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      <link:linkbaseRef xlink:type="simple" xlink:href="selb-20160630_def.xml" xlink:role="http://www.xbrl.org/2003/role/definitionLinkbaseRef" xlink:arcrole="http://www.w3.org/1999/xlink/properties/linkbase" />
      <link:linkbaseRef xlink:type="simple" xlink:href="selb-20160630_lab.xml" xlink:role="http://www.xbrl.org/2003/role/labelLinkbaseRef" xlink:arcrole="http://www.w3.org/1999/xlink/properties/linkbase" />
      <link:linkbaseRef xlink:type="simple" xlink:href="selb-20160630_cal.xml" xlink:role="http://www.xbrl.org/2003/role/calculationLinkbaseRef" xlink:arcrole="http://www.w3.org/1999/xlink/properties/linkbase" xlink:title="Calculation Links, all" />
    </xsd:appinfo>
  </xsd:annotation>
  <xsd:import namespace="http://xbrl.sec.gov/dei/2014-01-31" schemaLocation="http://xbrl.sec.gov/dei/2014/dei-2014-01-31.xsd" />
  <xsd:import namespace="http://www.xbrl.org/2009/role/negated" schemaLocation="http://www.xbrl.org/lrr/role/negated-2009-12-16.xsd" />
  <xsd:import namespace="http://www.xbrl.org/dtr/type/non-numeric" schemaLocation="http://www.xbrl.org/dtr/type/nonNumeric-2009-12-16.xsd" />
  <xsd:import namespace="http://www.xbrl.org/dtr/type/numeric" schemaLocation="http://www.xbrl.org/dtr/type/numeric-2009-12-16.xsd" />
  <xsd:import namespace="http://www.xbrl.org/2003/instance" schemaLocation="http://www.xbrl.org/2003/xbrl-instance-2003-12-31.xsd" />
  <xsd:import namespace="http://xbrl.org/2005/xbrldt" schemaLocation="http://www.xbrl.org/2005/xbrldt-2005.xsd" />
  <import namespace="http://fasb.org/us-gaap/2016-01-31" schemaLocation="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd" xmlns="http://www.w3.org/2001/XMLSchema" />
  <import namespace="http://xbrl.sec.gov/currency/2016-01-31" schemaLocation="http://xbrl.sec.gov/currency/2016/currency-2016-01-31.xsd" xmlns="http://www.w3.org/2001/XMLSchema" />
  <import namespace="http://xbrl.sec.gov/country/2016-01-31" schemaLocation="http://xbrl.sec.gov/country/2016/country-2016-01-31.xsd" xmlns="http://www.w3.org/2001/XMLSchema" />
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  <element id="selb_SeriesSrnRedeemableConvertiblePreferredStockMember" name="SeriesSrnRedeemableConvertiblePreferredStockMember" nillable="true" type="nonnum:domainItemType" substitutionGroup="xbrli:item" abstract="true" xbrli:periodType="duration" xmlns="http://www.w3.org/2001/XMLSchema" />
  <element id="selb_SeriesERedeemableConvertiblePreferredStockMember" name="SeriesERedeemableConvertiblePreferredStockMember" nillable="true" type="nonnum:domainItemType" substitutionGroup="xbrli:item" abstract="true" xbrli:periodType="duration" xmlns="http://www.w3.org/2001/XMLSchema" />
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  <element id="selb_IncreaseDecreaseInContingentlyRepayableGrantFunding" name="IncreaseDecreaseInContingentlyRepayableGrantFunding" nillable="true" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" xbrli:balance="debit" xmlns="http://www.w3.org/2001/XMLSchema" />
  <element id="selb_AccruedRentAndLeaseIncentivePayableCurrent" name="AccruedRentAndLeaseIncentivePayableCurrent" nillable="true" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="instant" xbrli:balance="credit" xmlns="http://www.w3.org/2001/XMLSchema" />
  <element id="selb_AccruedPatentFeesCurrent" name="AccruedPatentFeesCurrent" nillable="true" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="instant" xbrli:balance="credit" xmlns="http://www.w3.org/2001/XMLSchema" />
  <element id="selb_AccruedResearchAndDevelopmentCostsCurrent" name="AccruedResearchAndDevelopmentCostsCurrent" nillable="true" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="instant" xbrli:balance="credit" xmlns="http://www.w3.org/2001/XMLSchema" />
  <element id="selb_LaboratoryEquipmentMember" name="LaboratoryEquipmentMember" nillable="true" type="nonnum:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" xmlns="http://www.w3.org/2001/XMLSchema" />
  <element id="selb_CashEquivalentsAndShortTermInvestmentsPolicyTextBlock" name="CashEquivalentsAndShortTermInvestmentsPolicyTextBlock" nillable="true" type="nonnum:textBlockItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" xmlns="http://www.w3.org/2001/XMLSchema" />
  <element id="selb_RevenueRecognitionGrantRevenuePolicyTextBlock" name="RevenueRecognitionGrantRevenuePolicyTextBlock" nillable="true" type="nonnum:textBlockItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" xmlns="http://www.w3.org/2001/XMLSchema" />
  <element id="selb_ClinicalTrialCostsPolicyTextBlock" name="ClinicalTrialCostsPolicyTextBlock" nillable="true" type="nonnum:textBlockItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" xmlns="http://www.w3.org/2001/XMLSchema" />
  <element id="selb_WarrantsPolicyTextBlock" name="WarrantsPolicyTextBlock" nillable="true" type="nonnum:textBlockItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" xmlns="http://www.w3.org/2001/XMLSchema" />
  <element id="selb_DeferredRentPolicyTextBlock" name="DeferredRentPolicyTextBlock" nillable="true" type="nonnum:textBlockItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" xmlns="http://www.w3.org/2001/XMLSchema" />
  <element id="selb_ClassOfWarrantOrRightTermOfWarrantsOrRights" name="ClassOfWarrantOrRightTermOfWarrantsOrRights" nillable="true" type="xbrli:durationItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" xmlns="http://www.w3.org/2001/XMLSchema" />
  <element id="selb_LaboratoryAndOfficeSpaceMember" name="LaboratoryAndOfficeSpaceMember" nillable="true" type="nonnum:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" xmlns="http://www.w3.org/2001/XMLSchema" />
  <element id="selb_RestrictedCashAndOtherDepositsMember" name="RestrictedCashAndOtherDepositsMember" nillable="true" type="nonnum:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" xmlns="http://www.w3.org/2001/XMLSchema" />
  <element id="selb_Deferredrentandleaseincentiveliability" name="Deferredrentandleaseincentiveliability" nillable="true" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="instant" xbrli:balance="debit" xmlns="http://www.w3.org/2001/XMLSchema" />
  <element id="selb_TermLoanMember" name="TermLoanMember" nillable="true" type="nonnum:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" xmlns="http://www.w3.org/2001/XMLSchema" />
  <element id="selb_TermLoanPrepaidPriorToFirstAnniversaryMember" name="TermLoanPrepaidPriorToFirstAnniversaryMember" nillable="true" type="nonnum:domainItemType" substitutionGroup="xbrli:item" abstract="true" xbrli:periodType="duration" xmlns="http://www.w3.org/2001/XMLSchema" />
  <element id="selb_TermLoanPrepaidAfterFirstAnniversaryButBeforeSecondAnniversaryMember" name="TermLoanPrepaidAfterFirstAnniversaryButBeforeSecondAnniversaryMember" nillable="true" type="nonnum:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" xmlns="http://www.w3.org/2001/XMLSchema" />
  <element id="selb_TermLoanPrepaidAfterSecondAnniversaryMember" name="TermLoanPrepaidAfterSecondAnniversaryMember" nillable="true" type="nonnum:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" xmlns="http://www.w3.org/2001/XMLSchema" />
  <element id="selb_Numberoflenders" name="Numberoflenders" nillable="true" type="xbrli:integerItemType" substitutionGroup="xbrli:item" xbrli:periodType="instant" xmlns="http://www.w3.org/2001/XMLSchema" />
  <element id="selb_EarlyExtinguishmentOfDebtPrepaymentFeePercentage" name="EarlyExtinguishmentOfDebtPrepaymentFeePercentage" nillable="true" type="num:percentItemType" substitutionGroup="xbrli:item" xbrli:periodType="instant" xmlns="http://www.w3.org/2001/XMLSchema" />
  <element id="selb_FinalPaymentFeePercentage" name="FinalPaymentFeePercentage" nillable="true" type="num:percentItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" xmlns="http://www.w3.org/2001/XMLSchema" />
  <element id="selb_FinalPaymentFee" name="FinalPaymentFee" nillable="true" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" xbrli:balance="debit" xmlns="http://www.w3.org/2001/XMLSchema" />
  <element id="selb_WarrantsGrantDateFairValue" name="WarrantsGrantDateFairValue" nillable="true" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="instant" xbrli:balance="debit" xmlns="http://www.w3.org/2001/XMLSchema" />
  <element id="selb_NonEmployeeStockOptionMember" name="NonEmployeeStockOptionMember" nillable="true" type="nonnum:domainItemType" substitutionGroup="xbrli:item" abstract="true" xbrli:periodType="duration" xmlns="http://www.w3.org/2001/XMLSchema" />
  <element id="selb_StockIncentivePlan2008Member" name="StockIncentivePlan2008Member" nillable="true" type="nonnum:domainItemType" substitutionGroup="xbrli:item" abstract="true" xbrli:periodType="duration" xmlns="http://www.w3.org/2001/XMLSchema" />
  <element id="selb_ShareBasedCompensationArrangementByShareBasedPaymentAwardVotingRightsOfCommonStockHoldingPercentage" name="ShareBasedCompensationArrangementByShareBasedPaymentAwardVotingRightsOfCommonStockHoldingPercentage" nillable="true" type="num:percentItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" xmlns="http://www.w3.org/2001/XMLSchema" />
  <element id="selb_ShareBasedCompensationArrangementByShareBasedPaymentAwardForfeituresRate" name="ShareBasedCompensationArrangementByShareBasedPaymentAwardForfeituresRate" nillable="true" type="num:percentItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" xmlns="http://www.w3.org/2001/XMLSchema" />
  <element id="selb_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsVestedWeightedAverageExercisePrice" name="ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsVestedWeightedAverageExercisePrice" nillable="true" type="xbrli:decimalItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" xmlns="http://www.w3.org/2001/XMLSchema" />
  <element id="selb_NonEmployeeServiceShareBasedCompensationNonvestedAwardsCompensationNotYetRecognizedStockOptions" name="NonEmployeeServiceShareBasedCompensationNonvestedAwardsCompensationNotYetRecognizedStockOptions" nillable="true" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="instant" xbrli:balance="debit" xmlns="http://www.w3.org/2001/XMLSchema" />
  <element id="selb_LiabilityUnderRepurchaseProvisionAgreement" name="LiabilityUnderRepurchaseProvisionAgreement" nillable="true" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="instant" xbrli:balance="debit" xmlns="http://www.w3.org/2001/XMLSchema" />
  <element id="selb_ResearchAndDevelopmentMember" name="ResearchAndDevelopmentMember" nillable="true" type="nonnum:domainItemType" substitutionGroup="xbrli:item" abstract="true" xbrli:periodType="duration" xmlns="http://www.w3.org/2001/XMLSchema" />
  <element id="selb_LandlordMember" name="LandlordMember" nillable="true" type="nonnum:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" xmlns="http://www.w3.org/2001/XMLSchema" />
  <element id="selb_FounderMember" name="FounderMember" nillable="true" type="nonnum:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" xmlns="http://www.w3.org/2001/XMLSchema" />
  <element id="selb_CollaborativeArrangementAbstract" name="CollaborativeArrangementAbstract" nillable="true" type="xbrli:stringItemType" substitutionGroup="xbrli:item" abstract="true" xbrli:periodType="duration" xmlns="http://www.w3.org/2001/XMLSchema" />
  <element id="selb_SanofiCollaborationAgreementMember" name="SanofiCollaborationAgreementMember" nillable="true" type="nonnum:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" xmlns="http://www.w3.org/2001/XMLSchema" />
  <element id="selb_PeriodBeforeWhichNominatedDevelopmentCandidateCanBeReplacedWithNewDevelopmentCandidate" name="PeriodBeforeWhichNominatedDevelopmentCandidateCanBeReplacedWithNewDevelopmentCandidate" nillable="true" type="xbrli:durationItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" xmlns="http://www.w3.org/2001/XMLSchema" />
  <element id="selb_InitialPaymentForFirstIndication" name="InitialPaymentForFirstIndication" nillable="true" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" xbrli:balance="debit" xmlns="http://www.w3.org/2001/XMLSchema" />
  <element id="selb_AdditionalPaymentForSecondIndication" name="AdditionalPaymentForSecondIndication" nillable="true" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" xbrli:balance="debit" xmlns="http://www.w3.org/2001/XMLSchema" />
  <element id="selb_AdditionalPaymentForPreclinicalResearchForEachIndication" name="AdditionalPaymentForPreclinicalResearchForEachIndication" nillable="true" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" xbrli:balance="debit" xmlns="http://www.w3.org/2001/XMLSchema" />
  <element id="selb_NationalInstitutesOfHealthGrantAgreementMember" name="NationalInstitutesOfHealthGrantAgreementMember" nillable="true" type="nonnum:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" xmlns="http://www.w3.org/2001/XMLSchema" />
  <element id="selb_JuvenileDiabetesResearchFoundationGrantAgreementMember" name="JuvenileDiabetesResearchFoundationGrantAgreementMember" nillable="true" type="nonnum:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" xmlns="http://www.w3.org/2001/XMLSchema" />
  <element id="selb_BillAndMelindaGatesFoundationGrantAgreementMember" name="BillAndMelindaGatesFoundationGrantAgreementMember" nillable="true" type="nonnum:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" xmlns="http://www.w3.org/2001/XMLSchema" />
  <element id="selb_RussianMinistryOfIndustryAndTradeGrantAgreementMember" name="RussianMinistryOfIndustryAndTradeGrantAgreementMember" nillable="true" type="nonnum:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" xmlns="http://www.w3.org/2001/XMLSchema" />
  <element id="selb_RussiaVasedDevelopmentFundOfNewTechnologiesDevelopmentAndCommercializationCenterGrantAgreementMember" name="RussiaVasedDevelopmentFundOfNewTechnologiesDevelopmentAndCommercializationCenterGrantAgreementMember" nillable="true" type="nonnum:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" xmlns="http://www.w3.org/2001/XMLSchema" />
  <element id="selb_DevelopmentCandidateMilestonePayable" name="DevelopmentCandidateMilestonePayable" nillable="true" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="instant" xbrli:balance="credit" xmlns="http://www.w3.org/2001/XMLSchema" />
  <element id="selb_FurtherDevelopmentMilestones" name="FurtherDevelopmentMilestones" nillable="true" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="instant" xbrli:balance="credit" xmlns="http://www.w3.org/2001/XMLSchema" />
  <element id="selb_AggregateAmountForIndicationAndFilingFirstBiologicLicenseApplication" name="AggregateAmountForIndicationAndFilingFirstBiologicLicenseApplication" nillable="true" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="instant" xbrli:balance="credit" xmlns="http://www.w3.org/2001/XMLSchema" />
  <element id="selb_PortionAttributableToInitiationOfPhase3ClinicalTrailAndFilingOfFirstBiologicLicenseApplication" name="PortionAttributableToInitiationOfPhase3ClinicalTrailAndFilingOfFirstBiologicLicenseApplication" nillable="true" type="num:percentItemType" substitutionGroup="xbrli:item" xbrli:periodType="instant" xmlns="http://www.w3.org/2001/XMLSchema" />
  <element id="selb_AggregateAmountUponAchievingVariousRegulatoryApprovals" name="AggregateAmountUponAchievingVariousRegulatoryApprovals" nillable="true" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="instant" xbrli:balance="credit" xmlns="http://www.w3.org/2001/XMLSchema" />
  <element id="selb_AggregateAmountOfSalesMilestones" name="AggregateAmountOfSalesMilestones" nillable="true" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="instant" xbrli:balance="credit" xmlns="http://www.w3.org/2001/XMLSchema" />
  <element id="selb_NumberOfGrants" name="NumberOfGrants" nillable="true" type="xbrli:integerItemType" substitutionGroup="xbrli:item" xbrli:periodType="instant" xmlns="http://www.w3.org/2001/XMLSchema" />
  <element id="selb_GrantsFromEntitiesAmountOfGrantAward" name="GrantsFromEntitiesAmountOfGrantAward" nillable="true" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" xbrli:balance="debit" xmlns="http://www.w3.org/2001/XMLSchema" />
  <element id="selb_ExtendedResearchTerm" name="ExtendedResearchTerm" nillable="true" type="xbrli:durationItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" xmlns="http://www.w3.org/2001/XMLSchema" />
  <element id="selb_RepaymentOfGrantFundingReceived" name="RepaymentOfGrantFundingReceived" nillable="true" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" xbrli:balance="credit" xmlns="http://www.w3.org/2001/XMLSchema" />
  <element id="selb_PenaltyFeePercentageOfContractValue" name="PenaltyFeePercentageOfContractValue" nillable="true" type="num:percentItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" xmlns="http://www.w3.org/2001/XMLSchema" />
  <element id="selb_PenaltyFeeAmount" name="PenaltyFeeAmount" nillable="true" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" xbrli:balance="debit" xmlns="http://www.w3.org/2001/XMLSchema" />
  <element id="selb_PeriodToAuditExpenditureIncurred" name="PeriodToAuditExpenditureIncurred" nillable="true" type="xbrli:durationItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" xmlns="http://www.w3.org/2001/XMLSchema" />
  <element id="selb_PercentageOfEstimatedCostOfResearchPlan" name="PercentageOfEstimatedCostOfResearchPlan" nillable="true" type="num:percentItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" xmlns="http://www.w3.org/2001/XMLSchema" />
  <element id="selb_RemainingPercentageContributedByEntity" name="RemainingPercentageContributedByEntity" nillable="true" type="num:percentItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" xmlns="http://www.w3.org/2001/XMLSchema" />
  <element id="selb_DefinedContributionPlanEmployersMatchingContributionVestingPeriod" name="DefinedContributionPlanEmployersMatchingContributionVestingPeriod" nillable="true" type="xbrli:durationItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" xmlns="http://www.w3.org/2001/XMLSchema" />
  <element id="selb_TechonologyLicenseAgreementsAbstract" name="TechonologyLicenseAgreementsAbstract" nillable="true" type="xbrli:stringItemType" substitutionGroup="xbrli:item" abstract="true" xbrli:periodType="duration" xmlns="http://www.w3.org/2001/XMLSchema" />
  <element id="selb_TechonologyLicenseAgreementsTextBlock" name="TechonologyLicenseAgreementsTextBlock" nillable="true" type="nonnum:textBlockItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" xmlns="http://www.w3.org/2001/XMLSchema" />
  <element id="selb_ExclusivePatentLicenseAgreementWithMassachusettsInstituteOfTechnologyMember" name="ExclusivePatentLicenseAgreementWithMassachusettsInstituteOfTechnologyMember" nillable="true" type="nonnum:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" xmlns="http://www.w3.org/2001/XMLSchema" />
  <element id="selb_LicenseAgreementWithShenyangSunshinePharmaceuticalCompanyLimitedMember" name="LicenseAgreementWithShenyangSunshinePharmaceuticalCompanyLimitedMember" nillable="true" type="nonnum:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" xmlns="http://www.w3.org/2001/XMLSchema" />
  <element id="selb_PercentageOfSublicenseIncome" name="PercentageOfSublicenseIncome" nillable="true" type="num:percentItemType" substitutionGroup="xbrli:item" xbrli:periodType="instant" xmlns="http://www.w3.org/2001/XMLSchema" />
  <element id="selb_PaymentAmountUponAchievementOfDefinedClinicalMilestones" name="PaymentAmountUponAchievementOfDefinedClinicalMilestones" nillable="true" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" xbrli:balance="debit" xmlns="http://www.w3.org/2001/XMLSchema" />
  <element id="selb_PeriodForCommericalizationOfProduct" name="PeriodForCommericalizationOfProduct" nillable="true" type="xbrli:durationItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" xmlns="http://www.w3.org/2001/XMLSchema" />
  <element id="selb_AggregateAmountOfUpfrontAndMilestoneBasedPayments" name="AggregateAmountOfUpfrontAndMilestoneBasedPayments" nillable="true" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" xbrli:balance="debit" xmlns="http://www.w3.org/2001/XMLSchema" />
  <element id="selb_AggregateAmountForFuturePaymentsUponAchievementOfClinicalAndRegulatoryApprovalMilestonesForProductsContainingSvpTechnology" name="AggregateAmountForFuturePaymentsUponAchievementOfClinicalAndRegulatoryApprovalMilestonesForProductsContainingSvpTechnology" nillable="true" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" xbrli:balance="debit" xmlns="http://www.w3.org/2001/XMLSchema" />
  <element id="selb_AggregateAmountForFuturePaymentsUponAchievementOfClinicalAndRegulatoryApprovalMilestonesForProductsWithoutSvpTechnology" name="AggregateAmountForFuturePaymentsUponAchievementOfClinicalAndRegulatoryApprovalMilestonesForProductsWithoutSvpTechnology" nillable="true" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" xbrli:balance="debit" xmlns="http://www.w3.org/2001/XMLSchema" />
  <element id="selb_PeriodForPriorWrittenNoticeToTerminateLicense" name="PeriodForPriorWrittenNoticeToTerminateLicense" nillable="true" type="xbrli:durationItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" xmlns="http://www.w3.org/2001/XMLSchema" />
  <element id="selb_PercentageOfConvertibleNotesForWhichWarrantsIssuedToPurchaseCommonStock" name="PercentageOfConvertibleNotesForWhichWarrantsIssuedToPurchaseCommonStock" nillable="true" type="num:percentItemType" substitutionGroup="xbrli:item" xbrli:periodType="instant" xmlns="http://www.w3.org/2001/XMLSchema" />
  <element id="selb_WarrantsOrRightsTerm" name="WarrantsOrRightsTerm" nillable="true" type="xbrli:durationItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" xmlns="http://www.w3.org/2001/XMLSchema" />
  <element id="selb_SeriesaRedeemableConvertiblePreferredStockMember" name="SeriesaRedeemableConvertiblePreferredStockMember" nillable="true" type="nonnum:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" xmlns="http://www.w3.org/2001/XMLSchema" />
  <element id="selb_OtherResearchAndCollaborationAgreementsMember" name="OtherResearchAndCollaborationAgreementsMember" nillable="true" type="nonnum:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" xmlns="http://www.w3.org/2001/XMLSchema" />
  <element id="selb_InvestmentsMaturityPeriod" name="InvestmentsMaturityPeriod" nillable="true" type="xbrli:durationItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" xmlns="http://www.w3.org/2001/XMLSchema" />
  <element id="selb_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsWeightedAverageFairValue" name="ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsWeightedAverageFairValue" nillable="true" type="num:perShareItemType" substitutionGroup="xbrli:item" xbrli:periodType="instant" xmlns="http://www.w3.org/2001/XMLSchema" />
  <element id="selb_StockVestedDuringPeriodValueRestrictedCommonStock" name="StockVestedDuringPeriodValueRestrictedCommonStock" nillable="true" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" xbrli:balance="credit" xmlns="http://www.w3.org/2001/XMLSchema" />
  <element id="selb_StockVestedDuringPeriodShareRestrictedCommonStock" name="StockVestedDuringPeriodShareRestrictedCommonStock" nillable="true" type="xbrli:sharesItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" xmlns="http://www.w3.org/2001/XMLSchema" />
  <element id="selb_StockholdersEquityAccretionToRedemptionValue" name="StockholdersEquityAccretionToRedemptionValue" nillable="true" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" xbrli:balance="debit" xmlns="http://www.w3.org/2001/XMLSchema" />
  <element id="selb_TemporaryEquityDisclosureTextBlock" name="TemporaryEquityDisclosureTextBlock" nillable="true" type="nonnum:textBlockItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" xmlns="http://www.w3.org/2001/XMLSchema" />
  <element id="selb_TemporaryEquityStockIssuedDuringPeriodShareNewIssues" name="TemporaryEquityStockIssuedDuringPeriodShareNewIssues" nillable="true" type="xbrli:sharesItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" xmlns="http://www.w3.org/2001/XMLSchema" />
  <element id="selb_TemporaryEquityConversionPricePerShare" name="TemporaryEquityConversionPricePerShare" nillable="true" type="num:perShareItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" xmlns="http://www.w3.org/2001/XMLSchema" />
  <element id="selb_ProceedsFromIssuanceOfRedeemableConvertiblePreferredStockGross" name="ProceedsFromIssuanceOfRedeemableConvertiblePreferredStockGross" nillable="true" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" xbrli:balance="debit" xmlns="http://www.w3.org/2001/XMLSchema" />
  <element id="selb_PercentageOfWarrantsToPurchaseCommonStock" name="PercentageOfWarrantsToPurchaseCommonStock" nillable="true" type="num:percentItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" xmlns="http://www.w3.org/2001/XMLSchema" />
  <element id="selb_FirstGrantMember" name="FirstGrantMember" nillable="true" type="nonnum:domainItemType" substitutionGroup="xbrli:item" abstract="true" xbrli:periodType="duration" xmlns="http://www.w3.org/2001/XMLSchema" />
  <element id="selb_SecondGrantMember" name="SecondGrantMember" nillable="true" type="nonnum:domainItemType" substitutionGroup="xbrli:item" abstract="true" xbrli:periodType="duration" xmlns="http://www.w3.org/2001/XMLSchema" />
  <element id="selb_NonEmployeeServiceShareBasedCompensationNonvestedAwardsCompensationExpensesStockOptions" name="NonEmployeeServiceShareBasedCompensationNonvestedAwardsCompensationExpensesStockOptions" nillable="true" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="instant" xbrli:balance="debit" xmlns="http://www.w3.org/2001/XMLSchema" />
  <element id="selb_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingWeightedAverageRemainingContractualTermAbstract" name="ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingWeightedAverageRemainingContractualTermAbstract" nillable="true" type="xbrli:stringItemType" substitutionGroup="xbrli:item" abstract="true" xbrli:periodType="duration" xmlns="http://www.w3.org/2001/XMLSchema" />
  <element id="selb_Sharebasedcompensationarrangementbysharebasedpaymentawardoptionsvestedoutstandingweightedaverageremainingcontractualterm2" name="Sharebasedcompensationarrangementbysharebasedpaymentawardoptionsvestedoutstandingweightedaverageremainingcontractualterm2" nillable="true" type="xbrli:durationItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" xmlns="http://www.w3.org/2001/XMLSchema" />
  <element id="selb_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingIntrinsicValueAbstract" name="ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingIntrinsicValueAbstract" nillable="true" type="xbrli:stringItemType" substitutionGroup="xbrli:item" abstract="true" xbrli:periodType="duration" xmlns="http://www.w3.org/2001/XMLSchema" />
  <element id="selb_Sharebasedcompensationarrangementbysharebasedpaymentawardoptionsvestedoutstandingintrinsicvalue" name="Sharebasedcompensationarrangementbysharebasedpaymentawardoptionsvestedoutstandingintrinsicvalue" nillable="true" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="instant" xbrli:balance="debit" xmlns="http://www.w3.org/2001/XMLSchema" />
  <element id="selb_DefinedContribution401kPlanMember" name="DefinedContribution401kPlanMember" nillable="true" type="nonnum:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" xmlns="http://www.w3.org/2001/XMLSchema" />
  <element id="selb_TemporaryEquityConversionOfConvertibleStockValue" name="TemporaryEquityConversionOfConvertibleStockValue" nillable="true" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" xbrli:balance="debit" xmlns="http://www.w3.org/2001/XMLSchema" />
  <element id="selb_TemporaryEquityConversionOfConvertibleStockShares" name="TemporaryEquityConversionOfConvertibleStockShares" nillable="true" type="xbrli:sharesItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" xmlns="http://www.w3.org/2001/XMLSchema" />
  <element id="selb_StockIssuedDuringPeriodValueConversionPreferredStockWarrants" name="StockIssuedDuringPeriodValueConversionPreferredStockWarrants" nillable="true" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" xbrli:balance="credit" xmlns="http://www.w3.org/2001/XMLSchema" />
  <element id="selb_StockIssuanceCosts" name="StockIssuanceCosts" nillable="true" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" xbrli:balance="debit" xmlns="http://www.w3.org/2001/XMLSchema" />
  <element id="selb_StockIssuedDuringPeriodSharesWarrantsExercised" name="StockIssuedDuringPeriodSharesWarrantsExercised" nillable="true" type="xbrli:sharesItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" xmlns="http://www.w3.org/2001/XMLSchema" />
  <element id="selb_ProceedsFromVestingOfRestrictedStock" name="ProceedsFromVestingOfRestrictedStock" nillable="true" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" xbrli:balance="debit" xmlns="http://www.w3.org/2001/XMLSchema" />
  <element id="selb_NoncashOrPartialNoncashReclassificationOfDeferredIpoCostsFromNonCurrentAssetsToAdditionalPaidInCapital" name="NoncashOrPartialNoncashReclassificationOfDeferredIpoCostsFromNonCurrentAssetsToAdditionalPaidInCapital" nillable="true" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" xbrli:balance="credit" xmlns="http://www.w3.org/2001/XMLSchema" />
  <element id="selb_NoncashOrPartialNoncashTransactionInitialPublicOfferingCostsInAccountsPayableAndAccruedLiabilities" name="NoncashOrPartialNoncashTransactionInitialPublicOfferingCostsInAccountsPayableAndAccruedLiabilities" nillable="true" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" xbrli:balance="credit" xmlns="http://www.w3.org/2001/XMLSchema" />
  <element id="selb_GrossProceedsFromStockIssuedDuringPeriodNewIssues" name="GrossProceedsFromStockIssuedDuringPeriodNewIssues" nillable="true" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" xbrli:balance="debit" xmlns="http://www.w3.org/2001/XMLSchema" />
  <element id="selb_PaymentsForUnderwritingCommissions" name="PaymentsForUnderwritingCommissions" nillable="true" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" xbrli:balance="credit" xmlns="http://www.w3.org/2001/XMLSchema" />
  <element id="selb_ConvertiblePreferredStockWarrantsFairValueOfUnderlyingCommonShares" name="ConvertiblePreferredStockWarrantsFairValueOfUnderlyingCommonShares" nillable="true" type="num:perShareItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" xmlns="http://www.w3.org/2001/XMLSchema" />
  <element id="selb_LaboratoryAndOfficeSpaceAgreementAmendmentApril2015Member" name="LaboratoryAndOfficeSpaceAgreementAmendmentApril2015Member" nillable="true" type="nonnum:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" xmlns="http://www.w3.org/2001/XMLSchema" />
  <element id="selb_TermLoanNumberOfMonthlyPayments" name="TermLoanNumberOfMonthlyPayments" nillable="true" type="xbrli:integerItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" xmlns="http://www.w3.org/2001/XMLSchema" />
  <element id="selb_DebtInstrumentInterestPortion" name="DebtInstrumentInterestPortion" nillable="true" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="instant" xbrli:balance="credit" xmlns="http://www.w3.org/2001/XMLSchema" />
  <element id="selb_LicenseAgreementWithMassachusettsEyeAndEarInfirmaryAndSchepensEyeResearchInstituteInc.Member" name="LicenseAgreementWithMassachusettsEyeAndEarInfirmaryAndSchepensEyeResearchInstituteInc.Member" nillable="true" type="nonnum:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" xmlns="http://www.w3.org/2001/XMLSchema" />
  <element id="selb_DevelopmentMilestoneMethodAmountPaid" name="DevelopmentMilestoneMethodAmountPaid" nillable="true" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" xbrli:balance="debit" xmlns="http://www.w3.org/2001/XMLSchema" />
  <element id="selb_SalesMilestoneMethodAmountPaid" name="SalesMilestoneMethodAmountPaid" nillable="true" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" xbrli:balance="debit" xmlns="http://www.w3.org/2001/XMLSchema" />
  <element id="selb_StockIncentivePlan2016Member" name="StockIncentivePlan2016Member" nillable="true" type="nonnum:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" xmlns="http://www.w3.org/2001/XMLSchema" />
  <element id="selb_NumberOfProductsMarketedAndSold" name="NumberOfProductsMarketedAndSold" nillable="true" type="xbrli:integerItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" xmlns="http://www.w3.org/2001/XMLSchema" />
  <element id="selb_EmployeeStockPurchasePlan2016Member" name="EmployeeStockPurchasePlan2016Member" nillable="true" type="nonnum:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" xmlns="http://www.w3.org/2001/XMLSchema" />
  <element id="selb_EmployeeStockPurchasePlanMaximumPercentageOfSharesReservedBasedOnSharesOutstanding" name="EmployeeStockPurchasePlanMaximumPercentageOfSharesReservedBasedOnSharesOutstanding" nillable="true" type="xbrli:pureItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" xmlns="http://www.w3.org/2001/XMLSchema" />
</xsd:schema>
