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    <link:label id="lab_us-gaap_CreditFacilityDomain_370C9BA17B2E80958DD3105CC3D2741B_label_en-US" xlink:label="lab_us-gaap_CreditFacilityDomain_370C9BA17B2E80958DD3105CC3D2741B" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Credit Facility [Domain]</link:label>
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    <link:labelArc order="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_us-gaap_CreditFacilityDomain_370C9BA17B2E80958DD3105CC3D2741B" xlink:to="lab_us-gaap_CreditFacilityDomain_370C9BA17B2E80958DD3105CC3D2741B" xlink:type="arc" />
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    <link:label id="lab_selb_TermLoanMember_E9701AA2E2EEEBB7CB5A105CC5061DAA_label_en-US" xlink:label="lab_selb_TermLoanMember_E9701AA2E2EEEBB7CB5A105CC5061DAA" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Term Loan [Member]</link:label>
    <link:label id="lab_selb_TermLoanMember_E9701AA2E2EEEBB7CB5A105CC5061DAA_documentation_en-US" xlink:label="lab_selb_TermLoanMember_E9701AA2E2EEEBB7CB5A105CC5061DAA" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:type="resource" xml:lang="en-US">Represents information pertaining to term loan member.</link:label>
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    <link:label id="lab_us-gaap_DebtInstrumentAxis_E33A8281D0946B9C1450104BB5A07423_label_en-US" xlink:label="lab_us-gaap_DebtInstrumentAxis_E33A8281D0946B9C1450104BB5A07423" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Debt Instrument [Axis]</link:label>
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    <link:labelArc order="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_us-gaap_DebtInstrumentAxis_E33A8281D0946B9C1450104BB5A07423" xlink:to="lab_us-gaap_DebtInstrumentAxis_E33A8281D0946B9C1450104BB5A07423" xlink:type="arc" />
    <link:label id="lab_us-gaap_DebtInstrumentNameDomain_9FB846C4190A63E60229104BB5A07294_terseLabel_en-US" xlink:label="lab_us-gaap_DebtInstrumentNameDomain_9FB846C4190A63E60229104BB5A07294" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Debt Instrument, Name [Domain]</link:label>
    <link:label id="lab_us-gaap_DebtInstrumentNameDomain_9FB846C4190A63E60229104BB5A07294_label_en-US" xlink:label="lab_us-gaap_DebtInstrumentNameDomain_9FB846C4190A63E60229104BB5A07294" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Debt Instrument, Name [Domain]</link:label>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_DebtInstrumentNameDomain" xlink:label="loc_us-gaap_DebtInstrumentNameDomain_9FB846C4190A63E60229104BB5A07294" xlink:type="locator" />
    <link:labelArc order="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_9FB846C4190A63E60229104BB5A07294" xlink:to="lab_us-gaap_DebtInstrumentNameDomain_9FB846C4190A63E60229104BB5A07294" xlink:type="arc" />
    <link:label id="lab_us-gaap_ConvertibleNotesPayableMember_924BDA58DA076FAF5ABD104BB5A09454_terseLabel_en-US" xlink:label="lab_us-gaap_ConvertibleNotesPayableMember_924BDA58DA076FAF5ABD104BB5A09454" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Convertible Notes Payable</link:label>
    <link:label id="lab_us-gaap_ConvertibleNotesPayableMember_924BDA58DA076FAF5ABD104BB5A09454_label_en-US" xlink:label="lab_us-gaap_ConvertibleNotesPayableMember_924BDA58DA076FAF5ABD104BB5A09454" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Convertible Notes Payable [Member]</link:label>
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    <link:label id="lab_us-gaap_CommonStockMember_D64F639D944E606F0B6F104BB5A049B3_terseLabel_en-US" xlink:label="lab_us-gaap_CommonStockMember_D64F639D944E606F0B6F104BB5A049B3" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Common stock</link:label>
    <link:label id="lab_us-gaap_CommonStockMember_D64F639D944E606F0B6F104BB5A049B3_label_en-US" xlink:label="lab_us-gaap_CommonStockMember_D64F639D944E606F0B6F104BB5A049B3" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Common Stock [Member]</link:label>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_CommonStockMember" xlink:label="loc_us-gaap_CommonStockMember_D64F639D944E606F0B6F104BB5A049B3" xlink:type="locator" />
    <link:labelArc order="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_us-gaap_CommonStockMember_D64F639D944E606F0B6F104BB5A049B3" xlink:to="lab_us-gaap_CommonStockMember_D64F639D944E606F0B6F104BB5A049B3" xlink:type="arc" />
    <link:label id="lab_us-gaap_CorporateBondSecuritiesMember_86DE9A4500C0C8010132104BB5A071F8_terseLabel_en-US" xlink:label="lab_us-gaap_CorporateBondSecuritiesMember_86DE9A4500C0C8010132104BB5A071F8" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Corporate bonds</link:label>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_CorporateBondSecuritiesMember" xlink:label="loc_us-gaap_CorporateBondSecuritiesMember_86DE9A4500C0C8010132104BB5A071F8" xlink:type="locator" />
    <link:labelArc order="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_us-gaap_CorporateBondSecuritiesMember_86DE9A4500C0C8010132104BB5A071F8" xlink:to="lab_us-gaap_CorporateBondSecuritiesMember_86DE9A4500C0C8010132104BB5A071F8" xlink:type="arc" />
    <link:label id="lab_us-gaap_InvestmentTypeAxis_014CC590F5D95ED9170E104BB5B0EE6C_terseLabel_en-US" xlink:label="lab_us-gaap_InvestmentTypeAxis_014CC590F5D95ED9170E104BB5B0EE6C" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Investment Type [Axis]</link:label>
    <link:label id="lab_us-gaap_InvestmentTypeAxis_014CC590F5D95ED9170E104BB5B0EE6C_label_en-US" xlink:label="lab_us-gaap_InvestmentTypeAxis_014CC590F5D95ED9170E104BB5B0EE6C" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Investment Type [Axis]</link:label>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_InvestmentTypeAxis" xlink:label="loc_us-gaap_InvestmentTypeAxis_014CC590F5D95ED9170E104BB5B0EE6C" xlink:type="locator" />
    <link:labelArc order="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_us-gaap_InvestmentTypeAxis_014CC590F5D95ED9170E104BB5B0EE6C" xlink:to="lab_us-gaap_InvestmentTypeAxis_014CC590F5D95ED9170E104BB5B0EE6C" xlink:type="arc" />
    <link:label id="lab_us-gaap_InvestmentTypeCategorizationMember_EE17470E8119E634F382104BB5B0CB10_terseLabel_en-US" xlink:label="lab_us-gaap_InvestmentTypeCategorizationMember_EE17470E8119E634F382104BB5B0CB10" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Investments [Domain]</link:label>
    <link:label id="lab_us-gaap_InvestmentTypeCategorizationMember_EE17470E8119E634F382104BB5B0CB10_label_en-US" xlink:label="lab_us-gaap_InvestmentTypeCategorizationMember_EE17470E8119E634F382104BB5B0CB10" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Investments [Domain]</link:label>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_InvestmentTypeCategorizationMember" xlink:label="loc_us-gaap_InvestmentTypeCategorizationMember_EE17470E8119E634F382104BB5B0CB10" xlink:type="locator" />
    <link:labelArc order="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_us-gaap_InvestmentTypeCategorizationMember_EE17470E8119E634F382104BB5B0CB10" xlink:to="lab_us-gaap_InvestmentTypeCategorizationMember_EE17470E8119E634F382104BB5B0CB10" xlink:type="arc" />
    <link:label id="lab_us-gaap_LongtermDebtTypeAxis_EB5A10BF677859918E9E104BB5B02722_terseLabel_en-US" xlink:label="lab_us-gaap_LongtermDebtTypeAxis_EB5A10BF677859918E9E104BB5B02722" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Long-term Debt, Type [Axis]</link:label>
    <link:label id="lab_us-gaap_LongtermDebtTypeAxis_EB5A10BF677859918E9E104BB5B02722_label_en-US" xlink:label="lab_us-gaap_LongtermDebtTypeAxis_EB5A10BF677859918E9E104BB5B02722" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Long-term Debt, Type [Axis]</link:label>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_LongtermDebtTypeAxis" xlink:label="loc_us-gaap_LongtermDebtTypeAxis_EB5A10BF677859918E9E104BB5B02722" xlink:type="locator" />
    <link:labelArc order="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_us-gaap_LongtermDebtTypeAxis_EB5A10BF677859918E9E104BB5B02722" xlink:to="lab_us-gaap_LongtermDebtTypeAxis_EB5A10BF677859918E9E104BB5B02722" xlink:type="arc" />
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    <link:label id="lab_us-gaap_LongtermDebtTypeDomain_3A6366D2D4A973EC634F104BB5B01B64_label_en-US" xlink:label="lab_us-gaap_LongtermDebtTypeDomain_3A6366D2D4A973EC634F104BB5B01B64" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Long-term Debt, Type [Domain]</link:label>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_LongtermDebtTypeDomain" xlink:label="loc_us-gaap_LongtermDebtTypeDomain_3A6366D2D4A973EC634F104BB5B01B64" xlink:type="locator" />
    <link:labelArc order="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_us-gaap_LongtermDebtTypeDomain_3A6366D2D4A973EC634F104BB5B01B64" xlink:to="lab_us-gaap_LongtermDebtTypeDomain_3A6366D2D4A973EC634F104BB5B01B64" xlink:type="arc" />
    <link:label id="lab_us-gaap_ConvertibleDebtMember_BE369A8BF88F1A9819C6104BB5B096DF_terseLabel_en-US" xlink:label="lab_us-gaap_ConvertibleDebtMember_BE369A8BF88F1A9819C6104BB5B096DF" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Convertible Debt</link:label>
    <link:label id="lab_us-gaap_ConvertibleDebtMember_BE369A8BF88F1A9819C6104BB5B096DF_label_en-US" xlink:label="lab_us-gaap_ConvertibleDebtMember_BE369A8BF88F1A9819C6104BB5B096DF" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Convertible Debt [Member]</link:label>
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    <link:label id="lab_us-gaap_StatementClassOfStockAxis_B6DAAA4F937E85BB1B26104BB5B0B385_label_en-US" xlink:label="lab_us-gaap_StatementClassOfStockAxis_B6DAAA4F937E85BB1B26104BB5B0B385" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Class of Stock [Axis]</link:label>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_StatementClassOfStockAxis" xlink:label="loc_us-gaap_StatementClassOfStockAxis_B6DAAA4F937E85BB1B26104BB5B0B385" xlink:type="locator" />
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    <link:label id="lab_us-gaap_ClassOfStockDomain_B74D72180935469EDBD1104BB5B0D035_terseLabel_en-US" xlink:label="lab_us-gaap_ClassOfStockDomain_B74D72180935469EDBD1104BB5B0D035" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Class of Stock [Domain]</link:label>
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    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_ClassOfStockDomain" xlink:label="loc_us-gaap_ClassOfStockDomain_B74D72180935469EDBD1104BB5B0D035" xlink:type="locator" />
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    <link:label id="lab_selb_SeriesERedeemableConvertiblePreferredStockMember_DD8A1BCC8E1244A2AD57104BB5B0844D_verboseLabel_en-US" xlink:label="lab_selb_SeriesERedeemableConvertiblePreferredStockMember_DD8A1BCC8E1244A2AD57104BB5B0844D" xlink:role="http://www.xbrl.org/2003/role/verboseLabel" xlink:type="resource" xml:lang="en-US">Conversion of Series E Preferred</link:label>
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    <link:label id="lab_selb_SeriesERedeemableConvertiblePreferredStockMember_DD8A1BCC8E1244A2AD57104BB5B0844D_documentation_en-US" xlink:label="lab_selb_SeriesERedeemableConvertiblePreferredStockMember_DD8A1BCC8E1244A2AD57104BB5B0844D" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:type="resource" xml:lang="en-US">Represents information pertaining to series E redeemable convertible preferred stock.</link:label>
    <link:loc xlink:href="selb-20161231.xsd#selb_SeriesERedeemableConvertiblePreferredStockMember" xlink:label="loc_selb_SeriesERedeemableConvertiblePreferredStockMember_DD8A1BCC8E1244A2AD57104BB5B0844D" xlink:type="locator" />
    <link:labelArc order="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_selb_SeriesERedeemableConvertiblePreferredStockMember_DD8A1BCC8E1244A2AD57104BB5B0844D" xlink:to="lab_selb_SeriesERedeemableConvertiblePreferredStockMember_DD8A1BCC8E1244A2AD57104BB5B0844D" xlink:type="arc" />
    <link:label id="lab_selb_CashAndCashEquivalentsCollateralizedByGovernmentSecuritiesValueOfCollateralPercentOfFairValue_34160729165CF42DABF6104BB5B07540_terseLabel_en-US" xlink:label="lab_selb_CashAndCashEquivalentsCollateralizedByGovernmentSecuritiesValueOfCollateralPercentOfFairValue_34160729165CF42DABF6104BB5B07540" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Agreements collateralized by government securities (not less than) (as a percent)</link:label>
    <link:label id="lab_selb_CashAndCashEquivalentsCollateralizedByGovernmentSecuritiesValueOfCollateralPercentOfFairValue_34160729165CF42DABF6104BB5B07540_label_en-US" xlink:label="lab_selb_CashAndCashEquivalentsCollateralizedByGovernmentSecuritiesValueOfCollateralPercentOfFairValue_34160729165CF42DABF6104BB5B07540" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Cash And Cash Equivalents Collateralized By Government Securities, Value Of Collateral, Percent Of Fair Value</link:label>
    <link:label id="lab_selb_CashAndCashEquivalentsCollateralizedByGovernmentSecuritiesValueOfCollateralPercentOfFairValue_34160729165CF42DABF6104BB5B07540_documentation_en-US" xlink:label="lab_selb_CashAndCashEquivalentsCollateralizedByGovernmentSecuritiesValueOfCollateralPercentOfFairValue_34160729165CF42DABF6104BB5B07540" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:type="resource" xml:lang="en-US">Cash And Cash Equivalents Collateralized By Government Securities, Value Of Collateral, Percent Of Fair Value</link:label>
    <link:loc xlink:href="selb-20161231.xsd#selb_CashAndCashEquivalentsCollateralizedByGovernmentSecuritiesValueOfCollateralPercentOfFairValue" xlink:label="loc_selb_CashAndCashEquivalentsCollateralizedByGovernmentSecuritiesValueOfCollateralPercentOfFairValue_34160729165CF42DABF6104BB5B07540" xlink:type="locator" />
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    <link:label id="lab_selb_InvestmentsMaturityPeriod_B6658AE70FEBD4FF9A65104BB5B0080E_terseLabel_en-US" xlink:label="lab_selb_InvestmentsMaturityPeriod_B6658AE70FEBD4FF9A65104BB5B0080E" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Average maturity, term</link:label>
    <link:label id="lab_selb_InvestmentsMaturityPeriod_B6658AE70FEBD4FF9A65104BB5B0080E_label_en-US" xlink:label="lab_selb_InvestmentsMaturityPeriod_B6658AE70FEBD4FF9A65104BB5B0080E" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Investments Maturity Period</link:label>
    <link:label id="lab_selb_InvestmentsMaturityPeriod_B6658AE70FEBD4FF9A65104BB5B0080E_documentation_en-US" xlink:label="lab_selb_InvestmentsMaturityPeriod_B6658AE70FEBD4FF9A65104BB5B0080E" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:type="resource" xml:lang="en-US">Represents information pertaining to US treasury obligations in investments maturity period.</link:label>
    <link:loc xlink:href="selb-20161231.xsd#selb_InvestmentsMaturityPeriod" xlink:label="loc_selb_InvestmentsMaturityPeriod_B6658AE70FEBD4FF9A65104BB5B0080E" xlink:type="locator" />
    <link:labelArc order="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_selb_InvestmentsMaturityPeriod_B6658AE70FEBD4FF9A65104BB5B0080E" xlink:to="lab_selb_InvestmentsMaturityPeriod_B6658AE70FEBD4FF9A65104BB5B0080E" xlink:type="arc" />
    <link:label id="lab_us-gaap_ClassOfWarrantOrRightNumberOfSecuritiesCalledByWarrantsOrRights_0D1C95B517DBC27B467D104BB5B0816B_verboseLabel_en-US" xlink:label="lab_us-gaap_ClassOfWarrantOrRightNumberOfSecuritiesCalledByWarrantsOrRights_0D1C95B517DBC27B467D104BB5B0816B" xlink:role="http://www.xbrl.org/2003/role/verboseLabel" xlink:type="resource" xml:lang="en-US">Warrants issued for purchase of stock (in shares)</link:label>
    <link:label id="lab_us-gaap_ClassOfWarrantOrRightNumberOfSecuritiesCalledByWarrantsOrRights_0D1C95B517DBC27B467D104BB5B0816B_label_en-US" xlink:label="lab_us-gaap_ClassOfWarrantOrRightNumberOfSecuritiesCalledByWarrantsOrRights_0D1C95B517DBC27B467D104BB5B0816B" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Class of Warrant or Right, Number of Securities Called by Warrants or Rights</link:label>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_ClassOfWarrantOrRightNumberOfSecuritiesCalledByWarrantsOrRights" xlink:label="loc_us-gaap_ClassOfWarrantOrRightNumberOfSecuritiesCalledByWarrantsOrRights_0D1C95B517DBC27B467D104BB5B0816B" xlink:type="locator" />
    <link:labelArc order="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_us-gaap_ClassOfWarrantOrRightNumberOfSecuritiesCalledByWarrantsOrRights_0D1C95B517DBC27B467D104BB5B0816B" xlink:to="lab_us-gaap_ClassOfWarrantOrRightNumberOfSecuritiesCalledByWarrantsOrRights_0D1C95B517DBC27B467D104BB5B0816B" xlink:type="arc" />
    <link:label id="lab_selb_ClassOfWarrantsOrRightsTerm_D2D73E7F28A5E69DB157104BB5B018CA_terseLabel_en-US" xlink:label="lab_selb_ClassOfWarrantsOrRightsTerm_D2D73E7F28A5E69DB157104BB5B018CA" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Expiration period of warrants</link:label>
    <link:label id="lab_selb_ClassOfWarrantsOrRightsTerm_D2D73E7F28A5E69DB157104BB5B018CA_label_en-US" xlink:label="lab_selb_ClassOfWarrantsOrRightsTerm_D2D73E7F28A5E69DB157104BB5B018CA" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Class Of Warrants Or Rights, Term</link:label>
    <link:label id="lab_selb_ClassOfWarrantsOrRightsTerm_D2D73E7F28A5E69DB157104BB5B018CA_documentation_en-US" xlink:label="lab_selb_ClassOfWarrantsOrRightsTerm_D2D73E7F28A5E69DB157104BB5B018CA" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:type="resource" xml:lang="en-US">Period of time between issuance and maturity of warrant, in PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.</link:label>
    <link:loc xlink:href="selb-20161231.xsd#selb_ClassOfWarrantsOrRightsTerm" xlink:label="loc_selb_ClassOfWarrantsOrRightsTerm_D2D73E7F28A5E69DB157104BB5B018CA" xlink:type="locator" />
    <link:labelArc order="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_selb_ClassOfWarrantsOrRightsTerm_D2D73E7F28A5E69DB157104BB5B018CA" xlink:to="lab_selb_ClassOfWarrantsOrRightsTerm_D2D73E7F28A5E69DB157104BB5B018CA" xlink:type="arc" />
    <link:label id="lab_us-gaap_ClassOfWarrantOrRightExercisePriceOfWarrantsOrRights1_8A904A3ED6FEB479AF4A104BB5B0B1FA_terseLabel_en-US" xlink:label="lab_us-gaap_ClassOfWarrantOrRightExercisePriceOfWarrantsOrRights1_8A904A3ED6FEB479AF4A104BB5B0B1FA" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Exercise price (in dollars per share)</link:label>
    <link:label id="lab_us-gaap_ClassOfWarrantOrRightExercisePriceOfWarrantsOrRights1_8A904A3ED6FEB479AF4A104BB5B0B1FA_label_en-US" xlink:label="lab_us-gaap_ClassOfWarrantOrRightExercisePriceOfWarrantsOrRights1_8A904A3ED6FEB479AF4A104BB5B0B1FA" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Class of Warrant or Right, Exercise Price of Warrants or Rights</link:label>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_ClassOfWarrantOrRightExercisePriceOfWarrantsOrRights1" xlink:label="loc_us-gaap_ClassOfWarrantOrRightExercisePriceOfWarrantsOrRights1_8A904A3ED6FEB479AF4A104BB5B0B1FA" xlink:type="locator" />
    <link:labelArc order="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_us-gaap_ClassOfWarrantOrRightExercisePriceOfWarrantsOrRights1_8A904A3ED6FEB479AF4A104BB5B0B1FA" xlink:to="lab_us-gaap_ClassOfWarrantOrRightExercisePriceOfWarrantsOrRights1_8A904A3ED6FEB479AF4A104BB5B0B1FA" xlink:type="arc" />
    <link:label id="lab_selb_NumberOfWarrantsExercisedToPurchaseCommonStock_0ABAC93633237808A12A104BB5B0EDE5_terseLabel_en-US" xlink:label="lab_selb_NumberOfWarrantsExercisedToPurchaseCommonStock_0ABAC93633237808A12A104BB5B0EDE5" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Number of warrants exercised to purchase common stock (in shares)</link:label>
    <link:label id="lab_selb_NumberOfWarrantsExercisedToPurchaseCommonStock_0ABAC93633237808A12A104BB5B0EDE5_label_en-US" xlink:label="lab_selb_NumberOfWarrantsExercisedToPurchaseCommonStock_0ABAC93633237808A12A104BB5B0EDE5" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Number Of Warrants Exercised To Purchase Common Stock</link:label>
    <link:label id="lab_selb_NumberOfWarrantsExercisedToPurchaseCommonStock_0ABAC93633237808A12A104BB5B0EDE5_documentation_en-US" xlink:label="lab_selb_NumberOfWarrantsExercisedToPurchaseCommonStock_0ABAC93633237808A12A104BB5B0EDE5" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:type="resource" xml:lang="en-US">Number Of Warrants Exercised To Purchase Common Stock</link:label>
    <link:loc xlink:href="selb-20161231.xsd#selb_NumberOfWarrantsExercisedToPurchaseCommonStock" xlink:label="loc_selb_NumberOfWarrantsExercisedToPurchaseCommonStock_0ABAC93633237808A12A104BB5B0EDE5" xlink:type="locator" />
    <link:labelArc order="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_selb_NumberOfWarrantsExercisedToPurchaseCommonStock_0ABAC93633237808A12A104BB5B0EDE5" xlink:to="lab_selb_NumberOfWarrantsExercisedToPurchaseCommonStock_0ABAC93633237808A12A104BB5B0EDE5" xlink:type="arc" />
    <link:label id="lab_selb_StockIssuedDuringPeriodSharesCommonStockIssuedUponExerciseOfWarrants_E17802869C5496CC45C6104BB5B02D63_terseLabel_en-US" xlink:label="lab_selb_StockIssuedDuringPeriodSharesCommonStockIssuedUponExerciseOfWarrants_E17802869C5496CC45C6104BB5B02D63" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Net shares of common stock issued (in shares)</link:label>
    <link:label id="lab_selb_StockIssuedDuringPeriodSharesCommonStockIssuedUponExerciseOfWarrants_E17802869C5496CC45C6104BB5B02D63_label_en-US" xlink:label="lab_selb_StockIssuedDuringPeriodSharesCommonStockIssuedUponExerciseOfWarrants_E17802869C5496CC45C6104BB5B02D63" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Stock Issued During Period, Shares, Common Stock Issued Upon Exercise Of Warrants</link:label>
    <link:label id="lab_selb_StockIssuedDuringPeriodSharesCommonStockIssuedUponExerciseOfWarrants_E17802869C5496CC45C6104BB5B02D63_documentation_en-US" xlink:label="lab_selb_StockIssuedDuringPeriodSharesCommonStockIssuedUponExerciseOfWarrants_E17802869C5496CC45C6104BB5B02D63" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:type="resource" xml:lang="en-US">Stock Issued During Period, Shares, Common Stock Issued Upon Exercise Of Warrants</link:label>
    <link:loc xlink:href="selb-20161231.xsd#selb_StockIssuedDuringPeriodSharesCommonStockIssuedUponExerciseOfWarrants" xlink:label="loc_selb_StockIssuedDuringPeriodSharesCommonStockIssuedUponExerciseOfWarrants_E17802869C5496CC45C6104BB5B02D63" xlink:type="locator" />
    <link:labelArc order="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_selb_StockIssuedDuringPeriodSharesCommonStockIssuedUponExerciseOfWarrants_E17802869C5496CC45C6104BB5B02D63" xlink:to="lab_selb_StockIssuedDuringPeriodSharesCommonStockIssuedUponExerciseOfWarrants_E17802869C5496CC45C6104BB5B02D63" xlink:type="arc" />
    <link:label id="lab_us-gaap_EarningsPerShareAbstract_63C995577072A79D4FE301FAAA6A6509_label_en-US" xlink:label="lab_us-gaap_EarningsPerShareAbstract_63C995577072A79D4FE301FAAA6A6509" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Earnings Per Share [Abstract]</link:label>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_EarningsPerShareAbstract" xlink:label="loc_us-gaap_EarningsPerShareAbstract_63C995577072A79D4FE301FAAA6A6509" xlink:type="locator" />
    <link:labelArc order="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_us-gaap_EarningsPerShareAbstract_63C995577072A79D4FE301FAAA6A6509" xlink:to="lab_us-gaap_EarningsPerShareAbstract_63C995577072A79D4FE301FAAA6A6509" xlink:type="arc" />
    <link:label id="lab_us-gaap_NetIncomeLossAvailableToCommonStockholdersBasicAbstract_05DD31117E6EC0A879E601FAAA6BD3AB_terseLabel_en-US" xlink:label="lab_us-gaap_NetIncomeLossAvailableToCommonStockholdersBasicAbstract_05DD31117E6EC0A879E601FAAA6BD3AB" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Numerator:</link:label>
    <link:label id="lab_us-gaap_NetIncomeLossAvailableToCommonStockholdersBasicAbstract_05DD31117E6EC0A879E601FAAA6BD3AB_label_en-US" xlink:label="lab_us-gaap_NetIncomeLossAvailableToCommonStockholdersBasicAbstract_05DD31117E6EC0A879E601FAAA6BD3AB" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Net Income (Loss) Available to Common Stockholders, Basic [Abstract]</link:label>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_NetIncomeLossAvailableToCommonStockholdersBasicAbstract" xlink:label="loc_us-gaap_NetIncomeLossAvailableToCommonStockholdersBasicAbstract_05DD31117E6EC0A879E601FAAA6BD3AB" xlink:type="locator" />
    <link:labelArc order="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_us-gaap_NetIncomeLossAvailableToCommonStockholdersBasicAbstract_05DD31117E6EC0A879E601FAAA6BD3AB" xlink:to="lab_us-gaap_NetIncomeLossAvailableToCommonStockholdersBasicAbstract_05DD31117E6EC0A879E601FAAA6BD3AB" xlink:type="arc" />
    <link:label id="lab_us-gaap_NetIncomeLoss_32F813249B328106926801FAAA6BEA23_terseLabel_en-US" xlink:label="lab_us-gaap_NetIncomeLoss_32F813249B328106926801FAAA6BEA23" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Net loss</link:label>
    <link:label id="lab_us-gaap_NetIncomeLoss_32F813249B328106926801FAAA6BEA23_label_en-US" xlink:label="lab_us-gaap_NetIncomeLoss_32F813249B328106926801FAAA6BEA23" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Net Income (Loss) Attributable to Parent</link:label>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_NetIncomeLoss" xlink:label="loc_us-gaap_NetIncomeLoss_32F813249B328106926801FAAA6BEA23" xlink:type="locator" />
    <link:labelArc order="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_us-gaap_NetIncomeLoss_32F813249B328106926801FAAA6BEA23" xlink:to="lab_us-gaap_NetIncomeLoss_32F813249B328106926801FAAA6BEA23" xlink:type="arc" />
    <link:label id="lab_us-gaap_TemporaryEquityAccretionToRedemptionValueAdjustment_B92A8D2F7FE60C8B384E01FAAA6BCDC4_negatedTerseLabel_en-US" xlink:label="lab_us-gaap_TemporaryEquityAccretionToRedemptionValueAdjustment_B92A8D2F7FE60C8B384E01FAAA6BCDC4" xlink:role="http://www.xbrl.org/2009/role/negatedTerseLabel" xlink:type="resource" xml:lang="en-US">Less: accretion on preferred stock</link:label>
    <link:label id="lab_us-gaap_TemporaryEquityAccretionToRedemptionValueAdjustment_B92A8D2F7FE60C8B384E01FAAA6BCDC4_label_en-US" xlink:label="lab_us-gaap_TemporaryEquityAccretionToRedemptionValueAdjustment_B92A8D2F7FE60C8B384E01FAAA6BCDC4" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Temporary Equity, Accretion to Redemption Value, Adjustment</link:label>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_TemporaryEquityAccretionToRedemptionValueAdjustment" xlink:label="loc_us-gaap_TemporaryEquityAccretionToRedemptionValueAdjustment_B92A8D2F7FE60C8B384E01FAAA6BCDC4" xlink:type="locator" />
    <link:labelArc order="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_us-gaap_TemporaryEquityAccretionToRedemptionValueAdjustment_B92A8D2F7FE60C8B384E01FAAA6BCDC4" xlink:to="lab_us-gaap_TemporaryEquityAccretionToRedemptionValueAdjustment_B92A8D2F7FE60C8B384E01FAAA6BCDC4" xlink:type="arc" />
    <link:label id="lab_us-gaap_PreferredStockRedemptionDiscount_A4D077F7CA9E97C84C0F01FAAA6B1BB2_terseLabel_en-US" xlink:label="lab_us-gaap_PreferredStockRedemptionDiscount_A4D077F7CA9E97C84C0F01FAAA6B1BB2" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Net effect of extinguishment of Series SRN redeemable convertible preferred stock</link:label>
    <link:label id="lab_us-gaap_PreferredStockRedemptionDiscount_A4D077F7CA9E97C84C0F01FAAA6B1BB2_label_en-US" xlink:label="lab_us-gaap_PreferredStockRedemptionDiscount_A4D077F7CA9E97C84C0F01FAAA6B1BB2" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Preferred Stock Redemption Discount</link:label>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_PreferredStockRedemptionDiscount" xlink:label="loc_us-gaap_PreferredStockRedemptionDiscount_A4D077F7CA9E97C84C0F01FAAA6B1BB2" xlink:type="locator" />
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    <link:label id="lab_selb_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsWeightedAverageFairValue_4E3072CA9D056ADF67CBF77125D45613_terseLabel_en-US" xlink:label="lab_selb_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsWeightedAverageFairValue_4E3072CA9D056ADF67CBF77125D45613" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Weighted-average fair value of common stock (in dollars per share)</link:label>
    <link:label id="lab_selb_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsWeightedAverageFairValue_4E3072CA9D056ADF67CBF77125D45613_label_en-US" xlink:label="lab_selb_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsWeightedAverageFairValue_4E3072CA9D056ADF67CBF77125D45613" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Share-based Compensation Arrangement by Share-based Payment Award, Fair Value Assumptions, Weighted Average Fair Value</link:label>
    <link:label id="lab_selb_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsWeightedAverageFairValue_4E3072CA9D056ADF67CBF77125D45613_documentation_en-US" xlink:label="lab_selb_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsWeightedAverageFairValue_4E3072CA9D056ADF67CBF77125D45613" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:type="resource" xml:lang="en-US">Weighed-average fair value relating to the share-based payment award.</link:label>
    <link:loc xlink:href="selb-20161231.xsd#selb_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsWeightedAverageFairValue" xlink:label="loc_selb_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsWeightedAverageFairValue_4E3072CA9D056ADF67CBF77125D45613" xlink:type="locator" />
    <link:labelArc order="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_selb_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsWeightedAverageFairValue_4E3072CA9D056ADF67CBF77125D45613" xlink:to="lab_selb_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsWeightedAverageFairValue_4E3072CA9D056ADF67CBF77125D45613" xlink:type="arc" />
    <link:label id="lab_us-gaap_DebtDisclosureAbstract_58AA0DDE5319ABCCC078104BB581C8CF_label_en-US" xlink:label="lab_us-gaap_DebtDisclosureAbstract_58AA0DDE5319ABCCC078104BB581C8CF" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Debt Disclosure [Abstract]</link:label>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_DebtDisclosureAbstract" xlink:label="loc_us-gaap_DebtDisclosureAbstract_58AA0DDE5319ABCCC078104BB581C8CF" xlink:type="locator" />
    <link:labelArc order="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_us-gaap_DebtDisclosureAbstract_58AA0DDE5319ABCCC078104BB581C8CF" xlink:to="lab_us-gaap_DebtDisclosureAbstract_58AA0DDE5319ABCCC078104BB581C8CF" xlink:type="arc" />
    <link:label id="lab_us-gaap_LineOfCreditFacilityTable_EFE1F88E9AD6EAF75862104BB581034B_terseLabel_en-US" xlink:label="lab_us-gaap_LineOfCreditFacilityTable_EFE1F88E9AD6EAF75862104BB581034B" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Line of Credit Facility [Table]</link:label>
    <link:label id="lab_us-gaap_LineOfCreditFacilityTable_EFE1F88E9AD6EAF75862104BB581034B_label_en-US" xlink:label="lab_us-gaap_LineOfCreditFacilityTable_EFE1F88E9AD6EAF75862104BB581034B" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Line of Credit Facility [Table]</link:label>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_LineOfCreditFacilityTable" xlink:label="loc_us-gaap_LineOfCreditFacilityTable_EFE1F88E9AD6EAF75862104BB581034B" xlink:type="locator" />
    <link:labelArc order="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_us-gaap_LineOfCreditFacilityTable_EFE1F88E9AD6EAF75862104BB581034B" xlink:to="lab_us-gaap_LineOfCreditFacilityTable_EFE1F88E9AD6EAF75862104BB581034B" xlink:type="arc" />
    <link:label id="lab_selb_TermLoanMember_63C37903C4C53007C0B6104BB58179F1_verboseLabel_en-US" xlink:label="lab_selb_TermLoanMember_63C37903C4C53007C0B6104BB58179F1" xlink:role="http://www.xbrl.org/2003/role/verboseLabel" xlink:type="resource" xml:lang="en-US">Term Loans</link:label>
    <link:loc xlink:href="selb-20161231.xsd#selb_TermLoanMember" xlink:label="loc_selb_TermLoanMember_63C37903C4C53007C0B6104BB58179F1" xlink:type="locator" />
    <link:labelArc order="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_selb_TermLoanMember_63C37903C4C53007C0B6104BB58179F1" xlink:to="lab_selb_TermLoanMember_63C37903C4C53007C0B6104BB58179F1" xlink:type="arc" />
    <link:label id="lab_selb_DebtCovenantPeriodAxis_17B0FEC5D6ADD9F649D3104BB581F642_terseLabel_en-US" xlink:label="lab_selb_DebtCovenantPeriodAxis_17B0FEC5D6ADD9F649D3104BB581F642" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Debt Covenant Period [Axis]</link:label>
    <link:label id="lab_selb_DebtCovenantPeriodAxis_17B0FEC5D6ADD9F649D3104BB581F642_label_en-US" xlink:label="lab_selb_DebtCovenantPeriodAxis_17B0FEC5D6ADD9F649D3104BB581F642" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Debt Covenant Period [Axis]</link:label>
    <link:label id="lab_selb_DebtCovenantPeriodAxis_17B0FEC5D6ADD9F649D3104BB581F642_documentation_en-US" xlink:label="lab_selb_DebtCovenantPeriodAxis_17B0FEC5D6ADD9F649D3104BB581F642" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:type="resource" xml:lang="en-US">Debt Covenant Period [Axis]</link:label>
    <link:loc xlink:href="selb-20161231.xsd#selb_DebtCovenantPeriodAxis" xlink:label="loc_selb_DebtCovenantPeriodAxis_17B0FEC5D6ADD9F649D3104BB581F642" xlink:type="locator" />
    <link:labelArc order="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_selb_DebtCovenantPeriodAxis_17B0FEC5D6ADD9F649D3104BB581F642" xlink:to="lab_selb_DebtCovenantPeriodAxis_17B0FEC5D6ADD9F649D3104BB581F642" xlink:type="arc" />
    <link:label id="lab_selb_DebtCovenantPeriodDomain_CF936ECDD5CCC4542A63104BB581E905_terseLabel_en-US" xlink:label="lab_selb_DebtCovenantPeriodDomain_CF936ECDD5CCC4542A63104BB581E905" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Debt Covenant Period [Domain]</link:label>
    <link:label id="lab_selb_DebtCovenantPeriodDomain_CF936ECDD5CCC4542A63104BB581E905_label_en-US" xlink:label="lab_selb_DebtCovenantPeriodDomain_CF936ECDD5CCC4542A63104BB581E905" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Debt Covenant Period [Domain]</link:label>
    <link:label id="lab_selb_DebtCovenantPeriodDomain_CF936ECDD5CCC4542A63104BB581E905_documentation_en-US" xlink:label="lab_selb_DebtCovenantPeriodDomain_CF936ECDD5CCC4542A63104BB581E905" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:type="resource" xml:lang="en-US">[Domain] for Debt Covenant Period [Axis]</link:label>
    <link:loc xlink:href="selb-20161231.xsd#selb_DebtCovenantPeriodDomain" xlink:label="loc_selb_DebtCovenantPeriodDomain_CF936ECDD5CCC4542A63104BB581E905" xlink:type="locator" />
    <link:labelArc order="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_selb_DebtCovenantPeriodDomain_CF936ECDD5CCC4542A63104BB581E905" xlink:to="lab_selb_DebtCovenantPeriodDomain_CF936ECDD5CCC4542A63104BB581E905" xlink:type="arc" />
    <link:label id="lab_selb_TermLoanPrepaidPriorToFirstAnniversaryMember_78DB60F88DCA827D2E86104BB5816FDB_terseLabel_en-US" xlink:label="lab_selb_TermLoanPrepaidPriorToFirstAnniversaryMember_78DB60F88DCA827D2E86104BB5816FDB" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Prepaid prior to first anniversary</link:label>
    <link:label id="lab_selb_TermLoanPrepaidPriorToFirstAnniversaryMember_78DB60F88DCA827D2E86104BB5816FDB_label_en-US" xlink:label="lab_selb_TermLoanPrepaidPriorToFirstAnniversaryMember_78DB60F88DCA827D2E86104BB5816FDB" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Term Loan Prepaid Prior To First Anniversary [Member]</link:label>
    <link:label id="lab_selb_TermLoanPrepaidPriorToFirstAnniversaryMember_78DB60F88DCA827D2E86104BB5816FDB_documentation_en-US" xlink:label="lab_selb_TermLoanPrepaidPriorToFirstAnniversaryMember_78DB60F88DCA827D2E86104BB5816FDB" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:type="resource" xml:lang="en-US">Represents information pertaining to prepayment of term loan prior to first anniversary.</link:label>
    <link:loc xlink:href="selb-20161231.xsd#selb_TermLoanPrepaidPriorToFirstAnniversaryMember" xlink:label="loc_selb_TermLoanPrepaidPriorToFirstAnniversaryMember_78DB60F88DCA827D2E86104BB5816FDB" xlink:type="locator" />
    <link:labelArc order="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_selb_TermLoanPrepaidPriorToFirstAnniversaryMember_78DB60F88DCA827D2E86104BB5816FDB" xlink:to="lab_selb_TermLoanPrepaidPriorToFirstAnniversaryMember_78DB60F88DCA827D2E86104BB5816FDB" xlink:type="arc" />
    <link:label id="lab_selb_TermLoanPrepaidAfterFirstAnniversaryButBeforeSecondAnniversaryMember_2B6A455B2613CC0F6BB7104BB5818455_terseLabel_en-US" xlink:label="lab_selb_TermLoanPrepaidAfterFirstAnniversaryButBeforeSecondAnniversaryMember_2B6A455B2613CC0F6BB7104BB5818455" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Prepaid prior to first anniversary but before second</link:label>
    <link:label id="lab_selb_TermLoanPrepaidAfterFirstAnniversaryButBeforeSecondAnniversaryMember_2B6A455B2613CC0F6BB7104BB5818455_label_en-US" xlink:label="lab_selb_TermLoanPrepaidAfterFirstAnniversaryButBeforeSecondAnniversaryMember_2B6A455B2613CC0F6BB7104BB5818455" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Term Loan Prepaid After First Anniversary But Before Second Anniversary [Member]</link:label>
    <link:label id="lab_selb_TermLoanPrepaidAfterFirstAnniversaryButBeforeSecondAnniversaryMember_2B6A455B2613CC0F6BB7104BB5818455_documentation_en-US" xlink:label="lab_selb_TermLoanPrepaidAfterFirstAnniversaryButBeforeSecondAnniversaryMember_2B6A455B2613CC0F6BB7104BB5818455" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:type="resource" xml:lang="en-US">Represents information pertaining to prepayment of term loan after first anniversary but prior to second anniversary.</link:label>
    <link:loc xlink:href="selb-20161231.xsd#selb_TermLoanPrepaidAfterFirstAnniversaryButBeforeSecondAnniversaryMember" xlink:label="loc_selb_TermLoanPrepaidAfterFirstAnniversaryButBeforeSecondAnniversaryMember_2B6A455B2613CC0F6BB7104BB5818455" xlink:type="locator" />
    <link:labelArc order="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_selb_TermLoanPrepaidAfterFirstAnniversaryButBeforeSecondAnniversaryMember_2B6A455B2613CC0F6BB7104BB5818455" xlink:to="lab_selb_TermLoanPrepaidAfterFirstAnniversaryButBeforeSecondAnniversaryMember_2B6A455B2613CC0F6BB7104BB5818455" xlink:type="arc" />
    <link:label id="lab_selb_TermLoanPrepaidAfterSecondAnniversaryMember_CBD6AF931BCF267F0B9E104BB581B88E_terseLabel_en-US" xlink:label="lab_selb_TermLoanPrepaidAfterSecondAnniversaryMember_CBD6AF931BCF267F0B9E104BB581B88E" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Prepaid after second anniversary</link:label>
    <link:label id="lab_selb_TermLoanPrepaidAfterSecondAnniversaryMember_CBD6AF931BCF267F0B9E104BB581B88E_label_en-US" xlink:label="lab_selb_TermLoanPrepaidAfterSecondAnniversaryMember_CBD6AF931BCF267F0B9E104BB581B88E" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Term Loan Prepaid After Second Anniversary [Member]</link:label>
    <link:label id="lab_selb_TermLoanPrepaidAfterSecondAnniversaryMember_CBD6AF931BCF267F0B9E104BB581B88E_documentation_en-US" xlink:label="lab_selb_TermLoanPrepaidAfterSecondAnniversaryMember_CBD6AF931BCF267F0B9E104BB581B88E" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:type="resource" xml:lang="en-US">Represents information pertaining to prepayment of term loan after second anniversary.</link:label>
    <link:loc xlink:href="selb-20161231.xsd#selb_TermLoanPrepaidAfterSecondAnniversaryMember" xlink:label="loc_selb_TermLoanPrepaidAfterSecondAnniversaryMember_CBD6AF931BCF267F0B9E104BB581B88E" xlink:type="locator" />
    <link:labelArc order="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_selb_TermLoanPrepaidAfterSecondAnniversaryMember_CBD6AF931BCF267F0B9E104BB581B88E" xlink:to="lab_selb_TermLoanPrepaidAfterSecondAnniversaryMember_CBD6AF931BCF267F0B9E104BB581B88E" xlink:type="arc" />
    <link:label id="lab_us-gaap_LineOfCreditFacilityLineItems_4C4748669DA29DF6B089104BB581DDB7_terseLabel_en-US" xlink:label="lab_us-gaap_LineOfCreditFacilityLineItems_4C4748669DA29DF6B089104BB581DDB7" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Line of Credit Facility [Line Items]</link:label>
    <link:label id="lab_us-gaap_LineOfCreditFacilityLineItems_4C4748669DA29DF6B089104BB581DDB7_label_en-US" xlink:label="lab_us-gaap_LineOfCreditFacilityLineItems_4C4748669DA29DF6B089104BB581DDB7" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Line of Credit Facility [Line Items]</link:label>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_LineOfCreditFacilityLineItems" xlink:label="loc_us-gaap_LineOfCreditFacilityLineItems_4C4748669DA29DF6B089104BB581DDB7" xlink:type="locator" />
    <link:labelArc order="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_us-gaap_LineOfCreditFacilityLineItems_4C4748669DA29DF6B089104BB581DDB7" xlink:to="lab_us-gaap_LineOfCreditFacilityLineItems_4C4748669DA29DF6B089104BB581DDB7" xlink:type="arc" />
    <link:label id="lab_selb_NumberOfLenders_F071AB340ABF22EB2D73104BB5810E0E_terseLabel_en-US" xlink:label="lab_selb_NumberOfLenders_F071AB340ABF22EB2D73104BB5810E0E" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Number of lenders</link:label>
    <link:label id="lab_selb_NumberOfLenders_F071AB340ABF22EB2D73104BB5810E0E_label_en-US" xlink:label="lab_selb_NumberOfLenders_F071AB340ABF22EB2D73104BB5810E0E" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Number Of Lenders</link:label>
    <link:label id="lab_selb_NumberOfLenders_F071AB340ABF22EB2D73104BB5810E0E_documentation_en-US" xlink:label="lab_selb_NumberOfLenders_F071AB340ABF22EB2D73104BB5810E0E" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:type="resource" xml:lang="en-US">Represents the number of lenders.</link:label>
    <link:loc xlink:href="selb-20161231.xsd#selb_NumberOfLenders" xlink:label="loc_selb_NumberOfLenders_F071AB340ABF22EB2D73104BB5810E0E" xlink:type="locator" />
    <link:labelArc order="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_selb_NumberOfLenders_F071AB340ABF22EB2D73104BB5810E0E" xlink:to="lab_selb_NumberOfLenders_F071AB340ABF22EB2D73104BB5810E0E" xlink:type="arc" />
    <link:label id="lab_us-gaap_LineOfCreditFacilityMaximumBorrowingCapacity_35DBD09DDCE77D20BED1104BB581BA4F_verboseLabel_en-US" xlink:label="lab_us-gaap_LineOfCreditFacilityMaximumBorrowingCapacity_35DBD09DDCE77D20BED1104BB581BA4F" xlink:role="http://www.xbrl.org/2003/role/verboseLabel" xlink:type="resource" xml:lang="en-US">Borrowing capacity</link:label>
    <link:label id="lab_us-gaap_LineOfCreditFacilityMaximumBorrowingCapacity_35DBD09DDCE77D20BED1104BB581BA4F_label_en-US" xlink:label="lab_us-gaap_LineOfCreditFacilityMaximumBorrowingCapacity_35DBD09DDCE77D20BED1104BB581BA4F" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Line of Credit Facility, Maximum Borrowing Capacity</link:label>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_LineOfCreditFacilityMaximumBorrowingCapacity" xlink:label="loc_us-gaap_LineOfCreditFacilityMaximumBorrowingCapacity_35DBD09DDCE77D20BED1104BB581BA4F" xlink:type="locator" />
    <link:labelArc order="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_us-gaap_LineOfCreditFacilityMaximumBorrowingCapacity_35DBD09DDCE77D20BED1104BB581BA4F" xlink:to="lab_us-gaap_LineOfCreditFacilityMaximumBorrowingCapacity_35DBD09DDCE77D20BED1104BB581BA4F" xlink:type="arc" />
    <link:label id="lab_us-gaap_ProceedsFromLinesOfCredit_E3078ABFD72053A6D083104BB5816A34_verboseLabel_en-US" xlink:label="lab_us-gaap_ProceedsFromLinesOfCredit_E3078ABFD72053A6D083104BB5816A34" xlink:role="http://www.xbrl.org/2003/role/verboseLabel" xlink:type="resource" xml:lang="en-US">Borrowings on loan and security agreement</link:label>
    <link:label id="lab_us-gaap_ProceedsFromLinesOfCredit_E3078ABFD72053A6D083104BB5816A34_label_en-US" xlink:label="lab_us-gaap_ProceedsFromLinesOfCredit_E3078ABFD72053A6D083104BB5816A34" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Proceeds from Lines of Credit</link:label>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_ProceedsFromLinesOfCredit" xlink:label="loc_us-gaap_ProceedsFromLinesOfCredit_E3078ABFD72053A6D083104BB5816A34" xlink:type="locator" />
    <link:labelArc order="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_us-gaap_ProceedsFromLinesOfCredit_E3078ABFD72053A6D083104BB5816A34" xlink:to="lab_us-gaap_ProceedsFromLinesOfCredit_E3078ABFD72053A6D083104BB5816A34" xlink:type="arc" />
    <link:label id="lab_us-gaap_LineOfCredit_042A98F94B45A42F41E6104BB58129A9_terseLabel_en-US" xlink:label="lab_us-gaap_LineOfCredit_042A98F94B45A42F41E6104BB58129A9" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Outstanding principal balance under Term Loans</link:label>
    <link:label id="lab_us-gaap_LineOfCredit_042A98F94B45A42F41E6104BB58129A9_label_en-US" xlink:label="lab_us-gaap_LineOfCredit_042A98F94B45A42F41E6104BB58129A9" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Long-term Line of Credit</link:label>
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    <link:label id="lab_selb_WarrantsGrantDateFairValue_DE6386E59FF8FEDA34B9104BB581A00A_documentation_en-US" xlink:label="lab_selb_WarrantsGrantDateFairValue_DE6386E59FF8FEDA34B9104BB581A00A" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:type="resource" xml:lang="en-US">Represents the initial grant date fair value of the warrants.</link:label>
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    <link:label id="lab_us-gaap_RedeemableConvertiblePreferredStockMember_11CDD9790598E73D420401D9534DCE48_terseLabel_en-US" xlink:label="lab_us-gaap_RedeemableConvertiblePreferredStockMember_11CDD9790598E73D420401D9534DCE48" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Redeemable convertible preferred stock</link:label>
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    <link:loc xlink:href="selb-20161231.xsd#selb_AccruedLegalFeesCurrent" xlink:label="loc_selb_AccruedLegalFeesCurrent_C2B4ECA976734CABB24201D953245105" xlink:type="locator" />
    <link:labelArc order="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_selb_AccruedLegalFeesCurrent_C2B4ECA976734CABB24201D953245105" xlink:to="lab_selb_AccruedLegalFeesCurrent_C2B4ECA976734CABB24201D953245105" xlink:type="arc" />
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    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriodGross" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriodGross_891E803F1D329521BFAFF673C00E93A0" xlink:type="locator" />
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    <link:label id="lab_us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsVestedNumberOfShares_E81F4E78382FFEE778F4F673C00E2087_label_en-US" xlink:label="lab_us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsVestedNumberOfShares_E81F4E78382FFEE778F4F673C00E2087" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Share-based Compensation Arrangement by Share-based Payment Award, Options, Vested, Number of Shares</link:label>
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    <link:label id="lab_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsVestedAndExpectedToVestOutstandingNumber_6658B910FA434DB84BF9F673C00E2352_verboseLabel_en-US" xlink:label="lab_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsVestedAndExpectedToVestOutstandingNumber_6658B910FA434DB84BF9F673C00E2352" xlink:role="http://www.xbrl.org/2003/role/verboseLabel" xlink:type="resource" xml:lang="en-US">Vested and expected to vest (in shares)</link:label>
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    <link:label id="lab_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingWeightedAverageExercisePriceRollforward_65E9D3D7AEFAE5AD8615F673C00E200B_label_en-US" xlink:label="lab_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingWeightedAverageExercisePriceRollforward_65E9D3D7AEFAE5AD8615F673C00E200B" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Weighted Average Exercise Price [Abstract]</link:label>
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    <link:label id="lab_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingWeightedAverageExercisePrice_89CCFB1BD6D9EF1323ADF673C00EE6D3_periodStartLabel_en-US" xlink:label="lab_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingWeightedAverageExercisePrice_89CCFB1BD6D9EF1323ADF673C00EE6D3" xlink:role="http://www.xbrl.org/2003/role/periodStartLabel" xlink:type="resource" xml:lang="en-US">Beginning balance (in dollars per share)</link:label>
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    <link:label id="lab_selb_ShareBasedCompensationArrangementByShareBasedPaymentAwardVotingRightsOfCommonStockHoldingPercentage_D0C0E39ABD872F313B61F673C0187788_terseLabel_en-US" xlink:label="lab_selb_ShareBasedCompensationArrangementByShareBasedPaymentAwardVotingRightsOfCommonStockHoldingPercentage_D0C0E39ABD872F313B61F673C0187788" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Combined voting power of participants (as a percent)</link:label>
    <link:label id="lab_selb_ShareBasedCompensationArrangementByShareBasedPaymentAwardVotingRightsOfCommonStockHoldingPercentage_D0C0E39ABD872F313B61F673C0187788_label_en-US" xlink:label="lab_selb_ShareBasedCompensationArrangementByShareBasedPaymentAwardVotingRightsOfCommonStockHoldingPercentage_D0C0E39ABD872F313B61F673C0187788" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Share-based Compensation Arrangement By Share-based Payment Award, Voting Rights of Common Stock, Holding Percentage</link:label>
    <link:label id="lab_selb_ShareBasedCompensationArrangementByShareBasedPaymentAwardVotingRightsOfCommonStockHoldingPercentage_D0C0E39ABD872F313B61F673C0187788_documentation_en-US" xlink:label="lab_selb_ShareBasedCompensationArrangementByShareBasedPaymentAwardVotingRightsOfCommonStockHoldingPercentage_D0C0E39ABD872F313B61F673C0187788" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:type="resource" xml:lang="en-US">Represents the percentage of voting rights of all classes of stock held by the employees.</link:label>
    <link:loc xlink:href="selb-20161231.xsd#selb_ShareBasedCompensationArrangementByShareBasedPaymentAwardVotingRightsOfCommonStockHoldingPercentage" xlink:label="loc_selb_ShareBasedCompensationArrangementByShareBasedPaymentAwardVotingRightsOfCommonStockHoldingPercentage_D0C0E39ABD872F313B61F673C0187788" xlink:type="locator" />
    <link:labelArc order="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_selb_ShareBasedCompensationArrangementByShareBasedPaymentAwardVotingRightsOfCommonStockHoldingPercentage_D0C0E39ABD872F313B61F673C0187788" xlink:to="lab_selb_ShareBasedCompensationArrangementByShareBasedPaymentAwardVotingRightsOfCommonStockHoldingPercentage_D0C0E39ABD872F313B61F673C0187788" xlink:type="arc" />
    <link:label id="lab_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardAwardVestingPeriod1_58B71F3A645890076ABBF673C018302D_terseLabel_en-US" xlink:label="lab_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardAwardVestingPeriod1_58B71F3A645890076ABBF673C018302D" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Award vesting term</link:label>
    <link:label id="lab_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardAwardVestingPeriod1_58B71F3A645890076ABBF673C018302D_label_en-US" xlink:label="lab_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardAwardVestingPeriod1_58B71F3A645890076ABBF673C018302D" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Share-based Compensation Arrangement by Share-based Payment Award, Award Vesting Period</link:label>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardAwardVestingPeriod1" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardAwardVestingPeriod1_58B71F3A645890076ABBF673C018302D" xlink:type="locator" />
    <link:labelArc order="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardAwardVestingPeriod1_58B71F3A645890076ABBF673C018302D" xlink:to="lab_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardAwardVestingPeriod1_58B71F3A645890076ABBF673C018302D" xlink:type="arc" />
    <link:label id="lab_us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardExpirationPeriod_2FF34CDCFCDAD5D9920BF673C018E451_terseLabel_en-US" xlink:label="lab_us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardExpirationPeriod_2FF34CDCFCDAD5D9920BF673C018E451" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Award expiration term</link:label>
    <link:label id="lab_us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardExpirationPeriod_2FF34CDCFCDAD5D9920BF673C018E451_label_en-US" xlink:label="lab_us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardExpirationPeriod_2FF34CDCFCDAD5D9920BF673C018E451" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Share-based Compensation Arrangement by Share-based Payment Award, Expiration Period</link:label>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardExpirationPeriod" xlink:label="loc_us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardExpirationPeriod_2FF34CDCFCDAD5D9920BF673C018E451" xlink:type="locator" />
    <link:labelArc order="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardExpirationPeriod_2FF34CDCFCDAD5D9920BF673C018E451" xlink:to="lab_us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardExpirationPeriod_2FF34CDCFCDAD5D9920BF673C018E451" xlink:type="arc" />
    <link:label id="lab_selb_ShareBasedCompensationArrangementByShareBasedPaymentAwardForfeituresRate_DE35AB0895B35060FC6BF673C0182D2B_terseLabel_en-US" xlink:label="lab_selb_ShareBasedCompensationArrangementByShareBasedPaymentAwardForfeituresRate_DE35AB0895B35060FC6BF673C0182D2B" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Estimated forfeitures rate</link:label>
    <link:label id="lab_selb_ShareBasedCompensationArrangementByShareBasedPaymentAwardForfeituresRate_DE35AB0895B35060FC6BF673C0182D2B_label_en-US" xlink:label="lab_selb_ShareBasedCompensationArrangementByShareBasedPaymentAwardForfeituresRate_DE35AB0895B35060FC6BF673C0182D2B" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Share-based Compensation Arrangement By Share-based Payment Award Forfeitures Rate</link:label>
    <link:label id="lab_selb_ShareBasedCompensationArrangementByShareBasedPaymentAwardForfeituresRate_DE35AB0895B35060FC6BF673C0182D2B_documentation_en-US" xlink:label="lab_selb_ShareBasedCompensationArrangementByShareBasedPaymentAwardForfeituresRate_DE35AB0895B35060FC6BF673C0182D2B" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:type="resource" xml:lang="en-US">Represents the percentage of forfeitures rate of the stock options based on the historical trends.</link:label>
    <link:loc xlink:href="selb-20161231.xsd#selb_ShareBasedCompensationArrangementByShareBasedPaymentAwardForfeituresRate" xlink:label="loc_selb_ShareBasedCompensationArrangementByShareBasedPaymentAwardForfeituresRate_DE35AB0895B35060FC6BF673C0182D2B" xlink:type="locator" />
    <link:labelArc order="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_selb_ShareBasedCompensationArrangementByShareBasedPaymentAwardForfeituresRate_DE35AB0895B35060FC6BF673C0182D2B" xlink:to="lab_selb_ShareBasedCompensationArrangementByShareBasedPaymentAwardForfeituresRate_DE35AB0895B35060FC6BF673C0182D2B" xlink:type="arc" />
    <link:label id="lab_selb_EmployeeStockPurchasePlanMaximumPercentageOfSharesReservedBasedOnSharesOutstanding_A3643E63C9026C28A88AF673C018F9C2_terseLabel_en-US" xlink:label="lab_selb_EmployeeStockPurchasePlanMaximumPercentageOfSharesReservedBasedOnSharesOutstanding_A3643E63C9026C28A88AF673C018F9C2" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Automatic increase in the number of shares that may be issued (as a percent)</link:label>
    <link:label id="lab_selb_EmployeeStockPurchasePlanMaximumPercentageOfSharesReservedBasedOnSharesOutstanding_A3643E63C9026C28A88AF673C018F9C2_label_en-US" xlink:label="lab_selb_EmployeeStockPurchasePlanMaximumPercentageOfSharesReservedBasedOnSharesOutstanding_A3643E63C9026C28A88AF673C018F9C2" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Employee Stock Purchase Plan Maximum Percentage Of Shares Reserved Based On Shares Outstanding</link:label>
    <link:label id="lab_selb_EmployeeStockPurchasePlanMaximumPercentageOfSharesReservedBasedOnSharesOutstanding_A3643E63C9026C28A88AF673C018F9C2_documentation_en-US" xlink:label="lab_selb_EmployeeStockPurchasePlanMaximumPercentageOfSharesReservedBasedOnSharesOutstanding_A3643E63C9026C28A88AF673C018F9C2" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:type="resource" xml:lang="en-US">The maximum percentage increase in the shares reserved for future issuance each year based on the number of common stock outstanding at the last day of the year.</link:label>
    <link:loc xlink:href="selb-20161231.xsd#selb_EmployeeStockPurchasePlanMaximumPercentageOfSharesReservedBasedOnSharesOutstanding" xlink:label="loc_selb_EmployeeStockPurchasePlanMaximumPercentageOfSharesReservedBasedOnSharesOutstanding_A3643E63C9026C28A88AF673C018F9C2" xlink:type="locator" />
    <link:labelArc order="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_selb_EmployeeStockPurchasePlanMaximumPercentageOfSharesReservedBasedOnSharesOutstanding_A3643E63C9026C28A88AF673C018F9C2" xlink:to="lab_selb_EmployeeStockPurchasePlanMaximumPercentageOfSharesReservedBasedOnSharesOutstanding_A3643E63C9026C28A88AF673C018F9C2" xlink:type="arc" />
    <link:label id="lab_us-gaap_StockIssuedDuringPeriodSharesEmployeeStockPurchasePlans_AE6E8DAA83DE19398742F673C0183135_terseLabel_en-US" xlink:label="lab_us-gaap_StockIssuedDuringPeriodSharesEmployeeStockPurchasePlans_AE6E8DAA83DE19398742F673C0183135" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Shares issued under ESPP (in shares)</link:label>
    <link:label id="lab_us-gaap_StockIssuedDuringPeriodSharesEmployeeStockPurchasePlans_AE6E8DAA83DE19398742F673C0183135_label_en-US" xlink:label="lab_us-gaap_StockIssuedDuringPeriodSharesEmployeeStockPurchasePlans_AE6E8DAA83DE19398742F673C0183135" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Stock Issued During Period, Shares, Employee Stock Purchase Plans</link:label>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_StockIssuedDuringPeriodSharesEmployeeStockPurchasePlans" xlink:label="loc_us-gaap_StockIssuedDuringPeriodSharesEmployeeStockPurchasePlans_AE6E8DAA83DE19398742F673C0183135" xlink:type="locator" />
    <link:labelArc order="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_us-gaap_StockIssuedDuringPeriodSharesEmployeeStockPurchasePlans_AE6E8DAA83DE19398742F673C0183135" xlink:to="lab_us-gaap_StockIssuedDuringPeriodSharesEmployeeStockPurchasePlans_AE6E8DAA83DE19398742F673C0183135" xlink:type="arc" />
    <link:label id="lab_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriodWeightedAverageGrantDateFairValue_F3CD3D27AE9BDCB1B54CF673C018B85C_terseLabel_en-US" xlink:label="lab_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriodWeightedAverageGrantDateFairValue_F3CD3D27AE9BDCB1B54CF673C018B85C" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Weighted average grant date fair value of stock options (in dollars per share)</link:label>
    <link:label id="lab_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriodWeightedAverageGrantDateFairValue_F3CD3D27AE9BDCB1B54CF673C018B85C_label_en-US" xlink:label="lab_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriodWeightedAverageGrantDateFairValue_F3CD3D27AE9BDCB1B54CF673C018B85C" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Share-based Compensation Arrangement by Share-based Payment Award, Options, Grants in Period, Weighted Average Grant Date Fair Value</link:label>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriodWeightedAverageGrantDateFairValue" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriodWeightedAverageGrantDateFairValue_F3CD3D27AE9BDCB1B54CF673C018B85C" xlink:type="locator" />
    <link:labelArc order="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriodWeightedAverageGrantDateFairValue_F3CD3D27AE9BDCB1B54CF673C018B85C" xlink:to="lab_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriodWeightedAverageGrantDateFairValue_F3CD3D27AE9BDCB1B54CF673C018B85C" xlink:type="arc" />
    <link:label id="lab_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsVestedAndExpectedToVestOutstandingAggregateIntrinsicValue_769260480B2519788E2FF673C018FBD3_terseLabel_en-US" xlink:label="lab_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsVestedAndExpectedToVestOutstandingAggregateIntrinsicValue_769260480B2519788E2FF673C018FBD3" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Aggregate intrinsic value of stock options</link:label>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsVestedAndExpectedToVestOutstandingAggregateIntrinsicValue" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsVestedAndExpectedToVestOutstandingAggregateIntrinsicValue_769260480B2519788E2FF673C018FBD3" xlink:type="locator" />
    <link:labelArc order="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsVestedAndExpectedToVestOutstandingAggregateIntrinsicValue_769260480B2519788E2FF673C018FBD3" xlink:to="lab_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsVestedAndExpectedToVestOutstandingAggregateIntrinsicValue_769260480B2519788E2FF673C018FBD3" xlink:type="arc" />
    <link:label id="lab_us-gaap_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognizedStockOptions_B50CB3CB0BEEFF58F851F673C0182883_terseLabel_en-US" xlink:label="lab_us-gaap_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognizedStockOptions_B50CB3CB0BEEFF58F851F673C0182883" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Unrecognized compensation expense related to unvested employee stock options</link:label>
    <link:label id="lab_us-gaap_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognizedStockOptions_B50CB3CB0BEEFF58F851F673C0182883_label_en-US" xlink:label="lab_us-gaap_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognizedStockOptions_B50CB3CB0BEEFF58F851F673C0182883" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Employee Service Share-based Compensation, Nonvested Awards, Compensation Not yet Recognized, Stock Options</link:label>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognizedStockOptions" xlink:label="loc_us-gaap_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognizedStockOptions_B50CB3CB0BEEFF58F851F673C0182883" xlink:type="locator" />
    <link:labelArc order="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_us-gaap_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognizedStockOptions_B50CB3CB0BEEFF58F851F673C0182883" xlink:to="lab_us-gaap_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognizedStockOptions_B50CB3CB0BEEFF58F851F673C0182883" xlink:type="arc" />
    <link:label id="lab_us-gaap_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognizedPeriodForRecognition1_463F5764A950788227B2F673C0189AF1_verboseLabel_en-US" xlink:label="lab_us-gaap_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognizedPeriodForRecognition1_463F5764A950788227B2F673C0189AF1" xlink:role="http://www.xbrl.org/2003/role/verboseLabel" xlink:type="resource" xml:lang="en-US">Weighted average period for recognition</link:label>
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    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognizedPeriodForRecognition1" xlink:label="loc_us-gaap_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognizedPeriodForRecognition1_463F5764A950788227B2F673C0189AF1" xlink:type="locator" />
    <link:labelArc order="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_us-gaap_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognizedPeriodForRecognition1_463F5764A950788227B2F673C0189AF1" xlink:to="lab_us-gaap_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognizedPeriodForRecognition1_463F5764A950788227B2F673C0189AF1" xlink:type="arc" />
    <link:label id="lab_us-gaap_AdjustmentOfWarrantsGrantedForServices_E65956FBE2A0C528E388F673C018E1DF_terseLabel_en-US" xlink:label="lab_us-gaap_AdjustmentOfWarrantsGrantedForServices_E65956FBE2A0C528E388F673C018E1DF" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Non-employee stock-based compensation expense</link:label>
    <link:label id="lab_us-gaap_AdjustmentOfWarrantsGrantedForServices_E65956FBE2A0C528E388F673C018E1DF_label_en-US" xlink:label="lab_us-gaap_AdjustmentOfWarrantsGrantedForServices_E65956FBE2A0C528E388F673C018E1DF" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Adjustment of Warrants Granted for Services</link:label>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_AdjustmentOfWarrantsGrantedForServices" xlink:label="loc_us-gaap_AdjustmentOfWarrantsGrantedForServices_E65956FBE2A0C528E388F673C018E1DF" xlink:type="locator" />
    <link:labelArc order="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_us-gaap_AdjustmentOfWarrantsGrantedForServices_E65956FBE2A0C528E388F673C018E1DF" xlink:to="lab_us-gaap_AdjustmentOfWarrantsGrantedForServices_E65956FBE2A0C528E388F673C018E1DF" xlink:type="arc" />
    <link:label id="lab_selb_ShareBasedGoodsAndNonEmployeeServicesTransactionCompensationNotYetRecognizedStockOptions_F1EEC515695FDF5B77B1F673C018F00E_terseLabel_en-US" xlink:label="lab_selb_ShareBasedGoodsAndNonEmployeeServicesTransactionCompensationNotYetRecognizedStockOptions_F1EEC515695FDF5B77B1F673C018F00E" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Unrecognized compensation expense related to unvested non-employee stock options</link:label>
    <link:label id="lab_selb_ShareBasedGoodsAndNonEmployeeServicesTransactionCompensationNotYetRecognizedStockOptions_F1EEC515695FDF5B77B1F673C018F00E_label_en-US" xlink:label="lab_selb_ShareBasedGoodsAndNonEmployeeServicesTransactionCompensationNotYetRecognizedStockOptions_F1EEC515695FDF5B77B1F673C018F00E" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Share-Based Goods And Non Employee Services Transaction, Compensation Not Yet Recognized, Stock Options</link:label>
    <link:label id="lab_selb_ShareBasedGoodsAndNonEmployeeServicesTransactionCompensationNotYetRecognizedStockOptions_F1EEC515695FDF5B77B1F673C018F00E_documentation_en-US" xlink:label="lab_selb_ShareBasedGoodsAndNonEmployeeServicesTransactionCompensationNotYetRecognizedStockOptions_F1EEC515695FDF5B77B1F673C018F00E" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:type="resource" xml:lang="en-US">Share-Based Goods And Non Employee Services Transaction, Compensation Not Yet Recognized, Stock Options</link:label>
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    <link:labelArc order="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_us-gaap_OperatingLeasesFutureMinimumPaymentsDueCurrent_DA7CB48BE5FBF7A7BBDDF226DC4E3682" xlink:to="lab_us-gaap_OperatingLeasesFutureMinimumPaymentsDueCurrent_DA7CB48BE5FBF7A7BBDDF226DC4E3682" xlink:type="arc" />
    <link:label id="lab_us-gaap_OperatingLeasesFutureMinimumPaymentsDueInTwoYears_57278482D0CCE132B949F226DC4E61E9_verboseLabel_en-US" xlink:label="lab_us-gaap_OperatingLeasesFutureMinimumPaymentsDueInTwoYears_57278482D0CCE132B949F226DC4E61E9" xlink:role="http://www.xbrl.org/2003/role/verboseLabel" xlink:type="resource" xml:lang="en-US">2018</link:label>
    <link:label id="lab_us-gaap_OperatingLeasesFutureMinimumPaymentsDueInTwoYears_57278482D0CCE132B949F226DC4E61E9_label_en-US" xlink:label="lab_us-gaap_OperatingLeasesFutureMinimumPaymentsDueInTwoYears_57278482D0CCE132B949F226DC4E61E9" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Operating Leases, Future Minimum Payments, Due in Two Years</link:label>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_OperatingLeasesFutureMinimumPaymentsDueInTwoYears" xlink:label="loc_us-gaap_OperatingLeasesFutureMinimumPaymentsDueInTwoYears_57278482D0CCE132B949F226DC4E61E9" xlink:type="locator" />
    <link:labelArc order="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_us-gaap_OperatingLeasesFutureMinimumPaymentsDueInTwoYears_57278482D0CCE132B949F226DC4E61E9" xlink:to="lab_us-gaap_OperatingLeasesFutureMinimumPaymentsDueInTwoYears_57278482D0CCE132B949F226DC4E61E9" xlink:type="arc" />
    <link:label id="lab_us-gaap_OperatingLeasesFutureMinimumPaymentsDueInThreeYears_36540C3F0ECCF3D73D66F226DC4ECC10_terseLabel_en-US" xlink:label="lab_us-gaap_OperatingLeasesFutureMinimumPaymentsDueInThreeYears_36540C3F0ECCF3D73D66F226DC4ECC10" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">2019</link:label>
    <link:label id="lab_us-gaap_OperatingLeasesFutureMinimumPaymentsDueInThreeYears_36540C3F0ECCF3D73D66F226DC4ECC10_label_en-US" xlink:label="lab_us-gaap_OperatingLeasesFutureMinimumPaymentsDueInThreeYears_36540C3F0ECCF3D73D66F226DC4ECC10" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Operating Leases, Future Minimum Payments, Due in Three Years</link:label>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_OperatingLeasesFutureMinimumPaymentsDueInThreeYears" xlink:label="loc_us-gaap_OperatingLeasesFutureMinimumPaymentsDueInThreeYears_36540C3F0ECCF3D73D66F226DC4ECC10" xlink:type="locator" />
    <link:labelArc order="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_us-gaap_OperatingLeasesFutureMinimumPaymentsDueInThreeYears_36540C3F0ECCF3D73D66F226DC4ECC10" xlink:to="lab_us-gaap_OperatingLeasesFutureMinimumPaymentsDueInThreeYears_36540C3F0ECCF3D73D66F226DC4ECC10" xlink:type="arc" />
    <link:label id="lab_us-gaap_OperatingLeasesFutureMinimumPaymentsDueInFourYears_F3BC4050BF2AC2EA11C9F226DC4E74E2_terseLabel_en-US" xlink:label="lab_us-gaap_OperatingLeasesFutureMinimumPaymentsDueInFourYears_F3BC4050BF2AC2EA11C9F226DC4E74E2" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">2020</link:label>
    <link:label id="lab_us-gaap_OperatingLeasesFutureMinimumPaymentsDueInFourYears_F3BC4050BF2AC2EA11C9F226DC4E74E2_label_en-US" xlink:label="lab_us-gaap_OperatingLeasesFutureMinimumPaymentsDueInFourYears_F3BC4050BF2AC2EA11C9F226DC4E74E2" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Operating Leases, Future Minimum Payments, Due in Four Years</link:label>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_OperatingLeasesFutureMinimumPaymentsDueInFourYears" xlink:label="loc_us-gaap_OperatingLeasesFutureMinimumPaymentsDueInFourYears_F3BC4050BF2AC2EA11C9F226DC4E74E2" xlink:type="locator" />
    <link:labelArc order="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_us-gaap_OperatingLeasesFutureMinimumPaymentsDueInFourYears_F3BC4050BF2AC2EA11C9F226DC4E74E2" xlink:to="lab_us-gaap_OperatingLeasesFutureMinimumPaymentsDueInFourYears_F3BC4050BF2AC2EA11C9F226DC4E74E2" xlink:type="arc" />
    <link:label id="lab_us-gaap_OperatingLeasesFutureMinimumPaymentsDue_32BA4C841BDE7220C401F226DC4E482C_totalLabel_en-US" xlink:label="lab_us-gaap_OperatingLeasesFutureMinimumPaymentsDue_32BA4C841BDE7220C401F226DC4E482C" xlink:role="http://www.xbrl.org/2003/role/totalLabel" xlink:type="resource" xml:lang="en-US">Total minimum lease payments</link:label>
    <link:label id="lab_us-gaap_OperatingLeasesFutureMinimumPaymentsDue_32BA4C841BDE7220C401F226DC4E482C_label_en-US" xlink:label="lab_us-gaap_OperatingLeasesFutureMinimumPaymentsDue_32BA4C841BDE7220C401F226DC4E482C" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Operating Leases, Future Minimum Payments Due</link:label>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_OperatingLeasesFutureMinimumPaymentsDue" xlink:label="loc_us-gaap_OperatingLeasesFutureMinimumPaymentsDue_32BA4C841BDE7220C401F226DC4E482C" xlink:type="locator" />
    <link:labelArc order="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_us-gaap_OperatingLeasesFutureMinimumPaymentsDue_32BA4C841BDE7220C401F226DC4E482C" xlink:to="lab_us-gaap_OperatingLeasesFutureMinimumPaymentsDue_32BA4C841BDE7220C401F226DC4E482C" xlink:type="arc" />
    <link:label id="lab_us-gaap_CommitmentsAndContingenciesDisclosureTextBlock_CFA56C3609572C6A51C2F226DC5AB1B6_terseLabel_en-US" xlink:label="lab_us-gaap_CommitmentsAndContingenciesDisclosureTextBlock_CFA56C3609572C6A51C2F226DC5AB1B6" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Commitments and Contingencies</link:label>
    <link:label id="lab_us-gaap_CommitmentsAndContingenciesDisclosureTextBlock_CFA56C3609572C6A51C2F226DC5AB1B6_label_en-US" xlink:label="lab_us-gaap_CommitmentsAndContingenciesDisclosureTextBlock_CFA56C3609572C6A51C2F226DC5AB1B6" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Commitments and Contingencies Disclosure [Text Block]</link:label>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_CommitmentsAndContingenciesDisclosureTextBlock" xlink:label="loc_us-gaap_CommitmentsAndContingenciesDisclosureTextBlock_CFA56C3609572C6A51C2F226DC5AB1B6" xlink:type="locator" />
    <link:labelArc order="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_us-gaap_CommitmentsAndContingenciesDisclosureTextBlock_CFA56C3609572C6A51C2F226DC5AB1B6" xlink:to="lab_us-gaap_CommitmentsAndContingenciesDisclosureTextBlock_CFA56C3609572C6A51C2F226DC5AB1B6" xlink:type="arc" />
    <link:label id="lab_us-gaap_IncomeTaxDisclosureTextBlock_CAA02D6DE58F5FA1A78CB44B750574EF_terseLabel_en-US" xlink:label="lab_us-gaap_IncomeTaxDisclosureTextBlock_CAA02D6DE58F5FA1A78CB44B750574EF" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Income Taxes</link:label>
    <link:label id="lab_us-gaap_IncomeTaxDisclosureTextBlock_CAA02D6DE58F5FA1A78CB44B750574EF_label_en-US" xlink:label="lab_us-gaap_IncomeTaxDisclosureTextBlock_CAA02D6DE58F5FA1A78CB44B750574EF" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Income Tax Disclosure [Text Block]</link:label>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_IncomeTaxDisclosureTextBlock" xlink:label="loc_us-gaap_IncomeTaxDisclosureTextBlock_CAA02D6DE58F5FA1A78CB44B750574EF" xlink:type="locator" />
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    <link:label id="lab_us-gaap_ScheduleOfOperatingLeasedAssetsTable_0A4D31D07A51963033D5F673C0545275_terseLabel_en-US" xlink:label="lab_us-gaap_ScheduleOfOperatingLeasedAssetsTable_0A4D31D07A51963033D5F673C0545275" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Schedule of Operating Leased Assets [Table]</link:label>
    <link:label id="lab_us-gaap_ScheduleOfOperatingLeasedAssetsTable_0A4D31D07A51963033D5F673C0545275_label_en-US" xlink:label="lab_us-gaap_ScheduleOfOperatingLeasedAssetsTable_0A4D31D07A51963033D5F673C0545275" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Schedule of Operating Leased Assets [Table]</link:label>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_ScheduleOfOperatingLeasedAssetsTable" xlink:label="loc_us-gaap_ScheduleOfOperatingLeasedAssetsTable_0A4D31D07A51963033D5F673C0545275" xlink:type="locator" />
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    <link:label id="lab_us-gaap_LeaseArrangementTypeAxis_CBC5E2F7D4594F36D416F673C054951E_terseLabel_en-US" xlink:label="lab_us-gaap_LeaseArrangementTypeAxis_CBC5E2F7D4594F36D416F673C054951E" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Lease Arrangement, Type [Axis]</link:label>
    <link:label id="lab_us-gaap_LeaseArrangementTypeAxis_CBC5E2F7D4594F36D416F673C054951E_label_en-US" xlink:label="lab_us-gaap_LeaseArrangementTypeAxis_CBC5E2F7D4594F36D416F673C054951E" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Lease Arrangement, Type [Axis]</link:label>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_LeaseArrangementTypeAxis" xlink:label="loc_us-gaap_LeaseArrangementTypeAxis_CBC5E2F7D4594F36D416F673C054951E" xlink:type="locator" />
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    <link:label id="lab_us-gaap_LeaseArrangementTypeDomain_C9E13B45A3FE6A7E87EFF673C054BC26_label_en-US" xlink:label="lab_us-gaap_LeaseArrangementTypeDomain_C9E13B45A3FE6A7E87EFF673C054BC26" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Lease Arrangement, Type [Domain]</link:label>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_LeaseArrangementTypeDomain" xlink:label="loc_us-gaap_LeaseArrangementTypeDomain_C9E13B45A3FE6A7E87EFF673C054BC26" xlink:type="locator" />
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    <link:label id="lab_selb_LaboratoryAndOfficeSpaceMember_1035D28B262216EE8E36F673C054E437_terseLabel_en-US" xlink:label="lab_selb_LaboratoryAndOfficeSpaceMember_1035D28B262216EE8E36F673C054E437" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Laboratory and office space</link:label>
    <link:label id="lab_selb_LaboratoryAndOfficeSpaceMember_1035D28B262216EE8E36F673C054E437_label_en-US" xlink:label="lab_selb_LaboratoryAndOfficeSpaceMember_1035D28B262216EE8E36F673C054E437" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Laboratory And Office Space [Member]</link:label>
    <link:label id="lab_selb_LaboratoryAndOfficeSpaceMember_1035D28B262216EE8E36F673C054E437_documentation_en-US" xlink:label="lab_selb_LaboratoryAndOfficeSpaceMember_1035D28B262216EE8E36F673C054E437" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:type="resource" xml:lang="en-US">Represents information pertaining to laboratory and office space member.</link:label>
    <link:loc xlink:href="selb-20161231.xsd#selb_LaboratoryAndOfficeSpaceMember" xlink:label="loc_selb_LaboratoryAndOfficeSpaceMember_1035D28B262216EE8E36F673C054E437" xlink:type="locator" />
    <link:labelArc order="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_selb_LaboratoryAndOfficeSpaceMember_1035D28B262216EE8E36F673C054E437" xlink:to="lab_selb_LaboratoryAndOfficeSpaceMember_1035D28B262216EE8E36F673C054E437" xlink:type="arc" />
    <link:label id="lab_selb_LaboratoryAndOfficeSpaceAgreementAmendmentApril2015Member_FD8C76CD3CA852016B71F673C054337E_terseLabel_en-US" xlink:label="lab_selb_LaboratoryAndOfficeSpaceAgreementAmendmentApril2015Member_FD8C76CD3CA852016B71F673C054337E" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Laboratory and office space agreement amendment</link:label>
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    <link:label id="lab_selb_LaboratoryAndOfficeSpaceAgreementAmendmentApril2015Member_FD8C76CD3CA852016B71F673C054337E_documentation_en-US" xlink:label="lab_selb_LaboratoryAndOfficeSpaceAgreementAmendmentApril2015Member_FD8C76CD3CA852016B71F673C054337E" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:type="resource" xml:lang="en-US">Represents information pertaining to laboratory and office space agreement that was amended in April 2015.</link:label>
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    <link:label id="lab_us-gaap_BalanceSheetLocationAxis_66454E750EEDC340140BF673C054C20D_terseLabel_en-US" xlink:label="lab_us-gaap_BalanceSheetLocationAxis_66454E750EEDC340140BF673C054C20D" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Balance Sheet Location [Axis]</link:label>
    <link:label id="lab_us-gaap_BalanceSheetLocationAxis_66454E750EEDC340140BF673C054C20D_label_en-US" xlink:label="lab_us-gaap_BalanceSheetLocationAxis_66454E750EEDC340140BF673C054C20D" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Balance Sheet Location [Axis]</link:label>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_BalanceSheetLocationAxis" xlink:label="loc_us-gaap_BalanceSheetLocationAxis_66454E750EEDC340140BF673C054C20D" xlink:type="locator" />
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    <link:label id="lab_us-gaap_BalanceSheetLocationDomain_C92E07EB1E4DBF58BA4CF673C054912E_terseLabel_en-US" xlink:label="lab_us-gaap_BalanceSheetLocationDomain_C92E07EB1E4DBF58BA4CF673C054912E" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Balance Sheet Location [Domain]</link:label>
    <link:label id="lab_us-gaap_BalanceSheetLocationDomain_C92E07EB1E4DBF58BA4CF673C054912E_label_en-US" xlink:label="lab_us-gaap_BalanceSheetLocationDomain_C92E07EB1E4DBF58BA4CF673C054912E" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Balance Sheet Location [Domain]</link:label>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_BalanceSheetLocationDomain" xlink:label="loc_us-gaap_BalanceSheetLocationDomain_C92E07EB1E4DBF58BA4CF673C054912E" xlink:type="locator" />
    <link:labelArc order="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_us-gaap_BalanceSheetLocationDomain_C92E07EB1E4DBF58BA4CF673C054912E" xlink:to="lab_us-gaap_BalanceSheetLocationDomain_C92E07EB1E4DBF58BA4CF673C054912E" xlink:type="arc" />
    <link:label id="lab_selb_RestrictedCashAndOtherDepositsMember_2A5A670D6C3E3D910AACF673C054F3AC_terseLabel_en-US" xlink:label="lab_selb_RestrictedCashAndOtherDepositsMember_2A5A670D6C3E3D910AACF673C054F3AC" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Restricted cash and other deposits</link:label>
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    <link:label id="lab_selb_RestrictedCashAndOtherDepositsMember_2A5A670D6C3E3D910AACF673C054F3AC_documentation_en-US" xlink:label="lab_selb_RestrictedCashAndOtherDepositsMember_2A5A670D6C3E3D910AACF673C054F3AC" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:type="resource" xml:lang="en-US">Represents inforamtion pertaining to restricted cash and other deposits member.</link:label>
    <link:loc xlink:href="selb-20161231.xsd#selb_RestrictedCashAndOtherDepositsMember" xlink:label="loc_selb_RestrictedCashAndOtherDepositsMember_2A5A670D6C3E3D910AACF673C054F3AC" xlink:type="locator" />
    <link:labelArc order="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_selb_RestrictedCashAndOtherDepositsMember_2A5A670D6C3E3D910AACF673C054F3AC" xlink:to="lab_selb_RestrictedCashAndOtherDepositsMember_2A5A670D6C3E3D910AACF673C054F3AC" xlink:type="arc" />
    <link:label id="lab_us-gaap_AccountsPayableAndAccruedLiabilitiesMember_849C11F75FE9E04619BBF673C054E4F7_terseLabel_en-US" xlink:label="lab_us-gaap_AccountsPayableAndAccruedLiabilitiesMember_849C11F75FE9E04619BBF673C054E4F7" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Accrued expenses</link:label>
    <link:label id="lab_us-gaap_AccountsPayableAndAccruedLiabilitiesMember_849C11F75FE9E04619BBF673C054E4F7_label_en-US" xlink:label="lab_us-gaap_AccountsPayableAndAccruedLiabilitiesMember_849C11F75FE9E04619BBF673C054E4F7" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Accounts Payable and Accrued Liabilities [Member]</link:label>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_AccountsPayableAndAccruedLiabilitiesMember" xlink:label="loc_us-gaap_AccountsPayableAndAccruedLiabilitiesMember_849C11F75FE9E04619BBF673C054E4F7" xlink:type="locator" />
    <link:labelArc order="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_us-gaap_AccountsPayableAndAccruedLiabilitiesMember_849C11F75FE9E04619BBF673C054E4F7" xlink:to="lab_us-gaap_AccountsPayableAndAccruedLiabilitiesMember_849C11F75FE9E04619BBF673C054E4F7" xlink:type="arc" />
    <link:label id="lab_us-gaap_LetterOfCreditMember_A81E7E1B5447FBFD0315F673C054DFF8_terseLabel_en-US" xlink:label="lab_us-gaap_LetterOfCreditMember_A81E7E1B5447FBFD0315F673C054DFF8" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Letter of Credit</link:label>
    <link:label id="lab_us-gaap_LetterOfCreditMember_A81E7E1B5447FBFD0315F673C054DFF8_label_en-US" xlink:label="lab_us-gaap_LetterOfCreditMember_A81E7E1B5447FBFD0315F673C054DFF8" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Letter of Credit [Member]</link:label>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_LetterOfCreditMember" xlink:label="loc_us-gaap_LetterOfCreditMember_A81E7E1B5447FBFD0315F673C054DFF8" xlink:type="locator" />
    <link:labelArc order="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_us-gaap_LetterOfCreditMember_A81E7E1B5447FBFD0315F673C054DFF8" xlink:to="lab_us-gaap_LetterOfCreditMember_A81E7E1B5447FBFD0315F673C054DFF8" xlink:type="arc" />
    <link:label id="lab_us-gaap_StatementLineItems_4CE45BAF939424A53053F673C054DC8D_terseLabel_en-US" xlink:label="lab_us-gaap_StatementLineItems_4CE45BAF939424A53053F673C054DC8D" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Statement [Line Items]</link:label>
    <link:label id="lab_us-gaap_StatementLineItems_4CE45BAF939424A53053F673C054DC8D_label_en-US" xlink:label="lab_us-gaap_StatementLineItems_4CE45BAF939424A53053F673C054DC8D" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Statement [Line Items]</link:label>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_StatementLineItems" xlink:label="loc_us-gaap_StatementLineItems_4CE45BAF939424A53053F673C054DC8D" xlink:type="locator" />
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    <link:label id="lab_us-gaap_PaymentsForProceedsFromTenantAllowance_336FF7DCD24600B04ECFF673C054DAB7_terseLabel_en-US" xlink:label="lab_us-gaap_PaymentsForProceedsFromTenantAllowance_336FF7DCD24600B04ECFF673C054DAB7" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Tenant improvement allowance</link:label>
    <link:label id="lab_us-gaap_PaymentsForProceedsFromTenantAllowance_336FF7DCD24600B04ECFF673C054DAB7_label_en-US" xlink:label="lab_us-gaap_PaymentsForProceedsFromTenantAllowance_336FF7DCD24600B04ECFF673C054DAB7" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Payments for (Proceeds from) Tenant Allowance</link:label>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_PaymentsForProceedsFromTenantAllowance" xlink:label="loc_us-gaap_PaymentsForProceedsFromTenantAllowance_336FF7DCD24600B04ECFF673C054DAB7" xlink:type="locator" />
    <link:labelArc order="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_us-gaap_PaymentsForProceedsFromTenantAllowance_336FF7DCD24600B04ECFF673C054DAB7" xlink:to="lab_us-gaap_PaymentsForProceedsFromTenantAllowance_336FF7DCD24600B04ECFF673C054DAB7" xlink:type="arc" />
    <link:label id="lab_us-gaap_LineOfCreditFacilityMaximumBorrowingCapacity_D66DBD90241F0813A20FF673C054215F_terseLabel_en-US" xlink:label="lab_us-gaap_LineOfCreditFacilityMaximumBorrowingCapacity_D66DBD90241F0813A20FF673C054215F" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Letter of credit</link:label>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_LineOfCreditFacilityMaximumBorrowingCapacity" xlink:label="loc_us-gaap_LineOfCreditFacilityMaximumBorrowingCapacity_D66DBD90241F0813A20FF673C054215F" xlink:type="locator" />
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    <link:label id="lab_us-gaap_OperatingLeasesRentExpenseSubleaseRentals1_5BCEDABA38F5385BF008F673C054F9EB_terseLabel_en-US" xlink:label="lab_us-gaap_OperatingLeasesRentExpenseSubleaseRentals1_5BCEDABA38F5385BF008F673C054F9EB" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Sublease income</link:label>
    <link:label id="lab_us-gaap_OperatingLeasesRentExpenseSubleaseRentals1_5BCEDABA38F5385BF008F673C054F9EB_label_en-US" xlink:label="lab_us-gaap_OperatingLeasesRentExpenseSubleaseRentals1_5BCEDABA38F5385BF008F673C054F9EB" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Operating Leases, Rent Expense, Sublease Rentals</link:label>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_OperatingLeasesRentExpenseSubleaseRentals1" xlink:label="loc_us-gaap_OperatingLeasesRentExpenseSubleaseRentals1_5BCEDABA38F5385BF008F673C054F9EB" xlink:type="locator" />
    <link:labelArc order="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_us-gaap_OperatingLeasesRentExpenseSubleaseRentals1_5BCEDABA38F5385BF008F673C054F9EB" xlink:to="lab_us-gaap_OperatingLeasesRentExpenseSubleaseRentals1_5BCEDABA38F5385BF008F673C054F9EB" xlink:type="arc" />
    <link:label id="lab_us-gaap_AreaOfRealEstateProperty_354E627426B19122D509F673C05428E7_terseLabel_en-US" xlink:label="lab_us-gaap_AreaOfRealEstateProperty_354E627426B19122D509F673C05428E7" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Area exchanged (in square feet)</link:label>
    <link:label id="lab_us-gaap_AreaOfRealEstateProperty_354E627426B19122D509F673C05428E7_label_en-US" xlink:label="lab_us-gaap_AreaOfRealEstateProperty_354E627426B19122D509F673C05428E7" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Area of Real Estate Property</link:label>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_AreaOfRealEstateProperty" xlink:label="loc_us-gaap_AreaOfRealEstateProperty_354E627426B19122D509F673C05428E7" xlink:type="locator" />
    <link:labelArc order="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_us-gaap_AreaOfRealEstateProperty_354E627426B19122D509F673C05428E7" xlink:to="lab_us-gaap_AreaOfRealEstateProperty_354E627426B19122D509F673C05428E7" xlink:type="arc" />
    <link:label id="lab_selb_DeferredRentAndLeaseIncentiveLiability_3A0658781549CD6F2B02F673C0544C75_terseLabel_en-US" xlink:label="lab_selb_DeferredRentAndLeaseIncentiveLiability_3A0658781549CD6F2B02F673C0544C75" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Deferred rent and lease incentive liability</link:label>
    <link:label id="lab_selb_DeferredRentAndLeaseIncentiveLiability_3A0658781549CD6F2B02F673C0544C75_label_en-US" xlink:label="lab_selb_DeferredRentAndLeaseIncentiveLiability_3A0658781549CD6F2B02F673C0544C75" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Deferred Rent And Lease Incentive Liability</link:label>
    <link:label id="lab_selb_DeferredRentAndLeaseIncentiveLiability_3A0658781549CD6F2B02F673C0544C75_documentation_en-US" xlink:label="lab_selb_DeferredRentAndLeaseIncentiveLiability_3A0658781549CD6F2B02F673C0544C75" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:type="resource" xml:lang="en-US">This element represents both current and non current costs incurred by the lessor that are (a) costs to originate a lease incurred in transactions with independent third parties that (i) result directly from and are essential to acquire that lease and (ii) would not have been incurred had that leasing transaction not occurred and (b) certain costs directly related to specified activities performed by the lessor for that lease and includes the deferred charge for an incentive or inducement granted by a lessor to a lessee, in order to motivate the lessee to enter the lease agreement, which incentive or inducement is to be recognized as a reduction of rental revenue over the lease term.</link:label>
    <link:loc xlink:href="selb-20161231.xsd#selb_DeferredRentAndLeaseIncentiveLiability" xlink:label="loc_selb_DeferredRentAndLeaseIncentiveLiability_3A0658781549CD6F2B02F673C0544C75" xlink:type="locator" />
    <link:labelArc order="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_selb_DeferredRentAndLeaseIncentiveLiability_3A0658781549CD6F2B02F673C0544C75" xlink:to="lab_selb_DeferredRentAndLeaseIncentiveLiability_3A0658781549CD6F2B02F673C0544C75" xlink:type="arc" />
    <link:label id="lab_selb_AccruedRentAndLeaseIncentivePayableCurrent_9E8B4757F3F8108DD274F673C054ED11_verboseLabel_en-US" xlink:label="lab_selb_AccruedRentAndLeaseIncentivePayableCurrent_9E8B4757F3F8108DD274F673C054ED11" xlink:role="http://www.xbrl.org/2003/role/verboseLabel" xlink:type="resource" xml:lang="en-US">Current portion of deferred rent and lease incentive liability (less than in 2016)</link:label>
    <link:loc xlink:href="selb-20161231.xsd#selb_AccruedRentAndLeaseIncentivePayableCurrent" xlink:label="loc_selb_AccruedRentAndLeaseIncentivePayableCurrent_9E8B4757F3F8108DD274F673C054ED11" xlink:type="locator" />
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    <link:label id="lab_us-gaap_OperatingLeasesRentExpenseNet_CCB9D90F2A290863FF47F673C054C249_terseLabel_en-US" xlink:label="lab_us-gaap_OperatingLeasesRentExpenseNet_CCB9D90F2A290863FF47F673C054C249" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Rent expense, net of sublease payments</link:label>
    <link:label id="lab_us-gaap_OperatingLeasesRentExpenseNet_CCB9D90F2A290863FF47F673C054C249_label_en-US" xlink:label="lab_us-gaap_OperatingLeasesRentExpenseNet_CCB9D90F2A290863FF47F673C054C249" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Operating Leases, Rent Expense, Net</link:label>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_OperatingLeasesRentExpenseNet" xlink:label="loc_us-gaap_OperatingLeasesRentExpenseNet_CCB9D90F2A290863FF47F673C054C249" xlink:type="locator" />
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    <link:label id="lab_us-gaap_QuarterlyFinancialInformationDisclosureAbstract_F90CBC9B316E31F418B3B44E4B8270C1_label_en-US" xlink:label="lab_us-gaap_QuarterlyFinancialInformationDisclosureAbstract_F90CBC9B316E31F418B3B44E4B8270C1" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Quarterly Financial Information Disclosure [Abstract]</link:label>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_QuarterlyFinancialInformationDisclosureAbstract" xlink:label="loc_us-gaap_QuarterlyFinancialInformationDisclosureAbstract_F90CBC9B316E31F418B3B44E4B8270C1" xlink:type="locator" />
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    <link:label id="lab_us-gaap_ScheduleOfQuarterlyFinancialInformationTableTextBlock_83EA86DCBD08DE3F91C0B45027DC7ACD_terseLabel_en-US" xlink:label="lab_us-gaap_ScheduleOfQuarterlyFinancialInformationTableTextBlock_83EA86DCBD08DE3F91C0B45027DC7ACD" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Summary of Unaudited Quarterly Financial Data</link:label>
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    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_ScheduleOfQuarterlyFinancialInformationTableTextBlock" xlink:label="loc_us-gaap_ScheduleOfQuarterlyFinancialInformationTableTextBlock_83EA86DCBD08DE3F91C0B45027DC7ACD" xlink:type="locator" />
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    <link:label id="lab_selb_DocumentAndEntityInformationAbstract_51BBB4851E9AC4F0A535B8F39F3C6989_label_en-US" xlink:label="lab_selb_DocumentAndEntityInformationAbstract_51BBB4851E9AC4F0A535B8F39F3C6989" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Document and Entity Information</link:label>
    <link:label id="lab_selb_DocumentAndEntityInformationAbstract_51BBB4851E9AC4F0A535B8F39F3C6989_documentation_en-US" xlink:label="lab_selb_DocumentAndEntityInformationAbstract_51BBB4851E9AC4F0A535B8F39F3C6989" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:type="resource" xml:lang="en-US" />
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    <link:label id="lab_dei_DocumentType_B012EB612BBEB347708EB8F39F3CEFD1_terseLabel_en-US" xlink:label="lab_dei_DocumentType_B012EB612BBEB347708EB8F39F3CEFD1" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Document Type</link:label>
    <link:label id="lab_dei_DocumentType_B012EB612BBEB347708EB8F39F3CEFD1_label_en-US" xlink:label="lab_dei_DocumentType_B012EB612BBEB347708EB8F39F3CEFD1" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Document Type</link:label>
    <link:loc xlink:href="http://xbrl.sec.gov/dei/2014/dei-2014-01-31.xsd#dei_DocumentType" xlink:label="loc_dei_DocumentType_B012EB612BBEB347708EB8F39F3CEFD1" xlink:type="locator" />
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    <link:label id="lab_us-gaap_ScheduleOfStockByClassTable_895887C5C9EEF250DAC0F226DBC72C31_terseLabel_en-US" xlink:label="lab_us-gaap_ScheduleOfStockByClassTable_895887C5C9EEF250DAC0F226DBC72C31" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Schedule of Stock by Class [Table]</link:label>
    <link:label id="lab_us-gaap_ScheduleOfStockByClassTable_895887C5C9EEF250DAC0F226DBC72C31_label_en-US" xlink:label="lab_us-gaap_ScheduleOfStockByClassTable_895887C5C9EEF250DAC0F226DBC72C31" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Schedule of Stock by Class [Table]</link:label>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_ScheduleOfStockByClassTable" xlink:label="loc_us-gaap_ScheduleOfStockByClassTable_895887C5C9EEF250DAC0F226DBC72C31" xlink:type="locator" />
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    <link:label id="lab_selb_SeriesARedeemableConvertiblePreferredStockMember_C5BC62E1EF187C21E07FF226DBC77861_verboseLabel_en-US" xlink:label="lab_selb_SeriesARedeemableConvertiblePreferredStockMember_C5BC62E1EF187C21E07FF226DBC77861" xlink:role="http://www.xbrl.org/2003/role/verboseLabel" xlink:type="resource" xml:lang="en-US">Conversion of Series A Preferred</link:label>
    <link:label id="lab_selb_SeriesARedeemableConvertiblePreferredStockMember_C5BC62E1EF187C21E07FF226DBC77861_label_en-US" xlink:label="lab_selb_SeriesARedeemableConvertiblePreferredStockMember_C5BC62E1EF187C21E07FF226DBC77861" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Series A Redeemable Convertible Preferred Stock [Member]</link:label>
    <link:label id="lab_selb_SeriesARedeemableConvertiblePreferredStockMember_C5BC62E1EF187C21E07FF226DBC77861_documentation_en-US" xlink:label="lab_selb_SeriesARedeemableConvertiblePreferredStockMember_C5BC62E1EF187C21E07FF226DBC77861" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:type="resource" xml:lang="en-US">Represents information pertaining to series A redeemable convertible preferred stock.</link:label>
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    <link:label id="lab_selb_SeriesBRedeemableConvertiblePreferredStockMember_2FDC8966444260DFD461F226DBC8D080_verboseLabel_en-US" xlink:label="lab_selb_SeriesBRedeemableConvertiblePreferredStockMember_2FDC8966444260DFD461F226DBC8D080" xlink:role="http://www.xbrl.org/2003/role/verboseLabel" xlink:type="resource" xml:lang="en-US">Conversion of Series B Preferred</link:label>
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    <link:label id="lab_selb_SeriesBRedeemableConvertiblePreferredStockMember_2FDC8966444260DFD461F226DBC8D080_documentation_en-US" xlink:label="lab_selb_SeriesBRedeemableConvertiblePreferredStockMember_2FDC8966444260DFD461F226DBC8D080" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:type="resource" xml:lang="en-US">Represents information pertaining to series B redeemable convertible preferred stock.</link:label>
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    <link:label id="lab_selb_SeriesCRedeemableConvertiblePreferredStockMember_99660984A3FD41DCC1A7F226DBC8B808_verboseLabel_en-US" xlink:label="lab_selb_SeriesCRedeemableConvertiblePreferredStockMember_99660984A3FD41DCC1A7F226DBC8B808" xlink:role="http://www.xbrl.org/2003/role/verboseLabel" xlink:type="resource" xml:lang="en-US">Conversion of Series C Preferred</link:label>
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    <link:label id="lab_selb_SeriesCRedeemableConvertiblePreferredStockMember_99660984A3FD41DCC1A7F226DBC8B808_documentation_en-US" xlink:label="lab_selb_SeriesCRedeemableConvertiblePreferredStockMember_99660984A3FD41DCC1A7F226DBC8B808" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:type="resource" xml:lang="en-US">Represents information pertaining to series C redeemable convertible preferred stock.</link:label>
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    <link:label id="lab_us-gaap_WarrantMember_2F2CECF49A119494730FF226DBC89E6F_verboseLabel_en-US" xlink:label="lab_us-gaap_WarrantMember_2F2CECF49A119494730FF226DBC89E6F" xlink:role="http://www.xbrl.org/2003/role/verboseLabel" xlink:type="resource" xml:lang="en-US">Exercise of common warrants</link:label>
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    <link:label id="lab_us-gaap_StockCompensationPlanMember_061C109703961B56FF07F226DBC8CCD3_terseLabel_en-US" xlink:label="lab_us-gaap_StockCompensationPlanMember_061C109703961B56FF07F226DBC8CCD3" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Shares available for future stock incentive awards</link:label>
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    <link:label id="lab_us-gaap_EmployeeStockOptionMember_135AC3B348321CB2AA79F226DBC8AD0F_verboseLabel_en-US" xlink:label="lab_us-gaap_EmployeeStockOptionMember_135AC3B348321CB2AA79F226DBC8AD0F" xlink:role="http://www.xbrl.org/2003/role/verboseLabel" xlink:type="resource" xml:lang="en-US">Exercise of outstanding common stock options</link:label>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_EmployeeStockOptionMember" xlink:label="loc_us-gaap_EmployeeStockOptionMember_135AC3B348321CB2AA79F226DBC8AD0F" xlink:type="locator" />
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    <link:label id="lab_us-gaap_ClassOfStockLineItems_FC4673B667ED498731D4F226DBC8E0B0_terseLabel_en-US" xlink:label="lab_us-gaap_ClassOfStockLineItems_FC4673B667ED498731D4F226DBC8E0B0" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Class of Stock [Line Items]</link:label>
    <link:label id="lab_us-gaap_ClassOfStockLineItems_FC4673B667ED498731D4F226DBC8E0B0_label_en-US" xlink:label="lab_us-gaap_ClassOfStockLineItems_FC4673B667ED498731D4F226DBC8E0B0" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Class of Stock [Line Items]</link:label>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_ClassOfStockLineItems" xlink:label="loc_us-gaap_ClassOfStockLineItems_FC4673B667ED498731D4F226DBC8E0B0" xlink:type="locator" />
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    <link:label id="lab_us-gaap_CommonStockCapitalSharesReservedForFutureIssuance_463579CA865EF38F5ADDF226DBC8EB13_terseLabel_en-US" xlink:label="lab_us-gaap_CommonStockCapitalSharesReservedForFutureIssuance_463579CA865EF38F5ADDF226DBC8EB13" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Total (in shares)</link:label>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_CommonStockCapitalSharesReservedForFutureIssuance" xlink:label="loc_us-gaap_CommonStockCapitalSharesReservedForFutureIssuance_463579CA865EF38F5ADDF226DBC8EB13" xlink:type="locator" />
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    <link:label id="lab_us-gaap_AvailableForSaleSecuritiesInUnrealizedLossPositionsQualitativeDisclosureNumberOfPositionsLessThanOneYear_71234F5F22AA1FE09578F226DC91F188_terseLabel_en-US" xlink:label="lab_us-gaap_AvailableForSaleSecuritiesInUnrealizedLossPositionsQualitativeDisclosureNumberOfPositionsLessThanOneYear_71234F5F22AA1FE09578F226DC91F188" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Number of positions in an unrealized loss position, less than 12 months</link:label>
    <link:label id="lab_us-gaap_AvailableForSaleSecuritiesInUnrealizedLossPositionsQualitativeDisclosureNumberOfPositionsLessThanOneYear_71234F5F22AA1FE09578F226DC91F188_label_en-US" xlink:label="lab_us-gaap_AvailableForSaleSecuritiesInUnrealizedLossPositionsQualitativeDisclosureNumberOfPositionsLessThanOneYear_71234F5F22AA1FE09578F226DC91F188" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Available-for-sale, Securities in Unrealized Loss Positions, Qualitative Disclosure, Number of Positions, Less than One Year</link:label>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_AvailableForSaleSecuritiesInUnrealizedLossPositionsQualitativeDisclosureNumberOfPositionsLessThanOneYear" xlink:label="loc_us-gaap_AvailableForSaleSecuritiesInUnrealizedLossPositionsQualitativeDisclosureNumberOfPositionsLessThanOneYear_71234F5F22AA1FE09578F226DC91F188" xlink:type="locator" />
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    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_AvailableforsaleSecuritiesInUnrealizedLossPositionsQualitativeDisclosureNumberOfPositions1" xlink:label="loc_us-gaap_AvailableforsaleSecuritiesInUnrealizedLossPositionsQualitativeDisclosureNumberOfPositions1_CDEA6265248548BE5545F226DC912D2A" xlink:type="locator" />
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    <link:label id="lab_us-gaap_ScheduleOfPropertyPlantAndEquipmentTable_7A41908F13BC191552FFF226DCA3247F_terseLabel_en-US" xlink:label="lab_us-gaap_ScheduleOfPropertyPlantAndEquipmentTable_7A41908F13BC191552FFF226DCA3247F" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Property, Plant and Equipment [Table]</link:label>
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    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_ScheduleOfPropertyPlantAndEquipmentTable" xlink:label="loc_us-gaap_ScheduleOfPropertyPlantAndEquipmentTable_7A41908F13BC191552FFF226DCA3247F" xlink:type="locator" />
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    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_PropertyPlantAndEquipmentTypeDomain" xlink:label="loc_us-gaap_PropertyPlantAndEquipmentTypeDomain_D5F7CE2702B5B8E61274F226DCA31D49" xlink:type="locator" />
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    <link:label id="lab_us-gaap_FurnitureAndFixturesMember_F141A28B7F4577499997F226DCA32F5A_verboseLabel_en-US" xlink:label="lab_us-gaap_FurnitureAndFixturesMember_F141A28B7F4577499997F226DCA32F5A" xlink:role="http://www.xbrl.org/2003/role/verboseLabel" xlink:type="resource" xml:lang="en-US">Furniture</link:label>
    <link:label id="lab_us-gaap_FurnitureAndFixturesMember_F141A28B7F4577499997F226DCA32F5A_label_en-US" xlink:label="lab_us-gaap_FurnitureAndFixturesMember_F141A28B7F4577499997F226DCA32F5A" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Furniture and Fixtures [Member]</link:label>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_FurnitureAndFixturesMember" xlink:label="loc_us-gaap_FurnitureAndFixturesMember_F141A28B7F4577499997F226DCA32F5A" xlink:type="locator" />
    <link:labelArc order="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_us-gaap_FurnitureAndFixturesMember_F141A28B7F4577499997F226DCA32F5A" xlink:to="lab_us-gaap_FurnitureAndFixturesMember_F141A28B7F4577499997F226DCA32F5A" xlink:type="arc" />
    <link:label id="lab_us-gaap_EquipmentMember_9B804D4E91E6EDF23BADF226DCA37F45_terseLabel_en-US" xlink:label="lab_us-gaap_EquipmentMember_9B804D4E91E6EDF23BADF226DCA37F45" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Equipment</link:label>
    <link:label id="lab_us-gaap_EquipmentMember_9B804D4E91E6EDF23BADF226DCA37F45_label_en-US" xlink:label="lab_us-gaap_EquipmentMember_9B804D4E91E6EDF23BADF226DCA37F45" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Equipment [Member]</link:label>
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    <link:label id="lab_us-gaap_OfficeEquipmentMember_19AD167BC592F9FE456AF226DCA388BC_verboseLabel_en-US" xlink:label="lab_us-gaap_OfficeEquipmentMember_19AD167BC592F9FE456AF226DCA388BC" xlink:role="http://www.xbrl.org/2003/role/verboseLabel" xlink:type="resource" xml:lang="en-US">Computer and office equipment</link:label>
    <link:label id="lab_us-gaap_OfficeEquipmentMember_19AD167BC592F9FE456AF226DCA388BC_label_en-US" xlink:label="lab_us-gaap_OfficeEquipmentMember_19AD167BC592F9FE456AF226DCA388BC" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Office Equipment [Member]</link:label>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_OfficeEquipmentMember" xlink:label="loc_us-gaap_OfficeEquipmentMember_19AD167BC592F9FE456AF226DCA388BC" xlink:type="locator" />
    <link:labelArc order="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_us-gaap_OfficeEquipmentMember_19AD167BC592F9FE456AF226DCA388BC" xlink:to="lab_us-gaap_OfficeEquipmentMember_19AD167BC592F9FE456AF226DCA388BC" xlink:type="arc" />
    <link:label id="lab_us-gaap_PropertyPlantAndEquipmentLineItems_FE572E293BAA03DB43E2F226DCA38EE5_terseLabel_en-US" xlink:label="lab_us-gaap_PropertyPlantAndEquipmentLineItems_FE572E293BAA03DB43E2F226DCA38EE5" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Property, Plant and Equipment [Line Items]</link:label>
    <link:label id="lab_us-gaap_PropertyPlantAndEquipmentLineItems_FE572E293BAA03DB43E2F226DCA38EE5_label_en-US" xlink:label="lab_us-gaap_PropertyPlantAndEquipmentLineItems_FE572E293BAA03DB43E2F226DCA38EE5" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Property, Plant and Equipment [Line Items]</link:label>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_PropertyPlantAndEquipmentLineItems" xlink:label="loc_us-gaap_PropertyPlantAndEquipmentLineItems_FE572E293BAA03DB43E2F226DCA38EE5" xlink:type="locator" />
    <link:labelArc order="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentLineItems_FE572E293BAA03DB43E2F226DCA38EE5" xlink:to="lab_us-gaap_PropertyPlantAndEquipmentLineItems_FE572E293BAA03DB43E2F226DCA38EE5" xlink:type="arc" />
    <link:label id="lab_us-gaap_PropertyPlantAndEquipmentUsefulLife_770007304E8620E2A55EF226DCA34B60_terseLabel_en-US" xlink:label="lab_us-gaap_PropertyPlantAndEquipmentUsefulLife_770007304E8620E2A55EF226DCA34B60" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Estimated useful life</link:label>
    <link:label id="lab_us-gaap_PropertyPlantAndEquipmentUsefulLife_770007304E8620E2A55EF226DCA34B60_label_en-US" xlink:label="lab_us-gaap_PropertyPlantAndEquipmentUsefulLife_770007304E8620E2A55EF226DCA34B60" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Property, Plant and Equipment, Useful Life</link:label>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_PropertyPlantAndEquipmentUsefulLife" xlink:label="loc_us-gaap_PropertyPlantAndEquipmentUsefulLife_770007304E8620E2A55EF226DCA34B60" xlink:type="locator" />
    <link:labelArc order="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentUsefulLife_770007304E8620E2A55EF226DCA34B60" xlink:to="lab_us-gaap_PropertyPlantAndEquipmentUsefulLife_770007304E8620E2A55EF226DCA34B60" xlink:type="arc" />
    <link:label id="lab_us-gaap_LongTermDebtByMaturityAbstract_5F76F939CC0BFF8A96B0FB8B61930A4E_terseLabel_en-US" xlink:label="lab_us-gaap_LongTermDebtByMaturityAbstract_5F76F939CC0BFF8A96B0FB8B61930A4E" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Year ended December 31,</link:label>
    <link:label id="lab_us-gaap_LongTermDebtByMaturityAbstract_5F76F939CC0BFF8A96B0FB8B61930A4E_label_en-US" xlink:label="lab_us-gaap_LongTermDebtByMaturityAbstract_5F76F939CC0BFF8A96B0FB8B61930A4E" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Long-term Debt, Fiscal Year Maturity [Abstract]</link:label>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_LongTermDebtByMaturityAbstract" xlink:label="loc_us-gaap_LongTermDebtByMaturityAbstract_5F76F939CC0BFF8A96B0FB8B61930A4E" xlink:type="locator" />
    <link:labelArc order="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_us-gaap_LongTermDebtByMaturityAbstract_5F76F939CC0BFF8A96B0FB8B61930A4E" xlink:to="lab_us-gaap_LongTermDebtByMaturityAbstract_5F76F939CC0BFF8A96B0FB8B61930A4E" xlink:type="arc" />
    <link:label id="lab_selb_LongTermDebtMaturitiesRepaymentsOfPrincipalAndInterestInNextTwelveMonths_4F8C88D4038F9BDE198AFB8B61942D85_terseLabel_en-US" xlink:label="lab_selb_LongTermDebtMaturitiesRepaymentsOfPrincipalAndInterestInNextTwelveMonths_4F8C88D4038F9BDE198AFB8B61942D85" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">2017</link:label>
    <link:label id="lab_selb_LongTermDebtMaturitiesRepaymentsOfPrincipalAndInterestInNextTwelveMonths_4F8C88D4038F9BDE198AFB8B61942D85_label_en-US" xlink:label="lab_selb_LongTermDebtMaturitiesRepaymentsOfPrincipalAndInterestInNextTwelveMonths_4F8C88D4038F9BDE198AFB8B61942D85" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Long-Term Debt, Maturities, Repayments Of Principal And Interest In Next Twelve Months</link:label>
    <link:label id="lab_selb_LongTermDebtMaturitiesRepaymentsOfPrincipalAndInterestInNextTwelveMonths_4F8C88D4038F9BDE198AFB8B61942D85_documentation_en-US" xlink:label="lab_selb_LongTermDebtMaturitiesRepaymentsOfPrincipalAndInterestInNextTwelveMonths_4F8C88D4038F9BDE198AFB8B61942D85" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:type="resource" xml:lang="en-US">Long-Term Debt, Maturities, Repayments Of Principal And Interest In Next Twelve Months</link:label>
    <link:loc xlink:href="selb-20161231.xsd#selb_LongTermDebtMaturitiesRepaymentsOfPrincipalAndInterestInNextTwelveMonths" xlink:label="loc_selb_LongTermDebtMaturitiesRepaymentsOfPrincipalAndInterestInNextTwelveMonths_4F8C88D4038F9BDE198AFB8B61942D85" xlink:type="locator" />
    <link:labelArc order="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_selb_LongTermDebtMaturitiesRepaymentsOfPrincipalAndInterestInNextTwelveMonths_4F8C88D4038F9BDE198AFB8B61942D85" xlink:to="lab_selb_LongTermDebtMaturitiesRepaymentsOfPrincipalAndInterestInNextTwelveMonths_4F8C88D4038F9BDE198AFB8B61942D85" xlink:type="arc" />
    <link:label id="lab_selb_LongTermDebtMaturitiesRepaymentsOfPrincipalAndInterestInYearTwo_6FF85A8977DA7B7141F8FB8B61947371_terseLabel_en-US" xlink:label="lab_selb_LongTermDebtMaturitiesRepaymentsOfPrincipalAndInterestInYearTwo_6FF85A8977DA7B7141F8FB8B61947371" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">2018</link:label>
    <link:label id="lab_selb_LongTermDebtMaturitiesRepaymentsOfPrincipalAndInterestInYearTwo_6FF85A8977DA7B7141F8FB8B61947371_label_en-US" xlink:label="lab_selb_LongTermDebtMaturitiesRepaymentsOfPrincipalAndInterestInYearTwo_6FF85A8977DA7B7141F8FB8B61947371" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Long-Term Debt, Maturities, Repayments Of Principal And Interest In Year Two</link:label>
    <link:label id="lab_selb_LongTermDebtMaturitiesRepaymentsOfPrincipalAndInterestInYearTwo_6FF85A8977DA7B7141F8FB8B61947371_documentation_en-US" xlink:label="lab_selb_LongTermDebtMaturitiesRepaymentsOfPrincipalAndInterestInYearTwo_6FF85A8977DA7B7141F8FB8B61947371" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:type="resource" xml:lang="en-US">Long-Term Debt, Maturities, Repayments Of Principal And Interest In Year Two</link:label>
    <link:loc xlink:href="selb-20161231.xsd#selb_LongTermDebtMaturitiesRepaymentsOfPrincipalAndInterestInYearTwo" xlink:label="loc_selb_LongTermDebtMaturitiesRepaymentsOfPrincipalAndInterestInYearTwo_6FF85A8977DA7B7141F8FB8B61947371" xlink:type="locator" />
    <link:labelArc order="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_selb_LongTermDebtMaturitiesRepaymentsOfPrincipalAndInterestInYearTwo_6FF85A8977DA7B7141F8FB8B61947371" xlink:to="lab_selb_LongTermDebtMaturitiesRepaymentsOfPrincipalAndInterestInYearTwo_6FF85A8977DA7B7141F8FB8B61947371" xlink:type="arc" />
    <link:label id="lab_selb_LongTermDebtMaturitiesRepaymentsOfPrincipalAndInterestInYearThree_23C921B538057BC864B2FB8B6194EAD0_terseLabel_en-US" xlink:label="lab_selb_LongTermDebtMaturitiesRepaymentsOfPrincipalAndInterestInYearThree_23C921B538057BC864B2FB8B6194EAD0" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">2019</link:label>
    <link:label id="lab_selb_LongTermDebtMaturitiesRepaymentsOfPrincipalAndInterestInYearThree_23C921B538057BC864B2FB8B6194EAD0_label_en-US" xlink:label="lab_selb_LongTermDebtMaturitiesRepaymentsOfPrincipalAndInterestInYearThree_23C921B538057BC864B2FB8B6194EAD0" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Long-Term Debt, Maturities, Repayments Of Principal And Interest In Year Three</link:label>
    <link:label id="lab_selb_LongTermDebtMaturitiesRepaymentsOfPrincipalAndInterestInYearThree_23C921B538057BC864B2FB8B6194EAD0_documentation_en-US" xlink:label="lab_selb_LongTermDebtMaturitiesRepaymentsOfPrincipalAndInterestInYearThree_23C921B538057BC864B2FB8B6194EAD0" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:type="resource" xml:lang="en-US">Long-Term Debt, Maturities, Repayments Of Principal And Interest In Year Three</link:label>
    <link:loc xlink:href="selb-20161231.xsd#selb_LongTermDebtMaturitiesRepaymentsOfPrincipalAndInterestInYearThree" xlink:label="loc_selb_LongTermDebtMaturitiesRepaymentsOfPrincipalAndInterestInYearThree_23C921B538057BC864B2FB8B6194EAD0" xlink:type="locator" />
    <link:labelArc order="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_selb_LongTermDebtMaturitiesRepaymentsOfPrincipalAndInterestInYearThree_23C921B538057BC864B2FB8B6194EAD0" xlink:to="lab_selb_LongTermDebtMaturitiesRepaymentsOfPrincipalAndInterestInYearThree_23C921B538057BC864B2FB8B6194EAD0" xlink:type="arc" />
    <link:label id="lab_selb_LongTermDebtMaturitiesTotalRepaymentsOfPrincipalAndInterest_ABE6CAF45878B372B50DFB8B6194A25C_totalLabel_en-US" xlink:label="lab_selb_LongTermDebtMaturitiesTotalRepaymentsOfPrincipalAndInterest_ABE6CAF45878B372B50DFB8B6194A25C" xlink:role="http://www.xbrl.org/2003/role/totalLabel" xlink:type="resource" xml:lang="en-US">Total minimum debt payments</link:label>
    <link:label id="lab_selb_LongTermDebtMaturitiesTotalRepaymentsOfPrincipalAndInterest_ABE6CAF45878B372B50DFB8B6194A25C_label_en-US" xlink:label="lab_selb_LongTermDebtMaturitiesTotalRepaymentsOfPrincipalAndInterest_ABE6CAF45878B372B50DFB8B6194A25C" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Long-Term Debt, Maturities, Total Repayments Of Principal And Interest</link:label>
    <link:label id="lab_selb_LongTermDebtMaturitiesTotalRepaymentsOfPrincipalAndInterest_ABE6CAF45878B372B50DFB8B6194A25C_documentation_en-US" xlink:label="lab_selb_LongTermDebtMaturitiesTotalRepaymentsOfPrincipalAndInterest_ABE6CAF45878B372B50DFB8B6194A25C" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:type="resource" xml:lang="en-US">Long-Term Debt, Maturities, Total Repayments Of Principal And Interest</link:label>
    <link:loc xlink:href="selb-20161231.xsd#selb_LongTermDebtMaturitiesTotalRepaymentsOfPrincipalAndInterest" xlink:label="loc_selb_LongTermDebtMaturitiesTotalRepaymentsOfPrincipalAndInterest_ABE6CAF45878B372B50DFB8B6194A25C" xlink:type="locator" />
    <link:labelArc order="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_selb_LongTermDebtMaturitiesTotalRepaymentsOfPrincipalAndInterest_ABE6CAF45878B372B50DFB8B6194A25C" xlink:to="lab_selb_LongTermDebtMaturitiesTotalRepaymentsOfPrincipalAndInterest_ABE6CAF45878B372B50DFB8B6194A25C" xlink:type="arc" />
    <link:label id="lab_selb_DebtInstrumentInterestPortion_DC171525FF923AEA97CEFB8B61940F64_negatedTerseLabel_en-US" xlink:label="lab_selb_DebtInstrumentInterestPortion_DC171525FF923AEA97CEFB8B61940F64" xlink:role="http://www.xbrl.org/2009/role/negatedTerseLabel" xlink:type="resource" xml:lang="en-US">Less: Amount representing interest</link:label>
    <link:label id="lab_selb_DebtInstrumentInterestPortion_DC171525FF923AEA97CEFB8B61940F64_label_en-US" xlink:label="lab_selb_DebtInstrumentInterestPortion_DC171525FF923AEA97CEFB8B61940F64" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Debt Instrument Interest Portion</link:label>
    <link:label id="lab_selb_DebtInstrumentInterestPortion_DC171525FF923AEA97CEFB8B61940F64_documentation_en-US" xlink:label="lab_selb_DebtInstrumentInterestPortion_DC171525FF923AEA97CEFB8B61940F64" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:type="resource" xml:lang="en-US">The interest portion of gross outstanding debt.</link:label>
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    <link:label id="lab_us-gaap_DebtInstrumentUnamortizedDiscountPremiumAndDebtIssuanceCostsNet_B354ED52468F4764650EFB8B619410B4_negatedTerseLabel_en-US" xlink:label="lab_us-gaap_DebtInstrumentUnamortizedDiscountPremiumAndDebtIssuanceCostsNet_B354ED52468F4764650EFB8B619410B4" xlink:role="http://www.xbrl.org/2009/role/negatedTerseLabel" xlink:type="resource" xml:lang="en-US">Less: Debt discount and deferred charges</link:label>
    <link:label id="lab_us-gaap_DebtInstrumentUnamortizedDiscountPremiumAndDebtIssuanceCostsNet_B354ED52468F4764650EFB8B619410B4_label_en-US" xlink:label="lab_us-gaap_DebtInstrumentUnamortizedDiscountPremiumAndDebtIssuanceCostsNet_B354ED52468F4764650EFB8B619410B4" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Debt Instrument, Unamortized Discount (Premium) and Debt Issuance Costs, Net</link:label>
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    <link:loc xlink:href="selb-20161231.xsd#selb_AdditionalPaymentForPreclinicalResearchForEachIndication" xlink:label="loc_selb_AdditionalPaymentForPreclinicalResearchForEachIndication_7376168BA417DE7850EFF226DB8FC89E" xlink:type="locator" />
    <link:labelArc order="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_selb_AdditionalPaymentForPreclinicalResearchForEachIndication_7376168BA417DE7850EFF226DB8FC89E" xlink:to="lab_selb_AdditionalPaymentForPreclinicalResearchForEachIndication_7376168BA417DE7850EFF226DB8FC89E" xlink:type="arc" />
    <link:label id="lab_selb_ProceedsFromCounterpartyExerciseOfOptionForAdditionalIndications_138681171BDE91654D24F226DB8F37C3_terseLabel_en-US" xlink:label="lab_selb_ProceedsFromCounterpartyExerciseOfOptionForAdditionalIndications_138681171BDE91654D24F226DB8F37C3" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Additional payments received upon exercise of option</link:label>
    <link:label id="lab_selb_ProceedsFromCounterpartyExerciseOfOptionForAdditionalIndications_138681171BDE91654D24F226DB8F37C3_label_en-US" xlink:label="lab_selb_ProceedsFromCounterpartyExerciseOfOptionForAdditionalIndications_138681171BDE91654D24F226DB8F37C3" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Proceeds From Counterparty Exercise Of Option For Additional Indications</link:label>
    <link:label id="lab_selb_ProceedsFromCounterpartyExerciseOfOptionForAdditionalIndications_138681171BDE91654D24F226DB8F37C3_documentation_en-US" xlink:label="lab_selb_ProceedsFromCounterpartyExerciseOfOptionForAdditionalIndications_138681171BDE91654D24F226DB8F37C3" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:type="resource" xml:lang="en-US">Proceeds From Counterparty Exercise Of Option For Additional Indications</link:label>
    <link:loc xlink:href="selb-20161231.xsd#selb_ProceedsFromCounterpartyExerciseOfOptionForAdditionalIndications" xlink:label="loc_selb_ProceedsFromCounterpartyExerciseOfOptionForAdditionalIndications_138681171BDE91654D24F226DB8F37C3" xlink:type="locator" />
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    <link:label id="lab_selb_PaymentAmountUponAchievementOfDefinedClinicalMilestones_2870A06B8C509D86A963F226DB8FD69A_verboseLabel_en-US" xlink:label="lab_selb_PaymentAmountUponAchievementOfDefinedClinicalMilestones_2870A06B8C509D86A963F226DB8FD69A" xlink:role="http://www.xbrl.org/2003/role/verboseLabel" xlink:type="resource" xml:lang="en-US">Additional payment upon attaining first milestone for celiac disease indication</link:label>
    <link:label id="lab_selb_PaymentAmountUponAchievementOfDefinedClinicalMilestones_2870A06B8C509D86A963F226DB8FD69A_label_en-US" xlink:label="lab_selb_PaymentAmountUponAchievementOfDefinedClinicalMilestones_2870A06B8C509D86A963F226DB8FD69A" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Payment Amount Upon Achievement Of Defined Clinical Milestones</link:label>
    <link:label id="lab_selb_PaymentAmountUponAchievementOfDefinedClinicalMilestones_2870A06B8C509D86A963F226DB8FD69A_documentation_en-US" xlink:label="lab_selb_PaymentAmountUponAchievementOfDefinedClinicalMilestones_2870A06B8C509D86A963F226DB8FD69A" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:type="resource" xml:lang="en-US">Represents information pertaining to payment amount upon achievement of defined clinical milestones.</link:label>
    <link:loc xlink:href="selb-20161231.xsd#selb_PaymentAmountUponAchievementOfDefinedClinicalMilestones" xlink:label="loc_selb_PaymentAmountUponAchievementOfDefinedClinicalMilestones_2870A06B8C509D86A963F226DB8FD69A" xlink:type="locator" />
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    <link:label id="lab_selb_AggregateAmountOfUpfrontAndMilestoneBasedPayments_87F56C7863AF053124B1F226DB8FA963_verboseLabel_en-US" xlink:label="lab_selb_AggregateAmountOfUpfrontAndMilestoneBasedPayments_87F56C7863AF053124B1F226DB8FA963" xlink:role="http://www.xbrl.org/2003/role/verboseLabel" xlink:type="resource" xml:lang="en-US">Aggregate payments under Sanofi Agreement</link:label>
    <link:label id="lab_selb_AggregateAmountOfUpfrontAndMilestoneBasedPayments_87F56C7863AF053124B1F226DB8FA963_label_en-US" xlink:label="lab_selb_AggregateAmountOfUpfrontAndMilestoneBasedPayments_87F56C7863AF053124B1F226DB8FA963" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Aggregate Amount Of Upfront And Milestone Based Payments</link:label>
    <link:label id="lab_selb_AggregateAmountOfUpfrontAndMilestoneBasedPayments_87F56C7863AF053124B1F226DB8FA963_documentation_en-US" xlink:label="lab_selb_AggregateAmountOfUpfrontAndMilestoneBasedPayments_87F56C7863AF053124B1F226DB8FA963" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:type="resource" xml:lang="en-US">Represents information pertaining to aggregate amount of upfront and milestone based payments.</link:label>
    <link:loc xlink:href="selb-20161231.xsd#selb_AggregateAmountOfUpfrontAndMilestoneBasedPayments" xlink:label="loc_selb_AggregateAmountOfUpfrontAndMilestoneBasedPayments_87F56C7863AF053124B1F226DB8FA963" xlink:type="locator" />
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    <link:label id="lab_selb_InitialPeriodToCompleteResearchObligations_252EE40A986E0B582FD7F226DB8F2D80_terseLabel_en-US" xlink:label="lab_selb_InitialPeriodToCompleteResearchObligations_252EE40A986E0B582FD7F226DB8F2D80" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Initial period to complete research obligations</link:label>
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    <link:loc xlink:href="selb-20161231.xsd#selb_InitialPeriodToCompleteResearchObligations" xlink:label="loc_selb_InitialPeriodToCompleteResearchObligations_252EE40A986E0B582FD7F226DB8F2D80" xlink:type="locator" />
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    <link:label id="lab_us-gaap_ResearchAndDevelopmentArrangementContractToPerformForOthersCompensationEarned_81BBC805781C9CD34287F226DB8F4F87_netLabel_en-US" xlink:label="lab_us-gaap_ResearchAndDevelopmentArrangementContractToPerformForOthersCompensationEarned_81BBC805781C9CD34287F226DB8F4F87" xlink:role="http://www.xbrl.org/2009/role/netLabel" xlink:type="resource" xml:lang="en-US">Revenue</link:label>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_ResearchAndDevelopmentArrangementContractToPerformForOthersCompensationEarned" xlink:label="loc_us-gaap_ResearchAndDevelopmentArrangementContractToPerformForOthersCompensationEarned_81BBC805781C9CD34287F226DB8F4F87" xlink:type="locator" />
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    <link:label id="lab_us-gaap_PropertyPlantAndEquipmentDisclosureTextBlock_426D34754D151CCF58F4F226DC6D3611_terseLabel_en-US" xlink:label="lab_us-gaap_PropertyPlantAndEquipmentDisclosureTextBlock_426D34754D151CCF58F4F226DC6D3611" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Property and Equipment</link:label>
    <link:label id="lab_us-gaap_PropertyPlantAndEquipmentDisclosureTextBlock_426D34754D151CCF58F4F226DC6D3611_label_en-US" xlink:label="lab_us-gaap_PropertyPlantAndEquipmentDisclosureTextBlock_426D34754D151CCF58F4F226DC6D3611" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Property, Plant and Equipment Disclosure [Text Block]</link:label>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_PropertyPlantAndEquipmentDisclosureTextBlock" xlink:label="loc_us-gaap_PropertyPlantAndEquipmentDisclosureTextBlock_426D34754D151CCF58F4F226DC6D3611" xlink:type="locator" />
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    <link:label id="lab_selb_TechnologyLicenseAgreementsTextBlock_6CF603220C7AE0B33080F226DB145C82_terseLabel_en-US" xlink:label="lab_selb_TechnologyLicenseAgreementsTextBlock_6CF603220C7AE0B33080F226DB145C82" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Technology License Agreements</link:label>
    <link:label id="lab_selb_TechnologyLicenseAgreementsTextBlock_6CF603220C7AE0B33080F226DB145C82_label_en-US" xlink:label="lab_selb_TechnologyLicenseAgreementsTextBlock_6CF603220C7AE0B33080F226DB145C82" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Technology License Agreements [Text Block]</link:label>
    <link:label id="lab_selb_TechnologyLicenseAgreementsTextBlock_6CF603220C7AE0B33080F226DB145C82_documentation_en-US" xlink:label="lab_selb_TechnologyLicenseAgreementsTextBlock_6CF603220C7AE0B33080F226DB145C82" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:type="resource" xml:lang="en-US">The entire disclosure for technology license agreements.</link:label>
    <link:loc xlink:href="selb-20161231.xsd#selb_TechnologyLicenseAgreementsTextBlock" xlink:label="loc_selb_TechnologyLicenseAgreementsTextBlock_6CF603220C7AE0B33080F226DB145C82" xlink:type="locator" />
    <link:labelArc order="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_selb_TechnologyLicenseAgreementsTextBlock_6CF603220C7AE0B33080F226DB145C82" xlink:to="lab_selb_TechnologyLicenseAgreementsTextBlock_6CF603220C7AE0B33080F226DB145C82" xlink:type="arc" />
    <link:label id="lab_selb_OtherResearchAndCollaborationAgreementsMember_3D84F00A934AD2181666F226DB78B42F_terseLabel_en-US" xlink:label="lab_selb_OtherResearchAndCollaborationAgreementsMember_3D84F00A934AD2181666F226DB78B42F" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Other Research And Collaboration Agreements</link:label>
    <link:label id="lab_selb_OtherResearchAndCollaborationAgreementsMember_3D84F00A934AD2181666F226DB78B42F_label_en-US" xlink:label="lab_selb_OtherResearchAndCollaborationAgreementsMember_3D84F00A934AD2181666F226DB78B42F" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Other Research And Collaboration Agreements [Member]</link:label>
    <link:label id="lab_selb_OtherResearchAndCollaborationAgreementsMember_3D84F00A934AD2181666F226DB78B42F_documentation_en-US" xlink:label="lab_selb_OtherResearchAndCollaborationAgreementsMember_3D84F00A934AD2181666F226DB78B42F" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:type="resource" xml:lang="en-US">Represents information pertaining to other research and collaboration agreements.</link:label>
    <link:loc xlink:href="selb-20161231.xsd#selb_OtherResearchAndCollaborationAgreementsMember" xlink:label="loc_selb_OtherResearchAndCollaborationAgreementsMember_3D84F00A934AD2181666F226DB78B42F" xlink:type="locator" />
    <link:labelArc order="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_selb_OtherResearchAndCollaborationAgreementsMember_3D84F00A934AD2181666F226DB78B42F" xlink:to="lab_selb_OtherResearchAndCollaborationAgreementsMember_3D84F00A934AD2181666F226DB78B42F" xlink:type="arc" />
    <link:label id="lab_us-gaap_ConsolidationPolicyTextBlock_ECC7E2A4CFDDD76CD6B71025E7A190DE_terseLabel_en-US" xlink:label="lab_us-gaap_ConsolidationPolicyTextBlock_ECC7E2A4CFDDD76CD6B71025E7A190DE" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Principles of Consolidation</link:label>
    <link:label id="lab_us-gaap_ConsolidationPolicyTextBlock_ECC7E2A4CFDDD76CD6B71025E7A190DE_label_en-US" xlink:label="lab_us-gaap_ConsolidationPolicyTextBlock_ECC7E2A4CFDDD76CD6B71025E7A190DE" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Consolidation, Policy [Policy Text Block]</link:label>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_ConsolidationPolicyTextBlock" xlink:label="loc_us-gaap_ConsolidationPolicyTextBlock_ECC7E2A4CFDDD76CD6B71025E7A190DE" xlink:type="locator" />
    <link:labelArc order="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_us-gaap_ConsolidationPolicyTextBlock_ECC7E2A4CFDDD76CD6B71025E7A190DE" xlink:to="lab_us-gaap_ConsolidationPolicyTextBlock_ECC7E2A4CFDDD76CD6B71025E7A190DE" xlink:type="arc" />
    <link:label id="lab_us-gaap_ForeignCurrencyTransactionsAndTranslationsPolicyTextBlock_10450896D92658DE49DE1025E7A2C1BF_terseLabel_en-US" xlink:label="lab_us-gaap_ForeignCurrencyTransactionsAndTranslationsPolicyTextBlock_10450896D92658DE49DE1025E7A2C1BF" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Foreign Currency</link:label>
    <link:label id="lab_us-gaap_ForeignCurrencyTransactionsAndTranslationsPolicyTextBlock_10450896D92658DE49DE1025E7A2C1BF_label_en-US" xlink:label="lab_us-gaap_ForeignCurrencyTransactionsAndTranslationsPolicyTextBlock_10450896D92658DE49DE1025E7A2C1BF" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Foreign Currency Transactions and Translations Policy [Policy Text Block]</link:label>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_ForeignCurrencyTransactionsAndTranslationsPolicyTextBlock" xlink:label="loc_us-gaap_ForeignCurrencyTransactionsAndTranslationsPolicyTextBlock_10450896D92658DE49DE1025E7A2C1BF" xlink:type="locator" />
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    <link:label id="lab_us-gaap_UseOfEstimates_ACCD8EA276F88C9C70AB1025E7A2C459_terseLabel_en-US" xlink:label="lab_us-gaap_UseOfEstimates_ACCD8EA276F88C9C70AB1025E7A2C459" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Use of Estimates</link:label>
    <link:label id="lab_us-gaap_UseOfEstimates_ACCD8EA276F88C9C70AB1025E7A2C459_label_en-US" xlink:label="lab_us-gaap_UseOfEstimates_ACCD8EA276F88C9C70AB1025E7A2C459" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Use of Estimates, Policy [Policy Text Block]</link:label>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_UseOfEstimates" xlink:label="loc_us-gaap_UseOfEstimates_ACCD8EA276F88C9C70AB1025E7A2C459" xlink:type="locator" />
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    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_SegmentReportingPolicyPolicyTextBlock" xlink:label="loc_us-gaap_SegmentReportingPolicyPolicyTextBlock_9CBF532179614651D2511025E7A2327B" xlink:type="locator" />
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    <link:label id="lab_us-gaap_StockholdersEquityPolicyTextBlock_EBA7B7AB057403C1EA821025E7A23AB6_terseLabel_en-US" xlink:label="lab_us-gaap_StockholdersEquityPolicyTextBlock_EBA7B7AB057403C1EA821025E7A23AB6" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Reverse stock split and Preferred stock</link:label>
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    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_StockholdersEquityPolicyTextBlock" xlink:label="loc_us-gaap_StockholdersEquityPolicyTextBlock_EBA7B7AB057403C1EA821025E7A23AB6" xlink:type="locator" />
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    <link:label id="lab_us-gaap_ConcentrationRiskCreditRisk_068179BF3584808843C61025E7A241A2_terseLabel_en-US" xlink:label="lab_us-gaap_ConcentrationRiskCreditRisk_068179BF3584808843C61025E7A241A2" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Concentrations of Credit Risk and Off-Balance Sheet Risk</link:label>
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    <link:label id="lab_us-gaap_PropertyPlantAndEquipmentPolicyTextBlock_0592D6954BF71160057F1025E7A30963_terseLabel_en-US" xlink:label="lab_us-gaap_PropertyPlantAndEquipmentPolicyTextBlock_0592D6954BF71160057F1025E7A30963" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Property and Equipment</link:label>
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    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_ImpairmentOrDisposalOfLongLivedAssetsPolicyTextBlock" xlink:label="loc_us-gaap_ImpairmentOrDisposalOfLongLivedAssetsPolicyTextBlock_A159C798085E22E8960D1025E7A408F9" xlink:type="locator" />
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    <link:label id="lab_us-gaap_DebtPolicyTextBlock_5AB115E798141D5B13ED1025E7A446C1_terseLabel_en-US" xlink:label="lab_us-gaap_DebtPolicyTextBlock_5AB115E798141D5B13ED1025E7A446C1" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Debt Issuance Costs</link:label>
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    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_DebtPolicyTextBlock" xlink:label="loc_us-gaap_DebtPolicyTextBlock_5AB115E798141D5B13ED1025E7A446C1" xlink:type="locator" />
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    <link:label id="lab_us-gaap_ComprehensiveIncomePolicyPolicyTextBlock_CBE520F21A433825000E1025E7A46D56_terseLabel_en-US" xlink:label="lab_us-gaap_ComprehensiveIncomePolicyPolicyTextBlock_CBE520F21A433825000E1025E7A46D56" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Accumulated Other Comprehensive Income (Loss) and Comprehensive Loss</link:label>
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    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_ComprehensiveIncomePolicyPolicyTextBlock" xlink:label="loc_us-gaap_ComprehensiveIncomePolicyPolicyTextBlock_CBE520F21A433825000E1025E7A46D56" xlink:type="locator" />
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    <link:label id="lab_us-gaap_RevenueRecognitionPolicyTextBlock_918688B7F7ED21E0DDF41025E7A4AE13_terseLabel_en-US" xlink:label="lab_us-gaap_RevenueRecognitionPolicyTextBlock_918688B7F7ED21E0DDF41025E7A4AE13" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Revenue Recognition</link:label>
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    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_RevenueRecognitionPolicyTextBlock" xlink:label="loc_us-gaap_RevenueRecognitionPolicyTextBlock_918688B7F7ED21E0DDF41025E7A4AE13" xlink:type="locator" />
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    <link:label id="lab_us-gaap_CollaborativeArrangementAccountingPolicy_B5BA142797CA93DDCF501025E7A4E6A0_terseLabel_en-US" xlink:label="lab_us-gaap_CollaborativeArrangementAccountingPolicy_B5BA142797CA93DDCF501025E7A4E6A0" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Collaboration Revenue</link:label>
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    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_CollaborativeArrangementAccountingPolicy" xlink:label="loc_us-gaap_CollaborativeArrangementAccountingPolicy_B5BA142797CA93DDCF501025E7A4E6A0" xlink:type="locator" />
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    <link:label id="lab_selb_RevenueRecognitionGrantRevenuePolicyTextBlock_706ACB8E84662316221C1025E7A46DC8_terseLabel_en-US" xlink:label="lab_selb_RevenueRecognitionGrantRevenuePolicyTextBlock_706ACB8E84662316221C1025E7A46DC8" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Grant Agreements</link:label>
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    <link:label id="lab_us-gaap_ShareBasedCompensationOptionAndIncentivePlansPolicy_43FD6CEFD77E616EA9621025E7A4A80A_terseLabel_en-US" xlink:label="lab_us-gaap_ShareBasedCompensationOptionAndIncentivePlansPolicy_43FD6CEFD77E616EA9621025E7A4A80A" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Stock-Based Compensation</link:label>
    <link:label id="lab_us-gaap_ShareBasedCompensationOptionAndIncentivePlansPolicy_43FD6CEFD77E616EA9621025E7A4A80A_label_en-US" xlink:label="lab_us-gaap_ShareBasedCompensationOptionAndIncentivePlansPolicy_43FD6CEFD77E616EA9621025E7A4A80A" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Share-based Compensation, Option and Incentive Plans Policy [Policy Text Block]</link:label>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_ShareBasedCompensationOptionAndIncentivePlansPolicy" xlink:label="loc_us-gaap_ShareBasedCompensationOptionAndIncentivePlansPolicy_43FD6CEFD77E616EA9621025E7A4A80A" xlink:type="locator" />
    <link:labelArc order="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_us-gaap_ShareBasedCompensationOptionAndIncentivePlansPolicy_43FD6CEFD77E616EA9621025E7A4A80A" xlink:to="lab_us-gaap_ShareBasedCompensationOptionAndIncentivePlansPolicy_43FD6CEFD77E616EA9621025E7A4A80A" xlink:type="arc" />
    <link:label id="lab_us-gaap_EarningsPerSharePolicyTextBlock_D281D39B62A0D899E0B21025E7A4C1D5_terseLabel_en-US" xlink:label="lab_us-gaap_EarningsPerSharePolicyTextBlock_D281D39B62A0D899E0B21025E7A4C1D5" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Net Loss Per Share</link:label>
    <link:label id="lab_us-gaap_EarningsPerSharePolicyTextBlock_D281D39B62A0D899E0B21025E7A4C1D5_label_en-US" xlink:label="lab_us-gaap_EarningsPerSharePolicyTextBlock_D281D39B62A0D899E0B21025E7A4C1D5" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Earnings Per Share, Policy [Policy Text Block]</link:label>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_EarningsPerSharePolicyTextBlock" xlink:label="loc_us-gaap_EarningsPerSharePolicyTextBlock_D281D39B62A0D899E0B21025E7A4C1D5" xlink:type="locator" />
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    <link:label id="lab_selb_DeferredRentPolicyTextBlock_1910169C2D0CEEE354EF1025E7A55B8F_terseLabel_en-US" xlink:label="lab_selb_DeferredRentPolicyTextBlock_1910169C2D0CEEE354EF1025E7A55B8F" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Deferred Rent</link:label>
    <link:label id="lab_selb_DeferredRentPolicyTextBlock_1910169C2D0CEEE354EF1025E7A55B8F_label_en-US" xlink:label="lab_selb_DeferredRentPolicyTextBlock_1910169C2D0CEEE354EF1025E7A55B8F" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Deferred Rent [Policy Text Block]</link:label>
    <link:label id="lab_selb_DeferredRentPolicyTextBlock_1910169C2D0CEEE354EF1025E7A55B8F_documentation_en-US" xlink:label="lab_selb_DeferredRentPolicyTextBlock_1910169C2D0CEEE354EF1025E7A55B8F" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:type="resource" xml:lang="en-US">Disclosure of accounting policy for deferred rent.</link:label>
    <link:loc xlink:href="selb-20161231.xsd#selb_DeferredRentPolicyTextBlock" xlink:label="loc_selb_DeferredRentPolicyTextBlock_1910169C2D0CEEE354EF1025E7A55B8F" xlink:type="locator" />
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    <link:label id="lab_us-gaap_ContingentLiabilityReserveEstimatePolicy_53BFA9ACBEF9CF825C9E1025E7A5F78A_terseLabel_en-US" xlink:label="lab_us-gaap_ContingentLiabilityReserveEstimatePolicy_53BFA9ACBEF9CF825C9E1025E7A5F78A" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Contingent Liabilities</link:label>
    <link:label id="lab_us-gaap_ContingentLiabilityReserveEstimatePolicy_53BFA9ACBEF9CF825C9E1025E7A5F78A_label_en-US" xlink:label="lab_us-gaap_ContingentLiabilityReserveEstimatePolicy_53BFA9ACBEF9CF825C9E1025E7A5F78A" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Contingent Liability Reserve Estimate, Policy [Policy Text Block]</link:label>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_ContingentLiabilityReserveEstimatePolicy" xlink:label="loc_us-gaap_ContingentLiabilityReserveEstimatePolicy_53BFA9ACBEF9CF825C9E1025E7A5F78A" xlink:type="locator" />
    <link:labelArc order="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_us-gaap_ContingentLiabilityReserveEstimatePolicy_53BFA9ACBEF9CF825C9E1025E7A5F78A" xlink:to="lab_us-gaap_ContingentLiabilityReserveEstimatePolicy_53BFA9ACBEF9CF825C9E1025E7A5F78A" xlink:type="arc" />
    <link:label id="lab_us-gaap_NewAccountingPronouncementsPolicyPolicyTextBlock_23BB9393D4BCBF9D6B461025E7A561FC_terseLabel_en-US" xlink:label="lab_us-gaap_NewAccountingPronouncementsPolicyPolicyTextBlock_23BB9393D4BCBF9D6B461025E7A561FC" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Recent Accounting Pronouncements</link:label>
    <link:label id="lab_us-gaap_NewAccountingPronouncementsPolicyPolicyTextBlock_23BB9393D4BCBF9D6B461025E7A561FC_label_en-US" xlink:label="lab_us-gaap_NewAccountingPronouncementsPolicyPolicyTextBlock_23BB9393D4BCBF9D6B461025E7A561FC" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">New Accounting Pronouncements, Policy [Policy Text Block]</link:label>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_NewAccountingPronouncementsPolicyPolicyTextBlock" xlink:label="loc_us-gaap_NewAccountingPronouncementsPolicyPolicyTextBlock_23BB9393D4BCBF9D6B461025E7A561FC" xlink:type="locator" />
    <link:labelArc order="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_us-gaap_NewAccountingPronouncementsPolicyPolicyTextBlock_23BB9393D4BCBF9D6B461025E7A561FC" xlink:to="lab_us-gaap_NewAccountingPronouncementsPolicyPolicyTextBlock_23BB9393D4BCBF9D6B461025E7A561FC" xlink:type="arc" />
    <link:label id="lab_selb_NationalInstitutesOfHealthGrantAgreementMember_B80A97A00FB4EC61948AF226DB706320_terseLabel_en-US" xlink:label="lab_selb_NationalInstitutesOfHealthGrantAgreementMember_B80A97A00FB4EC61948AF226DB706320" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">NIH</link:label>
    <link:label id="lab_selb_NationalInstitutesOfHealthGrantAgreementMember_B80A97A00FB4EC61948AF226DB706320_label_en-US" xlink:label="lab_selb_NationalInstitutesOfHealthGrantAgreementMember_B80A97A00FB4EC61948AF226DB706320" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">National Institutes Of Health Grant Agreement [Member]</link:label>
    <link:label id="lab_selb_NationalInstitutesOfHealthGrantAgreementMember_B80A97A00FB4EC61948AF226DB706320_documentation_en-US" xlink:label="lab_selb_NationalInstitutesOfHealthGrantAgreementMember_B80A97A00FB4EC61948AF226DB706320" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:type="resource" xml:lang="en-US">Represents information pertaining to national institutes of health grant agreement.</link:label>
    <link:loc xlink:href="selb-20161231.xsd#selb_NationalInstitutesOfHealthGrantAgreementMember" xlink:label="loc_selb_NationalInstitutesOfHealthGrantAgreementMember_B80A97A00FB4EC61948AF226DB706320" xlink:type="locator" />
    <link:labelArc order="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_selb_NationalInstitutesOfHealthGrantAgreementMember_B80A97A00FB4EC61948AF226DB706320" xlink:to="lab_selb_NationalInstitutesOfHealthGrantAgreementMember_B80A97A00FB4EC61948AF226DB706320" xlink:type="arc" />
    <link:label id="lab_us-gaap_CapitalizedCostsOfUnprovedPropertiesExcludedFromAmortizationByPropertyOrProjectAxis_E06684FF254BFAEC884DF226DB70441F_terseLabel_en-US" xlink:label="lab_us-gaap_CapitalizedCostsOfUnprovedPropertiesExcludedFromAmortizationByPropertyOrProjectAxis_E06684FF254BFAEC884DF226DB70441F" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Project [Axis]</link:label>
    <link:label id="lab_us-gaap_CapitalizedCostsOfUnprovedPropertiesExcludedFromAmortizationByPropertyOrProjectAxis_E06684FF254BFAEC884DF226DB70441F_label_en-US" xlink:label="lab_us-gaap_CapitalizedCostsOfUnprovedPropertiesExcludedFromAmortizationByPropertyOrProjectAxis_E06684FF254BFAEC884DF226DB70441F" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Project [Axis]</link:label>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_CapitalizedCostsOfUnprovedPropertiesExcludedFromAmortizationByPropertyOrProjectAxis" xlink:label="loc_us-gaap_CapitalizedCostsOfUnprovedPropertiesExcludedFromAmortizationByPropertyOrProjectAxis_E06684FF254BFAEC884DF226DB70441F" xlink:type="locator" />
    <link:labelArc order="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_us-gaap_CapitalizedCostsOfUnprovedPropertiesExcludedFromAmortizationByPropertyOrProjectAxis_E06684FF254BFAEC884DF226DB70441F" xlink:to="lab_us-gaap_CapitalizedCostsOfUnprovedPropertiesExcludedFromAmortizationByPropertyOrProjectAxis_E06684FF254BFAEC884DF226DB70441F" xlink:type="arc" />
    <link:label id="lab_us-gaap_ProjectMember_DB366431A0D028566478F226DB70A19C_terseLabel_en-US" xlink:label="lab_us-gaap_ProjectMember_DB366431A0D028566478F226DB70A19C" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Project [Domain]</link:label>
    <link:label id="lab_us-gaap_ProjectMember_DB366431A0D028566478F226DB70A19C_label_en-US" xlink:label="lab_us-gaap_ProjectMember_DB366431A0D028566478F226DB70A19C" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Project [Domain]</link:label>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_ProjectMember" xlink:label="loc_us-gaap_ProjectMember_DB366431A0D028566478F226DB70A19C" xlink:type="locator" />
    <link:labelArc order="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_us-gaap_ProjectMember_DB366431A0D028566478F226DB70A19C" xlink:to="lab_us-gaap_ProjectMember_DB366431A0D028566478F226DB70A19C" xlink:type="arc" />
    <link:label id="lab_selb_FirstGrantMember_3EEF4BF55875EC7E8E5CF226DB70A3E5_terseLabel_en-US" xlink:label="lab_selb_FirstGrantMember_3EEF4BF55875EC7E8E5CF226DB70A3E5" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">First Grant</link:label>
    <link:label id="lab_selb_FirstGrantMember_3EEF4BF55875EC7E8E5CF226DB70A3E5_label_en-US" xlink:label="lab_selb_FirstGrantMember_3EEF4BF55875EC7E8E5CF226DB70A3E5" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">First Grant [Member]</link:label>
    <link:label id="lab_selb_FirstGrantMember_3EEF4BF55875EC7E8E5CF226DB70A3E5_documentation_en-US" xlink:label="lab_selb_FirstGrantMember_3EEF4BF55875EC7E8E5CF226DB70A3E5" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:type="resource" xml:lang="en-US">Represents information pertaining to first grant under NIH.</link:label>
    <link:loc xlink:href="selb-20161231.xsd#selb_FirstGrantMember" xlink:label="loc_selb_FirstGrantMember_3EEF4BF55875EC7E8E5CF226DB70A3E5" xlink:type="locator" />
    <link:labelArc order="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_selb_FirstGrantMember_3EEF4BF55875EC7E8E5CF226DB70A3E5" xlink:to="lab_selb_FirstGrantMember_3EEF4BF55875EC7E8E5CF226DB70A3E5" xlink:type="arc" />
    <link:label id="lab_selb_SecondGrantMember_660C176B2CD11D0A2E44F226DB706231_terseLabel_en-US" xlink:label="lab_selb_SecondGrantMember_660C176B2CD11D0A2E44F226DB706231" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Second Grant</link:label>
    <link:label id="lab_selb_SecondGrantMember_660C176B2CD11D0A2E44F226DB706231_label_en-US" xlink:label="lab_selb_SecondGrantMember_660C176B2CD11D0A2E44F226DB706231" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Second Grant [Member]</link:label>
    <link:label id="lab_selb_SecondGrantMember_660C176B2CD11D0A2E44F226DB706231_documentation_en-US" xlink:label="lab_selb_SecondGrantMember_660C176B2CD11D0A2E44F226DB706231" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:type="resource" xml:lang="en-US">Represents information pertaining to second grant under NIH.</link:label>
    <link:loc xlink:href="selb-20161231.xsd#selb_SecondGrantMember" xlink:label="loc_selb_SecondGrantMember_660C176B2CD11D0A2E44F226DB706231" xlink:type="locator" />
    <link:labelArc order="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_selb_SecondGrantMember_660C176B2CD11D0A2E44F226DB706231" xlink:to="lab_selb_SecondGrantMember_660C176B2CD11D0A2E44F226DB706231" xlink:type="arc" />
    <link:label id="lab_selb_NumberOfGrants_ECDB157899608ABC4CBBF226DB70834F_terseLabel_en-US" xlink:label="lab_selb_NumberOfGrants_ECDB157899608ABC4CBBF226DB70834F" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Number of grants</link:label>
    <link:label id="lab_selb_NumberOfGrants_ECDB157899608ABC4CBBF226DB70834F_label_en-US" xlink:label="lab_selb_NumberOfGrants_ECDB157899608ABC4CBBF226DB70834F" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Number Of Grants</link:label>
    <link:label id="lab_selb_NumberOfGrants_ECDB157899608ABC4CBBF226DB70834F_documentation_en-US" xlink:label="lab_selb_NumberOfGrants_ECDB157899608ABC4CBBF226DB70834F" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:type="resource" xml:lang="en-US">Represents information pertaining to number of grants.</link:label>
    <link:loc xlink:href="selb-20161231.xsd#selb_NumberOfGrants" xlink:label="loc_selb_NumberOfGrants_ECDB157899608ABC4CBBF226DB70834F" xlink:type="locator" />
    <link:labelArc order="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_selb_NumberOfGrants_ECDB157899608ABC4CBBF226DB70834F" xlink:to="lab_selb_NumberOfGrants_ECDB157899608ABC4CBBF226DB70834F" xlink:type="arc" />
    <link:label id="lab_us-gaap_StatementOfFinancialPositionAbstract_767777DCC8BF4AF3CF732F0CF5F974FD_label_en-US" xlink:label="lab_us-gaap_StatementOfFinancialPositionAbstract_767777DCC8BF4AF3CF732F0CF5F974FD" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Statement of Financial Position [Abstract]</link:label>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_StatementOfFinancialPositionAbstract" xlink:label="loc_us-gaap_StatementOfFinancialPositionAbstract_767777DCC8BF4AF3CF732F0CF5F974FD" xlink:type="locator" />
    <link:labelArc order="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_us-gaap_StatementOfFinancialPositionAbstract_767777DCC8BF4AF3CF732F0CF5F974FD" xlink:to="lab_us-gaap_StatementOfFinancialPositionAbstract_767777DCC8BF4AF3CF732F0CF5F974FD" xlink:type="arc" />
    <link:label id="lab_selb_SeriesARedeemableConvertiblePreferredStockMember_557F6A30189226D5F47B2F0CF5FA4251_netLabel_en-US" xlink:label="lab_selb_SeriesARedeemableConvertiblePreferredStockMember_557F6A30189226D5F47B2F0CF5FA4251" xlink:role="http://www.xbrl.org/2009/role/netLabel" xlink:type="resource" xml:lang="en-US">Series A redeemable convertible preferred stock</link:label>
    <link:loc xlink:href="selb-20161231.xsd#selb_SeriesARedeemableConvertiblePreferredStockMember" xlink:label="loc_selb_SeriesARedeemableConvertiblePreferredStockMember_557F6A30189226D5F47B2F0CF5FA4251" xlink:type="locator" />
    <link:labelArc order="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_selb_SeriesARedeemableConvertiblePreferredStockMember_557F6A30189226D5F47B2F0CF5FA4251" xlink:to="lab_selb_SeriesARedeemableConvertiblePreferredStockMember_557F6A30189226D5F47B2F0CF5FA4251" xlink:type="arc" />
    <link:label id="lab_selb_SeriesBRedeemableConvertiblePreferredStockMember_239D762AB6DC3567BA2F2F0CF5FA3813_netLabel_en-US" xlink:label="lab_selb_SeriesBRedeemableConvertiblePreferredStockMember_239D762AB6DC3567BA2F2F0CF5FA3813" xlink:role="http://www.xbrl.org/2009/role/netLabel" xlink:type="resource" xml:lang="en-US">Series B redeemable convertible preferred stock</link:label>
    <link:loc xlink:href="selb-20161231.xsd#selb_SeriesBRedeemableConvertiblePreferredStockMember" xlink:label="loc_selb_SeriesBRedeemableConvertiblePreferredStockMember_239D762AB6DC3567BA2F2F0CF5FA3813" xlink:type="locator" />
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    <link:label id="lab_selb_SeriesCRedeemableConvertiblePreferredStockMember_1ED4D28FA9FEDA9B397E2F0CF5FA2119_netLabel_en-US" xlink:label="lab_selb_SeriesCRedeemableConvertiblePreferredStockMember_1ED4D28FA9FEDA9B397E2F0CF5FA2119" xlink:role="http://www.xbrl.org/2009/role/netLabel" xlink:type="resource" xml:lang="en-US">Series C redeemable convertible preferred stock</link:label>
    <link:loc xlink:href="selb-20161231.xsd#selb_SeriesCRedeemableConvertiblePreferredStockMember" xlink:label="loc_selb_SeriesCRedeemableConvertiblePreferredStockMember_1ED4D28FA9FEDA9B397E2F0CF5FA2119" xlink:type="locator" />
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    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationsRecurringBasisLiabilityValue" xlink:label="loc_us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationsRecurringBasisLiabilityValue_0E520CCBFEFA0E057460F226DC71A1FA" xlink:type="locator" />
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    <link:label id="lab_us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisLiabilityIssues_64CF26CC1716405EB9A8F226DC71597B_terseLabel_en-US" xlink:label="lab_us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisLiabilityIssues_64CF26CC1716405EB9A8F226DC71597B" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Fair value of warrants issued</link:label>
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    <link:label id="lab_us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisLiabilityGainLossIncludedInEarnings_936BB92D81F07E6BA408F226DC71AFAC_terseLabel_en-US" xlink:label="lab_us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisLiabilityGainLossIncludedInEarnings_936BB92D81F07E6BA408F226DC71AFAC" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Change in fair value</link:label>
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    <link:label id="lab_selb_PercentageOfSublicenseIncome_A0B34F1EEA04D3D4CE0708A6821F3511_terseLabel_en-US" xlink:label="lab_selb_PercentageOfSublicenseIncome_A0B34F1EEA04D3D4CE0708A6821F3511" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Percentage of sublicense income</link:label>
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    <link:label id="lab_us-gaap_LiabilitiesCurrent_8F9F98C86A88ED99E298F226DCF9B5F6_label_en-US" xlink:label="lab_us-gaap_LiabilitiesCurrent_8F9F98C86A88ED99E298F226DCF9B5F6" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Liabilities, Current</link:label>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_LiabilitiesCurrent" xlink:label="loc_us-gaap_LiabilitiesCurrent_8F9F98C86A88ED99E298F226DCF9B5F6" xlink:type="locator" />
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    <link:label id="lab_us-gaap_OtherLiabilitiesNoncurrentAbstract_349915308651F3BC2A92F226DCF918EB_terseLabel_en-US" xlink:label="lab_us-gaap_OtherLiabilitiesNoncurrentAbstract_349915308651F3BC2A92F226DCF918EB" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Non&#8209;current liabilities:</link:label>
    <link:label id="lab_us-gaap_OtherLiabilitiesNoncurrentAbstract_349915308651F3BC2A92F226DCF918EB_label_en-US" xlink:label="lab_us-gaap_OtherLiabilitiesNoncurrentAbstract_349915308651F3BC2A92F226DCF918EB" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Other Liabilities, Noncurrent [Abstract]</link:label>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_OtherLiabilitiesNoncurrentAbstract" xlink:label="loc_us-gaap_OtherLiabilitiesNoncurrentAbstract_349915308651F3BC2A92F226DCF918EB" xlink:type="locator" />
    <link:labelArc order="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_us-gaap_OtherLiabilitiesNoncurrentAbstract_349915308651F3BC2A92F226DCF918EB" xlink:to="lab_us-gaap_OtherLiabilitiesNoncurrentAbstract_349915308651F3BC2A92F226DCF918EB" xlink:type="arc" />
    <link:label id="lab_us-gaap_DeferredRentCreditNoncurrent_8EF25C873DE74EC5C8C9F226DCF9D865_terseLabel_en-US" xlink:label="lab_us-gaap_DeferredRentCreditNoncurrent_8EF25C873DE74EC5C8C9F226DCF9D865" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Deferred rent and lease incentive</link:label>
    <link:label id="lab_us-gaap_DeferredRentCreditNoncurrent_8EF25C873DE74EC5C8C9F226DCF9D865_label_en-US" xlink:label="lab_us-gaap_DeferredRentCreditNoncurrent_8EF25C873DE74EC5C8C9F226DCF9D865" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Deferred Rent Credit, Noncurrent</link:label>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_DeferredRentCreditNoncurrent" xlink:label="loc_us-gaap_DeferredRentCreditNoncurrent_8EF25C873DE74EC5C8C9F226DCF9D865" xlink:type="locator" />
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    <link:label id="lab_us-gaap_LongTermLoansPayable_C4B8976A2FACDD40AC1AF226DCF9352E_terseLabel_en-US" xlink:label="lab_us-gaap_LongTermLoansPayable_C4B8976A2FACDD40AC1AF226DCF9352E" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Loans payable, net of current portion</link:label>
    <link:label id="lab_us-gaap_LongTermLoansPayable_C4B8976A2FACDD40AC1AF226DCF9352E_label_en-US" xlink:label="lab_us-gaap_LongTermLoansPayable_C4B8976A2FACDD40AC1AF226DCF9352E" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Loans Payable, Noncurrent</link:label>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_LongTermLoansPayable" xlink:label="loc_us-gaap_LongTermLoansPayable_C4B8976A2FACDD40AC1AF226DCF9352E" xlink:type="locator" />
    <link:labelArc order="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_us-gaap_LongTermLoansPayable_C4B8976A2FACDD40AC1AF226DCF9352E" xlink:to="lab_us-gaap_LongTermLoansPayable_C4B8976A2FACDD40AC1AF226DCF9352E" xlink:type="arc" />
    <link:label id="lab_us-gaap_DeferredRevenueNoncurrent_D8EE4503887869BF3EF9F226DCF9A2C8_terseLabel_en-US" xlink:label="lab_us-gaap_DeferredRevenueNoncurrent_D8EE4503887869BF3EF9F226DCF9A2C8" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Deferred revenue, net of current portion</link:label>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_DeferredRevenueNoncurrent" xlink:label="loc_us-gaap_DeferredRevenueNoncurrent_D8EE4503887869BF3EF9F226DCF9A2C8" xlink:type="locator" />
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    <link:label id="lab_us-gaap_OtherLiabilitiesNoncurrent_676F4627FE86B31F9867F226DCF92EA1_label_en-US" xlink:label="lab_us-gaap_OtherLiabilitiesNoncurrent_676F4627FE86B31F9867F226DCF92EA1" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Other Liabilities, Noncurrent</link:label>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_OtherLiabilitiesNoncurrent" xlink:label="loc_us-gaap_OtherLiabilitiesNoncurrent_676F4627FE86B31F9867F226DCF92EA1" xlink:type="locator" />
    <link:labelArc order="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_us-gaap_OtherLiabilitiesNoncurrent_676F4627FE86B31F9867F226DCF92EA1" xlink:to="lab_us-gaap_OtherLiabilitiesNoncurrent_676F4627FE86B31F9867F226DCF92EA1" xlink:type="arc" />
    <link:label id="lab_us-gaap_Liabilities_7474E0B33C90ACA478A8F226DCFA236C_totalLabel_en-US" xlink:label="lab_us-gaap_Liabilities_7474E0B33C90ACA478A8F226DCFA236C" xlink:role="http://www.xbrl.org/2003/role/totalLabel" xlink:type="resource" xml:lang="en-US">Total liabilities</link:label>
    <link:label id="lab_us-gaap_Liabilities_7474E0B33C90ACA478A8F226DCFA236C_label_en-US" xlink:label="lab_us-gaap_Liabilities_7474E0B33C90ACA478A8F226DCFA236C" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Liabilities</link:label>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_Liabilities" xlink:label="loc_us-gaap_Liabilities_7474E0B33C90ACA478A8F226DCFA236C" xlink:type="locator" />
    <link:labelArc order="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_us-gaap_Liabilities_7474E0B33C90ACA478A8F226DCFA236C" xlink:to="lab_us-gaap_Liabilities_7474E0B33C90ACA478A8F226DCFA236C" xlink:type="arc" />
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    <link:label id="lab_us-gaap_CommitmentsAndContingencies_8240D2642500AFCD1F71F226DCFA35B4_label_en-US" xlink:label="lab_us-gaap_CommitmentsAndContingencies_8240D2642500AFCD1F71F226DCFA35B4" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Commitments and Contingencies</link:label>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_CommitmentsAndContingencies" xlink:label="loc_us-gaap_CommitmentsAndContingencies_8240D2642500AFCD1F71F226DCFA35B4" xlink:type="locator" />
    <link:labelArc order="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_us-gaap_CommitmentsAndContingencies_8240D2642500AFCD1F71F226DCFA35B4" xlink:to="lab_us-gaap_CommitmentsAndContingencies_8240D2642500AFCD1F71F226DCFA35B4" xlink:type="arc" />
    <link:label id="lab_selb_SeriesARedeemableConvertiblePreferredStockMember_40AE286C3029950BA7F8F226DCFAD7CE_terseLabel_en-US" xlink:label="lab_selb_SeriesARedeemableConvertiblePreferredStockMember_40AE286C3029950BA7F8F226DCFAD7CE" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Series A redeemable convertible preferred stock, $0.0001 par value; 0 and 2,589,868 shares authorized; 0 and 2,589,868 shares issued and outstanding; as of December 31, 2016 and December 31, 2015 respectively.</link:label>
    <link:loc xlink:href="selb-20161231.xsd#selb_SeriesARedeemableConvertiblePreferredStockMember" xlink:label="loc_selb_SeriesARedeemableConvertiblePreferredStockMember_40AE286C3029950BA7F8F226DCFAD7CE" xlink:type="locator" />
    <link:labelArc order="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_selb_SeriesARedeemableConvertiblePreferredStockMember_40AE286C3029950BA7F8F226DCFAD7CE" xlink:to="lab_selb_SeriesARedeemableConvertiblePreferredStockMember_40AE286C3029950BA7F8F226DCFAD7CE" xlink:type="arc" />
    <link:label id="lab_selb_SeriesBRedeemableConvertiblePreferredStockMember_A01FB2DD717AE7CA91F0F226DCFA8F12_terseLabel_en-US" xlink:label="lab_selb_SeriesBRedeemableConvertiblePreferredStockMember_A01FB2DD717AE7CA91F0F226DCFA8F12" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Series B redeemable convertible preferred stock, $0.0001 par value; 0 and 7,437,325 shares authorized; 0 and 7,437,325 shares issued and outstanding; as of December 31, 2016 and December 31, 2015 respectively.</link:label>
    <link:loc xlink:href="selb-20161231.xsd#selb_SeriesBRedeemableConvertiblePreferredStockMember" xlink:label="loc_selb_SeriesBRedeemableConvertiblePreferredStockMember_A01FB2DD717AE7CA91F0F226DCFA8F12" xlink:type="locator" />
    <link:labelArc order="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_selb_SeriesBRedeemableConvertiblePreferredStockMember_A01FB2DD717AE7CA91F0F226DCFA8F12" xlink:to="lab_selb_SeriesBRedeemableConvertiblePreferredStockMember_A01FB2DD717AE7CA91F0F226DCFA8F12" xlink:type="arc" />
    <link:label id="lab_selb_SeriesCRedeemableConvertiblePreferredStockMember_8FFB2DC25E7FD6D7C0D3F226DCFAD098_terseLabel_en-US" xlink:label="lab_selb_SeriesCRedeemableConvertiblePreferredStockMember_8FFB2DC25E7FD6D7C0D3F226DCFAD098" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Series C redeemable convertible preferred stock, $0.0001 par value; 0 and 5,000,002 shares authorized; 0 and 5,000,002 shares issued and outstanding; as of December 31, 2016 and December 31, 2015 respectively.</link:label>
    <link:loc xlink:href="selb-20161231.xsd#selb_SeriesCRedeemableConvertiblePreferredStockMember" xlink:label="loc_selb_SeriesCRedeemableConvertiblePreferredStockMember_8FFB2DC25E7FD6D7C0D3F226DCFAD098" xlink:type="locator" />
    <link:labelArc order="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_selb_SeriesCRedeemableConvertiblePreferredStockMember_8FFB2DC25E7FD6D7C0D3F226DCFAD098" xlink:to="lab_selb_SeriesCRedeemableConvertiblePreferredStockMember_8FFB2DC25E7FD6D7C0D3F226DCFAD098" xlink:type="arc" />
    <link:label id="lab_selb_SeriesDRedeemableConvertiblePreferredStockMember_FFC00DE92DB13FF9F80DF226DCFA0AE1_terseLabel_en-US" xlink:label="lab_selb_SeriesDRedeemableConvertiblePreferredStockMember_FFC00DE92DB13FF9F80DF226DCFA0AE1" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Series D redeemable convertible preferred stock, $0.0001 par value; 0 and 8,166,662 shares authorized; 0 and 8,099,994 shares issued and outstanding; as of December 31, 2016 and December 31, 2015 respectively.</link:label>
    <link:loc xlink:href="selb-20161231.xsd#selb_SeriesDRedeemableConvertiblePreferredStockMember" xlink:label="loc_selb_SeriesDRedeemableConvertiblePreferredStockMember_FFC00DE92DB13FF9F80DF226DCFA0AE1" xlink:type="locator" />
    <link:labelArc order="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_selb_SeriesDRedeemableConvertiblePreferredStockMember_FFC00DE92DB13FF9F80DF226DCFA0AE1" xlink:to="lab_selb_SeriesDRedeemableConvertiblePreferredStockMember_FFC00DE92DB13FF9F80DF226DCFA0AE1" xlink:type="arc" />
    <link:label id="lab_selb_SeriesSRNRedeemableConvertiblePreferredStockMember_0132F96EF43ADF8BFC89F226DCFABC27_terseLabel_en-US" xlink:label="lab_selb_SeriesSRNRedeemableConvertiblePreferredStockMember_0132F96EF43ADF8BFC89F226DCFABC27" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Series SRN redeemable convertible preferred stock, $0.0001 par value; 0 and 5,611,112 shares authorized; 0 and 2,111,109 shares issued and outstanding; as of December 31, 2016 and December 31, 2015 respectively.</link:label>
    <link:loc xlink:href="selb-20161231.xsd#selb_SeriesSRNRedeemableConvertiblePreferredStockMember" xlink:label="loc_selb_SeriesSRNRedeemableConvertiblePreferredStockMember_0132F96EF43ADF8BFC89F226DCFABC27" xlink:type="locator" />
    <link:labelArc order="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_selb_SeriesSRNRedeemableConvertiblePreferredStockMember_0132F96EF43ADF8BFC89F226DCFABC27" xlink:to="lab_selb_SeriesSRNRedeemableConvertiblePreferredStockMember_0132F96EF43ADF8BFC89F226DCFABC27" xlink:type="arc" />
    <link:label id="lab_selb_SeriesERedeemableConvertiblePreferredStockMember_4920ABC721E590C2F76AF226DCFAB042_terseLabel_en-US" xlink:label="lab_selb_SeriesERedeemableConvertiblePreferredStockMember_4920ABC721E590C2F76AF226DCFAB042" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Series E redeemable convertible preferred stock, $0.0001 par value; 0 and 9,030,654 shares authorized; 0 and 8,888,888 shares issued and outstanding; as of December 31, 2016 and December 31, 2015 respectively.</link:label>
    <link:loc xlink:href="selb-20161231.xsd#selb_SeriesERedeemableConvertiblePreferredStockMember" xlink:label="loc_selb_SeriesERedeemableConvertiblePreferredStockMember_4920ABC721E590C2F76AF226DCFAB042" xlink:type="locator" />
    <link:labelArc order="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_selb_SeriesERedeemableConvertiblePreferredStockMember_4920ABC721E590C2F76AF226DCFAB042" xlink:to="lab_selb_SeriesERedeemableConvertiblePreferredStockMember_4920ABC721E590C2F76AF226DCFAB042" xlink:type="arc" />
    <link:label id="lab_us-gaap_TemporaryEquityCarryingAmountAttributableToParent_B64FEFC2689DBC300E05F226DCFA1185_terseLabel_en-US" xlink:label="lab_us-gaap_TemporaryEquityCarryingAmountAttributableToParent_B64FEFC2689DBC300E05F226DCFA1185" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Total redeemable convertible preferred stock</link:label>
    <link:label id="lab_us-gaap_TemporaryEquityCarryingAmountAttributableToParent_B64FEFC2689DBC300E05F226DCFA1185_label_en-US" xlink:label="lab_us-gaap_TemporaryEquityCarryingAmountAttributableToParent_B64FEFC2689DBC300E05F226DCFA1185" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Temporary Equity, Carrying Amount, Attributable to Parent</link:label>
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    <link:label id="lab_us-gaap_StockholdersEquityAbstract_46ED89C00BA28EC025B6F226DCFA7849_terseLabel_en-US" xlink:label="lab_us-gaap_StockholdersEquityAbstract_46ED89C00BA28EC025B6F226DCFA7849" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Stockholders&#8217; equity (deficit):</link:label>
    <link:label id="lab_us-gaap_StockholdersEquityAbstract_46ED89C00BA28EC025B6F226DCFA7849_label_en-US" xlink:label="lab_us-gaap_StockholdersEquityAbstract_46ED89C00BA28EC025B6F226DCFA7849" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Stockholders' Equity Attributable to Parent [Abstract]</link:label>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_StockholdersEquityAbstract" xlink:label="loc_us-gaap_StockholdersEquityAbstract_46ED89C00BA28EC025B6F226DCFA7849" xlink:type="locator" />
    <link:labelArc order="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_us-gaap_StockholdersEquityAbstract_46ED89C00BA28EC025B6F226DCFA7849" xlink:to="lab_us-gaap_StockholdersEquityAbstract_46ED89C00BA28EC025B6F226DCFA7849" xlink:type="arc" />
    <link:label id="lab_us-gaap_PreferredStockValue_B4AE202D341CD5FE6FE0F226DCFAEB3D_terseLabel_en-US" xlink:label="lab_us-gaap_PreferredStockValue_B4AE202D341CD5FE6FE0F226DCFAEB3D" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Preferred stock, $0.0001 par value; 10,000,000 and 0 shares authorized; 0 shares issued and outstanding at December 31, 2016 and December 31, 2015, respectively.</link:label>
    <link:label id="lab_us-gaap_PreferredStockValue_B4AE202D341CD5FE6FE0F226DCFAEB3D_label_en-US" xlink:label="lab_us-gaap_PreferredStockValue_B4AE202D341CD5FE6FE0F226DCFAEB3D" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Preferred Stock, Value, Issued</link:label>
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    <link:label id="lab_us-gaap_InterestPaid_FBDF6F4C3EE5812B28E8FD11C8DA28D0_label_en-US" xlink:label="lab_us-gaap_InterestPaid_FBDF6F4C3EE5812B28E8FD11C8DA28D0" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Interest Paid</link:label>
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    <link:label id="lab_us-gaap_RelatedPartyDomain_D5068002046087A69831F226DB23DCEF_label_en-US" xlink:label="lab_us-gaap_RelatedPartyDomain_D5068002046087A69831F226DB23DCEF" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Related Party [Domain]</link:label>
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    <link:label id="lab_selb_FounderMember_FD5B7C37CF35A6353CC6F226DB2311D4_label_en-US" xlink:label="lab_selb_FounderMember_FD5B7C37CF35A6353CC6F226DB2311D4" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Founder [Member]</link:label>
    <link:label id="lab_selb_FounderMember_FD5B7C37CF35A6353CC6F226DB2311D4_documentation_en-US" xlink:label="lab_selb_FounderMember_FD5B7C37CF35A6353CC6F226DB2311D4" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:type="resource" xml:lang="en-US">Represents information pertaining to founder member.</link:label>
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    <link:label id="lab_us-gaap_DebtInstrumentInterestRateEffectivePercentage_F6D36623D8D2A559A23AF226DCA6E656_verboseLabel_en-US" xlink:label="lab_us-gaap_DebtInstrumentInterestRateEffectivePercentage_F6D36623D8D2A559A23AF226DCA6E656" xlink:role="http://www.xbrl.org/2003/role/verboseLabel" xlink:type="resource" xml:lang="en-US">Interest rate on loans payable</link:label>
    <link:label id="lab_us-gaap_DebtInstrumentInterestRateEffectivePercentage_F6D36623D8D2A559A23AF226DCA6E656_label_en-US" xlink:label="lab_us-gaap_DebtInstrumentInterestRateEffectivePercentage_F6D36623D8D2A559A23AF226DCA6E656" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Debt Instrument, Interest Rate, Effective Percentage</link:label>
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    <link:label id="lab_us-gaap_TemporaryEquitySharesAuthorized_2C11AF80B40F12AE2214F226DBD54B96_verboseLabel_en-US" xlink:label="lab_us-gaap_TemporaryEquitySharesAuthorized_2C11AF80B40F12AE2214F226DBD54B96" xlink:role="http://www.xbrl.org/2003/role/verboseLabel" xlink:type="resource" xml:lang="en-US">Authorized shares of Preferred Stock (in shares)</link:label>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_TemporaryEquitySharesAuthorized" xlink:label="loc_us-gaap_TemporaryEquitySharesAuthorized_2C11AF80B40F12AE2214F226DBD54B96" xlink:type="locator" />
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    <link:label id="lab_us-gaap_TemporaryEquityByClassOfStockTable_6C4230E3BA6323E92C46F226DBD580E5_terseLabel_en-US" xlink:label="lab_us-gaap_TemporaryEquityByClassOfStockTable_6C4230E3BA6323E92C46F226DBD580E5" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Temporary Equity, by Class of Stock [Table]</link:label>
    <link:label id="lab_us-gaap_TemporaryEquityByClassOfStockTable_6C4230E3BA6323E92C46F226DBD580E5_label_en-US" xlink:label="lab_us-gaap_TemporaryEquityByClassOfStockTable_6C4230E3BA6323E92C46F226DBD580E5" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Temporary Equity, by Class of Stock [Table]</link:label>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_TemporaryEquityByClassOfStockTable" xlink:label="loc_us-gaap_TemporaryEquityByClassOfStockTable_6C4230E3BA6323E92C46F226DBD580E5" xlink:type="locator" />
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    <link:label id="lab_us-gaap_ConversionOfStockByUniqueDescriptionAxis_5A7C74E4BBB03A7ED535F226DBD65049_terseLabel_en-US" xlink:label="lab_us-gaap_ConversionOfStockByUniqueDescriptionAxis_5A7C74E4BBB03A7ED535F226DBD65049" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Stock Conversion Description [Axis]</link:label>
    <link:label id="lab_us-gaap_ConversionOfStockByUniqueDescriptionAxis_5A7C74E4BBB03A7ED535F226DBD65049_label_en-US" xlink:label="lab_us-gaap_ConversionOfStockByUniqueDescriptionAxis_5A7C74E4BBB03A7ED535F226DBD65049" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Stock Conversion Description [Axis]</link:label>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_ConversionOfStockByUniqueDescriptionAxis" xlink:label="loc_us-gaap_ConversionOfStockByUniqueDescriptionAxis_5A7C74E4BBB03A7ED535F226DBD65049" xlink:type="locator" />
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    <link:label id="lab_us-gaap_ConversionOfStockNameDomain_75449269AE169CC770BFF226DBD69FD5_terseLabel_en-US" xlink:label="lab_us-gaap_ConversionOfStockNameDomain_75449269AE169CC770BFF226DBD69FD5" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Conversion of Stock, Name [Domain]</link:label>
    <link:label id="lab_us-gaap_ConversionOfStockNameDomain_75449269AE169CC770BFF226DBD69FD5_label_en-US" xlink:label="lab_us-gaap_ConversionOfStockNameDomain_75449269AE169CC770BFF226DBD69FD5" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Conversion of Stock, Name [Domain]</link:label>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_ConversionOfStockNameDomain" xlink:label="loc_us-gaap_ConversionOfStockNameDomain_75449269AE169CC770BFF226DBD69FD5" xlink:type="locator" />
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    <link:label id="lab_selb_PreferredStockAutomaticallyConvertedIntoCommonStockUponClosingOfInitialPublicOfferingMember_D06AD3D19A1341826EABF226DBD65478_terseLabel_en-US" xlink:label="lab_selb_PreferredStockAutomaticallyConvertedIntoCommonStockUponClosingOfInitialPublicOfferingMember_D06AD3D19A1341826EABF226DBD65478" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Preferred stock automatically converted into common stock upon the closing of the IPO</link:label>
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    <link:loc xlink:href="selb-20161231.xsd#selb_PreferredStockAutomaticallyConvertedIntoCommonStockUponClosingOfInitialPublicOfferingMember" xlink:label="loc_selb_PreferredStockAutomaticallyConvertedIntoCommonStockUponClosingOfInitialPublicOfferingMember_D06AD3D19A1341826EABF226DBD65478" xlink:type="locator" />
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    <link:label id="lab_us-gaap_TemporaryEquityLineItems_6634088944FC6D411EE7F226DBD64361_terseLabel_en-US" xlink:label="lab_us-gaap_TemporaryEquityLineItems_6634088944FC6D411EE7F226DBD64361" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Preferred stock</link:label>
    <link:label id="lab_us-gaap_TemporaryEquityLineItems_6634088944FC6D411EE7F226DBD64361_label_en-US" xlink:label="lab_us-gaap_TemporaryEquityLineItems_6634088944FC6D411EE7F226DBD64361" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Temporary Equity [Line Items]</link:label>
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    <link:label id="lab_us-gaap_SharesIssuedPricePerShare_09932E717C2A58C4641DF226DBD69E49_terseLabel_en-US" xlink:label="lab_us-gaap_SharesIssuedPricePerShare_09932E717C2A58C4641DF226DBD69E49" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Price per share (in dollars per share)</link:label>
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_SharesIssuedPricePerShare" xlink:label="loc_us-gaap_SharesIssuedPricePerShare_09932E717C2A58C4641DF226DBD69E49" xlink:type="locator" />
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    <link:label id="lab_us-gaap_ProceedsFromIssuanceOfRedeemableConvertiblePreferredStock_CECDDFBB43D7393D24A7F226DBD6469A_terseLabel_en-US" xlink:label="lab_us-gaap_ProceedsFromIssuanceOfRedeemableConvertiblePreferredStock_CECDDFBB43D7393D24A7F226DBD6469A" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Total net proceeds from issuance of Series D Preferred</link:label>
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    <link:label id="lab_selb_TemporaryEquityConversionPricePerShare_930D825589751409337CF226DBD649F6_terseLabel_en-US" xlink:label="lab_selb_TemporaryEquityConversionPricePerShare_930D825589751409337CF226DBD649F6" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Conversion price (in dollars per share)</link:label>
    <link:label id="lab_selb_TemporaryEquityConversionPricePerShare_930D825589751409337CF226DBD649F6_label_en-US" xlink:label="lab_selb_TemporaryEquityConversionPricePerShare_930D825589751409337CF226DBD649F6" xlink:role="http://www.xbrl.org/2003/role/label" xlink:type="resource" xml:lang="en-US">Temporary Equity Conversion Price Per Share</link:label>
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    <link:label id="lab_us-gaap_TemporaryEquityCarryingAmountAttributableToParent_02F6CB7BC014930B0408F226DBD6EA46_verboseLabel_en-US" xlink:label="lab_us-gaap_TemporaryEquityCarryingAmountAttributableToParent_02F6CB7BC014930B0408F226DBD6EA46" xlink:role="http://www.xbrl.org/2003/role/verboseLabel" xlink:type="resource" xml:lang="en-US">Carrying value of Series SRN Preferred</link:label>
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    <link:label id="lab_us-gaap_AdjustmentsToAdditionalPaidInCapitalIncreaseInCarryingAmountOfRedeemablePreferredStock_E84169FBC2C03F6C2AD5F226DBD6EAAA_terseLabel_en-US" xlink:label="lab_us-gaap_AdjustmentsToAdditionalPaidInCapitalIncreaseInCarryingAmountOfRedeemablePreferredStock_E84169FBC2C03F6C2AD5F226DBD6EAAA" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:type="resource" xml:lang="en-US">Difference recorded as additional paid in capital</link:label>
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    <link:labelArc order="1" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="loc_us-gaap_AdjustmentsToAdditionalPaidInCapitalIncreaseInCarryingAmountOfRedeemablePreferredStock_E84169FBC2C03F6C2AD5F226DBD6EAAA" xlink:to="lab_us-gaap_AdjustmentsToAdditionalPaidInCapitalIncreaseInCarryingAmountOfRedeemablePreferredStock_E84169FBC2C03F6C2AD5F226DBD6EAAA" xlink:type="arc" />
    <link:label id="lab_selb_ProceedsFromIssuanceOfRedeemableConvertiblePreferredStockGross_E650737E24B5AECEA58AF226DBD6DB1E_verboseLabel_en-US" xlink:label="lab_selb_ProceedsFromIssuanceOfRedeemableConvertiblePreferredStockGross_E650737E24B5AECEA58AF226DBD6DB1E" xlink:role="http://www.xbrl.org/2003/role/verboseLabel" xlink:type="resource" xml:lang="en-US">Total gross proceeds from issuance of Series E Preferred</link:label>
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    <link:label id="lab_selb_ProceedsFromIssuanceOfRedeemableConvertiblePreferredStockGross_E650737E24B5AECEA58AF226DBD6DB1E_documentation_en-US" xlink:label="lab_selb_ProceedsFromIssuanceOfRedeemableConvertiblePreferredStockGross_E650737E24B5AECEA58AF226DBD6DB1E" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:type="resource" xml:lang="en-US">The gross cash inflow from issuance of callable preferred stock which is identified as being convertible to another type of financial security at the option of the issuer or the holder.</link:label>
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    <link:label id="lab_us-gaap_PaymentsOfStockIssuanceCosts_C3489BE372C5B5171502F226DBD7522D_verboseLabel_en-US" xlink:label="lab_us-gaap_PaymentsOfStockIssuanceCosts_C3489BE372C5B5171502F226DBD7522D" xlink:role="http://www.xbrl.org/2003/role/verboseLabel" xlink:type="resource" xml:lang="en-US">Issuance costs</link:label>
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    <link:label id="lab_selb_StockVestedDuringPeriodShareRestrictedCommonStock_7C03E3BD8DB6FA4A7615F673C0C48A0A_documentation_en-US" xlink:label="lab_selb_StockVestedDuringPeriodShareRestrictedCommonStock_7C03E3BD8DB6FA4A7615F673C0C48A0A" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:type="resource" xml:lang="en-US">Represents the total number of shares vested during the period as a result of Restricted Common Stock.</link:label>
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    <link:label id="lab_selb_StockVestedDuringPeriodValueRestrictedCommonStock_65008BD2B6D2E9EF3C04F673C0C4EDE7_documentation_en-US" xlink:label="lab_selb_StockVestedDuringPeriodValueRestrictedCommonStock_65008BD2B6D2E9EF3C04F673C0C4EDE7" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:type="resource" xml:lang="en-US">Represents the aggregate value of stock related to Restricted Common Stock vested during the period.</link:label>
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    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_StockIssuedDuringPeriodValueStockOptionsExercised" xlink:label="loc_us-gaap_StockIssuedDuringPeriodValueStockOptionsExercised_F6109DF1978A4002AAADF673C0C4672E" xlink:type="locator" />
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    <link:label id="lab_selb_StockholdersEquityAccretionToRedemptionValue_41B69395B792737E3A27F673C0C42A3D_documentation_en-US" xlink:label="lab_selb_StockholdersEquityAccretionToRedemptionValue_41B69395B792737E3A27F673C0C42A3D" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:type="resource" xml:lang="en-US">Represents the value of accretion of temporary equity to redemption value during the period.</link:label>
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    <link:label id="lab_us-gaap_TemporaryEquityStockIssuedDuringPeriodValueNewIssues_03403C40957D7BB0F6C5F673C0C4355A_verboseLabel_en-US" xlink:label="lab_us-gaap_TemporaryEquityStockIssuedDuringPeriodValueNewIssues_03403C40957D7BB0F6C5F673C0C4355A" xlink:role="http://www.xbrl.org/2003/role/verboseLabel" xlink:type="resource" xml:lang="en-US">Issuance of redeemable convertible preferred stock, net of issuance costs</link:label>
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