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<!-- DFIN ActiveDisclosure(SM) XBRL Schema Document - http://www.dfinsolutions.com/ -->
<!-- Creation Date      : 2020-08-05T03:11:37.3322927+00:00 -->
<!-- Version            : 5.0.1.476 -->
<!-- Package ID         : b73534ccac2d4b4a8e48bfec71a610e7 -->
<!-- Copyright (c) 2020 Donnelley Financial Solutions, Inc. All Rights Reserved. -->
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  <xsd:element id="asmb_NumberOfMilestones" name="NumberOfMilestones" type="xbrli:integerItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false" />
  <xsd:element id="asmb_AgreedToShareMaximumAmountDevelopmentCost" name="AgreedToShareMaximumAmountDevelopmentCost" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false" xbrli:balance="debit" />
  <xsd:element id="asmb_PremiumPercentageOnAgreedContributionDevelopmentCostAmount" name="PremiumPercentageOnAgreedContributionDevelopmentCostAmount" type="num:percentItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false" />
  <xsd:element id="asmb_RevenueRemainingPerformanceObligationOnEach" name="RevenueRemainingPerformanceObligationOnEach" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="instant" nillable="true" abstract="false" xbrli:balance="credit" />
  <xsd:element id="asmb_ContractWithCustomerLiabilityInAdditions" name="ContractWithCustomerLiabilityInAdditions" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false" xbrli:balance="credit" />
  <xsd:element id="asmb_ContractWithCustomerLiabilityInDeduction" name="ContractWithCustomerLiabilityInDeduction" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false" xbrli:balance="debit" />
  <xsd:element id="asmb_CollaborationRevenueRecognizedInPeriodAbstract" name="CollaborationRevenueRecognizedInPeriodAbstract" type="xbrli:stringItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true" />
  <xsd:element id="asmb_UpfrontCashPaymentReceived" name="UpfrontCashPaymentReceived" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false" xbrli:balance="debit" />
  <xsd:element id="asmb_AgreedToPayMaximumAmountDevelopmentAndRegulatoryCosts" name="AgreedToPayMaximumAmountDevelopmentAndRegulatoryCosts" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false" xbrli:balance="debit" />
  <xsd:element id="asmb_ChinaCollaborationAgreementMember" name="ChinaCollaborationAgreementMember" type="nonnum:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true" />
  <xsd:element id="asmb_DevelopmentAndRegulatoryMember" name="DevelopmentAndRegulatoryMember" type="nonnum:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true" />
  <xsd:element id="asmb_NetSalesMilestonePaymentsMember" name="NetSalesMilestonePaymentsMember" type="nonnum:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true" />
  <xsd:element id="asmb_BeiGeneLimitedMember" name="BeiGeneLimitedMember" type="nonnum:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true" />
</xsd:schema>
