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<!-- DFIN ActiveDisclosure(SM) XBRL Schema Document - http://www.dfinsolutions.com/ -->
<!-- Creation Date      : 2021-05-06T07:46:23.5232722+00:00 -->
<!-- Version            : 5.0.1.615 -->
<!-- Package ID         : 93f66a5c8aa64d5bb56459102bfb8cd8 -->
<!-- Copyright (c) 2021 Donnelley Financial Solutions, Inc. All Rights Reserved. -->
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  <xsd:element id="hrmy_CRGServicingLLCMember" name="CRGServicingLLCMember" type="nonnum:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true" />
  <xsd:element id="hrmy_CreditAgreementMember" name="CreditAgreementMember" type="nonnum:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true" />
  <xsd:element id="hrmy_DebtInstrumentVariableInterestRate" name="DebtInstrumentVariableInterestRate" type="num:percentItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false" />
  <xsd:element id="hrmy_ExtinguishmentOfDebtExitFees" name="ExtinguishmentOfDebtExitFees" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false" xbrli:balance="credit" />
  <xsd:element id="hrmy_DebtInstrumentExitFeePercentage" name="DebtInstrumentExitFeePercentage" type="num:percentItemType" substitutionGroup="xbrli:item" xbrli:periodType="instant" nillable="true" abstract="false" />
  <xsd:element id="hrmy_DebtInstrumentExitFees" name="DebtInstrumentExitFees" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="instant" nillable="true" abstract="false" xbrli:balance="debit" />
  <xsd:element id="hrmy_UnamortizedDebtDiscountAssociatedWithExitFeeDebtFinancingCostsAndDiscountWithWarrantFinancing" name="UnamortizedDebtDiscountAssociatedWithExitFeeDebtFinancingCostsAndDiscountWithWarrantFinancing" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="instant" nillable="true" abstract="false" xbrli:balance="debit" />
  <xsd:element id="hrmy_OrbiMedRoyaltyCreditOpportunitiesLPAndCRGServicingLLCMember" name="OrbiMedRoyaltyCreditOpportunitiesLPAndCRGServicingLLCMember" type="nonnum:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true" />
  <xsd:element id="hrmy_OperatingLeaseOfficeSpace" name="OperatingLeaseOfficeSpace" type="num:areaItemType" substitutionGroup="xbrli:item" xbrli:periodType="instant" nillable="true" abstract="false" />
  <xsd:element id="hrmy_OperatingLeaseExpirationMonthAndYear" name="OperatingLeaseExpirationMonthAndYear" type="xbrli:gYearMonthItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false" />
  <xsd:element id="hrmy_NorthbrookILMember" name="NorthbrookILMember" type="nonnum:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true" />
  <xsd:element id="hrmy_PlymouthMeetingPAMember" name="PlymouthMeetingPAMember" type="nonnum:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true" />
  <xsd:element id="hrmy_PreferredStockConversionRatio" name="PreferredStockConversionRatio" type="xbrli:pureItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false" />
  <xsd:element id="hrmy_UnderwritingDiscountsAndCommissionsAndOfferingExpenses" name="UnderwritingDiscountsAndCommissionsAndOfferingExpenses" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false" xbrli:balance="debit" />
  <xsd:element id="hrmy_TwoThousandSeventeenEquityIncentivePlanMember" name="TwoThousandSeventeenEquityIncentivePlanMember" type="nonnum:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true" />
  <xsd:element id="hrmy_IncentiveAwardPlanTwoThousandTwentyMember" name="IncentiveAwardPlanTwoThousandTwentyMember" type="nonnum:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true" />
  <xsd:element id="hrmy_TwoThousandSeventeenEquityIncentivePlanAndTwoThousandTwentyIncentiveAwardPlanMember" name="TwoThousandSeventeenEquityIncentivePlanAndTwoThousandTwentyIncentiveAwardPlanMember" type="nonnum:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true" />
  <xsd:element id="hrmy_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsExercisedInPeriod" name="ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsExercisedInPeriod" type="xbrli:sharesItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false" />
  <xsd:element id="hrmy_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonVestedWeightedAverageExercisePrice" name="ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonVestedWeightedAverageExercisePrice" type="num:perShareItemType" substitutionGroup="xbrli:item" xbrli:periodType="instant" nillable="true" abstract="false" />
  <xsd:element id="hrmy_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonVestedWeightedAverageExercisePriceGrantsInPeriod" name="ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonVestedWeightedAverageExercisePriceGrantsInPeriod" type="num:perShareItemType" substitutionGroup="xbrli:item" xbrli:periodType="instant" nillable="true" abstract="false" />
  <xsd:element id="hrmy_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonVestedWeightedAverageExercisePriceExercisedInPeriod" name="ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonVestedWeightedAverageExercisePriceExercisedInPeriod" type="num:perShareItemType" substitutionGroup="xbrli:item" xbrli:periodType="instant" nillable="true" abstract="false" />
  <xsd:element id="hrmy_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonVestedWeightedAverageExercisePriceForfeitedInPeriod" name="ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonVestedWeightedAverageExercisePriceForfeitedInPeriod" type="num:perShareItemType" substitutionGroup="xbrli:item" xbrli:periodType="instant" nillable="true" abstract="false" />
  <xsd:element id="hrmy_StockVestedDuringPeriodShares" name="StockVestedDuringPeriodShares" type="xbrli:sharesItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false" />
  <xsd:element id="hrmy_ShareBasedCompensationExpenseIncome" name="ShareBasedCompensationExpenseIncome" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false" xbrli:balance="debit" />
  <xsd:element id="hrmy_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsLackOfMarketabilityDiscount" name="ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsLackOfMarketabilityDiscount" type="num:percentItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false" />
  <xsd:element id="hrmy_FutureShareBasedCompensationExpensesRemainderOfFiscalYear" name="FutureShareBasedCompensationExpensesRemainderOfFiscalYear" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="instant" nillable="true" abstract="false" xbrli:balance="debit" />
  <xsd:element id="hrmy_FutureShareBasedCompensationExpenseYearOne" name="FutureShareBasedCompensationExpenseYearOne" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="instant" nillable="true" abstract="false" xbrli:balance="debit" />
  <xsd:element id="hrmy_FutureShareBasedCompensationExpenseYearTwo" name="FutureShareBasedCompensationExpenseYearTwo" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="instant" nillable="true" abstract="false" xbrli:balance="debit" />
  <xsd:element id="hrmy_FutureShareBasedCompensationExpenseYearThree" name="FutureShareBasedCompensationExpenseYearThree" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="instant" nillable="true" abstract="false" xbrli:balance="debit" />
  <xsd:element id="hrmy_FutureShareBasedCompensationExpenseYearFour" name="FutureShareBasedCompensationExpenseYearFour" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="instant" nillable="true" abstract="false" xbrli:balance="debit" />
  <xsd:element id="hrmy_SecuritiesOutstandingIncludedInComputationOfTreasuryStock" name="SecuritiesOutstandingIncludedInComputationOfTreasuryStock" type="xbrli:sharesItemType" substitutionGroup="xbrli:item" xbrli:periodType="instant" nillable="true" abstract="false" />
  <xsd:element id="hrmy_StockOptionAndStockStockAppreciationAndRestrictedStockUnitsMember" name="StockOptionAndStockStockAppreciationAndRestrictedStockUnitsMember" type="nonnum:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true" />
  <xsd:element id="hrmy_EmployeeStockOptionStockAppreciationRightsAndRestrictedStockUnitsMember" name="EmployeeStockOptionStockAppreciationRightsAndRestrictedStockUnitsMember" type="nonnum:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true" />
  <xsd:element id="hrmy_ManagementServicesAgreementMember" name="ManagementServicesAgreementMember" type="nonnum:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true" />
</xsd:schema>
