Imunon (IMNN) 10-K 19 Mar 21 2020 FY Annual report Financial data

Document and Entity Information

Document and Entity Information - USD ($)	12 Months Ended
	Dec. 31, 2020	Mar. 18, 2021	Jun. 30, 2020
Cover [Abstract]
Entity Registrant Name	Celsion CORP
Entity Central Index Key	0000749647
Document Type	10-K
Document Period End Date	Dec. 31, 2020
Amendment Flag	false
Current Fiscal Year End Date	--12-31
Entity Well-known Seasoned Issuer	No
Entity Voluntary Filer	No
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Entity Filer Category	Non-accelerated Filer
Entity Small Business Flag	true
Entity Emerging Growth Company	false
Entity Shell Company	false
Entity Public Float			$ 121,800,000
Entity Common Stock, Shares Outstanding		75,011,774
Document Fiscal Period Focus	FY
Document Fiscal Year Focus	2020

Consolidated Balance Sheets

Consolidated Balance Sheets - USD ($)	Dec. 31, 2020	Dec. 31, 2019
Current assets:
Cash and cash equivalents	$ 17,164,177	$ 6,875,273
Investment in debt securities - available for sale, at fair value		7,985,886
Accrued interest receivable on investment securities		21,369
Advances and deposits on clinical programs and other current assets	1,660,695	1,352,670
Total current assets	18,824,872	16,235,198
Property and equipment (at cost, less accumulated depreciation and amortization)	294,551	405,363
Other assets:
Deferred income tax asset	1,845,823	1,819,324
In-process research and development, net	13,366,234	15,736,491
Goodwill	1,976,101	1,976,101
Operating lease right-of-use assets, net	1,047,336	1,431,640
Other intangible assets, net	113,660	340,976
Deposits and other assets	58,761	333,274
Total other assets	18,407,915	21,637,806
Total assets	37,527,338	38,278,367
Current liabilities:
Accounts payable - trade	2,244,847	2,862,949
Other accrued liabilities	2,458,532	2,303,547
Notes payable - current portion, net of deferred financing costs	1,116,663	1,840,228
Operating lease liability - current portion	433,413	387,733
Deferred revenue - current portion	500,000	500,000
Total current liabilities	6,753,455	7,894,457
Earn-out milestone liability	7,018,000	5,717,709
Notes payable - non-current portion, net of deferred financing costs	3,934,497	7,963,449
Operating lease liability - non-current portion	710,305	1,143,717
Deferred revenue - non-current portion	500,000	1,000,000
Total liabilities	18,916,257	23,719,332
Commitments and contingencies
Stockholders' equity:
Preferred Stock - $0.01 par value (100,000 shares authorized, and no shares issued or outstanding at December 31, 2020 and 2019)
Common stock - $0.01 par value (112,500,000 shares authorized; 40,701,356 and 23,256,152 shares issued at December 31, 2020 and 2019, respectively, and 40,701,022 and 23,255,818 shares outstanding at December 31, 2020 and 2019, respectively)	407,014	232,562
Additional paid-in capital	330,289,596	304,885,663
Accumulated other comprehensive gain		42,778
Accumulated deficit	(312,000,341)	(290,516,780)
Total stockholders' equity before treasury stock	18,696,269	14,644,223
Treasury stock, at cost (334 shares at December 31, 2020 and 2019)	(85,188)	(85,188)
Total stockholders' equity	18,611,081	14,559,035
Total liabilities and stockholders' equity	$ 37,527,338	$ 38,278,367

Consolidated Balance Sheets (Pa

Consolidated Balance Sheets (Parenthetical) - $ / shares	Dec. 31, 2020	Dec. 31, 2019
Statement of Financial Position [Abstract]
Preferred stock, par value	$ 0.01	$ 0.01
Preferred stock, shares authorized	100,000	100,000
Preferred stock, shares issued
Preferred stock, shares outstanding
Common stock, par value	$ 0.01	$ 0.01
Common stock, shares authorized	112,500,000	112,500,000
Common stock, shares issued	40,701,356	23,256,152
Common stock, shares outstanding	40,701,022	23,255,818
Treasury stock, shares	334	334

Consolidated Statements of Oper

Consolidated Statements of Operations - USD ($)	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Income Statement [Abstract]
Technology development and licensing revenue	$ 500,000	$ 500,000
Operating expenses:
Research and development	11,344,819	13,065,309
General and administrative	7,641,593	8,000,164
Total operating expenses	18,986,412	21,065,473
Loss from operations	(18,486,412)	(20,565,473)
Other income (expense):
(Loss) gain from change in earn-out milestone liability	(1,300,291)	3,189,955
Fair value of warrants issued in connection with amendment to modify GEN-1 earn-out milestone payments		(400,000)
Impairment of in-process research and development	(2,370,257)
Investment income, net	119,907	500,882
Interest expense	(1,292,338)	(1,393,400)
Other income	7	29
Total other (expense) income	(4,842,972)	1,897,466
Loss before income tax benefit	(23,329,384)	(18,668,007)
Income tax benefit	1,845,823	1,816,474
Net loss	$ (21,483,561)	$ (16,851,533)
Net loss per common share - basic and diluted	$ (0.67)	$ (0.77)
Weighted average common shares outstanding - basic and diluted	31,961,248	21,832,932

Consolidated Statements of Comp

Consolidated Statements of Comprehensive Loss - USD ($)	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Statement of Comprehensive Income [Abstract]
Net loss	$ (21,483,561)	$ (16,851,533)
Changes in:
Realized (gain) on investment securities recognized in investment income, net	(53,354)	(57,895)
Unrealized gain on investment securities	10,576	70,801
Other comprehensive (loss) income	(42,778)	12,906
Comprehensive loss	$ (21,526,339)	$ (16,838,627)

Consolidated Statements of Cash

Consolidated Statements of Cash Flows - USD ($)	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Cash flows from operating activities:
Net loss	$ (21,483,561)	$ (16,851,533)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation and amortization	741,524	721,665
Change in fair value of earn-out milestone liability	1,300,291	(3,189,955)
Fair value of warrants issued in connection with amendment to modify the GEN-1 earn-out milestone payments		400,000
Fair value of warrants issued in exchange for services	44,798
Stock-based compensation	1,851,391	2,286,388
Shares issued upon vesting of stock awards		5,350
Change in deferred income tax asset	(26,499)	(1,819,324)
Impairment of in-process research and development	2,370,257
Amortization of deferred finance charges and debt discount associated with note payable	447,483	386,640
Net changes in:
Accrued interest receivable on investment securities	21,369	46,940
Advances and deposits on clinical programs and other current assets	(308,025)	(901,377)
Other assets	274,513	(74,341)
Accounts payable - trade	(618,102)	(157,689)
Deferred revenue	(500,000)	(500,000)
Other accrued liabilities	265,885	(611,746)
Net cash used in operating activities	(15,618,676)	(20,258,982)
Cash flows from investing activities:
Purchases of investment in debt securities	(9,956,892)	(23,829,982)
Proceeds from sale and maturity of investment in debt securities	17,900,000	30,115,000
Purchases of property and equipment	(19,092)	(349,158)
Net cash provided by investing activities	7,924,016	5,935,860
Cash flows from financing activities:
Proceeds from issuance of common stock equity, net of issuance costs	22,811,669	7,844,852
Proceeds from issuance of common stock upon exercise of stock options	371,895
Payments on notes payable including end-of-term fees	(5,200,000)
Proceeds from Paycheck Protection Program ("PPP") loans	1,324,750
Repayments on PPP loans	(1,324,750)
Net cash provided by financing activities	17,983,564	7,844,852
Increase (decrease) in cash and cash equivalents	10,288,904	(6,478,270)
Cash and cash equivalents at beginning of year	6,875,273	13,353,543
Cash and cash equivalents at end of year	17,164,177	6,875,273
Cash (paid for) received from:
Interest	(844,278)	(1,006,760)
Cash paid for amounts included in measurement of lease liabilities:
Operating cash flows from lease payments	525,809	485,848
Non-cash financing and investing activities
Common stock issued to settle accrued bonuses	498,632
Fair value of warrants issued in connection with the debt facility, net of cancelled warrants	81,102
Realized and unrealized (gains) and losses, net, on investment in debt securities	$ (42,778)	$ 12,906

Consolidated Statements of Chan

Consolidated Statements of Changes in Stockholders' Equity - USD ($)	Common Stock Outstanding [Member]	Additional Paid-In Capital [Member]	Treasury Stock [Member]	Accumulated Other Comprehensive Income [Member]	Accumulated Deficit [Member]	Total
Balance at Dec. 31, 2018	$ 188,322	$ 294,393,313	$ (85,188)	$ 29,872	$ (273,665,247)	$ 20,861,072
Balance, shares at Dec. 31, 2018	18,831,834		334
Net loss					(16,851,533)	(16,851,533)
Sale of equity through equity financing facilities	$ 43,860	7,800,992				7,844,852
Sale of equity through equity financing facilities, shares	4,385,984
Common stock warrants issued in connection with amendment to modify GEN-1 earn-out milestone payments		400,000				400,000
Issuance of restricted stock	$ 380	4,970				5,350
Issuance of restricted stock, shares	38,000
Realized and unrealized gains and losses, net, on investment securities				12,906		12,906
Stock-based compensation expense		2,286,388				2,286,388
Balance at Dec. 31, 2019	$ 232,562	304,885,663	$ (85,188)	42,778	(290,516,780)	14,559,035
Balance, shares at Dec. 31, 2019	23,255,818		334
Net loss					(21,483,561)	(21,483,561)
Sale of equity through equity financing facilities	$ 166,741	22,644,928				22,811,669
Sale of equity through equity financing facilities, shares	16,674,225
Issuance of restricted stock
Issuance of common stock upon exercise of options and vesting of stock awards	$ 1,439	370,456				371,895
Issuance of common stock upon exercise of options and vesting of stock awards, shares	143,864
Issuance of common stock upon exercise of common stock warrants	$ 1,973	(1,973)
Issuance of common stock upon exercise of common stock warrants,shares	197,260
Common stock issued to settle accrued bonuses	$ 4,299	494,333				498,632
Common stock issued to settle accrued bonuses, shares	429,855
Common stock warrants issued in exchange for services		44,798				44,798
Realized and unrealized gains and losses, net, on investment securities				(42,778)		(42,778)
Stock-based compensation expense		1,851,391				1,851,391
Balance at Dec. 31, 2020	$ 407,014	$ 330,289,596	$ (85,188)		$ (312,000,341)	$ 18,611,081
Balance, shares at Dec. 31, 2020	40,701,022		334

Summary of Significant Accounti

Summary of Significant Accounting Policies	12 Months Ended
	Dec. 31, 2020
Accounting Policies [Abstract]
Summary of Significant Accounting Policies	1. SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES Description of Business Celsion Corporation (“Celsion” and the “Company”) is a fully integrated, clinical stage biotechnology company focused on advancing a portfolio of innovative treatments including DNA-based immunotherapies, next generation vaccines and directed chemotherapies through clinical trials and eventual commercialization. The Company’s product pipeline includes GEN-1, a DNA-based immunotherapy for the localized treatment of ovarian cancer and ThermoDox ® Basis of Presentation The accompanying consolidated financial statements of Celsion have been prepared in accordance with generally accepted accounting principles (“GAAP”) in the U.S. and include the accounts of the Company and CLSN Laboratories, Inc. All significant intercompany balances and transactions have been eliminated in consolidation. The preparation of financial statements in conformity with GAAP requires management to make judgments, estimates, and assumptions that affect the amount reported in the Company’s financial statements and accompanying notes. Actual results could differ materially from these estimates. Events and conditions arising subsequent to the most recent balance sheet date through the date of the issuance of these consolidated financial statements have been evaluated for their possible impact on the financial statements and accompanying notes. No events and conditions would give rise to any information that required accounting recognition or disclosure in the financial statements other than those arising in the ordinary course of business. Use of Estimates The preparation of financial statements in conformity with US GAAP requires the Company to make estimates and assumptions that affect the reported amounts of assets and liabilities and disclosure of contingent assets and liabilities at the date of the financial statements and the reported amounts of expenses during the reporting period. On an ongoing basis, the Company evaluates its estimates using historical experience and other factors, including the current economic environment. Significant items subject to such estimates are assumptions used for purposes of determining stock-based compensation, the fair value of the earn-out milestone liabilities, estimates for contingent liabilities, if any, and accounting for valuation of in-process research and development assets and goodwill evaluation. Management believes its estimates to be reasonable under the circumstances. Actual results could differ significantly from those estimates. Significant estimates in these financials are the valuation of options granted and valuation methods used to determine the recoverability of goodwill and other intangible assets. Revenue Recognition The Company’s sole revenue stream is related to the Hisun agreement described in Note 18. There were no accounts receivable as of December 31, 2020 or 2019. Contract liabilities from the Hisun agreement amounted to $1,000,000 and $1,500,000 at December 31, 2020 and 2019, respectively. Contract liabilities values represent the value of cash received before the services were provided. Cash and Cash Equivalents Cash and cash equivalents include cash on hand and investments purchased with an original maturity of three months or less. A portion of these funds are not covered by FDIC insurance. Fair Value of Financial Instruments The carrying values of investment securities approximate their respective fair values. Management believes that the carrying amounts of the Company’s investment securities, including cash and cash equivalents, accounts payable and accrued expenses, approximate fair value due to the short-term nature of those instruments. Short-term investments are recorded at their estimated fair value. Short Term Investments The Company classifies its investments in debt securities with readily determinable fair values as investments available-for-sale in accordance with Accounting Standards Codification (“ASC”) 320, Investments - Debt and Equity Securities. Available-for-sale securities consist of debt securities not classified as trading securities or as securities to be held to maturity. The Company has classified all of its investments as available-for-sale. Unrealized holding gains and losses on available-for-sale securities are reported as a net amount in accumulated other comprehensive gain or loss in stockholders’ equity until realized. Gains and losses on the sale of available-for-sale securities are determined using the specific identification method. The Company’s short-term investments consist of corporate bonds. Property and Equipment Property and equipment are stated at cost less accumulated depreciation and amortization. Depreciation is provided over the estimated useful lives of the related assets, ranging from three to seven years, using the straight-line method. Amortization is recognized over the lesser of the life of the asset or the lease term. Major renewals and improvements are capitalized at cost and ordinary repairs and maintenance are charged against operating expenses as incurred. Depreciation expense was approximately $130,000 and $128,500 for the years ended December 31, 2020 and 2019, respectively. The Company reviews property and equipment for impairment whenever events or changes in circumstances indicate that the carrying amount of an asset may not be recoverable. An asset is considered impaired if its carrying amount exceeds the future net undiscounted cash flows that the asset is expected to generate. If such asset is considered to be impaired, the impairment recognized is the amount by which the carrying amount of the asset, if any, exceeds its fair value determined using a discounted cash flow model. There was no impairment of property or equipment during 2020 or 2019. Deposits Deposits include real property security deposits and other deposits which are contractually required and of a long-term nature. In-Process Research and Development, Other Intangible Assets and Goodwill During 2014, the Company acquired certain assets of EGEN, Inc. As more fully described in Note 5, the acquisition was accounted for under the acquisition method of accounting which required the Company to perform an allocation of the purchase price to the assets acquired and liabilities assumed. Under the acquisition method of accounting, the total purchase price is allocated to net tangible and intangible assets and liabilities based on their estimated fair values as of the acquisition date. Impairment or Disposal of Long-Lived Assets The Company assesses the impairment of its long-lived assets under accounting standards for the impairment or disposal of long-lived assets whenever events or changes in circumstances indicate that the carrying value may not be recoverable. For long-lived assets to be held and used, the Company recognizes an impairment loss only if its carrying amount is not recoverable through its undiscounted cash flows and measures the impairment loss based on the difference between the carrying amount and fair value. See Note 5 for information on impairment losses of its in - Comprehensive Income (Loss) ASC 220, Comprehensive Income 220 Research and Development Research and development costs are expensed as incurred. Equipment and facilities acquired for research and development activities that have alternative future uses are capitalized and charged to expense over their estimated useful lives. Net Loss Per Common Share Basic and diluted net loss per common share was computed by dividing net loss for the year by the weighted average number of shares of common stock outstanding, both basic and diluted, during each period. The impact of common stock equivalents has been excluded from the computation of diluted weighted average common shares outstanding in periods where there is a net loss, as their effect is anti-dilutive. For the years ended December 31, 2020 and 2019, the total number of shares of common stock issuable upon exercise of warrants and equity awards is 8,481,041 and 4,766,990, respectively. Warrants with an exercise price of $0.01 (as more fully described in Note 13 of these financial statements) exercisable for 200,000 shares of common stock issued in March 2019 and exercised for 197,260 shares of stock through a cashless conversion in October 2020, were considered issued in calculating basic loss per share for each year. For the year ended December 31, 2020 and 2019, diluted loss per common share is the same as basic loss per common share as all options and all other warrants that were convertible into shares of the Company’s common stock were excluded from the calculation of diluted earnings attributable to common stockholders per common share as their effect would be anti-dilutive. Income Taxes Income taxes are accounted for under the asset and liability method. Under this method, deferred tax assets and liabilities are recognized for the future tax consequences attributable to differences between the financial statement carrying amounts of existing assets and liabilities and their respective tax bases and operating loss and tax credit carry forwards. Deferred tax assets and liabilities are measured using enacted tax rates expected to apply to taxable income in the years in which those temporary differences are expected to be recovered or settled. The effect on deferred tax asset and liabilities of a change in tax rates is recognized in results of operations in the period that the tax rate change occurs. Valuation allowances are established, when necessary, to reduce deferred tax assets to the amount expected to be realized. In accordance with ASC 740, Income Taxes, As more fully discussed in Note 9, on February 12, 2021, the Company received approval from the New Jersey Economic Development Authority to sell $2.0 million of its New Jersey net operating losses recognizing a tax benefit for the year ended December 31, 2020 for the net proceeds (approximately $1.85 million) by reducing the deferred income tax valuation allowance. In February of 2021, the Company entered into an agreement to sell these net operating losses and expects to receive net proceeds of approximately $1.85 million by the end of the first quarter of 2021. During 2019 and 2018, the Company submitted applications to sell a portion of the Company’s State of New Jersey net operating losses as part of the Technology Business Tax Certificate Program sponsored by The New Jersey Economic Development Authority. Under the program, emerging biotechnology companies with unused NOLs and unused research and development credits are allowed to sell these benefits to other New Jersey-based companies. In 2019 and 2018, the Company sold NOLs totaling $13 million, receiving net proceeds of $1.8 million and $10.4 million, respectively. During 2021, the New Jersey State Legislature increased the maximum lifetime benefit per company from $15 million to $20 million, which will allow the Company to participate in this innovative funding program in future years. Stock-Based Compensation In March 2016, the Financial Accounting Standards Board (“FASB”) issued ASU 2016-09, Compensation-Stock Compensation Recent Accounting Pronouncements From time to time, new accounting pronouncements are issued by the Financial Accounting Standards Board (“FASB”) and are adopted by us as of the specified effective date. Unless otherwise discussed, we believe that the impact of recently issued accounting pronouncements will not have a material impact on the Company’s consolidated financial position, results of operations, and cash flows, or do not apply to our operations. In February 2016, the FASB issued ASU No. 2016-02, “Leases” - Topic 842 (ASC Topic 842), which requires that lessees recognize assets and liabilities for leases with lease terms greater than twelve months in the balance sheet. Leases will be classified as either finance or operating, with classification affecting the pattern of expense recognition in the income statement. This update also requires improved disclosures to help users of financial statements better understand the amount, timing and uncertainty of cash flows arising from leases. The update became effective for fiscal years beginning after December 15, 2018, including interim reporting periods within that reporting period. We adopted ASC Topic 842 effective January 1, 2019 and elected to apply the available practical expedients and implement internal controls to enable the preparation of financial information on adoption. We identified two of our leases consisting of the New Jersey corporate office lease and the Alabama lab facility lease as being subject to ASC Topic 842. The adoption of this standard resulted in the recognition of right-of-use assets of approximately $1.4 million, related operating lease liabilities of $1.5 million and reduced other liabilities by approximately $0.1 million on the consolidated balance sheets as of January 1, 2019 with no material impact to the opening balance of retained earnings. See Note 15 for further discussions regarding the adoption of ASC Topic 842. In June 2016, the FASB issued ASU No. 2016-13, “Financial Instruments – Credit Losses (Topic 326): Measurement of Credit Losses on Financial Instruments”, which modifies the measurement of expected credit losses on certain financial instruments. The Company expects to adopt ASU 2016-13 in its first quarter of 2021 utilizing the modified retrospective transition method. Based on the composition of the Company’s investment portfolio and current market conditions, the adoption of ASU 2016-13 is not expected to have a material impact on its consolidated financial statements. In August 2018, the FASB issued ASU No. 2018-13, Fair Value Measurement: Disclosure Framework – Changes to the Disclosure Requirements for Fair Value Measurement In December 2019, the FASB issued ASU No. 2019-12, Income Taxes (Topic 740). The standard simplifies the accounting for incomes taxes by removing certain exceptions to the general principles in Topic 740 related to the approach for intraperiod tax allocation and the recognition of deferred tax liabilities for outside basis differences. The standard also clarifies the accounting for transactions that result in a step-up in the tax basis of goodwill. The standard also improves consistent application of and simplifies GAAP for other areas of Topic 740 by clarifying and amending existing guidance. The amendment is effective for fiscal years, and interim periods within those fiscal years, beginning after December 15, 2020. Early adoption is permitted. The Company does not believe that the adoption of this standard will have an impact on its consolidated financial statements.

Financial Condition

Financial Condition	12 Months Ended
	Dec. 31, 2020
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Financial Condition	2. FINANCIAL CONDITION Since inception, the Company has incurred substantial operating losses, principally from expenses associated with the Company’s research and development programs, clinical trials conducted in connection with the Company’s product candidates, and applications and submissions to the U.S. Food and Drug Administration. The Company has not generated significant revenue and has incurred significant net losses in each year since our inception. As of December 31, 2020, the Company has incurred approximately $312 million of cumulative net losses and we had approximately $17.2 million in cash and cash equivalents. We have substantial future capital requirements to continue our research and development activities and advance our product candidates through various development stages. The Company believes these expenditures are essential for the commercialization of its technologies. The Company expects its operating losses to continue for the foreseeable future as it continues its product development efforts, and when it undertakes marketing and sales activities. The Company’s ability to achieve profitability is dependent upon its ability to obtain governmental approvals, manufacture, and market and sell its new product candidates. There can be no assurance that the Company will be able to commercialize its technology successfully or that profitability will ever be achieved. The operating results of the Company have fluctuated significantly in the past. In January 2020, the WHO declared an outbreak of coronavirus, COVID-19, to be a “Public Health Emergency of International Concern,” and the U.S. Department of Health and Human Services declared a public health emergency to aid the U.S. healthcare community in responding to COVID-19. This virus has spread to over 100 countries, including the U.S. Governments and businesses around the world have taken unprecedented actions to mitigate the spread of COVID-19, including, but not limited to, shelter-in-place orders, quarantines, significant restrictions on travel, as well as restrictions that prohibit many employees from going to work. Uncertainty with respect to the economic impacts of the pandemic has introduced significant volatility in the financial markets. The Company did not observe significant impacts on its business or results of operations during 2020 due to the global emergence of COVID-19. While the extent to which COVID-19 impacts the Company’s future results will depend on future developments, the pandemic and associated economic impacts could result in a material impact to the Company’s future financial condition, results of operations and cash flows. The Company’s ability to raise additional capital may be adversely impacted by potential worsening global economic conditions and the recent disruptions to, and volatility in, financial markets in the U.S. and worldwide resulting from the ongoing COVID-19 pandemic. The disruptions caused by COVID-19 may also disrupt the clinical trials process and enrolment of patients. This may delay commercialization efforts. The Company continues to monitor its operating activities in light of these events, and it is reasonably possible that the virus could have a negative effect on the Company’s financial condition and results of operations. The specific impact, if any, is not readily determinable as of the date of these financial statements. The actual amount of funds the Company will need to operate is subject to many factors, some of which are beyond the Company’s control. These factors include the following: ● the progress of research activities; ● the number and scope of research programs; ● the progress of preclinical and clinical development activities; ● the progress of the development efforts of parties with whom the Company has entered into research and development agreements; ● the costs associated with additional clinical trials of product candidates; ● the ability to maintain current research and development licensing arrangements and to establish new research and development and licensing arrangements; ● the ability to achieve milestones under licensing arrangements; ● the costs involved in prosecuting and enforcing patent claims and other intellectual property rights; and ● the costs and timing of regulatory approvals. On July 13, 2020, the Company announced that it has received a recommendation from the independent DMC to consider stopping the global Phase III OPTIMA Study of ThermoDox ® During 2020, 2019 and 2018, the Company submitted applications to sell a portion of the Company’s State of New Jersey net operating losses as part of the Technology Business Tax Certificate Program sponsored by The New Jersey Economic Development Authority. Under the program, emerging biotechnology companies with unused NOLs and unused research and development credits are allowed to sell these benefits to other New Jersey-based companies. In 2018 and 2019, the Company sold NOLs totaling $13 million receiving net proceeds of $12.2 million. In June 2020 and as updated in September 2020, the Company filed an application with the New Jersey Economic Development Authority to sell substantially all of its remaining State of New Jersey net operating losses totaling $2.0 million available under the program. On February 12, 2021, the New Jersey Economic Development Authority approved the full amount of the Company’s application. In February of 2021, the Company entered into an agreement to sell the net operating losses from the 2020 application and expects to receive net proceeds of approximately $1.85 million by the end of the first quarter of 2021. During 2021, the New Jersey State Legislature increased the maximum lifetime benefit per company from $15 million to $20 million, which will allow the Company to participate in this innovative funding program in future years. In June 2018, the Company entered into a Credit Agreement with Horizon Technology Finance Corporation (“Horizon”) that provided $10 million in capital (the “Horizon Credit Agreement”). The obligations under the Horizon Credit Agreement are secured by a first-priority security interest in substantially all assets of Celsion other than intellectual property assets. Payments under the loan agreement are interest only (calculated based on one-month LIBOR plus 7.625%) for the first twenty-four (24) months through July 2020, followed by a 24-month amortization period of principal and interest starting on August 1, 2020 and ending through the scheduled maturity date. On August 28, 2020, in connection with an Amendment to the Horizon Credit Agreement, Celsion repaid $5 million of the $10 million loan and $0.2 million in related end of term charges, and the remaining $5 million in obligations were restructured as more fully discussed in Note 8 to these financial statements. As more fully discussed in Note 10, during 2021 through the date of the filing of this Annual Report on Form 10-K, the Company has raised approximately $6.9 million in gross proceeds from the use of its JonesTrading Capital on Demand TM

Investments in Debt Securities

Investments in Debt Securities Available for Sale	12 Months Ended
	Dec. 31, 2020
Investments, Debt and Equity Securities [Abstract]
Investments in Debt Securities Available for Sale	3. INVESTMENTS IN DEBT SECURITIES AVAILABLE FOR SALE Investments in debt securities available for sale with a fair value of $7,985,886 as of December 31, 2019 consisted of corporate debt securities. These investments are valued at estimated fair value, with unrealized gains and losses reported as a separate component of stockholders’ equity in accumulated other comprehensive loss. The Company only had investments in cash and cash equivalents at December 31, 2020. Investments in debt securities available for sale are evaluated periodically to determine whether a decline in their value is other than temporary. The term “other than temporary” is not intended to indicate a permanent decline in value. Rather, it means that the prospects for near term recovery of value are not necessarily favorable, or that there is a lack of evidence to support fair values equal to, or greater than, the carrying value of the security. Management reviews criteria such as the magnitude and duration of the decline, as well as the reasons for the decline, to predict whether the loss in value is other than temporary. Once a decline in value is determined to be other than temporary, the value of the security is reduced and a corresponding charge to earnings is recognized. A summary of the cost, fair value and maturities of the Company’s short-term investments is as follows: December 31, 2020 December 31, 2019 Cost Fair Value Cost Fair Value Short-term investments Corporate debt securities $ - $ - $ 7,943,108 $ 7,985,886 Total $ - $ - $ 7,943,108 $ 7,985,886 December 31, 2020 December 31, 2019 Cost Fair Value Cost Fair Value Short-term investment maturities Within 3 months $ - $ - $ 7,943,108 $ 7,985,886 Between 3-12 months - - - - Total $ - $ - $ 7,943,108 $ 7,985,886 The following table shows the Company’s investment in debt securities available for sale gross unrealized gains (losses) and fair value by investment category and length of time that individual securities have been in a continuous unrealized loss position at December 31, 2020 and 2019. The Company has reviewed individual securities to determine whether a decline in fair value below the amortizable cost basis is other than temporary. December 31, 2020 December 31, 2019 Available for sale securities (all unrealized holding gains and losses are less than 12 months at date of measurement) Fair Value Unrealized Holding Gains (Losses) Fair Value Unrealized Holding Gains (Losses) Investments in debt securities with unrealized gains $ - $ - $ 7,985,886 $ 42,778 Investments in debt securities with unrealized losses - - - - Total $ - $ - $ 7,985,886 $ 42,778 Investment income, which includes net realized losses on sales of available for sale securities and investment income interest and dividends, is summarized as follows: 2020 2019 Interest and dividends accrued and paid $ 66,553 $ 442,987 Realized gains 53,354 57,895 Investment income net $ 119,907 $ 500,882

Fair Values of Financial Instru

Fair Values of Financial Instruments	12 Months Ended
	Dec. 31, 2020
Fair Value Disclosures [Abstract]
Fair Values of Financial Instruments	4. FAIR VALUES OF FINANCIAL INSTRUMENTS FASB ASC Section 820, Fair Value Measurements and Disclosures Level 1: Quoted prices (unadjusted) or identical assets or liabilities in active markets that the entity has the ability to access as of the measurement date; Level 2: Significant other observable inputs other than Level 1 prices such as quoted prices for similar assets or liabilities; quoted prices in markets that are not active; or other inputs that are observable or can be corroborated by observable market data; and Level 3: Significant unobservable inputs that reflect a reporting entity’s own assumptions that market participants would use in pricing an asset or liability. Cash and cash equivalents, other current assets, accounts payable and other accrued liabilities are reflected in the condensed consolidated balance sheet at their approximate estimated fair values primarily due to their short-term nature. The fair values of securities available for sale is determined by relying on the securities’ relationship to other benchmark quoted securities and classified its investments as Level 2 items in both 2020 and 2019. There were no transfers of assets or liabilities between Level 1 and Level 2 and no transfers in or out of Level 3 during the years ended December 31, 2020 and 2019. The changes in Level 3 liabilities were the result of changes in the fair value of the earn-out milestone liability included in earnings and in-process R&D. The earnout milestone liability is valued using a risk-adjusted assessment of the probability of payment of each milestone, discounted to present value using an estimated time to achieve the milestone (see Note 12). Assets and liabilities measured at fair value are summarized below: Total Fair Value Quoted Prices in Active Markets for Identical Assets/Liabilities (Level 1) Significant Other Observable Inputs (Level 2) Significant Unobservable Inputs (Level 3) Assets: Recurring items as of December 31, 2020 Corporate debt securities, available for sale $ – $ – $ – $ – Non-recurring items as of December 31, 2020 In-process R&D (Note 5) $ 13,366,234 $ – $ – $ 13,366,234 Recurring items as of December 31, 2019 Corporate debt securities, available for sale $ 7,985,886 $ – $ 7,985,886 $ – Non-recurring items as of December 31, 2019 In-process R&D (Note 5) $ 15,736,491 $ – $ – $ 15,736,491 Liabilities: Recurring items as of December 31, 2020 Earn-out milestone liability (Note 12) $ 7,018,000 $ – $ – $ 7,017,000 Recurring items as of December 31, 2019 Earn-out milestone liability (Note 12) $ 5,717,709 $ – $ – $ 5,717,709

Intangible Assets

Intangible Assets	12 Months Ended
	Dec. 31, 2020
Intangible Assets, Net (Including Goodwill) [Abstract]
Intangible Assets	5. INTANGIBLE ASSETS In June 2014, we completed the acquisition of substantially all of the assets of EGEN, Inc., an Alabama corporation, which has changed its company name to EGWU, Inc. after the closing of the acquisition (“EGEN”). We acquired all of EGEN’s right, title and interest in and to substantially all of the assets of EGEN, including cash and cash equivalents, patents, trademarks and other intellectual property rights, clinical data, certain contracts, licenses and permits, equipment, furniture, office equipment, furnishings, supplies and other tangible personal property. In addition, CLSN Laboratories assumed certain specified liabilities of EGEN, including the liabilities arising out of the acquired contracts and other assets relating to periods after the closing date. Acquired In-process Research and Development. Acquired in-process research and development (IPR&D) consists of EGEN’s drug technology platforms: TheraPlas and TheraSilence. The fair value of the IPR&D drug technology platforms was estimated to be $24.2 million as of the acquisition date. As of the closing of the acquisition, the IPR&D was considered indefinite lived intangible assets and will not be amortized. IPR&D is reviewed for impairment at least annually as of our third quarter ended September 30, and whenever events or changes in circumstances indicate that the carrying value of the assets might not be recoverable. The Company’s IPR&D consisted of three core elements, its RNA delivery system, its glioblastoma multiforme cancer (GBM) product candidate and its ovarian cancer indication. The Company’s ovarian cancer indication, with original value of $13.3 million, has not been impaired since its acquisition. At September 30, 2020, the Company evaluated its IPR&D of the ovarian cancer indication and concluded that it is not more likely than not that the asset is impaired. As no other indicators of impairment existed during the fourth quarter of 2020 or 2019, no impairment charges were recorded during 2020 or 2019. The Company’s GBM candidate, with original value of $9.4 million had cumulative impairments through 2018 of $7 million, with remaining carrying value of $2.4 million at December 31, 2019. On September 30, 2020, the Company evaluated its IPR&D for the (GBM) product candidate and concluded that it is more likely than not that the asset is further impaired. After this assessment on September 30, 2020, the Company wrote off the remaining $2.4 million of this asset, thereby recognizing a non-cash charge of $2.4 million in the third quarter of 2020. Covenants Not to Compete Pursuant to the EGEN Purchase Agreement, EGEN provided certain covenants (“Covenant Not To Compete”) to the Company whereby EGEN agreed, during the period ending on the seventh anniversary of the closing date of the acquisition on June 20, 2014, not to enter into any business, directly or indirectly, which competes with the business of the Company nor will it contact, solicit or approach any of the employees of the Company for purposes of offering employment. The Covenant Not to Compete which was valued at approximately $1.6 million at the date of the EGEN acquisition has a definitive life and is amortized on a straight-line basis over its life of 7 years. The Company recognized amortization expense of $227,316 in 2020 and 2019. The carrying value of the Covenant Not to Compete was $113,660, net of $1,477,554 accumulated amortization, as of December 31, 2020 and $340,976, net of $1,250,238 accumulated amortization as of December 31, 2019. The Covenant Not to Compete will be fully amortized by the end of the second quarter of 2021. Goodwill The purchase price exceeded the estimated fair value of the net assets acquired by approximately $2.0 million which was recorded as Goodwill. Goodwill represents the difference between the total purchase price for the net assets purchased from EGEN and the aggregate fair values of tangible and intangible assets acquired, less liabilities assumed. Goodwill is reviewed for impairment at least annually as of our third quarter ended September 30 or sooner if we believe indicators of impairment exist. As of September 30, 2020, we concluded that the Company’s fair value exceeded its carrying value therefore “it is not more likely than not” that the Goodwill was impaired. As no other indicators of impairment existed during the fourth quarters of 2020 or 2019, the Company concluded it is “not more likely than not” Goodwill was impaired. Following is a summary of the net fair value of the assets acquired in the EGEN acquisition for the two years ended December 31, 2020: IPR&D Goodwill Covenant Not to Compete Balance at January 1, 2019, net $ 15,736,491 $ 1,976,101 568,292 Amortization - - (227,316 ) Impairment charge - - - Balance at December 31, 2019, net 15,736,491 1,976,101 340,976 Amortization - - (227,316 ) Impairment charge (2,370,257 ) - - Balance at December 31, 2020, net $ 13,366,234 $ 1,976,101 $ 113,660

Property and Equipment

Property and Equipment	12 Months Ended
	Dec. 31, 2020
Property, Plant and Equipment [Abstract]
Property and Equipment	6. PROPERTY AND EQUIPMENT Property and equipment at December 31, 2020 and 2019 consist of the following: December 31, 2020 2019 Machinery and equipment (5-7 year life) $ 2,832,995 $ 2,831,564 Furniture and fixtures (3-5 year life) 344,939 327,278 Leasehold improvements (5-7 year life) 343,202 343,202 3,521,136 3,502,044 Less accumulated depreciation and amortization (3,226,585 ) (3,096,681 ) Total $ 294,551 $ 405,363

Other Accrued Liabilities

Other Accrued Liabilities	12 Months Ended
	Dec. 31, 2020
Payables and Accruals [Abstract]
Other Accrued Liabilities	7 . Other accrued liabilities at December 31, 2020 and 2019 include the following: December 31, 2020 2019 Amounts due to contract research organizations and other contractual agreements $ 636,000 $ 475,440 Accrued payroll and related benefits 1,736,271 1,604,541 Accrued professional fees 66,850 204,155 Other 19,411 19,411 Total $ 2,458,532 $ 2,303,547

Notes Payable

Notes Payable	12 Months Ended
	Dec. 31, 2020
Debt Disclosure [Abstract]
Notes Payable	8. NOTES PAYABLE Horizon Credit Agreement On June 27, 2018, the Company entered into a loan agreement with Horizon Technology Finance Corporation (“Horizon”) that provided $10 million in new capital (the “Horizon Credit Agreement”). The Company drew down $10 million upon closing of the Horizon Credit Agreement on June 27, 2018. On August 28, 2020, Horizon and the Company amended the Horizon Credit Agreement (the “Amendment”) whereby Celsion repaid $5 million of the $10 million loan and $0.2 million in related end of term charges, and the remaining $5 million in obligations were restructured as set forth below. Pursuant to the Amendment, the remaining $5 million in obligations of Celsion under the Initial Horizon Credit Agreement are secured by a first-priority security interest in substantially all assets of Celsion other than intellectual property assets. The obligations bear interest at a rate calculated based an amount by which the one-month LIBOR exceeds 2% plus 7.625%. In no event shall the interest rate be less than 9.625%. Payments pursuant to the Amendment are interest only for the first twelve (12) months after August 1, 2020, followed by a 21-month amortization period of principal and interest through the scheduled maturity date. In addition, the remaining $5 million in obligations is subject to an end of term fee equal, in the aggregate, to $275,000, which amount shall be payable upon the maturity of the obligations or upon the date of final payment or default, as applicable. In connection with the Amendment, Celsion agreed to a liquidity covenant which provides that, at all times, Celsion shall maintain unrestricted cash and/or cash equivalents on deposit in accounts over which the applicable Lenders maintain an account control agreement in an amount not less than $2.5 million. In addition, pursuant to the Amendment, Celsion has agreed to provide evidence to Horizon on or before March 31, 2021, that it has received aggregate cash proceeds of not less than $5 million from the sale of equity, debt, its New Jersey net operating losses, or a combination thereof, subsequent to the date of the Amendment. The Company met this requirement during the fourth quarter of 2020. In connection with the Horizon Credit Agreement, the Company incurred financing fees and expenses totaling $175,000 which were recorded and classified as debt discount. In addition, the Company paid loan origination fees of $100,000 which were recorded and classified as debt discount. These debt discount amounts totaling $782,116 were being amortized as interest expense using the effective interest method over the life of the loan. Also, in connection with each of the Horizon Credit Agreements, the Company is required to pay an end of term charge equal to 4.0% of the original loan amount at time of maturity. Therefore, these amounts totaling $400,000 were being amortized as interest expense using the effective interest method over the life of the loan. As a fee in connection with the Horizon Credit Agreement, Celsion issued Horizon warrants exercisable for a total of 190,114 shares of Celsion’s common stock (the “Existing Warrants”) at a per share exercise price of $2.63. The Horizon Warrants were immediately exercisable for cash or by net exercise from the date of grant and will expire after ten years from the date of grant. The Company valued the Horizon Warrants issued using the Black-Scholes option pricing model and recorded a total of $507,116 as a direct deduction from the debt liability, consistent with the presentation of debt discounts, and are being amortized as interest expense using the effective interest method over the life of the loan. Pursuant to the Amendment, one-half of the aggregate Existing Warrants, exercisable for a total of 95,057 shares of Celsion’s common stock, have been canceled, and, in connection with the Amendment, Celsion issued Horizon new warrants exercisable at a per share exercise price equal to $1.01 for a total of 247,525 shares of Celsion’s common stock (the “New Warrants” and, together with the Existing Warrants, the “Warrants”). The remaining 95,057 Existing Warrants issued in connection with the Initial Horizon Credit Agreement remain outstanding at a per share exercise price of $2.63. The New Warrants are immediately exercisable for cash or by net exercise from the date of grant and will expire after ten years from the date of grant. Effective October 27, 2020. The Horizon Credit Agreement contains customary representations, warranties and affirmative and negative covenants including, among other things, covenants that limit or restrict Celsion’s ability to grant liens, incur indebtedness, make certain restricted payments, merge, or consolidate and make dispositions of assets. The Amendment was evaluated in accordance with FASB ASC 470-50, Debt-Modifications and Extinguishments We accounted for the remaining $5 million of obligation under the Amendment as a debt modification to the initial agreement with respect to the minor changes in cash flows. Also, in connection with the $5 million remaining obligations, we recorded $5,000 of financing fees and the New Warrant fair value of $247,548 as additional debt discount on the $5 million remaining obligation. Therefore, approximately $109,706 of unamortized debt discount will be amortized over the remaining life of the new obligations. The $275,000 of end of term fees, net of previously amortized end of term fees totaling $142,605 previously accrued on the original note associated with the $5 million remaining obligation, will be amortized as interest expense over the remaining life of the new obligations. During 2020, the Company incurred $808,899 in interest expense and amortized $483,439 as interest expense for debt discounts and end of term charges in connection with the Horizon Credit Agreement. During 2019, the Company incurred $1,006,760 in interest expense and amortized $386,640 as interest expense for debt discounts and end of term charges in connection with the Horizon Credit Agreement. Following is a schedule of future principal payments, net of unamortized debt discounts and amortized end of term charges, due on the Horizon Credit Agreement: For the year ending December 31, 2021 $ 1,190,475 2022 2,857,140 2023 and thereafter 952,385 Subtotal of future principal payments 5,000,000 Unamortized debt issuance costs, net 51,160 Total $ 5,051,160 Paycheck Protection Program On April 23, 2020, we entered into a loan agreement with Silicon Valley Bank (the “April PPP Loan”), pursuant to the Paycheck Protection Program (the “PPP”), established pursuant to the recently enacted Coronavirus Aid, Relief, and Economic Security Act (the “CARES Act”) and administered by the U.S. Small Business Administration (“SBA”). We thereafter received proceeds of $632,220 under the April PPP Loan. The April PPP Loan application required Celsion to certify that there was economic uncertainty surrounding the Company and that, as such, the April PPP Loan was necessary to support our ongoing operations. Celsion made this certification in good faith after analyzing, among other things, its financial situation and access to alternative forms of capital and believed that the Company satisfied all eligibility criteria for the April PPP Loan, and that our receipt of the April PPP Loan proceeds was consistent with the broad objectives of the PPP of the CARES Act. The certification given with respect to the April PPP Loan did not contain any objective criteria and was subject to interpretation. Considering subsequent guidance issued by the SBA in consultation with the U.S. Department of the Treasury at that time, out of an abundance of caution we returned the proceeds of the PPP Loan in full on May 13, 2020. Shortly after the April PPP Loan was repaid, the SBA provided further guidance with respect to these certifications providing a safe harbor under which companies such as Celsion with PPP loans of less than $2 million will be deemed to have made these certifications in good faith. Therefore, as the Company continued to believe it qualifies for a loan under the PPP, it reapplied for and eventually received the new PPP Loan for $692,530 on May 26, 2020 (the “May PPP Loan”). The May PPP Loan was guaranteed by the SBA and evidenced by a promissory note of the Company dated May 26, 2020 (the “Note”) in the principal amount of $692,530 payable to the lender. Pursuant to the terms of the Note, was payable in part or in full, at any time, without penalty. On June 22, 2020, as disclosed in the Company’s Current Report on Form 8-K filed on the same date, the Company commenced an offering of 2,666,667 shares of its common stock which closed on June 24, 2020 (Note 10) and received net proceeds of approximately $9.1 million. In light of the proceeds received from this equity offering, the Company elected to repay the May PPP Loan in full (including interest accrued of $577) on June 24, 2020, terminating all obligations of the Company under the Note.

Income Taxes

Income Taxes	12 Months Ended
	Dec. 31, 2020
Income Tax Disclosure [Abstract]
Income Taxes	9. INCOME TAXES The income tax provision (benefit) for the years ended December 31, 2020 and 2019 consists of the following: 2020 2019 Federal Current $ - $ - Deferred - - State and Local - - Current - - Deferred (1,845,823 ) (1,816,474 ) Total $ (1,845,823 ) $ (1,816,474 ) A reconciliation of the Company’s statutory tax rate to the effective rate for the years ended December 31, 2020 and 2019 is as follows: 2020 2019 Federal statutory rate 21.0 % 21.0 % State taxes, net of federal tax benefit 7.8 9.8 Permanent differences (5.3 ) (2.6 ) Other – 1.1 Change in valuation allowance and deferred rate change, net (15.5 ) (19.6 ) Effective tax rate 8.0 % 9.7 % The components of the Company’s deferred tax asset as of December 31, 2020 and 2019 are as follows: December 31, 2020 2019 Net operating loss carryforwards $ 60,446,000 $ 58,243,000 Other Deferred tax assets, net 5,182,000 254,000 Subtotal 65,628,000 58,497,000 Valuation allowance (63,782,177 ) (56,677,676 ) Total deferred tax asset $ 1,845,823 $ 1,819,324 The evaluation of the realizability of such deferred tax assets in future periods is made based upon a variety of factors that affect the Company’s ability to generate future taxable income, such as intent and ability to sell assets and historical and projected operating performance. As of December 31, 2020, the Company has established a valuation reserve for its deferred income tax assets other than those related to its New Jersey NOLs. At December 31, 2020, after its evaluation of its New Jersey NOLs as discussed more fully below, the Company reduced the valuation reserve and recognized $1.8 million as a deferred income tax asset. Such tax assets are available to be recognized and benefit future periods. As of December 31, 2020, the Company had federal net operating loss carryforwards of approximately $274 million, net of net operating losses utilized in prior years of which $225 million, if unused, will expire starting in 2022 through 2037. The Federal net operating loss generated for the years ended December 31, 2018, 2019 and 2020 of approximately $45 million can be carried forward indefinitely. However, the deduction for net operating losses incurred in tax years beginning after January 1, 2018 is limited to 80% of annual taxable income. On March 27, 2020, the Coronavirus Aid, Relief, and Economic Security Act (“CARES Act”) was enacted in response to the COVID-19 pandemic. The CARES Act provides for economic and cash liquidity stimulus through various means including payroll tax credits, payroll tax deferral, short term changes in tax deductibility of interest expenses among other things. The Act also permits NOL carryovers and carrybacks to offset 100% of taxable income for taxable years beginning before 2021. Previously, NOLs generated after December 31, 2017 were limited to 80% of taxable income in future years. In addition, the CARES Act allows NOLs incurred in 2018, 2019 and 2020 to be carried back to each of the five preceding tax years. The Company evaluated the various aspects of the Act and determined that there was no material effect on the Financial Statements. As of December 31, 2020, the Company had state net operating loss carryforwards of approximately $39 million, net of net operating losses utilized in prior years, and, if unused, will expire starting in 2029 through 2040. During 2020, 2019 and in prior years, the Company performed analyses to determine if there were changes in ownership, as defined by Section 382 of the Internal Revenue Code that would limit its ability to utilize certain net operating loss and tax credit carry forwards. The Company determined that it experienced ownership changes, as defined by Section 382, in connection with certain common stock offerings in July 2011, February 2013, June 2013, June 2015, February 2017, June 2017, October 2017, August 2018 and February 2020. As a result, the utilization of the Company’s federal tax net operating loss carry forwards generated prior to the ownership changes are limited. As of December 31, 2020, the Company has net operating loss carry forwards for U.S. federal and state tax purposes of approximately $266 million, before excluding net operating losses that have been limited as a result of Section 382 limitations. The annual limitation due to Section 382 for net operating loss carry forward utilization is approximately $4.2 million per year for approximately $90 million in net operating loss carry forwards existing at the ownership change occurring in July 2011, approximately $1.4 million per year for approximately $34 million of additional net operating losses occurring from July 2011 to the ownership change that occurred in February 2013, approximately $1.5 million per year for approximately $4 million of additional net operating losses occurring from February 2013 to the ownership change that occurred in June 2013, approximately $1.6 million per year for approximately $40 million of additional net operating losses occurring from June 2013 to the ownership change that occurred in June 2015, approximately $0.3 million per year for approximately $35 million of additional net operating losses occurring from June 2015 to the ownership change that occurred in February 2017, approximately $0.3 million per year for approximately $7 million of additional net operating losses occurring from February 2017 to the ownership change that occurred in June 2017, approximately $0.8 million per year for approximately $5 million of additional net operating losses occurring from June 2017 to the ownership change that occurred in October 2017, and approximately $1.5 million per year for approximately $30 million of additional net operating losses occurring from October 2017 to the ownership change that occurred in August 2018, approximately $0.8 million per year for approximately $15 million of additional net operating losses occurring from August 2018 to the ownership change that occurred in February 2020. The utilization of these net operating loss carry forwards may be further limited if the Company experiences future ownership changes as defined in Section 382 of the Internal Revenue Code. Sale of New Jersey Net Operating Losses During 2020 and 2019, the Company applied for and received approval to sell a portion of the Company’s New Jersey NOLs as part of the Technology Business Tax Certificate Program sponsored by The New Jersey Economic Development Authority. Under the program, emerging biotechnology companies with unused NOLs and unused research and development credits are allowed to sell these benefits to other companies. During the first quarter of 2021, the Company entered into an agreement to sell the approved portion of the New Jersey NOLs applied for in 2020 for $1.85 million. At December 31, 2020, the Company evaluated the valuation reserve for its tax net operating losses associated with its New Jersey NOLs and reduced the valuation reserve and recognized $1.85 million as a deferred income tax asset and an income tax benefit. The Company expects to complete the sale of these net operating losses by the end of the first quarter of 2021. During the first quarter of 2020, the Company entered into an agreement to sell the approved portion of the New Jersey NOLs applied for in 2019 for $1.8 million. At December 31, 2019, the Company evaluated the valuation reserve for its tax net operating losses associated with its New Jersey NOLs and reduced the valuation reserve and recognized $1.8 million as a deferred income tax asset and an income tax benefit. The Company completed the sale of these net operating losses in the second quarter of 2020.

Stockholders' Equity

Stockholders' Equity	12 Months Ended
	Dec. 31, 2020
Equity [Abstract]
Stockholders' Equity	10. STOCKHOLDERS’ EQUITY In September 2018, the Company filed with the SEC a $75 million shelf registration statement on Form S-3 (the 2018 Shelf Registration Statement) that allows the Company to issue any combination of common stock, preferred stock or warrants to purchase common stock or preferred stock. This shelf registration was declared effective on October 12, 2018 and during January 2021, has been fully utilized. Capital on Demand TM On December 4, 2018, the Company entered into the Capital on Demand Agreement with JonesTrading, pursuant to which the Company may offer and sell, from time to time, through JonesTrading shares of Common Stock having an aggregate offering price of up to $16.0 million. During 2019, the Company sold and issued an aggregate of 0.5 million shares under the Capital on Demand Agreement, receiving approximately $1.0 million in gross proceeds. During 2020, the Company sold and issued an aggregate of 5.2 million shares under the Capital on Demand Agreement, receiving approximately $6.2 million in gross proceeds. During 2021 through the date of this Annual Report on Form 10K, the Company has sold 7.2 million shares under the Capital on Demand Agreement, receiving approximately $6.9 million in gross proceeds under the Capital on Demand Agreement. February 2020 Registered Direct Offering On February 27, 2020, we entered into a Securities Purchase Agreement (the “February 2020 Purchase Agreement”) with several institutional investors, pursuant to which we agreed to issue and sell, in a registered direct offering (the “February 2020 Offering”), an aggregate of 4,571,428 shares (the “Shares”) of our common stock at an offering price of $1.05 per Share for gross proceeds of approximately $4.8 million before the deduction of the Placement Agent fees and offering expenses. The February 2020 Purchase Agreement contained customary representations, warranties and agreements by the Company and customary conditions to closing. In a concurrent private placement (the “Private Placement”), the Company issued to the investors that participated in the February 2020 Offering, for no additional consideration, warrants, to purchase up to 2,971,428 shares of Common Stock (the “Original Warrants”). The Original Warrants were initially exercisable six months following their date of issue and were set to expire on the five-year anniversary of such initial exercise date. The Original Warrants had an exercise price of $1.15 per share subject to adjustment as provided therein. On March 12, 2020, the Company entered into private exchange agreements (the “Exchange Agreements”) with holders of the Original Warrants. Pursuant to the Exchange Agreements, in return for a higher exercise price of $1.24 per share of Common Stock, the Company issued new warrants to the Investors to purchase up to 3,200,000 shares of Common Stock (the “Exchange Warrants”) in exchange for the Original Warrants. The Exchange Warrants, like the Original Warrants, are initially exercisable six months following their issuance (the “Initial Exercise Date”) and expire on the five-year anniversary of their Initial Exercise Date. Other than having a higher exercise price, different issue date, Initial Exercise Date and expiration date, the terms of the Exchange Warrants are identical to those of the Original Warrants. On July 31, 2020, the Company filed a Form S-3 Registration Statement to register the shares of Common Stock issuable under the Exchange Warrants; the Registration Statement was declared effective by the SEC on August 13, 2020. No Exchange Warrants were exercised during 2020. During 2021 thus far, the Company has issued 1.2 million shares pursuant to investors exercising Exchange Warrants, receiving approximately $1.5 million. Underwritten Offering On June 22, 2020, the Company entered into an underwriting agreement (the “Underwriting Agreement”) with Oppenheimer & Co. Inc. (the “Underwriter”), relating to the issuance and sale (the “Underwritten Offering”) of 2,666,667 shares of the Company’s common stock. Pursuant to the terms of the Underwriting Agreement, the Underwriter agreed to purchase the shares at a price of $3.4875 per share. The Underwriter offered the shares at a public offering price of $3.75 per share, reflecting an underwriting discount equal to $0.2625, or 7.0% of the public offering price. The net proceeds to the Company from the Underwritten Offering, after deducting the underwriting discount and estimated offering expenses payable by the Company, were approximately $9.1 million. The Underwriting Agreement contains customary representations, warranties and agreements by the Company, customary conditions to closing, indemnification obligations of the Company and the Underwriter including for liabilities under the Securities Act, other obligations of the parties, and termination provisions. Pursuant to the Underwriting Agreement, until December 31, 2020, the Underwriter shall have a right of first refusal to act as sole underwriter, initial purchaser, placement/selling agent, or arranger, as the case may be, on any new financing for the Company (excluding equipment lease financings, loans or grants from governmental authorities or in connection with government programs and financings relating to or sales of tax attributes) during such period. The Underwriter shall have the sole right to determine whether or not any other broker dealer shall have the right to participate in any such offering and the economic terms of any such participation. Pursuant to the Underwriting Agreement, subject to certain exceptions, the Company and certain of the Company’s executive officers and directors have agreed that, without the prior written consent of the Underwriter and subject to certain negotiated exceptions, they will not, for a period of 60 days, in either case, following the date of the final prospectus supplement, sell or otherwise dispose of any of the Company’s securities held by them. LPC Purchase Agreement On September 8, 2020, the Company entered into a purchase agreement (the “LPC Purchase Agreement”) and a Registration Rights Agreement (the “Registration Rights Agreement”) with Lincoln Park Capital Fund, LLC (“Lincoln Park”), pursuant to which, upon the terms and subject to the conditions and limitations set forth therein, the Company has the right to sell to Lincoln Park up to $26.0 million of shares of the Company’s Common Stock at the Company’s discretion as described below (the “LPC Offering”). Over the 36-month term of the LPC Purchase Agreement, we have the right, but not the obligation, from time to time, in our sole discretion and subject to certain conditions, including that the closing price of our Common Stock is not below $0.25 per share, to direct Lincoln Park to purchase up to an aggregate amount of $26.0 million (subject to certain limitations) of shares of Common Stock. Under the Purchase Agreement, on any business day selected by us, we may direct Lincoln Park to purchase up to 400,000 shares (the “Regular Purchase Share Limit”) of our Common Stock (each such purchase, a “Regular Purchase”). Lincoln Park’s maximum obligation under any single Regular Purchase will not exceed $1,500,000 unless we mutually agree to increase the maximum amount of such Regular Purchase. The purchase price for shares of Common Stock to be purchased by Lincoln Park under a Regular Purchase will be the equal to the lower of (in each case, subject to the adjustments described in the LPC Purchase Agreement): (i) the lowest sale price for our Common Stock on The Nasdaq Capital Market on the applicable purchase date, and (ii) the arithmetic average of the three lowest sale prices for our Common Stock on The Nasdaq Capital Market during the ten trading days prior to the purchase date. If we direct Lincoln Park to purchase the maximum number of shares of Common Stock we then may sell in a Regular Purchase, then in addition to such Regular Purchase, and subject to certain conditions and limitations in the LPC Purchase Agreement, we may direct Lincoln Park to make an “accelerated purchase” of an additional amount of Common Stock that may not exceed the lesser of (i) 300% of the number of shares purchased pursuant to the corresponding Regular Purchase and (ii) 30% of the total number of shares of our Common Stock traded on The Nasdaq Capital Market during a specified period on the applicable purchase date as set forth in the Purchase Agreement. Under certain circumstances and in accordance with the Purchase Agreement, the Company may direct Lincoln Park to purchase shares in multiple accelerated purchases on the same trading day. The Purchase Agreement prohibits us from issuing or selling to Lincoln Park under the Purchase Agreement: (i) in excess of 6,688,588 shares of our Common Stock (the “Exchange Cap”), unless we obtain stockholder approval to issue shares in excess of the Exchange Cap or the average price of all applicable sales of our Common Stock to Lincoln Park under the LPC Purchase Agreement equal or exceed the lower of (a) the Nasdaq Official Closing Price (as defined in the Purchase Agreement) immediately preceding the execution of the LPC Purchase Agreement or (b) the average of the five Nasdaq Official Closing Prices for the Common Stock immediately preceding the execution of the LPC Purchase Agreement, as adjusted in accordance with the rules of The Nasdaq Capital Market, and (ii) any shares of our Common Stock if those shares, when aggregated with all other shares of our Common Stock then beneficially owned by Lincoln Park and its affiliates would result in Lincoln Park and its affiliates having beneficial ownership of more than 9.99% of the then total outstanding shares of our Common Stock. The LPC Purchase Agreement does not limit our ability to raise capital from other sources at our sole discretion, except that we may not enter into any equity line or similar transaction for 36 months, other than an “at-the-market” offering. The LPC Purchase Agreement and the Registration Rights Agreement contain customary representations, warranties and agreements of us and Lincoln Park, indemnification rights and other obligations of the parties. We have the right to terminate the Purchase Agreement at any time on one business day’s notice to Lincoln Park, at no cost to us. As consideration for entering into the Purchase Agreement, we issued 437,828 shares of our Common Stock to Lincoln Park (the “LPC Commitment Shares”). We will not receive any cash proceeds from the issuance of the LPC Commitment Shares. Also pursuant to the LPC Purchase Agreement, Lincoln Park agreed to an initial purchase of 1,000,000 shares of our Common Stock for an aggregate purchase price of $1,000,000 or $1.00 per share. Lincoln Park has covenanted not to cause or engage in any manner whatsoever, any direct or indirect short selling or hedging of our shares of Common Stock. During 2020, the Company sold and issued an aggregate of 3.3 million shares, including the LPC Commitment Shares, under the LPC Purchase Agreement, receiving approximately $2.2 million in gross proceeds. The Company sent a letter to Lincoln Park terminating the LPC Offering effective January 21, 2021. The Company did not sell any shares under the LPC Purchase Agreement in 2021. Aspire Purchase Agreement On August 31, 2018, the Company entered into a common stock purchase agreement (the “2018 Aspire Purchase Agreement”) with Aspire Capital Fund, LLC (“Aspire Capital”) which provides that, upon the terms and subject to the conditions and limitations set forth therein, Aspire Capital was committed to purchase up to an aggregate of $15.0 million of shares of the Company’s common stock over the 24-month term of the 2019 Aspire Purchase Agreement. During 2018, the Company sold and issued an aggregate of 0.1 million shares under the 2018 Aspire Purchase Agreement, receiving approximately $0.2 million. During 2019, the Company sold and issued an aggregate of 3.3 million shares under the 2018 Aspire Purchase Agreement, receiving approximately $6.3 million. As a result of the Company and Aspire entering into a new purchase agreement on October 28, 2019 (the “2019 Aspire Purchase Agreement”) discussed in the next paragraph, the 2018 Aspire Purchase Agreement was terminated. The 2019 Aspire Purchase Agreement provided that, upon the terms and subject to the conditions and limitations set forth therein, Aspire Capital was committed to purchase up to an aggregate of $10.0 million of shares of the Company’s common stock over the 24-month term of the 2019 Aspire Purchase Agreement. During 2019, the Company sold and issued an aggregate of 0.5 million shares under the 2019 Aspire Purchase Agreement, receiving approximately $0.7 million. During the first quarter of 2020 through March 5, 2020 when the Company delivered notice to Aspire terminating the 2019 Aspire Purchase Agreement, the Company sold 1.0 million shares of common stock under the Aspire Purchase Agreement, receiving approximately $1.6 million in additional gross proceeds. January 2021 Registered Direct Offering On January 22, 2021, the Company entered into a Securities Purchase Agreement (the “January 2021 Purchase Agreement”) with several institutional investors, pursuant to which the Company agreed to issue and sell, in a registered direct offering (the “January 2021 Offering”), an aggregate of 25,925,925 shares of the Company’s common stock at an offering price of $1.35 per share for gross proceeds of approximately $35 million before the deduction of the Placement Agents (as defined below) fee and offering expenses. The January 2021 Purchase Agreement contains customary representations, warranties and agreements by the Company and customary conditions to closing. The closing of the January 2021 Offering occurred on January 26, 2021. In connection with the January 2021 Offering, the Company entered into a placement agent agreement (the “January 2021 Placement Agent Agreement”) with A.G.P./Alliance Global Partners (together with Brookline Capital Markets, the “January 2021 Placement Agents”) pursuant to which the Company agreed to pay the January 2021 Placement Agents a cash fee equal to 7% of the aggregate gross proceeds raised from the sale of the securities sold in the January 2021 Offering and reimburse the January 2021 Placement Agents for certain of their expenses in an amount not to exceed $82,500. The January 2021 Placement Agent Agreement contains customary representations, warranties and agreements by the Company, customary conditions to closing, indemnification obligations of the Company and the January 2021 Placement Agents, including for liabilities under the Securities Act, other obligations of the parties and termination provisions. Under the January 2021 Purchase Agreement and January 2021 Placement Agent Agreement, the Company and its subsidiary are prohibited, for a period of 90 days after the closing, from issuing, entering into any agreement to issue or announcing the issuance or proposed issuance of any shares of common stock or any other securities that are at any time convertible into, or exercisable or exchangeable for, or otherwise entitle the holder thereof to receive common stock, without the prior written consent of the placement agents or the investors participating in the offering, subject to specific exceptions.

Stock-Based Compensation

Stock-Based Compensation	12 Months Ended
	Dec. 31, 2020
Share-based Payment Arrangement [Abstract]
Stock-Based Compensation	11. STOCK-BASED COMPENSATION The Company has long-term compensation plans that permit the granting of equity-based awards in the form of stock options, restricted stock, restricted stock units, stock appreciation rights, other stock awards, and performance awards. At the 2018 Annual Stockholders Meeting of the Company held on May 15, 2018, stockholders approved the Celsion Corporation 2018 Stock Incentive Plan (the “2018 Plan”). The 2018 Plan, as adopted, permits the granting of 2,700,000 shares of Celsion common stock as equity awards in the form of incentive stock options, nonqualified stock options, restricted stock, restricted stock units, stock appreciation rights, other stock awards, performance awards, or in any combination of the foregoing. At the 2019 Annual Stockholders Meeting of the Company held on May 14, 2019, stockholders approved an amendment to the 2018 Plan whereby the Company increased the number of common stock shares available by 1,200,000 to a total of 3,900,000 under the 2018 Plan, as amended. Prior to the adoption of the 2018 Plan, the Company had maintained the Celsion Corporation 2007 Stock Incentive Plan (the “2007 Plan”). At the 2020 Annual Stockholders Meeting of the Company held on June 15, 2020, stockholders approved an amendment to the 2018 Plan, as previously amended, whereby the Company increased the number of shares of common stock available by 2,500,000 to a total of 6,400,000 under the 2018 Plan, as amended. The Company has issued stock awards to employees and directors in the form of stock options and restricted stock. Options are generally granted with strike prices equal to the fair market value of a share of Celsion common stock on the date of grant. Incentive stock options may be granted to purchase shares of common stock at a price not less than 100% of the fair market value of the underlying shares on the date of grant, provided that the exercise price of any incentive stock option granted to an eligible employee owning more than 10% of the outstanding stock of Celsion must be at least 110% of such fair market value on the date of grant. Only officers and key employees may receive incentive stock options. Option and restricted stock awards vest upon terms determined by the Compensation Committee of the Board of Directors and are subject to accelerated vesting in the event of a change of control or certain terminations of employment. The Company issues new shares to satisfy its obligations from the exercise of options or the grant of restricted stock awards. On September 28, 2018, and again on February 19, 2019, the Compensation Committee of the Board of Directors approved the grant of (i) inducement stock options (the “Inducement Option Grants”) to purchase a total of 164,004 and 140,004 shares of Celsion common stock, respectively and (ii) inducement restricted stock awards (the “Inducement Stock Grants”) totaling 19,000 and 13,000 shares of Celsion common stock to five new employees collectively. Each award has a grant date of the date of grant. Each Inducement Option Grant has an exercise price per share equal to $2.77 and $2.18 which represents the closing price of Celsion’s common stock as reported by Nasdaq on September 28, 2018 and February 19, 2019, respectively. Each Inducement Option Grant will vest over three years, with one-third vesting on the one-year anniversary of the employee’s first day of employment with the Company and one-third vesting on the second and third anniversaries thereafter, subject to the new employee’s continued service relationship with the Company on each such date. Each Inducement Option Grant has a ten-year term and is subject to the terms and conditions of the applicable stock option agreement. Each of Inducement Stock Grant vested on the one-year anniversary of the employee’s first day of employment with the Company is subject to the new employee’s continued service relationship with the Company through such date and is subject to the terms and conditions of the applicable restricted stock agreement. As of December 31, 2020, there were a total of 6,505,924 shares of Celsion common stock reserved for issuance under the 2018 Plan, which were comprised of 4,484,721 shares of Celsion common stock subject to equity awards previously granted under the 2018 Plan and 2007 Plan and 2,018,453 shares of Celsion common stock available for future issuance under the 2018 Plan. As of December 31, 2020, there were a total of 140,004 shares of Celsion common stock subject to outstanding inducement awards. Total compensation cost related to stock options and restricted stock awards was approximately $1.9 million and $2.3 million during 2020 and 2019, respectively. Of these amounts, $0.8 million and $0.9 million was charged to research and development expenses during 2020 and 2019, respectively, and $1.1 million and $1.4 million was charged to general and administrative expenses during 2020 and 2019, respectively. In connection with the Company’s annual 2019 bonus program, the Company issued 429,855 shares of common stock from the 2018 Stock Incentive Plan in lieu of paying cash for 50% of the annual bonus awards. These amounts were fully accrued for in the consolidated financial statements for the year ended December 31, 2019. A summary of stock option awards as of December 31, 2020 and changes during the two-year period ended December 31, 2020 is presented below: Stock Options Number Outstanding Weighted Average Exercise Price Weighted Average Remaining Contractual Term (years) Aggregate Intrinsic Value Outstanding at January 1, 2019 3,148,743 $ 2.67 Options granted 1,250,754 $ 2.00 Options canceled or expired (67,355 ) $ 2.50 Outstanding at December 31, 2019 4,332,142 $ 2.63 Options granted 670,250 $ 3.41 Options exercised (140,864 ) $ 2.12 Options canceled or expired (236,803 ) $ 2.14 Outstanding at December 31, 2020 4,624,725 $ 2.77 7.8 $ 5,882 Exercisable at December 31, 2020 3,351,086 $ 2.80 7.4 $ 750 A summary of the status of the Company’s non-vested restricted stock awards as of December 31, 2020 and changes during the two-year period ended December 31, 2020, is presented below: Restricted Stock Number Outstanding Weighted Average Grant Date Fair Value Non-vested stock awards outstanding at January 1, 2019 22,500 $ 2.72 Granted 29,250 $ 1.99 Vested and issued (5,000 ) $ 2.14 Forfeited (38,000 ) $ 2.48 Non-vested stock awards outstanding at December 31, 2019 8,750 $ 1.59 Granted 431,605 $ 1.16 Vested and issued (434,105 ) $ 1.16 Forfeited (3,500 ) $ 1.59 Non-vested stock awards outstanding at December 31, 2020 2,750 $ 0.98 A summary of stock options outstanding at December 31, 2020 by price range is as follows: Options Outstanding Options Exercisable Range of Exercise Prices Number Weighted Average Remaining Contractual Term (in years) Weighted Average Exercise Price Number Weighted Average Remaining Contractual Term (in years) Weighted Average Exercise Price Up to $2.00 429,667 8.8 $ 1.64 147,276 8.8 $ 1.66 $2.00 to $5.00 4,130,723 7.7 $ 2.64 3,139,475 7.3 $ 2.53 Above $5.00 to $81.90 64,335 5.2 $ 18.81 64,335 5.2 $ 18.81 4,624,725 3,351,086 The fair values of stock options granted were estimated at the date of grant using the Black-Scholes option pricing model. The Black-Scholes model was originally developed for use in estimating the fair value of traded options, which have different characteristics from Celsion’s stock options. The model is also sensitive to changes in assumptions, which can materially affect the fair value estimate. The Company used the following assumptions for determining the fair value of options granted under the Black-Scholes option pricing model: Year Ended December 31, 2020 2019 Risk-free interest rate 0.65% to 1.33 % 2.82 to 3.02 % Expected volatility 100.4% to 109.1 % 101.3 to 106.2 % Expected life (in years) 7.5 to 10.0 7.5 to 9.3 Expected dividend yield 0.0 % 0.0 % Expected volatilities utilized in the model are based on historical volatility of the Company’s stock price. As of December 31, 2020, there was $1.4 million of total unrecognized compensation cost related to non-vested stock-based compensation arrangements. That cost is expected to be recognized over a weighted-average period of 1.1 years.

Earn-out Milestone Liability

Earn-out Milestone Liability	12 Months Ended
	Dec. 31, 2020
Hercules Warrant [Member]
Earn-out Milestone Liability	12. EARN-OUT MILESTONE LIABILITY The total aggregate purchase price for the EGEN Acquisition included potential future Earn-out Payments contingent upon achievement of certain milestones. The difference between the aggregate $30.4 million in future Earn-out Payments and the $13.9 million included in the fair value of the acquisition consideration at June 20, 2014 was based on the Company’s risk-adjusted assessment of each milestone (10% to 67%) and utilizing a discount rate based on the estimated time to achieve the milestone (1.5 to 2.5 years). The earn-out milestone liability will be fair valued at the end of each quarter and any change in their value will be recognized in the financial statements. On March 28, 2019, the Company and EGWU, Inc, entered into the Amended Asset Purchase Agreement. Pursuant to the Amended Asset Purchase Agreement, payment of the earnout milestone liability related to the Ovarian Cancer Indication of $12.4 million has been modified. The Company has the option to make the payment as follows: a) $7.0 million in cash within 10 business days of achieving the milestone; or b) $12.4 million in cash, common stock of the Company, or a combination of either, within one year of achieving the milestone. The Company provided EGWU, Inc. 200,000 warrants to purchase common stock at a strike price of $0.01 per warrant share as consideration for entering into this amended agreement. The warrant shares have no expiration and were fair valued at $2.00 using the closing price of a share of Celsion stock on the date of issuance offset by the exercise price and recorded as a non-cash expense in the income statement and were classified as equity on the balance sheet. In October of 2020, EGWU, Inc. elected to receive 197,260 shares through a non-cash conversion exercised all 200,000 warrant shares. At December 31, 2020, the Company fair valued the earn-out milestone liability at $7.0 million and recognized a non-cash charge of $1.3 million during 2020 as a result of the change in the fair value of earn-out milestone liability of $5.7 million at December 31, 2019. In assessing the earnout milestone liability at December 31, 2020, the Company fair valued each of the two payment options per the Amended Asset Purchase Agreement and weighted them at 50% and 50% probability for the $7.0 million and the $12.4 million payments, respectively. At December 31, 2019, the Company fair valued the earn-out milestone liability at $5.7 million and recognized a non-cash gain of $3.2 million during 2019 as a result of the change in the fair value of earn-out milestone liability of $8.9 million at December 31, 2018. In assessing the earnout milestone liability at December 31, 2019, the Company fair valued each of the two payment options per the Amended Asset Purchase Agreement and weighted them at 80% and 20% probability for the $7.0 million and the $12.4 million payments, respectively. The following is a summary of the changes in the earn-out milestone liability for 2019 and 2020: Balance at January 1, 2019 $ 8,907,664 Non-cash gain from the adjustment for the change in fair value included in 2019 net loss (3,189,955 ) Balance at December 31, 2019 5,717,709 Non-cash loss from the adjustment for the change in fair value included in 2020 net loss 1,300,291 Balance at December 31, 2020 $ 7,018,000

Warrants

Warrants	12 Months Ended
	Dec. 31, 2020
Warrants and Rights Note Disclosure [Abstract]
Warrants	13. WARRANTS Following is a summary of all warrant activity for the two years ended December 31, 2020: Warrants Number of Warrants Issued Weighted Average Exercise Price Warrants outstanding at January 1, 2019 1,593,162 $ 5.36 Warrants issued during 2019 (see Note 12) 200,000 $ 0.01 Warrants expired during 2019 (1,167,064 ) $ 6.32 Warrants outstanding at December 31, 2019 626,098 $ 1.87 Warrants issued during 2020 3,522,525 $ 1.21 Warrants exercised during 2020 (see Note 12) (200,000 ) $ 0.01 Warrants cancelled during 2020 (95,057 ) $ 2.63 Warrants outstanding and exercisable at December 31, 2020 3,853,566 $ 1.35 Aggregate intrinsic value of outstanding warrants at December 31, 2020 $ -0- Weighted average remaining contractual terms (years) 4.8 In connection with the February 2020 Registered Direct financing (Note 10), the Company issued warrants to purchase 3.2 million shares of common stock in February 2020. In connection with the Horizon Credit Agreement Amendment, the Company cancelled warrants to purchase 95,057 shares of common stock and issued warrants to purchase 247,525 shares of common stock in August 2020. Pursuant to a consulting agreement dated September 21, 2020, the Company issued warrants to purchase 75,000 shares of common stock vesting immediately and having a 4-year term. The shares underlying these warrants are unregistered and have a strike price of $0.79 per share. The Company fair valued these warrants $0.60 per share, recognizing $45,000 as professional fee expense. Warrants to purchase 1,167,064 shares of common stock expired during 2019.

Celsion Employee Benefit Plans

Celsion Employee Benefit Plans	12 Months Ended
	Dec. 31, 2020
Postemployment Benefits [Abstract]
Celsion Employee Benefit Plans	14. CELSION EMPLOYEE BENEFIT PLANS Celsion maintains a defined-contribution plan under Section 401(k) of the Internal Revenue Code. The plan covers substantially all employees over the age of 21. Participating employees may defer a portion of their pretax earnings, up to the IRS annual contribution limit. The Company makes a matching contribution up to a maximum of 3% of an employee’s annual salary. The Company’s total matching contributions for the years ended December 31, 2020 and 2019 was $111,000 and $106,000, respectively. During 2020, the Company also provided a discretionary contribution totaling $178,000 which represented 6% of each eligible participant’s annual salary in 2020. This amount was paid in January 2021.

Leases

Leases	12 Months Ended
	Dec. 31, 2020
Leases [Abstract]
Leases	15. LEASES In 2011, the Company executed a lease (the “Lease”) with Brandywine Operating Partnership, L.P. (Brandywine), a Delaware limited partnership for a 10,870 square foot premises located in Lawrenceville, New Jersey and relocated its offices to Lawrenceville, New Jersey from Columbia, Maryland. The Lease had an initial term of 66 months. In late 2015, Lenox Drive Office Park LLC, purchased the real estate and office building and assumed the Lease. This Lease was set to expire on April 30, 2017. In April 2017, the Company and the landlord amended the Lease effective May 1, 2017. The 1 st st st th st nd nd In connection with the EGEN Asset Purchase Agreement in June 2014, the Company assumed the existing lease with another landlord for an 11,500 square foot premises located in Huntsville Alabama. In January 2018, the Company and the Huntsville landlord entered into a new 60-month lease which reduced the premises to 9,049 square feet with rent payments of approximately $18,100 per month. As previously mentioned in Note 4, we adopted ASC Topic 842 on January 1, 2019 using the modified retrospective transition method for all lease arrangements at the beginning of the period of adoption. Results for reporting periods beginning January 1, 2019 are presented under ASC Topic 842, while prior period amounts were not adjusted and continue to be reported in accordance with our historic accounting under Topic 840, Leases. The standard had a material impact on our Consolidated Condensed Balance Sheet but had no impact on our consolidated net earnings and cash flows. The most significant impact of adopting ASC Topic 842 was the recognition of the right-of-use (ROU) asset and lease liabilities for operating leases, which are presented in the following three-line items on the Consolidated Condensed Balance Sheet: (i) operating lease right-of-use asset; (ii) current operating lease liabilities; and (iii) operating lease liabilities. Therefore, on date of adoption of ASC Topic 842, the Company recognized a ROU asset of $1.4 million, operating lease liabilities, current and non-current collectively, of $1.5 million and reduced other liabilities by approximately $0.1 million. We elected the package of practical expedients for leases that commenced before the effective date of ASC Topic 842 whereby we elected to not reassess the following: (i) whether any expired or existing contracts contain leases; (ii) the lease classification for any expired or existing leases; and (iii) initial direct costs for any existing leases. In addition, we have lease agreements with lease and non-lease components, and we have elected the practical expedient for all underlying asset classes and account for them as a single lease component. We have no finance leases. We determine if an arrangement is a lease at inception. We have operating leases for office space and research and development facilities. Neither of our leases include options to renew, however, one contains an option for early termination. We considered the option of early termination in measurement of right-of-use assets and lease liabilities and we determined it is not reasonably certain to be terminated. In connection with the 2 nd For the year ending 2021 $ 530,734 2022 535,579 2023 and thereafter 233,117 Subtotal future lease payments 1,299,430 Less imputed interest (155,712 ) Total lease liabilities $ 1,143,718 Weighted average remaining life 2.46 years Weighted average discount rate 9.98 % For 2020, operating lease expense was $522,380 and cash paid for operating leases included in operating cash flows was $525,809. For 2019, operating lease expense was $522,380 and cash paid for operating leases included in operating cash flows was $485,848.

Commitments and Contingencies

Commitments and Contingencies	12 Months Ended
	Dec. 31, 2020
Commitments and Contingencies Disclosure [Abstract]
Commitments and Contingencies	16. COMMITMENTS AND CONTINGENCIES On September 20, 2019, a purported stockholder of the Company filed a derivative and putative class action lawsuit against the Company and certain officers and directors (the “Shareholder Action”). The Company was a defendant in this derivative and putative class action lawsuit in the Superior Court of New Jersey, Chancery Division, filed by a shareholder against the Company (as both a class action defendant and nominal defendant), and certain of its officers and directors (the “Individual Defendants”), with the caption O’Connor v. Braun et al., Docket No. MER-C-000068-19 On April 24, 2020, the Company, the Individual Defendants, and the plaintiff (the “Parties”) entered into a Settlement Agreement and Release (the “Settlement Agreement”), which memorializes the terms of the Parties’ settlement of the Shareholder Action (the “Settlement”). The Settlement calls for repricing of certain stock options and payment of plaintiff legal fees of $187,500. On July 24, 2020, the Court issued an order approving the Parties’ proposed form of notice to shareholders regarding the Settlement. A hearing was held on September 8, 2020 whereby the Court issued a final approval approving the Settlement. Pursuant to the Settlement, the Company paid $187,500 on October 1, 2020. Without admitting the validity of any of the claims asserted in the Shareholder Action, or any liability with respect thereto, and expressly denying all allegations of wrongdoing, fault, liability, or damage against the Company and the Individual Defendants arising out of any of the conduct, statements, acts or omissions alleged, or that could have been alleged, in the Shareholder Action, the Company and the Individual Defendants concluded that it was desirable that the claims be settled on the terms and subject to the conditions set forth in the Settlement Agreement. The Company and the Individual Defendants entered into the Settlement Agreement for settlement purposes only and solely to avoid the cost and disruption of further litigation. On October 29, 2020, a putative securities class action was filed against the Company and certain of its officers and directors (the “Spar Individual Defendants”) in the U.S. District Court for the District of New Jersey, captioned Spar v. Celsion Corporation, et al. ® In February 2021, a derivative shareholder lawsuit was filed against the Company, as the nominal defendant, and certain of its directors and officers as defendants in the U.S. District Court for the District of New Jersey, captioned Fidler v. Michael H. Tardugno et al. ®.

Licenses of Intellectual Proper

Licenses of Intellectual Property and Patents	12 Months Ended
	Dec. 31, 2020
Intangible Assets, Net (Including Goodwill) [Abstract]
Licenses of Intellectual Property and Patents	17. LICENSES OF INTELLECTUAL PROPERTY AND PATENTS On November 10, 1999, the Company entered into a license agreement with Duke University (“Duke”) under which the Company received worldwide exclusive rights (subject to certain exceptions) to commercialize and use Duke’s thermally sensitive liposome technology. The license agreement contains annual royalty and minimum payment provisions due on net sales. The agreement also required milestone-based royalty payments measured by various events, including product development stages, FDA applications and approvals, foreign marketing approvals and achievement of significant sales. However, in lieu of such milestone-based cash payments, Duke agreed to accept shares of the Company’s common stock to be issued in installments at the time each milestone payment is due, with each installment of shares to be calculated at the average closing price of the common stock during the 20 trading days prior to issuance. The total number of shares issuable to Duke under these provisions is subject to adjustment in certain cases, and Duke has piggyback registration rights for public offerings taking place more than one year after the effective date of the license agreement. On January 31, 2003, the Company issued 253,691 shares of common stock to Duke University valued at $2.2 million as payment for milestone-based royalties under this license agreement. An amendment to the Duke license agreement contains certain development and regulatory milestones, and other performance requirements that the Company has met with respect to the use of the licensed technologies. The Company will be obligated to make royalty payments based on sales to Duke upon commercialization, until the last of the Duke patents expire. For the years ended December 31, 2020 and 2019, the Company has not incurred any expense under this agreement and will not incur any future liabilities until commercial sales commence. Under the November 1999 license agreement with Duke, the Company has rights to the thermally sensitive liposome technology, including Duke’s U.S. patents covering the technology as well as all foreign counterparts and related pending applications. Foreign counterpart applications have been issued in the EU, Hong Kong, Australia and Canada and have been allowed in Japan. The EU patent has been validated in Austria, Belgium, France, Germany, Great Britain, Italy, Luxembourg, Monaco, Spain and Switzerland. In addition, the Duke license agreement provides the Company with rights to multiple issued U.S. patents related to the formulation, method of making and use of heat sensitive liposomes. The Company’s rights under the license agreement with Duke extend for the life of the last-to-expire of the licensed patents. In addition to the rights available to the Company under completed or pending license agreements, the Company is actively pursuing patent protection for technologies developed by the Company. Among these patents is a family of a pending US, and international issued patents, which seek to protect the Company’s proprietary method of storing ThermoDox ® Finally, through proprietary information agreements with employees, consultants and others, the Company seeks to protect its own proprietary know-how and trade secrets. The Company cannot offer assurances that these confidentiality agreements will not be breached, that the Company will have adequate remedies for any breach, or that these agreements, even if fully enforced, will be adequate to prevent third-party use of the Company’s proprietary technology. Similarly, the Company cannot guarantee that technology rights licensed to it by others will not be successfully challenged or circumvented by third parties, or that the rights granted will provide the Company with adequate protection.

Technology Development and Lice

Technology Development and Licensing Agreements	12 Months Ended
	Dec. 31, 2020
Technology Development And Licensing Agreements
Technology Development and Licensing Agreements	18. TECHNOLOGY DEVELOPMENT AND LICENSING AGREEMENTS On May 7, 2012, the Company entered into a long-term commercial supply agreement with Zhejiang Hisun Pharmaceutical Co. Ltd. (Hisun) for the production of ThermoDox ® ® ® ® ® On January 18, 2013, we entered into a technology development contract with Hisun, pursuant to which Hisun paid us a non-refundable research and development fee of $5 million to support our development of ThermoDox ® ® ® ®

Subsequent Events

Subsequent Events	12 Months Ended
	Dec. 31, 2020
Subsequent Events [Abstract]
Subsequent Events	19. SUBSEQUENT EVENTS The Company has evaluated events subsequent to the date of the balance sheet through the date of these financial statements. As more fully discussed in Note 2, the Company issued a letter to shareholders on February 11, 2021 stating that the Company will be notifying all clinical sites to discontinue following patients in the OPTIMA Study. As more fully discussed in Note 10, the Company collectively has sold 34.3 million shares of common stock for gross proceeds of $43.4 million in 2021 through the date that these statements are made available.

Summary of Significant Accoun_2

Summary of Significant Accounting Policies (Policies)	12 Months Ended
	Dec. 31, 2020
Accounting Policies [Abstract]
Description of Business	Description of Business Celsion Corporation (“Celsion” and the “Company”) is a fully integrated, clinical stage biotechnology company focused on advancing a portfolio of innovative treatments including DNA-based immunotherapies, next generation vaccines and directed chemotherapies through clinical trials and eventual commercialization. The Company’s product pipeline includes GEN-1, a DNA-based immunotherapy for the localized treatment of ovarian cancer and ThermoDox ®
Basis of Presentation	Basis of Presentation The accompanying consolidated financial statements of Celsion have been prepared in accordance with generally accepted accounting principles (“GAAP”) in the U.S. and include the accounts of the Company and CLSN Laboratories, Inc. All significant intercompany balances and transactions have been eliminated in consolidation. The preparation of financial statements in conformity with GAAP requires management to make judgments, estimates, and assumptions that affect the amount reported in the Company’s financial statements and accompanying notes. Actual results could differ materially from these estimates. Events and conditions arising subsequent to the most recent balance sheet date through the date of the issuance of these consolidated financial statements have been evaluated for their possible impact on the financial statements and accompanying notes. No events and conditions would give rise to any information that required accounting recognition or disclosure in the financial statements other than those arising in the ordinary course of business.
Use of Estimates	Use of Estimates The preparation of financial statements in conformity with US GAAP requires the Company to make estimates and assumptions that affect the reported amounts of assets and liabilities and disclosure of contingent assets and liabilities at the date of the financial statements and the reported amounts of expenses during the reporting period. On an ongoing basis, the Company evaluates its estimates using historical experience and other factors, including the current economic environment. Significant items subject to such estimates are assumptions used for purposes of determining stock-based compensation, the fair value of the earn-out milestone liabilities, estimates for contingent liabilities, if any, and accounting for valuation of in-process research and development assets and goodwill evaluation. Management believes its estimates to be reasonable under the circumstances. Actual results could differ significantly from those estimates. Significant estimates in these financials are the valuation of options granted and valuation methods used to determine the recoverability of goodwill and other intangible assets.
Revenue Recognition	Revenue Recognition The Company’s sole revenue stream is related to the Hisun agreement described in Note 18. There were no accounts receivable as of December 31, 2020 or 2019. Contract liabilities from the Hisun agreement amounted to $1,000,000 and $1,500,000 at December 31, 2020 and 2019, respectively. Contract liabilities values represent the value of cash received before the services were provided.
Cash and Cash Equivalents	Cash and Cash Equivalents Cash and cash equivalents include cash on hand and investments purchased with an original maturity of three months or less. A portion of these funds are not covered by FDIC insurance.
Fair Value of Financial Instruments	Fair Value of Financial Instruments The carrying values of investment securities approximate their respective fair values. Management believes that the carrying amounts of the Company’s investment securities, including cash and cash equivalents, accounts payable and accrued expenses, approximate fair value due to the short-term nature of those instruments. Short-term investments are recorded at their estimated fair value.
Short Term Investments	Short Term Investments The Company classifies its investments in debt securities with readily determinable fair values as investments available-for-sale in accordance with Accounting Standards Codification (“ASC”) 320, Investments - Debt and Equity Securities. Available-for-sale securities consist of debt securities not classified as trading securities or as securities to be held to maturity. The Company has classified all of its investments as available-for-sale. Unrealized holding gains and losses on available-for-sale securities are reported as a net amount in accumulated other comprehensive gain or loss in stockholders’ equity until realized. Gains and losses on the sale of available-for-sale securities are determined using the specific identification method. The Company’s short-term investments consist of corporate bonds.
Property and Equipment	Property and Equipment Property and equipment are stated at cost less accumulated depreciation and amortization. Depreciation is provided over the estimated useful lives of the related assets, ranging from three to seven years, using the straight-line method. Amortization is recognized over the lesser of the life of the asset or the lease term. Major renewals and improvements are capitalized at cost and ordinary repairs and maintenance are charged against operating expenses as incurred. Depreciation expense was approximately $130,000 and $128,500 for the years ended December 31, 2020 and 2019, respectively. The Company reviews property and equipment for impairment whenever events or changes in circumstances indicate that the carrying amount of an asset may not be recoverable. An asset is considered impaired if its carrying amount exceeds the future net undiscounted cash flows that the asset is expected to generate. If such asset is considered to be impaired, the impairment recognized is the amount by which the carrying amount of the asset, if any, exceeds its fair value determined using a discounted cash flow model. There was no impairment of property or equipment during 2020 or 2019.
Deposits	Deposits Deposits include real property security deposits and other deposits which are contractually required and of a long-term nature.
In-Process Research and Development, Other Intangible Assets and Goodwill	In-Process Research and Development, Other Intangible Assets and Goodwill During 2014, the Company acquired certain assets of EGEN, Inc. As more fully described in Note 5, the acquisition was accounted for under the acquisition method of accounting which required the Company to perform an allocation of the purchase price to the assets acquired and liabilities assumed. Under the acquisition method of accounting, the total purchase price is allocated to net tangible and intangible assets and liabilities based on their estimated fair values as of the acquisition date.
Impairment or Disposal of Long-Lived Assets	Impairment or Disposal of Long-Lived Assets The Company assesses the impairment of its long-lived assets under accounting standards for the impairment or disposal of long-lived assets whenever events or changes in circumstances indicate that the carrying value may not be recoverable. For long-lived assets to be held and used, the Company recognizes an impairment loss only if its carrying amount is not recoverable through its undiscounted cash flows and measures the impairment loss based on the difference between the carrying amount and fair value. See Note 5 for information on impairment losses of its in -
Comprehensive Income (Loss)	Comprehensive Income (Loss) ASC 220, Comprehensive Income 220
Research and Development	Research and Development Research and development costs are expensed as incurred. Equipment and facilities acquired for research and development activities that have alternative future uses are capitalized and charged to expense over their estimated useful lives.
Net Loss Per Common Share	Net Loss Per Common Share Basic and diluted net loss per common share was computed by dividing net loss for the year by the weighted average number of shares of common stock outstanding, both basic and diluted, during each period. The impact of common stock equivalents has been excluded from the computation of diluted weighted average common shares outstanding in periods where there is a net loss, as their effect is anti-dilutive. For the years ended December 31, 2020 and 2019, the total number of shares of common stock issuable upon exercise of warrants and equity awards is 8,481,041 and 4,766,990, respectively. Warrants with an exercise price of $0.01 (as more fully described in Note 13 of these financial statements) exercisable for 200,000 shares of common stock issued in March 2019 and exercised for 197,260 shares of stock through a cashless conversion in October 2020, were considered issued in calculating basic loss per share for each year. For the year ended December 31, 2020 and 2019, diluted loss per common share is the same as basic loss per common share as all options and all other warrants that were convertible into shares of the Company’s common stock were excluded from the calculation of diluted earnings attributable to common stockholders per common share as their effect would be anti-dilutive.
Income Taxes	Income Taxes Income taxes are accounted for under the asset and liability method. Under this method, deferred tax assets and liabilities are recognized for the future tax consequences attributable to differences between the financial statement carrying amounts of existing assets and liabilities and their respective tax bases and operating loss and tax credit carry forwards. Deferred tax assets and liabilities are measured using enacted tax rates expected to apply to taxable income in the years in which those temporary differences are expected to be recovered or settled. The effect on deferred tax asset and liabilities of a change in tax rates is recognized in results of operations in the period that the tax rate change occurs. Valuation allowances are established, when necessary, to reduce deferred tax assets to the amount expected to be realized. In accordance with ASC 740, Income Taxes, As more fully discussed in Note 9, on February 12, 2021, the Company received approval from the New Jersey Economic Development Authority to sell $2.0 million of its New Jersey net operating losses recognizing a tax benefit for the year ended December 31, 2020 for the net proceeds (approximately $1.85 million) by reducing the deferred income tax valuation allowance. In February of 2021, the Company entered into an agreement to sell these net operating losses and expects to receive net proceeds of approximately $1.85 million by the end of the first quarter of 2021. During 2019 and 2018, the Company submitted applications to sell a portion of the Company’s State of New Jersey net operating losses as part of the Technology Business Tax Certificate Program sponsored by The New Jersey Economic Development Authority. Under the program, emerging biotechnology companies with unused NOLs and unused research and development credits are allowed to sell these benefits to other New Jersey-based companies. In 2019 and 2018, the Company sold NOLs totaling $13 million, receiving net proceeds of $1.8 million and $10.4 million, respectively. During 2021, the New Jersey State Legislature increased the maximum lifetime benefit per company from $15 million to $20 million, which will allow the Company to participate in this innovative funding program in future years.
Stock-Based Compensation	Stock-Based Compensation In March 2016, the Financial Accounting Standards Board (“FASB”) issued ASU 2016-09, Compensation-Stock Compensation
Recent Accounting Pronouncements	Recent Accounting Pronouncements From time to time, new accounting pronouncements are issued by the Financial Accounting Standards Board (“FASB”) and are adopted by us as of the specified effective date. Unless otherwise discussed, we believe that the impact of recently issued accounting pronouncements will not have a material impact on the Company’s consolidated financial position, results of operations, and cash flows, or do not apply to our operations. In February 2016, the FASB issued ASU No. 2016-02, “Leases” - Topic 842 (ASC Topic 842), which requires that lessees recognize assets and liabilities for leases with lease terms greater than twelve months in the balance sheet. Leases will be classified as either finance or operating, with classification affecting the pattern of expense recognition in the income statement. This update also requires improved disclosures to help users of financial statements better understand the amount, timing and uncertainty of cash flows arising from leases. The update became effective for fiscal years beginning after December 15, 2018, including interim reporting periods within that reporting period. We adopted ASC Topic 842 effective January 1, 2019 and elected to apply the available practical expedients and implement internal controls to enable the preparation of financial information on adoption. We identified two of our leases consisting of the New Jersey corporate office lease and the Alabama lab facility lease as being subject to ASC Topic 842. The adoption of this standard resulted in the recognition of right-of-use assets of approximately $1.4 million, related operating lease liabilities of $1.5 million and reduced other liabilities by approximately $0.1 million on the consolidated balance sheets as of January 1, 2019 with no material impact to the opening balance of retained earnings. See Note 15 for further discussions regarding the adoption of ASC Topic 842. In June 2016, the FASB issued ASU No. 2016-13, “Financial Instruments – Credit Losses (Topic 326): Measurement of Credit Losses on Financial Instruments”, which modifies the measurement of expected credit losses on certain financial instruments. The Company expects to adopt ASU 2016-13 in its first quarter of 2021 utilizing the modified retrospective transition method. Based on the composition of the Company’s investment portfolio and current market conditions, the adoption of ASU 2016-13 is not expected to have a material impact on its consolidated financial statements. In August 2018, the FASB issued ASU No. 2018-13, Fair Value Measurement: Disclosure Framework – Changes to the Disclosure Requirements for Fair Value Measurement In December 2019, the FASB issued ASU No. 2019-12, Income Taxes (Topic 740). The standard simplifies the accounting for incomes taxes by removing certain exceptions to the general principles in Topic 740 related to the approach for intraperiod tax allocation and the recognition of deferred tax liabilities for outside basis differences. The standard also clarifies the accounting for transactions that result in a step-up in the tax basis of goodwill. The standard also improves consistent application of and simplifies GAAP for other areas of Topic 740 by clarifying and amending existing guidance. The amendment is effective for fiscal years, and interim periods within those fiscal years, beginning after December 15, 2020. Early adoption is permitted. The Company does not believe that the adoption of this standard will have an impact on its consolidated financial statements.

Investments in Debt Securitie_2

Investments in Debt Securities Available for Sale (Tables)	12 Months Ended
	Dec. 31, 2020
Investments, Debt and Equity Securities [Abstract]
Schedule of Cost, Fair Value and Maturities of Short Term Investments	A summary of the cost, fair value and maturities of the Company’s short-term investments is as follows: December 31, 2020 December 31, 2019 Cost Fair Value Cost Fair Value Short-term investments Corporate debt securities $ - $ - $ 7,943,108 $ 7,985,886 Total $ - $ - $ 7,943,108 $ 7,985,886 December 31, 2020 December 31, 2019 Cost Fair Value Cost Fair Value Short-term investment maturities Within 3 months $ - $ - $ 7,943,108 $ 7,985,886 Between 3-12 months - - - - Total $ - $ - $ 7,943,108 $ 7,985,886
Summary of Investment Securities Gross Unrealized Gains (Losses)	The following table shows the Company’s investment in debt securities available for sale gross unrealized gains (losses) and fair value by investment category and length of time that individual securities have been in a continuous unrealized loss position at December 31, 2020 and 2019. The Company has reviewed individual securities to determine whether a decline in fair value below the amortizable cost basis is other than temporary. December 31, 2020 December 31, 2019 Available for sale securities (all unrealized holding gains and losses are less than 12 months at date of measurement) Fair Value Unrealized Holding Gains (Losses) Fair Value Unrealized Holding Gains (Losses) Investments in debt securities with unrealized gains $ - $ - $ 7,985,886 $ 42,778 Investments in debt securities with unrealized losses - - - - Total $ - $ - $ 7,985,886 $ 42,778
Summary of Net Realized Losses on Sales of Available for Sale Securities and Investment Income Interest and Dividends	Investment income, which includes net realized losses on sales of available for sale securities and investment income interest and dividends, is summarized as follows: 2020 2019 Interest and dividends accrued and paid $ 66,553 $ 442,987 Realized gains 53,354 57,895 Investment income net $ 119,907 $ 500,882

Fair Values of Financial Inst_2

Fair Values of Financial Instruments (Tables)	12 Months Ended
	Dec. 31, 2020
Fair Value Disclosures [Abstract]
Schedule of Fair Value, Assets and Liabilities Measured on Recurring Basis	Assets and liabilities measured at fair value are summarized below: Total Fair Value Quoted Prices in Active Markets for Identical Assets/Liabilities (Level 1) Significant Other Observable Inputs (Level 2) Significant Unobservable Inputs (Level 3) Assets: Recurring items as of December 31, 2020 Corporate debt securities, available for sale $ – $ – $ – $ – Non-recurring items as of December 31, 2020 In-process R&D (Note 5) $ 13,366,234 $ – $ – $ 13,366,234 Recurring items as of December 31, 2019 Corporate debt securities, available for sale $ 7,985,886 $ – $ 7,985,886 $ – Non-recurring items as of December 31, 2019 In-process R&D (Note 5) $ 15,736,491 $ – $ – $ 15,736,491 Liabilities: Recurring items as of December 31, 2020 Earn-out milestone liability (Note 12) $ 7,018,000 $ – $ – $ 7,017,000 Recurring items as of December 31, 2019 Earn-out milestone liability (Note 12) $ 5,717,709 $ – $ – $ 5,717,709

Intangible Assets (Tables)

Intangible Assets (Tables)	12 Months Ended
	Dec. 31, 2020
Intangible Assets, Net (Including Goodwill) [Abstract]
Schedule of Fair Value of Assets Acquired	Following is a summary of the net fair value of the assets acquired in the EGEN acquisition for the two years ended December 31, 2020: IPR&D Goodwill Covenant Not to Compete Balance at January 1, 2019, net $ 15,736,491 $ 1,976,101 568,292 Amortization - - (227,316 ) Impairment charge - - - Balance at December 31, 2019, net 15,736,491 1,976,101 340,976 Amortization - - (227,316 ) Impairment charge (2,370,257 ) - - Balance at December 31, 2020, net $ 13,366,234 $ 1,976,101 $ 113,660

Property and Equipment (Tables)

Property and Equipment (Tables)	12 Months Ended
	Dec. 31, 2020
Property, Plant and Equipment [Abstract]
Summary of Property and Equipment	Property and equipment at December 31, 2020 and 2019 consist of the following: December 31, 2020 2019 Machinery and equipment (5-7 year life) $ 2,832,995 $ 2,831,564 Furniture and fixtures (3-5 year life) 344,939 327,278 Leasehold improvements (5-7 year life) 343,202 343,202 3,521,136 3,502,044 Less accumulated depreciation and amortization (3,226,585 ) (3,096,681 ) Total $ 294,551 $ 405,363

Other Accrued Liabilities (Tabl

Other Accrued Liabilities (Tables)	12 Months Ended
	Dec. 31, 2020
Payables and Accruals [Abstract]
Schedule of Other Accrued Liabilities	Other accrued liabilities at December 31, 2020 and 2019 include the following: December 31, 2020 2019 Amounts due to contract research organizations and other contractual agreements $ 636,000 $ 475,440 Accrued payroll and related benefits 1,736,271 1,604,541 Accrued professional fees 66,850 204,155 Other 19,411 19,411 Total $ 2,458,532 $ 2,303,547

Notes Payable (Tables)

Notes Payable (Tables)	12 Months Ended
	Dec. 31, 2020
Debt Disclosure [Abstract]
Schedule of Future Principle Payments, Net of Unamortized Debt Discounts	Following is a schedule of future principal payments, net of unamortized debt discounts and amortized end of term charges, due on the Horizon Credit Agreement: For the year ending December 31, 2021 $ 1,190,475 2022 2,857,140 2023 and thereafter 952,385 Subtotal of future principal payments 5,000,000 Unamortized debt issuance costs, net 51,160 Total $ 5,051,160

Income Taxes (Tables)

Income Taxes (Tables)	12 Months Ended
	Dec. 31, 2020
Income Tax Disclosure [Abstract]
Schedule of Income Tax Provision (Benefit)	The income tax provision (benefit) for the years ended December 31, 2020 and 2019 consists of the following: 2020 2019 Federal Current $ - $ - Deferred - - State and Local - - Current - - Deferred (1,845,823 ) (1,816,474 ) Total $ (1,845,823 ) $ (1,816,474 )
Schedule of Effective Income Tax Rate Reconciliation	A reconciliation of the Company’s statutory tax rate to the effective rate for the years ended December 31, 2020 and 2019 is as follows: 2020 2019 Federal statutory rate 21.0 % 21.0 % State taxes, net of federal tax benefit 7.8 9.8 Permanent differences (5.3 ) (2.6 ) Other – 1.1 Change in valuation allowance and deferred rate change, net (15.5 ) (19.6 ) Effective tax rate 8.0 % 9.7 %
Schedule of Deferred Tax Assets and Liabilities	The components of the Company’s deferred tax asset as of December 31, 2020 and 2019 are as follows: December 31, 2020 2019 Net operating loss carryforwards $ 60,446,000 $ 58,243,000 Other Deferred tax assets, net 5,182,000 254,000 Subtotal 65,628,000 58,497,000 Valuation allowance (63,782,177 ) (56,677,676 ) Total deferred tax asset $ 1,845,823 $ 1,819,324

Stock-Based Compensation (Table

Stock-Based Compensation (Tables)	12 Months Ended
	Dec. 31, 2020
Share-based Payment Arrangement [Abstract]
Summary of Stock Options	A summary of stock option awards as of December 31, 2020 and changes during the two-year period ended December 31, 2020 is presented below: Stock Options Number Outstanding Weighted Average Exercise Price Weighted Average Remaining Contractual Term (years) Aggregate Intrinsic Value Outstanding at January 1, 2019 3,148,743 $ 2.67 Options granted 1,250,754 $ 2.00 Options canceled or expired (67,355 ) $ 2.50 Outstanding at December 31, 2019 4,332,142 $ 2.63 Options granted 670,250 $ 3.41 Options exercised (140,864 ) $ 2.12 Options canceled or expired (236,803 ) $ 2.14 Outstanding at December 31, 2020 4,624,725 $ 2.77 7.8 $ 5,882 Exercisable at December 31, 2020 3,351,086 $ 2.80 7.4 $ 750
Summary of Non-Vested Restricted Stock Awards	A summary of the status of the Company’s non-vested restricted stock awards as of December 31, 2020 and changes during the two-year period ended December 31, 2020, is presented below: Restricted Stock Number Outstanding Weighted Average Grant Date Fair Value Non-vested stock awards outstanding at January 1, 2019 22,500 $ 2.72 Granted 29,250 $ 1.99 Vested and issued (5,000 ) $ 2.14 Forfeited (38,000 ) $ 2.48 Non-vested stock awards outstanding at December 31, 2019 8,750 $ 1.59 Granted 431,605 $ 1.16 Vested and issued (434,105 ) $ 1.16 Forfeited (3,500 ) $ 1.59 Non-vested stock awards outstanding at December 31, 2020 2,750 $ 0.98
Summary of Stock Options Outstanding	A summary of stock options outstanding at December 31, 2020 by price range is as follows: Options Outstanding Options Exercisable Range of Exercise Prices Number Weighted Average Remaining Contractual Term (in years) Weighted Average Exercise Price Number Weighted Average Remaining Contractual Term (in years) Weighted Average Exercise Price Up to $2.00 429,667 8.8 $ 1.64 147,276 8.8 $ 1.66 $2.00 to $5.00 4,130,723 7.7 $ 2.64 3,139,475 7.3 $ 2.53 Above $5.00 to $81.90 64,335 5.2 $ 18.81 64,335 5.2 $ 18.81 4,624,725 3,351,086
Schedule of Assumptions Used to Determine Fair Value of Options Granted	The Company used the following assumptions for determining the fair value of options granted under the Black-Scholes option pricing model: Year Ended December 31, 2020 2019 Risk-free interest rate 0.65% to 1.33 % 2.82 to 3.02 % Expected volatility 100.4% to 109.1 % 101.3 to 106.2 % Expected life (in years) 7.5 to 10.0 7.5 to 9.3 Expected dividend yield 0.0 % 0.0 %

Earn-out Milestone Liability (T

Earn-out Milestone Liability (Tables)	12 Months Ended
	Dec. 31, 2020
Hercules Warrant [Member]
Schedule of Changes in Earn-out Milestone Liability	The following is a summary of the changes in the earn-out milestone liability for 2019 and 2020: Balance at January 1, 2019 $ 8,907,664 Non-cash gain from the adjustment for the change in fair value included in 2019 net loss (3,189,955 ) Balance at December 31, 2019 5,717,709 Non-cash loss from the adjustment for the change in fair value included in 2020 net loss 1,300,291 Balance at December 31, 2020 $ 7,018,000

Warrants (Tables)

Warrants (Tables)	12 Months Ended
	Dec. 31, 2020
Warrants and Rights Note Disclosure [Abstract]
Summary of Warrant Activity	Following is a summary of all warrant activity for the two years ended December 31, 2020: Warrants Number of Warrants Issued Weighted Average Exercise Price Warrants outstanding at January 1, 2019 1,593,162 $ 5.36 Warrants issued during 2019 (see Note 12) 200,000 $ 0.01 Warrants expired during 2019 (1,167,064 ) $ 6.32 Warrants outstanding at December 31, 2019 626,098 $ 1.87 Warrants issued during 2020 3,522,525 $ 1.21 Warrants exercised during 2020 (see Note 12) (200,000 ) $ 0.01 Warrants cancelled during 2020 (95,057 ) $ 2.63 Warrants outstanding and exercisable at December 31, 2020 3,853,566 $ 1.35 Aggregate intrinsic value of outstanding warrants at December 31, 2020 $ -0- Weighted average remaining contractual terms (years) 4.8

Leases (Tables)

Leases (Tables)	12 Months Ended
	Dec. 31, 2020
Leases [Abstract]
Schedule of Lease Payments and Maturity of Our Operating Lease Liabilities	Following is a table of the lease payments and maturity of our operating lease liabilities as of December 31, 2020: For the year ending 2021 $ 530,734 2022 535,579 2023 and thereafter 233,117 Subtotal future lease payments 1,299,430 Less imputed interest (155,712 ) Total lease liabilities $ 1,143,718 Weighted average remaining life 2.46 years Weighted average discount rate 9.98 %

Summary of Significant Accoun_3

Summary of Significant Accounting Policies (Details Narrative) - USD ($)	1 Months Ended				12 Months Ended
	Feb. 28, 2021	Oct. 31, 2020	Sep. 30, 2020	Mar. 31, 2019	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018	Sep. 21, 2020	Jan. 02, 2019
Accounts receivable
Depreciation						130,000	128,500
Impairment of property or equipment
Number of shares of common stock issuable upon exercise of warrants and equity awards						8,481,041	4,766,990
Warrants exercise price						$ 0.01	$ 0.01		$ 0.79
Number of shares of common stock issued in calculation basic loss per share		197,260		200,000
Right-of-use assets						$ 1,047,336	$ 1,431,640			$ 400,000
Related lease liabilities						1,143,718				1,900,000
Accounting Standards Update 2016-02 [Member]
Right-of-use assets						1,400,000				1,400,000
Related lease liabilities						1,500,000				1,500,000
Other liabilities						100,000				$ 100,000
New Jersey [Member]
Tax benefits of EDA						2,000,000
Net proceeds from sale of net operating losses			$ 2,000,000			1,850,000	13,000,000	$ 13,000,000
Proceeds from new capital							1,800,000	$ 1,040,000
New Jersey [Member] | Forecast [Member] | Minimum [Member]
Net proceeds from sale of net operating losses					$ 15,000,000
New Jersey [Member] | Forecast [Member] | Maximum [Member]
Net proceeds from sale of net operating losses					$ 20,000,000
New Jersey [Member] | Subsequent Event [Member]
Net proceeds from sale of net operating losses	$ 1,850,000
Hisun Agreement [Member]
Contract liabilities						$ 1,000,000	$ 1,500,000

Financial Condition (Details Na

Financial Condition (Details Narrative) - USD ($)	Mar. 19, 2021	Aug. 28, 2020	Feb. 28, 2021	Jan. 31, 2021	Sep. 30, 2020	Jun. 30, 2018	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Cumulated net losses								$ (312,000,341)	$ (290,516,780)
Cash and cash equivalents								17,164,177	6,875,273
Proceeds from sale of equity								43,000,000
Horizon Credit Agreement [Member] | Horizon Technology Finance Corporation [Member]
Proceeds from new capital						$ 10,000,000
Debt instrument face amount		$ 10,000,000
Horizon Credit Agreement [Member] | Horizon Technology Finance Corporation [Member] | London Interbank Offered Rate (LIBOR) [Member]
Debt instrument, interest rate						7.625%
Amendment to Horizon Credit Agreement [Member] | Horizon Technology Finance Corporation [Member]
Repayment of loans		5,000,000
Debt instrument face amount		5,000,000
Debt instrument related end term charges		$ 200,000
Capital on DemandTM Sales Agreement [Member] | Jones Trading Institutional Services, LLC [Member]
Proceeds from new capital	$ 6,900,000
Debt instrument face amount				$ 3,500,000
Proceeds from warrant exercises				$ 1,500,000
New Jersey [Member]
Net proceeds from sale of net operating losses					$ 2,000,000			1,850,000	13,000,000	$ 13,000,000
Proceeds from new capital									$ 1,800,000	$ 1,040,000
New Jersey [Member] | Maximum [Member] | LPC Purchase Agreement [Member] | Lincoln Park Capital Fund, LLC [Member]
Net proceeds from sale of net operating losses
Proceeds from sales of net operating losses								$ 1,850,000
New Jersey [Member] | Forecast [Member] | Minimum [Member]
Net proceeds from sale of net operating losses							$ 15,000,000
New Jersey [Member] | Forecast [Member] | Maximum [Member]
Net proceeds from sale of net operating losses							$ 20,000,000
New Jersey [Member] | Subsequent Event [Member]
Net proceeds from sale of net operating losses			$ 1,850,000

Investment in Debt Securities A

Investment in Debt Securities Available for Sale (Details Narrative) - USD ($)	Dec. 31, 2020	Dec. 31, 2019
Short-term investments - Fair Value		$ 7,985,886
Corporate Debt Securities [Member]
Short-term investments - Fair Value		7,985,886
Short-term Investments [Member] | Corporate Debt Securities [Member]
Short-term investments - Fair Value		$ 7,985,886

Investment in Debt Securities_2

Investment in Debt Securities Available for Sale - Schedule of Cost, Fair Value and Maturities of Short Term Investments (Details) - USD ($)	Dec. 31, 2020	Dec. 31, 2019
Short-term investments - Cost		$ 7,943,108
Short-term investments - Fair Value		7,985,886
Short-term investment maturities - Within 3 months, cost		7,943,108
Short-term investment maturities - Between 3-12 months, cost
Total, cost		7,943,108
Short-term investment maturities - Within 3 months, fair value		7,985,886
Short-term investment maturities - Between 3-12 months, fair value
Total, fair value		7,985,886
Corporate Debt Securities [Member]
Short-term investments - Cost		7,943,108
Short-term investments - Fair Value		$ 7,985,886

Investments in Debt Securitie_3

Investments in Debt Securities Available for Sale - Summary of Investment Securities Gross Unrealized Gains (Losses) (Details) - USD ($)	Dec. 31, 2020	Dec. 31, 2019
Fair Value Disclosures [Abstract]
Investments in debt securities with unrealized gains, Less than 12 months , Fair Value		$ 7,985,886
Investments in debt securities with unrealized losses, Less than 12 months, Fair Value
Investment securities - available for sale, Fair Value		7,985,886
Investments in debt securities with unrealized gains, Less than 12 months, Unrealized Holding Gains (Losses)		42,778
Investments in debt securities with unrealized losses, Less than 12 months, Unrealized Holding Gains (Losses)
Unrealized Holding Gains (Losses)		$ 42,778

Investments in Debt Securitie_4

Investments in Debt Securities Available for Sale - Summary of Net Realized Losses on Sales of Available for Sale Securities and Investment Income Interest and Dividends (Details) - USD ($)	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Fair Value Disclosures [Abstract]
Interest and dividends accrued and paid	$ 66,553	$ 442,987
Realized gains	53,354	57,895
Investment income net	$ 119,907	$ 500,882

Fair Values of Financial Inst_3

Fair Values of Financial Instruments - Schedule of Fair Value, Assets and Liabilities Measured on Recurring Basis (Details) - USD ($)	Dec. 31, 2020	Dec. 31, 2019
Investment securities, available for sale		$ 7,985,886
Earn-out milestone liability	7,018,000	5,717,709
Corporate Debt Securities [Member]
Investment securities, available for sale		7,985,886
Fair Value, Measurements, Recurring [Member] | Corporate Debt Securities [Member]
Investment securities, available for sale		7,985,886
Earn-out milestone liability	7,018,000	5,717,709
Fair Value, Measurements, Recurring [Member] | Corporate Debt Securities [Member] | Quoted Prices in Active Markets for Identical Assets/Liabilities (Level 1) [Member]
Investment securities, available for sale
Earn-out milestone liability
Fair Value, Measurements, Recurring [Member] | Corporate Debt Securities [Member] | Significant Other Observable Inputs (Level 2) [Member]
Investment securities, available for sale		7,985,886
Earn-out milestone liability
Fair Value, Measurements, Recurring [Member] | Corporate Debt Securities [Member] | Significant Unobservable Inputs (Level 3) [Member]
Investment securities, available for sale
Earn-out milestone liability	7,018,000	5,717,709
Fair Value, Measurements, Non Recurring [Member] | Inprocess R&D [Member]
Investment securities, available for sale	13,366,234	15,736,491
Fair Value, Measurements, Non Recurring [Member] | Inprocess R&D [Member] | Quoted Prices in Active Markets for Identical Assets/Liabilities (Level 1) [Member]
Investment securities, available for sale
Fair Value, Measurements, Non Recurring [Member] | Inprocess R&D [Member] | Significant Other Observable Inputs (Level 2) [Member]
Investment securities, available for sale
Fair Value, Measurements, Non Recurring [Member] | Inprocess R&D [Member] | Significant Unobservable Inputs (Level 3) [Member]
Investment securities, available for sale	$ 13,366,234	$ 15,736,491

Intangible Assets (Details Narr

Intangible Assets (Details Narrative) - USD ($)	Sep. 30, 2020	Dec. 31, 2020	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Finite-lived intangible assets, net		$ 113,660	$ 113,660	$ 340,976
2018 Aspire Purchase Agreements [Member]
Finite-lived intangible assets, net				340,976
Finite-lived intangible assets, accumulated amortization				1,250,238
Glioblastoma Multiforme Brain Cancer [Member]
Asset impairment charges				2,400,000
IPR&D Drug Technology Platforms [Member]
Asset impairment charges
IPR&D Drug Technology Platforms [Member] | Ovarian Cancer [Member]
Finite-lived intangible assets acquired			13,300,000
EGEN Inc [Member]
Asset impairment charges					$ 7,000,000
Goodwill, acquisition			2,000,000
EGEN Inc [Member] | Purchase Agreement [Member]
Finite-lived intangible assets acquired			$ 1,600,000
Finite-lived intangible asset, useful life			7 years
Amortization expense			$ 227,316	$ 227,316
Finite-lived intangible assets, net		113,660	113,660
Finite-lived intangible assets, accumulated amortization		1,477,554	1,477,554
EGEN Inc [Member] | Glioblastoma Multiforme Brain Cancer [Member]
Asset impairment charges	$ 2,400,000				$ 9,400,000
Non-cash charge		$ 2,400,000
EGEN Inc [Member] | IPR&D Drug Technology Platforms [Member]
Indefinite lived intangible assets			$ 24,200,000

Intangible Assets - Schedule of

Intangible Assets - Schedule of Fair Value of Assets Acquired (Details) - USD ($)	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Intangible assets, beginning balance	$ 340,976
Intangible assets, ending balance	113,660	$ 340,976
Covenant Not to Compete [Member]
Intangible assets, beginning balance	340,976	568,292
Amortization	(227,316)	(227,316)
Impairment charge
Intangible assets, ending balance	113,660	340,976
IPR&D [Member]
Intangible assets, beginning balance	15,736,491	15,736,491
Amortization
Impairment charge	(2,370,257)
Intangible assets, ending balance	13,366,234	15,736,491
Goodwill [Member]
Intangible assets, beginning balance	1,976,101	1,976,101
Amortization
Impairment charge
Intangible assets, ending balance	$ 1,976,101	$ 1,976,101

Property and Equipment - Summar

Property and Equipment - Summary of Property and Equipment (Details) - USD ($)	Dec. 31, 2020	Dec. 31, 2019
Property and equipment gross	$ 3,521,136	$ 3,502,044
Less accumulated depreciation and amortization	(3,226,585)	(3,096,681)
Total	294,551	405,363
Machinery and Equipment [Member]
Property and equipment gross	2,832,995	2,831,564
Furniture and Fixtures [Member]
Property and equipment gross	344,939	327,278
Leasehold Improvements [Member]
Property and equipment gross	$ 343,202	$ 343,202

Property and Equipment - Summ_2

Property and Equipment - Summary of Property and Equipment (Details) (Parenthetical)	12 Months Ended
	Dec. 31, 2020
Machinery and Equipment [Member] | Minimum [Member]
Estimated useful life	5 years
Machinery and Equipment [Member] | Maximum [Member]
Estimated useful life	7 years
Furniture and Fixtures [Member] | Minimum [Member]
Estimated useful life	3 years
Furniture and Fixtures [Member] | Maximum [Member]
Estimated useful life	5 years
Leasehold Improvements [Member] | Minimum [Member]
Estimated useful life	5 years
Leasehold Improvements [Member] | Maximum [Member]
Estimated useful life	7 years

Other Accrued Liabilities - Sch

Other Accrued Liabilities - Schedule of Other Accrued Liabilities (Details) - USD ($)	Dec. 31, 2020	Dec. 31, 2019
Payables and Accruals [Abstract]
Amounts due to contract research organizations and other contractual agreements	$ 636,000	$ 475,440
Accrued payroll and related benefits	1,336,271	1,604,541
Accrued professional fees	66,850	204,155
Other	19,411	19,411
Total	$ 2,458,532	$ 2,303,547

Notes Payable (Details Narrativ

Notes Payable (Details Narrative) - USD ($)	Aug. 28, 2020	Jun. 24, 2020	Jun. 22, 2020	May 26, 2020	Apr. 23, 2020	Jun. 27, 2018	Dec. 31, 2020	Dec. 31, 2019	Sep. 21, 2020	Aug. 31, 2020	Feb. 29, 2020
Financing fees and expenses							$ 1,292,338	$ 1,393,400
Debt financing fees							$ 51,160
Warrants exercise per share							$ 0.01	$ 0.01	$ 0.79
Warrants exercisable									75,000	247,525	3,200,000
Loan amount							$ 5,000,000
Net proceeds from issuance of common stock							22,811,669	$ 7,844,852
Initial Horizon Credit Agreement Amendment [Member]
Interest expense, debt, total							808,899	1,006,760
Amortization of debt issuance costs							483,439	$ 386,640
Common Stock Outstanding [Member]
Common stock shares issued			2,666,667
Net proceeds from issuance of common stock			$ 9,100,000
Initial Horizon Credit Agreement [Member]
Line of credit facility, maximum borrowing capacity						$ 10,000,000
Proceeds from lines of credit, total						10,000,000
Debt instrument, end term fee						142,605
Financing fees and expenses						175,000
Loan origination fees						100,000
Debt instrument, unamortized discount						$ 782,116
End of term charge percentage						4.00%
Debt financing fees						$ 400,000
Fair value of warrants						507,116
End of term fees						$ 275,000
Initial Horizon Credit Agreement [Member] | Common Stock Outstanding [Member]
Warrants exercise per share						$ 2.63
Warrants exercisable						190,114
Warrants outstanding						95,057
Amendment to Horizon Credit Agreement [Member] | Horizon Technology Finance Corporation [Member]
Repayment of loans	$ 5,000,000
Debt instrument related end term charges	200,000
Debt instrument face amount	$ 5,000,000
Debt instrument, interest rate terms	The obligations bear interest at a rate calculated based an amount by which the one-month LIBOR exceeds 2% plus 7.625%. In no event shall the interest rate be less than 9.625%. Payments pursuant to the Amendment are interest only for the first twelve (12) months after August 1, 2020, followed by a 21-month amortization period of principal and interest through the scheduled maturity date.
Debt instrument, end term fee	$ 275,000
Debt instrument, restrictive covenants	In connection with the Amendment, Celsion agreed to a liquidity covenant which provides that, at all times, Celsion shall maintain unrestricted cash and/or cash equivalents on deposit in accounts over which the applicable Lenders maintain an account control agreement in an amount not less than $2.5 million. In addition, pursuant to the Amendment, Celsion has agreed to provide evidence to Horizon on or before March 31, 2021, that it has received aggregate cash proceeds of not less than $5 million from the sale of equity, debt, its New Jersey net operating losses, or a combination thereof, subsequent to the date of the Amendment.
Debt instrument, unamortized discount	$ 200,000						$ 109,706
Debt financing fees	5,000
Payment of debt extinguishment	5,000,000
New warrants fair value	$ 247,548
Amendment to Horizon Credit Agreement [Member] | Horizon Technology Finance Corporation [Member] | Common Stock Outstanding [Member]
Warrants exercise per share	$ 1.01
Warrants exercisable	247,525
Warrants cancelled	95,057
Amendment to Horizon Credit Agreement [Member] | Horizon Technology Finance Corporation [Member] | One-Month LIBOR Exceeds 2% Plus [Member]
Debt instrument interest rate	9.625%
April PPP Loan [Member] | Silicon Valley Bank [Member]
Proceeds from loan					$ 632,220
Loan repayment date					May 13, 2020
PPP Loans [Member] | Silicon Valley Bank [Member] | Maximum [Member]
Loan amount					$ 2,000,000
May PPP Loan [Member]
Interest accrued on loan		$ 577
May PPP Loan [Member] | Silicon Valley Bank [Member]
Proceeds from loan				$ 692,530
Loan repayment date				Jun. 24, 2020
May PPP Loan [Member] | Silicon Valley Bank [Member] | Promissory Note [Member]
Debt instrument face amount				$ 692,530

Notes Payable - Schedule of Fut

Notes Payable - Schedule of Future Principle Payments, Net of Unamortized Debt Discounts (Details)	Dec. 31, 2020USD ($)
Debt Disclosure [Abstract]
2021	$ 1,190,475
2022	2,857,140
2023 and thereafter	952,385
Subtotal of future principal payments	5,000,000
Unamortized debt issuance costs, net	51,160
Total	$ 5,051,160

Income Taxes (Details Narrative

Income Taxes (Details Narrative) - USD ($)	1 Months Ended			3 Months Ended		5 Months Ended			11 Months Ended	12 Months Ended	19 Months Ended	20 Months Ended	25 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Jul. 31, 2011	Mar. 31, 2021	Mar. 31, 2020	Oct. 31, 2017	Jun. 30, 2017	Jun. 30, 2013	Aug. 31, 2018	Dec. 31, 2020	Feb. 29, 2020	Feb. 28, 2013	Feb. 28, 2017	Jun. 30, 2015
Deferred tax asset	$ 1,845,823	$ 1,819,324								$ 1,845,823
Net operating losses	274,000,000		$ 4,200,000			$ 800,000	$ 300,000	$ 1,500,000	$ 1,500,000	274,000,000	$ 800,000	$ 1,400,000	$ 300,000	$ 1,600,000
Net operating losses, unused	225,000,000									$ 225,000,000
Net operating losses expiration, description										Expire starting in 2022 through 2037
Net operating losses carryforward limits, description										The deduction for net operating losses incurred in tax years beginning after January 1, 2018 is limited to 80% of annual taxable income
Operating loss carry forwards, limitation on use			$ 90,000,000			$ 5,000,000	$ 7,000,000	$ 4,000,000	$ 30,000,000		$ 15,000,000	$ 34,000,000	$ 35,000,000	$ 40,000,000
Operating loss carry forwards, limitation on use										The Company determined that it experienced ownership changes, as defined by Section 382, in connection with certain common stock offerings in July 2011, February 2013, June 2013, June 2015, February 2017, June 2017, October 2017, August 2018 and February 2020. As a result, the utilization of the Company's federal tax net operating loss carry forwards generated prior to the ownership changes are limited. As of December 31, 2020, the Company has net operating loss carry forwards for U.S. federal and state tax purposes of approximately $266 million, before excluding net operating losses that have been limited as a result of Section 382 limitations. The annual limitation due to Section 382 for net operating loss carry forward utilization is approximately $4.2 million per year for approximately $90 million in net operating change occurring in July 2011, approximately $1.4 million per year for approximately $34 million of additional net operating losses occurring from July 2011 to the ownership change that loss carry forwards existing at the ownership occurred in February 2013, approximately $1.5 million per year for approximately $4 million of additional net operating losses occurring from February 2013 to the ownership change that occurred in June 2013, approximately $1.6 million per year for approximately $40 million of additional net operating losses occurring from June 2013 to the ownership change that occurred in June 2015, approximately $0.3 million per year for approximately $35 million of additional net operating losses occurring from June 2015 to the ownership change that occurred in February 2017, approximately $0.3 million per year for approximately $7 million of additional net operating losses occurring from February 2017 to the ownership change that occurred in June 2017, approximately $0.8 million per year for approximately $5 million of additional net operating losses occurring from June 2017 to the ownership change that occurred in October 2017, and approximately $1.5 million per year for approximately $30 million of additional net operating losses occurring from October 2017 to the ownership change that occurred in August 2018, approximately $0.8 million per year for approximately $15 million of additional net operating losses occurring from August 2018 to the ownership change that occurred in February 2020. The utilization of these net operating loss carry forwards may be further limited if the Company experiences future ownership changes as defined in Section 382 of the Internal Revenue Code.
State and Local Jurisdiction [Member]
Net operating losses	39,000,000									$ 39,000,000
Federal Income Tax [Member] | No Expiration [Member]
Net operating losses	45,000,000									45,000,000
New Jersey [Member]
Deferred tax asset	1,800,000									$ 1,800,000
Payments from sale of nols					$ 1,800,000
Proceeds from sale of nols	$ 1,850,000	$ 1,800,000
New Jersey [Member] | Forecast [Member]
Payments from sale of nols				$ 1,850,000

Income Taxes - Schedule of Inco

Income Taxes - Schedule of Income Tax Provision (Benefit) (Details) - USD ($)	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Income Tax Disclosure [Abstract]
Federal, Current
Federal, Deferred
State and Local, Current
State and Local, Deferred	(1,845,823)	(1,816,474)
Effective tax rate	$ (1,845,823)	$ (1,816,474)

Income Taxes - Schedule of Effe

Income Taxes - Schedule of Effective Income Tax Rate Reconciliation (Details)	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Income Tax Disclosure [Abstract]
Federal statutory rate	21.00%	21.00%
State taxes, net of federal tax benefit	7.80%	9.80%
Permanent differences	(5.30%)	(2.60%)
Other		1.10%
Change in valuation allowance and deferred rate change, net	(15.50%)	(19.60%)
Effective tax rate	8.00%	9.70%

Income Taxes - Schedule of Defe

Income Taxes - Schedule of Deferred Tax Assets and Liabilities (Details) - USD ($)	Dec. 31, 2020	Dec. 31, 2019
Income Tax Disclosure [Abstract]
Net operating loss carryforwards	$ 60,446,000	$ 58,243,000
Other Deferred tax assets, net	5,182,000	254,000
Subtotal	65,628,000	58,497,000
Valuation allowance	(63,782,177)	(56,677,676)
Total deferred tax asset	$ 1,845,823	$ 1,819,324

Stockholders' Equity (Details N

Stockholders' Equity (Details Narrative) - USD ($)

Jan. 22, 2021

Sep. 08, 2020

Jun. 22, 2020

Feb. 27, 2020

Dec. 04, 2018

Aug. 31, 2018

Sep. 30, 2018

Mar. 05, 2020

Dec. 31, 2021

Dec. 31, 2020

Dec. 31, 2019

Dec. 31, 2018

Sep. 21, 2020

Mar. 12, 2020

Shelf registration statement amount

$ 75,000,000

Proceeds from issuance of common stock

$ 22,811,669

$ 7,844,852

Warrants term

4 years

Warrants exercise price

$ 0.01

$ 0.01

$ 0.79

Common Stock Outstanding [Member]

Stock issued during period, shares, new issues

2,666,667

Proceeds from issuance of common stock

$ 9,100,000

Capital on DemandTM Sales Agreement [Member]

Aggregate offering price

$ 16,000,000

Capital on Demand Agreement [Member]

Stock issued during period, shares, new issues

5,200,000

500,000

Proceeds from issuance of common stock

$ 6,200,000

$ 1,000,000

Capital on Demand Agreement [Member] | Forecast [Member]

Stock issued during period, shares, new issues

7,200,000

Proceeds from issuance of common stock

$ 6,900,000

Securities Purchase Agreement [Member]

Stock issued during period, shares, new issues

4,571,428

Proceeds from issuance of common stock

$ 4,800,000

Shares issued, price per share

$ 1.05

Securities Purchase Agreement [Member] | Original Warrants [Member]

Number of warrants to purchase common stock

2,971,428

Warrants term

5 years

Warrants exercise price

$ 1.15

Securities Purchase Agreement [Member] | Forecast [Member]

Stock issued during period, shares, new issues

25,925,925

Proceeds from issuance of common stock

$ 35,000,000

Shares issued, price per share

$ 1.35

Placement agent fee description

The Company agreed to pay the January 2021 Placement Agents a cash fee equal to 7% of the aggregate gross proceeds raised from the sale of the securities sold in the January 2021 Offering and reimburse the January 2021 Placement Agents for certain of their expenses in an amount not to exceed $82,500.

Exchange Agreements [Member] | Warrant [Member]

Number of warrants to purchase common stock

3,200,000

Warrants term

5 years

Warrants exercise price

$ 1.24

Exchange Agreements [Member] | Forecast [Member]

Number of warrants to purchase common stock

1,200,000

Proceeds from issuance of warrants

$ 1,500,000

Underwriting Agreement [Member] | Underwritten Offering [Member]

Stock issued during period, shares, new issues

2,666,667

Proceeds from issuance of common stock

$ 9,100,000

Shares issued, price per share

$ 3.75

Shares purchased, price per share

3.4875

Underwriting discount price per share

$ 0.2625

Percentage of underwriting discount on public offering price

0.70%

LPC Purchase Agreement [Member]

Stock issued during period, shares, new issues

3,300,000

Proceeds from issuance of common stock

$ 2,200,000

LPC Purchase Agreement [Member] | Lincoln Park Capital Fund, LLC [Member]

Stock issued during period, shares, new issues

26,000,000

Sale of stock, description of transaction

Over the 36-month term of the LPC Purchase Agreement, we have the right, but not the obligation, from time to time, in our sole discretion and subject to certain conditions, including that the closing price of our Common Stock is not below $0.25 per share, to direct Lincoln Park to purchase up to an aggregate amount of $26.0 million (subject to certain limitations) of shares of Common Stock. Under the Purchase Agreement, on any business day selected by us, we may direct Lincoln Park to purchase up to 400,000 shares (the "Regular Purchase Share Limit") of our Common Stock (each such purchase, a "Regular Purchase"). Lincoln Park's maximum obligation under any single Regular Purchase will not exceed $1,500,000 unless we mutually agree to increase the maximum amount of such Regular Purchase.

Equity method investment, ownership percentage

9.99%

LPC Purchase Agreement [Member] | Exchange Cap of Common Stock [Member] | Lincoln Park Capital Fund, LLC [Member]

Stock issued during period, shares, new issues

6,688,588

LPC Purchase Agreement [Member] | LPC Commitment Shares [Member] | Lincoln Park Capital Fund, LLC [Member]

Stock issued during period, shares, new issues

437,828

LPC Purchase Agreement [Member] | Common Stock Outstanding [Member] | Lincoln Park Capital Fund, LLC [Member]

Aggregate offering price

$ 1,000,000

Stock issued during period, shares, new issues

1,000,000

Shares issued, price per share

$ 1

Regular Purchase Share Limit [Member] | Lincoln Park Capital Fund, LLC [Member]

Sale of stock, description of transaction

If we direct Lincoln Park to purchase the maximum number of shares of Common Stock we then may sell in a Regular Purchase, then in addition to such Regular Purchase, and subject to certain conditions and limitations in the LPC Purchase Agreement, we may direct Lincoln Park to make an "accelerated purchase" of an additional amount of Common Stock that may not exceed the lesser of (i) 300% of the number of shares purchased pursuant to the corresponding Regular Purchase and (ii) 30% of the total number of shares of our Common Stock traded on The Nasdaq Capital Market during a specified period on the applicable purchase date as set forth in the Purchase Agreement. Under certain circumstances and in accordance with the Purchase Agreement, the Company may direct Lincoln Park to purchase shares in multiple accelerated purchases on the same trading day.

Regular Purchase Share Limit [Member] | Lincoln Park Capital Fund, LLC [Member] | Maximum [Member]

Stock issued during period, shares, new issues

400,000

2019 Aspire Purchase Agreements [Member]

Stock issued during period, shares, new issues

1,000,000

500,000

Proceeds from issuance of common stock

$ 1,600,000

$ 700,000

Aggregate offering price, additions

$ 15,000,000

$ 10,000,000

Aggregate offering price, term

24 months

24 months

2018 Aspire Purchase Agreements [Member]

Stock issued during period, shares, new issues

3,300,000

100,000

Proceeds from issuance of common stock

$ 6,300,000

$ 200,000

Stock-Based Compensation (Detai

Stock-Based Compensation (Details Narrative) - USD ($)	Feb. 19, 2019	Sep. 28, 2018	Dec. 31, 2020	Dec. 31, 2019	Jun. 15, 2020
Unrecognized compensation cost related to non-vested stock based compensation			$ 1,400,000
Stock based compensation cost expected to be recognized, weighted average period			1 year 1 month 6 days
Equity Stock Awards [Member] | Granted Under 2018 Plan and 2007 Plan [Member]
Number of shares reserved for future issuance			4,484,721
Inducement Awards [Member]
Number of shares reserved for future issuance			140,004
Stock Options and Restricted Stock Awards [Member]
Compensation cost			$ 1,900,000	$ 2,300,000
Stock Options and Restricted Stock Awards [Member] | Research and Development Expense [Member]
Compensation cost			800,000	900,000
Stock Options and Restricted Stock Awards [Member] | General and Administrative Expense [Member]
Compensation cost			$ 1,100,000	$ 1,400,000
2018 Stock Incentive Plan [Member]
Equity awards, number of stock authorized			2,700,000
Number of shares reserved for future issuance			6,505,924
2018 Stock Incentive Plan [Member] | Minimum [Member]
Number of equity awards available for future issuance			1,200,000		2,500,000
2018 Stock Incentive Plan [Member] | Maximum [Member]
Number of equity awards available for future issuance			3,900,000		6,400,000
2007 Stock Incentive Plan [Member]
Stock options, strike price description			Options are generally granted with strike prices equal to the fair market value of a share of Celsion common stock on the date of grant. Incentive stock options may be granted to purchase shares of common stock at a price not less than 100% of the fair market value of the underlying shares on the date of grant, provided that the exercise price of any incentive stock option granted to an eligible employee owning more than 10% of the outstanding stock of Celsion must be at least 110% of such fair market value on the date of grant. Only officers and key employees may receive incentive stock options.
Inducement Option Grants [Member] | Five New Employees [Member]
Inducement option grant, exercise price per share	$ 2.18	$ 2.77
Option vested period	3 years	3 years
Inducement Option Grants [Member] | Five New Employees [Member] | Restricted Stock [Member]
Number of shares issued	13,000	19,000
Inducement Option Grants [Member] | Five New Employees [Member] | Common Stock Outstanding [Member]
Number of shares issued	140,004	164,004
2018 Plan [Member]
Number of shares reserved for future issuance			2,018,453
2019 Bonus Program [Member] | Common Stock Outstanding [Member]
Number of shares issued			429,855
Annual bonus awards, percentage			50.00%

Stock-Based Compensation - Summ

Stock-Based Compensation - Summary of Stock Options (Details) - USD ($)	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Number Outstanding, Outstanding, Ending balance	4,624,725
Number Outstanding, Exercisable, Ending balance	3,351,086
Stock Options [Member]
Number Outstanding, Outstanding, Beginning balance	4,332,142	3,148,743
Number Outstanding, Options granted	670,250	1,250,754
Number Outstanding, Options exercised	(140,864)
Number Outstanding, Options canceled or expired	(236,803)	(67,355)
Number Outstanding, Outstanding, Ending balance	4,624,725	4,332,142
Number Outstanding, Exercisable, Ending balance	3,351,086
Weighted Average Exercise Price, Outstanding, Beginning balance	$ 2.63	$ 2.67
Weighted Average Exercise Price, Options granted	3.41	2
Weighted Average Exercise Price, Options exercised	2.12
Weighted Average Exercise Price, Options canceled or expired	2.14	2.50
Weighted Average Exercise Price, Outstanding, Ending balance	2.77	$ 2.63
Weighted Average Exercise Price, Exercisable, Ending balance	$ 2.80
Weighted Average Remaining Contractual Term (years), Outstanding, Ending balance	7 years 9 months 18 days
Weighted Average Remaining Contractual Term (years), Exercisable, Ending balance	7 years 4 months 24 days
Aggregate Intrinsic Value, Outstanding, Ending balance	$ 5,882
Aggregate Intrinsic Value, Exercisable, Ending balance	$ 750

Stock-Based Compensation - Su_2

Stock-Based Compensation - Summary of Non-Vested Restricted Stock Awards (Details) - $ / shares	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Share-based Payment Arrangement [Abstract]
Number Outstanding, Non-vested stock awards, Outstanding, Beginning balance	8,750	22,500
Number Outstanding, Non-vested stock awards, Granted	431,605	29,250
Number Outstanding, Non-vested stock awards, Vested and issued	(434,105)	(5,000)
Number Outstanding, Non-vested stock awards, Forfeited	(3,500)	(38,000)
Number Outstanding, Non-vested stock awards, Outstanding, Ending balance	2,750	8,750
Weighted Average Grant Date Fair Value, Non-vested stock awards, Outstanding, Beginning balance	$ 1.59	$ 2.72
Weighted Average Grant Date Fair Value, Non-vested stock awards, Granted	1.16	1.99
Weighted Average Grant Date Fair Value, Non-vested stock awards, Vested and issued	1.16	2.14
Weighted Average Grant Date Fair Value, Non-vested stock awards, Forfeited	1.59	2.48
Weighted Average Grant Date Fair Value, Non-vested stock awards, Outstanding, Ending balance	$ 0.98	$ 1.59

Stock-Based Compensation - Su_3

Stock-Based Compensation - Summary of Stock Options Outstanding (Details)	12 Months Ended
	Dec. 31, 2020$ / sharesshares
Options Outstanding, Number | shares	4,624,725
Options Exercisable, Number | shares	3,351,086
Exercise Price One [Member]
Range of Exercise Prices, Upper	$ 2
Options Outstanding, Number | shares	429,667
Options Outstanding, Weighted Average Remaining Contractual Term (in years)	8 years 9 months 18 days
Options Outstanding, Weighted Average Exercise Price	$ 1.64
Options Exercisable, Number | shares	147,276
Options Exercisable, Weighted Average Remaining Contractual Term (in years)	8 years 9 months 18 days
Options Exercisable, Weighted Average Exercise Price	$ 1.66
Exercise Price Two [Member]
Range of Exercise Prices, Upper	2
Range of Exercise Prices, Lower	$ 5
Options Outstanding, Number | shares	4,130,723
Options Outstanding, Weighted Average Remaining Contractual Term (in years)	7 years 8 months 12 days
Options Outstanding, Weighted Average Exercise Price	$ 2.64
Options Exercisable, Number | shares	3,139,475
Options Exercisable, Weighted Average Remaining Contractual Term (in years)	7 years 3 months 19 days
Options Exercisable, Weighted Average Exercise Price	$ 2.53
Exercise Price Three [Member]
Range of Exercise Prices, Upper	81.90
Range of Exercise Prices, Lower	$ 5
Options Outstanding, Number | shares	64,335
Options Outstanding, Weighted Average Remaining Contractual Term (in years)	5 years 2 months 12 days
Options Outstanding, Weighted Average Exercise Price	$ 18.81
Options Exercisable, Number | shares	64,335
Options Exercisable, Weighted Average Remaining Contractual Term (in years)	5 years 2 months 12 days
Options Exercisable, Weighted Average Exercise Price	$ 18.81

Stock-Based Compensation - Sche

Stock-Based Compensation - Schedule of Assumptions Used to Determine Fair Value of Options Granted (Details)	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Risk-free interest rate, minimum	0.65%	2.82%
Risk-free interest rate, maximum	1.33%	3.02%
Expected volatility, minimum	100.40%	101.30%
Expected volatility, maximum	109.10%	106.20%
Expected dividend yield	0.00%	0.00%
Minimum [Member]
Expected life (in years)	7 years 6 months	7 years 6 months
Maximum [Member]
Expected life (in years)	10 years	9 years 3 months 19 days

Earn-out Milestone Liability (D

Earn-out Milestone Liability (Details Narrative) - USD ($)	Jun. 20, 2014	Jun. 20, 2014	Oct. 31, 2020	Dec. 31, 2020	Dec. 31, 2019	Sep. 21, 2020	Aug. 31, 2020	Feb. 29, 2020	Mar. 28, 2019	Sep. 30, 2018
Warrants to purchase common stock						75,000	247,525	3,200,000
Warrant exercise price				$ 0.01	$ 0.01	$ 0.79
Gain (loss) from change in fair value of earn out milestone liability				$ 1,300,291	$ (3,189,955)
EGEN Inc [Member]
Future earn-out payments	$ 30,400,000	$ 30,400,000
Fair value of acquisition consideration	$ 13,900,000
Warrants to purchase common stock										200,000
Warrants strike price										$ 0.01
Warrant exercise price										$ 2
EGEN Inc [Member] | Amended Asset Purchase Agreement [Member]
Earnout milestone liability									$ 12,400,000
EGEN Inc [Member] | Fair Value Earnout Milestone Liability [Member]
Fair value of acquisition consideration				7,000,000	5,700,000
Gain on non-cash benefit				1,300,000	3,200,000
Gain (loss) from change in fair value of earn out milestone liability				$ 5,700,000	$ 8,900,000
EGEN Inc [Member] | Amended Asset Purchase Agreement Option Payment 1 [Member]
Risk adjusted assessment of each milestone				50.00%	80.00%
Gain (loss) from change in fair value of earn out milestone liability				$ 7,000,000	$ 7,000,000
EGEN Inc [Member] | Amended Asset Purchase Agreement Option Payment 2 [Member]
Risk adjusted assessment of each milestone				50.00%	20.00%
Gain (loss) from change in fair value of earn out milestone liability				$ 12,400,000	$ 12,400,000
EGEN Inc [Member] | Within One Year of Achieving Milestone [Member] | Amended Asset Purchase Agreement [Member]
Earnout milestone liability									12,400,000
EGEN Inc [Member] | 10 Business Days of Achieving Milestone [Member] | Amended Asset Purchase Agreement [Member]
Earnout milestone liability									$ 7,000,000
EGWU, Inc [Member]
Warrants to purchase common stock			200,000
Non-cash conversion exercised warrant shares			197,260
Minimum [Member] | EGEN Inc [Member]
Risk adjusted assessment of each milestone	10.00%	10.00%
Estimated time to achieve the milestone	1 year 6 months
Maximum [Member] | EGEN Inc [Member]
Risk adjusted assessment of each milestone	67.00%	67.00%
Estimated time to achieve the milestone		2 years 6 months

Earn-out Milestone Liability -

Earn-out Milestone Liability - Schedule of Changes in Earn-out Milestone Liability (Details) - USD ($)	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Hercules Warrant [Member]
Earn-out liabilities, beginning balance	$ 5,717,709	$ 8,907,664
Non-cash gain loss from the adjustment for the change in fair value	1,300,291	(3,189,955)
Earn-out liabilities, ending balance	$ 7,018,000	$ 5,717,709

Warrants (Details Narrative)

Warrants (Details Narrative) - USD ($)	Sep. 21, 2020	Dec. 31, 2020	Aug. 31, 2020	Feb. 29, 2020	Dec. 31, 2019
Warrant Abstract
Number of shares, warrant rights	75,000		247,525	3,200,000
Number of shares, warrant rights cancel			95,057
Class of warrant or right, year	4 years
Warrants exercise price	$ 0.79	$ 0.01			$ 0.01
Fair value warrant	$ 0.60
Professional fee expense	$ 45,000
Number of shares, warrant rights expired					1,167,064

Warrants - Summary of Warrant A

Warrants - Summary of Warrant Activity (Details) - USD ($)	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Warrants and Rights Note Disclosure [Abstract]
Number of Warrants Issued, Warrants outstanding, Beginning balance	626,098	1,593,162
Number of Warrants Issued, Warrants issued	3,522,525	200,000
Number of Warrants Issued, Warrants expired		(1,167,064)
Number of Warrants Issued, Warrants exercised	(200,000)
Number of Warrants Issued, Warrants cancelled	(95,057)
Number of Warrants Issued, Warrants outstanding, Ending balance	3,853,566	626,098
Weighted Average Exercise Price, Warrants outstanding, Beginning balance	$ 1.87	$ 5.36
Weighted Average Exercise Price, Warrants issued	1.21	0.01
Weighted Average Exercise Price, Warrants expired		6.32
Weighted Average Exercise Price, Warrants exercised	0.01
Weighted Average Exercise Price, Warrants cancelled	2.63
Weighted Average Exercise Price, Warrants outstanding, Ending balance	$ 1.35	$ 1.87
Aggregate intrinsic value of outstanding warrants	$ 0
Weighted average remaining contractual terms (years)	4 years 9 months 18 days

Celsion Employee Benefit Plans

Celsion Employee Benefit Plans (Details Narrative) - USD ($)	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Postemployment Benefits [Abstract]
Maximum annual contributions per employee, percent	3.00%
Matching contributions of employee	$ 111,000	$ 106,000
Discretionary contribution	$ 178,000
Discretionary contribution, rate	6.00%

Leases (Details Narrative)

Leases (Details Narrative)	Jan. 02, 2019USD ($)	Jan. 31, 2018USD ($)	Jul. 31, 2011ft²	Dec. 31, 2020USD ($)ft²	Dec. 31, 2019USD ($)
Area of land | ft²			10,870
Lease expiration date			Apr. 30, 2017
Lease, term of contract			66 months
Lease, renewal term			64 months
Lease, option to extend					The 1st Lease Amendment extended the term of the agreement for an additional 64 months, reduced the premises to 7,565 square feet, reduced the monthly rent and provided four months free rent. The monthly rent ranged from approximately $18,900 in the first year to approximately $20,500 in the final year of the 1st Lease Amendment. The Company also had a one-time option to cancel the lease as of the 40th month after the commencement date of the 1st Lease Amendment and must provide the landlord notice by the 28th month of the lease. Effective January 9, 2019, the Company amended the current terms of the 1st Lease Amendment to increase the size of the premises by 2,285 square feet to 9,850 square feet and also extended the lease term by one year to September 1, 2023. In conjunction with this 2nd Lease Amendment, we agreed to modify our one-time option to cancel the lease as of the end of August 2021 and we must provide notice to the landlord by the end of August 2020. The monthly rent will range from approximately $25,035 in the first year to approximately $27,088 in the final year of the 2nd Lease Amendment.
Lease description			In 2011, the Company executed a lease (the "Lease") with Brandywine Operating Partnership, L.P. (Brandywine), a Delaware limited partnership for a 10,870 square foot premises located in Lawrenceville, New Jersey and relocated its offices to Lawrenceville, New Jersey from Columbia, Maryland.
ROU asset	$ 400,000			$ 1,047,336	$ 1,431,640
Operating lease liabilities	1,900,000			1,143,718
Increased ROU asset	1,800,000
Operating lease costs				522,380	522,380
Operating lease expense paid				525,809	485,848
1st Lease Amendment [Member] | First Year [Member]
Lease, rent payment					18,900
1st Lease Amendment [Member] | Final Year [Member]
Lease, rent payment					20,500
2nd Lease Amendment [Member] | First Year [Member]
Lease, rent payment					25,035
2nd Lease Amendment [Member] | Final Year [Member]
Lease, rent payment					$ 27,088
EGEN Asset Purchase Agreement [Member]
Lease, rent payment		$ 18,100
Lease description		In connection with the EGEN Asset Purchase Agreement in June 2014, the Company assumed the existing lease with another landlord for an 11,500 square foot premises located in Huntsville Alabama. In January 2018, the Company and the Huntsville landlord entered into a new 60-month lease which reduced the premises to 9,049 square feet with rent payments of approximately $18,100 per month.
Accounting Standards Update 2016-02 [Member]
ROU asset	1,400,000			1,400,000
Operating lease liabilities	1,500,000			1,500,000
Other liabilities	$ 100,000			$ 100,000
Huntsville Alabama [Member]
Area of land | ft²				11,500

Leases - Schedule of Lease Paym

Leases - Schedule of Lease Payments and Maturity of Our Operating Lease Liabilities (Details) - USD ($)	Dec. 31, 2020	Jan. 02, 2019
Leases [Abstract]
2021	$ 530,734
2022	535,579
2023 and thereafter	233,117
Subtotal future lease payments	1,299,430
Less imputed interest	(155,712)
Total lease liabilities	$ 1,143,718	$ 1,900,000
Weighted average remaining life	2 years 5 months 16 days
Weighted average discount rate	9.98%

Commitments and Contingencies (

Commitments and Contingencies (Details Narrative) - USD ($)	Oct. 02, 2020	Apr. 24, 2020
Commitments and Contingencies Disclosure [Abstract]
Payment of legal fees		$ 187,500
Payments for legal settlements	$ 187,500

Licenses of Intellectual Prop_2

Licenses of Intellectual Property and Patents (Details Narrative) - USD ($)	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Jan. 31, 2003
Common stock, shares, issued	40,701,356	23,256,152
Common stock, value, issued	$ 407,014	$ 232,562
License Agreement [Member] | Duke University [Member]
Number of days before issuance factoring into average closing price	20 days
Amount of time after effective date of license agreement for registration rights to take place	1 year
Common stock, shares, issued			253,691
Common stock, value, issued			$ 2,200,000

Technology Development and Li_2

Technology Development and Licensing Agreements (Details Narrative) - Hisun [Member]	Jan. 18, 2013USD ($)
Non-refundable research and development fee	$ 5,000,000
Deferred revenue	$ 5,000,000
Deferred revenue amortization period	10 years

Subsequent Events (Details Narr

Subsequent Events (Details Narrative) - February 2020 Offering [Member] - Subsequent Event [Member]	3 Months Ended
	Mar. 19, 2021USD ($)shares
Sale of common stock, shares | shares	34,300,000
Proceeds from offering | $	$ 43,400,000