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  <xsd:element id="selb_IncreaseDecreaseInContingentlyRepayableGrantFunding" name="IncreaseDecreaseInContingentlyRepayableGrantFunding" nillable="true" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType" xbrli:balance="debit" xbrli:periodType="duration" />
  <xsd:element id="selb_LaboratoryAndOfficeSpaceMember" name="LaboratoryAndOfficeSpaceMember" nillable="true" substitutionGroup="xbrli:item" type="nonnum:domainItemType" xbrli:periodType="duration" />
  <xsd:element id="selb_LaboratoryEquipmentMember" name="LaboratoryEquipmentMember" nillable="true" substitutionGroup="xbrli:item" type="nonnum:domainItemType" xbrli:periodType="duration" />
  <xsd:element abstract="true" id="selb_LeaseArrangementAxis" name="LeaseArrangementAxis" nillable="true" substitutionGroup="xbrldt:dimensionItem" type="xbrli:stringItemType" xbrli:periodType="duration" />
  <xsd:element abstract="true" id="selb_LeaseArrangementDomain" name="LeaseArrangementDomain" nillable="true" substitutionGroup="xbrli:item" type="nonnum:domainItemType" xbrli:periodType="duration" />
  <xsd:element abstract="true" id="selb_LicenseAgreementForPompeDiseaseMember" name="LicenseAgreementForPompeDiseaseMember" nillable="true" substitutionGroup="xbrli:item" type="nonnum:domainItemType" xbrli:periodType="duration" />
  <xsd:element id="selb_LicenseAgreementWithShenyangSunshinePharmaceuticalCompanyLimitedMember" name="LicenseAgreementWithShenyangSunshinePharmaceuticalCompanyLimitedMember" nillable="true" substitutionGroup="xbrli:item" type="nonnum:domainItemType" xbrli:periodType="duration" />
  <xsd:element id="selb_LicenseAndOptionAgreementAdditionalDevelopmentAndRegulatoryMilestonePaymentsThatMayBeReceived" name="LicenseAndOptionAgreementAdditionalDevelopmentAndRegulatoryMilestonePaymentsThatMayBeReceived" nillable="true" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType" xbrli:balance="debit" xbrli:periodType="duration" />
  <xsd:element id="selb_LicenseAndOptionAgreementAdditionalSubLicensePaymentReceivedLiability" name="LicenseAndOptionAgreementAdditionalSubLicensePaymentReceivedLiability" nillable="true" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType" xbrli:balance="credit" xbrli:periodType="duration" />
  <xsd:element id="selb_LicenseAndOptionAgreementAggregateAdditionalPaymentsDueWithinTwelveMonthsOfContractDate" name="LicenseAndOptionAgreementAggregateAdditionalPaymentsDueWithinTwelveMonthsOfContractDate" nillable="true" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType" xbrli:balance="debit" xbrli:periodType="duration" />
  <xsd:element id="selb_LicenseAndOptionAgreementCalculatedPremiumPaidForEquityInvestmentUnderPurchaseAgreement" name="LicenseAndOptionAgreementCalculatedPremiumPaidForEquityInvestmentUnderPurchaseAgreement" nillable="true" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType" xbrli:balance="credit" xbrli:periodType="duration" />
  <xsd:element id="selb_LicenseAndOptionAgreementCommercializationMilestonePaymentsThatMayBeReceived" name="LicenseAndOptionAgreementCommercializationMilestonePaymentsThatMayBeReceived" nillable="true" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType" xbrli:balance="debit" xbrli:periodType="duration" />
  <xsd:element id="selb_LicenseAndOptionAgreementContractualPaymentsMade" name="LicenseAndOptionAgreementContractualPaymentsMade" nillable="true" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType" xbrli:balance="credit" xbrli:periodType="duration" />
  <xsd:element id="selb_LicenseAndOptionAgreementExecutionFeePayment" name="LicenseAndOptionAgreementExecutionFeePayment" nillable="true" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType" xbrli:balance="debit" xbrli:periodType="duration" />
  <xsd:element id="selb_LicenseAndOptionAgreementInitialUpFrontCashPayment" name="LicenseAndOptionAgreementInitialUpFrontCashPayment" nillable="true" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType" xbrli:balance="debit" xbrli:periodType="duration" />
  <xsd:element id="selb_LicenseAndOptionAgreementNumberOfAdditionalTargetsForWhichOtherPartyMayExerciseOptionsForAdditionalLicenses" name="LicenseAndOptionAgreementNumberOfAdditionalTargetsForWhichOtherPartyMayExerciseOptionsForAdditionalLicenses" nillable="true" substitutionGroup="xbrli:item" type="xbrli:integerItemType" xbrli:periodType="duration" />
  <xsd:element id="selb_LicenseAndOptionAgreementPeriodForOtherPartyToExerciseOptionsForAdditionalLicenses" name="LicenseAndOptionAgreementPeriodForOtherPartyToExerciseOptionsForAdditionalLicenses" nillable="true" substitutionGroup="xbrli:item" type="xbrli:durationItemType" xbrli:periodType="duration" />
  <xsd:element id="selb_LicenseAndOptionAgreementSalesMilestonePaymentsThatMayBeReceived" name="LicenseAndOptionAgreementSalesMilestonePaymentsThatMayBeReceived" nillable="true" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType" xbrli:balance="debit" xbrli:periodType="duration" />
  <xsd:element id="selb_LicenseAndOptionAgreementTwoPaymentsDueWithinTwelveMonthsOfContractDate" name="LicenseAndOptionAgreementTwoPaymentsDueWithinTwelveMonthsOfContractDate" nillable="true" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType" xbrli:balance="credit" xbrli:periodType="duration" />
  <xsd:element id="selb_LicenseAndOptionAgreementUpfrontCashPayment" name="LicenseAndOptionAgreementUpfrontCashPayment" nillable="true" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType" xbrli:balance="debit" xbrli:periodType="duration" />
  <xsd:element id="selb_LicenseAndOptionAgreementVariableFeeToBeReceivedForEachAdditionalTargetOptionElected" name="LicenseAndOptionAgreementVariableFeeToBeReceivedForEachAdditionalTargetOptionElected" nillable="true" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType" xbrli:balance="debit" xbrli:periodType="duration" />
  <xsd:element abstract="true" id="selb_LicenseAndSupplyObligationMember" name="LicenseAndSupplyObligationMember" nillable="true" substitutionGroup="xbrli:item" type="nonnum:domainItemType" xbrli:periodType="duration" />
  <xsd:element abstract="true" id="selb_NonEmployeeStockOptionMember" name="NonEmployeeStockOptionMember" nillable="true" substitutionGroup="xbrli:item" type="nonnum:domainItemType" xbrli:periodType="duration" />
  <xsd:element id="selb_NumberOfAgreementsCombinedIntoSingleAgreementForEvaluation" name="NumberOfAgreementsCombinedIntoSingleAgreementForEvaluation" nillable="true" substitutionGroup="xbrli:item" type="xbrli:integerItemType" xbrli:periodType="instant" />
  <xsd:element id="selb_NumberOfOfferingPeriods" name="NumberOfOfferingPeriods" nillable="true" substitutionGroup="xbrli:item" type="xbrli:integerItemType" xbrli:periodType="duration" />
  <xsd:element abstract="true" id="selb_OutstandingBalancesMember" name="OutstandingBalancesMember" nillable="true" substitutionGroup="xbrli:item" type="nonnum:domainItemType" xbrli:periodType="duration" />
  <xsd:element id="selb_OverspentCosts" name="OverspentCosts" nillable="true" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType" xbrli:balance="credit" xbrli:periodType="duration" />
  <xsd:element id="selb_PeriodForPriorWrittenNoticeToTerminateLicense" name="PeriodForPriorWrittenNoticeToTerminateLicense" nillable="true" substitutionGroup="xbrli:item" type="xbrli:durationItemType" xbrli:periodType="duration" />
  <xsd:element id="selb_PlantPropertyAndEquipmentAcceleratedDepreciation" name="PlantPropertyAndEquipmentAcceleratedDepreciation" nillable="true" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType" xbrli:balance="debit" xbrli:periodType="duration" />
  <xsd:element id="selb_PremiumOfAverageDailyVolumeWeightedAveragePriceOfCommonStockPercent" name="PremiumOfAverageDailyVolumeWeightedAveragePriceOfCommonStockPercent" nillable="true" substitutionGroup="xbrli:item" type="num:percentItemType" xbrli:periodType="instant" />
  <xsd:element id="selb_ProceedsFromIssuanceOfCommonStockNet" name="ProceedsFromIssuanceOfCommonStockNet" nillable="true" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType" xbrli:balance="debit" xbrli:periodType="duration" />
  <xsd:element id="selb_PublicSecuritiesOfferingAmountAuthorized" name="PublicSecuritiesOfferingAmountAuthorized" nillable="true" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType" xbrli:balance="credit" xbrli:periodType="duration" />
  <xsd:element abstract="true" id="selb_RegulatoryMilestonesMember" name="RegulatoryMilestonesMember" nillable="true" substitutionGroup="xbrli:item" type="nonnum:domainItemType" xbrli:periodType="duration" />
  <xsd:element id="selb_ReimbursementInvoice" name="ReimbursementInvoice" nillable="true" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType" xbrli:balance="credit" xbrli:periodType="duration" />
  <xsd:element abstract="true" id="selb_ResearchAndDevelopmentMember" name="ResearchAndDevelopmentMember" nillable="true" substitutionGroup="xbrli:item" type="nonnum:domainItemType" xbrli:periodType="duration" />
  <xsd:element id="selb_RevenueNumberOfPerformanceObligations" name="RevenueNumberOfPerformanceObligations" nillable="true" substitutionGroup="xbrli:item" type="xbrli:integerItemType" xbrli:periodType="instant" />
  <xsd:element id="selb_RevenueRemainingPerformanceObligationEachOption" name="RevenueRemainingPerformanceObligationEachOption" nillable="true" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType" xbrli:balance="credit" xbrli:periodType="instant" />
  <xsd:element id="selb_RussiaVasedDevelopmentFundOfNewTechnologiesDevelopmentAndCommercializationCenterGrantAgreementMember" name="RussiaVasedDevelopmentFundOfNewTechnologiesDevelopmentAndCommercializationCenterGrantAgreementMember" nillable="true" substitutionGroup="xbrli:item" type="nonnum:domainItemType" xbrli:periodType="duration" />
  <xsd:element abstract="true" id="selb_SecondAcquisitionRightMember" name="SecondAcquisitionRightMember" nillable="true" substitutionGroup="xbrli:item" type="nonnum:domainItemType" xbrli:periodType="duration" />
  <xsd:element id="selb_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsWeightedAverageFairValue" name="ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsWeightedAverageFairValue" nillable="true" substitutionGroup="xbrli:item" type="num:perShareItemType" xbrli:periodType="instant" />
  <xsd:element id="selb_ShareBasedCompensationArrangementByShareBasedPaymentAwardForfeituresRate" name="ShareBasedCompensationArrangementByShareBasedPaymentAwardForfeituresRate" nillable="true" substitutionGroup="xbrli:item" type="num:percentItemType" xbrli:periodType="duration" />
  <xsd:element id="selb_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfSharesAvailableForGrantIncreaseDecrease" name="ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfSharesAvailableForGrantIncreaseDecrease" nillable="true" substitutionGroup="xbrli:item" type="xbrli:sharesItemType" xbrli:periodType="duration" />
  <xsd:element abstract="true" id="selb_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingIntrinsicValueAbstract" name="ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingIntrinsicValueAbstract" nillable="true" substitutionGroup="xbrli:item" type="xbrli:stringItemType" xbrli:periodType="duration" />
  <xsd:element abstract="true" id="selb_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingWeightedAverageRemainingContractualTermAbstract" name="ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingWeightedAverageRemainingContractualTermAbstract" nillable="true" substitutionGroup="xbrli:item" type="xbrli:stringItemType" xbrli:periodType="duration" />
  <xsd:element id="selb_ShareBasedCompensationArrangementByShareBasedPaymentAwardVotingRightsOfCommonStockHoldingPercentage" name="ShareBasedCompensationArrangementByShareBasedPaymentAwardVotingRightsOfCommonStockHoldingPercentage" nillable="true" substitutionGroup="xbrli:item" type="num:percentItemType" xbrli:periodType="duration" />
  <xsd:element id="selb_ShareBasedGoodsAndNonEmployeeServicesTransactionCompensationNotYetRecognizedStockOptions" name="ShareBasedGoodsAndNonEmployeeServicesTransactionCompensationNotYetRecognizedStockOptions" nillable="true" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType" xbrli:balance="debit" xbrli:periodType="instant" />
  <xsd:element id="selb_ShareBasedGoodsAndNonEmployeeServicesTransactionCompensationNotYetRecognizedStockOptionsPeriod" name="ShareBasedGoodsAndNonEmployeeServicesTransactionCompensationNotYetRecognizedStockOptionsPeriod" nillable="true" substitutionGroup="xbrli:item" type="xbrli:durationItemType" xbrli:periodType="duration" />
  <xsd:element id="selb_SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsVestedOutstandingIntrinsicValue" name="SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsVestedOutstandingIntrinsicValue" nillable="true" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType" xbrli:balance="debit" xbrli:periodType="instant" />
  <xsd:element id="selb_SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsVestedOutstandingWeightedAverageRemainingContractualTerm" name="SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsVestedOutstandingWeightedAverageRemainingContractualTerm" nillable="true" substitutionGroup="xbrli:item" type="xbrli:durationItemType" xbrli:periodType="duration" />
  <xsd:element id="selb_SharebasedCompensationArrangementbySharebasedPaymentAwardOptionsVestedWeightedAverageExercisePrice" name="SharebasedCompensationArrangementbySharebasedPaymentAwardOptionsVestedWeightedAverageExercisePrice" nillable="true" substitutionGroup="xbrli:item" type="num:perShareItemType" xbrli:periodType="duration" />
  <xsd:element abstract="true" id="selb_SparkLetterAgreementMember" name="SparkLetterAgreementMember" nillable="true" substitutionGroup="xbrli:item" type="nonnum:domainItemType" xbrli:periodType="duration" />
  <xsd:element abstract="true" id="selb_SpringerPurchaseAgreementMember" name="SpringerPurchaseAgreementMember" nillable="true" substitutionGroup="xbrli:item" type="nonnum:domainItemType" xbrli:periodType="duration" />
  <xsd:element abstract="true" id="selb_StockIncentivePlan2008Member" name="StockIncentivePlan2008Member" nillable="true" substitutionGroup="xbrli:item" type="nonnum:domainItemType" xbrli:periodType="duration" />
  <xsd:element id="selb_StockIncentivePlan2016Member" name="StockIncentivePlan2016Member" nillable="true" substitutionGroup="xbrli:item" type="nonnum:domainItemType" xbrli:periodType="duration" />
  <xsd:element id="selb_StockPurchaseAgreementAuthorizedAmountOfStockToSell" name="StockPurchaseAgreementAuthorizedAmountOfStockToSell" nillable="true" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType" xbrli:balance="debit" xbrli:periodType="instant" />
  <xsd:element id="selb_StockPurchaseProgramAggregatePurchasePricePerShare" name="StockPurchaseProgramAggregatePurchasePricePerShare" nillable="true" substitutionGroup="xbrli:item" type="num:perShareItemType" xbrli:periodType="duration" />
  <xsd:element id="selb_StockPurchaseProgramNumberOfSharesAuthorizedToBeSold" name="StockPurchaseProgramNumberOfSharesAuthorizedToBeSold" nillable="true" substitutionGroup="xbrli:item" type="xbrli:sharesItemType" xbrli:periodType="instant" />
  <xsd:element id="selb_TermLoanMember" name="TermLoanMember" nillable="true" substitutionGroup="xbrli:item" type="nonnum:domainItemType" xbrli:periodType="duration" />
  <xsd:element id="selb_TermLoanNumberofPayments" name="TermLoanNumberofPayments" nillable="true" substitutionGroup="xbrli:item" type="xbrli:integerItemType" xbrli:periodType="duration" />
  <xsd:element id="selb_TermLoanPrepaidAfterSecondAnniversaryMember" name="TermLoanPrepaidAfterSecondAnniversaryMember" nillable="true" substitutionGroup="xbrli:item" type="nonnum:domainItemType" xbrli:periodType="duration" />
  <xsd:element abstract="true" id="selb_The2008PlanAndThe2016PlanMember" name="The2008PlanAndThe2016PlanMember" nillable="true" substitutionGroup="xbrli:item" type="nonnum:domainItemType" xbrli:periodType="duration" />
  <xsd:element abstract="true" id="selb_UnrestrictedCashMember" name="UnrestrictedCashMember" nillable="true" substitutionGroup="xbrli:item" type="nonnum:domainItemType" xbrli:periodType="duration" />
  <xsd:element id="selb_VotesPerShareofCommonStock" name="VotesPerShareofCommonStock" nillable="true" substitutionGroup="xbrli:item" type="xbrli:integerItemType" xbrli:periodType="instant" />
  <xsd:element id="selb_WarrantIssued" name="WarrantIssued" nillable="true" substitutionGroup="xbrli:item" type="xbrli:monetaryItemType" xbrli:balance="credit" xbrli:periodType="duration" />
  <xsd:element id="selb_WarrantsPolicyTextBlock" name="WarrantsPolicyTextBlock" nillable="true" substitutionGroup="xbrli:item" type="nonnum:textBlockItemType" xbrli:periodType="duration" />
</xsd:schema>
