfEmployeeAndNonemployeeServiceShareBasedCompensationAllocationOfRecognizedPeriodCostsTextBlock" id="mack_ScheduleOfEmployeeAndNonemployeeServiceShareBasedCompensationAllocationOfRecognizedPeriodCostsTextBlock" type="nonnum:textBlockItemType" substitutionGroup="xbrli:item" nillable="true" xbrli:periodType="duration" />
  <xsd:element name="SaleOfStockTable" id="mack_SaleOfStockTable" type="xbrli:stringItemType" substitutionGroup="xbrldt:hypercubeItem" abstract="true" nillable="true" xbrli:periodType="duration" />
  <xsd:element name="SaleOfStockLineItems" id="mack_SaleOfStockLineItems" type="xbrli:stringItemType" substitutionGroup="xbrli:item" abstract="true" nillable="true" xbrli:periodType="duration" />
  <xsd:element name="AllocatedShareBasedCompensationExpenseIncludingNonEmployees" id="mack_AllocatedShareBasedCompensationExpenseIncludingNonEmployees" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" nillable="true" xbrli:balance="debit" xbrli:periodType="duration" />
  <xsd:element name="OperatingLeasesFutureMinimumPaymentsDueAmendment" id="mack_OperatingLeasesFutureMinimumPaymentsDueAmendment" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" nillable="true" xbrli:balance="credit" xbrli:periodType="instant" />
  <xsd:element name="PurchasedPremiumsAndInterestOnAvailableForSaleSecurities" id="mack_PurchasedPremiumsAndInterestOnAvailableForSaleSecurities" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" nillable="true" xbrli:balance="credit" xbrli:periodType="duration" />
  <xsd:element name="ConvertiblePreferredStockWarrantsSharesReservedForFutureIssuance" id="mack_ConvertiblePreferredStockWarrantsSharesReservedForFutureIssuance" type="xbrli:sharesItemType" substitutionGroup="xbrli:item" nillable="true" xbrli:periodType="instant" />
  <xsd:element name="CommonStockWarrantsSharesReservedForFutureIssuance" id="mack_CommonStockWarrantsSharesReservedForFutureIssuance" type="xbrli:sharesItemType" substitutionGroup="xbrli:item" nillable="true" xbrli:periodType="instant" />
  <xsd:element name="CommonStockDisclosureTextBlock" id="mack_CommonStockDisclosureTextBlock" type="nonnum:textBlockItemType" substitutionGroup="xbrli:item" nillable="true" xbrli:periodType="duration" />
  <xsd:element name="HermesBioSciencesIncMember" id="mack_HermesBioSciencesIncMember" type="nonnum:domainItemType" substitutionGroup="xbrli:item" abstract="true" nillable="true" xbrli:periodType="duration" />
  <xsd:element name="AntibodyTargetedNanotherapeuticMember" id="mack_AntibodyTargetedNanotherapeuticMember" type="nonnum:domainItemType" substitutionGroup="xbrli:item" abstract="true" nillable="true" xbrli:periodType="duration" />
  <xsd:element name="NanotherapeuticMember" id="mack_NanotherapeuticMember" type="nonnum:domainItemType" substitutionGroup="xbrli:item" abstract="true" nillable="true" xbrli:periodType="duration" />
  <xsd:element name="OtherProgramsMember" id="mack_OtherProgramsMember" type="nonnum:domainItemType" substitutionGroup="xbrli:item" abstract="true" nillable="true" xbrli:periodType="duration" />
  <xsd:element name="ResearchAndDevelopmentProgramAxis" id="mack_ResearchAndDevelopmentProgramAxis" type="xbrli:stringItemType" substitutionGroup="xbrldt:dimensionItem" abstract="true" nillable="true" xbrli:periodType="duration" />
  <xsd:element name="ResearchAndDevelopmentProgramDomain" id="mack_ResearchAndDevelopmentProgramDomain" type="nonnum:domainItemType" substitutionGroup="xbrli:item" abstract="true" nillable="true" xbrli:periodType="duration" />
  <xsd:element name="DebtInstrumentInitialAdvance" id="mack_DebtInstrumentInitialAdvance" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" abstract="false" nillable="true" xbrli:balance="credit" xbrli:periodType="instant" />
  <xsd:element name="DebtInstrumentAdditionalAdvance" id="mack_DebtInstrumentAdditionalAdvance" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" abstract="false" nillable="true" xbrli:balance="credit" xbrli:periodType="instant" />
  <xsd:element name="LifeSciencesTaxIncentiveProgram2011Member" id="mack_LifeSciencesTaxIncentiveProgram2011Member" type="nonnum:domainItemType" substitutionGroup="xbrli:item" abstract="true" nillable="true" xbrli:periodType="duration" />
  <xsd:element name="TaxIncentiveProgramLineItems" id="mack_TaxIncentiveProgramLineItems" type="xbrli:stringItemType" substitutionGroup="xbrli:item" abstract="true" nillable="true" xbrli:periodType="duration" />
  <xsd:element name="TaxIncentiveProgramTaxIncentiveAwarded" id="mack_TaxIncentiveProgramTaxIncentiveAwarded" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" abstract="false" nillable="true" xbrli:balance="credit" xbrli:periodType="duration" />
  <xsd:element name="TaxIncentiveProgramStateResearchAndDevelopmentTaxCreditsMonetized" id="mack_TaxIncentiveProgramStateResearchAndDevelopmentTaxCreditsMonetized" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" abstract="false" nillable="true" xbrli:balance="credit" xbrli:periodType="duration" />
  <xsd:element name="DebtInstrumentInterestRateAlternativeAxis" id="mack_DebtInstrumentInterestRateAlternativeAxis" type="xbrli:stringItemType" substitutionGroup="xbrldt:dimensionItem" abstract="true" nillable="true" xbrli:periodType="duration" />
  <xsd:element name="DebtInstrumentInterestRateAlternativeDomain" id="mack_DebtInstrumentInterestRateAlternativeDomain" type="nonnum:domainItemType" substitutionGroup="xbrli:item" abstract="true" nillable="true" xbrli:periodType="duration" />
  <xsd:element name="DebtInstrumentInterestRateAlternativeOneMember" id="mack_DebtInstrumentInterestRateAlternativeOneMember" type="nonnum:domainItemType" substitutionGroup="xbrli:item" abstract="true" nillable="true" xbrli:periodType="duration" />
  <xsd:element name="DebtInstrumentInterestRateAlternativeTwoMember" id="mack_DebtInstrumentInterestRateAlternativeTwoMember" type="nonnum:domainItemType" substitutionGroup="xbrli:item" abstract="true" nillable="true" xbrli:periodType="duration" />
  <xsd:element name="DebtInstrumentInterestRateStatedPercentageUsedAsBasisForCalculationOfAlternativeInterestRate" id="mack_DebtInstrumentInterestRateStatedPercentageUsedAsBasisForCalculationOfAlternativeInterestRate" type="num:percentItemType" substitutionGroup="xbrli:item" nillable="true" xbrli:periodType="instant" />
  <xsd:element name="DebtInstrumentDescriptionOfVariableRateBasisAddedToStatedPercentage" id="mack_DebtInstrumentDescriptionOfVariableRateBasisAddedToStatedPercentage" type="xbrli:stringItemType" substitutionGroup="xbrli:item" nillable="true" xbrli:periodType="duration" />
  <xsd:element name="DebtInstrumentBasisReductionOnVariableRate" id="mack_DebtInstrumentBasisReductionOnVariableRate" type="num:percentItemType" substitutionGroup="xbrli:item" nillable="true" xbrli:periodType="instant" />
  <xsd:element name="DebtInstrumentGrossProceedsInOneOrMoreTransactionsPriorToSpecifiedDate" id="mack_DebtInstrumentGrossProceedsInOneOrMoreTransactionsPriorToSpecifiedDate" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" abstract="false" nillable="true" xbrli:balance="debit" xbrli:periodType="duration" />
  <xsd:element name="DebtInstrumentInterestOnlyPaymentPeriodExtension" id="mack_DebtInstrumentInterestOnlyPaymentPeriodExtension" type="xbrli:durationItemType" substitutionGroup="xbrli:item" abstract="false" nillable="true" xbrli:periodType="duration" />
</xsd:schema>
