0001493152-21-019448 | 10-Q | XBRL Viewer

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Cover - shares	6 Months Ended
Cover - shares	Jun. 30, 2021	Aug. 11, 2021
Cover [Abstract]
Document Type	10-Q
Amendment Flag	false
Document Quarterly Report	true
Document Transition Report	false
Document Period End Date	Jun. 30, 2021
Document Fiscal Period Focus	Q2
Document Fiscal Year Focus	2021
Current Fiscal Year End Date	--12-31
Entity File Number	001-15911
Entity Registrant Name	CELSION CORPORATION
Entity Central Index Key	0000749647
Entity Tax Identification Number	52-1256615
Entity Incorporation, State or Country Code	DE
Entity Address, Address Line One	997 Lenox Drive
Entity Address, Address Line Two	Suite 100
Entity Address, City or Town	Lawrenceville
Entity Address, State or Province	NJ
Entity Address, Postal Zip Code	08648
City Area Code	(609)
Local Phone Number	896-9100
Title of 12(b) Security	Common stock, par value $0.01 per share
Trading Symbol	CLSN
Security Exchange Name	NASDAQ
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Entity Filer Category	Non-accelerated Filer
Entity Small Business	true
Entity Emerging Growth Company	false
Entity Shell Company	false
Entity Common Stock, Shares Outstanding		86,557,736

Condensed Consolidated Balance Sheets - USD ($)	Jun. 30, 2021	Dec. 31, 2020
Current assets:
Cash and cash equivalents	$ 26,437,424	$ 17,164,177
Investment in debt securities - available for sale, at fair value	31,923,285
Accrued interest on investment in debt securities	105,000
Advances and deposits on clinical programs and other current assets	1,844,451	1,660,695
Total current assets	60,310,160	18,824,872
Property and equipment (at cost, less accumulated depreciation and amortization)	458,551	294,551
Other assets:
Money market investments, restricted cash	6,000,000
Deferred income tax asset		1,845,823
In-process research and development, net	13,366,234	13,366,234
Goodwill	1,976,101	1,976,101
Operating lease right-of-use assets, net	840,195	1,047,336
Other intangible assets, net		113,660
Deposits and other assets	58,761	58,761
Total other assets	22,241,291	18,407,915
Total assets	83,010,002	37,527,338
Current liabilities:
Accounts payable – trade	2,109,479	2,244,847
Other accrued liabilities	2,312,705	2,458,532
Notes payable – current portion, net of deferred financing costs		1,116,663
Operating lease liability - current portion	458,168	433,413
Deferred revenue - current portion	500,000	500,000
Total current liabilities	5,380,352	6,753,455
Earn-out milestone liability	7,088,000	7,018,000
Notes payable – non-current portion, net of deferred financing costs	5,763,087	3,934,497
Operating lease liability - non-current portion	475,051	710,305
Deferred revenue - non-current portion	250,000	500,000
Total liabilities	18,956,490	18,916,257
Commitments and contingencies
Stockholders’ equity:
Preferred Stock - $0.01 par value (100,000 shares authorized, and no shares issued or outstanding at June 30, 2021 and December 31, 2020)
Common stock - $0.01 par value (112,500,000 shares authorized; 86,558,070 and 40,701,356 shares issued at June 30, 2021 and December 31, 2020, respectively, and 86,557,736 and 40,701,022 shares outstanding at June 30, 2021 and December 31, 2020, respectively)	865,581	407,014
Additional paid-in capital	386,414,630	330,289,596
Accumulated other comprehensive loss	(3,770)
Accumulated deficit	(323,137,741)	(312,000,341)
Total stockholders’ equity before treasury stock	64,138,700	18,696,269
Treasury stock, at cost (334 shares at June 30, 2021 and December 31, 2020)	(85,188)	(85,188)
Total stockholders’ equity	64,053,512	18,611,081
Total liabilities and stockholders’ equity	$ 83,010,002	$ 37,527,338

Condensed Consolidated Balance Sheets (Parenthetical) - $ / shares	Jun. 30, 2021	Dec. 31, 2020
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	0	0
Preferred stock, shares outstanding	0	0
Common stock, par value	$ 0.01	$ 0.01
Common stock, shares authorized	112,500,000	112,500,000
Common stock, shares issued	86,558,070	40,701,356
Common stock, shares outstanding	86,557,736	40,701,022
Treasury stock, shares	334	334

Condensed Consolidated Statements of Operations (Unaudited) - USD ($)	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Income Statement [Abstract]
Licensing revenue	$ 125,000	$ 125,000	$ 250,000	$ 250,000
Operating expenses:
Research and development	2,593,412	2,990,861	5,164,985	6,042,910
General and administrative	2,602,990	1,901,136	5,539,761	3,740,042
Total operating expenses	5,196,402	4,891,997	10,704,746	9,782,952
Loss from operations	(5,071,402)	(4,766,997)	(10,454,746)	(9,532,952)
Other (expense) income:
Gain (loss) from change in valuation of earn-out milestone liability	81,000	(256,296)	(70,000)	(297,570)
Investment income	(349)	20,960	2,062	109,269
Interest expense	(221,227)	(340,602)	(378,841)	(679,967)
Recognized loss on extinguishment of debt	(234,419)		(234,419)
Other (expense) income	(2,000)		(1,456)	1,407
Total other (expense) income, net	(376,995)	(575,938)	(682,654)	(866,861)
Net loss	$ (5,448,397)	$ (5,342,935)	$ (11,137,400)	$ (10,399,813)
Basic and diluted	$ (0.06)	$ (0.18)	$ (0.15)	$ (0.37)
Basic and diluted	85,923,755	29,887,329	76,165,451	27,830,573

Condensed Consolidated Statements of Comprehensive Loss (Unaudited) - USD ($)	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Changes in:
Realized gains (losses) on debt securities recognized in investment income, net	$ 1,785	$ (2,865)	$ 1,785	$ (46,097)
Unrealized (losses) gains on debt securities, net	(7,340)	6,918	(5,555)	11,185
Change in unrealized (losses) gains on available for sale securities, net	(5,555)	4,053	(3,770)	(34,912)
Net loss	(5,448,397)	(5,342,935)	(11,137,400)	(10,399,813)
Comprehensive loss	$ (5,453,952)	$ (5,338,882)	$ (11,141,170)	$ (10,434,725)

- Definition

The portion of profit or loss for the period, net of income taxes, which is attributable to the parent.

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+ Details

Condensed Consolidated Statements of Cash Flows (Unaudited) - USD ($)	3 Months Ended		6 Months Ended		12 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020	Dec. 31, 2020
Cash flows from operating activities:
Net loss	$ (5,448,397)	$ (5,342,935)	$ (11,137,400)	$ (10,399,813)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation and amortization			383,801	378,990
Change in fair value of earn-out milestone liability	(81,000)	256,296	70,000	297,570
Recognition of deferred revenue			(250,000)	(250,000)
Stock-based compensation costs			2,372,945	1,030,726
Deferred income tax asset			1,845,823	1,819,324
Amortization of deferred finance charges and debt discount associated with notes payable			145,884	192,793
Net changes in:
Accrued interest on investment securities			(105,000)	13,503
Advances, deposits, and other current assets			(183,756)	(60,104)
Accounts payable and accrued liabilities			(491,694)	(946,265)
Net cash used in operating activities			(7,349,397)	(7,923,276)
Cash flows from investing activities:
Purchases of investment securities			(40,927,055)	(9,940,894)
Proceeds from sale and maturity of investment securities			9,000,000	15,100,000
Purchases of property and equipment			(227,000)	(11,837)
Net cash (used in) provided by investing activities			(32,154,055)	5,147,269
Cash flows from financing activities:
Proceeds from sale of common stock equity, net of issuance costs			52,697,265	18,182,599
Proceeds from issuance of common stock upon conversion of stock warrants			1,508,666
Proceeds from issuance of common stock upon conversion of stock options			4,725	371,895
Proceeds from the SVB Loan Facility, net of issuance costs			5,756,630
Payoff of the Horizon Credit Agreement and accrued end of term fees			(5,190,587)
Proceeds from Payroll Protection Program (PPP) loans				1,324,750
Repayments on Payroll Protection Program (PPP) loans				(1,324,750)
Net cash provided by financing activities			54,776,699	18,554,494
Increase in cash, cash equivalents and restricted cash			15,273,247	15,778,487
Cash, cash equivalents and restricted cash at beginning of period			17,164,177	6,875,273	$ 6,875,273
Cash, cash equivalents and restricted cash at end of period	$ 32,437,424	$ 22,653,760	32,437,424	22,653,760	$ 17,164,177
Supplemental disclosures of cash flow information:
Interest paid			(267,360)	(487,174)
Cash paid for amounts included in measurement of lease liabilities:
Operating cash flows from lease payments			264,546	262,084
Common stock issued to settle accrued bonuses				498,632
Realized and unrealized gains (losses), net, on investment securities			$ 3,770	$ (34,912)

Condensed Consolidated Statements of Changes in Stockholders' Equity (Unaudited) - USD ($)	Common Stock [Member]	Additional Paid-in Capital [Member]	Treasury Stock [Member]	AOCI Attributable to Parent [Member]	Retained Earnings [Member]	Total
Beginning balance, value 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					(10,399,813)	(10,399,813)
Sale of equity through equity financing facilities	$ 94,027	18,088,572				18,182,599
Sale of equity through equity financing facilities net of fees, shares	9,402,843
Realized and unrealized gains and losses, net, on investments securities				(34,912)		(34,912)
Issuance of common stock upon exercise of options	$ 1,409	370,486				371,895
Issuance of common stock upon exercise of options, shares	140,864
Common stock issued to settle accrued bonuses	$ 4,299	494,333				$ 498,632
?Common stock issued to settle accrued bonuses, shares						429,855
Stock-based compensation expense		1,030,726				$ 1,030,726
Ending balance, value at Jun. 30, 2020	$ 332,297	324,869,780	$ (85,188)	7,866	(300,916,593)	24,208,162
Balance, shares at Jun. 30, 2020	33,229,380		334
Beginning balance, value 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
Ending balance, value 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
Beginning balance, value at Mar. 31, 2020	$ 292,574	311,570,995	$ (85,188)	3,813	(295,573,658)	16,208,536
Balance, shares at Mar. 31, 2020	29,257,101		334
Net loss					(5,342,935)	(5,342,935)
Sale of equity through equity financing facilities	$ 38,314	12,349,538				12,387,852
Sale of equity through equity financing facilities net of fees, shares	3,831,415
Realized and unrealized gains and losses, net, on investments securities				4,053		4,053
Issuance of common stock upon exercise of options	$ 1,409	370,486				371,895
Issuance of common stock upon exercise of options, shares	140,864
Stock-based compensation expense		578,761				578,761
Ending balance, value at Jun. 30, 2020	$ 332,297	324,869,780	$ (85,188)	7,866	(300,916,593)	24,208,162
Balance, shares at Jun. 30, 2020	33,229,380		334
Beginning balance, value 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
Ending balance, value at Mar. 31, 2021	$ 750,196	371,982,609	$ (85,188)	1,785	(317,689,344)	54,960,058
Balance, shares at Mar. 31, 2021	75,019,274		334
Beginning balance, value 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
Net loss					(11,137,400)	(11,137,400)
Sale of equity through equity financing facilities	$ 446,326	52,250,939				52,697,265
Sale of equity through equity financing facilities net of fees, shares	44,632,547
Shares issued upon exercise of common stock warrants, net of fees	$ 12,166	1,496,500				1,508,666
Shares issued upon exercise of common stock warrants, net of fees, shares	1,216,667
Shares issued upon exercise of options to purchase common stock	$ 75	4,650				4,725
Shares issued upon exercise of options to purchase common stock, shares	7,500
Realized and unrealized gains and losses, net, on investments securities				(3,770)		(3,770)
Stock-based compensation expense		2,372,945				2,372,945
Ending balance, value at Jun. 30, 2021	$ 865,581	386,414,630	$ (85,188)	(3,770)	(323,137,741)	64,053,512
Balance, shares at Jun. 30, 2021	86,557,736		334
Beginning balance, value at Mar. 31, 2021	$ 750,196	371,982,609	$ (85,188)	1,785	(317,689,344)	54,960,058
Balance, shares at Mar. 31, 2021	75,019,274		334
Net loss					(5,448,397)	(5,448,397)
Sale of equity through equity financing facilities	$ 115,385	13,638,402				13,753,787
Sale of equity through equity financing facilities net of fees, shares	11,538,462
Realized and unrealized gains and losses, net, on investments securities				(5,555)		(5,555)
Stock-based compensation expense		793,619				793,619
Ending balance, value at Jun. 30, 2021	$ 865,581	$ 386,414,630	$ (85,188)	$ (3,770)	$ (323,137,741)	$ 64,053,512
Balance, shares at Jun. 30, 2021	86,557,736		334

Business Description

6 Months Ended

Jun. 30, 2021

Accounting Policies [Abstract]

Business Description

Note 1. Business Description

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^®, a proprietary heat-activated liposomal encapsulation of doxorubicin, currently under investigator-sponsored development for several cancer indications. Celsion has two feasibility stage platform technologies for the development of novel nucleic acid-based immunotherapies and next generation vaccines and other anti-cancer DNA or RNA therapies. Both are novel synthetic, non-viral vectors with demonstrated capability in nucleic acid cellular transfection.

Basis of Presentation

6 Months Ended

Jun. 30, 2021

Organization, Consolidation and Presentation of Financial Statements [Abstract]

Basis of Presentation

Note 2. Basis of Presentation

The accompanying unaudited condensed consolidated financial statements, which include the accounts of the Company and its wholly owned subsidiaries, CLSN Laboratories, Inc. and Celsion, GmbH, have been prepared in accordance with generally accepted accounting principles in the United States (GAAP) for interim financial information and with the instructions to Form 10-Q and Article 10 of Regulation S-X. All significant intercompany balances and transactions have been eliminated in consolidation. Certain information and disclosures normally included in financial statements prepared in accordance with GAAP have been condensed or omitted pursuant to such rules and regulations.

In the opinion of management, all adjustments, consisting only of normal recurring accruals considered necessary for a fair presentation, have been included in the accompanying unaudited condensed consolidated financial statements. Operating results for the three and six-month periods June 30, 2021 and 2020 are not necessarily indicative of the results that may be expected for any other interim period(s) or for any full year. For further information, refer to the financial statements and notes thereto included in the Company’s Annual Report on Form 10-K for the fiscal year ended December 31, 2020 filed with the Securities and Exchange Commission (SEC) on March 19, 2021.

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 those estimates. Events and conditions arising subsequent to the most recent balance sheet date have been evaluated for their possible impact on the financial statements and accompanying notes. The Company continues to monitor the impact of the COVID-19 pandemic on its financial condition and results of operations, along with the valuation of its long-term assets, intangible assets, and goodwill. The effect of this matter could potentially have an impact on the valuation of such assets in the future. The COVID-19 pandemic is discussed in more detail in Note 3 to the financial statements.

Financial Condition and Business Plan

6 Months Ended

Jun. 30, 2021

Organization, Consolidation and Presentation of Financial Statements [Abstract]

Financial Condition and Business Plan

Note 3. Financial Condition and Business Plan

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 June 30, 2021, the Company has incurred approximately $323 million of cumulative net losses and had approximately $64.5 million in cash and cash equivalents, restricted cash, short-term investments and interest receivable. 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 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 and into 2021 due to 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. 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^®in combination with RFA for the treatment of HCC, or primary liver cancer. The recommendation was made following the second pre-planned interim safety and efficacy analysis by the DMC on July 9, 2020. The DMC’s analysis found that the pre-specified boundary for stopping the trial for futility of 0.900 was crossed with an actual value of 0.903. The Company followed the advice of the DMC and considered its options to either stop the study or continue to follow patients after a thorough review of the data, and an evaluation of the probability of success. On February 11, 2021, the Company issued a letter to shareholders stating that the Company was notifying all clinical sites to discontinue following patients in the OPTIMA Study.

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 the Company received net proceeds of approximately $1.85 million on May 10, 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. On June 16, 2021, the Company filed another application to sell approximately $1.6 million of net operating losses during 2021 and expects to receive up to approximately $1.4 million under the current year program.

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 24 months through July 2020, followed by a 21-month amortization period of principal and interest starting on August 1, 2020 and ending through the scheduled maturity date on April 1, 2023. 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 11 to these financial statements, in June 2021, the Company entered into a $10 million loan facility with Silicon Valley Bank. The Company immediately used $6 million from this facility to retire all outstanding indebtedness with Horizon Technology Finance Corporation. The remaining $4 million will be available to be drawn down up to 12 months after closing and will be used for working capital and to fund the advancement of the Company’s product pipelines. The funding is in the form of money market secured indebtedness bearing interest at a calculated WSJ Prime-based variable rate (currently 3.25%). Payments under the loan agreement are interest only for the first 24 months after loan closing, followed by a 24-month amortization period of principal and interest through the scheduled maturity date.

As more fully discussed in Note 12, during 2021 through the date of the filing of this Quarterly Report on Form 10-Q, the Company has raised approximately $6.9 million in gross proceeds from the use of its JonesTrading Capital on Demand^TM financing facility, $35 million from a registered direct financing completed in January 2021, $15 million from a registered direct financing completed on April 5, 2021, and $1.5 million from warrant exercises. With $64.5 million in cash and cash equivalents, restricted cash, short-term investments and interest receivable, the Company believes it has sufficient capital resources to fund its operations through the end of 2024.

The Company has based its estimates on assumptions that may prove to be wrong. The Company may need to obtain additional funds sooner or in greater amounts than it currently anticipates. Potential sources of financing include strategic relationships, public or private sales of the Company’s shares or debt, the sale of the Company’s State of New Jersey net operating losses and other sources. If the Company raises funds by selling additional shares of common stock or other securities convertible into common stock, the ownership interest of existing stockholders may be diluted.

New Accounting Pronouncements

6 Months Ended

Jun. 30, 2021

Accounting Changes and Error Corrections [Abstract]

New Accounting Pronouncements

Note 4. New 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 condensed consolidated financial position, results of operations, and cash flows, or do not apply to our operations.

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 adopted ASU 2016-13 in the 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 did not have a material impact on its consolidated financial statements.

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 intra-period 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. The Company adopted this standard during the first quarter of 2021. The adoption of ASU 2019-12 did not have a material impact on its consolidated financial statements.

In connection with the upcoming elimination of the London Inter-bank Offered Rate, (“LIBOR”) and other reference interest rates, the FASB issued ASU 2020-04, Reference Rate Reform (Topic 848) Facilitation of the Effects of Reference Reform on Financial Reporting. ASU 2020-04, which is available for contract modifications and hedging relationship modifications entered into or evaluated before December 31, 2022, provides certain practical expedients related to simplifying the accounting for contract modifications resulting from the change in terms from LIBOR to a new required interest rate benchmark. The Company is currently evaluating the effects of adopting this accounting standards update.

- Definition

The entire disclosure for change in accounting principle. Includes, but is not limited to, nature, reason, and method of adopting amendment to accounting standards or other change in accounting principle.

+ References

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+ Details

Restricted Cash

6 Months Ended

Jun. 30, 2021

Receivables [Abstract]

Restricted Cash

Note 5. Restricted Cash

As a condition of the $10 million loan facility with Silicon Valley Bank (“SVB”) entered into on June 18, 2021 as further discussed in Note 11, the Company is required at all times to maintain on deposit with SVB as cash collateral in a segregated money market bank account in the name of the Company, unrestricted and unencumbered cash in an amount of at least 100% of the aggregate outstanding amount of the SVB loan facility. SVB may restrict withdrawals or transfers by or on behalf of the Company that would violate this requirement. The required reserve totaled $6.0 million as of June 30, 2021. This amount is presented in part as restricted cash in other non-current assets on the accompanying condensed consolidated balance sheets.

The following table reconciles cash and cash equivalents and restricted cash per the balance sheet to the condensed statement of cash flows:

	June 30,		June 30,
	2021		2020
Cash and cash equivalents	$	26,437,424	$	22,653,760
Money market investments, restricted		6,000,000		-
Total	$	32,437,424	$	22,653,760

Net Loss per Common Share

6 Months Ended

Jun. 30, 2021

Earnings Per Share [Abstract]

Net Loss per Common Share

Note 6. Net Loss per Common Share

Basic loss per share is calculated based upon the net loss available to common shareholders divided by the weighted average number of common shares outstanding during the period. Diluted loss per share is calculated after adjusting the denominator of the basic earnings per share computation for the effects of all dilutive potential common shares outstanding during the period. The dilutive effects of preferred stock, options and warrants and their equivalents are computed using the treasury stock method.

The total number of shares of common stock issuable upon exercise of warrants, stock option grants and equity awards were 9,325,228 and 8,560,124 shares for the three and six-month periods ended June 30, 2021 and 2020, respectively. Warrants with an exercise price of $0.01 exercisable for 200,000 shares of common stock were considered issued in calculating basic loss per share during the first six-months of 2020. These warrants were exercised in October 2020. For the three and six-month periods ended June 30, 2021 and 2020, diluted loss per common share was the same as basic loss per common share as the other warrants and equity awards that were convertible into shares of the Company’s common stock were excluded from the calculation of diluted loss per common share as their effect would have been anti-dilutive. The Company did not pay any dividends during the first six months of 2021 or 2020.

Investment in Debt Securities Available for Sale

6 Months Ended

Jun. 30, 2021

Investments, Debt and Equity Securities [Abstract]

Investment in Debt Securities Available for Sale

Note 7. Investment in Debt Securities Available for Sale

Investments in debt securities available for sale with a fair value of $31,923,285 as of June 30, 2021, consisted of government backed debt securities and commercial paper. 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 on 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:

	June 30, 2021				December 31, 2020
	Cost		Fair Value		Cost		Fair Value
Short-term investments
Commercial paper	$	7,795,035	$	7,792,785	$	-		-
Government backed debt securities		24,132,020		24,130,500		-		-
Total	$	31,927,055	$	31,923,285	$	-	$	-

	June 30, 2021				December 31, 2020
	Cost		Fair Value		Cost		Fair Value
Short-term investment maturities
Within 3 months	$	2,999,420	$	7,792,785	$	-	$	-
Between 3-12 months		28,927,635		24,130,500		-		-
Total	$	31,927,055	$	31,923,285	$	-	$	-

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 June 30, 2021 and December 31, 2020. The Company has reviewed individual securities to determine whether a decline in fair value below the amortizable cost basis is other than temporary.

	June 30, 2021					December 31, 2020
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 with unrealized gains	$	5,998,980	$	1,073		$	-	$	-
Investments with unrealized losses		25,924,305		(4,843	)		-		-
Total	$	31,923,285	$	(3,770	)	$	-	$	-

Investment (loss) income, which includes net realized losses on sales of available for sale securities and investment income interest and dividends, is summarized as follows:

	2021			2020
	Three Months Ended June 30,
	2021			2020
Interest and dividends accrued and paid	$	1,436		$	18,095
Realized (losses) gains		(1,785	)		2,865
Investment (loss) income, net	$	(349	)	$	20,960

	2021			2020
	Six Months Ended June 30,
	2021			2020
Interest and dividends accrued and paid	$	3,847		$	63,172
Realized (losses) gains		(1,785	)		46,097
Investment income, net	$	2,062		$	109,269
Investment (loss) income, net		2,062			109,269

Fair Value Measurements

6 Months Ended

Jun. 30, 2021

Fair Value Measurements

Fair Value Measurements

Note 8. Fair Value Measurements

FASB ASC Section 820, Fair Value Measurements and Disclosures establishes a three-level hierarchy for fair value measurements which requires an entity to maximize the use of observable inputs and minimize the use of unobservable inputs when measuring fair value. The three levels of inputs that may be used to measure fair value are as follows:

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 2021 and 2020. 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 six-months ended June 30, 2021 or during the year ended December 31, 2020. 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 14).

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 June 30, 2021
Investment in debt securities - available for sale, at fair value	$	31,923,285	$	–	$	31,923,285	$	–

Non-recurring items as of June 30, 2021
In-process R&D (Note 9)	$	13,366,234	$	–	$	–	$	13,366,234

Non-recurring items as of December 31, 2020
In-process R&D (Note 9)	$	13,366,234	$	–	$	–	$	13,366,234

Liabilities:

Recurring items as of June 30, 2021
Earn-out milestone liability (Note 14)	$	7,088,000	$	–	$	–	$	7,088,000

Recurring items as of December 31, 2020
Earn-out milestone liability (Note 14)	$	7,018,000	$	–	$	–	$	7,018,000

Intangible Assets

6 Months Ended

Jun. 30, 2021

Goodwill and Intangible Assets Disclosure [Abstract]

Intangible Assets

Note 9. 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 first half of 2021, no impairment charges were recorded during the three or six-months ended June 30, 2021 and 2020.

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 $56,830 in each of the three and six-month periods ended June 30, 2021 and 2020. The carrying value of the Covenant Not to Compete was fully amortized as of June 30, 2021 and $113,660, net of $1,477,554 accumulated amortization, as of December 31, 2020.

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 June 30, 2021, 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.

Following is a summary of the net fair value of the assets acquired in the EGEN asset acquisition for the six-month period ended June 30, 2021:

	IPR&D		Goodwill		Covenant Not To Compete
For the six-months ended June 30, 2021
Balance at January 1, 2021, net	$	13,366,234	$	1,976,101	$	113,660
Amortization		-		-		(113,660	)
Balance at June 30, 2021, net	$	13,366,234	$	1,976,101	$	-

Accrued Liabilities

6 Months Ended

Jun. 30, 2021

Payables and Accruals [Abstract]

Accrued Liabilities

Note 10. Accrued Liabilities

Other accrued liabilities at June 30, 2021 and December 31, 2020 include the following:

Schedule of Accrued Liabilities

	June 30, 2021		December 31, 2020

Amounts due to contract research organizations and other contractual agreements	$	1,189,017	$	636,000
Accrued payroll and related benefits		1,016,610		1,736,271
Accrued professional fees		80,625		66,850
Accrued interest		7,042		-
Other		19,411		19,411
Total	$	2,312,705	$	2,458,532

Notes

6 Months Ended

Jun. 30, 2021

Debt Disclosure [Abstract]

Notes

Note 11. Notes Payable

The SVB Loan Facility

On June 18, 2021, the Company entered into a $10 million loan facility (the “SVB Loan Facility”) with Silicon Valley Bank (“SVB”). Celsion immediately used $6 million from the SVB Loan Facility to retire all outstanding indebtedness with Horizon Technology Finance Corporation as further discussed below. Simultaneously with this transaction, the Company used $6.0 million of other available funds to establish a restricted cash account which serves as security for the SVB Loan Facility. The remaining $4 million will be available to be drawn down up to 12 months after closing and will be used for working capital and to fund the advancement of the Company’s product pipeline, including GEN-1 for the treatment of newly diagnosed advanced ovarian cancer, as well as other strategic initiatives intended to broaden its product pipeline.

The SVB Loan Facility is in the form of money market secured indebtedness bearing interest at a calculated WSJ Prime-based variable rate (currently 3.25%). A final payment equal to 3% of the total $10 million commitment amount is due upon maturity or prepayment of the SVB Loan Facility. There was no facility commitment fee and no stock or warrants were issued to SVB. Payments under the loan agreement are interest only for the first 24 months after loan closing, followed by a 24-month amortization period of principal and interest through the scheduled maturity date.

In connection with the SVB Loan Facility, the Company incurred financing fees and expenses totaling $243,370 which is recorded and classified as debt discount and are being amortized as interest expense using the effective interest method over the life of the loan. Also, in connection with the SVB Loan Facility, the Company is required to pay an end-of-term fee equal to 3.0% of the original loan amount at time of maturity. Therefore, these amounts totaling $300,000 were being amortized as interest expense using the effective interest method over the life of the loan. During the three and six-month periods ended June 30, 2021, the Company incurred $7,042 in interest expense and amortized $6,457 as interest expense for debt discounts and end-of-term fee in connection with the SVB Financing Facility.

Following is a schedule of future principal payments, net of unamortized debt discounts and amortized end-of-term fee, due on the SVB Loan Facility:

	As of June 30,
2022	$	–
2023		–
2024		3,000,000
2025 and thereafter		3,000,000
Subtotal of future principal payments		6,000,000
Unamortized debt premium, net		(236,913	)
Total	$	5,763,087

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 Horizon Credit Agreement was secured by a first-priority security interest in substantially all assets of Celsion other than intellectual property assets. The obligations bore 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 were 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 on April 1, 2023. In addition, the remaining $5 million in obligations was subject to an end of term fee equal, in the aggregate, to $275,000, which amount was 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 agreed to provide evidence to Horizon on or before March 31, 2021, that it 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 Agreement, the Company was required to pay an end of term charge equal to 4.0% of the original loan amount at time of maturity. Therefore, those 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 Horizon Credit Agreement remain outstanding at a per share exercise price of $2.63.

The New 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. 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, for debt modification and extinguishment accounting. We accounted for the $5 million we repaid as a debt extinguishment thereby reducing the principal obligations accordingly. Also, in connection with the $5 million repayment, we recognized as interest expense, approximately $0.2 million of unamortized debt discount, deferred financing and end of term fees related to the repaid obligation in August 2020.

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 the three and six-month periods ended June 30, 2021, the Company incurred $105,607 and $225,920, respectively, in interest expense and amortized $102,126 and $139,428 as interest expense for debt discounts and end of term charges in connection with the Horizon Credit Agreement. During the three and six-month periods ended June 30, 2020, the Company incurred $243,299 and $486,597, respectively, in interest expense and amortized $96,727 and $192,793, respectfully, as interest expense for debt discounts and end of term charges in connection with the Horizon Credit Agreement.

On June 18, 2021, as a condition of entering into the SVB Loan Facility, the Company paid the outstanding principal balance, an early termination fee and the end of term charges in full satisfaction of the Horizon Credit Agreement, as amended. Following is a schedule of the amounts paid to Horizon on June 18, 2021.

Schedule of Debt


Principal balance at June 18, 2021	$	5,000,000
Early termination fees		150,000
End of term charges		275,000
Total	$	5,425,000

During the three and six months ended June 30, 2021, the Company recorded a loss of $234,419 on the termination of the Horizon Credit Agreement, as amended, which represented the early termination fee and the end of term fees, net of previously amortized interest expense totaling $190,581 on the date of its payoff.

- Definition

The entire disclosure for information about short-term and long-term debt arrangements, which includes amounts of borrowings under each line of credit, note payable, commercial paper issue, bonds indenture, debenture issue, own-share lending arrangements and any other contractual agreement to repay funds, and about the underlying arrangements, rationale for a classification as long-term, including repayment terms, interest rates, collateral provided, restrictions on use of assets and activities, whether or not in compliance with debt covenants, and other matters important to users of the financial statements, such as the effects of refinancing and noncompliance with debt covenants.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
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-Name Accounting Standards Codification
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Reference 2: http://www.xbrl.org/2003/role/disclosureRef
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-Name Accounting Standards Codification
-Topic 470
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-Section 50
-Paragraph 1B
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Reference 3: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
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Reference 4: http://www.xbrl.org/2003/role/disclosureRef
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-Paragraph 1I
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Reference 5: http://www.xbrl.org/2003/role/disclosureRef
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-Subparagraph (d)
-URI http://asc.fasb.org/extlink&oid=123466505&loc=SL123495371-112611

Reference 6: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
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-Section S99
-Paragraph 1
-Subparagraph (SX 210.4-08(c))
-URI http://asc.fasb.org/extlink&oid=120395691&loc=d3e23780-122690

Reference 7: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
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-SubTopic 20
-Section 50
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-Subparagraph (g)
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Reference 8: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
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Reference 9: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
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-Paragraph 1C
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=123466505&loc=SL123495334-112611

Reference 10: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
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-Section 50
-Paragraph 1E
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=123466505&loc=SL123495348-112611

Reference 11: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 470
-SubTopic 20
-Section 50
-Paragraph 1B
-URI http://asc.fasb.org/extlink&oid=123466505&loc=SL123495323-112611

Reference 12: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 470
-SubTopic 20
-Section 50
-Paragraph 1I
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=123466505&loc=SL123495371-112611

Reference 13: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 470
-SubTopic 20
-Section 50
-Paragraph 1B
-Subparagraph (i)
-URI http://asc.fasb.org/extlink&oid=123466505&loc=SL123495323-112611

+ Details

Stockholders’ Equity

6 Months Ended

Jun. 30, 2021

Equity [Abstract]

Stockholders’ Equity

Note 12. 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 was fully utilized by the end of January 2021.

On March 19, 2021, the Company filed with the SEC a new $100 million shelf registration statement on Form S-3 (the “2021 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 March 30, 2021.

Capital on Demand^TM Sales Agreement

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 2020 through June 30, 2020, the Company sold and issued an aggregate of 1.2 million shares under the Capital on Demand Agreement, receiving approximately $3.5 million in gross proceeds. During the first half of 2021, the Company 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.

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 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. 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 through the date of this Quarterly Report on Form 10-Q, the Company issued 1.2 million shares pursuant to investors exercising Exchange Warrants, receiving approximately $1.5 million in net proceeds.

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.

Pursuant to the Underwriting Agreement, until December 31, 2020, the Underwriter had 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 common stock 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.

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 January 2021 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.

March 2021 Registered Direct Offering

On March 31, 2021, the Company entered into a Securities Purchase Agreement (the “March 2021 Purchase Agreement”) with several institutional investors, pursuant to which the Company agreed to issue and sell, in a registered direct offering (the “March 2021 Offering”), an aggregate of 11,538,462 shares of the Company’s common stock, at an offering price of $1.30 per share for gross proceeds of approximately $15 million before the deduction of the placement agents fee and offering expenses. The shares were offered by the Company pursuant to the 2021 Registration Statement. The closing of the Offering occurred on April 5, 2021.

In connection with the March 2021 Offering, the Company entered into a placement agent agreement (the “March 2021 Placement Agent Agreement”) with A.G.P./Alliance Global Partners, as lead placement agent (“AGP,” and together with JonesTrading Institutional Services LLC and Brookline Capital Markets, a division of Arcadia Securities, LLC, serving as co-placement agents, the “March 2021 Placement Agents”) pursuant to which the Company agreed to pay the March 2021 Placement Agents an aggregate cash fee equal to 7% of the aggregate gross proceeds raised from the sale of the securities sold in the Offering and reimburse the Placement Agents for certain of their expenses in an amount not to exceed $82,500.

Under the March 2021 Purchase Agreement and March 2021 Placement Agent Agreement, the Company and its subsidiaries are prohibited, for a period of 90 days after the closing, from entering into any agreement to issue or announcing any issuance or proposed issuance 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 AGP or the investors participating in the offering. For purposes of this offering, AGP and the investors from the Company’s January 2021 Offering waived a similar 90-day restriction in the placement agent agreement and purchase agreement for that transaction.

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”). During 2020, the Company sold and issued an aggregate of 3.3 million shares, including the 437,828 commitment shares, under the LPC Purchase Agreement, receiving approximately $2.2 million in gross proceeds. On January 21, 2021, the Company terminated the LPC Purchase Agreement. The Company did not sell any shares under the LPC Purchase Agreement in 2021.

- Definition

The entire disclosure for shareholders' equity comprised of portions attributable to the parent entity and noncontrolling interest, including other comprehensive income. Includes, but is not limited to, balances of common stock, preferred stock, additional paid-in capital, other capital and retained earnings, accumulated balance for each classification of other comprehensive income and amount of comprehensive income.

+ References

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Reference 3: http://www.xbrl.org/2003/role/disclosureRef
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Reference 8: http://fasb.org/us-gaap/role/ref/legacyRef
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Reference 9: http://www.xbrl.org/2003/role/disclosureRef
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Reference 10: http://www.xbrl.org/2003/role/disclosureRef
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+ Details

Stock-Based Compensation

6 Months Ended

Jun. 30, 2021

Share-based Payment Arrangement [Abstract]

Stock-Based Compensation

Note 13. 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. At the 2021 Annual Stockholders Meeting of the Company held on June 10, 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 7,700,000 to a total of 14,100,000 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 June 30, 2021, there were a total of 14,198,424 shares of Celsion common stock reserved for issuance under the 2018 Plan, which were comprised of 6,548,325 shares of Celsion common stock subject to equity awards previously granted under the 2018 Plan and 2007 Plan and 7,650,099 shares of Celsion common stock available for future issuance under the 2018 Plan. As of June 30, 2021, 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 amounted to $793,619 and $578,761 for the three-month periods ended June 30, 2021 and 2020, respectively. Of these amounts, $299,581 and $200,186 was charged to research and development during the three-month periods ended June 30, 2021 and 2020, respectively, and $494,038 and $378,575 was charged to general and administrative expenses during the three-month periods ended June 30, 2021 and 2020, respectively.

Total compensation cost related to stock options and restricted stock awards amounted to $2,372,945 and $1,030,726 for the six-month periods ended June 30, 2021 and 2020, respectively. Of these amounts, $882,088 and $378,122 was charged to research and development during the six-month periods ended June 30, 2021 and 2020, respectively, and $1,490,857 and $652,604 was charged to general and administrative expenses during the six-month periods ended June 30, 2021 and 2020, respectively.

As of June 30, 2021, there was $3.2 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 1.2 years. The weighted average grant date fair values of the stock options granted was $1.98 and $3.10 during the six-month periods ended June 30, 2021 and 2020, respectively. A summary of stock option awards and restricted stock grants for the three-months ended June 30, 2021 is presented below:

	Stock Options					Restricted Stock Awards				Weighted Average
	Options Outstanding			Weighted Average Exercise Price		Non-vested Restricted Stock Outstanding		Weighted Average Grant Date Fair Value		Contractual Terms of Equity Awards (in years)
Equity awards outstanding at January 1, 2021		4,624,725		$	2.77		2,750	$	0.89

Equity awards granted		2,154,000		$	2.18		7,000	$	1.38

Equity awards exercised or vested and issued		(7,500	)	$	0.63		-	$	-

Equity awards forfeited, cancelled or expired		(92,646	)	$	2.69		-	$	-

Equity awards outstanding at June 30, 2021		6,678,579		$	2.58		9,750	$	1.27		8.0

Aggregate intrinsic value of outstanding equity awards at June 30, 2021	$	12,145				$	12,383

Equity awards exercisable at June 30, 2021		4,329,286		$	2.73						7.8

Aggregate intrinsic value of equity awards exercisable at June 30, 2021	$	1,650

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:

Six Months Ended June 30,

2021 2020

Risk-free interest rate 1.56 to 1.74 % 0.71 to 1.33 %

Expected volatility 106.8 to 113.0 % 100.4 to 104.2 %

Expected life (in years) 7.5 to 10.0 8.5 to 10.0

Expected dividend yield - % - %

Expected volatilities utilized in the model are based on historical volatility of the Company’s stock price. The risk-free interest rate is derived from values assigned to U.S. Treasury bonds with terms that approximate the expected option lives in effect at the time of grant.

Earn-Out Milestone Liability

6 Months Ended

Jun. 30, 2021

Earn-out Milestone Liability

Earn-Out Milestone Liability

Note 14. Earn-Out Milestone Liability

On March 28, 2019, the Company and EGWU, Inc, entered into an amendment to its purchase agreement (“Amended Asset Purchase Agreement”), whereby payment of the earnout milestone liability related to the Ovarian Cancer Indication of $12.4 million had 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.

As of June 30, 2021, March 31, 2021, and December 31, 2020, the Company fair valued the earn-out milestone liability at $7.1 million, $7.2 million and $7.0 million, respectively, and recognized a non-cash benefit of $0.1 million for the three-months ended June 30, 2021 and a non-cash charge of $0.1 million for the six-months ended June 30, 2021. In assessing the earnout milestone liability at June 30, 2021 and March 31, 2021, the Company fair valued each of the two payment options per the Amended Asset Purchase Agreement and weighted them at 50% / 50% probability for the $7.0 million and the $12.4 million payments, respectively.

As of June 30, 2020, March 31, 2020, and December 31, 2019, the Company fair valued the earn-out milestone liability at $6.0 million, $5.8 million, and $5.7 million, respectively and recognized a non-cash charge of $0.2 and $0.3 million for the three-month and six-month periods ended June 30, 2020, respectively. In assessing the earnout milestone liability at June 30, 2020 and March 31, 2020, the Company fair valued each of the two payment options per the Amended Asset Purchase Agreement and weighted them at 80% / 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 the six-month period ended June 30, 2021:


Balance at January 1, 2021	$	(7,018,000	)
Non-cash loss from the change in fair value		(70,000	)
Balance at June 30, 2021	$	(7,088,000	)

The following is a schedule of the Company’s risk-adjustment assessment of each milestone:

Schedule of Risk Adjustment Assessment

Date	Risk-adjustment Assessment of Achieving Each Milestone			Discount Rate			Estimated Time to Achieve

June 30, 2021		80	%		9	%	0.42 to 1.42 years
March 31, 2021		80	%		9	%	0.29 to 1.29 years
December 31, 2020		80	%		9	%	0.54 to 1.54 years

June 30, 2020		80	%		9	%	0.54 to 1.54 years
March 31, 2020		80	%		9	%	1.04 to 2.04 years
December 31, 2019		80	%		9	%	1.12 to 2.12 years

Warrants

6 Months Ended

Jun. 30, 2021

Warrants

Warrants

Note 15. Warrants

Following is a summary of all warrant activity for the six months ended June 30, 2021:

Summary of Warrant Activity

Warrants	Number of Warrants Issued			Weighted Average Exercise Price

Warrants outstanding at December 31, 2020		3,853,566		$	1.35

Warrants exercised during the six months ended June 30, 2021 (see Note 12)		(1,216,667	)	$	1.24

Warrants outstanding at June 30, 2021		2,636,899		$	1.40

Aggregate intrinsic value of outstanding warrants at June 30, 2021	$	159,857

Weighted average remaining contractual terms at June 30, 2021		4.6 years

Leases

6 Months Ended

Jun. 30, 2021

Leases

Leases

Note 16. 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 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 1^st Lease Amendment. Effective January 9, 2019, the Company amended the current terms of the 1^st 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. The monthly rent ranges from approximately $25,035 in the first year to approximately $27,088 in the final year of the 2^nd Lease Amendment.

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.

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 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 Condensed Consolidated Balance Sheet but had no impact on our condensed 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 Lease Amendment for the New Jersey office lease in January 2019, the Company considered this as one modified lease and not as two separate leases. Therefore, in January 2019, the Company determined this lease was an operating lease and remeasured the ROU asset and lease liability. Therefore, the Company increased the ROU asset and operating lease liabilities by $0.4 million to $1.8 million and $1.9 million, respectively.

Following is a table of the lease payments and maturity of our operating lease liabilities as of June 30, 2021:

	For the year ending June 30,
Remainder of 2021	$	266,188
2022		535,579
2023		233,116
2024 and thereafter		-
Subtotal future lease payments		1,034,883
Less imputed interest		(101,664	)
Total lease liabilities	$	933,219

Weighted average remaining life		2.0 years

Weighted average discount rate		9.98	%

For the three-month and six-month periods ended June 30, 2021, operating lease expense was $130,595 and $261,190, respectively and cash paid for operating leases included in operating cash flows was $132,684 and $264,546, respectively. For the three-month and six-month periods ended June 30, 2020, operating lease expense was $130,595 and $261,190, respectively and cash paid for operating leases included in operating cash flows was $131,452 and $262,084, respectively.

Technology Development and Licensing Agreements

6 Months Ended

Jun. 30, 2021

Technology Development And Licensing Agreements

Technology Development and Licensing Agreements

Note 17. 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^® in the China territory. In accordance with the terms of the agreement, Hisun will be responsible for providing all of the technical and regulatory support services, including the costs of all technical transfer, registration and bioequivalence studies, technical transfer costs, Celsion consultative support costs and the purchase of any necessary equipment and additional facility costs necessary to support capacity requirements for the manufacture of ThermoDox^®. Celsion will repay Hisun for the aggregate amount of these development costs and fees commencing on the successful completion of three registration batches of ThermoDox^®. Hisun is also obligated to certain performance requirements under the agreement. The agreement will initially be limited to a percentage of the production requirements of ThermoDox^® in the China territory with Hisun retaining an option for additional global supply after local regulatory approval in the China territory. In addition, Hisun will collaborate with Celsion around the regulatory approval activities for ThermoDox^®with the China State Food and Drug Administration (CHINA FDA). During the first quarter of 2015, Hisun completed the successful manufacture of three registration batches 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^®in mainland China, Hong Kong and Macau (the China territory). Following our announcement on January 31, 2013 that the HEAT study failed to meet its primary endpoint, Celsion and Hisun have agreed that the Technology Development Contract entered into on January 18, 2013 will remain in effect while the parties continue to collaborate and are evaluating the next steps in relation to ThermoDox^®, which include the sub-group analysis of patients in the Phase III HEAT Study for the hepatocellular carcinoma clinical indication and other activities to further the development of ThermoDox^®for the Greater China market. The $5.0 million received as a non-refundable payment from Hisun in the first quarter 2013 has been recorded to deferred revenue and will continue to be amortized over the 10 -year term of the agreement, until such time as the parties find a mutually acceptable path forward on the development of ThermoDox^® based on findings of the ongoing post-study analysis of the HEAT Study data.

On July 19, 2013, the Company and Hisun entered into a Memorandum of Understanding to pursue ongoing cooperation for the continued clinical development of ThermoDox^® as well as the technology transfer relating to the commercial manufacture of ThermoDox^®for the China territory. This expanded level of cooperation includes development of the next generation liposomal formulation with the goal of creating safer, more efficacious versions of marketed cancer chemotherapeutics.

Among the key provisions of the Celsion-Hisun Memorandum of Understanding are:

●	Hisun will provide the Company with internal resources necessary to complete the technology transfer of the Company’s proprietary manufacturing process and the production of registration batches for the China territory;

●	Hisun will coordinate with the Company around the clinical and regulatory approval activities for ThermoDox^® as well as other liposomal formations with the CHINA FDA; and

●	Hisun will be granted a right of first offer for a commercial license to ThermoDox^® for the sale and distribution of ThermoDox^®in the China territory.

On August 8, 2016, we signed a Technology Transfer, Manufacturing and Commercial Supply Agreement (“GEN-1 Agreement”) with Hisun to pursue an expanded partnership for the technology transfer relating to the clinical and commercial manufacture and supply of GEN-1, Celsion’s proprietary gene mediated, IL-12 immunotherapy, for the greater China territory, with the option to expand into other countries in the rest of the world after all necessary regulatory approvals are in effect. The GEN-1 Agreement will help to support supply for both ongoing and planned clinical studies in the U.S., and for potential future studies of GEN-1 in China. GEN-1 is currently being evaluated by Celsion in first line ovarian cancer patients.

Key provisions of the GEN-1 Agreement are as follows:

●	the GEN-1 Agreement has targeted unit costs for clinical supplies of GEN-1 that are substantially competitive with the Company’s current suppliers;

●	once approved, the cost structure for GEN-1 will support rapid market adoption and significant gross margins across global markets;

●	Celsion will provide Hisun a certain percentage of China’s commercial unit demand, and separately of global commercial unit demand, subject to regulatory approval;

●	Hisun and Celsion will commence technology transfer activities relating to the manufacture of GEN-1, including all studies required by CHINA FDA for site approval; and

●	Hisun will collaborate with Celsion around the regulatory approval activities for GEN-1 with the CHINA FDA. A local China partner affords Celsion access to accelerated CHINA FDA review and potential regulatory exclusivity for the approved indication.

The Company evaluated the Hisun arrangement in accordance with ASC 606 and determined that its performance obligations under the agreement include the non-exclusive, royalty-free license, research and development services to be provided by the Company, and its obligation to serve on a joint committee. The Company concluded that the license was not distinct since its value is closely tied to the ongoing research and development activities. As such, the license and the research and development services are bundled as a single performance obligation. Since the provision of the license and research and development services are considered a single performance obligation, the $5,000,000 upfront payment is being recognized as revenue ratably through 2022.

Commitments and Contingencies

6 Months Ended

Jun. 30, 2021

Commitments and Contingencies Disclosure [Abstract]

Commitments and Contingencies

Note 18. 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 (the “Shareholder Action”). The Shareholder Action alleged breaches of the defendants’ fiduciary duties based on allegations that the defendants omitted or made improper statements when seeking shareholder approval of the 2018 Stock Incentive Plan. The Shareholder Action sought, among other things, any damages sustained by the Company as a result of the defendants’ alleged wrongdoing, a declaratory judgment against all defendants invalidating the 2018 Stock Incentive Plan and declaring any awards made under the Plan invalid, rescinded, and subject to disgorgement, an order disgorging the equity awards granted to the Individual Defendants under the 2018 Stock Incentive Plan, and attorneys’ fees and costs.

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., Case No. 1:20-cv-15228. The plaintiff alleges that the Company and Individual Defendants made false and misleading statements regarding one of the Company’s product candidates, ThermoDox^®, and brings claims for damages under Section 10(b) of the Exchange Act and Rule 10b-5 promulgated thereunder against all Defendants, and under Section 20(a) of the Exchange Act of 1934 against the Spar Individual Defendants. The Company believes that the case is without merit and intends to defend it vigorously. Due to the early stage of the case neither the likelihood that a loss, if any, will be realized, nor an estimate of possible loss or range of loss, if any, can be determined.

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., Case No. 3:21-cv-02662. The plaintiff alleges breach of fiduciary duty and other claims arising out of alleged statements made by certain of the Company’s directors and/or officers regarding ThermoDox^®. The Company believes it has meritorious defenses to these claims and intends to vigorously contest this suit. Due to the early stage of the case neither the likelihood that a loss, if any, will be realized, nor an estimate of possible loss or range of loss, if any, can be determined.

Restricted Cash (Tables)

6 Months Ended

Jun. 30, 2021

Receivables [Abstract]

Schedule of Cash and Cash Equivalents and Restricted Cash

The following table reconciles cash and cash equivalents and restricted cash per the balance sheet to the condensed statement of cash flows:

	June 30,		June 30,
	2021		2020
Cash and cash equivalents	$	26,437,424	$	22,653,760
Money market investments, restricted		6,000,000		-
Total	$	32,437,424	$	22,653,760

Investment in Debt Securities Available for Sale (Tables)

6 Months Ended

Jun. 30, 2021

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:

	June 30, 2021				December 31, 2020
	Cost		Fair Value		Cost		Fair Value
Short-term investments
Commercial paper	$	7,795,035	$	7,792,785	$	-		-
Government backed debt securities		24,132,020		24,130,500		-		-
Total	$	31,927,055	$	31,923,285	$	-	$	-

	June 30, 2021				December 31, 2020
	Cost		Fair Value		Cost		Fair Value
Short-term investment maturities
Within 3 months	$	2,999,420	$	7,792,785	$	-	$	-
Between 3-12 months		28,927,635		24,130,500		-		-
Total	$	31,927,055	$	31,923,285	$	-	$	-

Summary of Investment Securities Gross Unrealized Gains (Losses)

	June 30, 2021					December 31, 2020
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 with unrealized gains	$	5,998,980	$	1,073		$	-	$	-
Investments with unrealized losses		25,924,305		(4,843	)		-		-
Total	$	31,923,285	$	(3,770	)	$	-	$	-

Summary of Net Realized Losses on Sales of Available for Sale Securities and Investment Income Interest and Dividends

Investment (loss) income, which includes net realized losses on sales of available for sale securities and investment income interest and dividends, is summarized as follows:

	2021			2020
	Three Months Ended June 30,
	2021			2020
Interest and dividends accrued and paid	$	1,436		$	18,095
Realized (losses) gains		(1,785	)		2,865
Investment (loss) income, net	$	(349	)	$	20,960

	2021			2020
	Six Months Ended June 30,
	2021			2020
Interest and dividends accrued and paid	$	3,847		$	63,172
Realized (losses) gains		(1,785	)		46,097
Investment income, net	$	2,062		$	109,269
Investment (loss) income, net		2,062			109,269

Fair Value Measurements (Tables)

6 Months Ended

Jun. 30, 2021

Fair Value Measurements

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 June 30, 2021
Investment in debt securities - available for sale, at fair value	$	31,923,285	$	–	$	31,923,285	$	–

Non-recurring items as of June 30, 2021
In-process R&D (Note 9)	$	13,366,234	$	–	$	–	$	13,366,234

Non-recurring items as of December 31, 2020
In-process R&D (Note 9)	$	13,366,234	$	–	$	–	$	13,366,234

Liabilities:

Recurring items as of June 30, 2021
Earn-out milestone liability (Note 14)	$	7,088,000	$	–	$	–	$	7,088,000

Recurring items as of December 31, 2020
Earn-out milestone liability (Note 14)	$	7,018,000	$	–	$	–	$	7,018,000

Intangible Assets (Tables)

6 Months Ended

Jun. 30, 2021

Goodwill and Intangible Assets Disclosure [Abstract]

Schedule of Fair Value of Assets Acquired

Following is a summary of the net fair value of the assets acquired in the EGEN asset acquisition for the six-month period ended June 30, 2021:

	IPR&D		Goodwill		Covenant Not To Compete
For the six-months ended June 30, 2021
Balance at January 1, 2021, net	$	13,366,234	$	1,976,101	$	113,660
Amortization		-		-		(113,660	)
Balance at June 30, 2021, net	$	13,366,234	$	1,976,101	$	-

Accrued Liabilities (Tables)

6 Months Ended

Jun. 30, 2021

Payables and Accruals [Abstract]

Schedule of Accrued Liabilities

Other accrued liabilities at June 30, 2021 and December 31, 2020 include the following:

Schedule of Accrued Liabilities

	June 30, 2021		December 31, 2020

Amounts due to contract research organizations and other contractual agreements	$	1,189,017	$	636,000
Accrued payroll and related benefits		1,016,610		1,736,271
Accrued professional fees		80,625		66,850
Accrued interest		7,042		-
Other		19,411		19,411
Total	$	2,312,705	$	2,458,532

Notes (Tables)

6 Months Ended

Jun. 30, 2021

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 fee, due on the SVB Loan Facility:

	As of June 30,
2022	$	–
2023		–
2024		3,000,000
2025 and thereafter		3,000,000
Subtotal of future principal payments		6,000,000
Unamortized debt premium, net		(236,913	)
Total	$	5,763,087

Schedule of Debt


Principal balance at June 18, 2021	$	5,000,000
Early termination fees		150,000
End of term charges		275,000
Total	$	5,425,000

Stock-Based Compensation (Tables)

6 Months Ended

Jun. 30, 2021

Share-based Payment Arrangement [Abstract]

Summary of Stock Option Awards and Restricted Stock Grants

	Stock Options					Restricted Stock Awards				Weighted Average
	Options Outstanding			Weighted Average Exercise Price		Non-vested Restricted Stock Outstanding		Weighted Average Grant Date Fair Value		Contractual Terms of Equity Awards (in years)
Equity awards outstanding at January 1, 2021		4,624,725		$	2.77		2,750	$	0.89

Equity awards granted		2,154,000		$	2.18		7,000	$	1.38

Equity awards exercised or vested and issued		(7,500	)	$	0.63		-	$	-

Equity awards forfeited, cancelled or expired		(92,646	)	$	2.69		-	$	-

Equity awards outstanding at June 30, 2021		6,678,579		$	2.58		9,750	$	1.27		8.0

Aggregate intrinsic value of outstanding equity awards at June 30, 2021	$	12,145				$	12,383

Equity awards exercisable at June 30, 2021		4,329,286		$	2.73						7.8

Aggregate intrinsic value of equity awards exercisable at June 30, 2021	$	1,650

Schedule of Assumptions Used to Determine Fair Value of Options Granted

Earn-Out Milestone Liability (Tables)

6 Months Ended

Jun. 30, 2021

Earn-out Milestone Liability

Schedule of Changes in Earn-out Milestone Liability

The following is a summary of the changes in the earn-out milestone liability for the six-month period ended June 30, 2021:


Balance at January 1, 2021	$	(7,018,000	)
Non-cash loss from the change in fair value		(70,000	)
Balance at June 30, 2021	$	(7,088,000	)

Schedule of Risk Adjustment Assessment

The following is a schedule of the Company’s risk-adjustment assessment of each milestone:

Schedule of Risk Adjustment Assessment

Date	Risk-adjustment Assessment of Achieving Each Milestone			Discount Rate			Estimated Time to Achieve

June 30, 2021		80	%		9	%	0.42 to 1.42 years
March 31, 2021		80	%		9	%	0.29 to 1.29 years
December 31, 2020		80	%		9	%	0.54 to 1.54 years

June 30, 2020		80	%		9	%	0.54 to 1.54 years
March 31, 2020		80	%		9	%	1.04 to 2.04 years
December 31, 2019		80	%		9	%	1.12 to 2.12 years

Warrants (Tables)

6 Months Ended

Jun. 30, 2021

Warrants

Summary of Warrant Activity

Following is a summary of all warrant activity for the six months ended June 30, 2021:

Summary of Warrant Activity

Warrants	Number of Warrants Issued			Weighted Average Exercise Price

Warrants outstanding at December 31, 2020		3,853,566		$	1.35

Warrants exercised during the six months ended June 30, 2021 (see Note 12)		(1,216,667	)	$	1.24

Warrants outstanding at June 30, 2021		2,636,899		$	1.40

Aggregate intrinsic value of outstanding warrants at June 30, 2021	$	159,857

Weighted average remaining contractual terms at June 30, 2021		4.6 years

Leases (Tables)

6 Months Ended

Jun. 30, 2021

Leases

Schedule of Lease Payments and Maturity of Operating Lease Liabilities

Following is a table of the lease payments and maturity of our operating lease liabilities as of June 30, 2021:

	For the year ending June 30,
Remainder of 2021	$	266,188
2022		535,579
2023		233,116
2024 and thereafter		-
Subtotal future lease payments		1,034,883
Less imputed interest		(101,664	)
Total lease liabilities	$	933,219

Weighted average remaining life		2.0 years

Weighted average discount rate		9.98	%

Financial Condition and Business Plan (Details Narrative) - USD ($)					1 Months Ended				6 Months Ended	12 Months Ended
	Jun. 16, 2021	May 10, 2021	Mar. 19, 2021	Aug. 28, 2020	Jun. 18, 2021	Jan. 31, 2021	Sep. 30, 2020	Jun. 30, 2018	Jun. 30, 2021	Dec. 31, 2019	Dec. 31, 2018	Apr. 05, 2021	Dec. 31, 2020
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Retained Earnings (Accumulated Deficit)									$ 323,137,741				$ 312,000,341
[custom:CashAndCashEquivalentsRestrictedCashShorttermInvestmentsAndReceivableOnSaleOfNetOperatingLosses-0]									64,500,000
[custom:ReceivableOnSaleOfNetOperatingLosses-0]									$ 1,850,000
Horizon Credit Agreement [Member] \| Horizon Technology Finance Corporation [Member]
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Proceeds from Contributed 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]
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Debt Instrument, Interest Rate, Stated Percentage								7.625%
Amendment to Horizon Credit Agreement [Member] \| Horizon Technology Finance Corporation [Member]
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Repayments of Notes Payable				5,000,000
Debt Instrument, Face Amount				5,000,000
Debt instrument related end term charges				$ 200,000
SVB Loan Facility [Member]
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Debt Instrument, Interest Rate, Stated Percentage					3.25%
Line of Credit Facility, Maximum Borrowing Capacity					$ 10,000,000
Line of Credit Facility, Remaining Borrowing Capacity					$ 4,000,000
Debt Instrument, Description					Payments under the loan agreement are interest only for the first 24 months after loan closing, followed by a 24-month amortization period of principal and interest through the scheduled maturity date.				Payments under the loan agreement are interest only for the first 24 months after loan closing, followed by a 24-month amortization period of principal and interest through the scheduled maturity date.
SVB Loan Facility [Member] \| Silicon Valley Bank [Member]
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Line of Credit Facility, Maximum Borrowing Capacity					$ 10,000,000				$ 10,000,000
Line of Credit Facility, Remaining Borrowing Capacity									$ 4,000,000
SVB Loan Facility [Member] \| Prime Rate [Member] \| Silicon Valley Bank [Member]
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Debt Instrument, Interest Rate, Stated Percentage									3.25%
SVB Loan Facility [Member] \| Horizon Technology Finance Corporation [Member]
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
[custom:RepaymentOfOutstandingIndebtednessAmount-0]									$ 6,000,000
Capital on DemandTM Sales Agreement [Member] \| Jones Trading Institutional Services, LLC [Member]
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
[custom:CashAndCashEquivalentsRestrictedCashShorttermInvestmentsAndReceivableOnSaleOfNetOperatingLosses-0]									$ 64,500,000
Proceeds from Contributed Capital			$ 6,900,000
Debt Instrument, Face Amount						$ 35,000,000						$ 15,000,000
Proceeds from Warrant Exercises						$ 1,500,000
New Jersey [Member]
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
[custom:NetProceedsFromSaleOfNetOperatingLosses]	$ 1,600,000						$ 2,000,000.0			$ 12,200,000	$ 13,000,000
New Jersey [Member] \| Minimum [Member]
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
[custom:NetProceedsFromSaleOfNetOperatingLosses]		$ 15,000,000
New Jersey [Member] \| Maximum [Member]
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
[custom:NetProceedsFromSaleOfNetOperatingLosses]	$ 1,400,000	$ 20,000,000

Schedule of Cash and Cash Equivalents and Restricted Cash (Details) - USD ($)	Jun. 30, 2021	Dec. 31, 2020	Jun. 30, 2020
Receivables [Abstract]
Cash and cash equivalents	$ 26,437,424	$ 17,164,177	$ 22,653,760
Money market investments, restricted	6,000,000
Total	$ 32,437,424		$ 22,653,760

Restricted Cash (Details Narrative) - USD ($)	1 Months Ended
Restricted Cash (Details Narrative) - USD ($)	Jun. 18, 2021	Jun. 30, 2021	Jun. 30, 2020
Discounted Future Net Cash Flows Relating to Proved Oil and Gas Reserves [Line Items]
Restricted Investments		$ 6,000,000
SVB Loan Facility [Member]
Discounted Future Net Cash Flows Relating to Proved Oil and Gas Reserves [Line Items]
Line of Credit Facility, Maximum Borrowing Capacity	$ 10,000,000
Line of Credit Facility, Description	the Company is required at all times to maintain on deposit with SVB as cash collateral in a segregated money market bank account in the name of the Company, unrestricted and unencumbered cash in an amount of at least 100% of the aggregate outstanding amount of the SVB loan facility. SVB may restrict withdrawals or transfers by or on behalf of the Company that would violate this requirement.
Silicon Valley Bank [Member] \| SVB Loan Facility [Member]
Discounted Future Net Cash Flows Relating to Proved Oil and Gas Reserves [Line Items]
Line of Credit Facility, Maximum Borrowing Capacity	$ 10,000,000	10,000,000
Restricted Investments		$ 6,000,000.0

Net Loss per Common Share (Details Narrative) - $ / shares	6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020
Earnings Per Share [Abstract]
clsn_NumberOfSharesOfCommonStockIssuableUponExerciseOfWarrantsAndEquityAwards	9,325,228	8,560,124
Class of Warrant or Right, Exercise Price of Warrants or Rights	$ 0.01
Description of Business		200,000

Schedule of Cost, Fair Value and Maturities of Short Term Investments (Details) - USD ($)	Jun. 30, 2021	Dec. 31, 2020
Marketable Securities [Line Items]
Short-term investments - Cost	$ 31,927,055
Short-term investments - Fair Value	31,923,285
Short-term investment maturities - Within 3 months, cost	2,999,420
Short-term investment maturities - Within 3 months, fair value	7,792,785
Short-term investment maturities - Between 3-12 months, cost	28,927,635
Short-term investment maturities - Between 3-12 months, fair value	24,130,500
Total, cost	31,927,055
Total, fair value	31,923,285
Commercial Paper [Member]
Marketable Securities [Line Items]
Short-term investments - Cost	7,795,035
Short-term investments - Fair Value	7,792,785
Government Backed Debt Securities [Member]
Marketable Securities [Line Items]
Short-term investments - Cost	24,132,020
Short-term investments - Fair Value	$ 24,130,500

Summary of Investment Securities Gross Unrealized Gains (Losses) (Details) - USD ($)	Jun. 30, 2021	Dec. 31, 2020
Investments, Debt and Equity Securities [Abstract]
Investments with unrealized gains, Fair Value	$ 5,998,980
Investments with unrealized gains, Unrealized Holding Gains (Losses)	1,073
Investments with unrealized losses, Fair Value	25,924,305
Investments with unrealized Losses, Unrealized Holding Gains (Losses)	(4,843)
Investment securities, available for sale	31,923,285
Investments with unrealized Gains (Losses), Unrealized Holding Gains (Losses)	$ (3,770)

Summary of Net Realized Losses on Sales of Available for Sale Securities and Investment Income Interest and Dividends (Details) - USD ($)	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Investments, Debt and Equity Securities [Abstract]
Interest and dividends accrued and paid	$ 1,436	$ 18,095	$ 3,847	$ 63,172
Realized (losses) gains	(1,785)	2,865	(1,785)	46,097
Investment (loss) income, net	$ (349)	$ 20,960	$ 2,062	$ 109,269

Investment in Debt Securities Available for Sale (Details Narrative) - USD ($)	Jun. 30, 2021	Dec. 31, 2020
Investments, Debt and Equity Securities [Abstract]
Investment in debt securities - available for sale, at fair value	$ 31,923,285

Schedule of Fair Value, Assets and Liabilities Measured on Recurring Basis (Details) - USD ($)	Jun. 30, 2021	Dec. 31, 2020
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]
Investment securities, available for sale	$ 31,923,285
Earn-out milestone liability	7,088,000	7,018,000
Fair Value, Recurring [Member]
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]
Earn-out milestone liability	7,088,000	7,018,000
Fair Value, Recurring [Member] \| Fair Value, Inputs, Level 1 [Member]
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]
Earn-out milestone liability
Fair Value, Recurring [Member] \| Fair Value, Inputs, Level 2 [Member]
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]
Earn-out milestone liability
Fair Value, Recurring [Member] \| Fair Value, Inputs, Level 3 [Member]
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]
Earn-out milestone liability	7,088,000	7,018,000
Fair Value, Recurring [Member] \| Corporate Debt Securities [Member]
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]
Investment securities, available for sale	31,923,285
Fair Value, Recurring [Member] \| Corporate Debt Securities [Member] \| Fair Value, Inputs, Level 1 [Member]
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]
Investment securities, available for sale
Fair Value, Recurring [Member] \| Corporate Debt Securities [Member] \| Fair Value, Inputs, Level 2 [Member]
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]
Investment securities, available for sale	31,923,285
Fair Value, Recurring [Member] \| Corporate Debt Securities [Member] \| Fair Value, Inputs, Level 3 [Member]
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]
Investment securities, available for sale
Fair Value, Nonrecurring [Member] \| Inprocess R&D [Member]
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]
Investment securities, available for sale	13,366,234	13,366,234
Fair Value, Nonrecurring [Member] \| Inprocess R&D [Member] \| Fair Value, Inputs, Level 1 [Member]
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]
Investment securities, available for sale
Fair Value, Nonrecurring [Member] \| Inprocess R&D [Member] \| Fair Value, Inputs, Level 2 [Member]
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]
Investment securities, available for sale
Fair Value, Nonrecurring [Member] \| Inprocess R&D [Member] \| Fair Value, Inputs, Level 3 [Member]
Fair Value, Investments, Entities that Calculate Net Asset Value Per Share [Line Items]
Investment securities, available for sale	$ 13,366,234	$ 13,366,234

Schedule of Fair Value of Assets Acquired (Details)	6 Months Ended
Schedule of Fair Value of Assets Acquired (Details)	Jun. 30, 2021 USD ($)
Finite-Lived Intangible Assets [Line Items]
Intangible assets, beginning balance	$ 113,660
Intangible assets, ending balance
Noncompete Agreements [Member]
Finite-Lived Intangible Assets [Line Items]
Intangible assets, beginning balance	113,660
Amortization	(113,660)
Intangible assets, ending balance
IPR&D [Member]
Finite-Lived Intangible Assets [Line Items]
Intangible assets, beginning balance	13,366,234
Amortization
Intangible assets, ending balance	13,366,234
Goodwill [Member]
Finite-Lived Intangible Assets [Line Items]
Intangible assets, beginning balance	1,976,101
Amortization
Intangible assets, ending balance	$ 1,976,101

Intangible Assets (Details Narrative) - USD ($)		3 Months Ended	6 Months Ended		12 Months Ended
Intangible Assets (Details Narrative) - USD ($)	Sep. 30, 2020	Sep. 30, 2020	Jun. 30, 2021	Jun. 30, 2020	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2020
Acquired Indefinite-lived Intangible Assets [Line Items]
Finite-Lived Intangible Assets, Net							$ 113,660
2018 Aspire Purchase Agreements [Member]
Acquired Indefinite-lived Intangible Assets [Line Items]
Finite-Lived Intangible Assets, Net							113,660
Finite-Lived Intangible Assets, Accumulated Amortization							$ 1,477,554
Glioblastoma Multiforme Brain Cancer [Member]
Acquired Indefinite-lived Intangible Assets [Line Items]
Asset Impairment Charges					$ 2,400,000
Glioblastoma Multiforme Brain Cancer [Member] \| Ovarian Cancer [Member]
Acquired Indefinite-lived Intangible Assets [Line Items]
Finite-lived Intangible Assets Acquired			13,300,000
EGEN Inc [Member]
Acquired Indefinite-lived Intangible Assets [Line Items]
Asset Impairment Charges						$ 7,000,000
Goodwill, Acquired During Period			2,000,000.0
EGEN Inc [Member] \| Purchase Agreement [Member]
Acquired Indefinite-lived Intangible Assets [Line Items]
Finite-lived Intangible Assets Acquired			$ 1,600,000
Finite-Lived Intangible Asset, Useful Life			7 years
Amortization				$ 56,830
EGEN Inc [Member] \| Glioblastoma Multiforme Brain Cancer [Member]
Acquired Indefinite-lived Intangible Assets [Line Items]
Asset Impairment Charges	$ 2,400,000					$ 9,400,000
[custom:NoncashCharge]		$ 2,400,000
EGEN Inc [Member] \| Glioblastoma Multiforme Brain Cancer [Member]
Acquired Indefinite-lived Intangible Assets [Line Items]
Indefinite-lived Intangible Assets Acquired			$ 24,200,000

Schedule of Accrued Liabilities (Details) - USD ($)	Jun. 30, 2021	Dec. 31, 2020
Payables and Accruals [Abstract]
Amounts due to contract research organizations and other contractual agreements	$ 1,189,017	$ 636,000
Accrued payroll and related benefits	1,016,610	1,736,271
Accrued professional fees	80,625	66,850
Accrued interest	7,042
Other	19,411	19,411
Total	$ 2,312,705	$ 2,458,532

Schedule of Future Principle Payments, Net of Unamortized Debt Discounts (Details)	Jun. 30, 2021 USD ($)
Debt Disclosure [Abstract]
2022
2023
2024	3,000,000
2025 and thereafter	3,000,000
Subtotal of future principal payments	6,000,000
Unamortized debt premium, net	(236,913)
Total	$ 5,763,087

- Definition

Amount, after unamortized (discount) premium and debt issuance costs, of long-term debt. Includes, but not limited to, notes payable, bonds payable, debentures, mortgage loans and commercial paper. Excludes capital lease obligations.

+ References + Details

Schedule of Debt (Details) - Horizon Technology Finance Corporation [Member]	Jun. 30, 2021 USD ($)
Entity Listings [Line Items]
Line of credit, beginning balance	$ 5,000,000
Early termination fees	150,000
End of term charges	275,000
Line of credit, ending balance	$ 5,425,000

- Definition

The carrying value as of the balance sheet date of the current and noncurrent portions of long-term obligations drawn from a line of credit, which is a bank's commitment to make loans up to a specific amount. Examples of items that might be included in the application of this element may consist of letters of credit, standby letters of credit, and revolving credit arrangements, under which borrowings can be made up to a maximum amount as of any point in time conditional on satisfaction of specified terms before, as of and after the date of drawdowns on the line. Includes short-term obligations that would normally be classified as current liabilities but for which (a) postbalance sheet date issuance of a long term obligation to refinance the short term obligation on a long term basis, or (b) the enterprise has entered into a financing agreement that clearly permits the enterprise to refinance the short-term obligation on a long term basis and the following conditions are met (1) the agreement does not expire within 1 year and is not cancelable by the lender except for violation of an objectively determinable provision, (2) no violation exists at the BS date, and (3) the lender has entered into the financing agreement is expected to be financially capable of honoring the agreement.

+ References + Details

Notes (Details Narrative) - USD ($)				1 Months Ended	3 Months Ended		6 Months Ended
Notes (Details Narrative) - USD ($)	Jun. 30, 2021	Aug. 28, 2020	Jun. 27, 2018	Jun. 18, 2021	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Short-term Debt [Line Items]
Interest and Debt Expense					$ 221,227	$ 340,602	$ 378,841	$ 679,967
Debt Issuance Costs, Net	$ 236,913				$ 236,913		$ 236,913
Class of Warrant or Right, Exercise Price of Warrants or Rights	$ 0.01				$ 0.01		$ 0.01
Initial Horizon Credit Agreement Amendment [Member]
Short-term Debt [Line Items]
Amortization of Debt Issuance Costs					$ 102,126	96,727	$ 139,428	192,793
Interest Expense, Debt					105,607	$ 243,299	225,920	$ 486,597
Horizon Technology Finance Corporation [Member]
Short-term Debt [Line Items]
Long-term Line of Credit	$ 5,425,000			$ 5,000,000	5,425,000		$ 5,425,000
[custom:EndOfTermFees]	275,000
SVB Loan Facility [Member]
Short-term Debt [Line Items]
Line of Credit Facility, Maximum Borrowing Capacity				10,000,000
Proceeds from Lines of Credit				6,000,000
Restricted cash				6,000,000.0
Line of Credit Facility, Remaining Borrowing Capacity				$ 4,000,000
Debt Instrument, Interest Rate, Stated Percentage				3.25%
Final payment percentage				3.00%
Long-term Line of Credit				$ 10,000,000
Line of Credit Facility, Commitment Fee Amount				$ 0
Debt Conversion, Converted Instrument, Warrants or Options Issued				0
Debt Instrument, Description				Payments under the loan agreement are interest only for the first 24 months after loan closing, followed by a 24-month amortization period of principal and interest through the scheduled maturity date.			Payments under the loan agreement are interest only for the first 24 months after loan closing, followed by a 24-month amortization period of principal and interest through the scheduled maturity date.
Interest and Debt Expense				$ 243,370
End of term charge percentage				3.00%
Amortization of Debt Issuance Costs				$ 300,000
Interest Expense, Debt							$ 7,042
Amortization of Debt Issuance Costs and Discounts							6,457
Initial Horizon Credit Agreement [Member]
Short-term Debt [Line Items]
Line of Credit Facility, Maximum Borrowing Capacity			$ 10,000,000
Proceeds from Lines of Credit			10,000,000
Line of Credit Facility, Remaining Borrowing Capacity			5,000,000
Interest and Debt Expense			$ 175,000
End of term charge percentage			4.00%
Debt Instrument, Fee Amount			$ 142,605
Loan Processing Fee			100,000
Debt Instrument, Unamortized Discount			782,116
Debt Issuance Costs, Net			400,000
Fair Value Adjustment of Warrants			507,116
[custom:EndOfTermFees]			$ 275,000
Initial Horizon Credit Agreement [Member] \| Common Stock [Member]
Short-term Debt [Line Items]
Class of Warrant or Right, Number of Securities Called by Warrants or Rights			190,114
Class of Warrant or Right, Exercise Price of Warrants or Rights			$ 2.63
Class of Warrant or Right, Outstanding			95,057
Amendment to Horizon Credit Agreement [Member] \| Horizon Technology Finance Corporation [Member]
Short-term Debt [Line Items]
Repayments of Notes Payable		$ 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 bore 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 were 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 on April 1, 2023. In addition, the remaining $5 million in obligations was subject to an end of term fee equal, in the aggregate, to $
Debt Instrument, Fee Amount		$ 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 agreed to provide evidence to Horizon on or before March 31, 2021, that it 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	$ 109,706	$ 200,000			$ 109,706		109,706
Debt Issuance Costs, Net		5,000
Payment for Debt Extinguishment or Debt Prepayment Cost		5,000,000
Warrants Not Settleable in Cash, Fair Value Disclosure		$ 247,548
Amendment to Horizon Credit Agreement [Member] \| Horizon Technology Finance Corporation [Member] \| Common Stock [Member]
Short-term Debt [Line Items]
Class of Warrant or Right, Number of Securities Called by Warrants or Rights		247,525
Class of Warrant or Right, Exercise Price of Warrants or Rights		$ 1.01
Warrants cancelled		95,057
Horizon Credit Agreement [Member]
Short-term Debt [Line Items]
Interest Expense, Debt							190,581
Gain (Loss) on Contract Termination							$ 234,419
Horizon Credit Agreement [Member] \| Horizon Technology Finance Corporation [Member]
Short-term Debt [Line Items]
Debt Instrument, Face Amount		$ 10,000,000

Stockholders’ Equity (Details Narrative) - USD ($)							1 Months Ended		3 Months Ended	6 Months Ended		12 Months Ended
Stockholders’ Equity (Details Narrative) - USD ($)	Mar. 19, 2021	Jan. 22, 2021	Sep. 08, 2020	Jun. 22, 2020	Feb. 27, 2020	Dec. 04, 2018	Mar. 31, 2021	Sep. 30, 2018	Mar. 31, 2021	Jun. 30, 2021	Jun. 30, 2020	Dec. 31, 2020	Mar. 12, 2020
Accumulated Other Comprehensive Income (Loss) [Line Items]
clsn_ShelfRegistrationStatementAmount	$ 100,000,000							$ 75,000,000
Proceeds from Issuance of Common Stock										$ 52,697,265	$ 18,182,599
Class of Warrant or Right, Exercise Price of Warrants or Rights										$ 0.01
Capital on DemandTM Sales Agreement [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Less than 12 months, unrealized gains, fair value						$ 16,000,000.0
Capital on Demand Agreement [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Stock Issued During Period, Shares, New Issues									7,200,000		1,200,000
Proceeds from Issuance of Common Stock									$ 6,900,000		$ 3,500,000
Securities Purchase Agreement [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
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]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Class of Warrant or Right, Number of Securities Called by Each Warrant or Right					2,971,428
Warrants and Rights Outstanding, Term					5 years
Class of Warrant or Right, Exercise Price of Warrants or Rights					$ 1.15
Exchange Agreements [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Class of Warrant or Right, Number of Securities Called by Each Warrant or Right										1,200,000
Proceeds from Issuance of Warrants										$ 1,500,000
Exchange Agreements [Member] \| Warrant [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Class of Warrant or Right, Number of Securities Called by Each Warrant or Right													3,200,000
Warrants and Rights Outstanding, Term													5 years
Class of Warrant or Right, Exercise Price of Warrants or Rights													$ 1.24
Underwriting Agreement [Member] \| Underwritten Offering [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
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
Share Price				3.4875
[custom:UnderwritingDiscountPricePerShare]				$ 0.2625
Payments from sale of nols				7.00%
Underwriting Agreement [Member] \| January 2021 Registered Direct Offering [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Stock Issued During Period, Shares, New Issues		25,925,925
Proceeds from Issuance of Common Stock		$ 35,000,000
Share Price		$ 1.35
Placement agent fee description.		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.
Underwriting Agreement [Member] \| March 2021 Registered Direct Offering [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Stock Issued During Period, Shares, New Issues							11,538,462
Proceeds from Issuance of Common Stock							$ 15,000,000
Share Price							$ 1.30		$ 1.30
Placement agent fee description.							In connection with the March 2021 Offering, the Company entered into a placement agent agreement (the “March 2021 Placement Agent Agreement”) with A.G.P./Alliance Global Partners, as lead placement agent (“AGP,” and together with JonesTrading Institutional Services LLC and Brookline Capital Markets, a division of Arcadia Securities, LLC, serving as co-placement agents, the “March 2021 Placement Agents”) pursuant to which the Company agreed to pay the March 2021 Placement Agents an aggregate cash fee equal to 7% of the aggregate gross proceeds raised from the sale of the securities sold in the Offering and reimburse the Placement Agents for certain of their expenses in an amount not to exceed $82,500.
LPC Purchase Agreement [Member] \| Lincoln Park Capital Fund, LLC [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Stock Issued During Period, Shares, New Issues			26,000,000.0									3,300,000
Proceeds from Issuance of Common Stock												$ 2,200,000
LPC Purchase Agreement [Member] \| LPC Commitment Shares [Member] \| Lincoln Park Capital Fund, LLC [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Stock Issued During Period, Shares, New Issues			437,828

Summary of Stock Option Awards and Restricted Stock Grants (Details) - USD ($)	6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Weighted Average Exercise Price, Options granted	$ 1.98	$ 3.10
Share-based Payment Arrangement, Option [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number Outstanding, Outstanding, Beginning balance	4,624,725
Weighted Average Exercise Price, Outstanding, Beginning balance	$ 2.77
Number Outstanding, Options granted	2,154,000
Weighted Average Exercise Price, Options granted	$ 2.18
Number Outstanding, Options exercised or vested and issued	(7,500)
Weighted Average Exercise Price, Options exercised or vested and issued	$ 0.63
Number Outstanding, Options canceled or expired	(92,646)
Weighted Average Exercise Price, Options canceled or expired	$ 2.69
Number Outstanding, Outstanding, Ending balance	6,678,579
Weighted Average Exercise Price, Outstanding, Ending balance	$ 2.58
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Weighted Average Remaining Contractual Term	8 years
Aggregate Intrinsic Value, Outstanding, Ending balance	$ 12,145
Number Outstanding, Exercisable, Ending balance	4,329,286
Weighted Average Exercise Price, Exercisable, Ending balance	$ 2.73
Share-based Compensation Arrangement by Share-based Payment Award, Options, Exercisable, Weighted Average Remaining Contractual Term	7 years 9 months 18 days
Aggregate Intrinsic Value, Exercisable, Ending balance	$ 1,650
Restricted Stock [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number Outstanding, Non-vested stock awards, Outstanding, Beginning balance	2,750
Weighted Average Grant Date Fair Value, Non-vested stock awards, Outstanding, Beginning balance	$ 0.89
Number Outstanding, Non-vested stock awards, Granted	7,000
Weighted Average Grant Date Fair Value, Non-vested stock awards, Granted	$ 1.38
Number Outstanding, Non-vested stock awards, exercised or vested and issued
Weighted Average Grant Date Fair Value, Non-vested stock awards, exercised or vested and issued
Number Outstanding, Non-vested stock awards, Forfeited
Weighted Average Grant Date Fair Value, Non-vested stock awards, Forfeited
Number Outstanding, Non-vested stock awards, Outstanding, Ending balance	9,750
Weighted Average Grant Date Fair Value, Non-vested stock awards, Outstanding, Ending balance	$ 1.27
Aggregate Intrinsic Value, Non-vested stock awards, Outstanding, Ending balance	$ 12,383

Schedule of Assumptions Used to Determine Fair Value of Options Granted (Details)	6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based Compensation Arrangement by Share-based Payment Award, Fair Value Assumptions, Risk Free Interest Rate, Minimum	1.56%	0.71%
Share-based Compensation Arrangement by Share-based Payment Award, Fair Value Assumptions, Risk Free Interest Rate, Maximum	1.74%	1.33%
Share-based Compensation Arrangement by Share-based Payment Award, Fair Value Assumptions, Expected Volatility Rate, Minimum	106.80%	100.40%
Share-based Compensation Arrangement by Share-based Payment Award, Fair Value Assumptions, Expected Volatility Rate, Maximum	113.00%	104.20%
Expected dividend yield
Minimum [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based Compensation Arrangement by Share-based Payment Award, Fair Value Assumptions, Expected Term	7 years 6 months	8 years 6 months
Maximum [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based Compensation Arrangement by Share-based Payment Award, Fair Value Assumptions, Expected Term	10 years	10 years

Stock-Based Compensation (Details Narrative) - USD ($)			3 Months Ended		6 Months Ended
Stock-Based Compensation (Details Narrative) - USD ($)	Feb. 19, 2019	Sep. 28, 2018	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020	Jun. 10, 2021	Jun. 15, 2020	May 14, 2019
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based Compensation Arrangements by Share-based Payment Award, Options, Grants in Period, Weighted Average Exercise Price					$ 1.98	$ 3.10
Share-based Payment Arrangement, Nonvested Award, Cost Not yet Recognized, Amount			$ 3,200,000		$ 3,200,000
Share-based Payment Arrangement, Nonvested Award, Cost Not yet Recognized, Period for Recognition					1 year 2 months 12 days
Equity Stock Awards [Member] \| Granted Under 2018 Plan and 2007 Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Common Stock, Capital Shares Reserved for Future Issuance			6,548,325		6,548,325
Inducement Awards [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Common Stock, Capital Shares Reserved for Future Issuance			140,004		140,004
Stock Options and Restricted Stock Awards [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based Payment Arrangement, Expense			$ 793,619	$ 578,761	$ 2,372,945	$ 1,030,726
Stock Options and Restricted Stock Awards [Member] \| Research and Development Expense [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based Payment Arrangement, Expense			299,581	200,186	882,088	378,122
Stock Options and Restricted Stock Awards [Member] \| General and Administrative Expense [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based Payment Arrangement, Expense			$ 494,038	$ 378,575	$ 1,490,857	$ 652,604
2018 Stock Incentive Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based Compensation Arrangement by Share-based Payment Award, Number of Shares Authorized			2,700,000		2,700,000
Common Stock, Capital Shares Reserved for Future Issuance			14,198,424		14,198,424
2018 Stock Incentive Plan [Member] \| Minimum [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based Compensation Arrangement by Share-based Payment Award, Number of Shares Available for Grant							7,700,000	2,500,000	1,200,000
2018 Stock Incentive Plan [Member] \| Maximum [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based Compensation Arrangement by Share-based Payment Award, Number of Shares Available for Grant							14,100,000	6,400,000	3,900,000
2007 Stock Incentive Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
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]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based Compensation Arrangements by Share-based Payment Award, Options, Grants in Period, Weighted Average Exercise Price	$ 2.18	$ 2.77
Share-based Compensation Arrangement by Share-based Payment Award, Award Vesting Period	3 years
Inducement Option Grants [Member] \| Five New Employees [Member] \| Restricted Stock [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares, Issued	13,000	19,000
Inducement Option Grants [Member] \| Five New Employees [Member] \| Common Stock [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares, Issued	140,004	164,004
2018 Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Common Stock, Capital Shares Reserved for Future Issuance			7,650,099		7,650,099

Schedule of Changes in Earn-out Milestone Liability (Details)	6 Months Ended
	Jun. 30, 2021 USD ($)
Earn-out Milestone Liability
Earn-out liabilities, beginning balance	$ (7,018,000)
Non-cash gain loss from the adjustment for the change in fair value	(70,000)
Earn-out liabilities, ending balance	$ (7,088,000)

Schedule of Risk Adjustment Assessment (Details)	3 Months Ended		6 Months Ended		12 Months Ended
Schedule of Risk Adjustment Assessment (Details)	Mar. 31, 2021	Mar. 31, 2020	Jun. 30, 2021	Jun. 30, 2020	Dec. 31, 2020	Dec. 31, 2019
SEC Schedule, 12-18, Supplemental Information, Property-Casualty Insurance Underwriters [Line Items]
Risk-adjustment Assessment of achieving each Milestone	80.00%	80.00%	80.00%	80.00%	80.00%	80.00%
Discount Rate	9.00%	9.00%	9.00%	9.00%	9.00%	9.00%
Minimum [Member]
SEC Schedule, 12-18, Supplemental Information, Property-Casualty Insurance Underwriters [Line Items]
[custom:EstimatedTimeToAchieveMileStone]	3 months 14 days	1 year 14 days	5 months 1 day	6 months 14 days	6 months 14 days	1 year 1 month 13 days
Maximum [Member]
SEC Schedule, 12-18, Supplemental Information, Property-Casualty Insurance Underwriters [Line Items]
[custom:EstimatedTimeToAchieveMileStone]	1 year 3 months 14 days	2 years 14 days	1 year 5 months 1 day	1 year 6 months 14 days	1 year 6 months 14 days	2 years 1 month 13 days

Earn-Out Milestone Liability (Details Narrative) - USD ($) $ in Millions	3 Months Ended				6 Months Ended		12 Months Ended
	Jun. 30, 2021	Mar. 31, 2021	Jun. 30, 2020	Mar. 31, 2020	Jun. 30, 2021	Jun. 30, 2020	Dec. 31, 2020	Dec. 31, 2019	Mar. 28, 2019
EGWC, Inc [Member]
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Non-cash charge on earnout milestone liability	$ 0.1		$ 0.2		$ 0.1	$ 0.3
[custom:EarnoutPaymentOptionsDescription]					In assessing the earnout milestone liability at June 30, 2021 and March 31, 2021, the Company fair valued each of the two payment options per the Amended Asset Purchase Agreement and weighted them at 50% / 50% probability for the $7.0 million and the $12.4 million payments, respectively.	In assessing the earnout milestone liability at June 30, 2020 and March 31, 2020, the Company fair valued each of the two payment options per the Amended Asset Purchase Agreement and weighted them at 80% / 20% probability for the $7.0 million and the $12.4 million payments, respectively.
Amended Asset Purchase Agreement [Member]
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Earnout milestone liability									$ 12.4
Amended Asset Purchase Agreement [Member] \| Within One Year of Achieving Milestone [Member]
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Earnout milestone liability									12.4
Amended Asset Purchase Agreement [Member] \| 10 Business Days of Achieving Milestone [Member]
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Earnout milestone liability									$ 7.0
Fair Value Earnout Milestone Liability [Member] \| EGWC, Inc [Member]
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Business Combination, Consideration Transferred, Liabilities Incurred		$ 7.2		$ 5.8	$ 7.1	$ 6.0	$ 7.0	$ 5.7

Summary of Warrant Activity (Details)	6 Months Ended
Summary of Warrant Activity (Details)	Jun. 30, 2021 USD ($) $ / shares shares
Warrants
Number of Warrants Issued, Warrants outstanding, Beginning balance \| shares	3,853,566
Weighted Average Exercise Price, Warrants outstanding, Beginning balance \| $ / shares	$ 1.35
Number of Warrants Issued, Warrants exercised \| shares	(1,216,667)
Weighted Average Exercise Price, Warrants exercised \| $ / shares	$ 1.24
Number of Warrants Issued, Warrants outstanding, Ending balance \| shares	2,636,899
Weighted Average Exercise Price, Warrants outstanding, Ending balance \| $ / shares	$ 1.40
Aggregate intrinsic value of outstanding warrants \| $	$ 159,857
Weighted average remaining contractual terms (years)	4 years 7 months 6 days

Schedule of Lease Payments and Maturity of Operating Lease Liabilities (Details) - USD ($)	Jun. 30, 2021	Jan. 02, 2019
Leases
Remainder of 2021	$ 266,188
2022	535,579
2023	233,116
2024 and thereafter
Subtotal future lease payments	1,034,883
Less imputed interest	(101,664)
Total lease liabilities	$ 933,219	$ 1,900,000
Operating Lease, Weighted Average Remaining Lease Term	2 years
Operating Lease, Weighted Average Discount Rate, Percent	9.98%

Leases (Details Narrative)		1 Months Ended		3 Months Ended		6 Months Ended
Leases (Details Narrative)	Jan. 02, 2019 USD ($)	Jan. 31, 2018 USD ($)	Jul. 31, 2011 ft²	Jun. 30, 2021 USD ($)	Jun. 30, 2020 USD ($)	Jun. 30, 2021 USD ($)	Jun. 30, 2020 USD ($)	Dec. 31, 2020 USD ($) ft²
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate [Line Items]
Lessee, Operating Lease, Description			In 2011, the Company executed a lease (the “Lease”) with Brandywine Operating Partnership, L.P. (Brandywine), a Delaware limited partnership, for a
Area of Land \| ft²			10,870
Lessee, Operating Lease, Term of Contract			66 months
Lease Expiration Date			Apr. 30, 2017
Operating Lease, Right-of-Use Asset	$ 400,000			$ 840,195		$ 840,195		$ 1,047,336
Operating Lease, Liability	1,900,000			933,219		933,219
Right-of-Use Asset Obtained in Exchange for Operating Lease Liability	1,800,000
Operating Lease, Payments						264,546	$ 262,084
Accounting Standards Update 2016-02 [Member]
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate [Line Items]
Operating Lease, Right-of-Use Asset	1,400,000
Operating Lease, Liability	1,500,000
Other Liabilities	$ 100,000
Huntsville Alabama [Member]
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate [Line Items]
Area of Land \| ft²								11,500
1st Lease Amendment [Member] \| First Year [Member]
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate [Line Items]
Payments for Rent						18,900
1st Lease Amendment [Member] \| Final Year [Member]
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate [Line Items]
Payments for Rent						20,500
2nd Lease Amendment [Member] \| First Year [Member]
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate [Line Items]
Payments for Rent						25,035
2nd Lease Amendment [Member] \| Final Year [Member]
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate [Line Items]
Payments for Rent						27,088
EGEN Asset Purchase Agreement [Member]
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate [Line Items]
Lessee, Operating Lease, Description		In connection with the EGEN Asset Purchase Agreement in June 2014, the Company assumed the existing lease with another landlord for an
Payments for Rent		$ 18,100
Operating Leases [Member]
SEC Schedule, 12-29, Real Estate Companies, Investment in Mortgage Loans on Real Estate [Line Items]
Operating Lease, Cost				130,595	$ 130,595	261,190	261,190
Operating Lease, Payments				$ 132,684	$ 131,452	$ 264,546	$ 262,084

Technology Development and Licensing Agreements (Details Narrative) - USD ($)		6 Months Ended
	Jan. 18, 2013	Jun. 30, 2021
Accounts, Notes, Loans and Financing Receivable [Line Items]
[custom:UpfrontPaymentBeingRecognized]		$ 5,000,000
Hisun [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Proceeds from License Fees Received	$ 5,000,000
Deferred Revenue	$ 5,000,000.0
clsn_DeferredRevenueAmortizationPeriod	10 years

Commitments and Contingencies (Details Narrative) - USD ($)	Oct. 02, 2020	Apr. 24, 2020
Commitments and Contingencies Disclosure [Abstract]
Litigation Settlement, Expense		$ 187,500
Payments for Legal Settlements	$ 187,500