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      <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_NoncompeteAgreementsMember" xlink:to="us-gaap_NoncompeteAgreementsMember_lbl" xlink:type="arc" />
      <link:label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_NoncompeteAgreementsMember_lbl" xml:lang="en-US">Noncompete Agreements [Member]</link:label>
      <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/srt/2020/elts/srt-2020-01-31.xsd#srt_RangeAxis" xlink:label="srt_RangeAxis" />
      <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="srt_RangeAxis" xlink:to="srt_RangeAxis_lbl" xlink:type="arc" />
      <link:label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="srt_RangeAxis_lbl" xml:lang="en-US">Range [Axis]</link:label>
      <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/srt/2020/elts/srt-2020-01-31.xsd#srt_MinimumMember" xlink:label="srt_MinimumMember" />
      <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="srt_MinimumMember" xlink:to="srt_MinimumMember_lbl" xlink:type="arc" />
      <link:label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="srt_MinimumMember_lbl" xml:lang="en-US">Minimum [Member]</link:label>
      <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/srt/2020/elts/srt-2020-01-31.xsd#srt_MaximumMember" xlink:label="srt_MaximumMember" />
      <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="srt_MaximumMember" xlink:to="srt_MaximumMember_lbl" xlink:type="arc" />
      <link:label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="srt_MaximumMember_lbl" xml:lang="en-US">Maximum [Member]</link:label>
      <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_FairValueByAssetClassAxis" xlink:label="us-gaap_FairValueByAssetClassAxis" />
      <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_FairValueByAssetClassAxis" xlink:to="us-gaap_FairValueByAssetClassAxis_lbl" xlink:type="arc" />
      <link:label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_FairValueByAssetClassAxis_lbl" xml:lang="en-US">Asset Class [Axis]</link:label>
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      <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="CLSN_IPRAndDMember" xlink:to="CLSN_IPRAndDMember_lbl" xlink:type="arc" />
      <link:label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="CLSN_IPRAndDMember_lbl" xml:lang="en-US">IPR&amp;D [Member]</link:label>
      <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_GoodwillMember" xlink:label="us-gaap_GoodwillMember" />
      <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_GoodwillMember" xlink:to="us-gaap_GoodwillMember_lbl" xlink:type="arc" />
      <link:label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_GoodwillMember_lbl" xml:lang="en-US">Goodwill [Member]</link:label>
      <link:loc xlink:type="locator" xlink:href="clsn-20200630.xsd#CLSN_AspirePurchaseAgreementsMember" xlink:label="CLSN_AspirePurchaseAgreementsMember" />
      <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="CLSN_AspirePurchaseAgreementsMember" xlink:to="CLSN_AspirePurchaseAgreementsMember_lbl" xlink:type="arc" />
      <link:label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/verboseLabel" xlink:label="CLSN_AspirePurchaseAgreementsMember_lbl" xml:lang="en-US">2018 Aspire Purchase Agreements [Member]</link:label>
      <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_PlanNameAxis" xlink:label="us-gaap_PlanNameAxis" />
      <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_PlanNameAxis" xlink:to="us-gaap_PlanNameAxis_lbl" xlink:type="arc" />
      <link:label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_PlanNameAxis_lbl" xml:lang="en-US">Plan Name [Axis]</link:label>
      <link:loc xlink:type="locator" xlink:href="clsn-20200630.xsd#CLSN_InducementOptionGrantsMember" xlink:label="CLSN_InducementOptionGrantsMember" />
      <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="CLSN_InducementOptionGrantsMember" xlink:to="CLSN_InducementOptionGrantsMember_lbl" xlink:type="arc" />
      <link:label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="CLSN_InducementOptionGrantsMember_lbl" xml:lang="en-US">Inducement Option Grants [Member]</link:label>
      <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/srt/2020/elts/srt-2020-01-31.xsd#srt_TitleOfIndividualAxis" xlink:label="srt_TitleOfIndividualAxis" />
      <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="srt_TitleOfIndividualAxis" xlink:to="srt_TitleOfIndividualAxis_lbl" xlink:type="arc" />
      <link:label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="srt_TitleOfIndividualAxis_lbl" xml:lang="en-US">Title of Individual [Axis]</link:label>
      <link:loc xlink:type="locator" xlink:href="clsn-20200630.xsd#CLSN_TwoNewEmployeesMember" xlink:label="CLSN_TwoNewEmployeesMember" />
      <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="CLSN_TwoNewEmployeesMember" xlink:to="CLSN_TwoNewEmployeesMember_lbl" xlink:type="arc" />
      <link:label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="CLSN_TwoNewEmployeesMember_lbl" xml:lang="en-US">Two New Employees [Member]</link:label>
      <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_AwardTypeAxis" xlink:label="us-gaap_AwardTypeAxis" />
      <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_AwardTypeAxis" xlink:to="us-gaap_AwardTypeAxis_lbl" xlink:type="arc" />
      <link:label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_AwardTypeAxis_lbl" xml:lang="en-US">Award Type [Axis]</link:label>
      <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_RestrictedStockMember" xlink:label="us-gaap_RestrictedStockMember" />
      <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_RestrictedStockMember" xlink:to="us-gaap_RestrictedStockMember_lbl" xlink:type="arc" />
      <link:label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_RestrictedStockMember_lbl" xml:lang="en-US">Restricted Stock Awards [Member]</link:label>
      <link:loc xlink:type="locator" xlink:href="clsn-20200630.xsd#CLSN_FiveNewEmployeesMember" xlink:label="CLSN_FiveNewEmployeesMember" />
      <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="CLSN_FiveNewEmployeesMember" xlink:to="CLSN_FiveNewEmployeesMember_lbl" xlink:type="arc" />
      <link:label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="CLSN_FiveNewEmployeesMember_lbl" xml:lang="en-US">Five New Employees [Member]</link:label>
      <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_EmployeeStockOptionMember" xlink:label="us-gaap_EmployeeStockOptionMember" />
      <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_EmployeeStockOptionMember" xlink:to="us-gaap_EmployeeStockOptionMember_lbl" xlink:type="arc" />
      <link:label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_EmployeeStockOptionMember_lbl" xml:lang="en-US">Stock Options [Member]</link:label>
      <link:loc xlink:type="locator" xlink:href="clsn-20200630.xsd#CLSN_TwoThousandNineteenAspirePurchaseAgreementsMember" xlink:label="CLSN_TwoThousandNineteenAspirePurchaseAgreementsMember" />
      <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="CLSN_TwoThousandNineteenAspirePurchaseAgreementsMember" xlink:to="CLSN_TwoThousandNineteenAspirePurchaseAgreementsMember_lbl" xlink:type="arc" />
      <link:label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="CLSN_TwoThousandNineteenAspirePurchaseAgreementsMember_lbl" xml:lang="en-US">2019 Aspire Purchase Agreements [Member]</link:label>
      <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_InvestmentTypeAxis" xlink:label="us-gaap_InvestmentTypeAxis" />
      <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_InvestmentTypeAxis" xlink:to="us-gaap_InvestmentTypeAxis_lbl" xlink:type="arc" />
      <link:label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_InvestmentTypeAxis_lbl" xml:lang="en-US">Investment Type [Axis]</link:label>
      <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ShortTermInvestmentsMember" xlink:label="us-gaap_ShortTermInvestmentsMember" />
      <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_ShortTermInvestmentsMember" xlink:to="us-gaap_ShortTermInvestmentsMember_lbl" xlink:type="arc" />
      <link:label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_ShortTermInvestmentsMember_lbl" xml:lang="en-US">Short-term Investments [Member]</link:label>
      <link:loc xlink:type="locator" xlink:href="clsn-20200630.xsd#CLSN_SecuritiesPurchaseAgreementMember" xlink:label="CLSN_SecuritiesPurchaseAgreementMember" />
      <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="CLSN_SecuritiesPurchaseAgreementMember" xlink:to="CLSN_SecuritiesPurchaseAgreementMember_lbl" xlink:type="arc" />
      <link:label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="CLSN_SecuritiesPurchaseAgreementMember_lbl" xml:lang="en-US">Securities Purchase Agreement [Member]</link:label>
      <link:loc xlink:type="locator" xlink:href="clsn-20200630.xsd#CLSN_OriginalWarrantsMember" xlink:label="CLSN_OriginalWarrantsMember" />
      <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="CLSN_OriginalWarrantsMember" xlink:to="CLSN_OriginalWarrantsMember_lbl" xlink:type="arc" />
      <link:label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="CLSN_OriginalWarrantsMember_lbl" xml:lang="en-US">Original Warrants [Member]</link:label>
      <link:loc xlink:type="locator" xlink:href="clsn-20200630.xsd#CLSN_PrivateExchangeAgreementsMember" xlink:label="CLSN_PrivateExchangeAgreementsMember" />
      <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="CLSN_PrivateExchangeAgreementsMember" xlink:to="CLSN_PrivateExchangeAgreementsMember_lbl" xlink:type="arc" />
      <link:label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="CLSN_PrivateExchangeAgreementsMember_lbl" xml:lang="en-US">Private Exchange Agreements [Member]</link:label>
      <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_WarrantMember" xlink:label="us-gaap_WarrantMember" />
      <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_WarrantMember" xlink:to="us-gaap_WarrantMember_lbl" xlink:type="arc" />
      <link:label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_WarrantMember_lbl" xml:lang="en-US">Warrant [Member]</link:label>
      <link:loc xlink:type="locator" xlink:href="clsn-20200630.xsd#CLSN_HorizonTechnologyFinanceCorporationMember" xlink:label="CLSN_HorizonTechnologyFinanceCorporationMember" />
      <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="CLSN_HorizonTechnologyFinanceCorporationMember" xlink:to="CLSN_HorizonTechnologyFinanceCorporationMember_lbl" xlink:type="arc" />
      <link:label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="CLSN_HorizonTechnologyFinanceCorporationMember_lbl" xml:lang="en-US">Horizon Technology Finance Corporation [Member]</link:label>
      <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_VariableRateAxis" xlink:label="us-gaap_VariableRateAxis" />
      <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_VariableRateAxis" xlink:to="us-gaap_VariableRateAxis_lbl" xlink:type="arc" />
      <link:label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_VariableRateAxis_lbl" xml:lang="en-US">Variable Rate [Axis]</link:label>
      <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_LondonInterbankOfferedRateLIBORMember" xlink:label="us-gaap_LondonInterbankOfferedRateLIBORMember" />
      <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_LondonInterbankOfferedRateLIBORMember" xlink:to="us-gaap_LondonInterbankOfferedRateLIBORMember_lbl" xlink:type="arc" />
      <link:label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_LondonInterbankOfferedRateLIBORMember_lbl" xml:lang="en-US">London Interbank Offered Rate (LIBOR) [Member]</link:label>
      <link:loc xlink:type="locator" xlink:href="clsn-20200630.xsd#CLSN_RNADeliverySystemMember" xlink:label="CLSN_RNADeliverySystemMember" />
      <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="CLSN_RNADeliverySystemMember" xlink:to="CLSN_RNADeliverySystemMember_lbl" xlink:type="arc" />
      <link:label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="CLSN_RNADeliverySystemMember_lbl" xml:lang="en-US">RNA Delivery System [Member]</link:label>
      <link:loc xlink:type="locator" xlink:href="clsn-20200630.xsd#CLSN_PurchaseAgreementMember" xlink:label="CLSN_PurchaseAgreementMember" />
      <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="CLSN_PurchaseAgreementMember" xlink:to="CLSN_PurchaseAgreementMember_lbl" xlink:type="arc" />
      <link:label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="CLSN_PurchaseAgreementMember_lbl" xml:lang="en-US">Purchase Agreement [Member]</link:label>
      <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_DebtInstrumentAxis" xlink:label="us-gaap_DebtInstrumentAxis" />
      <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_DebtInstrumentAxis" xlink:to="us-gaap_DebtInstrumentAxis_lbl" xlink:type="arc" />
      <link:label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_DebtInstrumentAxis_lbl" xml:lang="en-US">Debt Instrument [Axis]</link:label>
      <link:loc xlink:type="locator" xlink:href="clsn-20200630.xsd#CLSN_TwoThousandAndEighteenStockIncentivePlanMember" xlink:label="CLSN_TwoThousandAndEighteenStockIncentivePlanMember" />
      <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="CLSN_TwoThousandAndEighteenStockIncentivePlanMember" xlink:to="CLSN_TwoThousandAndEighteenStockIncentivePlanMember_lbl" xlink:type="arc" />
      <link:label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="CLSN_TwoThousandAndEighteenStockIncentivePlanMember_lbl" xml:lang="en-US">2018 Stock Incentive Plan [Member]</link:label>
      <link:loc xlink:type="locator" xlink:href="clsn-20200630.xsd#CLSN_TwoThousandSevenStockIncentivePlanMember" xlink:label="CLSN_TwoThousandSevenStockIncentivePlanMember" />
      <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="CLSN_TwoThousandSevenStockIncentivePlanMember" xlink:to="CLSN_TwoThousandSevenStockIncentivePlanMember_lbl" xlink:type="arc" />
      <link:label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="CLSN_TwoThousandSevenStockIncentivePlanMember_lbl" xml:lang="en-US">2007 Stock Incentive Plan [Member]</link:label>
      <link:loc xlink:type="locator" xlink:href="clsn-20200630.xsd#CLSN_EquityStockAwardsMember" xlink:label="CLSN_EquityStockAwardsMember" />
      <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="CLSN_EquityStockAwardsMember" xlink:to="CLSN_EquityStockAwardsMember_lbl" xlink:type="arc" />
      <link:label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="CLSN_EquityStockAwardsMember_lbl" xml:lang="en-US">Equity Stock Awards [Member]</link:label>
      <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/srt/2020/elts/srt-2020-01-31.xsd#srt_StatementScenarioAxis" xlink:label="srt_StatementScenarioAxis" />
      <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="srt_StatementScenarioAxis" xlink:to="srt_StatementScenarioAxis_lbl" xlink:type="arc" />
      <link:label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="srt_StatementScenarioAxis_lbl" xml:lang="en-US">Scenario [Axis]</link:label>
      <link:loc xlink:type="locator" xlink:href="clsn-20200630.xsd#CLSN_GrantedUnderTwoThousandEighteenPlanAndTwoThousandSevenPlanMember" xlink:label="CLSN_GrantedUnderTwoThousandEighteenPlanAndTwoThousandSevenPlanMember" />
      <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="CLSN_GrantedUnderTwoThousandEighteenPlanAndTwoThousandSevenPlanMember" xlink:to="CLSN_GrantedUnderTwoThousandEighteenPlanAndTwoThousandSevenPlanMember_lbl" xlink:type="arc" />
      <link:label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="CLSN_GrantedUnderTwoThousandEighteenPlanAndTwoThousandSevenPlanMember_lbl" xml:lang="en-US">Granted Under 2018 Plan and 2007 Plan [Member]</link:label>
      <link:loc xlink:type="locator" xlink:href="clsn-20200630.xsd#CLSN_TwoThousandAndEighteenPlanMember" xlink:label="CLSN_TwoThousandAndEighteenPlanMember" />
      <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="CLSN_TwoThousandAndEighteenPlanMember" xlink:to="CLSN_TwoThousandAndEighteenPlanMember_lbl" xlink:type="arc" />
      <link:label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="CLSN_TwoThousandAndEighteenPlanMember_lbl" xml:lang="en-US">2018 Plan [Member]</link:label>
      <link:loc xlink:type="locator" xlink:href="clsn-20200630.xsd#CLSN_InducementAwardsMember" xlink:label="CLSN_InducementAwardsMember" />
      <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="CLSN_InducementAwardsMember" xlink:to="CLSN_InducementAwardsMember_lbl" xlink:type="arc" />
      <link:label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="CLSN_InducementAwardsMember_lbl" xml:lang="en-US">Inducement Awards [Member]</link:label>
      <link:loc xlink:type="locator" xlink:href="clsn-20200630.xsd#CLSN_EmployeeStockOptionAndRestrictedStockAwardsMember" xlink:label="CLSN_EmployeeStockOptionAndRestrictedStockAwardsMember" />
      <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="CLSN_EmployeeStockOptionAndRestrictedStockAwardsMember" xlink:to="CLSN_EmployeeStockOptionAndRestrictedStockAwardsMember_lbl" xlink:type="arc" />
      <link:label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="CLSN_EmployeeStockOptionAndRestrictedStockAwardsMember_lbl" xml:lang="en-US">Stock Options and Restricted Stock Awards [Member]</link:label>
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      <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_IncomeStatementLocationAxis" xlink:to="us-gaap_IncomeStatementLocationAxis_lbl" xlink:type="arc" />
      <link:label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_IncomeStatementLocationAxis_lbl" xml:lang="en-US">Income Statement Location [Axis]</link:label>
      <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ResearchAndDevelopmentExpenseMember" xlink:label="us-gaap_ResearchAndDevelopmentExpenseMember" />
      <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_ResearchAndDevelopmentExpenseMember" xlink:to="us-gaap_ResearchAndDevelopmentExpenseMember_lbl" xlink:type="arc" />
      <link:label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_ResearchAndDevelopmentExpenseMember_lbl" xml:lang="en-US">Research and Development Expense [Member]</link:label>
      <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_GeneralAndAdministrativeExpenseMember" xlink:label="us-gaap_GeneralAndAdministrativeExpenseMember" />
      <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_GeneralAndAdministrativeExpenseMember" xlink:to="us-gaap_GeneralAndAdministrativeExpenseMember_lbl" xlink:type="arc" />
      <link:label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_GeneralAndAdministrativeExpenseMember_lbl" xml:lang="en-US">General and Administrative Expense [Member]</link:label>
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      <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="CLSN_NonVestedStockBasedCompensationArrangementsMember" xlink:to="CLSN_NonVestedStockBasedCompensationArrangementsMember_lbl" xlink:type="arc" />
      <link:label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="CLSN_NonVestedStockBasedCompensationArrangementsMember_lbl" xml:lang="en-US">Non-Vested Stock-Based Compensation Arrangements [Member]</link:label>
      <link:loc xlink:type="locator" xlink:href="clsn-20200630.xsd#CLSN_TwoThousandNineteenBonusProgramMember" xlink:label="CLSN_TwoThousandNineteenBonusProgramMember" />
      <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="CLSN_TwoThousandNineteenBonusProgramMember" xlink:to="CLSN_TwoThousandNineteenBonusProgramMember_lbl" xlink:type="arc" />
      <link:label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="CLSN_TwoThousandNineteenBonusProgramMember_lbl" xml:lang="en-US">2019 Bonus Program [Member]</link:label>
      <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_RestrictedStockMember" xlink:to="us-gaap_RestrictedStockMember_2_lbl" xlink:type="arc" />
      <link:label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/verboseLabel" xlink:label="us-gaap_RestrictedStockMember_2_lbl" xml:lang="en-US">Restricted Stock [Member]</link:label>
      <link:loc xlink:type="locator" xlink:href="clsn-20200630.xsd#CLSN_FairValueEarnoutMilestoneLiabilityMember" xlink:label="CLSN_FairValueEarnoutMilestoneLiabilityMember" />
      <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="CLSN_FairValueEarnoutMilestoneLiabilityMember" xlink:to="CLSN_FairValueEarnoutMilestoneLiabilityMember_lbl" xlink:type="arc" />
      <link:label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="CLSN_FairValueEarnoutMilestoneLiabilityMember_lbl" xml:lang="en-US">Fair Value Earnout Milestone Liability [Member]</link:label>
      <link:loc xlink:type="locator" xlink:href="clsn-20200630.xsd#CLSN_PaymentOptionOneMember" xlink:label="CLSN_PaymentOptionOneMember" />
      <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="CLSN_PaymentOptionOneMember" xlink:to="CLSN_PaymentOptionOneMember_lbl" xlink:type="arc" />
      <link:label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="CLSN_PaymentOptionOneMember_lbl" xml:lang="en-US">Payment Option One [Member]</link:label>
      <link:loc xlink:type="locator" xlink:href="clsn-20200630.xsd#CLSN_AmendedAssetPurchaseAgreementOptionPaymentOneMember" xlink:label="CLSN_AmendedAssetPurchaseAgreementOptionPaymentOneMember" />
      <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="CLSN_AmendedAssetPurchaseAgreementOptionPaymentOneMember" xlink:to="CLSN_AmendedAssetPurchaseAgreementOptionPaymentOneMember_lbl" xlink:type="arc" />
      <link:label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="CLSN_AmendedAssetPurchaseAgreementOptionPaymentOneMember_lbl" xml:lang="en-US">Amended Asset Purchase Agreement Option Payment 1 [Member]</link:label>
      <link:loc xlink:type="locator" xlink:href="clsn-20200630.xsd#CLSN_EGWUIncMember" xlink:label="CLSN_EGWUIncMember" />
      <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="CLSN_EGWUIncMember" xlink:to="CLSN_EGWUIncMember_lbl" xlink:type="arc" />
      <link:label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="CLSN_EGWUIncMember_lbl" xml:lang="en-US">EGWU, Inc [Member]</link:label>
      <link:loc xlink:type="locator" xlink:href="clsn-20200630.xsd#CLSN_AllOtherWarrantsMember" xlink:label="CLSN_AllOtherWarrantsMember" />
      <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="CLSN_AllOtherWarrantsMember" xlink:to="CLSN_AllOtherWarrantsMember_lbl" xlink:type="arc" />
      <link:label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="CLSN_AllOtherWarrantsMember_lbl" xml:lang="en-US">All Other Warrants [Member]</link:label>
      <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_AdjustmentsForNewAccountingPronouncementsAxis" xlink:label="us-gaap_AdjustmentsForNewAccountingPronouncementsAxis" />
      <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_AdjustmentsForNewAccountingPronouncementsAxis" xlink:to="us-gaap_AdjustmentsForNewAccountingPronouncementsAxis_lbl" xlink:type="arc" />
      <link:label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_AdjustmentsForNewAccountingPronouncementsAxis_lbl" xml:lang="en-US">Adjustments for New Accounting Pronouncements [Axis]</link:label>
      <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_AccountingStandardsUpdate201602Member" xlink:label="us-gaap_AccountingStandardsUpdate201602Member" />
      <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_AccountingStandardsUpdate201602Member" xlink:to="us-gaap_AccountingStandardsUpdate201602Member_lbl" xlink:type="arc" />
      <link:label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_AccountingStandardsUpdate201602Member_lbl" xml:lang="en-US">Accounting Standards Update 2016-02 [Member]</link:label>
      <link:loc xlink:type="locator" xlink:href="clsn-20200630.xsd#CLSN_AprilPaycheckProtectionProgramLoanMember" xlink:label="CLSN_AprilPaycheckProtectionProgramLoanMember" />
      <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="CLSN_AprilPaycheckProtectionProgramLoanMember" xlink:to="CLSN_AprilPaycheckProtectionProgramLoanMember_lbl" xlink:type="arc" />
      <link:label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="CLSN_AprilPaycheckProtectionProgramLoanMember_lbl" xml:lang="en-US">April PPP Loan [Member]</link:label>
      <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/srt/2020/elts/srt-2020-01-31.xsd#srt_CounterpartyNameAxis" xlink:label="srt_CounterpartyNameAxis" />
      <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="srt_CounterpartyNameAxis" xlink:to="srt_CounterpartyNameAxis_lbl" xlink:type="arc" />
      <link:label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="srt_CounterpartyNameAxis_lbl" xml:lang="en-US">Counterparty Name [Axis]</link:label>
      <link:loc xlink:type="locator" xlink:href="clsn-20200630.xsd#CLSN_SiliconValleyBankMember" xlink:label="CLSN_SiliconValleyBankMember" />
      <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="CLSN_SiliconValleyBankMember" xlink:to="CLSN_SiliconValleyBankMember_lbl" xlink:type="arc" />
      <link:label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="CLSN_SiliconValleyBankMember_lbl" xml:lang="en-US">Silicon Valley Bank [Member]</link:label>
      <link:loc xlink:type="locator" xlink:href="clsn-20200630.xsd#CLSN_PaycheckProtectionProgramLoansMember" xlink:label="CLSN_PaycheckProtectionProgramLoansMember" />
      <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="CLSN_PaycheckProtectionProgramLoansMember" xlink:to="CLSN_PaycheckProtectionProgramLoansMember_lbl" xlink:type="arc" />
      <link:label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="CLSN_PaycheckProtectionProgramLoansMember_lbl" xml:lang="en-US">PPP Loans [Member]</link:label>
      <link:loc xlink:type="locator" xlink:href="clsn-20200630.xsd#CLSN_MayPaycheckProtectionProgramLoanMember" xlink:label="CLSN_MayPaycheckProtectionProgramLoanMember" />
      <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="CLSN_MayPaycheckProtectionProgramLoanMember" xlink:to="CLSN_MayPaycheckProtectionProgramLoanMember_lbl" xlink:type="arc" />
      <link:label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="CLSN_MayPaycheckProtectionProgramLoanMember_lbl" xml:lang="en-US">May PPP Loan [Member]</link:label>
      <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_LongtermDebtTypeAxis" xlink:label="us-gaap_LongtermDebtTypeAxis" />
      <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_LongtermDebtTypeAxis" xlink:to="us-gaap_LongtermDebtTypeAxis_lbl" xlink:type="arc" />
      <link:label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_LongtermDebtTypeAxis_lbl" xml:lang="en-US">Long-term Debt, Type [Axis]</link:label>
      <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_NotesPayableToBanksMember" xlink:label="us-gaap_NotesPayableToBanksMember" />
      <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_NotesPayableToBanksMember" xlink:to="us-gaap_NotesPayableToBanksMember_lbl" xlink:type="arc" />
      <link:label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_NotesPayableToBanksMember_lbl" xml:lang="en-US">Promissory Note [Member]</link:label>
      <link:loc xlink:type="locator" xlink:href="clsn-20200630.xsd#CLSN_UnderwritingAgreementMember" xlink:label="CLSN_UnderwritingAgreementMember" />
      <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="CLSN_UnderwritingAgreementMember" xlink:to="CLSN_UnderwritingAgreementMember_lbl" xlink:type="arc" />
      <link:label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="CLSN_UnderwritingAgreementMember_lbl" xml:lang="en-US">Underwriting Agreement [Member]</link:label>
      <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_SubsidiarySaleOfStockAxis" xlink:label="us-gaap_SubsidiarySaleOfStockAxis" />
      <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_SubsidiarySaleOfStockAxis" xlink:to="us-gaap_SubsidiarySaleOfStockAxis_lbl" xlink:type="arc" />
      <link:label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_SubsidiarySaleOfStockAxis_lbl" xml:lang="en-US">Sale of Stock [Axis]</link:label>
      <link:loc xlink:type="locator" xlink:href="clsn-20200630.xsd#CLSN_UnderwrittenOfferingMember" xlink:label="CLSN_UnderwrittenOfferingMember" />
      <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="CLSN_UnderwrittenOfferingMember" xlink:to="CLSN_UnderwrittenOfferingMember_lbl" xlink:type="arc" />
      <link:label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="CLSN_UnderwrittenOfferingMember_lbl" xml:lang="en-US">Underwritten Offering [Member]</link:label>
      <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_AdditionalPaidInCapitalMember" xlink:to="us-gaap_AdditionalPaidInCapitalMember_2_lbl" xlink:type="arc" />
      <link:label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/verboseLabel" xlink:label="us-gaap_AdditionalPaidInCapitalMember_2_lbl" xml:lang="en-US">Additional Paid-In Capital [Member]</link:label>
      <link:loc xlink:type="locator" xlink:href="clsn-20200630.xsd#CLSN_PaymentOptionTwoMember" xlink:label="CLSN_PaymentOptionTwoMember" />
      <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="CLSN_PaymentOptionTwoMember" xlink:to="CLSN_PaymentOptionTwoMember_lbl" xlink:type="arc" />
      <link:label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="CLSN_PaymentOptionTwoMember_lbl" xml:lang="en-US">Payment Option Two [Member]</link:label>
      <link:loc xlink:type="locator" xlink:href="clsn-20200630.xsd#CLSN_AmendedAssetPurchaseAgreementOptionPaymentTwoMember" xlink:label="CLSN_AmendedAssetPurchaseAgreementOptionPaymentTwoMember" />
      <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="CLSN_AmendedAssetPurchaseAgreementOptionPaymentTwoMember" xlink:to="CLSN_AmendedAssetPurchaseAgreementOptionPaymentTwoMember_lbl" xlink:type="arc" />
      <link:label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="CLSN_AmendedAssetPurchaseAgreementOptionPaymentTwoMember_lbl" xml:lang="en-US">Amended Asset Purchase Agreement Option Payment 2 [Member]</link:label>
      <link:loc xlink:type="locator" xlink:href="clsn-20200630.xsd#CLSN_LawrencevilleNewJerseyMember" xlink:label="CLSN_LawrencevilleNewJerseyMember" />
      <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="CLSN_LawrencevilleNewJerseyMember" xlink:to="CLSN_LawrencevilleNewJerseyMember_lbl" xlink:type="arc" />
      <link:label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="CLSN_LawrencevilleNewJerseyMember_lbl" xml:lang="en-US">Lawrenceville, New Jersey [Member]</link:label>
      <link:loc xlink:type="locator" xlink:href="clsn-20200630.xsd#CLSN_HuntsvilleAlabamaMember" xlink:label="CLSN_HuntsvilleAlabamaMember" />
      <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="CLSN_HuntsvilleAlabamaMember" xlink:to="CLSN_HuntsvilleAlabamaMember_lbl" xlink:type="arc" />
      <link:label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="CLSN_HuntsvilleAlabamaMember_lbl" xml:lang="en-US">Huntsville Alabama [Member]</link:label>
      <link:loc xlink:type="locator" xlink:href="https://xbrl.sec.gov/dei/2020/dei-2020-01-31.xsd#dei_CoverAbstract" xlink:label="dei_CoverAbstract" />
      <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="dei_CoverAbstract" xlink:to="dei_CoverAbstract_lbl" xlink:type="arc" />
      <link:label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="dei_CoverAbstract_lbl" xml:lang="en-US">Cover [Abstract]</link:label>
      <link:loc xlink:type="locator" xlink:href="https://xbrl.sec.gov/dei/2020/dei-2020-01-31.xsd#dei_EntityRegistrantName" xlink:label="dei_EntityRegistrantName" />
      <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="dei_EntityRegistrantName" xlink:to="dei_EntityRegistrantName_lbl" xlink:type="arc" />
      <link:label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="dei_EntityRegistrantName_lbl" xml:lang="en-US">Entity Registrant Name</link:label>
      <link:loc xlink:type="locator" xlink:href="https://xbrl.sec.gov/dei/2020/dei-2020-01-31.xsd#dei_EntityCentralIndexKey" xlink:label="dei_EntityCentralIndexKey" />
      <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="dei_EntityCentralIndexKey" xlink:to="dei_EntityCentralIndexKey_lbl" xlink:type="arc" />
      <link:label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="dei_EntityCentralIndexKey_lbl" xml:lang="en-US">Entity Central Index Key</link:label>
      <link:loc xlink:type="locator" xlink:href="https://xbrl.sec.gov/dei/2020/dei-2020-01-31.xsd#dei_DocumentType" xlink:label="dei_DocumentType" />
      <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="dei_DocumentType" xlink:to="dei_DocumentType_lbl" xlink:type="arc" />
      <link:label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="dei_DocumentType_lbl" xml:lang="en-US">Document Type</link:label>
      <link:loc xlink:type="locator" xlink:href="https://xbrl.sec.gov/dei/2020/dei-2020-01-31.xsd#dei_DocumentPeriodEndDate" xlink:label="dei_DocumentPeriodEndDate" />
      <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="dei_DocumentPeriodEndDate" xlink:to="dei_DocumentPeriodEndDate_lbl" xlink:type="arc" />
      <link:label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="dei_DocumentPeriodEndDate_lbl" xml:lang="en-US">Document Period End Date</link:label>
      <link:loc xlink:type="locator" xlink:href="https://xbrl.sec.gov/dei/2020/dei-2020-01-31.xsd#dei_AmendmentFlag" xlink:label="dei_AmendmentFlag" />
      <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="dei_AmendmentFlag" xlink:to="dei_AmendmentFlag_lbl" xlink:type="arc" />
      <link:label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="dei_AmendmentFlag_lbl" xml:lang="en-US">Amendment Flag</link:label>
      <link:loc xlink:type="locator" xlink:href="https://xbrl.sec.gov/dei/2020/dei-2020-01-31.xsd#dei_CurrentFiscalYearEndDate" xlink:label="dei_CurrentFiscalYearEndDate" />
      <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="dei_CurrentFiscalYearEndDate" xlink:to="dei_CurrentFiscalYearEndDate_lbl" xlink:type="arc" />
      <link:label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="dei_CurrentFiscalYearEndDate_lbl" xml:lang="en-US">Current Fiscal Year End Date</link:label>
      <link:loc xlink:type="locator" xlink:href="https://xbrl.sec.gov/dei/2020/dei-2020-01-31.xsd#dei_EntityCurrentReportingStatus" xlink:label="dei_EntityCurrentReportingStatus" />
      <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="dei_EntityCurrentReportingStatus" xlink:to="dei_EntityCurrentReportingStatus_lbl" xlink:type="arc" />
      <link:label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="dei_EntityCurrentReportingStatus_lbl" xml:lang="en-US">Entity Current Reporting Status</link:label>
      <link:loc xlink:type="locator" xlink:href="https://xbrl.sec.gov/dei/2020/dei-2020-01-31.xsd#dei_EntityInteractiveDataCurrent" xlink:label="dei_EntityInteractiveDataCurrent" />
      <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="dei_EntityInteractiveDataCurrent" xlink:to="dei_EntityInteractiveDataCurrent_lbl" xlink:type="arc" />
      <link:label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="dei_EntityInteractiveDataCurrent_lbl" xml:lang="en-US">Entity Interactive Data Current</link:label>
      <link:loc xlink:type="locator" xlink:href="https://xbrl.sec.gov/dei/2020/dei-2020-01-31.xsd#dei_EntityFilerCategory" xlink:label="dei_EntityFilerCategory" />
      <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="dei_EntityFilerCategory" xlink:to="dei_EntityFilerCategory_lbl" xlink:type="arc" />
      <link:label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="dei_EntityFilerCategory_lbl" xml:lang="en-US">Entity Filer Category</link:label>
      <link:loc xlink:type="locator" xlink:href="https://xbrl.sec.gov/dei/2020/dei-2020-01-31.xsd#dei_EntitySmallBusiness" xlink:label="dei_EntitySmallBusiness" />
      <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="dei_EntitySmallBusiness" xlink:to="dei_EntitySmallBusiness_lbl" xlink:type="arc" />
      <link:label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="dei_EntitySmallBusiness_lbl" xml:lang="en-US">Entity Small Business Flag</link:label>
      <link:loc xlink:type="locator" xlink:href="https://xbrl.sec.gov/dei/2020/dei-2020-01-31.xsd#dei_EntityEmergingGrowthCompany" xlink:label="dei_EntityEmergingGrowthCompany" />
      <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="dei_EntityEmergingGrowthCompany" xlink:to="dei_EntityEmergingGrowthCompany_lbl" xlink:type="arc" />
      <link:label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="dei_EntityEmergingGrowthCompany_lbl" xml:lang="en-US">Entity Emerging Growth Company</link:label>
      <link:loc xlink:type="locator" xlink:href="https://xbrl.sec.gov/dei/2020/dei-2020-01-31.xsd#dei_EntityShellCompany" xlink:label="dei_EntityShellCompany" />
      <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="dei_EntityShellCompany" xlink:to="dei_EntityShellCompany_lbl" xlink:type="arc" />
      <link:label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="dei_EntityShellCompany_lbl" xml:lang="en-US">Entity Shell Company</link:label>
      <link:loc xlink:type="locator" xlink:href="https://xbrl.sec.gov/dei/2020/dei-2020-01-31.xsd#dei_EntityCommonStockSharesOutstanding" xlink:label="dei_EntityCommonStockSharesOutstanding" />
      <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="dei_EntityCommonStockSharesOutstanding" xlink:to="dei_EntityCommonStockSharesOutstanding_lbl" xlink:type="arc" />
      <link:label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="dei_EntityCommonStockSharesOutstanding_lbl" xml:lang="en-US">Entity Common Stock, Shares Outstanding</link:label>
      <link:loc xlink:type="locator" xlink:href="https://xbrl.sec.gov/dei/2020/dei-2020-01-31.xsd#dei_DocumentFiscalPeriodFocus" xlink:label="dei_DocumentFiscalPeriodFocus" />
      <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="dei_DocumentFiscalPeriodFocus" xlink:to="dei_DocumentFiscalPeriodFocus_lbl" xlink:type="arc" />
      <link:label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="dei_DocumentFiscalPeriodFocus_lbl" xml:lang="en-US">Document Fiscal Period Focus</link:label>
      <link:loc xlink:type="locator" xlink:href="https://xbrl.sec.gov/dei/2020/dei-2020-01-31.xsd#dei_DocumentFiscalYearFocus" xlink:label="dei_DocumentFiscalYearFocus" />
      <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="dei_DocumentFiscalYearFocus" xlink:to="dei_DocumentFiscalYearFocus_lbl" xlink:type="arc" />
      <link:label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="dei_DocumentFiscalYearFocus_lbl" xml:lang="en-US">Document Fiscal Year Focus</link:label>
      <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_StatementOfFinancialPositionAbstract" xlink:label="us-gaap_StatementOfFinancialPositionAbstract" />
      <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_StatementOfFinancialPositionAbstract" xlink:to="us-gaap_StatementOfFinancialPositionAbstract_lbl" xlink:type="arc" />
      <link:label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_StatementOfFinancialPositionAbstract_lbl" xml:lang="en-US">Statement of Financial Position [Abstract]</link:label>
      <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_AssetsAbstract" xlink:label="us-gaap_AssetsAbstract" />
      <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_AssetsAbstract" xlink:to="us-gaap_AssetsAbstract_lbl" xlink:type="arc" />
      <link:label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_AssetsAbstract_lbl" xml:lang="en-US">ASSETS</link:label>
      <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_AssetsCurrentAbstract" xlink:label="us-gaap_AssetsCurrentAbstract" />
      <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_AssetsCurrentAbstract" xlink:to="us-gaap_AssetsCurrentAbstract_lbl" xlink:type="arc" />
      <link:label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_AssetsCurrentAbstract_lbl" xml:lang="en-US">Current assets:</link:label>
      <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_CashAndCashEquivalentsAtCarryingValue" xlink:label="us-gaap_CashAndCashEquivalentsAtCarryingValue" />
      <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_CashAndCashEquivalentsAtCarryingValue" xlink:to="us-gaap_CashAndCashEquivalentsAtCarryingValue_lbl" xlink:type="arc" />
      <link:label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_CashAndCashEquivalentsAtCarryingValue_lbl" xml:lang="en-US">Cash and cash equivalents</link:label>
      <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_AvailableForSaleSecuritiesDebtSecuritiesCurrent" xlink:label="us-gaap_AvailableForSaleSecuritiesDebtSecuritiesCurrent" />
      <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_AvailableForSaleSecuritiesDebtSecuritiesCurrent" xlink:to="us-gaap_AvailableForSaleSecuritiesDebtSecuritiesCurrent_lbl" xlink:type="arc" />
      <link:label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_AvailableForSaleSecuritiesDebtSecuritiesCurrent_lbl" xml:lang="en-US">Investment in debt securities - available for sale, at fair value</link:label>
      <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_AccruedInvestmentIncomeReceivable" xlink:label="us-gaap_AccruedInvestmentIncomeReceivable" />
      <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_AccruedInvestmentIncomeReceivable" xlink:to="us-gaap_AccruedInvestmentIncomeReceivable_lbl" xlink:type="arc" />
      <link:label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_AccruedInvestmentIncomeReceivable_lbl" xml:lang="en-US">Accrued interest receivable on investment securities</link:label>
      <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_GrantsReceivableCurrent" xlink:label="us-gaap_GrantsReceivableCurrent" />
      <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_GrantsReceivableCurrent" xlink:to="us-gaap_GrantsReceivableCurrent_lbl" xlink:type="arc" />
      <link:label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_GrantsReceivableCurrent_lbl" xml:lang="en-US">Advances and deposits on clinical programs and other current assets</link:label>
      <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_AssetsCurrent" xlink:label="us-gaap_AssetsCurrent" />
      <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_AssetsCurrent" xlink:to="us-gaap_AssetsCurrent_lbl" xlink:type="arc" />
      <link:label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/totalLabel" xlink:label="us-gaap_AssetsCurrent_lbl" xml:lang="en-US">Total current assets</link:label>
      <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_PropertyPlantAndEquipmentNet" xlink:label="us-gaap_PropertyPlantAndEquipmentNet" />
      <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_PropertyPlantAndEquipmentNet" xlink:to="us-gaap_PropertyPlantAndEquipmentNet_lbl" xlink:type="arc" />
      <link:label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_PropertyPlantAndEquipmentNet_lbl" xml:lang="en-US">Property and equipment (at cost, less accumulated depreciation of $3,174,681 and $3,096,681, respectively)</link:label>
      <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_OtherAssetsAbstract" xlink:label="us-gaap_OtherAssetsAbstract" />
      <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_OtherAssetsAbstract" xlink:to="us-gaap_OtherAssetsAbstract_lbl" xlink:type="arc" />
      <link:label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_OtherAssetsAbstract_lbl" xml:lang="en-US">Other assets:</link:label>
      <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_DeferredIncomeTaxAssetsNet" xlink:label="us-gaap_DeferredIncomeTaxAssetsNet" />
      <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_DeferredIncomeTaxAssetsNet" xlink:to="us-gaap_DeferredIncomeTaxAssetsNet_lbl" xlink:type="arc" />
      <link:label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_DeferredIncomeTaxAssetsNet_lbl" xml:lang="en-US">Deferred tax asset</link:label>
      <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_IndefiniteLivedIntangibleAssetsExcludingGoodwill" xlink:label="us-gaap_IndefiniteLivedIntangibleAssetsExcludingGoodwill" />
      <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_IndefiniteLivedIntangibleAssetsExcludingGoodwill" xlink:to="us-gaap_IndefiniteLivedIntangibleAssetsExcludingGoodwill_lbl" xlink:type="arc" />
      <link:label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_IndefiniteLivedIntangibleAssetsExcludingGoodwill_lbl" xml:lang="en-US">In-process research and development, net</link:label>
      <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_Goodwill" xlink:label="us-gaap_Goodwill" />
      <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_Goodwill" xlink:to="us-gaap_Goodwill_lbl" xlink:type="arc" />
      <link:label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_Goodwill_lbl" xml:lang="en-US">Goodwill</link:label>
      <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_OperatingLeaseRightOfUseAsset" xlink:label="us-gaap_OperatingLeaseRightOfUseAsset" />
      <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_OperatingLeaseRightOfUseAsset" xlink:to="us-gaap_OperatingLeaseRightOfUseAsset_lbl" xlink:type="arc" />
      <link:label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_OperatingLeaseRightOfUseAsset_lbl" xml:lang="en-US">Operating lease right-of-use assets, net</link:label>
      <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_FiniteLivedIntangibleAssetsNet" xlink:label="us-gaap_FiniteLivedIntangibleAssetsNet" />
      <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_FiniteLivedIntangibleAssetsNet" xlink:to="us-gaap_FiniteLivedIntangibleAssetsNet_lbl" xlink:type="arc" />
      <link:label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_FiniteLivedIntangibleAssetsNet_lbl" xml:lang="en-US">Other intangible assets, net</link:label>
      <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_DepositsAssetsNoncurrent" xlink:label="us-gaap_DepositsAssetsNoncurrent" />
      <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_DepositsAssetsNoncurrent" xlink:to="us-gaap_DepositsAssetsNoncurrent_lbl" xlink:type="arc" />
      <link:label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_DepositsAssetsNoncurrent_lbl" xml:lang="en-US">Deposits and other assets</link:label>
      <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_AssetsNoncurrent" xlink:label="us-gaap_AssetsNoncurrent" />
      <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_AssetsNoncurrent" xlink:to="us-gaap_AssetsNoncurrent_lbl" xlink:type="arc" />
      <link:label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/totalLabel" xlink:label="us-gaap_AssetsNoncurrent_lbl" xml:lang="en-US">Total other assets</link:label>
      <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_Assets" xlink:label="us-gaap_Assets" />
      <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_Assets" xlink:to="us-gaap_Assets_lbl" xlink:type="arc" />
      <link:label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/totalLabel" xlink:label="us-gaap_Assets_lbl" xml:lang="en-US">Total assets</link:label>
      <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_LiabilitiesAndStockholdersEquityAbstract" xlink:label="us-gaap_LiabilitiesAndStockholdersEquityAbstract" />
      <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_LiabilitiesAndStockholdersEquityAbstract" xlink:to="us-gaap_LiabilitiesAndStockholdersEquityAbstract_lbl" xlink:type="arc" />
      <link:label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_LiabilitiesAndStockholdersEquityAbstract_lbl" xml:lang="en-US">LIABILITIES AND STOCKHOLDERS' EQUITY</link:label>
      <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_LiabilitiesCurrentAbstract" xlink:label="us-gaap_LiabilitiesCurrentAbstract" />
      <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_LiabilitiesCurrentAbstract" xlink:to="us-gaap_LiabilitiesCurrentAbstract_lbl" xlink:type="arc" />
      <link:label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_LiabilitiesCurrentAbstract_lbl" xml:lang="en-US">Current liabilities:</link:label>
      <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_AccountsPayableCurrent" xlink:label="us-gaap_AccountsPayableCurrent" />
      <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_AccountsPayableCurrent" xlink:to="us-gaap_AccountsPayableCurrent_lbl" xlink:type="arc" />
      <link:label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_AccountsPayableCurrent_lbl" xml:lang="en-US">Accounts payable - trade</link:label>
      <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_AccruedLiabilitiesCurrent" xlink:label="us-gaap_AccruedLiabilitiesCurrent" />
      <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_AccruedLiabilitiesCurrent" xlink:to="us-gaap_AccruedLiabilitiesCurrent_lbl" xlink:type="arc" />
      <link:label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_AccruedLiabilitiesCurrent_lbl" xml:lang="en-US">Other accrued liabilities</link:label>
      <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_NotesPayableCurrent" xlink:label="us-gaap_NotesPayableCurrent" />
      <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_NotesPayableCurrent" xlink:to="us-gaap_NotesPayableCurrent_lbl" xlink:type="arc" />
      <link:label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_NotesPayableCurrent_lbl" xml:lang="en-US">Notes payable - current portion, net of deferred financing costs</link:label>
      <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_OperatingLeaseLiabilityCurrent" xlink:label="us-gaap_OperatingLeaseLiabilityCurrent" />
      <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_OperatingLeaseLiabilityCurrent" xlink:to="us-gaap_OperatingLeaseLiabilityCurrent_lbl" xlink:type="arc" />
      <link:label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_OperatingLeaseLiabilityCurrent_lbl" xml:lang="en-US">Operating lease liability - current portion</link:label>
      <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ContractWithCustomerLiabilityCurrent" xlink:label="us-gaap_ContractWithCustomerLiabilityCurrent" />
      <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_ContractWithCustomerLiabilityCurrent" xlink:to="us-gaap_ContractWithCustomerLiabilityCurrent_lbl" xlink:type="arc" />
      <link:label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_ContractWithCustomerLiabilityCurrent_lbl" xml:lang="en-US">Deferred revenue - current portion</link:label>
      <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_LiabilitiesCurrent" xlink:label="us-gaap_LiabilitiesCurrent" />
      <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_LiabilitiesCurrent" xlink:to="us-gaap_LiabilitiesCurrent_lbl" xlink:type="arc" />
      <link:label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/totalLabel" xlink:label="us-gaap_LiabilitiesCurrent_lbl" xml:lang="en-US">Total current liabilities</link:label>
      <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_BusinessCombinationContingentConsiderationLiabilityNoncurrent" xlink:label="us-gaap_BusinessCombinationContingentConsiderationLiabilityNoncurrent" />
      <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_BusinessCombinationContingentConsiderationLiabilityNoncurrent" xlink:to="us-gaap_BusinessCombinationContingentConsiderationLiabilityNoncurrent_lbl" xlink:type="arc" />
      <link:label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_BusinessCombinationContingentConsiderationLiabilityNoncurrent_lbl" xml:lang="en-US">Earn-out milestone liability</link:label>
      <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_LongTermNotesPayable" xlink:label="us-gaap_LongTermNotesPayable" />
      <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_LongTermNotesPayable" xlink:to="us-gaap_LongTermNotesPayable_lbl" xlink:type="arc" />
      <link:label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_LongTermNotesPayable_lbl" xml:lang="en-US">Note payable, net of deferred financing costs</link:label>
      <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_OperatingLeaseLiabilityNoncurrent" xlink:label="us-gaap_OperatingLeaseLiabilityNoncurrent" />
      <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_OperatingLeaseLiabilityNoncurrent" xlink:to="us-gaap_OperatingLeaseLiabilityNoncurrent_lbl" xlink:type="arc" />
      <link:label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_OperatingLeaseLiabilityNoncurrent_lbl" xml:lang="en-US">Operating lease liability - non-current portion</link:label>
      <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_DeferredRevenueNoncurrent" xlink:label="us-gaap_DeferredRevenueNoncurrent" />
      <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_DeferredRevenueNoncurrent" xlink:to="us-gaap_DeferredRevenueNoncurrent_lbl" xlink:type="arc" />
      <link:label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_DeferredRevenueNoncurrent_lbl" xml:lang="en-US">Deferred revenue - non-current portion</link:label>
      <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_Liabilities" xlink:label="us-gaap_Liabilities" />
      <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_Liabilities" xlink:to="us-gaap_Liabilities_lbl" xlink:type="arc" />
      <link:label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/totalLabel" xlink:label="us-gaap_Liabilities_lbl" xml:lang="en-US">Total liabilities</link:label>
      <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_CommitmentsAndContingencies" xlink:label="us-gaap_CommitmentsAndContingencies" />
      <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_CommitmentsAndContingencies" xlink:to="us-gaap_CommitmentsAndContingencies_lbl" xlink:type="arc" />
      <link:label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_CommitmentsAndContingencies_lbl" xml:lang="en-US">Commitments and contingencies</link:label>
      <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_StockholdersEquityAbstract" xlink:label="us-gaap_StockholdersEquityAbstract" />
      <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_StockholdersEquityAbstract" xlink:to="us-gaap_StockholdersEquityAbstract_lbl" xlink:type="arc" />
      <link:label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_StockholdersEquityAbstract_lbl" xml:lang="en-US">Stockholders' equity:</link:label>
      <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_PreferredStockValue" xlink:label="us-gaap_PreferredStockValue" />
      <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_PreferredStockValue" xlink:to="us-gaap_PreferredStockValue_lbl" xlink:type="arc" />
      <link:label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_PreferredStockValue_lbl" xml:lang="en-US">Preferred stock - $0.01 par value (100,000 shares authorized, and no shares issued or outstanding at June 30, 2020 and December 31, 2019)</link:label>
      <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_CommonStockValue" xlink:label="us-gaap_CommonStockValue" />
      <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_CommonStockValue" xlink:to="us-gaap_CommonStockValue_lbl" xlink:type="arc" />
      <link:label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_CommonStockValue_lbl" xml:lang="en-US">Common stock - $0.01 par value (112,500,000 shares authorized; 33,229,714 and 23,256,152 shares issued at June 30, 2020 and December 31, 2019, respectively, and 33,229,380 and 23,255,818 shares outstanding at June 30, 2020 and December 31, 2019, respectively)</link:label>
      <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_AdditionalPaidInCapital" xlink:label="us-gaap_AdditionalPaidInCapital" />
      <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_AdditionalPaidInCapital" xlink:to="us-gaap_AdditionalPaidInCapital_lbl" xlink:type="arc" />
      <link:label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_AdditionalPaidInCapital_lbl" xml:lang="en-US">Additional paid-in capital</link:label>
      <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_AccumulatedOtherComprehensiveIncomeLossNetOfTax" xlink:label="us-gaap_AccumulatedOtherComprehensiveIncomeLossNetOfTax" />
      <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_AccumulatedOtherComprehensiveIncomeLossNetOfTax" xlink:to="us-gaap_AccumulatedOtherComprehensiveIncomeLossNetOfTax_lbl" xlink:type="arc" />
      <link:label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_AccumulatedOtherComprehensiveIncomeLossNetOfTax_lbl" xml:lang="en-US">Accumulated other comprehensive gain</link:label>
      <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_RetainedEarningsAccumulatedDeficit" xlink:label="us-gaap_RetainedEarningsAccumulatedDeficit" />
      <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_RetainedEarningsAccumulatedDeficit" xlink:to="us-gaap_RetainedEarningsAccumulatedDeficit_lbl" xlink:type="arc" />
      <link:label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_RetainedEarningsAccumulatedDeficit_lbl" xml:lang="en-US">Accumulated deficit</link:label>
      <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_StockholdersEquityBeforeTreasuryStock" xlink:label="us-gaap_StockholdersEquityBeforeTreasuryStock" />
      <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_StockholdersEquityBeforeTreasuryStock" xlink:to="us-gaap_StockholdersEquityBeforeTreasuryStock_lbl" xlink:type="arc" />
      <link:label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/totalLabel" xlink:label="us-gaap_StockholdersEquityBeforeTreasuryStock_lbl" xml:lang="en-US">Total stockholders' equity before treasury stock</link:label>
      <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_TreasuryStockValue" xlink:label="us-gaap_TreasuryStockValue" />
      <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_TreasuryStockValue" xlink:to="us-gaap_TreasuryStockValue_lbl" xlink:type="arc" />
      <link:label xlink:type="resource" xlink:role="http://www.xbrl.org/2009/role/negatedLabel" xlink:label="us-gaap_TreasuryStockValue_lbl" xml:lang="en-US">Treasury stock, at cost (334 shares at June 30, 2020 and December 31, 2019)</link:label>
      <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_StockholdersEquity" xlink:label="us-gaap_StockholdersEquity" />
      <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_StockholdersEquity" xlink:to="us-gaap_StockholdersEquity_lbl" xlink:type="arc" />
      <link:label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/totalLabel" xlink:label="us-gaap_StockholdersEquity_lbl" xml:lang="en-US">Total stockholders' equity</link:label>
      <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_LiabilitiesAndStockholdersEquity" xlink:label="us-gaap_LiabilitiesAndStockholdersEquity" />
      <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_LiabilitiesAndStockholdersEquity" xlink:to="us-gaap_LiabilitiesAndStockholdersEquity_lbl" xlink:type="arc" />
      <link:label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/totalLabel" xlink:label="us-gaap_LiabilitiesAndStockholdersEquity_lbl" xml:lang="en-US">Total liabilities and stockholders' equity</link:label>
      <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_PreferredStockParOrStatedValuePerShare" xlink:label="us-gaap_PreferredStockParOrStatedValuePerShare" />
      <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_PreferredStockParOrStatedValuePerShare" xlink:to="us-gaap_PreferredStockParOrStatedValuePerShare_lbl" xlink:type="arc" />
      <link:label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_PreferredStockParOrStatedValuePerShare_lbl" xml:lang="en-US">Preferred stock, par value</link:label>
      <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_PreferredStockSharesAuthorized" xlink:label="us-gaap_PreferredStockSharesAuthorized" />
      <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_PreferredStockSharesAuthorized" xlink:to="us-gaap_PreferredStockSharesAuthorized_lbl" xlink:type="arc" />
      <link:label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_PreferredStockSharesAuthorized_lbl" xml:lang="en-US">Preferred stock, shares authorized</link:label>
      <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_PreferredStockSharesIssued" xlink:label="us-gaap_PreferredStockSharesIssued" />
      <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_PreferredStockSharesIssued" xlink:to="us-gaap_PreferredStockSharesIssued_lbl" xlink:type="arc" />
      <link:label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_PreferredStockSharesIssued_lbl" xml:lang="en-US">Preferred stock, shares issued</link:label>
      <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_PreferredStockSharesOutstanding" xlink:label="us-gaap_PreferredStockSharesOutstanding" />
      <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_PreferredStockSharesOutstanding" xlink:to="us-gaap_PreferredStockSharesOutstanding_lbl" xlink:type="arc" />
      <link:label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_PreferredStockSharesOutstanding_lbl" xml:lang="en-US">Preferred stock, shares outstanding</link:label>
      <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_CommonStockParOrStatedValuePerShare" xlink:label="us-gaap_CommonStockParOrStatedValuePerShare" />
      <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_CommonStockParOrStatedValuePerShare" xlink:to="us-gaap_CommonStockParOrStatedValuePerShare_lbl" xlink:type="arc" />
      <link:label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_CommonStockParOrStatedValuePerShare_lbl" xml:lang="en-US">Common stock, par value</link:label>
      <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_CommonStockSharesAuthorized" xlink:label="us-gaap_CommonStockSharesAuthorized" />
      <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_CommonStockSharesAuthorized" xlink:to="us-gaap_CommonStockSharesAuthorized_lbl" xlink:type="arc" />
      <link:label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_CommonStockSharesAuthorized_lbl" xml:lang="en-US">Common stock, shares authorized</link:label>
      <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_CommonStockSharesIssued" xlink:label="us-gaap_CommonStockSharesIssued" />
      <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_CommonStockSharesIssued" xlink:to="us-gaap_CommonStockSharesIssued_lbl" xlink:type="arc" />
      <link:label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_CommonStockSharesIssued_lbl" xml:lang="en-US">Common stock, shares issued</link:label>
      <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_CommonStockSharesOutstanding" xlink:label="us-gaap_CommonStockSharesOutstanding" />
      <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_CommonStockSharesOutstanding" xlink:to="us-gaap_CommonStockSharesOutstanding_lbl" xlink:type="arc" />
      <link:label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_CommonStockSharesOutstanding_lbl" xml:lang="en-US">Common stock, shares outstanding</link:label>
      <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_TreasuryStockShares" xlink:label="us-gaap_TreasuryStockShares" />
      <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_TreasuryStockShares" xlink:to="us-gaap_TreasuryStockShares_lbl" xlink:type="arc" />
      <link:label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_TreasuryStockShares_lbl" xml:lang="en-US">Treasury stock, shares</link:label>
      <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_IncomeStatementAbstract" xlink:label="us-gaap_IncomeStatementAbstract" />
      <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_IncomeStatementAbstract" xlink:to="us-gaap_IncomeStatementAbstract_lbl" xlink:type="arc" />
      <link:label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_IncomeStatementAbstract_lbl" xml:lang="en-US">Income Statement [Abstract]</link:label>
      <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_RevenueFromContractWithCustomerExcludingAssessedTax" xlink:label="us-gaap_RevenueFromContractWithCustomerExcludingAssessedTax" />
      <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_RevenueFromContractWithCustomerExcludingAssessedTax" xlink:to="us-gaap_RevenueFromContractWithCustomerExcludingAssessedTax_lbl" xlink:type="arc" />
      <link:label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_RevenueFromContractWithCustomerExcludingAssessedTax_lbl" xml:lang="en-US">Licensing revenue</link:label>
      <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_OperatingExpensesAbstract" xlink:label="us-gaap_OperatingExpensesAbstract" />
      <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_OperatingExpensesAbstract" xlink:to="us-gaap_OperatingExpensesAbstract_lbl" xlink:type="arc" />
      <link:label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_OperatingExpensesAbstract_lbl" xml:lang="en-US">Operating expenses:</link:label>
      <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ResearchAndDevelopmentExpense" xlink:label="us-gaap_ResearchAndDevelopmentExpense" />
      <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_ResearchAndDevelopmentExpense" xlink:to="us-gaap_ResearchAndDevelopmentExpense_lbl" xlink:type="arc" />
      <link:label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_ResearchAndDevelopmentExpense_lbl" xml:lang="en-US">Research and development</link:label>
      <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_GeneralAndAdministrativeExpense" xlink:label="us-gaap_GeneralAndAdministrativeExpense" />
      <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_GeneralAndAdministrativeExpense" xlink:to="us-gaap_GeneralAndAdministrativeExpense_lbl" xlink:type="arc" />
      <link:label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_GeneralAndAdministrativeExpense_lbl" xml:lang="en-US">General and administrative</link:label>
      <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_OperatingExpenses" xlink:label="us-gaap_OperatingExpenses" />
      <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_OperatingExpenses" xlink:to="us-gaap_OperatingExpenses_lbl" xlink:type="arc" />
      <link:label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/totalLabel" xlink:label="us-gaap_OperatingExpenses_lbl" xml:lang="en-US">Total operating expenses</link:label>
      <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_OperatingIncomeLoss" xlink:label="us-gaap_OperatingIncomeLoss" />
      <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_OperatingIncomeLoss" xlink:to="us-gaap_OperatingIncomeLoss_lbl" xlink:type="arc" />
      <link:label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/totalLabel" xlink:label="us-gaap_OperatingIncomeLoss_lbl" xml:lang="en-US">Loss from operations</link:label>
      <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_OtherIncomeAndExpensesAbstract" xlink:label="us-gaap_OtherIncomeAndExpensesAbstract" />
      <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_OtherIncomeAndExpensesAbstract" xlink:to="us-gaap_OtherIncomeAndExpensesAbstract_lbl" xlink:type="arc" />
      <link:label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_OtherIncomeAndExpensesAbstract_lbl" xml:lang="en-US">Other (expense) income:</link:label>
      <link:loc xlink:type="locator" xlink:href="clsn-20200630.xsd#CLSN_GainLossFromChangeInEarnoutMilestoneLiability" xlink:label="CLSN_GainLossFromChangeInEarnoutMilestoneLiability" />
      <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="CLSN_GainLossFromChangeInEarnoutMilestoneLiability" xlink:to="CLSN_GainLossFromChangeInEarnoutMilestoneLiability_lbl" xlink:type="arc" />
      <link:label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="CLSN_GainLossFromChangeInEarnoutMilestoneLiability_lbl" xml:lang="en-US">(Loss) gain from change in valuation of earn-out milestone liability</link:label>
      <link:loc xlink:type="locator" xlink:href="clsn-20200630.xsd#CLSN_FairValueOfWarrantsIssuedInConnectionWithAmendmentToModifyEarnoutMilestonePayments" xlink:label="CLSN_FairValueOfWarrantsIssuedInConnectionWithAmendmentToModifyEarnoutMilestonePayments" />
      <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="CLSN_FairValueOfWarrantsIssuedInConnectionWithAmendmentToModifyEarnoutMilestonePayments" xlink:to="CLSN_FairValueOfWarrantsIssuedInConnectionWithAmendmentToModifyEarnoutMilestonePayments_lbl" xlink:type="arc" />
      <link:label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="CLSN_FairValueOfWarrantsIssuedInConnectionWithAmendmentToModifyEarnoutMilestonePayments_lbl" xml:lang="en-US">Fair value of warrants issued in connection with amendment to modify GEN-1 earn-out milestone payments</link:label>
      <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_InvestmentIncomeNonoperating" xlink:label="us-gaap_InvestmentIncomeNonoperating" />
      <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_InvestmentIncomeNonoperating" xlink:to="us-gaap_InvestmentIncomeNonoperating_lbl" xlink:type="arc" />
      <link:label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_InvestmentIncomeNonoperating_lbl" xml:lang="en-US">Investment income</link:label>
      <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_InterestAndDebtExpense" xlink:label="us-gaap_InterestAndDebtExpense" />
      <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_InterestAndDebtExpense" xlink:to="us-gaap_InterestAndDebtExpense_lbl" xlink:type="arc" />
      <link:label xlink:type="resource" xlink:role="http://www.xbrl.org/2009/role/negatedLabel" xlink:label="us-gaap_InterestAndDebtExpense_lbl" xml:lang="en-US">Interest expense</link:label>
      <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_OtherNonoperatingIncomeExpense" xlink:label="us-gaap_OtherNonoperatingIncomeExpense" />
      <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_OtherNonoperatingIncomeExpense" xlink:to="us-gaap_OtherNonoperatingIncomeExpense_lbl" xlink:type="arc" />
      <link:label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_OtherNonoperatingIncomeExpense_lbl" xml:lang="en-US">Other (expense) income</link:label>
      <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_NonoperatingIncomeExpense" xlink:label="us-gaap_NonoperatingIncomeExpense" />
      <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_NonoperatingIncomeExpense" xlink:to="us-gaap_NonoperatingIncomeExpense_lbl" xlink:type="arc" />
      <link:label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/totalLabel" xlink:label="us-gaap_NonoperatingIncomeExpense_lbl" xml:lang="en-US">Total other (expense) income, net</link:label>
      <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_NetIncomeLoss" xlink:label="us-gaap_NetIncomeLoss" />
      <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_NetIncomeLoss" xlink:to="us-gaap_NetIncomeLoss_lbl" xlink:type="arc" />
      <link:label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/totalLabel" xlink:label="us-gaap_NetIncomeLoss_lbl" xml:lang="en-US">Net loss</link:label>
      <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_EarningsPerShareBasicAndDiluted" xlink:label="us-gaap_EarningsPerShareBasicAndDiluted" />
      <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_EarningsPerShareBasicAndDiluted" xlink:to="us-gaap_EarningsPerShareBasicAndDiluted_lbl" xlink:type="arc" />
      <link:label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_EarningsPerShareBasicAndDiluted_lbl" xml:lang="en-US">Net loss per common share - Basic and diluted</link:label>
      <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_WeightedAverageNumberOfShareOutstandingBasicAndDiluted" xlink:label="us-gaap_WeightedAverageNumberOfShareOutstandingBasicAndDiluted" />
      <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_WeightedAverageNumberOfShareOutstandingBasicAndDiluted" xlink:to="us-gaap_WeightedAverageNumberOfShareOutstandingBasicAndDiluted_lbl" xlink:type="arc" />
      <link:label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_WeightedAverageNumberOfShareOutstandingBasicAndDiluted_lbl" xml:lang="en-US">Weighted average shares outstanding - Basic and diluted</link:label>
      <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_StatementOfIncomeAndComprehensiveIncomeAbstract" xlink:label="us-gaap_StatementOfIncomeAndComprehensiveIncomeAbstract" />
      <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_StatementOfIncomeAndComprehensiveIncomeAbstract" xlink:to="us-gaap_StatementOfIncomeAndComprehensiveIncomeAbstract_lbl" xlink:type="arc" />
      <link:label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_StatementOfIncomeAndComprehensiveIncomeAbstract_lbl" xml:lang="en-US">Statement of Comprehensive Income [Abstract]</link:label>
      <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ComprehensiveIncomeNetOfTaxAbstract" xlink:label="us-gaap_ComprehensiveIncomeNetOfTaxAbstract" />
      <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_ComprehensiveIncomeNetOfTaxAbstract" xlink:to="us-gaap_ComprehensiveIncomeNetOfTaxAbstract_lbl" xlink:type="arc" />
      <link:label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_ComprehensiveIncomeNetOfTaxAbstract_lbl" xml:lang="en-US">Other comprehensive (loss) gain</link:label>
      <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_OtherComprehensiveIncomeAvailableforsaleSecuritiesAdjustmentNetOfTaxPortionAttributableToParentAbstract" xlink:label="us-gaap_OtherComprehensiveIncomeAvailableforsaleSecuritiesAdjustmentNetOfTaxPortionAttributableToParentAbstract" />
      <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_OtherComprehensiveIncomeAvailableforsaleSecuritiesAdjustmentNetOfTaxPortionAttributableToParentAbstract" xlink:to="us-gaap_OtherComprehensiveIncomeAvailableforsaleSecuritiesAdjustmentNetOfTaxPortionAttributableToParentAbstract_lbl" xlink:type="arc" />
      <link:label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_OtherComprehensiveIncomeAvailableforsaleSecuritiesAdjustmentNetOfTaxPortionAttributableToParentAbstract_lbl" xml:lang="en-US">Changes in:</link:label>
      <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIForSaleOfSecuritiesNetOfTax" xlink:label="us-gaap_OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIForSaleOfSecuritiesNetOfTax" />
      <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIForSaleOfSecuritiesNetOfTax" xlink:to="us-gaap_OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIForSaleOfSecuritiesNetOfTax_lbl" xlink:type="arc" />
      <link:label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIForSaleOfSecuritiesNetOfTax_lbl" xml:lang="en-US">Realized (gains) losses on investment securities recognized in investment income, net</link:label>
      <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_OtherComprehensiveIncomeUnrealizedHoldingGainLossOnSecuritiesArisingDuringPeriodNetOfTax" xlink:label="us-gaap_OtherComprehensiveIncomeUnrealizedHoldingGainLossOnSecuritiesArisingDuringPeriodNetOfTax" />
      <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_OtherComprehensiveIncomeUnrealizedHoldingGainLossOnSecuritiesArisingDuringPeriodNetOfTax" xlink:to="us-gaap_OtherComprehensiveIncomeUnrealizedHoldingGainLossOnSecuritiesArisingDuringPeriodNetOfTax_lbl" xlink:type="arc" />
      <link:label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_OtherComprehensiveIncomeUnrealizedHoldingGainLossOnSecuritiesArisingDuringPeriodNetOfTax_lbl" xml:lang="en-US">Unrealized gains on investment securities, net</link:label>
      <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_OtherComprehensiveIncomeLossAvailableForSaleSecuritiesAdjustmentNetOfTax" xlink:label="us-gaap_OtherComprehensiveIncomeLossAvailableForSaleSecuritiesAdjustmentNetOfTax" />
      <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_OtherComprehensiveIncomeLossAvailableForSaleSecuritiesAdjustmentNetOfTax" xlink:to="us-gaap_OtherComprehensiveIncomeLossAvailableForSaleSecuritiesAdjustmentNetOfTax_lbl" xlink:type="arc" />
      <link:label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/totalLabel" xlink:label="us-gaap_OtherComprehensiveIncomeLossAvailableForSaleSecuritiesAdjustmentNetOfTax_lbl" xml:lang="en-US">Change in unrealized (loss) gain, net, on available for sale securities</link:label>
      <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_NetIncomeLoss" xlink:to="us-gaap_NetIncomeLoss_2_lbl" xlink:type="arc" />
      <link:label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_NetIncomeLoss_2_lbl" xml:lang="en-US">Net loss</link:label>
      <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ComprehensiveIncomeNetOfTax" xlink:label="us-gaap_ComprehensiveIncomeNetOfTax" />
      <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_ComprehensiveIncomeNetOfTax" xlink:to="us-gaap_ComprehensiveIncomeNetOfTax_lbl" xlink:type="arc" />
      <link:label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/totalLabel" xlink:label="us-gaap_ComprehensiveIncomeNetOfTax_lbl" xml:lang="en-US">Comprehensive loss</link:label>
      <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_StatementOfCashFlowsAbstract" xlink:label="us-gaap_StatementOfCashFlowsAbstract" />
      <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_StatementOfCashFlowsAbstract" xlink:to="us-gaap_StatementOfCashFlowsAbstract_lbl" xlink:type="arc" />
      <link:label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_StatementOfCashFlowsAbstract_lbl" xml:lang="en-US">Statement of Cash Flows [Abstract]</link:label>
      <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_NetCashProvidedByUsedInOperatingActivitiesAbstract" xlink:label="us-gaap_NetCashProvidedByUsedInOperatingActivitiesAbstract" />
      <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_NetCashProvidedByUsedInOperatingActivitiesAbstract" xlink:to="us-gaap_NetCashProvidedByUsedInOperatingActivitiesAbstract_lbl" xlink:type="arc" />
      <link:label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_NetCashProvidedByUsedInOperatingActivitiesAbstract_lbl" xml:lang="en-US">Cash flows from operating activities:</link:label>
      <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_AdjustmentsNoncashItemsToReconcileNetIncomeLossToCashProvidedByUsedInOperatingActivitiesAbstract" xlink:label="us-gaap_AdjustmentsNoncashItemsToReconcileNetIncomeLossToCashProvidedByUsedInOperatingActivitiesAbstract" />
      <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_AdjustmentsNoncashItemsToReconcileNetIncomeLossToCashProvidedByUsedInOperatingActivitiesAbstract" xlink:to="us-gaap_AdjustmentsNoncashItemsToReconcileNetIncomeLossToCashProvidedByUsedInOperatingActivitiesAbstract_lbl" xlink:type="arc" />
      <link:label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_AdjustmentsNoncashItemsToReconcileNetIncomeLossToCashProvidedByUsedInOperatingActivitiesAbstract_lbl" xml:lang="en-US">Adjustments to reconcile net loss to net cash from operating activities:</link:label>
      <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_DepreciationDepletionAndAmortization" xlink:label="us-gaap_DepreciationDepletionAndAmortization" />
      <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_DepreciationDepletionAndAmortization" xlink:to="us-gaap_DepreciationDepletionAndAmortization_lbl" xlink:type="arc" />
      <link:label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_DepreciationDepletionAndAmortization_lbl" xml:lang="en-US">Depreciation and amortization</link:label>
      <link:loc xlink:type="locator" xlink:href="clsn-20200630.xsd#CLSN_GainLossFromValuationOfEarnoutMilestoneLiability" xlink:label="CLSN_GainLossFromValuationOfEarnoutMilestoneLiability" />
      <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="CLSN_GainLossFromValuationOfEarnoutMilestoneLiability" xlink:to="CLSN_GainLossFromValuationOfEarnoutMilestoneLiability_lbl" xlink:type="arc" />
      <link:label xlink:type="resource" xlink:role="http://www.xbrl.org/2009/role/negatedLabel" xlink:label="CLSN_GainLossFromValuationOfEarnoutMilestoneLiability_lbl" xml:lang="en-US">Change in fair value of earn-out milestone liability</link:label>
      <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="CLSN_FairValueOfWarrantsIssuedInConnectionWithAmendmentToModifyEarnoutMilestonePayments" xlink:to="CLSN_FairValueOfWarrantsIssuedInConnectionWithAmendmentToModifyEarnoutMilestonePayments_2_lbl" xlink:type="arc" />
      <link:label xlink:type="resource" xlink:role="http://www.xbrl.org/2009/role/negatedLabel" xlink:label="CLSN_FairValueOfWarrantsIssuedInConnectionWithAmendmentToModifyEarnoutMilestonePayments_2_lbl" xml:lang="en-US">Fair value of warrants issued in connection with amendment to modify the GEN-1 earn-out milestone payments</link:label>
      <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ContractWithCustomerLiabilityRevenueRecognized" xlink:label="us-gaap_ContractWithCustomerLiabilityRevenueRecognized" />
      <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_ContractWithCustomerLiabilityRevenueRecognized" xlink:to="us-gaap_ContractWithCustomerLiabilityRevenueRecognized_lbl" xlink:type="arc" />
      <link:label xlink:type="resource" xlink:role="http://www.xbrl.org/2009/role/negatedLabel" xlink:label="us-gaap_ContractWithCustomerLiabilityRevenueRecognized_lbl" xml:lang="en-US">Recognition of deferred revenue</link:label>
      <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ShareBasedCompensation" xlink:label="us-gaap_ShareBasedCompensation" />
      <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_ShareBasedCompensation" xlink:to="us-gaap_ShareBasedCompensation_lbl" xlink:type="arc" />
      <link:label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_ShareBasedCompensation_lbl" xml:lang="en-US">Stock-based compensation costs</link:label>
      <link:loc xlink:type="locator" xlink:href="clsn-20200630.xsd#CLSN_SharesIssuedInExchangeForServices" xlink:label="CLSN_SharesIssuedInExchangeForServices" />
      <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="CLSN_SharesIssuedInExchangeForServices" xlink:to="CLSN_SharesIssuedInExchangeForServices_lbl" xlink:type="arc" />
      <link:label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="CLSN_SharesIssuedInExchangeForServices_lbl" xml:lang="en-US">Shares issued in exchange for services</link:label>
      <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_DeferredIncomeTaxExpenseBenefit" xlink:label="us-gaap_DeferredIncomeTaxExpenseBenefit" />
      <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_DeferredIncomeTaxExpenseBenefit" xlink:to="us-gaap_DeferredIncomeTaxExpenseBenefit_lbl" xlink:type="arc" />
      <link:label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_DeferredIncomeTaxExpenseBenefit_lbl" xml:lang="en-US">Deferred income tax asset</link:label>
      <link:loc xlink:type="locator" xlink:href="clsn-20200630.xsd#CLSN_AmortizationOfDeferredFinanceChargesAndDebtDiscountAssociatedWithNotePayable" xlink:label="CLSN_AmortizationOfDeferredFinanceChargesAndDebtDiscountAssociatedWithNotePayable" />
      <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="CLSN_AmortizationOfDeferredFinanceChargesAndDebtDiscountAssociatedWithNotePayable" xlink:to="CLSN_AmortizationOfDeferredFinanceChargesAndDebtDiscountAssociatedWithNotePayable_lbl" xlink:type="arc" />
      <link:label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="CLSN_AmortizationOfDeferredFinanceChargesAndDebtDiscountAssociatedWithNotePayable_lbl" xml:lang="en-US">Amortization of deferred finance charges and debt discount associated with notes payable</link:label>
      <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_IncreaseDecreaseInOperatingCapitalAbstract" xlink:label="us-gaap_IncreaseDecreaseInOperatingCapitalAbstract" />
      <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_IncreaseDecreaseInOperatingCapitalAbstract" xlink:to="us-gaap_IncreaseDecreaseInOperatingCapitalAbstract_lbl" xlink:type="arc" />
      <link:label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_IncreaseDecreaseInOperatingCapitalAbstract_lbl" xml:lang="en-US">Net changes in:</link:label>
      <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_IncreaseDecreaseInAccruedInvestmentIncomeReceivable" xlink:label="us-gaap_IncreaseDecreaseInAccruedInvestmentIncomeReceivable" />
      <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_IncreaseDecreaseInAccruedInvestmentIncomeReceivable" xlink:to="us-gaap_IncreaseDecreaseInAccruedInvestmentIncomeReceivable_lbl" xlink:type="arc" />
      <link:label xlink:type="resource" xlink:role="http://www.xbrl.org/2009/role/negatedLabel" xlink:label="us-gaap_IncreaseDecreaseInAccruedInvestmentIncomeReceivable_lbl" xml:lang="en-US">Accrued interest on investment securities</link:label>
      <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_IncreaseDecreaseInPrepaidDeferredExpenseAndOtherAssets" xlink:label="us-gaap_IncreaseDecreaseInPrepaidDeferredExpenseAndOtherAssets" />
      <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_IncreaseDecreaseInPrepaidDeferredExpenseAndOtherAssets" xlink:to="us-gaap_IncreaseDecreaseInPrepaidDeferredExpenseAndOtherAssets_lbl" xlink:type="arc" />
      <link:label xlink:type="resource" xlink:role="http://www.xbrl.org/2009/role/negatedLabel" xlink:label="us-gaap_IncreaseDecreaseInPrepaidDeferredExpenseAndOtherAssets_lbl" xml:lang="en-US">Advances, deposits and other current assets</link:label>
      <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_IncreaseDecreaseInAccountsPayableAndAccruedLiabilities" xlink:label="us-gaap_IncreaseDecreaseInAccountsPayableAndAccruedLiabilities" />
      <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_IncreaseDecreaseInAccountsPayableAndAccruedLiabilities" xlink:to="us-gaap_IncreaseDecreaseInAccountsPayableAndAccruedLiabilities_lbl" xlink:type="arc" />
      <link:label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_IncreaseDecreaseInAccountsPayableAndAccruedLiabilities_lbl" xml:lang="en-US">Accounts payable and accrued liabilities</link:label>
      <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_NetCashProvidedByUsedInOperatingActivities" xlink:label="us-gaap_NetCashProvidedByUsedInOperatingActivities" />
      <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_NetCashProvidedByUsedInOperatingActivities" xlink:to="us-gaap_NetCashProvidedByUsedInOperatingActivities_lbl" xlink:type="arc" />
      <link:label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/totalLabel" xlink:label="us-gaap_NetCashProvidedByUsedInOperatingActivities_lbl" xml:lang="en-US">Net cash (used in) operating activities:</link:label>
      <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_NetCashProvidedByUsedInInvestingActivitiesAbstract" xlink:label="us-gaap_NetCashProvidedByUsedInInvestingActivitiesAbstract" />
      <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_NetCashProvidedByUsedInInvestingActivitiesAbstract" xlink:to="us-gaap_NetCashProvidedByUsedInInvestingActivitiesAbstract_lbl" xlink:type="arc" />
      <link:label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_NetCashProvidedByUsedInInvestingActivitiesAbstract_lbl" xml:lang="en-US">Cash flows from investing activities:</link:label>
      <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_PaymentsToAcquireAvailableForSaleSecurities" xlink:label="us-gaap_PaymentsToAcquireAvailableForSaleSecurities" />
      <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_PaymentsToAcquireAvailableForSaleSecurities" xlink:to="us-gaap_PaymentsToAcquireAvailableForSaleSecurities_lbl" xlink:type="arc" />
      <link:label xlink:type="resource" xlink:role="http://www.xbrl.org/2009/role/negatedLabel" xlink:label="us-gaap_PaymentsToAcquireAvailableForSaleSecurities_lbl" xml:lang="en-US">Purchases of investment securities</link:label>
      <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ProceedsFromSaleAndMaturityOfAvailableForSaleSecurities" xlink:label="us-gaap_ProceedsFromSaleAndMaturityOfAvailableForSaleSecurities" />
      <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_ProceedsFromSaleAndMaturityOfAvailableForSaleSecurities" xlink:to="us-gaap_ProceedsFromSaleAndMaturityOfAvailableForSaleSecurities_lbl" xlink:type="arc" />
      <link:label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_ProceedsFromSaleAndMaturityOfAvailableForSaleSecurities_lbl" xml:lang="en-US">Proceeds from sale and maturity of investment securities</link:label>
      <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_PaymentsToAcquirePropertyPlantAndEquipment" xlink:label="us-gaap_PaymentsToAcquirePropertyPlantAndEquipment" />
      <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_PaymentsToAcquirePropertyPlantAndEquipment" xlink:to="us-gaap_PaymentsToAcquirePropertyPlantAndEquipment_lbl" xlink:type="arc" />
      <link:label xlink:type="resource" xlink:role="http://www.xbrl.org/2009/role/negatedLabel" xlink:label="us-gaap_PaymentsToAcquirePropertyPlantAndEquipment_lbl" xml:lang="en-US">Purchases of property and equipment</link:label>
      <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_NetCashProvidedByUsedInInvestingActivities" xlink:label="us-gaap_NetCashProvidedByUsedInInvestingActivities" />
      <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_NetCashProvidedByUsedInInvestingActivities" xlink:to="us-gaap_NetCashProvidedByUsedInInvestingActivities_lbl" xlink:type="arc" />
      <link:label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/totalLabel" xlink:label="us-gaap_NetCashProvidedByUsedInInvestingActivities_lbl" xml:lang="en-US">Net cash provided by (used in) investing activities</link:label>
      <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_NetCashProvidedByUsedInFinancingActivitiesAbstract" xlink:label="us-gaap_NetCashProvidedByUsedInFinancingActivitiesAbstract" />
      <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_NetCashProvidedByUsedInFinancingActivitiesAbstract" xlink:to="us-gaap_NetCashProvidedByUsedInFinancingActivitiesAbstract_lbl" xlink:type="arc" />
      <link:label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_NetCashProvidedByUsedInFinancingActivitiesAbstract_lbl" xml:lang="en-US">Cash flows from financing activities:</link:label>
      <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ProceedsFromIssuanceOfCommonStock" xlink:label="us-gaap_ProceedsFromIssuanceOfCommonStock" />
      <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_ProceedsFromIssuanceOfCommonStock" xlink:to="us-gaap_ProceedsFromIssuanceOfCommonStock_lbl" xlink:type="arc" />
      <link:label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_ProceedsFromIssuanceOfCommonStock_lbl" xml:lang="en-US">Proceeds from sale of common stock equity, net of issuance costs</link:label>
      <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ProceedsFromStockOptionsExercised" xlink:label="us-gaap_ProceedsFromStockOptionsExercised" />
      <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_ProceedsFromStockOptionsExercised" xlink:to="us-gaap_ProceedsFromStockOptionsExercised_lbl" xlink:type="arc" />
      <link:label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_ProceedsFromStockOptionsExercised_lbl" xml:lang="en-US">Proceeds from issuance of common stock upon conversion of stock options</link:label>
      <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ProceedsFromLoans" xlink:label="us-gaap_ProceedsFromLoans" />
      <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_ProceedsFromLoans" xlink:to="us-gaap_ProceedsFromLoans_lbl" xlink:type="arc" />
      <link:label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_ProceedsFromLoans_lbl" xml:lang="en-US">Proceeds from Payroll Protection Program (PPP) loans</link:label>
      <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_PaymentsForLoans" xlink:label="us-gaap_PaymentsForLoans" />
      <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_PaymentsForLoans" xlink:to="us-gaap_PaymentsForLoans_lbl" xlink:type="arc" />
      <link:label xlink:type="resource" xlink:role="http://www.xbrl.org/2009/role/negatedLabel" xlink:label="us-gaap_PaymentsForLoans_lbl" xml:lang="en-US">Repayments on Payroll Protection Program (PPP) loans</link:label>
      <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_NetCashProvidedByUsedInFinancingActivities" xlink:label="us-gaap_NetCashProvidedByUsedInFinancingActivities" />
      <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_NetCashProvidedByUsedInFinancingActivities" xlink:to="us-gaap_NetCashProvidedByUsedInFinancingActivities_lbl" xlink:type="arc" />
      <link:label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/totalLabel" xlink:label="us-gaap_NetCashProvidedByUsedInFinancingActivities_lbl" xml:lang="en-US">Net cash provided by financing activities</link:label>
      <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalentsPeriodIncreaseDecreaseIncludingExchangeRateEffect" xlink:label="us-gaap_CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalentsPeriodIncreaseDecreaseIncludingExchangeRateEffect" />
      <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalentsPeriodIncreaseDecreaseIncludingExchangeRateEffect" xlink:to="us-gaap_CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalentsPeriodIncreaseDecreaseIncludingExchangeRateEffect_lbl" xlink:type="arc" />
      <link:label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/totalLabel" xlink:label="us-gaap_CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalentsPeriodIncreaseDecreaseIncludingExchangeRateEffect_lbl" xml:lang="en-US">Increase (decrease) in cash and cash equivalents</link:label>
      <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalentsIncludingDisposalGroupAndDiscontinuedOperations" xlink:label="us-gaap_CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalentsIncludingDisposalGroupAndDiscontinuedOperations" />
      <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalentsIncludingDisposalGroupAndDiscontinuedOperations" xlink:to="us-gaap_CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalentsIncludingDisposalGroupAndDiscontinuedOperations_lbl" xlink:type="arc" />
      <link:label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/periodStartLabel" xlink:label="us-gaap_CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalentsIncludingDisposalGroupAndDiscontinuedOperations_lbl" xml:lang="en-US">Cash and cash equivalents at beginning of period</link:label>
      <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalentsIncludingDisposalGroupAndDiscontinuedOperations" xlink:to="us-gaap_CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalentsIncludingDisposalGroupAndDiscontinuedOperations_2_lbl" xlink:type="arc" />
      <link:label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/periodEndLabel" xlink:label="us-gaap_CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalentsIncludingDisposalGroupAndDiscontinuedOperations_2_lbl" xml:lang="en-US">Cash and cash equivalents at end of period</link:label>
      <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_SupplementalCashFlowInformationAbstract" xlink:label="us-gaap_SupplementalCashFlowInformationAbstract" />
      <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_SupplementalCashFlowInformationAbstract" xlink:to="us-gaap_SupplementalCashFlowInformationAbstract_lbl" xlink:type="arc" />
      <link:label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_SupplementalCashFlowInformationAbstract_lbl" xml:lang="en-US">Supplemental disclosures of cash flow information:</link:label>
      <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_InterestPaidNet" xlink:label="us-gaap_InterestPaidNet" />
      <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_InterestPaidNet" xlink:to="us-gaap_InterestPaidNet_lbl" xlink:type="arc" />
      <link:label xlink:type="resource" xlink:role="http://www.xbrl.org/2009/role/negatedLabel" xlink:label="us-gaap_InterestPaidNet_lbl" xml:lang="en-US">Interest paid</link:label>
      <link:loc xlink:type="locator" xlink:href="clsn-20200630.xsd#CLSN_CashPaidForAmountsIncludedInMeasurementOfLeaseLiabilitiesAbstract" xlink:label="CLSN_CashPaidForAmountsIncludedInMeasurementOfLeaseLiabilitiesAbstract" />
      <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="CLSN_CashPaidForAmountsIncludedInMeasurementOfLeaseLiabilitiesAbstract" xlink:to="CLSN_CashPaidForAmountsIncludedInMeasurementOfLeaseLiabilitiesAbstract_lbl" xlink:type="arc" />
      <link:label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="CLSN_CashPaidForAmountsIncludedInMeasurementOfLeaseLiabilitiesAbstract_lbl" xml:lang="en-US">Cash paid for amounts included in measurement of lease liabilities:</link:label>
      <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_OperatingLeasePayments" xlink:label="us-gaap_OperatingLeasePayments" />
      <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_OperatingLeasePayments" xlink:to="us-gaap_OperatingLeasePayments_lbl" xlink:type="arc" />
      <link:label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_OperatingLeasePayments_lbl" xml:lang="en-US">Operating cash flows from lease payments</link:label>
      <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_CashFlowNoncashInvestingAndFinancingActivitiesDisclosureAbstract" xlink:label="us-gaap_CashFlowNoncashInvestingAndFinancingActivitiesDisclosureAbstract" />
      <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_CashFlowNoncashInvestingAndFinancingActivitiesDisclosureAbstract" xlink:to="us-gaap_CashFlowNoncashInvestingAndFinancingActivitiesDisclosureAbstract_lbl" xlink:type="arc" />
      <link:label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_CashFlowNoncashInvestingAndFinancingActivitiesDisclosureAbstract_lbl" xml:lang="en-US">Non-cash financing and investing activities</link:label>
      <link:loc xlink:type="locator" xlink:href="clsn-20200630.xsd#CLSN_FairValueOfWarrantsIssuedInConnectionWithAmendmentToModifyRelatedEarnoutMilestonePayments" xlink:label="CLSN_FairValueOfWarrantsIssuedInConnectionWithAmendmentToModifyRelatedEarnoutMilestonePayments" />
      <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="CLSN_FairValueOfWarrantsIssuedInConnectionWithAmendmentToModifyRelatedEarnoutMilestonePayments" xlink:to="CLSN_FairValueOfWarrantsIssuedInConnectionWithAmendmentToModifyRelatedEarnoutMilestonePayments_lbl" xlink:type="arc" />
      <link:label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="CLSN_FairValueOfWarrantsIssuedInConnectionWithAmendmentToModifyRelatedEarnoutMilestonePayments_lbl" xml:lang="en-US">Fair value of warrants issued in connection with amendment to modify the GEN-1 earn-out milestone payments</link:label>
      <link:loc xlink:type="locator" xlink:href="clsn-20200630.xsd#CLSN_RightOfUseAssetsObtainedInExchangeForLeaseLiabilitiesAbstract" xlink:label="CLSN_RightOfUseAssetsObtainedInExchangeForLeaseLiabilitiesAbstract" />
      <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="CLSN_RightOfUseAssetsObtainedInExchangeForLeaseLiabilitiesAbstract" xlink:to="CLSN_RightOfUseAssetsObtainedInExchangeForLeaseLiabilitiesAbstract_lbl" xlink:type="arc" />
      <link:label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="CLSN_RightOfUseAssetsObtainedInExchangeForLeaseLiabilitiesAbstract_lbl" xml:lang="en-US">Right of use assets obtained in exchange for lease liabilities</link:label>
      <link:loc xlink:type="locator" xlink:href="clsn-20200630.xsd#CLSN_RightOfUseAssetsObtainedInExchangeForLease" xlink:label="CLSN_RightOfUseAssetsObtainedInExchangeForLease" />
      <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="CLSN_RightOfUseAssetsObtainedInExchangeForLease" xlink:to="CLSN_RightOfUseAssetsObtainedInExchangeForLease_lbl" xlink:type="arc" />
      <link:label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="CLSN_RightOfUseAssetsObtainedInExchangeForLease_lbl" xml:lang="en-US">Right of use assets</link:label>
      <link:loc xlink:type="locator" xlink:href="clsn-20200630.xsd#CLSN_StockIssuedInLieuOfCashBonusPayments" xlink:label="CLSN_StockIssuedInLieuOfCashBonusPayments" />
      <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="CLSN_StockIssuedInLieuOfCashBonusPayments" xlink:to="CLSN_StockIssuedInLieuOfCashBonusPayments_lbl" xlink:type="arc" />
      <link:label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="CLSN_StockIssuedInLieuOfCashBonusPayments_lbl" xml:lang="en-US">Stock issued in lieu of cash bonus payments</link:label>
      <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_OtherComprehensiveIncomeLossNetOfTaxPortionAttributableToParent" xlink:label="us-gaap_OtherComprehensiveIncomeLossNetOfTaxPortionAttributableToParent" />
      <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_OtherComprehensiveIncomeLossNetOfTaxPortionAttributableToParent" xlink:to="us-gaap_OtherComprehensiveIncomeLossNetOfTaxPortionAttributableToParent_lbl" xlink:type="arc" />
      <link:label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_OtherComprehensiveIncomeLossNetOfTaxPortionAttributableToParent_lbl" xml:lang="en-US">Realized and unrealized (gains) losses, net, on investment securities</link:label>
      <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_StatementTable" xlink:label="us-gaap_StatementTable" />
      <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_StatementTable" xlink:to="us-gaap_StatementTable_lbl" xlink:type="arc" />
      <link:label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_StatementTable_lbl" xml:lang="en-US">Statement [Table]</link:label>
      <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_StatementLineItems" xlink:label="us-gaap_StatementLineItems" />
      <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_StatementLineItems" xlink:to="us-gaap_StatementLineItems_lbl" xlink:type="arc" />
      <link:label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_StatementLineItems_lbl" xml:lang="en-US">Statement [Line Items]</link:label>
      <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_StockholdersEquity" xlink:to="us-gaap_StockholdersEquity_2_lbl" xlink:type="arc" />
      <link:label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/periodStartLabel" xlink:label="us-gaap_StockholdersEquity_2_lbl" xml:lang="en-US">Balance</link:label>
      <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_SharesOutstanding" xlink:label="us-gaap_SharesOutstanding" />
      <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_SharesOutstanding" xlink:to="us-gaap_SharesOutstanding_lbl" xlink:type="arc" />
      <link:label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/periodStartLabel" xlink:label="us-gaap_SharesOutstanding_lbl" xml:lang="en-US">Balance, shares</link:label>
      <link:loc xlink:type="locator" xlink:href="clsn-20200630.xsd#CLSN_SaleOfEquityThroughEquityFinancingFacilities" xlink:label="CLSN_SaleOfEquityThroughEquityFinancingFacilities" />
      <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="CLSN_SaleOfEquityThroughEquityFinancingFacilities" xlink:to="CLSN_SaleOfEquityThroughEquityFinancingFacilities_lbl" xlink:type="arc" />
      <link:label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="CLSN_SaleOfEquityThroughEquityFinancingFacilities_lbl" xml:lang="en-US">Sale of equity through financing facilities</link:label>
      <link:loc xlink:type="locator" xlink:href="clsn-20200630.xsd#CLSN_SaleOfEquityThroughEquityFinancingFacilitiesShares" xlink:label="CLSN_SaleOfEquityThroughEquityFinancingFacilitiesShares" />
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      <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_RetainedEarningsAccumulatedDeficit" xlink:to="us-gaap_RetainedEarningsAccumulatedDeficit_2_lbl" xlink:type="arc" />
      <link:label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/verboseLabel" xlink:label="us-gaap_RetainedEarningsAccumulatedDeficit_2_lbl" xml:lang="en-US">Cumulated net losses</link:label>
      <link:loc xlink:type="locator" xlink:href="clsn-20200630.xsd#CLSN_CashInvestmentSecuritiesAndInterestReceivable" xlink:label="CLSN_CashInvestmentSecuritiesAndInterestReceivable" />
      <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="CLSN_CashInvestmentSecuritiesAndInterestReceivable" xlink:to="CLSN_CashInvestmentSecuritiesAndInterestReceivable_lbl" xlink:type="arc" />
      <link:label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="CLSN_CashInvestmentSecuritiesAndInterestReceivable_lbl" xml:lang="en-US">Cash, investment securities and interest receivable</link:label>
      <link:loc xlink:type="locator" xlink:href="clsn-20200630.xsd#CLSN_TaxBenefitsOfEarningsBeforeDepreciationAndAmortization" xlink:label="CLSN_TaxBenefitsOfEarningsBeforeDepreciationAndAmortization" />
      <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="CLSN_TaxBenefitsOfEarningsBeforeDepreciationAndAmortization" xlink:to="CLSN_TaxBenefitsOfEarningsBeforeDepreciationAndAmortization_lbl" xlink:type="arc" />
      <link:label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="CLSN_TaxBenefitsOfEarningsBeforeDepreciationAndAmortization_lbl" xml:lang="en-US">Tax benefits of EDA</link:label>
      <link:loc xlink:type="locator" xlink:href="clsn-20200630.xsd#CLSN_NetProceedsFromSaleOfNetOperatingLosses" xlink:label="CLSN_NetProceedsFromSaleOfNetOperatingLosses" />
      <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="CLSN_NetProceedsFromSaleOfNetOperatingLosses" xlink:to="CLSN_NetProceedsFromSaleOfNetOperatingLosses_lbl" xlink:type="arc" />
      <link:label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="CLSN_NetProceedsFromSaleOfNetOperatingLosses_lbl" xml:lang="en-US">Net proceeds from sale of net operating losses</link:label>
      <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ProceedsFromContributedCapital" xlink:label="us-gaap_ProceedsFromContributedCapital" />
      <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_ProceedsFromContributedCapital" xlink:to="us-gaap_ProceedsFromContributedCapital_lbl" xlink:type="arc" />
      <link:label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_ProceedsFromContributedCapital_lbl" xml:lang="en-US">Proceeds from new capital</link:label>
      <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_DebtInstrumentInterestRateStatedPercentage" xlink:label="us-gaap_DebtInstrumentInterestRateStatedPercentage" />
      <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_DebtInstrumentInterestRateStatedPercentage" xlink:to="us-gaap_DebtInstrumentInterestRateStatedPercentage_lbl" xlink:type="arc" />
      <link:label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_DebtInstrumentInterestRateStatedPercentage_lbl" xml:lang="en-US">Debt instrument, interest rate</link:label>
      <link:loc xlink:type="locator" xlink:href="clsn-20200630.xsd#CLSN_NumberOfSharesOfCommonStockIssuableUponExerciseOfWarrantsAndEquityAwards" xlink:label="CLSN_NumberOfSharesOfCommonStockIssuableUponExerciseOfWarrantsAndEquityAwards" />
      <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="CLSN_NumberOfSharesOfCommonStockIssuableUponExerciseOfWarrantsAndEquityAwards" xlink:to="CLSN_NumberOfSharesOfCommonStockIssuableUponExerciseOfWarrantsAndEquityAwards_lbl" xlink:type="arc" />
      <link:label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="CLSN_NumberOfSharesOfCommonStockIssuableUponExerciseOfWarrantsAndEquityAwards_lbl" xml:lang="en-US">Number of shares of common stock issuable upon exercise of warrants and equity awards</link:label>
      <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ClassOfWarrantOrRightExercisePriceOfWarrantsOrRights1" xlink:label="us-gaap_ClassOfWarrantOrRightExercisePriceOfWarrantsOrRights1" />
      <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_ClassOfWarrantOrRightExercisePriceOfWarrantsOrRights1" xlink:to="us-gaap_ClassOfWarrantOrRightExercisePriceOfWarrantsOrRights1_lbl" xlink:type="arc" />
      <link:label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_ClassOfWarrantOrRightExercisePriceOfWarrantsOrRights1_lbl" xml:lang="en-US">Warrants exercise price</link:label>
      <link:loc xlink:type="locator" xlink:href="clsn-20200630.xsd#CLSN_NumberOfSharesOfCommonStockIssuedInCalculationBasicLossPerShare" xlink:label="CLSN_NumberOfSharesOfCommonStockIssuedInCalculationBasicLossPerShare" />
      <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="CLSN_NumberOfSharesOfCommonStockIssuedInCalculationBasicLossPerShare" xlink:to="CLSN_NumberOfSharesOfCommonStockIssuedInCalculationBasicLossPerShare_lbl" xlink:type="arc" />
      <link:label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="CLSN_NumberOfSharesOfCommonStockIssuedInCalculationBasicLossPerShare_lbl" xml:lang="en-US">Number of shares of common stock issued in calculation basic loss per share</link:label>
      <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_AvailableForSaleSecuritiesDebtSecuritiesCurrent" xlink:to="us-gaap_AvailableForSaleSecuritiesDebtSecuritiesCurrent_2_lbl" xlink:type="arc" />
      <link:label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/verboseLabel" xlink:label="us-gaap_AvailableForSaleSecuritiesDebtSecuritiesCurrent_2_lbl" xml:lang="en-US">Short-term investments - Fair Value</link:label>
      <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ShortTermInvestments" xlink:label="us-gaap_ShortTermInvestments" />
      <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_ShortTermInvestments" xlink:to="us-gaap_ShortTermInvestments_lbl" xlink:type="arc" />
      <link:label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_ShortTermInvestments_lbl" xml:lang="en-US">Short-term investments - Cost</link:label>
      <link:loc xlink:type="locator" xlink:href="clsn-20200630.xsd#CLSN_DebtSecuritiesAvailableforsaleMaturityAllocatedAndSingleMaturityDateRollingWithinThreeMonthsAmortizedCost" xlink:label="CLSN_DebtSecuritiesAvailableforsaleMaturityAllocatedAndSingleMaturityDateRollingWithinThreeMonthsAmortizedCost" />
      <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="CLSN_DebtSecuritiesAvailableforsaleMaturityAllocatedAndSingleMaturityDateRollingWithinThreeMonthsAmortizedCost" xlink:to="CLSN_DebtSecuritiesAvailableforsaleMaturityAllocatedAndSingleMaturityDateRollingWithinThreeMonthsAmortizedCost_lbl" xlink:type="arc" />
      <link:label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="CLSN_DebtSecuritiesAvailableforsaleMaturityAllocatedAndSingleMaturityDateRollingWithinThreeMonthsAmortizedCost_lbl" xml:lang="en-US">Short-term investment maturities - Within 3 months, cost</link:label>
      <link:loc xlink:type="locator" xlink:href="clsn-20200630.xsd#CLSN_AvailableForSaleDebtSecuritiesAmortizedCostBasisCurrent" xlink:label="CLSN_AvailableForSaleDebtSecuritiesAmortizedCostBasisCurrent" />
      <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="CLSN_AvailableForSaleDebtSecuritiesAmortizedCostBasisCurrent" xlink:to="CLSN_AvailableForSaleDebtSecuritiesAmortizedCostBasisCurrent_lbl" xlink:type="arc" />
      <link:label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/totalLabel" xlink:label="CLSN_AvailableForSaleDebtSecuritiesAmortizedCostBasisCurrent_lbl" xml:lang="en-US">Total, cost</link:label>
      <link:loc xlink:type="locator" xlink:href="clsn-20200630.xsd#CLSN_DebtSecuritiesAvailableforsaleMaturityAllocatedAndSingleMaturityDateRollingWithinThreeMonthsFairValue" xlink:label="CLSN_DebtSecuritiesAvailableforsaleMaturityAllocatedAndSingleMaturityDateRollingWithinThreeMonthsFairValue" />
      <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="CLSN_DebtSecuritiesAvailableforsaleMaturityAllocatedAndSingleMaturityDateRollingWithinThreeMonthsFairValue" xlink:to="CLSN_DebtSecuritiesAvailableforsaleMaturityAllocatedAndSingleMaturityDateRollingWithinThreeMonthsFairValue_lbl" xlink:type="arc" />
      <link:label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="CLSN_DebtSecuritiesAvailableforsaleMaturityAllocatedAndSingleMaturityDateRollingWithinThreeMonthsFairValue_lbl" xml:lang="en-US">Short-term investment maturities - Within 3 months, fair value</link:label>
      <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_AvailableForSaleSecuritiesDebtMaturitiesSingleMaturityDate" xlink:label="us-gaap_AvailableForSaleSecuritiesDebtMaturitiesSingleMaturityDate" />
      <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_AvailableForSaleSecuritiesDebtMaturitiesSingleMaturityDate" xlink:to="us-gaap_AvailableForSaleSecuritiesDebtMaturitiesSingleMaturityDate_lbl" xlink:type="arc" />
      <link:label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/totalLabel" xlink:label="us-gaap_AvailableForSaleSecuritiesDebtMaturitiesSingleMaturityDate_lbl" xml:lang="en-US">Total, fair value</link:label>
      <link:loc xlink:type="locator" xlink:href="clsn-20200630.xsd#CLSN_DebtSecuritiesAvailableforsaleContinuousUnrealizedGainPositionLessThan12Months" xlink:label="CLSN_DebtSecuritiesAvailableforsaleContinuousUnrealizedGainPositionLessThan12Months" />
      <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="CLSN_DebtSecuritiesAvailableforsaleContinuousUnrealizedGainPositionLessThan12Months" xlink:to="CLSN_DebtSecuritiesAvailableforsaleContinuousUnrealizedGainPositionLessThan12Months_lbl" xlink:type="arc" />
      <link:label xlink:type="resource" xlink:role="http://www.xbrl.org/2009/role/negatedLabel" xlink:label="CLSN_DebtSecuritiesAvailableforsaleContinuousUnrealizedGainPositionLessThan12Months_lbl" xml:lang="en-US">Investments in debt securities with unrealized Gains, Less than 12 months , Fair Value</link:label>
      <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_AvailableForSaleSecuritiesDebtSecuritiesCurrent" xlink:to="us-gaap_AvailableForSaleSecuritiesDebtSecuritiesCurrent_3_lbl" xlink:type="arc" />
      <link:label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/totalLabel" xlink:label="us-gaap_AvailableForSaleSecuritiesDebtSecuritiesCurrent_3_lbl" xml:lang="en-US">Investment securities - available for sale, Fair Value</link:label>
      <link:loc xlink:type="locator" xlink:href="clsn-20200630.xsd#CLSN_DebtSecuritiesAvailableforsaleContinuousUnrealizedGainPositionLessThan12MonthsAccumulatedGain" xlink:label="CLSN_DebtSecuritiesAvailableforsaleContinuousUnrealizedGainPositionLessThan12MonthsAccumulatedGain" />
      <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="CLSN_DebtSecuritiesAvailableforsaleContinuousUnrealizedGainPositionLessThan12MonthsAccumulatedGain" xlink:to="CLSN_DebtSecuritiesAvailableforsaleContinuousUnrealizedGainPositionLessThan12MonthsAccumulatedGain_lbl" xlink:type="arc" />
      <link:label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="CLSN_DebtSecuritiesAvailableforsaleContinuousUnrealizedGainPositionLessThan12MonthsAccumulatedGain_lbl" xml:lang="en-US">Investments in debt securities with unrealized Gains, Less than 12 months, Unrealized Holding Gains</link:label>
      <link:loc xlink:type="locator" xlink:href="clsn-20200630.xsd#CLSN_AvailableforsaleSecuritiesDebtSecuritiesCurrentAccumulatedUnrealizedGainLoss" xlink:label="CLSN_AvailableforsaleSecuritiesDebtSecuritiesCurrentAccumulatedUnrealizedGainLoss" />
      <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="CLSN_AvailableforsaleSecuritiesDebtSecuritiesCurrentAccumulatedUnrealizedGainLoss" xlink:to="CLSN_AvailableforsaleSecuritiesDebtSecuritiesCurrentAccumulatedUnrealizedGainLoss_lbl" xlink:type="arc" />
      <link:label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/totalLabel" xlink:label="CLSN_AvailableforsaleSecuritiesDebtSecuritiesCurrentAccumulatedUnrealizedGainLoss_lbl" xml:lang="en-US">Unrealized Holding Gains</link:label>
      <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_InvestmentIncomeInterestAndDividend" xlink:label="us-gaap_InvestmentIncomeInterestAndDividend" />
      <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_InvestmentIncomeInterestAndDividend" xlink:to="us-gaap_InvestmentIncomeInterestAndDividend_lbl" xlink:type="arc" />
      <link:label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_InvestmentIncomeInterestAndDividend_lbl" xml:lang="en-US">Interest and dividends accrued and paid</link:label>
      <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_AvailableForSaleSecuritiesGrossRealizedGainLossNet" xlink:label="us-gaap_AvailableForSaleSecuritiesGrossRealizedGainLossNet" />
      <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_AvailableForSaleSecuritiesGrossRealizedGainLossNet" xlink:to="us-gaap_AvailableForSaleSecuritiesGrossRealizedGainLossNet_lbl" xlink:type="arc" />
      <link:label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_AvailableForSaleSecuritiesGrossRealizedGainLossNet_lbl" xml:lang="en-US">Realized gains</link:label>
      <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_InvestmentIncomeNonoperating" xlink:to="us-gaap_InvestmentIncomeNonoperating_2_lbl" xlink:type="arc" />
      <link:label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/totalLabel" xlink:label="us-gaap_InvestmentIncomeNonoperating_2_lbl" xml:lang="en-US">Investment income, net</link:label>
      <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_AvailableForSaleSecuritiesDebtSecuritiesCurrent" xlink:to="us-gaap_AvailableForSaleSecuritiesDebtSecuritiesCurrent_4_lbl" xlink:type="arc" />
      <link:label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:label="us-gaap_AvailableForSaleSecuritiesDebtSecuritiesCurrent_4_lbl" xml:lang="en-US">Investment securities, available for sale</link:label>
      <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_IndefinitelivedIntangibleAssetsAcquired" xlink:label="us-gaap_IndefinitelivedIntangibleAssetsAcquired" />
      <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_IndefinitelivedIntangibleAssetsAcquired" xlink:to="us-gaap_IndefinitelivedIntangibleAssetsAcquired_lbl" xlink:type="arc" />
      <link:label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_IndefinitelivedIntangibleAssetsAcquired_lbl" xml:lang="en-US">Indefinite lived intangible assets</link:label>
      <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_AssetImpairmentCharges" xlink:label="us-gaap_AssetImpairmentCharges" />
      <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_AssetImpairmentCharges" xlink:to="us-gaap_AssetImpairmentCharges_lbl" xlink:type="arc" />
      <link:label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_AssetImpairmentCharges_lbl" xml:lang="en-US">Asset impairment charges, total</link:label>
      <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_FinitelivedIntangibleAssetsAcquired1" xlink:label="us-gaap_FinitelivedIntangibleAssetsAcquired1" />
      <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_FinitelivedIntangibleAssetsAcquired1" xlink:to="us-gaap_FinitelivedIntangibleAssetsAcquired1_lbl" xlink:type="arc" />
      <link:label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_FinitelivedIntangibleAssetsAcquired1_lbl" xml:lang="en-US">Finite-lived intangible assets acquired</link:label>
      <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_FiniteLivedIntangibleAssetUsefulLife" xlink:label="us-gaap_FiniteLivedIntangibleAssetUsefulLife" />
      <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_FiniteLivedIntangibleAssetUsefulLife" xlink:to="us-gaap_FiniteLivedIntangibleAssetUsefulLife_lbl" xlink:type="arc" />
      <link:label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_FiniteLivedIntangibleAssetUsefulLife_lbl" xml:lang="en-US">Finite-lived intangible asset, useful life</link:label>
      <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_AdjustmentForAmortization" xlink:label="us-gaap_AdjustmentForAmortization" />
      <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_AdjustmentForAmortization" xlink:to="us-gaap_AdjustmentForAmortization_lbl" xlink:type="arc" />
      <link:label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_AdjustmentForAmortization_lbl" xml:lang="en-US">Amortization expense</link:label>
      <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_FiniteLivedIntangibleAssetsNet" xlink:to="us-gaap_FiniteLivedIntangibleAssetsNet_2_lbl" xlink:type="arc" />
      <link:label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/verboseLabel" xlink:label="us-gaap_FiniteLivedIntangibleAssetsNet_2_lbl" xml:lang="en-US">Finite-lived intangible assets, net</link:label>
      <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_FiniteLivedIntangibleAssetsAccumulatedAmortization" xlink:label="us-gaap_FiniteLivedIntangibleAssetsAccumulatedAmortization" />
      <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_FiniteLivedIntangibleAssetsAccumulatedAmortization" xlink:to="us-gaap_FiniteLivedIntangibleAssetsAccumulatedAmortization_lbl" xlink:type="arc" />
      <link:label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_FiniteLivedIntangibleAssetsAccumulatedAmortization_lbl" xml:lang="en-US">Finite-lived intangible assets, accumulated amortization</link:label>
      <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_GoodwillAcquiredDuringPeriod" xlink:label="us-gaap_GoodwillAcquiredDuringPeriod" />
      <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_GoodwillAcquiredDuringPeriod" xlink:to="us-gaap_GoodwillAcquiredDuringPeriod_lbl" xlink:type="arc" />
      <link:label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_GoodwillAcquiredDuringPeriod_lbl" xml:lang="en-US">Goodwill, acquisition</link:label>
      <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_FiniteLivedIntangibleAssetsAmortizationExpenseNextTwelveMonths" xlink:label="us-gaap_FiniteLivedIntangibleAssetsAmortizationExpenseNextTwelveMonths" />
      <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_FiniteLivedIntangibleAssetsAmortizationExpenseNextTwelveMonths" xlink:to="us-gaap_FiniteLivedIntangibleAssetsAmortizationExpenseNextTwelveMonths_lbl" xlink:type="arc" />
      <link:label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_FiniteLivedIntangibleAssetsAmortizationExpenseNextTwelveMonths_lbl" xml:lang="en-US">2021</link:label>
      <link:loc xlink:type="locator" xlink:href="clsn-20200630.xsd#CLSN_FiniteLivedIntangibleAssetsAmortizationExpenseYearTwoAndAfter" xlink:label="CLSN_FiniteLivedIntangibleAssetsAmortizationExpenseYearTwoAndAfter" />
      <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="CLSN_FiniteLivedIntangibleAssetsAmortizationExpenseYearTwoAndAfter" xlink:to="CLSN_FiniteLivedIntangibleAssetsAmortizationExpenseYearTwoAndAfter_lbl" xlink:type="arc" />
      <link:label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="CLSN_FiniteLivedIntangibleAssetsAmortizationExpenseYearTwoAndAfter_lbl" xml:lang="en-US">2022 and thereafter</link:label>
      <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_FiniteLivedIntangibleAssetsNet" xlink:to="us-gaap_FiniteLivedIntangibleAssetsNet_3_lbl" xlink:type="arc" />
      <link:label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/totalLabel" xlink:label="us-gaap_FiniteLivedIntangibleAssetsNet_3_lbl" xml:lang="en-US">Total</link:label>
      <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_FiniteLivedIntangibleAssetsNet" xlink:to="us-gaap_FiniteLivedIntangibleAssetsNet_4_lbl" xlink:type="arc" />
      <link:label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/periodStartLabel" xlink:label="us-gaap_FiniteLivedIntangibleAssetsNet_4_lbl" xml:lang="en-US">Intangible assets, beginning balance</link:label>
      <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_AmortizationOfIntangibleAssets" xlink:label="us-gaap_AmortizationOfIntangibleAssets" />
      <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_AmortizationOfIntangibleAssets" xlink:to="us-gaap_AmortizationOfIntangibleAssets_lbl" xlink:type="arc" />
      <link:label xlink:type="resource" xlink:role="http://www.xbrl.org/2009/role/negatedLabel" xlink:label="us-gaap_AmortizationOfIntangibleAssets_lbl" xml:lang="en-US">Amortization</link:label>
      <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_FiniteLivedIntangibleAssetsNet" xlink:to="us-gaap_FiniteLivedIntangibleAssetsNet_5_lbl" xlink:type="arc" />
      <link:label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/periodEndLabel" xlink:label="us-gaap_FiniteLivedIntangibleAssetsNet_5_lbl" xml:lang="en-US">Intangible assets, ending balance</link:label>
      <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ContractualObligation" xlink:label="us-gaap_ContractualObligation" />
      <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_ContractualObligation" xlink:to="us-gaap_ContractualObligation_lbl" xlink:type="arc" />
      <link:label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_ContractualObligation_lbl" xml:lang="en-US">Amounts due to contract research organizations and other contractual agreements</link:label>
      <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_EmployeeRelatedLiabilitiesCurrent" xlink:label="us-gaap_EmployeeRelatedLiabilitiesCurrent" />
      <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_EmployeeRelatedLiabilitiesCurrent" xlink:to="us-gaap_EmployeeRelatedLiabilitiesCurrent_lbl" xlink:type="arc" />
      <link:label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_EmployeeRelatedLiabilitiesCurrent_lbl" xml:lang="en-US">Accrued payroll and related benefits</link:label>
      <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_AccruedProfessionalFeesCurrent" xlink:label="us-gaap_AccruedProfessionalFeesCurrent" />
      <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_AccruedProfessionalFeesCurrent" xlink:to="us-gaap_AccruedProfessionalFeesCurrent_lbl" xlink:type="arc" />
      <link:label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_AccruedProfessionalFeesCurrent_lbl" xml:lang="en-US">Accrued professional fees</link:label>
      <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_OtherAccruedLiabilitiesCurrent" xlink:label="us-gaap_OtherAccruedLiabilitiesCurrent" />
      <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_OtherAccruedLiabilitiesCurrent" xlink:to="us-gaap_OtherAccruedLiabilitiesCurrent_lbl" xlink:type="arc" />
      <link:label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_OtherAccruedLiabilitiesCurrent_lbl" xml:lang="en-US">Other</link:label>
      <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_AccruedLiabilitiesCurrent" xlink:to="us-gaap_AccruedLiabilitiesCurrent_2_lbl" xlink:type="arc" />
      <link:label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/totalLabel" xlink:label="us-gaap_AccruedLiabilitiesCurrent_2_lbl" xml:lang="en-US">Total</link:label>
      <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="srt_RangeAxis" xlink:to="srt_RangeAxis_2_lbl" xlink:type="arc" />
      <link:label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/verboseLabel" xlink:label="srt_RangeAxis_2_lbl" xml:lang="en-US">Statistical Measurement [Axis]</link:label>
      <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ProceedsFromLinesOfCredit" xlink:label="us-gaap_ProceedsFromLinesOfCredit" />
      <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_ProceedsFromLinesOfCredit" xlink:to="us-gaap_ProceedsFromLinesOfCredit_lbl" xlink:type="arc" />
      <link:label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_ProceedsFromLinesOfCredit_lbl" xml:lang="en-US">Proceeds from lines of credit, total</link:label>
      <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_InterestExpenseDebt" xlink:label="us-gaap_InterestExpenseDebt" />
      <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_InterestExpenseDebt" xlink:to="us-gaap_InterestExpenseDebt_lbl" xlink:type="arc" />
      <link:label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_InterestExpenseDebt_lbl" xml:lang="en-US">Interest expense, debt, total</link:label>
      <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_AmortizationOfFinancingCosts" xlink:label="us-gaap_AmortizationOfFinancingCosts" />
      <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_AmortizationOfFinancingCosts" xlink:to="us-gaap_AmortizationOfFinancingCosts_lbl" xlink:type="arc" />
      <link:label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_AmortizationOfFinancingCosts_lbl" xml:lang="en-US">Amortization of debt issuance costs</link:label>
      <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_ProceedsFromLoans" xlink:to="us-gaap_ProceedsFromLoans_2_lbl" xlink:type="arc" />
      <link:label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/verboseLabel" xlink:label="us-gaap_ProceedsFromLoans_2_lbl" xml:lang="en-US">Proceeds from loan</link:label>
      <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_DebtInstrumentMaturityDate" xlink:label="us-gaap_DebtInstrumentMaturityDate" />
      <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_DebtInstrumentMaturityDate" xlink:to="us-gaap_DebtInstrumentMaturityDate_lbl" xlink:type="arc" />
      <link:label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_DebtInstrumentMaturityDate_lbl" xml:lang="en-US">Loan repayment date</link:label>
      <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_DebtInstrumentCarryingAmount" xlink:label="us-gaap_DebtInstrumentCarryingAmount" />
      <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_DebtInstrumentCarryingAmount" xlink:to="us-gaap_DebtInstrumentCarryingAmount_lbl" xlink:type="arc" />
      <link:label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_DebtInstrumentCarryingAmount_lbl" xml:lang="en-US">Loan amount</link:label>
      <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_DebtInstrumentFaceAmount" xlink:label="us-gaap_DebtInstrumentFaceAmount" />
      <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_DebtInstrumentFaceAmount" xlink:to="us-gaap_DebtInstrumentFaceAmount_lbl" xlink:type="arc" />
      <link:label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_DebtInstrumentFaceAmount_lbl" xml:lang="en-US">Debt instrument face amount</link:label>
      <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_StockIssuedDuringPeriodSharesNewIssues" xlink:label="us-gaap_StockIssuedDuringPeriodSharesNewIssues" />
      <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_StockIssuedDuringPeriodSharesNewIssues" xlink:to="us-gaap_StockIssuedDuringPeriodSharesNewIssues_lbl" xlink:type="arc" />
      <link:label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_StockIssuedDuringPeriodSharesNewIssues_lbl" xml:lang="en-US">Common stock shares issued</link:label>
      <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_ProceedsFromIssuanceOfCommonStock" xlink:to="us-gaap_ProceedsFromIssuanceOfCommonStock_2_lbl" xlink:type="arc" />
      <link:label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/verboseLabel" xlink:label="us-gaap_ProceedsFromIssuanceOfCommonStock_2_lbl" xml:lang="en-US">Net proceeds from issuance of common stock</link:label>
      <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_DebtInstrumentIncreaseAccruedInterest" xlink:label="us-gaap_DebtInstrumentIncreaseAccruedInterest" />
      <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_DebtInstrumentIncreaseAccruedInterest" xlink:to="us-gaap_DebtInstrumentIncreaseAccruedInterest_lbl" xlink:type="arc" />
      <link:label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_DebtInstrumentIncreaseAccruedInterest_lbl" xml:lang="en-US">Interest accrued on loan</link:label>
      <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_LongTermDebtMaturitiesRepaymentsOfPrincipalInNextTwelveMonths" xlink:label="us-gaap_LongTermDebtMaturitiesRepaymentsOfPrincipalInNextTwelveMonths" />
      <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_LongTermDebtMaturitiesRepaymentsOfPrincipalInNextTwelveMonths" xlink:to="us-gaap_LongTermDebtMaturitiesRepaymentsOfPrincipalInNextTwelveMonths_lbl" xlink:type="arc" />
      <link:label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/verboseLabel" xlink:label="us-gaap_LongTermDebtMaturitiesRepaymentsOfPrincipalInNextTwelveMonths_lbl" xml:lang="en-US">2021</link:label>
      <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_LongTermDebtMaturitiesRepaymentsOfPrincipalInYearTwo" xlink:label="us-gaap_LongTermDebtMaturitiesRepaymentsOfPrincipalInYearTwo" />
      <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_LongTermDebtMaturitiesRepaymentsOfPrincipalInYearTwo" xlink:to="us-gaap_LongTermDebtMaturitiesRepaymentsOfPrincipalInYearTwo_lbl" xlink:type="arc" />
      <link:label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_LongTermDebtMaturitiesRepaymentsOfPrincipalInYearTwo_lbl" xml:lang="en-US">2022</link:label>
      <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_LongTermDebtMaturitiesRepaymentsOfPrincipalInYearThree" xlink:label="us-gaap_LongTermDebtMaturitiesRepaymentsOfPrincipalInYearThree" />
      <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_LongTermDebtMaturitiesRepaymentsOfPrincipalInYearThree" xlink:to="us-gaap_LongTermDebtMaturitiesRepaymentsOfPrincipalInYearThree_lbl" xlink:type="arc" />
      <link:label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_LongTermDebtMaturitiesRepaymentsOfPrincipalInYearThree_lbl" xml:lang="en-US">2023</link:label>
      <link:loc xlink:type="locator" xlink:href="clsn-20200630.xsd#CLSN_LongTermDebtMaturitiesRepaymentsOfPrincipalYearFourAndThereAfter" xlink:label="CLSN_LongTermDebtMaturitiesRepaymentsOfPrincipalYearFourAndThereAfter" />
      <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="CLSN_LongTermDebtMaturitiesRepaymentsOfPrincipalYearFourAndThereAfter" xlink:to="CLSN_LongTermDebtMaturitiesRepaymentsOfPrincipalYearFourAndThereAfter_lbl" xlink:type="arc" />
      <link:label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="CLSN_LongTermDebtMaturitiesRepaymentsOfPrincipalYearFourAndThereAfter_lbl" xml:lang="en-US">2024 and thereafter</link:label>
      <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_DebtInstrumentCarryingAmount" xlink:to="us-gaap_DebtInstrumentCarryingAmount_2_lbl" xlink:type="arc" />
      <link:label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/verboseLabel" xlink:label="us-gaap_DebtInstrumentCarryingAmount_2_lbl" xml:lang="en-US">Subtotal of future principal payments</link:label>
      <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_DeferredFinanceCostsNet" xlink:label="us-gaap_DeferredFinanceCostsNet" />
      <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_DeferredFinanceCostsNet" xlink:to="us-gaap_DeferredFinanceCostsNet_lbl" xlink:type="arc" />
      <link:label xlink:type="resource" xlink:role="http://www.xbrl.org/2009/role/negatedLabel" xlink:label="us-gaap_DeferredFinanceCostsNet_lbl" xml:lang="en-US">Unamortized debt issuance costs, net</link:label>
      <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_LongTermDebt" xlink:label="us-gaap_LongTermDebt" />
      <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_LongTermDebt" xlink:to="us-gaap_LongTermDebt_lbl" xlink:type="arc" />
      <link:label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/totalLabel" xlink:label="us-gaap_LongTermDebt_lbl" xml:lang="en-US">Total</link:label>
      <link:loc xlink:type="locator" xlink:href="clsn-20200630.xsd#CLSN_ShelfRegistrationStatementAmount" xlink:label="CLSN_ShelfRegistrationStatementAmount" />
      <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="CLSN_ShelfRegistrationStatementAmount" xlink:to="CLSN_ShelfRegistrationStatementAmount_lbl" xlink:type="arc" />
      <link:label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="CLSN_ShelfRegistrationStatementAmount_lbl" xml:lang="en-US">Shelf registration statement amount</link:label>
      <link:loc xlink:type="locator" xlink:href="clsn-20200630.xsd#CLSN_AggregateOfferingPriceAdditions" xlink:label="CLSN_AggregateOfferingPriceAdditions" />
      <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="CLSN_AggregateOfferingPriceAdditions" xlink:to="CLSN_AggregateOfferingPriceAdditions_lbl" xlink:type="arc" />
      <link:label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="CLSN_AggregateOfferingPriceAdditions_lbl" xml:lang="en-US">Aggregate offering price, additions</link:label>
      <link:loc xlink:type="locator" xlink:href="clsn-20200630.xsd#CLSN_AggregateOfferingPriceTerm" xlink:label="CLSN_AggregateOfferingPriceTerm" />
      <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="CLSN_AggregateOfferingPriceTerm" xlink:to="CLSN_AggregateOfferingPriceTerm_lbl" xlink:type="arc" />
      <link:label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="CLSN_AggregateOfferingPriceTerm_lbl" xml:lang="en-US">Aggregate offering price, term</link:label>
      <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_StockIssuedDuringPeriodSharesNewIssues" xlink:to="us-gaap_StockIssuedDuringPeriodSharesNewIssues_2_lbl" xlink:type="arc" />
      <link:label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/verboseLabel" xlink:label="us-gaap_StockIssuedDuringPeriodSharesNewIssues_2_lbl" xml:lang="en-US">Stock issued during period, shares, new issues</link:label>
      <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_ProceedsFromIssuanceOfCommonStock" xlink:to="us-gaap_ProceedsFromIssuanceOfCommonStock_3_lbl" xlink:type="arc" />
      <link:label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:label="us-gaap_ProceedsFromIssuanceOfCommonStock_3_lbl" xml:lang="en-US">Proceeds from issuance of common stock</link:label>
      <link:loc xlink:type="locator" xlink:href="clsn-20200630.xsd#CLSN_AggregateOfferingPrices" xlink:label="CLSN_AggregateOfferingPrices" />
      <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="CLSN_AggregateOfferingPrices" xlink:to="CLSN_AggregateOfferingPrices_lbl" xlink:type="arc" />
      <link:label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="CLSN_AggregateOfferingPrices_lbl" xml:lang="en-US">Aggregate offering price</link:label>
      <link:loc xlink:type="locator" xlink:href="clsn-20200630.xsd#CLSN_AggregateValueAvailableForIssuance" xlink:label="CLSN_AggregateValueAvailableForIssuance" />
      <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="CLSN_AggregateValueAvailableForIssuance" xlink:to="CLSN_AggregateValueAvailableForIssuance_lbl" xlink:type="arc" />
      <link:label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="CLSN_AggregateValueAvailableForIssuance_lbl" xml:lang="en-US">Aggregate value available for issuance</link:label>
      <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_SharesIssuedPricePerShare" xlink:label="us-gaap_SharesIssuedPricePerShare" />
      <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_SharesIssuedPricePerShare" xlink:to="us-gaap_SharesIssuedPricePerShare_lbl" xlink:type="arc" />
      <link:label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_SharesIssuedPricePerShare_lbl" xml:lang="en-US">Shares issued, price per share</link:label>
      <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ClassOfWarrantOrRightNumberOfSecuritiesCalledByEachWarrantOrRight" xlink:label="us-gaap_ClassOfWarrantOrRightNumberOfSecuritiesCalledByEachWarrantOrRight" />
      <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_ClassOfWarrantOrRightNumberOfSecuritiesCalledByEachWarrantOrRight" xlink:to="us-gaap_ClassOfWarrantOrRightNumberOfSecuritiesCalledByEachWarrantOrRight_lbl" xlink:type="arc" />
      <link:label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_ClassOfWarrantOrRightNumberOfSecuritiesCalledByEachWarrantOrRight_lbl" xml:lang="en-US">Number of warrants to purchase common stock</link:label>
      <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_WarrantsAndRightsOutstandingTerm" xlink:label="us-gaap_WarrantsAndRightsOutstandingTerm" />
      <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_WarrantsAndRightsOutstandingTerm" xlink:to="us-gaap_WarrantsAndRightsOutstandingTerm_lbl" xlink:type="arc" />
      <link:label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_WarrantsAndRightsOutstandingTerm_lbl" xml:lang="en-US">Warrants term</link:label>
      <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_SharePrice" xlink:label="us-gaap_SharePrice" />
      <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_SharePrice" xlink:to="us-gaap_SharePrice_lbl" xlink:type="arc" />
      <link:label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_SharePrice_lbl" xml:lang="en-US">Shares purchased, price per share</link:label>
      <link:loc xlink:type="locator" xlink:href="clsn-20200630.xsd#CLSN_UnderwritingDiscountPricePerShare" xlink:label="CLSN_UnderwritingDiscountPricePerShare" />
      <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="CLSN_UnderwritingDiscountPricePerShare" xlink:to="CLSN_UnderwritingDiscountPricePerShare_lbl" xlink:type="arc" />
      <link:label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="CLSN_UnderwritingDiscountPricePerShare_lbl" xml:lang="en-US">Underwriting discount price per share</link:label>
      <link:loc xlink:type="locator" xlink:href="clsn-20200630.xsd#CLSN_PercentageOfUnderwritingDiscountOnPublicOfferingPrice" xlink:label="CLSN_PercentageOfUnderwritingDiscountOnPublicOfferingPrice" />
      <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="CLSN_PercentageOfUnderwritingDiscountOnPublicOfferingPrice" xlink:to="CLSN_PercentageOfUnderwritingDiscountOnPublicOfferingPrice_lbl" xlink:type="arc" />
      <link:label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="CLSN_PercentageOfUnderwritingDiscountOnPublicOfferingPrice_lbl" xml:lang="en-US">Percentage of underwriting discount on public offering price</link:label>
      <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfSharesAuthorized" xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfSharesAuthorized" />
      <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfSharesAuthorized" xlink:to="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfSharesAuthorized_lbl" xlink:type="arc" />
      <link:label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfSharesAuthorized_lbl" xml:lang="en-US">Equity awards, number of stock authorized</link:label>
      <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfSharesAvailableForGrant" xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfSharesAvailableForGrant" />
      <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfSharesAvailableForGrant" xlink:to="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfSharesAvailableForGrant_lbl" xlink:type="arc" />
      <link:label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfSharesAvailableForGrant_lbl" xml:lang="en-US">Number of equity awards available for future issuance</link:label>
      <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriod" xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriod" />
      <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriod" xlink:to="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriod_lbl" xlink:type="arc" />
      <link:label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriod_lbl" xml:lang="en-US">Number of stock options granted, during period</link:label>
      <link:loc xlink:type="locator" xlink:href="clsn-20200630.xsd#CLSN_StockOptionsStrikePriceDescription" xlink:label="CLSN_StockOptionsStrikePriceDescription" />
      <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="CLSN_StockOptionsStrikePriceDescription" xlink:to="CLSN_StockOptionsStrikePriceDescription_lbl" xlink:type="arc" />
      <link:label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="CLSN_StockOptionsStrikePriceDescription_lbl" xml:lang="en-US">Stock options, strike price description</link:label>
      <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_SharesIssued" xlink:label="us-gaap_SharesIssued" />
      <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_SharesIssued" xlink:to="us-gaap_SharesIssued_lbl" xlink:type="arc" />
      <link:label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_SharesIssued_lbl" xml:lang="en-US">Number of shares issued</link:label>
      <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardOptionsGrantsInPeriodWeightedAverageExercisePrice" xlink:label="us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardOptionsGrantsInPeriodWeightedAverageExercisePrice" />
      <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardOptionsGrantsInPeriodWeightedAverageExercisePrice" xlink:to="us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardOptionsGrantsInPeriodWeightedAverageExercisePrice_lbl" xlink:type="arc" />
      <link:label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardOptionsGrantsInPeriodWeightedAverageExercisePrice_lbl" xml:lang="en-US">Inducement option grant, exercise price per share</link:label>
      <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardAwardVestingPeriod1" xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardAwardVestingPeriod1" />
      <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardAwardVestingPeriod1" xlink:to="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardAwardVestingPeriod1_lbl" xlink:type="arc" />
      <link:label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardAwardVestingPeriod1_lbl" xml:lang="en-US">Option vested period</link:label>
      <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_CommonStockCapitalSharesReservedForFutureIssuance" xlink:label="us-gaap_CommonStockCapitalSharesReservedForFutureIssuance" />
      <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_CommonStockCapitalSharesReservedForFutureIssuance" xlink:to="us-gaap_CommonStockCapitalSharesReservedForFutureIssuance_lbl" xlink:type="arc" />
      <link:label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_CommonStockCapitalSharesReservedForFutureIssuance_lbl" xml:lang="en-US">Number of shares reserved for future issuance</link:label>
      <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_AllocatedShareBasedCompensationExpense" xlink:label="us-gaap_AllocatedShareBasedCompensationExpense" />
      <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_AllocatedShareBasedCompensationExpense" xlink:to="us-gaap_AllocatedShareBasedCompensationExpense_lbl" xlink:type="arc" />
      <link:label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_AllocatedShareBasedCompensationExpense_lbl" xml:lang="en-US">Compensation cost</link:label>
      <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognized" xlink:label="us-gaap_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognized" />
      <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognized" xlink:to="us-gaap_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognized_lbl" xlink:type="arc" />
      <link:label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognized_lbl" xml:lang="en-US">Unrecognized compensation cost related to non-vested stock based compensation</link:label>
      <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognizedPeriodForRecognition1" xlink:label="us-gaap_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognizedPeriodForRecognition1" />
      <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognizedPeriodForRecognition1" xlink:to="us-gaap_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognizedPeriodForRecognition1_lbl" xlink:type="arc" />
      <link:label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognizedPeriodForRecognition1_lbl" xml:lang="en-US">Stock based compensation cost expected to be recognized, weighted average period</link:label>
      <link:loc xlink:type="locator" xlink:href="clsn-20200630.xsd#CLSN_AnnualBonusAwardsPercentage" xlink:label="CLSN_AnnualBonusAwardsPercentage" />
      <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="CLSN_AnnualBonusAwardsPercentage" xlink:to="CLSN_AnnualBonusAwardsPercentage_lbl" xlink:type="arc" />
      <link:label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="CLSN_AnnualBonusAwardsPercentage_lbl" xml:lang="en-US">Annual bonus awards, percentage</link:label>
      <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_ProceedsFromStockOptionsExercised" xlink:to="us-gaap_ProceedsFromStockOptionsExercised_2_lbl" xlink:type="arc" />
      <link:label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/verboseLabel" xlink:label="us-gaap_ProceedsFromStockOptionsExercised_2_lbl" xml:lang="en-US">Gross proceeds from issuance of common stock upon exercise of stock option</link:label>
      <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_StockIssuedDuringPeriodSharesStockOptionsExercised" xlink:to="us-gaap_StockIssuedDuringPeriodSharesStockOptionsExercised_2_lbl" xlink:type="arc" />
      <link:label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/verboseLabel" xlink:label="us-gaap_StockIssuedDuringPeriodSharesStockOptionsExercised_2_lbl" xml:lang="en-US">Shares of common stock issued upon exercise of stock option</link:label>
      <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingNumber" xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingNumber" />
      <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingNumber" xlink:to="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingNumber_lbl" xlink:type="arc" />
      <link:label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/periodStartLabel" xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingNumber_lbl" xml:lang="en-US">Number Outstanding, Outstanding, Beginning Balance</link:label>
      <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriod" xlink:to="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriod_2_lbl" xlink:type="arc" />
      <link:label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/verboseLabel" xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriod_2_lbl" xml:lang="en-US">Number Outstanding, Granted</link:label>
      <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_StockIssuedDuringPeriodSharesStockOptionsExercised" xlink:to="us-gaap_StockIssuedDuringPeriodSharesStockOptionsExercised_3_lbl" xlink:type="arc" />
      <link:label xlink:type="resource" xlink:role="http://www.xbrl.org/2009/role/negatedLabel" xlink:label="us-gaap_StockIssuedDuringPeriodSharesStockOptionsExercised_3_lbl" xml:lang="en-US">Number Outstanding, Options exercised</link:label>
      <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsVestedNumberOfShares" xlink:label="us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsVestedNumberOfShares" />
      <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsVestedNumberOfShares" xlink:to="us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsVestedNumberOfShares_lbl" xlink:type="arc" />
      <link:label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsVestedNumberOfShares_lbl" xml:lang="en-US">Number Outstanding, Vested and issued</link:label>
      <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsForfeituresAndExpirationsInPeriod" xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsForfeituresAndExpirationsInPeriod" />
      <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsForfeituresAndExpirationsInPeriod" xlink:to="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsForfeituresAndExpirationsInPeriod_lbl" xlink:type="arc" />
      <link:label xlink:type="resource" xlink:role="http://www.xbrl.org/2009/role/negatedLabel" xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsForfeituresAndExpirationsInPeriod_lbl" xml:lang="en-US">Number Outstanding, Forfeited, cancelled or expired</link:label>
      <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingNumber" xlink:to="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingNumber_2_lbl" xlink:type="arc" />
      <link:label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/periodEndLabel" xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingNumber_2_lbl" xml:lang="en-US">Number Outstanding, Ending Balance</link:label>
      <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsExercisableNumber" xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsExercisableNumber" />
      <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsExercisableNumber" xlink:to="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsExercisableNumber_lbl" xlink:type="arc" />
      <link:label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/periodEndLabel" xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsExercisableNumber_lbl" xml:lang="en-US">Number Outstanding, Exercisable</link:label>
      <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingWeightedAverageExercisePrice" xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingWeightedAverageExercisePrice" />
      <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingWeightedAverageExercisePrice" xlink:to="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingWeightedAverageExercisePrice_lbl" xlink:type="arc" />
      <link:label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/periodStartLabel" xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingWeightedAverageExercisePrice_lbl" xml:lang="en-US">Weighted Average Exercise Price, Outstanding, Beginning Balance</link:label>
      <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardOptionsGrantsInPeriodWeightedAverageExercisePrice" xlink:to="us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardOptionsGrantsInPeriodWeightedAverageExercisePrice_2_lbl" xlink:type="arc" />
      <link:label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/verboseLabel" xlink:label="us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardOptionsGrantsInPeriodWeightedAverageExercisePrice_2_lbl" xml:lang="en-US">Weighted Average Exercise Price, Granted</link:label>
      <link:loc xlink:type="locator" xlink:href="clsn-20200630.xsd#CLSN_ShareBasedCompensationArrangementsByShareBasedPaymentAwardOptionsExerciseInPeriodWeightedAverageExercisePrice" xlink:label="CLSN_ShareBasedCompensationArrangementsByShareBasedPaymentAwardOptionsExerciseInPeriodWeightedAverageExercisePrice" />
      <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="CLSN_ShareBasedCompensationArrangementsByShareBasedPaymentAwardOptionsExerciseInPeriodWeightedAverageExercisePrice" xlink:to="CLSN_ShareBasedCompensationArrangementsByShareBasedPaymentAwardOptionsExerciseInPeriodWeightedAverageExercisePrice_lbl" xlink:type="arc" />
      <link:label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="CLSN_ShareBasedCompensationArrangementsByShareBasedPaymentAwardOptionsExerciseInPeriodWeightedAverageExercisePrice_lbl" xml:lang="en-US">Weighted Average Exercise Price, Options exercised</link:label>
      <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsVestedWeightedAverageGrantDateFairValue" xlink:label="us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsVestedWeightedAverageGrantDateFairValue" />
      <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsVestedWeightedAverageGrantDateFairValue" xlink:to="us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsVestedWeightedAverageGrantDateFairValue_lbl" xlink:type="arc" />
      <link:label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsVestedWeightedAverageGrantDateFairValue_lbl" xml:lang="en-US">Weighted Average Exercise Price, Vested and issued</link:label>
      <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsForfeituresAndExpirationsInPeriodWeightedAverageExercisePrice" xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsForfeituresAndExpirationsInPeriodWeightedAverageExercisePrice" />
      <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsForfeituresAndExpirationsInPeriodWeightedAverageExercisePrice" xlink:to="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsForfeituresAndExpirationsInPeriodWeightedAverageExercisePrice_lbl" xlink:type="arc" />
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      <link:label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="CLSN_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsExerciseInPeriod_lbl" xml:lang="en-US">Number Outstanding, Non-vested stock awards outstanding, Options exercised</link:label>
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      <link:label xlink:type="resource" xlink:role="http://www.xbrl.org/2009/role/negatedLabel" xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriod_lbl" xml:lang="en-US">Number Outstanding, Non-vested stock awards outstanding, Vested and issued</link:label>
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      <link:label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsForfeitedInPeriod_lbl" xml:lang="en-US">Number Outstanding, Non-vested stock awards outstanding, Forfeited</link:label>
      <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedNumber" xlink:to="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedNumber_2_lbl" xlink:type="arc" />
      <link:label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/periodEndLabel" xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedNumber_2_lbl" xml:lang="en-US">Number Outstanding, Non-vested stock awards outstanding, Ending Balance</link:label>
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      <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValue" xlink:to="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValue_lbl" xlink:type="arc" />
      <link:label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/periodStartLabel" xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValue_lbl" xml:lang="en-US">Weighted Average Grant Date Fair Value, Non-vested stock awards, Beginning Balance</link:label>
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      <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriodWeightedAverageGrantDateFairValue" xlink:to="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriodWeightedAverageGrantDateFairValue_lbl" xlink:type="arc" />
      <link:label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriodWeightedAverageGrantDateFairValue_lbl" xml:lang="en-US">Weighted Average Grant Date Fair Value, Non-vested stock awards, Granted</link:label>
      <link:loc xlink:type="locator" xlink:href="clsn-20200630.xsd#CLSN_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsExerciseInPeriodWeightedAverageGrantDateFairValue" xlink:label="CLSN_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsExerciseInPeriodWeightedAverageGrantDateFairValue" />
      <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="CLSN_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsExerciseInPeriodWeightedAverageGrantDateFairValue" xlink:to="CLSN_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsExerciseInPeriodWeightedAverageGrantDateFairValue_lbl" xlink:type="arc" />
      <link:label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="CLSN_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsExerciseInPeriodWeightedAverageGrantDateFairValue_lbl" xml:lang="en-US">Weighted Average Grant Date Fair Value, Non-vested stock awards, Options exercised</link:label>
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      <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriodWeightedAverageGrantDateFairValue" xlink:to="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriodWeightedAverageGrantDateFairValue_lbl" xlink:type="arc" />
      <link:label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriodWeightedAverageGrantDateFairValue_lbl" xml:lang="en-US">Weighted Average Grant Date Fair Value, Non-vested stock awards, Vested and issued</link:label>
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      <link:label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsForfeituresWeightedAverageGrantDateFairValue_lbl" xml:lang="en-US">Weighted Average Grant Date Fair Value, Non-vested stock awards, Forfeited</link:label>
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      <link:label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/periodEndLabel" xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValue_2_lbl" xml:lang="en-US">Weighted Average Grant Date Fair Value, Non-vested stock awards, Ending Balance</link:label>
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      <link:label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/periodEndLabel" xlink:label="us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardEquityInstrumentsOtherThanOptionsAggregateIntrinsicValueOutstanding_lbl" xml:lang="en-US">Aggregate Intrinsic Value, Outstanding, Non-vested stock awards, Ending Balance</link:label>
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      <link:label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsRiskFreeInterestRateMinimum_lbl" xml:lang="en-US">Risk-free interest rate, minimum</link:label>
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      <link:label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsExpectedVolatilityRateMaximum_lbl" xml:lang="en-US">Expected volatility, maximum</link:label>
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      <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardFairValueAssumptionsExpectedTerm1" xlink:to="us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardFairValueAssumptionsExpectedTerm1_lbl" xlink:type="arc" />
      <link:label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardFairValueAssumptionsExpectedTerm1_lbl" xml:lang="en-US">Expected life (in years)</link:label>
      <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsExpectedDividendRate" xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsExpectedDividendRate" />
      <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsExpectedDividendRate" xlink:to="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsExpectedDividendRate_lbl" xlink:type="arc" />
      <link:label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsExpectedDividendRate_lbl" xml:lang="en-US">Expected dividend yield</link:label>
      <link:loc xlink:type="locator" xlink:href="clsn-20200630.xsd#CLSN_PaymentsForEarnoutMilestoneLiability" xlink:label="CLSN_PaymentsForEarnoutMilestoneLiability" />
      <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="CLSN_PaymentsForEarnoutMilestoneLiability" xlink:to="CLSN_PaymentsForEarnoutMilestoneLiability_lbl" xlink:type="arc" />
      <link:label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="CLSN_PaymentsForEarnoutMilestoneLiability_lbl" xml:lang="en-US">Payments for earnout milestone liability</link:label>
      <link:loc xlink:type="locator" xlink:href="clsn-20200630.xsd#CLSN_PaymentsForEarnoutMilestoneLiabilityInCash" xlink:label="CLSN_PaymentsForEarnoutMilestoneLiabilityInCash" />
      <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="CLSN_PaymentsForEarnoutMilestoneLiabilityInCash" xlink:to="CLSN_PaymentsForEarnoutMilestoneLiabilityInCash_lbl" xlink:type="arc" />
      <link:label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="CLSN_PaymentsForEarnoutMilestoneLiabilityInCash_lbl" xml:lang="en-US">Payments for earnout milestone liability in cash</link:label>
      <link:loc xlink:type="locator" xlink:href="clsn-20200630.xsd#CLSN_EarnoutMilestoneLiability1" xlink:label="CLSN_EarnoutMilestoneLiability1" />
      <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="CLSN_EarnoutMilestoneLiability1" xlink:to="CLSN_EarnoutMilestoneLiability1_lbl" xlink:type="arc" />
      <link:label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="CLSN_EarnoutMilestoneLiability1_lbl" xml:lang="en-US">Earnout milestone liability</link:label>
      <link:loc xlink:type="locator" xlink:href="clsn-20200630.xsd#CLSN_GainOnNoncashBenefit" xlink:label="CLSN_GainOnNoncashBenefit" />
      <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="CLSN_GainOnNoncashBenefit" xlink:to="CLSN_GainOnNoncashBenefit_lbl" xlink:type="arc" />
      <link:label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="CLSN_GainOnNoncashBenefit_lbl" xml:lang="en-US">Gain on non-cash benefit</link:label>
      <link:loc xlink:type="locator" xlink:href="clsn-20200630.xsd#CLSN_RiskAdjustedAssessmentOfEachMilestone" xlink:label="CLSN_RiskAdjustedAssessmentOfEachMilestone" />
      <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="CLSN_RiskAdjustedAssessmentOfEachMilestone" xlink:to="CLSN_RiskAdjustedAssessmentOfEachMilestone_lbl" xlink:type="arc" />
      <link:label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="CLSN_RiskAdjustedAssessmentOfEachMilestone_lbl" xml:lang="en-US">Risk adjusted assessment of each milestone</link:label>
      <link:loc xlink:type="locator" xlink:href="clsn-20200630.xsd#CLSN_GainLossFromChangeInFairValueOfEarnOutMilestoneLiability" xlink:label="CLSN_GainLossFromChangeInFairValueOfEarnOutMilestoneLiability" />
      <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="CLSN_GainLossFromChangeInFairValueOfEarnOutMilestoneLiability" xlink:to="CLSN_GainLossFromChangeInFairValueOfEarnOutMilestoneLiability_lbl" xlink:type="arc" />
      <link:label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="CLSN_GainLossFromChangeInFairValueOfEarnOutMilestoneLiability_lbl" xml:lang="en-US">Gain (loss) from change in fair value of earn out milestone liability</link:label>
      <link:loc xlink:type="locator" xlink:href="clsn-20200630.xsd#CLSN_EarnoutMilestoneLiability" xlink:label="CLSN_EarnoutMilestoneLiability" />
      <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="CLSN_EarnoutMilestoneLiability" xlink:to="CLSN_EarnoutMilestoneLiability_lbl" xlink:type="arc" />
      <link:label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/periodStartLabel" xlink:label="CLSN_EarnoutMilestoneLiability_lbl" xml:lang="en-US">Earn-out liabilities, beginning balance</link:label>
      <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="CLSN_GainLossFromChangeInFairValueOfEarnOutMilestoneLiability" xlink:to="CLSN_GainLossFromChangeInFairValueOfEarnOutMilestoneLiability_2_lbl" xlink:type="arc" />
      <link:label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/verboseLabel" xlink:label="CLSN_GainLossFromChangeInFairValueOfEarnOutMilestoneLiability_2_lbl" xml:lang="en-US">Non-cash loss from the change in fair value</link:label>
      <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="CLSN_EarnoutMilestoneLiability" xlink:to="CLSN_EarnoutMilestoneLiability_2_lbl" xlink:type="arc" />
      <link:label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/periodEndLabel" xlink:label="CLSN_EarnoutMilestoneLiability_2_lbl" xml:lang="en-US">Earn-out liabilities, ending balance</link:label>
      <link:loc xlink:type="locator" xlink:href="clsn-20200630.xsd#CLSN_RiskadjustmentAssessmentOfAchievingEachMilestone" xlink:label="CLSN_RiskadjustmentAssessmentOfAchievingEachMilestone" />
      <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="CLSN_RiskadjustmentAssessmentOfAchievingEachMilestone" xlink:to="CLSN_RiskadjustmentAssessmentOfAchievingEachMilestone_lbl" xlink:type="arc" />
      <link:label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="CLSN_RiskadjustmentAssessmentOfAchievingEachMilestone_lbl" xml:lang="en-US">Risk-adjustment Assessment of achieving each Milestone</link:label>
      <link:loc xlink:type="locator" xlink:href="clsn-20200630.xsd#CLSN_DiscountRateOnMileStoneLiabilities" xlink:label="CLSN_DiscountRateOnMileStoneLiabilities" />
      <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="CLSN_DiscountRateOnMileStoneLiabilities" xlink:to="CLSN_DiscountRateOnMileStoneLiabilities_lbl" xlink:type="arc" />
      <link:label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="CLSN_DiscountRateOnMileStoneLiabilities_lbl" xml:lang="en-US">Discount Rate</link:label>
      <link:loc xlink:type="locator" xlink:href="clsn-20200630.xsd#CLSN_EstimatedTimeToAchieveMileStone" xlink:label="CLSN_EstimatedTimeToAchieveMileStone" />
      <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="CLSN_EstimatedTimeToAchieveMileStone" xlink:to="CLSN_EstimatedTimeToAchieveMileStone_lbl" xlink:type="arc" />
      <link:label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="CLSN_EstimatedTimeToAchieveMileStone_lbl" xml:lang="en-US">Estimated Time to Achieve</link:label>
      <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNonOptionEquityInstrumentsOutstandingNumber" xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNonOptionEquityInstrumentsOutstandingNumber" />
      <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNonOptionEquityInstrumentsOutstandingNumber" xlink:to="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNonOptionEquityInstrumentsOutstandingNumber_lbl" xlink:type="arc" />
      <link:label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/periodStartLabel" xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNonOptionEquityInstrumentsOutstandingNumber_lbl" xml:lang="en-US">Number of Warrants Issued, Warrants Outstanding, Beginning Balance</link:label>
      <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNonOptionEquityInstrumentsGranted" xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNonOptionEquityInstrumentsGranted" />
      <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNonOptionEquityInstrumentsGranted" xlink:to="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNonOptionEquityInstrumentsGranted_lbl" xlink:type="arc" />
      <link:label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNonOptionEquityInstrumentsGranted_lbl" xml:lang="en-US">Number of Warrants Issued, Warrants Issued</link:label>
      <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNonOptionEquityInstrumentsOutstandingNumber" xlink:to="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNonOptionEquityInstrumentsOutstandingNumber_2_lbl" xlink:type="arc" />
      <link:label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/periodEndLabel" xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNonOptionEquityInstrumentsOutstandingNumber_2_lbl" xml:lang="en-US">Number of Warrants Issued, Warrants Outstanding, Ending Balance</link:label>
      <link:loc xlink:type="locator" xlink:href="clsn-20200630.xsd#CLSN_ShareBasedCompensationArrangementByShareBasedPaymentAwardNonOptionEquityInstrumentsOutstandingWeightedAverageExercisePrice" xlink:label="CLSN_ShareBasedCompensationArrangementByShareBasedPaymentAwardNonOptionEquityInstrumentsOutstandingWeightedAverageExercisePrice" />
      <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="CLSN_ShareBasedCompensationArrangementByShareBasedPaymentAwardNonOptionEquityInstrumentsOutstandingWeightedAverageExercisePrice" xlink:to="CLSN_ShareBasedCompensationArrangementByShareBasedPaymentAwardNonOptionEquityInstrumentsOutstandingWeightedAverageExercisePrice_lbl" xlink:type="arc" />
      <link:label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/periodStartLabel" xlink:label="CLSN_ShareBasedCompensationArrangementByShareBasedPaymentAwardNonOptionEquityInstrumentsOutstandingWeightedAverageExercisePrice_lbl" xml:lang="en-US">Weighted Average Exercise Price, Warrants Outstanding, Beginning Balance</link:label>
      <link:loc xlink:type="locator" xlink:href="clsn-20200630.xsd#CLSN_ShareBasedCompensationArrangementByShareBasedPaymentAwardNonOptionEquityInstrumentsGrantsInPeriodWeightedAverageExercisePrice" xlink:label="CLSN_ShareBasedCompensationArrangementByShareBasedPaymentAwardNonOptionEquityInstrumentsGrantsInPeriodWeightedAverageExercisePrice" />
      <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="CLSN_ShareBasedCompensationArrangementByShareBasedPaymentAwardNonOptionEquityInstrumentsGrantsInPeriodWeightedAverageExercisePrice" xlink:to="CLSN_ShareBasedCompensationArrangementByShareBasedPaymentAwardNonOptionEquityInstrumentsGrantsInPeriodWeightedAverageExercisePrice_lbl" xlink:type="arc" />
      <link:label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="CLSN_ShareBasedCompensationArrangementByShareBasedPaymentAwardNonOptionEquityInstrumentsGrantsInPeriodWeightedAverageExercisePrice_lbl" xml:lang="en-US">Weighted Average Exercise Price, Warrants Issued</link:label>
      <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="CLSN_ShareBasedCompensationArrangementByShareBasedPaymentAwardNonOptionEquityInstrumentsOutstandingWeightedAverageExercisePrice" xlink:to="CLSN_ShareBasedCompensationArrangementByShareBasedPaymentAwardNonOptionEquityInstrumentsOutstandingWeightedAverageExercisePrice_2_lbl" xlink:type="arc" />
      <link:label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/periodEndLabel" xlink:label="CLSN_ShareBasedCompensationArrangementByShareBasedPaymentAwardNonOptionEquityInstrumentsOutstandingWeightedAverageExercisePrice_2_lbl" xml:lang="en-US">Weighted Average Exercise Price, Warrants Outstanding, Ending Balance</link:label>
      <link:loc xlink:type="locator" xlink:href="clsn-20200630.xsd#CLSN_ShareBasedCompensationArrangementByShareBasedPaymentAwardNonOptionsOutstandingIntrinsicValue" xlink:label="CLSN_ShareBasedCompensationArrangementByShareBasedPaymentAwardNonOptionsOutstandingIntrinsicValue" />
      <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="CLSN_ShareBasedCompensationArrangementByShareBasedPaymentAwardNonOptionsOutstandingIntrinsicValue" xlink:to="CLSN_ShareBasedCompensationArrangementByShareBasedPaymentAwardNonOptionsOutstandingIntrinsicValue_lbl" xlink:type="arc" />
      <link:label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/periodStartLabel" xlink:label="CLSN_ShareBasedCompensationArrangementByShareBasedPaymentAwardNonOptionsOutstandingIntrinsicValue_lbl" xml:lang="en-US">Aggregate Intrinsic Value of Outstanding Warrants</link:label>
      <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNonOptionEquityInstrumentsGranted" xlink:to="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNonOptionEquityInstrumentsGranted_2_lbl" xlink:type="arc" />
      <link:label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/verboseLabel" xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNonOptionEquityInstrumentsGranted_2_lbl" xml:lang="en-US">Number of Warrants Issued</link:label>
      <link:loc xlink:type="locator" xlink:href="clsn-20200630.xsd#CLSN_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriodWeightedAverageIssuedDateFairValue" xlink:label="CLSN_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriodWeightedAverageIssuedDateFairValue" />
      <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="CLSN_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriodWeightedAverageIssuedDateFairValue" xlink:to="CLSN_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriodWeightedAverageIssuedDateFairValue_lbl" xlink:type="arc" />
      <link:label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="CLSN_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriodWeightedAverageIssuedDateFairValue_lbl" xml:lang="en-US">Weighted Average Exercise Price</link:label>
      <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsOutstandingWeightedAverageRemainingContractualTerms" xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsOutstandingWeightedAverageRemainingContractualTerms" />
      <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsOutstandingWeightedAverageRemainingContractualTerms" xlink:to="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsOutstandingWeightedAverageRemainingContractualTerms_lbl" xlink:type="arc" />
      <link:label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsOutstandingWeightedAverageRemainingContractualTerms_lbl" xml:lang="en-US">Weighted Average Contractual Terms Remaining (in years)</link:label>
      <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_AdjustmentsForNewAccountingPronouncementsAxis" xlink:to="us-gaap_AdjustmentsForNewAccountingPronouncementsAxis_2_lbl" xlink:type="arc" />
      <link:label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/verboseLabel" xlink:label="us-gaap_AdjustmentsForNewAccountingPronouncementsAxis_2_lbl" xml:lang="en-US">Accounting Standards Update [Axis]</link:label>
      <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_AreaOfLand" xlink:label="us-gaap_AreaOfLand" />
      <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_AreaOfLand" xlink:to="us-gaap_AreaOfLand_lbl" xlink:type="arc" />
      <link:label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_AreaOfLand_lbl" xml:lang="en-US">Area of land</link:label>
      <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_LeaseExpirationDate1" xlink:label="us-gaap_LeaseExpirationDate1" />
      <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_LeaseExpirationDate1" xlink:to="us-gaap_LeaseExpirationDate1_lbl" xlink:type="arc" />
      <link:label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_LeaseExpirationDate1_lbl" xml:lang="en-US">Lease expiration date</link:label>
      <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_OperatingLeaseRightOfUseAsset" xlink:to="us-gaap_OperatingLeaseRightOfUseAsset_2_lbl" xlink:type="arc" />
      <link:label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/verboseLabel" xlink:label="us-gaap_OperatingLeaseRightOfUseAsset_2_lbl" xml:lang="en-US">ROU asset</link:label>
      <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_OperatingLeaseLiability" xlink:label="us-gaap_OperatingLeaseLiability" />
      <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_OperatingLeaseLiability" xlink:to="us-gaap_OperatingLeaseLiability_lbl" xlink:type="arc" />
      <link:label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_OperatingLeaseLiability_lbl" xml:lang="en-US">Operating lease liabilities</link:label>
      <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_OtherLiabilities" xlink:label="us-gaap_OtherLiabilities" />
      <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_OtherLiabilities" xlink:to="us-gaap_OtherLiabilities_lbl" xlink:type="arc" />
      <link:label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_OtherLiabilities_lbl" xml:lang="en-US">Other liabilities</link:label>
      <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_RightOfUseAssetObtainedInExchangeForOperatingLeaseLiability" xlink:label="us-gaap_RightOfUseAssetObtainedInExchangeForOperatingLeaseLiability" />
      <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_RightOfUseAssetObtainedInExchangeForOperatingLeaseLiability" xlink:to="us-gaap_RightOfUseAssetObtainedInExchangeForOperatingLeaseLiability_lbl" xlink:type="arc" />
      <link:label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_RightOfUseAssetObtainedInExchangeForOperatingLeaseLiability_lbl" xml:lang="en-US">Increased ROU asset</link:label>
      <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_OperatingLeasePayments" xlink:to="us-gaap_OperatingLeasePayments_2_lbl" xlink:type="arc" />
      <link:label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/verboseLabel" xlink:label="us-gaap_OperatingLeasePayments_2_lbl" xml:lang="en-US">Operating lease expense</link:label>
      <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_OperatingLeaseCost" xlink:label="us-gaap_OperatingLeaseCost" />
      <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_OperatingLeaseCost" xlink:to="us-gaap_OperatingLeaseCost_lbl" xlink:type="arc" />
      <link:label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_OperatingLeaseCost_lbl" xml:lang="en-US">Operating lease costs</link:label>
      <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_LesseeOperatingLeaseLiabilityPaymentsRemainderOfFiscalYear" xlink:label="us-gaap_LesseeOperatingLeaseLiabilityPaymentsRemainderOfFiscalYear" />
      <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_LesseeOperatingLeaseLiabilityPaymentsRemainderOfFiscalYear" xlink:to="us-gaap_LesseeOperatingLeaseLiabilityPaymentsRemainderOfFiscalYear_lbl" xlink:type="arc" />
      <link:label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_LesseeOperatingLeaseLiabilityPaymentsRemainderOfFiscalYear_lbl" xml:lang="en-US">Remainder of 2020</link:label>
      <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_LesseeOperatingLeaseLiabilityPaymentsDueNextTwelveMonths" xlink:label="us-gaap_LesseeOperatingLeaseLiabilityPaymentsDueNextTwelveMonths" />
      <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_LesseeOperatingLeaseLiabilityPaymentsDueNextTwelveMonths" xlink:to="us-gaap_LesseeOperatingLeaseLiabilityPaymentsDueNextTwelveMonths_lbl" xlink:type="arc" />
      <link:label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/verboseLabel" xlink:label="us-gaap_LesseeOperatingLeaseLiabilityPaymentsDueNextTwelveMonths_lbl" xml:lang="en-US">2021</link:label>
      <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_LesseeOperatingLeaseLiabilityPaymentsDueYearTwo" xlink:label="us-gaap_LesseeOperatingLeaseLiabilityPaymentsDueYearTwo" />
      <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_LesseeOperatingLeaseLiabilityPaymentsDueYearTwo" xlink:to="us-gaap_LesseeOperatingLeaseLiabilityPaymentsDueYearTwo_lbl" xlink:type="arc" />
      <link:label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/verboseLabel" xlink:label="us-gaap_LesseeOperatingLeaseLiabilityPaymentsDueYearTwo_lbl" xml:lang="en-US">2022</link:label>
      <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_LesseeOperatingLeaseLiabilityPaymentsDueYearThree" xlink:label="us-gaap_LesseeOperatingLeaseLiabilityPaymentsDueYearThree" />
      <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_LesseeOperatingLeaseLiabilityPaymentsDueYearThree" xlink:to="us-gaap_LesseeOperatingLeaseLiabilityPaymentsDueYearThree_lbl" xlink:type="arc" />
      <link:label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/verboseLabel" xlink:label="us-gaap_LesseeOperatingLeaseLiabilityPaymentsDueYearThree_lbl" xml:lang="en-US">2023</link:label>
      <link:loc xlink:type="locator" xlink:href="clsn-20200630.xsd#CLSN_LesseeOperatingLeaseLiabilityPaymentsDueYearFourAndThereAfter" xlink:label="CLSN_LesseeOperatingLeaseLiabilityPaymentsDueYearFourAndThereAfter" />
      <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="CLSN_LesseeOperatingLeaseLiabilityPaymentsDueYearFourAndThereAfter" xlink:to="CLSN_LesseeOperatingLeaseLiabilityPaymentsDueYearFourAndThereAfter_lbl" xlink:type="arc" />
      <link:label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/verboseLabel" xlink:label="CLSN_LesseeOperatingLeaseLiabilityPaymentsDueYearFourAndThereAfter_lbl" xml:lang="en-US">2024 and thereafter</link:label>
      <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_LesseeOperatingLeaseLiabilityPaymentsDue" xlink:label="us-gaap_LesseeOperatingLeaseLiabilityPaymentsDue" />
      <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_LesseeOperatingLeaseLiabilityPaymentsDue" xlink:to="us-gaap_LesseeOperatingLeaseLiabilityPaymentsDue_lbl" xlink:type="arc" />
      <link:label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/totalLabel" xlink:label="us-gaap_LesseeOperatingLeaseLiabilityPaymentsDue_lbl" xml:lang="en-US">Subtotal future lease payments</link:label>
      <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_LesseeOperatingLeaseLiabilityUndiscountedExcessAmount" xlink:label="us-gaap_LesseeOperatingLeaseLiabilityUndiscountedExcessAmount" />
      <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_LesseeOperatingLeaseLiabilityUndiscountedExcessAmount" xlink:to="us-gaap_LesseeOperatingLeaseLiabilityUndiscountedExcessAmount_lbl" xlink:type="arc" />
      <link:label xlink:type="resource" xlink:role="http://www.xbrl.org/2009/role/negatedLabel" xlink:label="us-gaap_LesseeOperatingLeaseLiabilityUndiscountedExcessAmount_lbl" xml:lang="en-US">Less imputed interest</link:label>
      <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_OperatingLeaseLiability" xlink:to="us-gaap_OperatingLeaseLiability_2_lbl" xlink:type="arc" />
      <link:label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/verboseLabel" xlink:label="us-gaap_OperatingLeaseLiability_2_lbl" xml:lang="en-US">Total lease liabilities</link:label>
      <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_OperatingLeaseWeightedAverageRemainingLeaseTerm1" xlink:label="us-gaap_OperatingLeaseWeightedAverageRemainingLeaseTerm1" />
      <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_OperatingLeaseWeightedAverageRemainingLeaseTerm1" xlink:to="us-gaap_OperatingLeaseWeightedAverageRemainingLeaseTerm1_lbl" xlink:type="arc" />
      <link:label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_OperatingLeaseWeightedAverageRemainingLeaseTerm1_lbl" xml:lang="en-US">Weighted average remaining life</link:label>
      <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_OperatingLeaseWeightedAverageDiscountRatePercent" xlink:label="us-gaap_OperatingLeaseWeightedAverageDiscountRatePercent" />
      <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_OperatingLeaseWeightedAverageDiscountRatePercent" xlink:to="us-gaap_OperatingLeaseWeightedAverageDiscountRatePercent_lbl" xlink:type="arc" />
      <link:label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_OperatingLeaseWeightedAverageDiscountRatePercent_lbl" xml:lang="en-US">Weighted average discount rate</link:label>
      <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ProceedsFromLicenseFeesReceived" xlink:label="us-gaap_ProceedsFromLicenseFeesReceived" />
      <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_ProceedsFromLicenseFeesReceived" xlink:to="us-gaap_ProceedsFromLicenseFeesReceived_lbl" xlink:type="arc" />
      <link:label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_ProceedsFromLicenseFeesReceived_lbl" xml:lang="en-US">Non-refundable research and development fee</link:label>
      <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_DeferredRevenue" xlink:label="us-gaap_DeferredRevenue" />
      <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_DeferredRevenue" xlink:to="us-gaap_DeferredRevenue_lbl" xlink:type="arc" />
      <link:label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_DeferredRevenue_lbl" xml:lang="en-US">Deferred revenue</link:label>
      <link:loc xlink:type="locator" xlink:href="clsn-20200630.xsd#CLSN_DeferredRevenueAmortizationPeriod" xlink:label="CLSN_DeferredRevenueAmortizationPeriod" />
      <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="CLSN_DeferredRevenueAmortizationPeriod" xlink:to="CLSN_DeferredRevenueAmortizationPeriod_lbl" xlink:type="arc" />
      <link:label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="CLSN_DeferredRevenueAmortizationPeriod_lbl" xml:lang="en-US">Deferred revenue amortization period</link:label>
      <link:loc xlink:type="locator" xlink:href="clsn-20200630.xsd#CLSN_UpfrontPayment" xlink:label="CLSN_UpfrontPayment" />
      <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="CLSN_UpfrontPayment" xlink:to="CLSN_UpfrontPayment_lbl" xlink:type="arc" />
      <link:label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="CLSN_UpfrontPayment_lbl" xml:lang="en-US">Upfront payment</link:label>
      <link:loc xlink:type="locator" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_LitigationSettlementExpense" xlink:label="us-gaap_LitigationSettlementExpense" />
      <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_LitigationSettlementExpense" xlink:to="us-gaap_LitigationSettlementExpense_lbl" xlink:type="arc" />
      <link:label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_LitigationSettlementExpense_lbl" xml:lang="en-US">Payment of legal fees</link:label>
      <link:loc xlink:type="locator" xlink:href="clsn-20200630.xsd#CLSN_ATMAgreementMember" xlink:label="CLSN_ATMAgreementMember" />
      <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="CLSN_ATMAgreementMember" xlink:to="CLSN_ATMAgreementMember_doc" xlink:type="arc" />
      <link:label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:label="CLSN_ATMAgreementMember_doc" xml:lang="en-US">Represents Controlled Equity Offering Sales Agreement (the &amp;amp;amp;amp;amp;amp;amp;amp;#8220;ATM Agreement&amp;amp;amp;amp;amp;amp;amp;amp;#8221;) with Cantor Fitzgerald &amp;amp;amp;amp;amp;amp;amp;amp;amp; Co., as sales agent.</link:label>
      <link:loc xlink:type="locator" xlink:href="clsn-20200630.xsd#CLSN_AchievingMilestoneWithInOneYearMember" xlink:label="CLSN_AchievingMilestoneWithInOneYearMember" />
      <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="CLSN_AchievingMilestoneWithInOneYearMember" xlink:to="CLSN_AchievingMilestoneWithInOneYearMember_doc" xlink:type="arc" />
      <link:label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:label="CLSN_AchievingMilestoneWithInOneYearMember_doc" xml:lang="en-US">Within One Year of Achieving Milestone [Member]</link:label>
      <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="CLSN_AggregateOfferingPriceAdditions" xlink:to="CLSN_AggregateOfferingPriceAdditions_doc" xlink:type="arc" />
      <link:label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:label="CLSN_AggregateOfferingPriceAdditions_doc" xml:lang="en-US">Represents the additional aggregate offering price for shares of common stock that the Company may offer and sell through a sales agent.</link:label>
      <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="CLSN_AggregateOfferingPriceTerm" xlink:to="CLSN_AggregateOfferingPriceTerm_doc" xlink:type="arc" />
      <link:label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:label="CLSN_AggregateOfferingPriceTerm_doc" xml:lang="en-US">Aggregate offering price, term.</link:label>
      <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="CLSN_AggregateOfferingPrices" xlink:to="CLSN_AggregateOfferingPrices_doc" xlink:type="arc" />
      <link:label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:label="CLSN_AggregateOfferingPrices_doc" xml:lang="en-US">Aggregate offering price.</link:label>
      <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="CLSN_AggregateValueAvailableForIssuance" xlink:to="CLSN_AggregateValueAvailableForIssuance_doc" xlink:type="arc" />
      <link:label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:label="CLSN_AggregateValueAvailableForIssuance_doc" xml:lang="en-US">Aggregate value available for issuance.</link:label>
      <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="CLSN_AllOtherWarrantsMember" xlink:to="CLSN_AllOtherWarrantsMember_doc" xlink:type="arc" />
      <link:label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:label="CLSN_AllOtherWarrantsMember_doc" xml:lang="en-US">All Other Warrants [Member]</link:label>
      <link:loc xlink:type="locator" xlink:href="clsn-20200630.xsd#CLSN_AmendedAssetPurchaseAgreementMember" xlink:label="CLSN_AmendedAssetPurchaseAgreementMember" />
      <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="CLSN_AmendedAssetPurchaseAgreementMember" xlink:to="CLSN_AmendedAssetPurchaseAgreementMember_doc" xlink:type="arc" />
      <link:label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:label="CLSN_AmendedAssetPurchaseAgreementMember_doc" xml:lang="en-US">Amended Asset Purchase Agreement [Member]</link:label>
      <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="CLSN_AmendedAssetPurchaseAgreementOptionPaymentOneMember" xlink:to="CLSN_AmendedAssetPurchaseAgreementOptionPaymentOneMember_doc" xlink:type="arc" />
      <link:label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:label="CLSN_AmendedAssetPurchaseAgreementOptionPaymentOneMember_doc" xml:lang="en-US">Amended Asset Purchase Agreement Option Payment 1 [Member]</link:label>
      <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="CLSN_AmendedAssetPurchaseAgreementOptionPaymentTwoMember" xlink:to="CLSN_AmendedAssetPurchaseAgreementOptionPaymentTwoMember_doc" xlink:type="arc" />
      <link:label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:label="CLSN_AmendedAssetPurchaseAgreementOptionPaymentTwoMember_doc" xml:lang="en-US">Amended Asset Purchase Agreement Option Payment 2 [Member]</link:label>
      <link:loc xlink:type="locator" xlink:href="clsn-20200630.xsd#CLSN_AspireCapitalFundLLCMember" xlink:label="CLSN_AspireCapitalFundLLCMember" />
      <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="CLSN_AspireCapitalFundLLCMember" xlink:to="CLSN_AspireCapitalFundLLCMember_doc" xlink:type="arc" />
      <link:label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:label="CLSN_AspireCapitalFundLLCMember_doc" xml:lang="en-US">Aspire Capital Fund, LLC [Member]</link:label>
      <link:loc xlink:type="locator" xlink:href="clsn-20200630.xsd#CLSN_AspirePurchaseAgreementMember" xlink:label="CLSN_AspirePurchaseAgreementMember" />
      <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="CLSN_AspirePurchaseAgreementMember" xlink:to="CLSN_AspirePurchaseAgreementMember_doc" xlink:type="arc" />
      <link:label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:label="CLSN_AspirePurchaseAgreementMember_doc" xml:lang="en-US">Aspire Purchase Agreement [Member]</link:label>
      <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="CLSN_AspirePurchaseAgreementsMember" xlink:to="CLSN_AspirePurchaseAgreementsMember_doc" xlink:type="arc" />
      <link:label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:label="CLSN_AspirePurchaseAgreementsMember_doc" xml:lang="en-US">2018 Aspire Purchase Agreements [Member]</link:label>
      <link:loc xlink:type="locator" xlink:href="clsn-20200630.xsd#CLSN_AssetPurchaseAgreementMember" xlink:label="CLSN_AssetPurchaseAgreementMember" />
      <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="CLSN_AssetPurchaseAgreementMember" xlink:to="CLSN_AssetPurchaseAgreementMember_doc" xlink:type="arc" />
      <link:label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:label="CLSN_AssetPurchaseAgreementMember_doc" xml:lang="en-US">Asset Purchase Agreement [Member]</link:label>
      <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="CLSN_AvailableForSaleDebtSecuritiesAmortizedCostBasisCurrent" xlink:to="CLSN_AvailableForSaleDebtSecuritiesAmortizedCostBasisCurrent_doc" xlink:type="arc" />
      <link:label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:label="CLSN_AvailableForSaleDebtSecuritiesAmortizedCostBasisCurrent_doc" xml:lang="en-US">The current amount of amortized cost of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).</link:label>
      <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="CLSN_AvailableforsaleSecuritiesDebtSecuritiesCurrentAccumulatedUnrealizedGainLoss" xlink:to="CLSN_AvailableforsaleSecuritiesDebtSecuritiesCurrentAccumulatedUnrealizedGainLoss_doc" xlink:type="arc" />
      <link:label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:label="CLSN_AvailableforsaleSecuritiesDebtSecuritiesCurrentAccumulatedUnrealizedGainLoss_doc" xml:lang="en-US">Amount of accumulated unrealized gain (loss) on investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale), in unrealized loss position.</link:label>
      <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="CLSN_CapitalOnDemandAgreementMember" xlink:to="CLSN_CapitalOnDemandAgreementMember_doc" xlink:type="arc" />
      <link:label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:label="CLSN_CapitalOnDemandAgreementMember_doc" xml:lang="en-US">Capital on Demand Agreement [Member]</link:label>
      <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="CLSN_CapitalOnDemandTMSalesAgreementMember" xlink:to="CLSN_CapitalOnDemandTMSalesAgreementMember_doc" xlink:type="arc" />
      <link:label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:label="CLSN_CapitalOnDemandTMSalesAgreementMember_doc" xml:lang="en-US">Capital on DemandTM Sales Agreement [Member]</link:label>
      <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="CLSN_CashInvestmentSecuritiesAndInterestReceivable" xlink:to="CLSN_CashInvestmentSecuritiesAndInterestReceivable_doc" xlink:type="arc" />
      <link:label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:label="CLSN_CashInvestmentSecuritiesAndInterestReceivable_doc" xml:lang="en-US">The amount of cash, investment securities and interest receivable.</link:label>
      <link:loc xlink:type="locator" xlink:href="clsn-20200630.xsd#CLSN_CertainBusinessDaysOfAchievingMilestoneMember" xlink:label="CLSN_CertainBusinessDaysOfAchievingMilestoneMember" />
      <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="CLSN_CertainBusinessDaysOfAchievingMilestoneMember" xlink:to="CLSN_CertainBusinessDaysOfAchievingMilestoneMember_doc" xlink:type="arc" />
      <link:label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:label="CLSN_CertainBusinessDaysOfAchievingMilestoneMember_doc" xml:lang="en-US">10 Business Days of Achieving Milestone [Member]</link:label>
      <link:loc xlink:type="locator" xlink:href="clsn-20200630.xsd#CLSN_CommonStockSalesAgreementMember" xlink:label="CLSN_CommonStockSalesAgreementMember" />
      <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="CLSN_CommonStockSalesAgreementMember" xlink:to="CLSN_CommonStockSalesAgreementMember_doc" xlink:type="arc" />
      <link:label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:label="CLSN_CommonStockSalesAgreementMember_doc" xml:lang="en-US">Common Stock Sales Agreement [Member]</link:label>
      <link:loc xlink:type="locator" xlink:href="clsn-20200630.xsd#CLSN_ControlledEquityOfferingSMSalesAgreementMember" xlink:label="CLSN_ControlledEquityOfferingSMSalesAgreementMember" />
      <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="CLSN_ControlledEquityOfferingSMSalesAgreementMember" xlink:to="CLSN_ControlledEquityOfferingSMSalesAgreementMember_doc" xlink:type="arc" />
      <link:label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:label="CLSN_ControlledEquityOfferingSMSalesAgreementMember_doc" xml:lang="en-US">Controlled Equity Offering SM Sales Agreement [Member]</link:label>
      <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="CLSN_DebtSecuritiesAvailableforsaleContinuousUnrealizedGainPositionLessThan12Months" xlink:to="CLSN_DebtSecuritiesAvailableforsaleContinuousUnrealizedGainPositionLessThan12Months_doc" xlink:type="arc" />
      <link:label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:label="CLSN_DebtSecuritiesAvailableforsaleContinuousUnrealizedGainPositionLessThan12Months_doc" xml:lang="en-US">Amount of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale) unrealized gain less than 12 months.</link:label>
      <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="CLSN_DebtSecuritiesAvailableforsaleContinuousUnrealizedGainPositionLessThan12MonthsAccumulatedGain" xlink:to="CLSN_DebtSecuritiesAvailableforsaleContinuousUnrealizedGainPositionLessThan12MonthsAccumulatedGain_doc" xlink:type="arc" />
      <link:label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:label="CLSN_DebtSecuritiesAvailableforsaleContinuousUnrealizedGainPositionLessThan12MonthsAccumulatedGain_doc" xml:lang="en-US">Amount of accumulated unrealized gain on investment in debt security measured at fair value with change in other comprehensive income (available-for-sale), unrealized gain for less than 12 months.</link:label>
      <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="CLSN_DebtSecuritiesAvailableforsaleMaturityAllocatedAndSingleMaturityDateRollingWithinThreeMonthsAmortizedCost" xlink:to="CLSN_DebtSecuritiesAvailableforsaleMaturityAllocatedAndSingleMaturityDateRollingWithinThreeMonthsAmortizedCost_doc" xlink:type="arc" />
      <link:label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:label="CLSN_DebtSecuritiesAvailableforsaleMaturityAllocatedAndSingleMaturityDateRollingWithinThreeMonthsAmortizedCost_doc" xml:lang="en-US">Amortized cost of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale) with single maturity date and allocated without single maturity date, maturing in next rolling three months.</link:label>
      <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="CLSN_DebtSecuritiesAvailableforsaleMaturityAllocatedAndSingleMaturityDateRollingWithinThreeMonthsFairValue" xlink:to="CLSN_DebtSecuritiesAvailableforsaleMaturityAllocatedAndSingleMaturityDateRollingWithinThreeMonthsFairValue_doc" xlink:type="arc" />
      <link:label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:label="CLSN_DebtSecuritiesAvailableforsaleMaturityAllocatedAndSingleMaturityDateRollingWithinThreeMonthsFairValue_doc" xml:lang="en-US">Fair value of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale), with single maturity date and allocated without single maturity date, maturing in next rolling three months.</link:label>
      <link:loc xlink:type="locator" xlink:href="clsn-20200630.xsd#CLSN_DukeUniversityMember" xlink:label="CLSN_DukeUniversityMember" />
      <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="CLSN_DukeUniversityMember" xlink:to="CLSN_DukeUniversityMember_doc" xlink:type="arc" />
      <link:label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:label="CLSN_DukeUniversityMember_doc" xml:lang="en-US">Duke University [Member]</link:label>
      <link:loc xlink:type="locator" xlink:href="clsn-20200630.xsd#CLSN_EGENAssetPurchaseAgreementMember" xlink:label="CLSN_EGENAssetPurchaseAgreementMember" />
      <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="CLSN_EGENAssetPurchaseAgreementMember" xlink:to="CLSN_EGENAssetPurchaseAgreementMember_doc" xlink:type="arc" />
      <link:label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:label="CLSN_EGENAssetPurchaseAgreementMember_doc" xml:lang="en-US">EGEN Asset Purchase Agreement [Member]</link:label>
      <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="CLSN_EGENIncMember" xlink:to="CLSN_EGENIncMember_doc" xlink:type="arc" />
      <link:label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:label="CLSN_EGENIncMember_doc" xml:lang="en-US">Information pertaining to the business acquisition of EGEN, Inc.</link:label>
      <link:loc xlink:type="locator" xlink:href="clsn-20200630.xsd#CLSN_EGENMember" xlink:label="CLSN_EGENMember" />
      <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="CLSN_EGENMember" xlink:to="CLSN_EGENMember_doc" xlink:type="arc" />
      <link:label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:label="CLSN_EGENMember_doc" xml:lang="en-US">EGEN Inc [Member]</link:label>
      <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="CLSN_EGWUIncMember" xlink:to="CLSN_EGWUIncMember_doc" xlink:type="arc" />
      <link:label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:label="CLSN_EGWUIncMember_doc" xml:lang="en-US">EGWU, Inc [Member]</link:label>
      <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="CLSN_EquityStockAwardsMember" xlink:to="CLSN_EquityStockAwardsMember_doc" xlink:type="arc" />
      <link:label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:label="CLSN_EquityStockAwardsMember_doc" xml:lang="en-US">Equity Stock Awards [Member]</link:label>
      <link:loc xlink:type="locator" xlink:href="clsn-20200630.xsd#CLSN_ExerciseAgreementsMember" xlink:label="CLSN_ExerciseAgreementsMember" />
      <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="CLSN_ExerciseAgreementsMember" xlink:to="CLSN_ExerciseAgreementsMember_doc" xlink:type="arc" />
      <link:label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:label="CLSN_ExerciseAgreementsMember_doc" xml:lang="en-US">Exercise Agreements [Member]</link:label>
      <link:loc xlink:type="locator" xlink:href="clsn-20200630.xsd#CLSN_ExercisePriceOneMember" xlink:label="CLSN_ExercisePriceOneMember" />
      <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="CLSN_ExercisePriceOneMember" xlink:to="CLSN_ExercisePriceOneMember_doc" xlink:type="arc" />
      <link:label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:label="CLSN_ExercisePriceOneMember_doc" xml:lang="en-US">Exercise Price One [Member]</link:label>
      <link:loc xlink:type="locator" xlink:href="clsn-20200630.xsd#CLSN_ExercisePriceTwoMember" xlink:label="CLSN_ExercisePriceTwoMember" />
      <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="CLSN_ExercisePriceTwoMember" xlink:to="CLSN_ExercisePriceTwoMember_doc" xlink:type="arc" />
      <link:label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:label="CLSN_ExercisePriceTwoMember_doc" xml:lang="en-US">Exercise Price Two [Member]</link:label>
      <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="CLSN_FairValueEarnoutMilestoneLiabilityMember" xlink:to="CLSN_FairValueEarnoutMilestoneLiabilityMember_doc" xlink:type="arc" />
      <link:label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:label="CLSN_FairValueEarnoutMilestoneLiabilityMember_doc" xml:lang="en-US">Fair Value Earnout Milestone Liability [Member]</link:label>
      <link:loc xlink:type="locator" xlink:href="clsn-20200630.xsd#CLSN_February142017PublicOfferingMember" xlink:label="CLSN_February142017PublicOfferingMember" />
      <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="CLSN_February142017PublicOfferingMember" xlink:to="CLSN_February142017PublicOfferingMember_doc" xlink:type="arc" />
      <link:label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:label="CLSN_February142017PublicOfferingMember_doc" xml:lang="en-US">Represents the public offering on February 14, 2017.</link:label>
      <link:loc xlink:type="locator" xlink:href="clsn-20200630.xsd#CLSN_FebruaryFourteenTwoThousandAndSeventeenPublicOfferingMember" xlink:label="CLSN_FebruaryFourteenTwoThousandAndSeventeenPublicOfferingMember" />
      <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="CLSN_FebruaryFourteenTwoThousandAndSeventeenPublicOfferingMember" xlink:to="CLSN_FebruaryFourteenTwoThousandAndSeventeenPublicOfferingMember_doc" xlink:type="arc" />
      <link:label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:label="CLSN_FebruaryFourteenTwoThousandAndSeventeenPublicOfferingMember_doc" xml:lang="en-US">February 14, 2017 Public Offering [Member]</link:label>
      <link:loc xlink:type="locator" xlink:href="clsn-20200630.xsd#CLSN_FederalIncomeTaxMember" xlink:label="CLSN_FederalIncomeTaxMember" />
      <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="CLSN_FederalIncomeTaxMember" xlink:to="CLSN_FederalIncomeTaxMember_doc" xlink:type="arc" />
      <link:label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:label="CLSN_FederalIncomeTaxMember_doc" xml:lang="en-US">Federal Income Tax [Member]</link:label>
      <link:loc xlink:type="locator" xlink:href="clsn-20200630.xsd#CLSN_FinalYearMember" xlink:label="CLSN_FinalYearMember" />
      <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="CLSN_FinalYearMember" xlink:to="CLSN_FinalYearMember_doc" xlink:type="arc" />
      <link:label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:label="CLSN_FinalYearMember_doc" xml:lang="en-US">Final Year [Member]</link:label>
      <link:loc xlink:type="locator" xlink:href="clsn-20200630.xsd#CLSN_FirstLeaseAmendmentMember" xlink:label="CLSN_FirstLeaseAmendmentMember" />
      <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="CLSN_FirstLeaseAmendmentMember" xlink:to="CLSN_FirstLeaseAmendmentMember_doc" xlink:type="arc" />
      <link:label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:label="CLSN_FirstLeaseAmendmentMember_doc" xml:lang="en-US">1st Lease Amendment [Member]</link:label>
      <link:loc xlink:type="locator" xlink:href="clsn-20200630.xsd#CLSN_FirstTrancheMember" xlink:label="CLSN_FirstTrancheMember" />
      <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="CLSN_FirstTrancheMember" xlink:to="CLSN_FirstTrancheMember_doc" xlink:type="arc" />
      <link:label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:label="CLSN_FirstTrancheMember_doc" xml:lang="en-US">First Tranche [Member]</link:label>
      <link:loc xlink:type="locator" xlink:href="clsn-20200630.xsd#CLSN_FirstYearMember" xlink:label="CLSN_FirstYearMember" />
      <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="CLSN_FirstYearMember" xlink:to="CLSN_FirstYearMember_doc" xlink:type="arc" />
      <link:label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:label="CLSN_FirstYearMember_doc" xml:lang="en-US">First Year [Member]</link:label>
      <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="CLSN_FiveNewEmployeesMember" xlink:to="CLSN_FiveNewEmployeesMember_doc" xlink:type="arc" />
      <link:label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:label="CLSN_FiveNewEmployeesMember_doc" xml:lang="en-US">Five New Employees [Member]</link:label>
      <link:loc xlink:type="locator" xlink:href="clsn-20200630.xsd#CLSN_GeneralAndAdministrativeExpensesMember" xlink:label="CLSN_GeneralAndAdministrativeExpensesMember" />
      <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="CLSN_GeneralAndAdministrativeExpensesMember" xlink:to="CLSN_GeneralAndAdministrativeExpensesMember_doc" xlink:type="arc" />
      <link:label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:label="CLSN_GeneralAndAdministrativeExpensesMember_doc" xml:lang="en-US">General and Administrative Expenses [Member]</link:label>
      <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="CLSN_GlioblastomaMultiformeBrainCancerMember" xlink:to="CLSN_GlioblastomaMultiformeBrainCancerMember_doc" xlink:type="arc" />
      <link:label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:label="CLSN_GlioblastomaMultiformeBrainCancerMember_doc" xml:lang="en-US">Glioblastoma Multiforme Brain Cancer [Member]</link:label>
      <link:loc xlink:type="locator" xlink:href="clsn-20200630.xsd#CLSN_HerculesCreditAgreementMember" xlink:label="CLSN_HerculesCreditAgreementMember" />
      <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="CLSN_HerculesCreditAgreementMember" xlink:to="CLSN_HerculesCreditAgreementMember_doc" xlink:type="arc" />
      <link:label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:label="CLSN_HerculesCreditAgreementMember_doc" xml:lang="en-US">Represents a loan agreement with Hercules Technology Growth Capital, Inc. (&amp;amp;amp;amp;amp;amp;amp;amp;#8220;Hercules&amp;amp;amp;amp;amp;amp;amp;amp;#8221;).</link:label>
      <link:loc xlink:type="locator" xlink:href="clsn-20200630.xsd#CLSN_HerculesMember" xlink:label="CLSN_HerculesMember" />
      <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="CLSN_HerculesMember" xlink:to="CLSN_HerculesMember_doc" xlink:type="arc" />
      <link:label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:label="CLSN_HerculesMember_doc" xml:lang="en-US">Represents Hercules Technology Growth Capital, Inc..</link:label>
      <link:loc xlink:type="locator" xlink:href="clsn-20200630.xsd#CLSN_HerculesTechnologyGrowthCapitalIncMember" xlink:label="CLSN_HerculesTechnologyGrowthCapitalIncMember" />
      <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="CLSN_HerculesTechnologyGrowthCapitalIncMember" xlink:to="CLSN_HerculesTechnologyGrowthCapitalIncMember_doc" xlink:type="arc" />
      <link:label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:label="CLSN_HerculesTechnologyGrowthCapitalIncMember_doc" xml:lang="en-US">Hercules Technology Growth Capital, Inc. [Member]</link:label>
      <link:loc xlink:type="locator" xlink:href="clsn-20200630.xsd#CLSN_HerculesWarrantMember" xlink:label="CLSN_HerculesWarrantMember" />
      <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="CLSN_HerculesWarrantMember" xlink:to="CLSN_HerculesWarrantMember_doc" xlink:type="arc" />
      <link:label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:label="CLSN_HerculesWarrantMember_doc" xml:lang="en-US">Represents Hercules Technology Growth Capital, Inc..</link:label>
      <link:loc xlink:type="locator" xlink:href="clsn-20200630.xsd#CLSN_HisunAgreementMember" xlink:label="CLSN_HisunAgreementMember" />
      <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="CLSN_HisunAgreementMember" xlink:to="CLSN_HisunAgreementMember_doc" xlink:type="arc" />
      <link:label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:label="CLSN_HisunAgreementMember_doc" xml:lang="en-US">Hisun Agreement [Member]</link:label>
      <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="CLSN_HisunMember" xlink:to="CLSN_HisunMember_doc" xlink:type="arc" />
      <link:label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:label="CLSN_HisunMember_doc" xml:lang="en-US">Hisun [Member]</link:label>
      <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="CLSN_HorizonCreditAgreementMember" xlink:to="CLSN_HorizonCreditAgreementMember_doc" xlink:type="arc" />
      <link:label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:label="CLSN_HorizonCreditAgreementMember_doc" xml:lang="en-US">Horizon Credit Agreement [Member]</link:label>
      <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="CLSN_HorizonTechnologyFinanceCorporationMember" xlink:to="CLSN_HorizonTechnologyFinanceCorporationMember_doc" xlink:type="arc" />
      <link:label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:label="CLSN_HorizonTechnologyFinanceCorporationMember_doc" xml:lang="en-US">Horizon Technology Finance Corporation [Member]</link:label>
      <link:loc xlink:type="locator" xlink:href="clsn-20200630.xsd#CLSN_HorizonWarrantMember" xlink:label="CLSN_HorizonWarrantMember" />
      <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="CLSN_HorizonWarrantMember" xlink:to="CLSN_HorizonWarrantMember_doc" xlink:type="arc" />
      <link:label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:label="CLSN_HorizonWarrantMember_doc" xml:lang="en-US">Horizon Warrants [Member]</link:label>
      <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="CLSN_HuntsvilleAlabamaMember" xlink:to="CLSN_HuntsvilleAlabamaMember_doc" xlink:type="arc" />
      <link:label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:label="CLSN_HuntsvilleAlabamaMember_doc" xml:lang="en-US">Huntsville Alabama [Member]</link:label>
      <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="CLSN_IPRAndDDrugTechnologyPlatformsMember" xlink:to="CLSN_IPRAndDDrugTechnologyPlatformsMember_doc" xlink:type="arc" />
      <link:label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:label="CLSN_IPRAndDDrugTechnologyPlatformsMember_doc" xml:lang="en-US">IPR&amp;amp;amp;amp;amp;amp;amp;D Drug Technology Platforms [Member]</link:label>
      <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="CLSN_IPRAndDMember" xlink:to="CLSN_IPRAndDMember_doc" xlink:type="arc" />
      <link:label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:label="CLSN_IPRAndDMember_doc" xml:lang="en-US">IPR&amp;amp;amp;amp;amp;amp;D [Member]</link:label>
      <link:loc xlink:type="locator" xlink:href="clsn-20200630.xsd#CLSN_InProcessResearchAndDevelopmentTwoMember" xlink:label="CLSN_InProcessResearchAndDevelopmentTwoMember" />
      <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="CLSN_InProcessResearchAndDevelopmentTwoMember" xlink:to="CLSN_InProcessResearchAndDevelopmentTwoMember_doc" xlink:type="arc" />
      <link:label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:label="CLSN_InProcessResearchAndDevelopmentTwoMember_doc" xml:lang="en-US">In Process R and D - GBM Two [Member]</link:label>
      <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="CLSN_InducementAwardsMember" xlink:to="CLSN_InducementAwardsMember_doc" xlink:type="arc" />
      <link:label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:label="CLSN_InducementAwardsMember_doc" xml:lang="en-US">Inducement Awards [Member]</link:label>
      <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="CLSN_InducementOptionGrantsMember" xlink:to="CLSN_InducementOptionGrantsMember_doc" xlink:type="arc" />
      <link:label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:label="CLSN_InducementOptionGrantsMember_doc" xml:lang="en-US">Inducement Option Grants [Member]</link:label>
      <link:loc xlink:type="locator" xlink:href="clsn-20200630.xsd#CLSN_InvestorWarrantMember" xlink:label="CLSN_InvestorWarrantMember" />
      <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="CLSN_InvestorWarrantMember" xlink:to="CLSN_InvestorWarrantMember_doc" xlink:type="arc" />
      <link:label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:label="CLSN_InvestorWarrantMember_doc" xml:lang="en-US">Investor Warrants [Member]</link:label>
      <link:loc xlink:type="locator" xlink:href="clsn-20200630.xsd#CLSN_July2017DirectOfferingMember" xlink:label="CLSN_July2017DirectOfferingMember" />
      <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="CLSN_July2017DirectOfferingMember" xlink:to="CLSN_July2017DirectOfferingMember_doc" xlink:type="arc" />
      <link:label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:label="CLSN_July2017DirectOfferingMember_doc" xml:lang="en-US">Represents the information pertaining to the direct offering agreement on July 6, 2017.</link:label>
      <link:loc xlink:type="locator" xlink:href="clsn-20200630.xsd#CLSN_JuneTwoThousandAndSixrteenWarrantsMember" xlink:label="CLSN_JuneTwoThousandAndSixrteenWarrantsMember" />
      <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="CLSN_JuneTwoThousandAndSixrteenWarrantsMember" xlink:to="CLSN_JuneTwoThousandAndSixrteenWarrantsMember_doc" xlink:type="arc" />
      <link:label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:label="CLSN_JuneTwoThousandAndSixrteenWarrantsMember_doc" xml:lang="en-US">June 2016 Warrants [Member]</link:label>
      <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="CLSN_LawrencevilleNewJerseyMember" xlink:to="CLSN_LawrencevilleNewJerseyMember_doc" xlink:type="arc" />
      <link:label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:label="CLSN_LawrencevilleNewJerseyMember_doc" xml:lang="en-US">Lawrenceville New Jersey [Member]</link:label>
      <link:loc xlink:type="locator" xlink:href="clsn-20200630.xsd#CLSN_LeaseContractTypeAxis" xlink:label="CLSN_LeaseContractTypeAxis" />
      <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="CLSN_LeaseContractTypeAxis" xlink:to="CLSN_LeaseContractTypeAxis_doc" xlink:type="arc" />
      <link:label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:label="CLSN_LeaseContractTypeAxis_doc" xml:lang="en-US">Lease Contract Type [Axis]</link:label>
      <link:loc xlink:type="locator" xlink:href="clsn-20200630.xsd#CLSN_LicenseAgreementMember" xlink:label="CLSN_LicenseAgreementMember" />
      <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="CLSN_LicenseAgreementMember" xlink:to="CLSN_LicenseAgreementMember_doc" xlink:type="arc" />
      <link:label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:label="CLSN_LicenseAgreementMember_doc" xml:lang="en-US">License Agreement [Member]</link:label>
      <link:loc xlink:type="locator" xlink:href="clsn-20200630.xsd#CLSN_LoanAgreementMember" xlink:label="CLSN_LoanAgreementMember" />
      <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="CLSN_LoanAgreementMember" xlink:to="CLSN_LoanAgreementMember_doc" xlink:type="arc" />
      <link:label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:label="CLSN_LoanAgreementMember_doc" xml:lang="en-US">Loan Agreement [Member]</link:label>
      <link:loc xlink:type="locator" xlink:href="clsn-20200630.xsd#CLSN_May2015CommonStockOfferingMember" xlink:label="CLSN_May2015CommonStockOfferingMember" />
      <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="CLSN_May2015CommonStockOfferingMember" xlink:to="CLSN_May2015CommonStockOfferingMember_doc" xlink:type="arc" />
      <link:label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:label="CLSN_May2015CommonStockOfferingMember_doc" xml:lang="en-US">Represents a securities purchase agreement with certain investors into which the entity entered in May 2015.</link:label>
      <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="CLSN_NJMember" xlink:to="CLSN_NJMember_doc" xlink:type="arc" />
      <link:label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:label="CLSN_NJMember_doc" xml:lang="en-US">New Jersey [Member]</link:label>
      <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="CLSN_NetProceedsFromSaleOfNetOperatingLosses" xlink:to="CLSN_NetProceedsFromSaleOfNetOperatingLosses_doc" xlink:type="arc" />
      <link:label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:label="CLSN_NetProceedsFromSaleOfNetOperatingLosses_doc" xml:lang="en-US">Net proceeds from sale of net operating losses</link:label>
      <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="CLSN_NumberOfSharesOfCommonStockIssuableUponExerciseOfWarrantsAndEquityAwards" xlink:to="CLSN_NumberOfSharesOfCommonStockIssuableUponExerciseOfWarrantsAndEquityAwards_doc" xlink:type="arc" />
      <link:label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:label="CLSN_NumberOfSharesOfCommonStockIssuableUponExerciseOfWarrantsAndEquityAwards_doc" xml:lang="en-US">Represents the total number of Shares of common stock issuable upon exercise of warrants and equity awards.</link:label>
      <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="CLSN_NumberOfSharesOfCommonStockIssuedInCalculationBasicLossPerShare" xlink:to="CLSN_NumberOfSharesOfCommonStockIssuedInCalculationBasicLossPerShare_doc" xlink:type="arc" />
      <link:label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:label="CLSN_NumberOfSharesOfCommonStockIssuedInCalculationBasicLossPerShare_doc" xml:lang="en-US">Number of shares of common stock issued in calculation basic loss per share.</link:label>
      <link:loc xlink:type="locator" xlink:href="clsn-20200630.xsd#CLSN_October2017UnderwrittenOfferingMember" xlink:label="CLSN_October2017UnderwrittenOfferingMember" />
      <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="CLSN_October2017UnderwrittenOfferingMember" xlink:to="CLSN_October2017UnderwrittenOfferingMember_doc" xlink:type="arc" />
      <link:label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:label="CLSN_October2017UnderwrittenOfferingMember_doc" xml:lang="en-US">Represents the October 2017 Underwritten Offering.</link:label>
      <link:loc xlink:type="locator" xlink:href="clsn-20200630.xsd#CLSN_OperatingLeasesMember" xlink:label="CLSN_OperatingLeasesMember" />
      <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="CLSN_OperatingLeasesMember" xlink:to="CLSN_OperatingLeasesMember_doc" xlink:type="arc" />
      <link:label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:label="CLSN_OperatingLeasesMember_doc" xml:lang="en-US">Operating Leases [Member]</link:label>
      <link:loc xlink:type="locator" xlink:href="clsn-20200630.xsd#CLSN_OppenheimerAndCoIncMember" xlink:label="CLSN_OppenheimerAndCoIncMember" />
      <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="CLSN_OppenheimerAndCoIncMember" xlink:to="CLSN_OppenheimerAndCoIncMember_doc" xlink:type="arc" />
      <link:label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:label="CLSN_OppenheimerAndCoIncMember_doc" xml:lang="en-US">Oppenheimer &amp;amp;amp;amp;amp;amp;amp; Co. Inc. [Member]</link:label>
      <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="CLSN_OriginalWarrantsMember" xlink:to="CLSN_OriginalWarrantsMember_doc" xlink:type="arc" />
      <link:label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:label="CLSN_OriginalWarrantsMember_doc" xml:lang="en-US">Original Warrants [Member]</link:label>
      <link:loc xlink:type="locator" xlink:href="clsn-20200630.xsd#CLSN_OtherWarrantsMember" xlink:label="CLSN_OtherWarrantsMember" />
      <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="CLSN_OtherWarrantsMember" xlink:to="CLSN_OtherWarrantsMember_doc" xlink:type="arc" />
      <link:label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:label="CLSN_OtherWarrantsMember_doc" xml:lang="en-US">Other Warrant [Member]</link:label>
      <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="CLSN_OvarianCancerMember" xlink:to="CLSN_OvarianCancerMember_doc" xlink:type="arc" />
      <link:label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:label="CLSN_OvarianCancerMember_doc" xml:lang="en-US">Ovarian Cancer [Member]</link:label>
      <link:loc xlink:type="locator" xlink:href="clsn-20200630.xsd#CLSN_PreFundedSeriesBBWarrantMember" xlink:label="CLSN_PreFundedSeriesBBWarrantMember" />
      <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="CLSN_PreFundedSeriesBBWarrantMember" xlink:to="CLSN_PreFundedSeriesBBWarrantMember_doc" xlink:type="arc" />
      <link:label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:label="CLSN_PreFundedSeriesBBWarrantMember_doc" xml:lang="en-US">Information relating to Pre-Funded Series BB Warrant.</link:label>
      <link:loc xlink:type="locator" xlink:href="clsn-20200630.xsd#CLSN_PreFundedSeriesCCCWarrantsMember" xlink:label="CLSN_PreFundedSeriesCCCWarrantsMember" />
      <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="CLSN_PreFundedSeriesCCCWarrantsMember" xlink:to="CLSN_PreFundedSeriesCCCWarrantsMember_doc" xlink:type="arc" />
      <link:label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:label="CLSN_PreFundedSeriesCCCWarrantsMember_doc" xml:lang="en-US">Represents the information pertaining to the Pre-Funded Series CCC Warrants.</link:label>
      <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="CLSN_PrivateExchangeAgreementsMember" xlink:to="CLSN_PrivateExchangeAgreementsMember_doc" xlink:type="arc" />
      <link:label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:label="CLSN_PrivateExchangeAgreementsMember_doc" xml:lang="en-US">Private Exchange Agreements [Member]</link:label>
      <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="CLSN_PurchaseAgreementMember" xlink:to="CLSN_PurchaseAgreementMember_doc" xlink:type="arc" />
      <link:label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:label="CLSN_PurchaseAgreementMember_doc" xml:lang="en-US">Purchase Agreement [Member]</link:label>
      <link:loc xlink:type="locator" xlink:href="clsn-20200630.xsd#CLSN_RecognizedNonCashChargeMember" xlink:label="CLSN_RecognizedNonCashChargeMember" />
      <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="CLSN_RecognizedNonCashChargeMember" xlink:to="CLSN_RecognizedNonCashChargeMember_doc" xlink:type="arc" />
      <link:label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:label="CLSN_RecognizedNonCashChargeMember_doc" xml:lang="en-US">Recognized Non-cash Charge [Member]</link:label>
      <link:loc xlink:type="locator" xlink:href="clsn-20200630.xsd#CLSN_RecognizedNoncashBenefitMember" xlink:label="CLSN_RecognizedNoncashBenefitMember" />
      <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="CLSN_RecognizedNoncashBenefitMember" xlink:to="CLSN_RecognizedNoncashBenefitMember_doc" xlink:type="arc" />
      <link:label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:label="CLSN_RecognizedNoncashBenefitMember_doc" xml:lang="en-US">Recognized Non-cash Benefit [Member]</link:label>
      <link:loc xlink:type="locator" xlink:href="clsn-20200630.xsd#CLSN_ReductionInWarrantsMember" xlink:label="CLSN_ReductionInWarrantsMember" />
      <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="CLSN_ReductionInWarrantsMember" xlink:to="CLSN_ReductionInWarrantsMember_doc" xlink:type="arc" />
      <link:label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:label="CLSN_ReductionInWarrantsMember_doc" xml:lang="en-US">Reduction in Warrant [Member]</link:label>
      <link:loc xlink:type="locator" xlink:href="clsn-20200630.xsd#CLSN_RevenueRatablyThroughTwentyTwentyTwoMember" xlink:label="CLSN_RevenueRatablyThroughTwentyTwentyTwoMember" />
      <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="CLSN_RevenueRatablyThroughTwentyTwentyTwoMember" xlink:to="CLSN_RevenueRatablyThroughTwentyTwentyTwoMember_doc" xlink:type="arc" />
      <link:label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:label="CLSN_RevenueRatablyThroughTwentyTwentyTwoMember_doc" xml:lang="en-US">Revenue Ratably Through 2022 [Member]</link:label>
      <link:loc xlink:type="locator" xlink:href="clsn-20200630.xsd#CLSN_SecondLeaseAmendmentMember" xlink:label="CLSN_SecondLeaseAmendmentMember" />
      <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="CLSN_SecondLeaseAmendmentMember" xlink:to="CLSN_SecondLeaseAmendmentMember_doc" xlink:type="arc" />
      <link:label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:label="CLSN_SecondLeaseAmendmentMember_doc" xml:lang="en-US">2nd Lease Amendment [Member]</link:label>
      <link:loc xlink:type="locator" xlink:href="clsn-20200630.xsd#CLSN_SecondTrancheMember" xlink:label="CLSN_SecondTrancheMember" />
      <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="CLSN_SecondTrancheMember" xlink:to="CLSN_SecondTrancheMember_doc" xlink:type="arc" />
      <link:label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:label="CLSN_SecondTrancheMember_doc" xml:lang="en-US">Second Tranche [Member]</link:label>
      <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="CLSN_SecuritiesPurchaseAgreementMember" xlink:to="CLSN_SecuritiesPurchaseAgreementMember_doc" xlink:type="arc" />
      <link:label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:label="CLSN_SecuritiesPurchaseAgreementMember_doc" xml:lang="en-US">Securities Purchase Agreement [Member]</link:label>
      <link:loc xlink:type="locator" xlink:href="clsn-20200630.xsd#CLSN_SeriesAAAWarrantsMember" xlink:label="CLSN_SeriesAAAWarrantsMember" />
      <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="CLSN_SeriesAAAWarrantsMember" xlink:to="CLSN_SeriesAAAWarrantsMember_doc" xlink:type="arc" />
      <link:label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:label="CLSN_SeriesAAAWarrantsMember_doc" xml:lang="en-US">Represents the information pertaining to the Series AAA Warrants.</link:label>
      <link:loc xlink:type="locator" xlink:href="clsn-20200630.xsd#CLSN_SeriesAAWarrantMember" xlink:label="CLSN_SeriesAAWarrantMember" />
      <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="CLSN_SeriesAAWarrantMember" xlink:to="CLSN_SeriesAAWarrantMember_doc" xlink:type="arc" />
      <link:label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:label="CLSN_SeriesAAWarrantMember_doc" xml:lang="en-US">Information relating to Series AA warrants.</link:label>
      <link:loc xlink:type="locator" xlink:href="clsn-20200630.xsd#CLSN_SeriesBBBWarrantsMember" xlink:label="CLSN_SeriesBBBWarrantsMember" />
      <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="CLSN_SeriesBBBWarrantsMember" xlink:to="CLSN_SeriesBBBWarrantsMember_doc" xlink:type="arc" />
      <link:label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:label="CLSN_SeriesBBBWarrantsMember_doc" xml:lang="en-US">Represents the information pertaining to the Series BBB Warrants.</link:label>
      <link:loc xlink:type="locator" xlink:href="clsn-20200630.xsd#CLSN_SeriesDDDWarrantsMember" xlink:label="CLSN_SeriesDDDWarrantsMember" />
      <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="CLSN_SeriesDDDWarrantsMember" xlink:to="CLSN_SeriesDDDWarrantsMember_doc" xlink:type="arc" />
      <link:label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:label="CLSN_SeriesDDDWarrantsMember_doc" xml:lang="en-US">Represents the information pertaining to Series DDD Warrants.</link:label>
      <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="CLSN_ShelfRegistrationStatementAmount" xlink:to="CLSN_ShelfRegistrationStatementAmount_doc" xlink:type="arc" />
      <link:label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:label="CLSN_ShelfRegistrationStatementAmount_doc" xml:lang="en-US">Shelf Registration statement.</link:label>
      <link:loc xlink:type="locator" xlink:href="clsn-20200630.xsd#CLSN_SixtyMonthLeaseMember" xlink:label="CLSN_SixtyMonthLeaseMember" />
      <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="CLSN_SixtyMonthLeaseMember" xlink:to="CLSN_SixtyMonthLeaseMember_doc" xlink:type="arc" />
      <link:label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:label="CLSN_SixtyMonthLeaseMember_doc" xml:lang="en-US">60 Month Lease [Member]</link:label>
      <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="CLSN_TaxBenefitsOfEarningsBeforeDepreciationAndAmortization" xlink:to="CLSN_TaxBenefitsOfEarningsBeforeDepreciationAndAmortization_doc" xlink:type="arc" />
      <link:label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:label="CLSN_TaxBenefitsOfEarningsBeforeDepreciationAndAmortization_doc" xml:lang="en-US">Tax benefits of EDA</link:label>
      <link:loc xlink:type="locator" xlink:href="clsn-20200630.xsd#CLSN_TaxReformActMember" xlink:label="CLSN_TaxReformActMember" />
      <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="CLSN_TaxReformActMember" xlink:to="CLSN_TaxReformActMember_doc" xlink:type="arc" />
      <link:label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:label="CLSN_TaxReformActMember_doc" xml:lang="en-US">Tax Reform Act [Member]</link:label>
      <link:loc xlink:type="locator" xlink:href="clsn-20200630.xsd#CLSN_ThreeNewEmployeesMember" xlink:label="CLSN_ThreeNewEmployeesMember" />
      <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="CLSN_ThreeNewEmployeesMember" xlink:to="CLSN_ThreeNewEmployeesMember_doc" xlink:type="arc" />
      <link:label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:label="CLSN_ThreeNewEmployeesMember_doc" xml:lang="en-US">Three New Employees [Member]</link:label>
      <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="CLSN_TwoThousandAndEighteenStockIncentivePlanMember" xlink:to="CLSN_TwoThousandAndEighteenStockIncentivePlanMember_doc" xlink:type="arc" />
      <link:label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:label="CLSN_TwoThousandAndEighteenStockIncentivePlanMember_doc" xml:lang="en-US">2018 Stock Incentive Plan [Member]</link:label>
      <link:loc xlink:type="locator" xlink:href="clsn-20200630.xsd#CLSN_TwoThousandAndSevenStockIncentivePlanMember" xlink:label="CLSN_TwoThousandAndSevenStockIncentivePlanMember" />
      <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="CLSN_TwoThousandAndSevenStockIncentivePlanMember" xlink:to="CLSN_TwoThousandAndSevenStockIncentivePlanMember_doc" xlink:type="arc" />
      <link:label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:label="CLSN_TwoThousandAndSevenStockIncentivePlanMember_doc" xml:lang="en-US">2007 Stock Incentive Plan [Member]</link:label>
      <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="CLSN_TwoThousandEighteenAspirePurchaseAgreementsMember" xlink:to="CLSN_TwoThousandEighteenAspirePurchaseAgreementsMember_doc" xlink:type="arc" />
      <link:label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:label="CLSN_TwoThousandEighteenAspirePurchaseAgreementsMember_doc" xml:lang="en-US">2018 Aspire Purchase Agreements [Member]</link:label>
      <link:loc xlink:type="locator" xlink:href="clsn-20200630.xsd#CLSN_TwoThousandFifteenWarrantsMember" xlink:label="CLSN_TwoThousandFifteenWarrantsMember" />
      <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="CLSN_TwoThousandFifteenWarrantsMember" xlink:to="CLSN_TwoThousandFifteenWarrantsMember_doc" xlink:type="arc" />
      <link:label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:label="CLSN_TwoThousandFifteenWarrantsMember_doc" xml:lang="en-US">Represents the information pertaining to the 2015 Warrants.</link:label>
      <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="CLSN_TwoThousandNineteenAspirePurchaseAgreementsMember" xlink:to="CLSN_TwoThousandNineteenAspirePurchaseAgreementsMember_doc" xlink:type="arc" />
      <link:label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:label="CLSN_TwoThousandNineteenAspirePurchaseAgreementsMember_doc" xml:lang="en-US">2019 Aspire Purchase Agreements [Member]</link:label>
      <link:loc xlink:type="locator" xlink:href="clsn-20200630.xsd#CLSN_TwoThousandThirteenWarrants2014WarrantsAndJune2016WarrantsMember" xlink:label="CLSN_TwoThousandThirteenWarrants2014WarrantsAndJune2016WarrantsMember" />
      <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="CLSN_TwoThousandThirteenWarrants2014WarrantsAndJune2016WarrantsMember" xlink:to="CLSN_TwoThousandThirteenWarrants2014WarrantsAndJune2016WarrantsMember_doc" xlink:type="arc" />
      <link:label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:label="CLSN_TwoThousandThirteenWarrants2014WarrantsAndJune2016WarrantsMember_doc" xml:lang="en-US">Represents the information pertaining to the 2013 Warrants, 2014 Warrants, and June 2016 Warrants.</link:label>
      <link:loc xlink:type="locator" xlink:href="clsn-20200630.xsd#CLSN_USFederalAndStateTaxMember" xlink:label="CLSN_USFederalAndStateTaxMember" />
      <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="CLSN_USFederalAndStateTaxMember" xlink:to="CLSN_USFederalAndStateTaxMember_doc" xlink:type="arc" />
      <link:label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:label="CLSN_USFederalAndStateTaxMember_doc" xml:lang="en-US">U.S. Federal and State Tax [Member]</link:label>
      <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="CLSN_UnderwritingAgreementMember" xlink:to="CLSN_UnderwritingAgreementMember_doc" xlink:type="arc" />
      <link:label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:label="CLSN_UnderwritingAgreementMember_doc" xml:lang="en-US">Underwriting Agreement [Member]</link:label>
      <link:loc xlink:type="locator" xlink:href="clsn-20200630.xsd#CLSN_WarrantExchangeAgreementsMember" xlink:label="CLSN_WarrantExchangeAgreementsMember" />
      <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="CLSN_WarrantExchangeAgreementsMember" xlink:to="CLSN_WarrantExchangeAgreementsMember_doc" xlink:type="arc" />
      <link:label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:label="CLSN_WarrantExchangeAgreementsMember_doc" xml:lang="en-US">Warrant Exchange Agreements [Member]</link:label>
      <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="CLSN_SummaryOfStockOptionAndRestrictedStockAwardsTableTextBlock" xlink:to="CLSN_SummaryOfStockOptionAndRestrictedStockAwardsTableTextBlock_doc" xlink:type="arc" />
      <link:label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:label="CLSN_SummaryOfStockOptionAndRestrictedStockAwardsTableTextBlock_doc" xml:lang="en-US">Summary of stock option and restricted stock awards [Table text block]</link:label>
      <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="CLSN_RNADeliverySystemMember" xlink:to="CLSN_RNADeliverySystemMember_doc" xlink:type="arc" />
      <link:label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:label="CLSN_RNADeliverySystemMember_doc" xml:lang="en-US">RNA Delivery System [Member]</link:label>
      <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="CLSN_LongTermDebtMaturitiesRepaymentsOfPrincipalYearFourAndThereAfter" xlink:to="CLSN_LongTermDebtMaturitiesRepaymentsOfPrincipalYearFourAndThereAfter_doc" xlink:type="arc" />
      <link:label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:label="CLSN_LongTermDebtMaturitiesRepaymentsOfPrincipalYearFourAndThereAfter_doc" xml:lang="en-US">2023 and thereafter.</link:label>
      <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="CLSN_TwoThousandSevenStockIncentivePlanMember" xlink:to="CLSN_TwoThousandSevenStockIncentivePlanMember_doc" xlink:type="arc" />
      <link:label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:label="CLSN_TwoThousandSevenStockIncentivePlanMember_doc" xml:lang="en-US">2007 Stock Incentive Plan [Member]</link:label>
      <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="CLSN_StockOptionsStrikePriceDescription" xlink:to="CLSN_StockOptionsStrikePriceDescription_doc" xlink:type="arc" />
      <link:label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:label="CLSN_StockOptionsStrikePriceDescription_doc" xml:lang="en-US">Stock options, strike price description.</link:label>
      <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="CLSN_TwoNewEmployeesMember" xlink:to="CLSN_TwoNewEmployeesMember_doc" xlink:type="arc" />
      <link:label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:label="CLSN_TwoNewEmployeesMember_doc" xml:lang="en-US">Two New Employees [Member]</link:label>
      <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="CLSN_GrantedUnderTwoThousandEighteenPlanAndTwoThousandSevenPlanMember" xlink:to="CLSN_GrantedUnderTwoThousandEighteenPlanAndTwoThousandSevenPlanMember_doc" xlink:type="arc" />
      <link:label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:label="CLSN_GrantedUnderTwoThousandEighteenPlanAndTwoThousandSevenPlanMember_doc" xml:lang="en-US">Granted Under 2018 Plan and 2007 Plan [Member]</link:label>
      <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="CLSN_TwoThousandAndEighteenPlanMember" xlink:to="CLSN_TwoThousandAndEighteenPlanMember_doc" xlink:type="arc" />
      <link:label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:label="CLSN_TwoThousandAndEighteenPlanMember_doc" xml:lang="en-US">2018 Plan [Member]</link:label>
      <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="CLSN_EmployeeStockOptionAndRestrictedStockAwardsMember" xlink:to="CLSN_EmployeeStockOptionAndRestrictedStockAwardsMember_doc" xlink:type="arc" />
      <link:label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:label="CLSN_EmployeeStockOptionAndRestrictedStockAwardsMember_doc" xml:lang="en-US">Stock Options and Restricted Stock Awards [Member]</link:label>
      <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="CLSN_NonVestedStockBasedCompensationArrangementsMember" xlink:to="CLSN_NonVestedStockBasedCompensationArrangementsMember_doc" xlink:type="arc" />
      <link:label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:label="CLSN_NonVestedStockBasedCompensationArrangementsMember_doc" xml:lang="en-US">Non-Vested Stock-Based Compensation Arrangements [Member]</link:label>
      <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="CLSN_TwoThousandNineteenBonusProgramMember" xlink:to="CLSN_TwoThousandNineteenBonusProgramMember_doc" xlink:type="arc" />
      <link:label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:label="CLSN_TwoThousandNineteenBonusProgramMember_doc" xml:lang="en-US">2019 Bonus Program [Member]</link:label>
      <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="CLSN_AnnualBonusAwardsPercentage" xlink:to="CLSN_AnnualBonusAwardsPercentage_doc" xlink:type="arc" />
      <link:label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:label="CLSN_AnnualBonusAwardsPercentage_doc" xml:lang="en-US">Annual bonus awards, percentage</link:label>
      <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="CLSN_PaymentOptionOneMember" xlink:to="CLSN_PaymentOptionOneMember_doc" xlink:type="arc" />
      <link:label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:label="CLSN_PaymentOptionOneMember_doc" xml:lang="en-US">Payment Option One [Member]</link:label>
      <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="CLSN_PaymentOptionTwoMember" xlink:to="CLSN_PaymentOptionTwoMember_doc" xlink:type="arc" />
      <link:label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:label="CLSN_PaymentOptionTwoMember_doc" xml:lang="en-US">Payment Option Two [Member]</link:label>
      <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="CLSN_AprilPaycheckProtectionProgramLoanMember" xlink:to="CLSN_AprilPaycheckProtectionProgramLoanMember_doc" xlink:type="arc" />
      <link:label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:label="CLSN_AprilPaycheckProtectionProgramLoanMember_doc" xml:lang="en-US">April PPP Loan [Member]</link:label>
      <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="CLSN_SiliconValleyBankMember" xlink:to="CLSN_SiliconValleyBankMember_doc" xlink:type="arc" />
      <link:label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:label="CLSN_SiliconValleyBankMember_doc" xml:lang="en-US">Silicon Valley Bank [Member]</link:label>
      <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="CLSN_PaycheckProtectionProgramLoansMember" xlink:to="CLSN_PaycheckProtectionProgramLoansMember_doc" xlink:type="arc" />
      <link:label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:label="CLSN_PaycheckProtectionProgramLoansMember_doc" xml:lang="en-US">PPP Loans [Member]</link:label>
      <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="CLSN_MayPaycheckProtectionProgramLoanMember" xlink:to="CLSN_MayPaycheckProtectionProgramLoanMember_doc" xlink:type="arc" />
      <link:label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:label="CLSN_MayPaycheckProtectionProgramLoanMember_doc" xml:lang="en-US">May PPP Loan [Member]</link:label>
      <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="CLSN_UnderwrittenOfferingMember" xlink:to="CLSN_UnderwrittenOfferingMember_doc" xlink:type="arc" />
      <link:label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:label="CLSN_UnderwrittenOfferingMember_doc" xml:lang="en-US">Underwritten Offering [Member]</link:label>
      <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="CLSN_UnderwritingDiscountPricePerShare" xlink:to="CLSN_UnderwritingDiscountPricePerShare_doc" xlink:type="arc" />
      <link:label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:label="CLSN_UnderwritingDiscountPricePerShare_doc" xml:lang="en-US">Underwriting discount price per share.</link:label>
      <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="CLSN_PercentageOfUnderwritingDiscountOnPublicOfferingPrice" xlink:to="CLSN_PercentageOfUnderwritingDiscountOnPublicOfferingPrice_doc" xlink:type="arc" />
      <link:label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:label="CLSN_PercentageOfUnderwritingDiscountOnPublicOfferingPrice_doc" xml:lang="en-US">Percentage of underwriting discount on public offering price.</link:label>
      <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="CLSN_ShareBasedCompensationArrangementsByShareBasedPaymentAwardOptionsExerciseInPeriodWeightedAverageExercisePrice" xlink:to="CLSN_ShareBasedCompensationArrangementsByShareBasedPaymentAwardOptionsExerciseInPeriodWeightedAverageExercisePrice_doc" xlink:type="arc" />
      <link:label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:label="CLSN_ShareBasedCompensationArrangementsByShareBasedPaymentAwardOptionsExerciseInPeriodWeightedAverageExercisePrice_doc" xml:lang="en-US">Weighted Average Exercise Price, Options exercised.</link:label>
      <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="CLSN_FiniteLivedIntangibleAssetsAmortizationExpenseYearTwoAndAfter" xlink:to="CLSN_FiniteLivedIntangibleAssetsAmortizationExpenseYearTwoAndAfter_doc" xlink:type="arc" />
      <link:label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:label="CLSN_FiniteLivedIntangibleAssetsAmortizationExpenseYearTwoAndAfter_doc" xml:lang="en-US">Finite-lived intangible asset, expected amortization, year two, and after.</link:label>
      <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="CLSN_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsExerciseInPeriod" xlink:to="CLSN_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsExerciseInPeriod_doc" xlink:type="arc" />
      <link:label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:label="CLSN_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsExerciseInPeriod_doc" xml:lang="en-US">Number Outstanding, Non-vested stock awards outstanding, Options exercised.</link:label>
      <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="CLSN_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsExerciseInPeriodWeightedAverageGrantDateFairValue" xlink:to="CLSN_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsExerciseInPeriodWeightedAverageGrantDateFairValue_doc" xlink:type="arc" />
      <link:label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:label="CLSN_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsExerciseInPeriodWeightedAverageGrantDateFairValue_doc" xml:lang="en-US">Weighted Average Grant Date Fair Value, Non-vested stock awards, Options exercised.</link:label>
      <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="CLSN_GainLossFromChangeInEarnoutMilestoneLiability" xlink:to="CLSN_GainLossFromChangeInEarnoutMilestoneLiability_doc" xlink:type="arc" />
      <link:label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:label="CLSN_GainLossFromChangeInEarnoutMilestoneLiability_doc" xml:lang="en-US">Gain (loss) from change in valuation of earn-out milestone liability.</link:label>
      <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="CLSN_FairValueOfWarrantsIssuedInConnectionWithAmendmentToModifyEarnoutMilestonePayments" xlink:to="CLSN_FairValueOfWarrantsIssuedInConnectionWithAmendmentToModifyEarnoutMilestonePayments_doc" xlink:type="arc" />
      <link:label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:label="CLSN_FairValueOfWarrantsIssuedInConnectionWithAmendmentToModifyEarnoutMilestonePayments_doc" xml:lang="en-US">Fair value of warrants issued in connection with amendment to modify GEN-1 earn-out milestone payments.</link:label>
      <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="CLSN_GainLossFromValuationOfEarnoutMilestoneLiability" xlink:to="CLSN_GainLossFromValuationOfEarnoutMilestoneLiability_doc" xlink:type="arc" />
      <link:label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:label="CLSN_GainLossFromValuationOfEarnoutMilestoneLiability_doc" xml:lang="en-US">The amount recognized in earnings related to the change in fair value during the period of milestone liability.</link:label>
      <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="CLSN_SharesIssuedInExchangeForServices" xlink:to="CLSN_SharesIssuedInExchangeForServices_doc" xlink:type="arc" />
      <link:label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:label="CLSN_SharesIssuedInExchangeForServices_doc" xml:lang="en-US">Shares issued in exchange for services.</link:label>
      <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="CLSN_AmortizationOfDeferredFinanceChargesAndDebtDiscountAssociatedWithNotePayable" xlink:to="CLSN_AmortizationOfDeferredFinanceChargesAndDebtDiscountAssociatedWithNotePayable_doc" xlink:type="arc" />
      <link:label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:label="CLSN_AmortizationOfDeferredFinanceChargesAndDebtDiscountAssociatedWithNotePayable_doc" xml:lang="en-US">Amortization of deferred finance charges and debt discount associated with note payable.</link:label>
      <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="CLSN_FairValueOfWarrantsIssuedInConnectionWithAmendmentToModifyRelatedEarnoutMilestonePayments" xlink:to="CLSN_FairValueOfWarrantsIssuedInConnectionWithAmendmentToModifyRelatedEarnoutMilestonePayments_doc" xlink:type="arc" />
      <link:label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:label="CLSN_FairValueOfWarrantsIssuedInConnectionWithAmendmentToModifyRelatedEarnoutMilestonePayments_doc" xml:lang="en-US">Fair value of warrants issued in connection with amendment to modify the related earn-out milestone payments.</link:label>
      <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="CLSN_RightOfUseAssetsObtainedInExchangeForLeaseLiabilitiesAbstract" xlink:to="CLSN_RightOfUseAssetsObtainedInExchangeForLeaseLiabilitiesAbstract_doc" xlink:type="arc" />
      <link:label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:label="CLSN_RightOfUseAssetsObtainedInExchangeForLeaseLiabilitiesAbstract_doc" xml:lang="en-US">Right of use assets obtained in exchange for lease liabilities.</link:label>
      <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="CLSN_RightOfUseAssetsObtainedInExchangeForLease" xlink:to="CLSN_RightOfUseAssetsObtainedInExchangeForLease_doc" xlink:type="arc" />
      <link:label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:label="CLSN_RightOfUseAssetsObtainedInExchangeForLease_doc" xml:lang="en-US">Right of use assets, obtained in exchange for lease liabilities.</link:label>
      <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="CLSN_SaleOfEquityThroughEquityFinancingFacilities" xlink:to="CLSN_SaleOfEquityThroughEquityFinancingFacilities_doc" xlink:type="arc" />
      <link:label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:label="CLSN_SaleOfEquityThroughEquityFinancingFacilities_doc" xml:lang="en-US">Sale of equity through financing facilities.</link:label>
      <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="CLSN_SaleOfEquityThroughEquityFinancingFacilitiesShares" xlink:to="CLSN_SaleOfEquityThroughEquityFinancingFacilitiesShares_doc" xlink:type="arc" />
      <link:label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:label="CLSN_SaleOfEquityThroughEquityFinancingFacilitiesShares_doc" xml:lang="en-US">Sale of equity through financing facilities, shares.</link:label>
      <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="CLSN_EarnoutMilestoneLiabilityDisclosureTextBlock" xlink:to="CLSN_EarnoutMilestoneLiabilityDisclosureTextBlock_doc" xlink:type="arc" />
      <link:label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:label="CLSN_EarnoutMilestoneLiabilityDisclosureTextBlock_doc" xml:lang="en-US">The disclosure related to earn-out milestone liabilities.</link:label>
      <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="CLSN_WarrantsTextBlock" xlink:to="CLSN_WarrantsTextBlock_doc" xlink:type="arc" />
      <link:label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:label="CLSN_WarrantsTextBlock_doc" xml:lang="en-US">Warrants [Text Block]</link:label>
      <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="CLSN_LicensingTransactionTextBlock" xlink:to="CLSN_LicensingTransactionTextBlock_doc" xlink:type="arc" />
      <link:label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:label="CLSN_LicensingTransactionTextBlock_doc" xml:lang="en-US">The entire disclosure for a contractual arrangement, in which the Company gave another party an exclusive license.</link:label>
      <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="CLSN_ScheduleOfChangesInEarnOutMilestoneLiabilitiesTableTextBlock" xlink:to="CLSN_ScheduleOfChangesInEarnOutMilestoneLiabilitiesTableTextBlock_doc" xlink:type="arc" />
      <link:label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:label="CLSN_ScheduleOfChangesInEarnOutMilestoneLiabilitiesTableTextBlock_doc" xml:lang="en-US">The disclosure of transactions regarding the changes in earn-out liabilities during the period.</link:label>
      <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="CLSN_ScheduleOfRiskadjustmentAssessmentTableTextBlock" xlink:to="CLSN_ScheduleOfRiskadjustmentAssessmentTableTextBlock_doc" xlink:type="arc" />
      <link:label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:label="CLSN_ScheduleOfRiskadjustmentAssessmentTableTextBlock_doc" xml:lang="en-US">Schedule of risk-adjustment assessment [Table text block]</link:label>
      <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="CLSN_ScheduleOfWeightedAverageRemainingContractualTermsTableTextBlock" xlink:to="CLSN_ScheduleOfWeightedAverageRemainingContractualTermsTableTextBlock_doc" xlink:type="arc" />
      <link:label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:label="CLSN_ScheduleOfWeightedAverageRemainingContractualTermsTableTextBlock_doc" xml:lang="en-US">Tabular disclosure of weighted average remaining contractual terms.</link:label>
      <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="CLSN_EarnoutMilestoneLiability1" xlink:to="CLSN_EarnoutMilestoneLiability1_doc" xlink:type="arc" />
      <link:label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:label="CLSN_EarnoutMilestoneLiability1_doc" xml:lang="en-US">Earnout milestone liability.</link:label>
      <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="CLSN_GainOnNoncashBenefit" xlink:to="CLSN_GainOnNoncashBenefit_doc" xlink:type="arc" />
      <link:label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:label="CLSN_GainOnNoncashBenefit_doc" xml:lang="en-US">Gain on non-cash benefit.</link:label>
      <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="CLSN_RiskAdjustedAssessmentOfEachMilestone" xlink:to="CLSN_RiskAdjustedAssessmentOfEachMilestone_doc" xlink:type="arc" />
      <link:label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:label="CLSN_RiskAdjustedAssessmentOfEachMilestone_doc" xml:lang="en-US">The percentage of risk-adjusted assessment of each milestone.</link:label>
      <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="CLSN_GainLossFromChangeInFairValueOfEarnOutMilestoneLiability" xlink:to="CLSN_GainLossFromChangeInFairValueOfEarnOutMilestoneLiability_doc" xlink:type="arc" />
      <link:label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:label="CLSN_GainLossFromChangeInFairValueOfEarnOutMilestoneLiability_doc" xml:lang="en-US">The amount of gain (loss) from the change in the fair value of earn-out milestone liability.</link:label>
      <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="CLSN_EarnoutMilestoneLiability" xlink:to="CLSN_EarnoutMilestoneLiability_doc" xlink:type="arc" />
      <link:label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:label="CLSN_EarnoutMilestoneLiability_doc" xml:lang="en-US">Earn-out liabilities, beginning balance.</link:label>
      <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="CLSN_RiskadjustmentAssessmentOfAchievingEachMilestone" xlink:to="CLSN_RiskadjustmentAssessmentOfAchievingEachMilestone_doc" xlink:type="arc" />
      <link:label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:label="CLSN_RiskadjustmentAssessmentOfAchievingEachMilestone_doc" xml:lang="en-US">Risk-adjustment assessment of achieving each milestone.</link:label>
      <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="CLSN_DiscountRateOnMileStoneLiabilities" xlink:to="CLSN_DiscountRateOnMileStoneLiabilities_doc" xlink:type="arc" />
      <link:label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:label="CLSN_DiscountRateOnMileStoneLiabilities_doc" xml:lang="en-US">Discount rate on milestone liabilites.</link:label>
      <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="CLSN_EstimatedTimeToAchieveMileStone" xlink:to="CLSN_EstimatedTimeToAchieveMileStone_doc" xlink:type="arc" />
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      <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="CLSN_LesseeOperatingLeaseLiabilityPaymentsDueYearFourAndThereAfter" xlink:to="CLSN_LesseeOperatingLeaseLiabilityPaymentsDueYearFourAndThereAfter_doc" xlink:type="arc" />
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      <link:label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:label="CLSN_DeferredRevenueAmortizationPeriod_doc" xml:lang="en-US">The amortization period for deferred revenue.</link:label>
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      <link:label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:label="CLSN_IssuanceOfCommonStockInLieuOfCashBonus_doc" xml:lang="en-US">Issuance of common stock in lieu of cash bonus.</link:label>
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      <link:labelArc xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="CLSN_AspirePurchaseAgreementsMember" xlink:to="CLSN_AspirePurchaseAgreementsMember_3_lbl" xlink:type="arc" />
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      <link:label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_NonoperatingIncomeExpense_2_lbl" xml:lang="en-US">Nonoperating Income (Expense)</link:label>
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      <link:label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_ContractWithCustomerLiabilityRevenueRecognized_2_lbl" xml:lang="en-US">Contract with Customer, Liability, Revenue Recognized</link:label>
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