Enzon Pharmaceuticals (ENZN) 10-K 16 Feb 23 2022 FY Annual report Financial data

Document and Entity Information

Document and Entity Information - USD ($)	12 Months Ended
	Dec. 31, 2022	Feb. 10, 2023	Jun. 30, 2022
Document and Entity Information
Document Type	10-K
Document Annual Report	true
Document Transition Report	false
Document Period End Date	Dec. 31, 2022
Amendment Flag	false
Document Fiscal Year Focus	2022
Document Fiscal Period Focus	FY
Entity Registrant Name	Enzon Pharmaceuticals, Inc.
Entity Central Index Key	0000727510
Current Fiscal Year End Date	--12-31
Entity File Number	001-36435
Entity Incorporation, State or Country Code	DE
Entity Tax Identification Number	22-2372868
Entity Address, Address Line One	20 Commerce Drive (Suite 135)
Entity Address, City or Town	Cranford
Entity Address, State or Province	NJ
Entity Address, Postal Zip Code	07016
City Area Code	732
Local Phone Number	980-4500
Title of 12(g) Security	Common Stock, $0.01 par value
Trading Symbol	ENZN
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		74,214,603
Entity Well-known Seasoned Issuer	No
Entity Voluntary Filers	No
Entity Public Float			$ 11,766,830
ICFR Auditor Attestation Flag	false
Auditor Name	EisnerAmper LLP
Auditor Firm ID	274
Auditor Location	Philadelphia, Pennsylvania

CONSOLIDATED BALANCE SHEETS

CONSOLIDATED BALANCE SHEETS - USD ($) $ in Thousands	Dec. 31, 2022	Dec. 31, 2021
Current assets:
Cash and cash equivalents	$ 46,982	$ 47,641
Royalty receivable		28
Other current assets	405	85
Total current assets	47,387	47,754
Deferred tax asset	202
Total assets	47,589	47,754
Current liabilities:
Accounts payable	331	331
Accrued expenses and other current liabilities	93	72
Dividends payable on Series C preferred stock	1,275
Total current liabilities	1,699	403
Commitments and contingencies
Stockholders' equity:
Preferred stock - $0.01 par value, authorized 2,960,000 shares; no shares issued and outstanding at December 31, 2022 and 2021
Common stock - $0.01 par value, authorized 170,000,000 shares; issued and outstanding 74,214,603 shares at December 31, 2022 and 2021	742	742
Additional paid-in capital	74,708	75,983
Accumulated deficit	(72,043)	(71,857)
Total stockholders' equity	3,407	4,868
Total liabilities, mezzanine equity and stockholders' equity	47,589	47,754
Mezzanine Equity - Series C Preferred Stock
Mezzanine equity:
Series C preferred stock - $0.01 par value, 40,000 shares authorized, issued and outstanding (liquidation value $1,062 per share ) at December 31, 2022 and 2021	$ 42,483	$ 42,483

CONDENSED CONSOLIDATED BALANCE

CONDENSED CONSOLIDATED BALANCE SHEETS (Parenthetical) - $ / shares	Dec. 31, 2022	Dec. 31, 2021
Mezzanine equity
Preferred stock, par value (in dollars per share)	$ 0.01	$ 0.01
Preferred stock, shares authorized	2,960,000	2,960,000
Preferred stock, shares issued	0	0
Preferred stock, shares outstanding	0	0
Common stock, par value (in dollars per share)	$ 0.01	$ 0.01
Common stock, shares authorized	170,000,000	170,000,000
Common stock, shares issued	74,214,603	74,214,603
Common stock, shares outstanding	74,214,603	74,214,603
Mezzanine Equity - Series C Preferred Stock
Mezzanine equity
Preferred stock, par value	$ 0.01	$ 0.01
Preferred Shares, shares authorized	40,000	40,000
Preferred stock, shares issued	40,000	40,000
Preferred stock, shares outstanding	40,000	40,000
Preferred stock, liquidation value (per share)	$ 1,062	$ 1,062
Preferred stock, shares authorized		3,000,000

CONSOLIDATED STATEMENTS OF OPER

CONSOLIDATED STATEMENTS OF OPERATIONS - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021
Revenues:
Royalties and milestones, net	$ 26	$ 701
Total revenues	26	701
Operating expenses:
General and administrative	1,058	1,170
Total operating expenses	1,058	1,170
Operating loss	(1,032)	(469)
Other income	646	7
Loss before income tax benefit (expense)	(386)	(462)
Income tax benefit (expense)	200	(7)
Net loss	(186)	(469)
Dividends on Series C preferred stock	(1,275)	(2,023)
Net loss available to common shareholders	$ (1,461)	$ (2,492)
Loss per common share
Loss per common share - Basic	$ (0.02)	$ (0.03)
Loss per common share - Diluted	$ (0.02)	$ (0.03)
Weighted average number of common shares
Weighted-average number of common shares outstanding - Basic	74,215	74,215
Weighted-average number of common shares outstanding - Diluted	74,215	74,215

CONDENSED CONSOLIDATED STATEMEN

CONDENSED CONSOLIDATED STATEMENTS OF MEZZANINE EQUITY AND STOCKHOLDERS' EQUITY - USD ($) $ in Thousands	Mezzanine Equity - Series C Preferred Stock Preferred Stock	Mezzanine Equity - Series C Preferred Stock	Common Stock	Additional Paid-in Capital	Accumulated Deficit	Total
Balance at Dec. 31, 2020	$ 40,460		$ 742	$ 78,006	$ (71,388)	$ 7,360
Balance (in shares) at Dec. 31, 2020	40		74,215
Net loss	$ 0		$ 0	0	(469)	(469)
Preferred stock dividend accumulation	2,023			(2,023)		(2,023)
Balance at Dec. 31, 2021	$ 42,483		$ 742	75,983	(71,857)	4,868
Balance (in shares) at Dec. 31, 2021	40		74,215
Balance at Dec. 31, 2021		$ 42,483
Balance (in shares) at Dec. 31, 2021		40,000
Net loss	$ 0		$ 0	0	(186)	(186)
Preferred stock dividend accumulation				(1,275)		(1,275)
Balance at Dec. 31, 2022	$ 42,483		$ 742	$ 74,708	$ (72,043)	$ 3,407
Balance (in shares) at Dec. 31, 2022	40		74,215
Balance at Dec. 31, 2022		$ 42,483
Balance (in shares) at Dec. 31, 2022		40,000

CONSOLIDATED STATEMENTS OF CASH

CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($)	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021
Cash flows from operating activities:
Net loss	$ (186,000)	$ (469,000)
Adjustments to reconcile net loss to net cash used in operating activities:
Deferred income taxes	(202,000)
Changes in operating assets and liabilities:
Decrease (increase) in royalty receivable	28,000	(23,000)
Increase in other current assets	(320,000)
Increase in accounts payable		29,000
Increase (decrease) increase in accrued expenses and other current liabilities	21,000	(38,000)
Net cash used in operating activities	(659,000)	(501,000)
Net decrease in cash	(659,000)	(501,000)
Cash and cash equivalents at beginning of year	47,641,000	48,142,000
Cash and cash equivalents at end of year	46,982,000	47,641,000
Series C Preferred Stock
Non-cash financing activities:
Declaration of dividend for Series C Preferred Stock	$ 1,275,000
Accretion of dividend for Series C Preferred Stock		$ 2,023,000

Description of Business

Description of Business	12 Months Ended
	Dec. 31, 2022
Description of Business.
Description of Business	(1) Description of Business Enzon Pharmaceuticals, Inc. (together with its subsidiaries, the “Company,” “Enzon,” “we” or “us”) is positioned as a public company acquisition vehicle, where it can become an acquisition platform and more fully utilize its net operating loss carryforwards (“NOLs”) and enhance stockholder value. In September 2020, the Company initiated a rights offering for its common and preferred stock (see below and Note 13 to our Condensed Consolidated Financial Statements), which closed in October 2020, and it realized $43.6 million in gross proceeds. This has enabled the Company to embark on its plan to realize the value of its more than $100 million net NOLs by acquiring potentially profitable businesses or assets. To protect the NOLs, in August 2020, the Company’s Board of Directors (the “Board”) adopted a Section 382 rights plan (see Note 12 to our Condensed Consolidated Financial Statements). Historically, the Company had received royalty revenues from licensing arrangements with other companies primarily related to sales of certain drug products that utilized Enzon’s proprietary technology. In recent years, the Company has had no clinical operations and limited corporate operations. Enzon has a marketing agreement in the drug Vicineum, which, if approved, will, potentially, generate milestone and royalty payments to it in the future. Enzon cannot assure you that it will earn material future royalties or milestones. The Board and the Company’s management are actively involved in pursuing, sourcing, reviewing and evaluating various potential acquisition transactions consistent with its long-term strategy. The Company’s management and Board have made a number of contacts and engaged in discussions with principals of individual companies and financial advisors on behalf of various individual companies, while continuing to evaluate potential transactions. To date, no actionable transactions have been initiated. The Company has a marketing agreement with Micromet AG, now part of Amgen, Inc. (the “Micromet Agreement”), pursuant to which it may be entitled to certain milestone and royalty payments if Vicineum, a drug being developed by Sesen, Inc., (Sesen”) is approved for the treatment of non-muscle invasive bladder cancer. Based on the U.S. Food and Drug Administration (the “FDA”) accepting Sesen’s Biologic License Application (“BLA”) for Vicineum, the Company earned a milestone of $409,430 in the first quarter of 2021. In a series of announcements, Sesen described a number of regulatory issues that developed with the FDA, which caused it to voluntarily pause further development of Vicineum in the United States. Sesen also stated that the decision was based on a thorough reassessment of Vicineum following recent discussions with the FDA. Sesen stated that it continued to believe Vicineum has benefits for patients and healthcare providers that can be maximized through a company with a larger infrastructure, and as such, intended to seek a partner that could execute further development to realize the full potential of Vicineum. As a result of this decision, Sesen stated that it turned its primary focus to the careful assessment of potential strategic alternatives. On September 21, 2022, Sesen announced that it had entered into a definitive merger agreement with Carisma Therapeutics Inc. (“Carisma”) and that the combined company will focus on the advancement of Carisma’s proprietary cell therapy for the treatment of cancer and other disorders. Sesen also stated that it intends to seek a partner for the further development of Vicineum. On February 2, 2023, in an SEC filing, Sesen noted that given ongoing discussions with potential partners, completing a sale of Vicineum may be challenging. In a filing with the SEC in March 2021, Sesen noted that it had received notice from the European Medicines Agency that its Marketing Authorization Application for Vicineum was found to be valid and the review procedure had officially started. Accordingly, the Company earned and received an additional milestone of $292,284 in the second quarter of 2021. Subsequently, on August 25, 2021, Sesen announced that it had withdrawn its application to market Vicineum in Europe. During the fourth quarters of 2022 and 2021, we received a license maintenance fee of approximately $26,000 and $28,000, respectively, from Amgen, Inc. in payment of a worldwide, royalty-free non-exclusive right to license Vicineum. The fee represents half of the amount paid by Viventia Biotech (Barbados) Inc. (“Viventia”), part of Sesen, on an annual basis for the continued right to license Vicineum. In August 2020, the Board adopted a Section 382 rights plan and declared a dividend distribution of one right for each outstanding share of the Company’s common stock to stockholders of record at the close of business on August 24, 2020. (See Note 12 to the Consolidated Financial Statements.) ​ In September 2020, the Board approved a Rights Offering (the “Rights Offering”), by which the Company distributed, at no charge to all holders of its common stock on September 23, 2020 (the “Record Date”), transferable subscription rights to purchase units (“Units”) at a subscription price per Unit of $1,090. In the Rights Offering, each stockholder on the Record Date received one subscription right for every share of common stock owned on the Record Date. For every 1,105 subscription rights held, a stockholder was entitled to purchase one Unit at the subscription price. Each Unit consisted of one share of newly designated Series C Preferred Stock, par value $0.01 per share, and 750 shares of the Company’s common stock. The subscription period for the Rights Offering ended on October 9, 2020. As a result of the sale of all 40,000 Units available for purchase in the Rights Offering, the Company received approximately $43.6 million of gross proceeds and had 40,000 shares of Series C Preferred Stock outstanding and an aggregate of 74,214,603 shares of common stock outstanding following the Rights Offering. (See Note 13 to the Consolidated Financial Statements.) On an annual basis, the Board may, at its sole discretion, cause a dividend with respect to the Series C Preferred Stock to be paid in cash to the holders in an amount equal to 3% of the liquidation preference as in effect at such time (initially $1,000 per share). If the dividend is not so paid in cash, the liquidation preference is adjusted and increased annually by an amount equal to 5% of the liquidation preference per share as in effect at such time, that is not paid in cash to the holders on such date. The Board did not declare a dividend as of December 31, 2021 and, at December 31, 2021 the liquidation value of the Series C Preferred Stock was $1,062 per share. On December 29, 2022, the Board declared a cash dividend of 3% on the Series C Preferred Stock, aggregating $1,274,400 or $31.86 per share. Accordingly, the cumulative liquidation value of the Series C Preferred Stock was approximately $42,483,000 ($1,062 per share) on December 31, 2022. The dividend was paid on January 17, 2023 to the holders of record of the Company’s Series C Preferred Stock as of January 10, 2023. (See Note 14 to the Consolidated Financial Statements.) The Company maintains its principal executive offices at 20 Commerce Drive, Suite 135, Cranford, New Jersey 07016 through a service agreement with Regus Management Group, LLC.

Summary of Significant Accounti

Summary of Significant Accounting Policies	12 Months Ended
	Dec. 31, 2022
Summary of Significant Accounting Policies
Summary of Significant Accounting Policies	(2) Summary of Significant Accounting Policies Principles of Consolidation The consolidated financial statements include the accounts of Enzon Pharmaceuticals, Inc. and its wholly owned subsidiaries. All intercompany balances and transactions have been eliminated as part of the consolidation. Use of Estimates The preparation of consolidated financial statements in conformity with accounting principles generally accepted in the United States of America (“U.S. GAAP”) requires management to make estimates and assumptions that affect reported amounts of assets and liabilities, disclosures of contingent assets and liabilities at the date of the financial statements, and the reported amounts of revenues and expenses during the reporting period. These estimates include legal and contractual contingencies and income taxes. Although management bases its estimates on historical experience, relevant current information and various other assumptions that are believed to be reasonable under the circumstances, actual results could differ from these estimates. Financial Instruments and Fair Value The carrying values of cash and cash equivalents, royalty receivable, other current assets, accounts payable, accrued expenses and other current liabilities in the Company’s consolidated balance sheets approximated their fair values at December 31, 2022 and 2021 due to their short-term nature. As of each of December 31, 2022 and 2021, the Company held cash equivalents aggregating approximately $44.2 million and $43.6 million, respectively. Revenue Recognition Royalty revenues from the Company’s agreements with third parties and pursuant to the sale of the Company’s former specialty pharmaceutical business are recognized when the Company can reasonably determine the amounts earned. In most cases, this will be upon notification from the third-party licensee, which is typically during the quarter following the quarter in which the sales occurred. The Company does not participate in the selling or marketing of products for which it receives royalties. Because the Company records revenue only when collection is assured, no provision for uncollectible accounts is established upon recognition of revenues. Contingent payments with third parties and pursuant to the sale of the Company’s former specialty pharmaceutical business are recognized as income when the milestone has been achieved and collection is assured, such payments are non-refundable and no further effort is required on the part of the Company or the other party to complete the earning process. Income Taxes Income taxes are accounted for under the asset and liability method. Deferred tax assets and liabilities are recognized for the estimated future tax consequences attributable to differences between the financial statement carrying amounts of existing assets and liabilities and their respective tax bases and operating loss and tax credit carryforwards. Deferred tax assets and liabilities are measured using enacted tax rates expected to apply to taxable income in the years in which those temporary differences are expected to be realized. The effect of a change in tax rates or laws on deferred tax assets and liabilities is recognized in operations in the period that includes the enactment date of the rate change. A valuation allowance is established to reduce the deferred tax assets to the amounts that are more likely than not to be realized from operations. Tax benefits of uncertain tax positions are recognized only if it is more likely than not that the Company will be able to sustain a position taken on an income tax return. The Company has no liability for uncertain tax positions. Interest and penalties, if any, related to unrecognized tax benefits would be recognized as income tax expense. ​

Recent Accounting Pronouncement

Recent Accounting Pronouncements	12 Months Ended
	Dec. 31, 2022
Recent Accounting Pronouncements
Recent Accounting Pronouncements	(3) Recent Accounting Pronouncements Recent Accounting Standards Updates issued by the Financial Accounting Standards Board (the “FASB”) and guidance issued by the Securities and Exchange Commission did not, or are not believed by management to, have a material effect on the Company’s present or future consolidated financial statements.

Accounts Payable, Accrued Expen

Accounts Payable, Accrued Expenses and Dividends Payable on Series C Preferred Stock	12 Months Ended
	Dec. 31, 2022
Accounts Payable, Accrued Expenses and Dividends Payable on Series C Preferred Stock
Accounts Payable, Accrued Expenses and Dividends Payable on Series C Preferred Stock	(4) Accounts Payable, Accrued Expenses and Dividends Payable on Series C Preferred Stock Prior to 2017, the Company’s primary source of royalty revenues was derived from sales of PegIntron, which is marketed by Merck & Co., Inc. (“Merck”). At December 31, 2021, we recorded a liability to Merck of approximately $331,000, based primarily on Merck’s assertions regarding recoupments related to prior returns and rebates. During the year ended December 31, 2022, no additional royalties/(recoupments) related to PegIntron were claimed by Merck. As such, as asserted by Merck, the Company’s recorded liability to Merck remained at $331,000 at December 31, 2022. During the year ended December 31, 2021, net recoupments from PegIntron were approximately $28,000. The Company believes that it will receive little or no future royalties from Merck, but may be charged with additional chargebacks from returns and rebates in amounts that, based on current estimates, are not expected to be material. Accrued expenses and other current liabilities consisted of the following as of December 31, 2022 and 2021 (in thousands): ​ ​ ​ ​ ​ ​ ​ ​ ​ December 31, December 31, ​ ​ 2022 ​ 2021 Professional and consulting fees ​ $ 87 ​ $ 61 Other ​ 6 ​ 11 ​ ​ $ 93 ​ $ 72 ​ On December 29, 2022, the Board declared a cash dividend of 3% of the liquidation preference ($42,483,286) of the Series C Preferred Stock, aggregating $1,274,400 ($31.86 per share). Such dividend was accrued at December 31, 2022 and paid on January 17, 2023.

Stockholders' Equity

Stockholders' Equity	12 Months Ended
	Dec. 31, 2022
Stockholders' Equity
Stockholders' Equity	(5) Stockholders’ Equity Preferred Stock The Company has authorized 3,000,000 shares of preferred stock in one or more series of which, at December 31, 2021, 40,000 shares have been issued, are outstanding Common Stock As of December 31, 2022, the Company reserved 9,818,392 shares of its common stock for the non-qualified and incentive stock plans.

Cash Dividend

Cash Dividend	12 Months Ended
	Dec. 31, 2022
Cash Dividend
Cash Dividend	(6) Cash Dividend No dividend on the shares of the Company’s common stock has been paid or declared during the years ended December 31, 2022 and 2021. On December 29, 2022, the Board declared a cash dividend of 3% on the Series C Preferred Stock, aggregating $1,274,400 or $31.86 per share. Accordingly, the cumulative liquidation value of the Series C Preferred Stock was approximately $42,483,000 ($1,062 per share) on December 31, 2022. The dividend was paid on January 17, 2023 to the holders of record of the Company’s Series C Preferred Stock as of January 10, 2023 (See Note 14 to the Consolidated Financial Statements).

Loss Per Common Share

Loss Per Common Share	12 Months Ended
	Dec. 31, 2022
Loss Per Common Share
Loss Per Common Share	(7) Loss Per Common Share Basic earnings (loss) per common share (EPS) is calculated by dividing net income (loss), less any dividends, accretion or reduction or redemption on the Company’s Series C Preferred Stock, by the weighted average number of common shares outstanding during the reported period. Restricted stock awards and restricted stock units (collectively, “nonvested shares”) are not considered to be outstanding shares until the service or performance vesting period has been completed. The diluted earnings per common share calculation would normally involve adjusting both the denominator and numerator as described here if the effect is dilutive. For purposes of calculating diluted earnings per common share, the denominator normally includes both the weighted-average number of shares of common stock outstanding and the number of common stock equivalents if the inclusion of such common stock equivalents is dilutive. Because a loss was incurred in each of the years ended December 31, 2022 and 2021, common stock equivalents would be anti-dilutive and, accordingly, were excluded from the calculation of diluted loss per share in each of the periods. Dilutive common stock equivalents potentially include stock options and nonvested shares using the treasury stock method and shares issuable under the employee stock purchase plan. During each of the years ended December 31, 2022 and 2021, there were no common stock equivalents. Loss per common share information was as follows (in thousands, except per share amounts) for the years ended December 31, 2022 and 2021: ​ ​ ​ ​ ​ ​ ​ ​ ​ 2022 2021 Loss per Common Share – Basic and Diluted ​ ​ Net loss for year ​ $ (186) ​ $ (469) Dividends on Series C preferred stock ​ ​ (1,275) ​ ​ (2,023) Net loss available to common shareholders ​ $ (1,461) ​ $ (2,492) ​ ​ ​ ​ ​ ​ ​ Weighted-average number of common shares outstanding ​ 74,215 ​ 74,215 ​ ​ ​ ​ ​ ​ ​ Basic and diluted loss per common share ​ $ (0.02) ​ $ (0.03) ​ At December 31, 2021, options for 25,000 shares were outstanding that have been excluded from the calculation of diluted weighted-average number of shares outstanding, as they would be anti-dilutive, since the respective options’ strike price was greater than the market price of the respective shares. There were no options outstanding at December 31, 2022.

Stock Options

Stock Options	12 Months Ended
	Dec. 31, 2022
Stock Options
Stock Options	(8) Stock Options Through the Compensation Committee of the Board, the Company administers the 2011 Stock Option and Incentive Plan (the “2011 Plan”), which provides incentive and non-qualified stock option benefits for employees, officers, directors and independent contractors providing services to Enzon. Options granted to employees generally vest over four years from date of grant and options granted to directors vest after one year. The exercise price of the options granted must be at least 100 percent of the fair value of the Company’s common stock at the time the options are granted. Options may be exercised for a period of up to ten years from the grant date. As of December 31, 2021, the 2011 Plan authorized equity-based awards for 5.0 million common shares of which approximately 4.6 million shares remained available for grant. However, this 2011 Plan and the Company’s other stock option plans, including the 2001 Incentive Stock Plan and the 1987 Non-Qualified Stock Option Plan, were terminated effective February 24, 2022 and, as such, there will be no further grants made pursuant these plans. At December 31, 2021, there were fully vested options outstanding for 25,000 shares of common stock with an average exercise price of $1.31, all of which expired in January 2022. As such, at December 31, 2022, there were no options outstanding under the 2011 Stock Option and Incentive Plan, the 2001 Incentive Stock Plan, and the 1987 Non-Qualified Stock Option Plan. As of December 31, 2022, there was no unrecognized compensation cost related to unvested options. No options were granted during the years ended December 31, 2022 and 2021. During the years ended December 31, 2022 and 2021, the Company recorded no stock-based compensation related to stock options. The Company’s policy is to use newly issued shares to satisfy the exercise of stock options. The Company received no cash from exercises of stock options during either of the years ended December 31, 2022 and 2021.

Income Taxes

Income Taxes	12 Months Ended
	Dec. 31, 2022
Income Taxes
Income Taxes	(9) Income Taxes The components of the income tax (benefit) provision are summarized as follows (in thousands): ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Year Ended December 31, ​ 2022 2021 Current: ​ ​ ​ ​ ​ ​ Federal ​ $ — ​ $ — State and foreign ​ 2 ​ 7 Total current ​ 2 ​ 7 Deferred: ​ ​ ​ Federal ​ ​ (151) ​ ​ ​ State ​ (51) ​ — Total deferred ​ ​ (202) ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Income tax (benefit) provision ​ $ (200) ​ $ 7 ​ The following table represents the reconciliation between the reported income taxes and the income taxes that would be computed by applying the federal statutory rate (21% for years ended December 31, 2022 and 2021) to income before taxes (in thousands): ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Year Ended December 31, ​ 2022 2021 Income tax provision at federal statutory rate ​ $ (81) ​ $ (97) Add (deduct) effect of: ​ ​ State income taxes, net of federal tax ​ (26) ​ (28) Expiration of federal research and development credits ​ 1,022 ​ 1,016 Change in valuation allowance ​ (1,115) ​ (884) ​ ​ ​ ​ ​ ​ ​ Income tax (benefit) provision ​ $ (200) ​ $ 7 ​ No federal income tax expense was incurred in relation to normal operating results. As of December 31, 2022 and 2021, the cumulative tax effects of temporary differences that give rise to the deferred tax assets were as follows (in thousands): ​ ​ ​ ​ ​ ​ ​ ​ ​ December 31, December 31, ​ ​ 2022 ​ 2021 Deferred tax assets: ​ ​ Federal and state net operating loss carryforward ​ $ 23,639 ​ $ 23,530 Research and development credits carryforward ​ 12,758 ​ 13,780 Total gross deferred tax assets ​ 36,397 ​ 37,310 Less valuation allowance ​ (36,195) ​ (37,310) Net deferred tax assets ​ $ 202 ​ $ — ​ ASC 740 requires the reduction of deferred tax assets by a valuation allowance if, based on the weight of available evidence, it is more likely than not that some or all of the deferred tax assets will not be realized. Because of the inherent uncertainties, including future interest rates, whether or when an acquisition of a profitable entity will come to fruition and other factors, projecting long-term future performance of the Company is problematical. Accordingly, the Company is only projecting 2023 pre-tax book income. This amounts to approximately $720,000 due to increased interest rates at the end of 2022 on its short-term cash investments. Upon review of positive and negative evidence in determining a partial reversal of the valuation allowance, the Company has concluded that a partial reversal of the valuation allowance is necessary. Interest rates may fluctuate throughout 2023. However, the Company does not expect them to return to low rates of the past creating a projected taxable income position. Therefore, the Company will partially reverse the valuation allowances as of December 31, 2022. In 2022, the Company generated approximately $389,000 in taxable loss before utilization of NOLs. The Company utilized none of the NOLs due to the taxable loss position. A deferred tax benefit of $202,000 was recorded during the year ended December 31, 2022. The Company intends to acquire profitable businesses, entities or revenue streams that will generate sufficient income so that it can utilize its approximately $103.8 million NOL. To date, no actionable acquisition candidates have been identified and, while the Company expects that, ultimately, it will be successful in realizing the value of its NOLs, the Company cannot provide assurance that it will be able to do so. Management of the Company will continue to assess the need for this valuation allowance and will make adjustments when appropriate. At December 31, 2022, the Company had federal NOLs of approximately $103.8 million, of which approximately $100.6 million will expire in the years 2025 through 2036, and New Jersey state NOLs of approximately $26.0 million that expire in the years 2031 through 2042. Under the Tax Cuts and Jobs Act, federal net operating losses generated in tax years beginning after December 31, 2017 have an unlimited carryforward period, and the amount of net operating loss allowed to be utilized each year is limited to 80% of taxable income. The Company also had federal research and development (“R&D”) credit carryforwards of approximately $1.0 million that expired in 2022. The Company has remaining R&D credit carryforwards of approximately $12.8 million that expire in the years 2023 through 2029. These deferred tax assets were subject to a valuation allowance such that the deferred tax expense incurred as a result of the expiration of the capital loss and R&D credit carryforwards was offset by a corresponding deferred tax benefit for the related reduction in valuation allowance. The Company’s ability to use the NOLs and R&D tax credit carryforwards may be limited, as they are subject to certain limitations due to ownership changes as defined by rules pursuant to Section 382 of the Internal Revenue Code of 1986, as amended. However, management of the Company believes that the Company’s NOLs will not be limited by any changes in the Company’s ownership as a result of the successful completion of the Rights Offering. (See Note 13 to the Consolidated Financial Statements.) Additionally, in an effort to protect stockholder value by attempting to protect against a possible limitation on the Company’s ability to use its NOLs, the Board adopted a Section 382 rights plan. (See Note 12 to the Consolidated Financial Statements.) The Company has not recorded a liability for unrecognized income tax benefits.

Significant Agreements

Significant Agreements	12 Months Ended
	Dec. 31, 2022
Significant Agreements
Significant Agreements	(10) Significant Agreements Merck Agreement See Note 4 to the Consolidated Financial Statements regarding Merck royalty revenues. Sesen Agreement See Note 1 to the Consolidated Financial Statements regarding the Servier milestone obligation to the Company.

Commitments and Contingent Liab

Commitments and Contingent Liabilities	12 Months Ended
	Dec. 31, 2022
Commitments and Contingent Liabilities
Commitments and Contingent Liabilities	(11) Commitments and Contingent Liabilities In December 2019, an outbreak of a novel strain of coronavirus (COVID-19) was reported in Wuhan, China. Despite continued progress in the administration of vaccines, both the continued outbreak of recent variants and the related containment measures that have been put in place across the globe, have had and are likely to continue to have a serious adverse impact on the global economy and may adversely affect the Company’s business operations. The ongoing global health crisis (including resurgences) resulting from the pandemic have disrupted, and continue to disrupt, the normal operations of many businesses, including restrictions such as the temporary scale-back of business operations and/or the imposition of either quarantine or remote work requirements for employees, either by government order or on a voluntary basis. It is impossible to predict the effect and ultimate impact of the COVID-19 pandemic, as the situation is continually evolving. The COVID-19 pandemic may continue to disrupt the global supply chain and may cause disruptions to the Company’s operations, financial condition and prospects. At the present time, the Company’s business activities have been largely unaffected by COVID-19 restrictions as the Company’s workforce is comprised solely of independent contractors who are able to perform their duties remotely. However, these restrictions may impact the third parties who are responsible for obtaining final approval of and manufacturing product candidates for which the Company shares the right to receive licensing fees, milestone payments and royalty revenues. If those third parties are required to curtail their business activities for a significant time, or if global supply chain disruptions impact their ability to procure needed resources, raw materials or components, the Company’s right to receive licensing fees, milestone payments or royalties could be materially and adversely affected. Additionally, the development timeline for product candidates being developed by third parties that are pending before the FDA or other regulatory approval could be delayed if the agency is required to shift resources to the review and approval of candidates for treatment of COVID-19. In addition, the effects of the COVID-19 pandemic may negatively impact the Company’s search for a target company, as well as the business and/or results of operations of any target business that the Company acquires or in which the Company invests. The Company has been involved in various claims and legal actions arising in the ordinary course of business. In the opinion of management, the ultimate disposition of these matters will not have a material effect on the Company’s consolidated financial position, results of operations, or liquidity.

Section 382 Rights Plan

Section 382 Rights Plan	12 Months Ended
	Dec. 31, 2022
Section 382 Rights Plan
Section 382 Rights Plan	(12) Section 382 Rights Plan On August 14, 2020, in an effort to protect stockholder value by attempting to protect against a possible limitation on the Company’s ability to use its NOLs, the Board adopted a Section 382 rights plan and declared a dividend distribution of one right for each outstanding share of the Company’s common stock to stockholders of record at the close of business on August 24, 2020. Accordingly, holders of the Company’s common stock own one preferred stock purchase right for each share of common stock owned by such holder. The rights are not immediately exercisable and will become exercisable only upon the occurrence of certain events as set forth in the Section 382 rights plan. If the rights become exercisable, each right would initially represent the right to purchase from the Company one one-thousandth of a share of the Company’s Series A-1 Junior Participating Preferred Stock, par value $0.01 per share, for a purchase price of $1.20 per right. If issued, each fractional share of Series A-1 Junior Participating Preferred Stock would give the stockholder approximately the same dividend, voting and liquidation rights as does one share of the Company’s common stock. However, prior to exercise, a right does not give its holder any rights as a stockholder of the Company, including any dividend, voting or liquidation rights. The rights will expire on the earliest of (i) the close of business on June 2, 2024 (unless that date is advanced or extended by the Board), (ii) the time at which the rights are redeemed or exchanged under the Section 382 rights plan, (iii) the close of business on the day of repeal of Section 382 of the Internal Revenue Code or any successor statute or (iv) the close of business on the first day of a taxable year of the Company to which the Company’s Board of Directors determines that no NOLs may be carried forward.

Rights Offering

Rights Offering	12 Months Ended
	Dec. 31, 2022
Rights Offering
Rights Offering	(13) Rights Offering On September 1, 2020, the Board approved a Rights Offering. For every 1,105 subscription rights held, a stockholder was entitled to purchase one Unit at the subscription price of $1,090. Each Unit consisted of one share of newly designated Series C Preferred Stock, par value $0.01 per share, and 750 shares of the Company’s common stock. On October 9, 2020, the Rights Offering expired and, as a result of the sale of all 40,000 Units, the Company received approximately $43.6 million in gross proceeds and issued shares of Series C Preferred Stock and shares of common stock such that, following the closing of the Rights Offering, there was an aggregate of 40,000 shares of Series C Preferred Stock outstanding and 74,214,603 shares of common stock outstanding. On an annual basis, the Board may, at its sole discretion, cause a dividend with respect to the Series C Preferred Stock to be paid in cash to the holders in an amount equal to 3% of the liquidation preference as in effect at such time (initially $1,000 per share). If the dividend is not so paid in cash, the liquidation preference is adjusted and increased annually by an amount equal to 5% of the liquidation preference per share as in effect at such time, that is not paid in cash to the holders on such date. Holders of Series C Preferred Stock do not have any voting rights and the Series C Preferred Stock is not convertible into shares of the Company’s common stock. The initial liquidation value of the Series C Preferred Stock was $1,000 per share. At December 31, 2021 the liquidation value of the Series C Preferred Stock was $1,062 per share,, inasmuch as no dividend was declared or paid in cash. On December 29, 2022, the Board declared a cash dividend of 3% on the Series C Preferred Stock, aggregating $1,274,400 or $31.86 per share. Accordingly, the liquidation value of the Series C Preferred Stock was $1,062 per share on December 31, 2022. The dividend was paid on January 17, 2023 to the holders of record of the Company’s Series C Preferred Stock as of January 10, 2023. As of November 1, 2022, the Company is able to redeem the Series C Preferred Stock at any time, in whole or in part, for an amount based on the liquidation preference per share as in effect at such time. Holders of Series C Preferred Stock have the right to demand that the Company redeem their shares in the event that the Company undergoes a change of control as defined in the Certificate of Designation of the Series C Preferred Stock.

Series C Preferred Stock

Series C Preferred Stock	12 Months Ended
	Dec. 31, 2022
Series C Preferred Stock
Series C Preferred Stock	(14) Series C Preferred Stock In October 2020, the Company issued 40,000 shares of Series C Preferred Stock for an aggregate purchase price of $40.0 million. As of December 31, 2021, the Board had not declared a cash dividend on the Series C Preferred Stock. Accordingly, during the year ended December 31, 2021, the Company recorded a 5% increase to the liquidation preference of approximately $50 per share of Series C Preferred Stock, aggregating approximately $2,023,000, for a cumulative liquidation value of approximately $42,483,000 ($1,062 per share) as of December 31, 2021. Because a cash dividend of 3% was declared for 2022, at December 31, 2022, there was no change to the liquidation value that was recorded as of December 31, 2021. There is no prohibition on the repurchase or redemption of Series C Preferred Shares while there is any arrearage in the payment of dividends. Since the redemption of the Series C Preferred Stock is contingently or optionally redeemable, the Series C Preferred Stock has been classified in mezzanine equity on the Consolidated Balance Sheets.

Summary of Significant Accoun_2

Summary of Significant Accounting Policies (Policies)	12 Months Ended
	Dec. 31, 2022
Summary of Significant Accounting Policies
Principles of Consolidation	Principles of Consolidation The consolidated financial statements include the accounts of Enzon Pharmaceuticals, Inc. and its wholly owned subsidiaries. All intercompany balances and transactions have been eliminated as part of the consolidation.
Use of Estimates	Use of Estimates The preparation of consolidated financial statements in conformity with accounting principles generally accepted in the United States of America (“U.S. GAAP”) requires management to make estimates and assumptions that affect reported amounts of assets and liabilities, disclosures of contingent assets and liabilities at the date of the financial statements, and the reported amounts of revenues and expenses during the reporting period. These estimates include legal and contractual contingencies and income taxes. Although management bases its estimates on historical experience, relevant current information and various other assumptions that are believed to be reasonable under the circumstances, actual results could differ from these estimates.
Financial Instruments and Fair Value	Financial Instruments and Fair Value The carrying values of cash and cash equivalents, royalty receivable, other current assets, accounts payable, accrued expenses and other current liabilities in the Company’s consolidated balance sheets approximated their fair values at December 31, 2022 and 2021 due to their short-term nature. As of each of December 31, 2022 and 2021, the Company held cash equivalents aggregating approximately $44.2 million and $43.6 million, respectively.
Revenue Recognition	Revenue Recognition Royalty revenues from the Company’s agreements with third parties and pursuant to the sale of the Company’s former specialty pharmaceutical business are recognized when the Company can reasonably determine the amounts earned. In most cases, this will be upon notification from the third-party licensee, which is typically during the quarter following the quarter in which the sales occurred. The Company does not participate in the selling or marketing of products for which it receives royalties. Because the Company records revenue only when collection is assured, no provision for uncollectible accounts is established upon recognition of revenues. Contingent payments with third parties and pursuant to the sale of the Company’s former specialty pharmaceutical business are recognized as income when the milestone has been achieved and collection is assured, such payments are non-refundable and no further effort is required on the part of the Company or the other party to complete the earning process.
Income Taxes	Income Taxes Income taxes are accounted for under the asset and liability method. Deferred tax assets and liabilities are recognized for the estimated future tax consequences attributable to differences between the financial statement carrying amounts of existing assets and liabilities and their respective tax bases and operating loss and tax credit carryforwards. Deferred tax assets and liabilities are measured using enacted tax rates expected to apply to taxable income in the years in which those temporary differences are expected to be realized. The effect of a change in tax rates or laws on deferred tax assets and liabilities is recognized in operations in the period that includes the enactment date of the rate change. A valuation allowance is established to reduce the deferred tax assets to the amounts that are more likely than not to be realized from operations. Tax benefits of uncertain tax positions are recognized only if it is more likely than not that the Company will be able to sustain a position taken on an income tax return. The Company has no liability for uncertain tax positions. Interest and penalties, if any, related to unrecognized tax benefits would be recognized as income tax expense.

Accounts Payable, Accrued Exp_2

Accounts Payable, Accrued Expenses and Dividends Payable on Series C Preferred Stock (Tables)	12 Months Ended
	Dec. 31, 2022
Accounts Payable, Accrued Expenses and Dividends Payable on Series C Preferred Stock
Schedule of accrued expenses and other current liabilities	Accrued expenses and other current liabilities consisted of the following as of December 31, 2022 and 2021 (in thousands): ​ ​ ​ ​ ​ ​ ​ ​ ​ December 31, December 31, ​ ​ 2022 ​ 2021 Professional and consulting fees ​ $ 87 ​ $ 61 Other ​ 6 ​ 11 ​ ​ $ 93 ​ $ 72 ​

Loss Per Common Share (Tables)

Loss Per Common Share (Tables)	12 Months Ended
	Dec. 31, 2022
Loss Per Common Share
Schedule of Loss per common share information, basic and diluted	Loss per common share information was as follows (in thousands, except per share amounts) for the years ended December 31, 2022 and 2021: ​ ​ ​ ​ ​ ​ ​ ​ ​ 2022 2021 Loss per Common Share – Basic and Diluted ​ ​ Net loss for year ​ $ (186) ​ $ (469) Dividends on Series C preferred stock ​ ​ (1,275) ​ ​ (2,023) Net loss available to common shareholders ​ $ (1,461) ​ $ (2,492) ​ ​ ​ ​ ​ ​ ​ Weighted-average number of common shares outstanding ​ 74,215 ​ 74,215 ​ ​ ​ ​ ​ ​ ​ Basic and diluted loss per common share ​ $ (0.02) ​ $ (0.03) ​

Income Taxes (Tables)

Income Taxes (Tables)	12 Months Ended
	Dec. 31, 2022
Income Taxes
Schedule of Components of Income Tax Expense (Benefit)	The components of the income tax (benefit) provision are summarized as follows (in thousands): ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Year Ended December 31, ​ 2022 2021 Current: ​ ​ ​ ​ ​ ​ Federal ​ $ — ​ $ — State and foreign ​ 2 ​ 7 Total current ​ 2 ​ 7 Deferred: ​ ​ ​ Federal ​ ​ (151) ​ ​ ​ State ​ (51) ​ — Total deferred ​ ​ (202) ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Income tax (benefit) provision ​ $ (200) ​ $ 7 ​
Schedule of Effective Income Tax Rate Reconciliation	The following table represents the reconciliation between the reported income taxes and the income taxes that would be computed by applying the federal statutory rate (21% for years ended December 31, 2022 and 2021) to income before taxes (in thousands): ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Year Ended December 31, ​ 2022 2021 Income tax provision at federal statutory rate ​ $ (81) ​ $ (97) Add (deduct) effect of: ​ ​ State income taxes, net of federal tax ​ (26) ​ (28) Expiration of federal research and development credits ​ 1,022 ​ 1,016 Change in valuation allowance ​ (1,115) ​ (884) ​ ​ ​ ​ ​ ​ ​ Income tax (benefit) provision ​ $ (200) ​ $ 7 ​
Schedule of Deferred Tax Assets and Liabilities	As of December 31, 2022 and 2021, the cumulative tax effects of temporary differences that give rise to the deferred tax assets were as follows (in thousands): ​ ​ ​ ​ ​ ​ ​ ​ ​ December 31, December 31, ​ ​ 2022 ​ 2021 Deferred tax assets: ​ ​ Federal and state net operating loss carryforward ​ $ 23,639 ​ $ 23,530 Research and development credits carryforward ​ 12,758 ​ 13,780 Total gross deferred tax assets ​ 36,397 ​ 37,310 Less valuation allowance ​ (36,195) ​ (37,310) Net deferred tax assets ​ $ 202 ​ $ — ​

Description of Business (Detail

Description of Business (Details)				3 Months Ended				12 Months Ended
	Dec. 29, 2022 USD ($) $ / shares	Sep. 30, 2020 USD ($) $ / shares shares	Sep. 01, 2020 $ / shares shares	Dec. 31, 2022 USD ($) $ / shares shares	Dec. 31, 2021 USD ($) $ / shares shares	Jun. 30, 2021 USD ($)	Mar. 31, 2021 USD ($)	Dec. 31, 2022 USD ($) $ / shares shares	Sep. 23, 2020 $ / shares
Description of Business
Amount of operating loss carry forward | $		$ 100,000,000		$ 103,800,000				$ 103,800,000
Milestone revenue | $							$ 409,430,000
Amount received | $						$ 292,284,000
license maintenance fee | $				$ 26,000,000	$ 28,000,000
Royalty receivable | $					$ 28,000
Common stock, shares outstanding | shares				74,214,603	74,214,603			74,214,603
Rights Offering
Description of Business
Rights offering and realized in gross proceeds | $		$ 43,600,000
Subscription price per Unit									$ 1,090
Number of rights per share of stock | shares		1	1
Number of subscription rights to be held		1,105
Preferred stock, par value		$ 1
Number of units available for purchase | shares		40,000
Rights Offering | Common Stock
Description of Business
Number of Shares Per Unit | $		750
Common stock, shares outstanding | shares				74,214,603				74,214,603
Series C Preferred Stock
Description of Business
Preferred stock, par value				$ 0.01	$ 0.01			$ 0.01
Preferred stock, shares outstanding | shares				40,000	40,000			40,000
Percentage of dividend on liquidation preference to be paid in cash								3%
Percentage of annual increase in liquidation preference								5%
Preferred stock, liquidation value (per share)				$ 1,062	$ 1,062			$ 1,062
Initial dividend per share								$ 1,000
Cash dividend (as percent)	3%
Aggregated dividend amount | $	$ 1,274,400							$ 1,274,400
Dividend per share	$ 31.86							$ 31.86
Cumulative liquidation value | $	$ 42,483,286			$ 42,483,000	$ 2,023,000			$ 42,483,000
Cumulative liquidation value per share				$ 1,062	$ 1,062			$ 1,062
Series C Preferred Stock | Rights Offering
Description of Business
Preferred stock, par value		$ 0.01
Percentage of dividend on liquidation preference to be paid in cash			3%
Cumulative liquidation value per share			$ 1,000		$ 1,062

Summary of Significant Accoun_3

Summary of Significant Accounting Policies (Details) - USD ($) $ in Millions	Dec. 31, 2022	Dec. 31, 2021
Summary of Significant Accounting Policies
Cash equivalents	$ 44.2	$ 43.6

Accounts Payable, Accrued Exp_3

Accounts Payable, Accrued Expenses and Dividends Payable on Series C Preferred Stock (Details) - USD ($) $ in Thousands	Dec. 31, 2022	Dec. 31, 2021
Accounts Payable, Accrued Expenses and Dividends Payable on Series C Preferred Stock
Professional and consulting fees	$ 87	$ 61
Other	6	11
Accrued expenses and other current liabilities, Total	$ 93	$ 72

Accounts Payable, Accrued Exp_4

Accounts Payable, Accrued Expenses and Dividends Payable on Series C Preferred Stock - Additional Information (Details) - USD ($)		12 Months Ended
	Dec. 29, 2022	Dec. 31, 2022	Dec. 31, 2021
Accounts Payable, Accrued Expenses and Dividends Payable on Series C Preferred Stock
Revenues		$ 26,000	$ 701,000
Series C Preferred Stock
Accounts Payable, Accrued Expenses and Dividends Payable on Series C Preferred Stock
Cash dividend (as percent)	3%
Cumulative liquidation value	$ (42,483,286)	(42,483,000)	(2,023,000)
Aggregated dividend amount	$ 1,274,400	$ 1,274,400
Dividend per share	$ 31.86	$ 31.86
Royalty
Accounts Payable, Accrued Expenses and Dividends Payable on Series C Preferred Stock
Revenues			28,000
Merck
Accounts Payable, Accrued Expenses and Dividends Payable on Series C Preferred Stock
Due to related parties			$ 331,000
Accrued royalties		$ 331,000

Stockholders' Equity (Details)

Stockholders' Equity (Details) - shares	Dec. 31, 2022	Dec. 31, 2021
Stockholders' Equity
Preferred stock, shares authorized	2,960,000	2,960,000
Non-qualified and incentive stock plans
Stockholders' Equity
Common stock reserved	9,818,392
Series A-1 Junior Participating Preferred Stock
Stockholders' Equity
Preferred stock, shares authorized	100,000
Series C Preferred Stock
Stockholders' Equity
Preferred stock, shares authorized		3,000,000
Preferred stock, shares issued	40,000	40,000
Preferred stock, shares outstanding	40,000	40,000

Cash Dividend (Details)

Cash Dividend (Details) - USD ($)		12 Months Ended
	Dec. 29, 2022	Dec. 31, 2022	Dec. 31, 2021
Cash Dividend
Common stock dividend paid or declared		$ 0	$ 0
Series C Preferred Stock
Cash Dividend
Cash dividend (as percent)	3%
Aggregated dividend amount	$ 1,274,400	$ 1,274,400
Dividend per share	$ 31.86	$ 31.86
Cumulative liquidation value	$ 42,483,286	$ 42,483,000	$ 2,023,000
Cumulative liquidation value per share		$ 1,062	$ 1,062

Loss Per Common Share (Details)

Loss Per Common Share (Details) - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021
Loss per Common Share - Basic and Diluted
Net loss for year	$ (186)	$ (469)
Dividends on Series C preferred stock	(1,275)	(2,023)
Net loss available to common shareholders	$ (1,461)	$ (2,492)
Weighted-average number of common shares outstanding - Basic	74,215	74,215
Weighted-average number of common shares outstanding - Diluted	74,215	74,215
Basic loss per common share	$ (0.02)	$ (0.03)
Loss per common share - Diluted	$ (0.02)	$ (0.03)

Loss Per Common Share - Additio

Loss Per Common Share - Additional Information (Details) - shares	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2022
Loss Per Common Share
Antidilutive securities	25,000
Option outstanding		0

Stock Options (Details)

Stock Options (Details) - USD ($)	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021
Stock Options
Exercise price as percentage of fair value	100%
Expiration period	10 years
Outstanding shares expired	0	25,000
Average exercise price of outstanding options expired		$ 1.31
Unrecognized compensation cost	$ 0
Options granted during the period	0	0
Stock-based compensation expense	$ 0	$ 0
Proceeds from Stock Options Exercised	$ 0	$ 0
2011 Plan
Stock Options
Number of shares authorized		5,000,000
Number of shares available for grant		4,600,000
Employee
Stock Options
Vesting period	4 years
Director
Stock Options
Vesting period	1 year

Income Taxes - Provision compon

Income Taxes - Provision components (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021
Current:
State and foreign	$ 2	$ 7
Total current	2	7
Deferred:
Federal	(151)
State	(51)
Total deferred	(202)
Income tax (benefit) provision	$ (200)	$ 7

Income Taxes - Rate reconciliat

Income Taxes - Rate reconciliation (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021
Income Taxes
Income tax provision at federal statutory rate	$ (81)	$ (97)
Add (deduct) effect of:
State income taxes, net of federal tax	(26)	(28)
Expiration of federal research and development credits	1,022	1,016
Change in valuation allowance	(1,115)	(884)
Income tax (benefit) provision	$ (200)	$ 7

Income Taxes - Deferred tax ass

Income Taxes - Deferred tax assets (Details) - USD ($) $ in Thousands	Dec. 31, 2022	Dec. 31, 2021
Deferred tax assets:
Federal and state net operating loss carryforward	$ 23,639	$ 23,530
Research and development credits carryforward	12,758	13,780
Total gross deferred tax assets	36,397	37,310
Less valuation allowance	(36,195)	$ (37,310)
Net deferred tax assets	$ 202

Income Taxes - Additional infor

Income Taxes - Additional information (Details) - USD ($)	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021	Sep. 30, 2020
Income Taxes
Effective Income Tax Rate Reconciliation, at Federal Statutory Income Tax Rate		21%	21%
Pre-tax book income		$ (386,000)	$ (462,000)
Net Operating Loss Carry-Forwards Limitation On Annual Utilization		389,000
Deferred income taxes		202,000
Operating loss carryforwards		$ 103,800,000		$ 100,000,000
Tax credit carryforward, limitations on use		net operating losses generated in tax years beginning after December 31, 2017 have an unlimited carryforward period, and the amount of net operating loss allowed to be utilized each year is limited to 80% of taxable income
Forecast
Income Taxes
Pre-tax book income	$ 720,000
R & D credit carryforwards
Income Taxes
Tax credit carryforward, limitations on use		The Company has remaining R&D credit carryforwards of approximately $12.8 million that expire in the years 2023 through 2029
Domestic Tax Authority
Income Taxes
Operating loss carryforwards		$ 100,600,000
Domestic Tax Authority | R & D credit carryforwards
Income Taxes
Tax Credit Carryforward Amount		1,000,000
New Jersey state
Income Taxes
Operating loss carryforwards		$ 26,000,000

Section 382 Rights Plan (Detail

Section 382 Rights Plan (Details)	Aug. 14, 2020 Vote $ / shares shares	Dec. 31, 2022 $ / shares	Dec. 31, 2021 $ / shares
Preferred stock, par value (in dollars per share) | $ / shares		$ 0.01	$ 0.01
Section 382 Rights Plan
Rights per share distributed as dividend | shares	1
Number of preferred stock purchase right for each common stockholder | shares	1
Section 382 Rights Plan | Series A-1 Junior Participating Preferred Stock
Number of common stock eligible for each warrant become exercisable | shares	1
Preferred stock, par value (in dollars per share) | $ / shares	$ 0.01
Purchase price per right | $ / shares	$ 1.20
Number of votes for fractional share | Vote	1

Rights Offering (Details)

Rights Offering (Details) - USD ($)				12 Months Ended
	Dec. 29, 2022	Oct. 09, 2020	Sep. 01, 2020	Dec. 31, 2022	Dec. 31, 2021	Sep. 30, 2020
Rights Offering
Preferred stock, par value (in dollars per share)				$ 0.01	$ 0.01
Preferred Stock, Shares Outstanding				0	0
Common stock, shares outstanding				74,214,603	74,214,603
Series C Preferred Stock
Rights Offering
Percentage of dividend on liquidation preference to be paid in cash				3%
Cumulative liquidation value per share				$ 1,062	$ 1,062
Cash dividend (as percent)	3%
Aggregated dividend amount	$ 1,274,400			$ 1,274,400
Dividend per share	$ 31.86			$ 31.86
Rights Offering
Rights Offering
Number of subscription rights to be held for purchase of a unit			1,105
Number of units entitled for 1,105 subscription rights held			1
Subscription price per unit of a right			$ 1,090
Number of common stock eligible for each warrant become exercisable			1			1
Rights Offering | Series C Preferred Stock
Rights Offering
Preferred stock, par value (in dollars per share)			$ 0.01
Number of common shares for unit			750
Percentage of dividend on liquidation preference to be paid in cash			3%
Cumulative liquidation value per share			$ 1,000		$ 1,062
Annual Increase in Percentage of the Liquidation Preference Per Share, If Dividend Not Paid in Cash			5%
Rights Offering | Investment Agreement | Icahn Capital LP
Rights Offering
Number of units sold		40,000
Issued and gross proceeds		$ 43,600,000
Rights Offering | Investment Agreement | Icahn Capital LP | Series C Preferred Stock
Rights Offering
Preferred Stock, Shares Outstanding		40,000
Common stock, shares outstanding		74,214,603

Series C Preferred Stock (Detai

Series C Preferred Stock (Details) - Series C Preferred Stock - USD ($)	1 Months Ended	12 Months Ended
	Oct. 31, 2020	Dec. 31, 2022	Dec. 31, 2021	Dec. 29, 2022
Series C Preferred Stock
Rights offering, proceeds (in shares)	40,000
Rights offering, proceeds net of expenses	$ 40,000,000
Increase in liquidation preference value (in percentage)			5%
Preferred stock, increase in liquidation preference (per share)			$ 50
Cumulative liquidation value		$ 42,483,000	$ 2,023,000	$ 42,483,286
Preferred stock cumulative liquidation value			$ 42,483,000
Cumulative liquidation value per share		$ 1,062	$ 1,062
Preferred Stock, Liquidation Preference Percent		3%