Exhibit 3.5

INDEPENDENT CONTRACTOR AGREEMENT

This Independent Contractor Agreement (the “Agreement”) is effective as of February 24, 2022 (the “Effective Date”) by and between Richard L. Feinstein, CPA (“Feinstein”) and Enzon Pharmaceuticals, Inc. (“Enzon”), pursuant to which Feinstein is being engaged to serve as Enzon’s Chief Executive Officer, Chief Financial Officer and Secretary. This Agreement supersedes and replaces in its entirety the Independent Contractor Agreement between the Feinstein and Enzon dated as of December 13, 2013.

RECITALS

WHEREAS, Enzon desires to continue to retain the services of Feinstein, and Feinstein desires to provide such services to Enzon, subject to the terms and conditions contained herein.

NOW, THEREFORE, in consideration of the mutual covenants and agreements contained herein, the receipt and sufficiency of which are hereby acknowledged, the parties hereto agree as follows:

1. Feinstein’s Position and Duties; Term.

A.Feinstein is hereby engaged by Enzon as an independent contractor to serve as the Chief Executive Officer, Chief Financial Officer and Secretary of Enzon and Feinstein shall perform such services as are customarily associated with his positions and such additional services consistent with his positions as may, from time to time, be properly and lawfully assigned to him by the Board of Directors (the “Services”). Without derogating from the foregoing, Feinstein will work at the request of Enzon as and when requested by Enzon or its Board of Directors.

B.The term of this Agreement (the “Term”) shall commence on the Effective Date and continue until terminated by either party with or without cause upon receipt of written notice.

2. Independent Contractor Relationship.

A. The relationship between Enzon and Feinstein shall be that of independent contracting parties and shall not be deemed to be any other relationship, including, without limitation, that of principal and agent. Nothing herein shall be construed to create the relationship of employer and employee between Enzon and Feinstein. Feinstein shall exercise his own independent judgment as to the method and manner of performance of the Services hereunder. Enzon does not seek, and shall not expect, any control over Feinstein’s performance of the Services; provided, however, Feinstein shall conform to such policies and procedures established by Enzon and to such customary standards which are necessary to satisfy applicable statutes, rules or regulations governing the provision of such Services. Enzon shall not be obligated to provide any employee-related benefit to Feinstein, including, but not limited to, Workers Compensation insurance, unemployment insurance, disability insurance, health or accident insurance, nor will Enzon make any contributions for Social Security, or withholding taxes on behalf of Enzon. Feinstein acknowledges that Enzon will not provide any benefits or participation in any benefit plan applicable to an employer-employee relationship. Feinstein shall be solely responsible for the payment of all applicable governmental taxes, including federal, state and local taxes, and Social Security contributions.

B.Feinstein is free to devote whatever time he chooses to any other business in which he may choose to engage, provided he complies with all applicable regulatory rules. Feinstein may determine his own hours of work and may perform the Services in any manner or sequence he determines, subject, however, to such restrictions as may exist in order to comply with the policies of Enzon or to satisfy the requirements or standards of the statutes, rules or regulations governing the Services.

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C.Feinstein has not received any training from Enzon and Enzon will not provide any training to Feinstein.

D.Feinstein shall not have the authority to hire, direct and pay other persons in connection with the Services without the prior written consent of Enzon. Any person so employed by Feinstein shall be the employee of Feinstein and shall not be the employee or agent of Enzon.

3.Compliance With Statutes, Rules And Regulations.

As part of the proper performance of the Services, at all times during the Term, Feinstein shall comply with all applicable statutes, regulations, rules and written statements of policy promulgated and administered by the Securities and Exchange Commission and any state or municipal governmental or regulatory agency; and the rules of any national securities exchange or association in which Enzon is or may become a member.

4.Fees.

A.During the Term, Enzon shall pay Feinstein’s fees at an annualized amount of $200,000 (the “Fees”) (in bi-weekly installments in the amount of $7,671.23) in connection with the Services. Feinstein shall perform the Services at such times and as requested by Enzon.

B.For each fiscal year in the Term, Feinstein shall be eligible to earn up to an additional 25% of the Fees based on his performance and that of Enzon, at the discretion of the Board of Directors.

C.Enzon will reimburse Feinstein for reasonable out-of-pocket expenses incurred by Feinstein in connection with the performance of the Services during the Term, including: (i) mileage at the rate of fifty (50) cents per mile for any driving that may be required in connection with Feinstein’s performance of the Services; (ii) tolls; (iii) supplies; and (iv) other reasonable expenses incurred by Feinstein in connection with the performance of the Services. Feinstein will submit receipts or documentation of expenses during the Term and Enzon will pay each such proper bill within twelve (12) business days of its receipt.

5. Warranties.

A.Each party warrants to the other that it has the authority to enter into and perform this agreement, and its performance hereunder will not result in the breach or violation of any contract, arrangement or understanding it may have with any third party. Each party warrants to the other that it will comply in all material respects with all applicable laws, rules and regulations.

B.Consultant shall perform the services in accordance with the highest professional standards and in compliance with all applicable laws and regulations.

6. Indemnification. Feinstein shall be entitled to the same indemnification rights from Enzon under the bylaws of Enzon as are applicable to all other directors and officers of Enzon and covered by the same Directors and Officers Insurance as all other officers and directors of Enzon.

7. Confidentiality.

A.Feinstein acknowledges and agrees that during the Term, he will have access to “Confidential Information” concerning Enzon, its affiliates, and their clients and employees, and that such Confidential Information constitutes a valuable and unique asset of Enzon. For purposes of this Agreement, Confidential Information includes, but is not limited to, proprietary information pertaining to Enzon, its affiliates and clients, including business plans (both current and under development), data, trade secrets, financial information, costs, revenues, profits, methodologies, information concerning clients and potential clients, compilations, systems, technologies, computer programs, potential acquisition targets and all other information which Enzon and its clients treat as confidential. All Confidential Information obtained by Feinstein in the course

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of providing the Services shall be deemed confidential and proprietary. Feinstein covenants and agrees that, during the Term and at all times thereafter, Feinstein will not, except as may be required by applicable law, regulation, legal process, or the request of any regulatory or self-regulatory authority, (i) for any reason use for Feinstein’s own benefit or the benefit of any person or entity with which Feinstein may be associated, or disclose any Confidential Information to any person or entity, for any reason or purpose, without the prior written consent of Enzon; or (ii) remove or cause to be removed from Enzon’s office any Confidential Information or material relating thereto for purposes other than those for use in connection with Feinstein’s Services. Upon the expiration of the Term (including any renewal thereof), Feinstein agrees to return to Enzon all tangible embodiments of all Confidential Information in Feinstein’s possession or control, nor will Feinstein retain any copy or records of such Confidential Information, in hard copy or electronic form.

B.Nothing in this Agreement prohibits Feinstein from reporting any possible violations of federal law or regulation to any government agency or entity, including but not limited to the Department of Justice and the Securities and Exchange Commission, or making any other disclosures that are protected under the whistleblower provisions of Federal law or regulation. Feinstein is not required to notify Enzon that he will make or has made such reports or disclosures. Non-compliance with the disclosure provisions of this Agreement shall not subject Feinstein to criminal or civil liability under any Federal or State trade secret law for the disclosure of an Enzon trade secret if the disclosure is made: (i) in confidence to a Federal, State or local government official, either directly or indirectly, or to an attorney in confidence solely for the purpose of reporting or investigating a suspected violation of law; (ii) in a complaint or other document filed in a lawsuit or other proceeding, provided that any complaint or document containing the trade secret is filed under seal; or (iii) to an attorney representing Feinstein in a lawsuit for retaliation by Enzon for reporting a suspected violation of law or to use the trade secret information in that court proceeding, provided that any document containing the trade secret is filed under seal and Feinstein does not disclose the trade secret, except pursuant to court order.

8. Miscellaneous.

A.This Agreement shall in all respects be governed by, and construed and enforced in accordance with the laws of, the State of New Jersey, without giving effect to its conflicts of laws provisions.

B.This Agreement shall be binding upon and shall inure to the benefit of the parties hereto and their permitted successors and assigns. This Agreement may not be assigned by Feinstein without the prior written consent of Enzon.

C.This Agreement is not a contract of employment or service for any specific or minimum term and the arrangement set forth above is terminable at will. Feinstein may resign his employment or service, and Enzon likewise may terminate his employment or service, at any time, for any reason, with or without cause or advance notice and without any liability on the part of Enzon for severance.

D.The terms of this Agreement cannot be modified, altered or changed, except in a writing signed by both parties. From and after the Effective Date, this Agreement constitutes the entire agreement between the parties hereto, and supersedes all prior representations, agreements and understandings, both written and oral, relating to any services rendered by Feinstein to Enzon or any of its affiliates, including, without limitation, the Independent Contractor Agreement between the Feinstein and Enzon dated as of December 13, 2013, which agreement shall be considered null and void as of the Effective Date without any further action or notice.

C.Any notice provided for in this Agreement shall be in writing and shall be either personally delivered, sent by electronic mail, or sent by reputable overnight carrier, in each case with proof of receipt, to the recipient. Notices to Feinstein shall be sent to the address that he most recently provided to Enzon. Notices to Enzon should be sent to Enzon Pharmaceuticals, Inc., P.O. Box 570005, Houston, Texas, 77257, Attn:  Chairman of the Board, Email RCRead@icmgi.com, with a copy to Todd E. Mason, 335 Madison Avenue 12th Floor, New York, New York, 10017, Email Todd.Mason@ThompsonHine.com. Any notice under this Agreement will be deemed to have been given when so delivered, sent or emailed.

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(Signature page follows)

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IN WITNESS WHEREOF, the parties have executed this Agreement as of the Effective Date.

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Exhibit 4.1

DESCRIPTION OF ENZON PHARMACEUTICALS, INC.’S REGISTERED SECURITIES

The following description of the common stock, $0.01 par value (“Common Stock”), of Enzon Pharmaceuticals, Inc. (“us”, “our”, or the “Company”) and the Series A-1 Junior Participating Preferred Stock Purchase Rights (the “Rights”) is a summary. This summary is not complete and is subject to and qualified in its entirety by reference to the complete text of our Amended and Restated Certificate of Incorporation, as amended (“Certificate”), and our Second Amended and Restated By-Laws, as amended (“By-Laws”), each previously filed with the Securities and Exchange Commission and incorporated by reference as an exhibit to the Annual Report on Form 10-K of which this Exhibit 4.1 is a part, as well as to the relevant provisions of the Delaware General Corporation Law (the “DGCL”). The Common Stock and the Rights are the only classes of securities of the Company registered under Section 12 of the Securities Exchange Act of 1934, as amended.

General

The authorized capital stock of the Company consists of: (i) 170,000,000 shares of Common Stock, and (ii) 3,000,000 shares of preferred stock, par value $0.01 per share (“Preferred Stock”).

Common Stock

Dividends

Holders of Common Stock are entitled to receive dividends when, as and if declared by our Board of Directors out of funds legally available for their payment, subject to the rights of holders of any Preferred Stock that may be issued and outstanding and to restrictions contained in agreements to which the Company is a party.

Voting Rights

Each holder of our Common Stock is entitled to one vote per share on all matters submitted to a vote of stockholders. Generally, a matter submitted for stockholder action shall be approved if a majority of the votes cast at such meeting by the holders of shares of Common Stock present in person or represented by proxy and entitled to vote thereon are cast “for” the matter, unless a greater or different vote is required by statute, any applicable law or regulation, the rights of any authorized series of Preferred Stock, or our Certificate or By-Laws. Other than in a contested election where directors are elected by a plurality vote, a director nominee shall be elected to the board if the votes cast “for” such nominee’s election exceed the votes cast “against” such nominee’s election. Subject to any rights of the holders of any series of Preferred Stock pursuant to applicable law or the certificate of designations creating that series, all voting rights are vested in the holders of shares of our Common Stock. Holders of shares of our Common Stock do not have cumulative voting rights.

Rights Upon Liquidation

Upon our liquidation, dissolution or winding up, the holders of Common Stock are entitled to share ratably in our net assets available after the payment of all debts and other liabilities, and after the satisfaction of the rights of any outstanding Preferred Stock.

Other Rights

Holders of our Common Stock have no preemptive, subscription, redemption or conversion rights, nor are they entitled to the benefit of any sinking fund. The outstanding shares of Common Stock are validly issued, fully paid and non-assessable.

Preferred Stock

Our Board of Directors is authorized, without further action by our stockholders, to issue up to 3,000,000 shares of “blank check” Preferred Stock, in one or more series, and to fix the designations, powers, preferences and the relative, participating, optional or other special rights and any qualifications, limitations and restrictions of the shares of each series of Preferred Stock. The issuance of Preferred Stock could have the effect of delaying, deferring or preventing a change in control, as well as decrease the amount of earnings and assets available for distribution to holders of our Common Stock or otherwise adversely affect their rights and powers, including voting rights. Of our currently authorized Preferred Stock, 100,000 shares are designated as Series A-1 Junior Participating Preferred Stock in connection with the Company’s Section 382 Rights Plan (as defined below), which was adopted August 14, 2020, and 40,000 shares are designated as Series C Non-Convertible Redeemable Preferred Stock, which were issued in connection with a rights offering completed by the Company during October 2020.

Series A-1 Junior Participating Preferred Stock Purchase Rights

On August 14, 2020 (the “Rights Dividend Declaration Date”), the Board of Directors (the “Board”) of the Company adopted a Section 382 rights plan (the “Section 382 Rights Plan”) and declared a dividend distribution of one Right for each outstanding share of Common Stock to stockholders of record at the close of business on August 24, 2020. Each Right entitles its holder, under certain circumstances described below, to purchase from the Company one one-thousandth of a share of Series A-1 Junior Participating Preferred Stock of the Company, par value $0.01 per share (the “Series A-1 Junior Participating Preferred Stock”), at an exercise price of $1.20 per Right, subject to adjustment (the “Purchase Price”). The description and terms of the Rights are set forth in a Section 382 Rights Agreement, dated as of August 14, 2020, as amended on June 4, 2021 (with effect as of June 2, 2021) by and between the Company and Continental Stock Transfer & Trust Company, as Rights Agent (the “Section 382 Rights Agreement”).

The Board adopted the Section 382 Rights Plan in an effort to protect stockholder value by attempting to protect against a possible limitation on the Company’s ability to use its net operating loss carryforwards (“NOLs”). If the Company experiences an “ownership change,” as defined in Section 382 of the Internal Revenue Code of 1986, as amended (the “Code”), the Company’s ability to fully utilize the NOLs on an annual basis will be substantially limited, and the timing of the usage of the NOLs could be substantially delayed, which could therefore significantly impair the value of those benefits. The Section 382 Rights Plan is intended to act as a deterrent to any person (an “Acquiring Person”) acquiring (together with all affiliates and associates of such person) beneficial ownership of 4.9% or more of the Company’s outstanding common stock within the meaning of Section 382 of the Code, without the approval of the Board. Stockholders who beneficially own 4.9% or more of the Company’s outstanding common stock as of the Rights Dividend Declaration Date will not be deemed to be an Acquiring Person.

The Rights

Initially, the Rights are associated with shares of Common Stock certificates or, in the case of uncertificated shares of Common Stock, the book-entry account that evidences record ownership of such shares, which will contain a notation incorporating the Section 382 Rights Plan by reference, and are transferable with and only with the underlying shares of Common Stock. New Rights will attach to any shares of Common Stock that become outstanding after the Record Date and prior to the earlier of the Distribution Date (as defined below) and the Expiration Date (as defined below). If Series A-1 Junior Participating Preferred Stock is issued upon exercise of the Rights, 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 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.

Initial Exercisability

Subject to certain exceptions, the Rights are not exercisable until the “Distribution Date,” which occurs upon the earlier of:

Any existing stockholder or group that beneficially owned 4.9% or more of Common Stock as of August 14, 2020 has been grandfathered at its current ownership level, but the Rights will not be exercisable if, at any time after the announcement of the Section 382 Rights Plan, such stockholder or group increases its ownership of Common Stock by one share of Common Stock. Certain synthetic interests in securities created by derivative positions, whether or not such interests are considered to be ownership of the underlying Common Stock or are reportable for purposes of Regulation 13D of the Securities Exchange Act of 1934, as amended, are treated as beneficial ownership of the number of shares of Common Stock equivalent to the economic exposure created by the derivative position, to the extent actual shares of Common Stock are directly or indirectly held by counterparties to the derivatives contracts.

Separation and Distribution of Rights

Until the earlier of the Distribution Date and the Expiration Date, the surrender for transfer of any shares of Common Stock will also constitute the transfer of the Rights associated with those shares. As soon as practicable after the Distribution Date, separate rights certificates will be mailed to holders of record of Common Stock as of the close of business on the Distribution Date. From and after the Distribution Date, the separate rights certificates alone will represent the Rights, and the Rights may be transferred apart from the transfer of the underlying shares of Common Stock, unless and until the Board has determined to effect an exchange pursuant to the Section 382 Rights Agreement (as described below).

Expiration Date

The Section 382 Rights Agreement will expire on the earliest of the following:

“Flip-In” Event

In the event that a person becomes an Acquiring Person (a “Flip-in Event”), each holder of a Right, other than Rights that are or, under certain circumstances, were beneficially owned by the Acquiring Person (which will thereupon become void), will, from and after the Distribution Date, have the right to receive, upon exercise of a Right and payment of the Purchase Price, a number of shares of Common Stock having a market value of two times the Purchase Price.

For example, at an exercise price of $1.20 per Right, each Right not owned by an Acquiring Person (or certain related parties) following a Flip-in Event will entitle its holder to purchase $2.40 worth of shares of Common Stock for $1.20. If the Common Stock at the time of exercise had a market value per share of $0.20, the holder of each valid Right would be entitled to purchase twelve shares of Common Stock for $1.20.

However, Rights are not exercisable following the occurrence of a person becoming an Acquiring Person until such time as the Rights are no longer redeemable by the Company (as described below).

“Flip-Over” Event

In the event that, at any time following the Stock Acquisition Date, any of the following occurs (each, a “Flip-over Event”):

each holder of a Right (except Rights which previously have been voided as described above) will have the right to receive, upon exercise, common stock of the acquiring company having a value equal to two times the exercise price of the Right.

Preferred Share Provisions

Each share of Series A-1 Junior Participating Preferred Stock, if issued: will not be redeemable, will entitle the holder thereof, when, as and if declared, to quarterly dividend payments equal to the greater of $1.20 per share and 1,000 times the amount of all cash dividends plus 1,000 times the amount of non-cash dividends or other distributions paid on one share of Common Stock, will entitle the holder thereof to receive $1,200 plus accrued and unpaid dividends per share upon liquidation, will have the same voting power as 1,000 shares of Common Stock and, if shares of Common Stock are exchanged via merger, consolidation or a similar transaction, will entitle the holder thereof to a per share payment equal to the payment made on 1,000 shares of Common Stock.

Exempted Persons and Exempted Transactions

The Board recognizes that there may be instances when an acquisition of shares of Common Stock that would cause a stockholder to become an Acquiring Person may not jeopardize or endanger in any material respect the availability of the NOLs to the Company. Accordingly, the Section 382 Rights Agreement provides that the following “Exempted Persons” cannot become an Acquiring Person:

Additionally, the Section 382 Rights Agreement provides that an “Exempted Transaction,” as determined by the Board, cannot result in a person becoming an Acquiring Person.

Redemption

At any time prior to the earlier of (1) the Stock Acquisition Date and (2) the Final Expiration Date, the Company may redeem the Rights in whole, but not in part, at a price of $0.01 per Right (the “Redemption Price”) (subject to adjustment). The redemption of the Rights may be made effective at such time, on such basis and with such conditions as the Board in its sole discretion may establish. Immediately upon any redemption of the Rights (or such later time as the Board may establish), the Right to exercise the Rights will terminate, and the only right of the holders of Rights will be to receive the Redemption Price for each Right so held.

Exchange

At any time after any person or group becomes an Acquiring Person and prior to the acquisition by the Acquiring Person of 50% or more of the outstanding shares of Common Stock, the Board may exchange the Rights (other than Rights that are void), in whole or in part, at an exchange ratio equal to (i) a number of shares of Common Stock per Right with a value equal to the spread between the value of the number of shares of Common Stock for which the Rights may then be exercised and the Purchase Price or (ii) if prior to the acquisition by the Acquiring Person of 50% or more of the then-outstanding shares of Common Stock, one share of Common Stock per Right (subject to adjustment). Immediately upon an exchange of any Rights, the right to exercise such Rights will terminate and the only right of the holders of Rights will be to receive the number of shares of Common Stock equal to the number of such Rights held by such holder multiplied by an exchange ratio.

Anti-Dilution Provisions

The Board may adjust the Purchase Price of the Series A-1 Junior Participating Preferred Stock, the number of shares of Series A-1 Junior Participating Preferred Stock issuable and the number of outstanding Rights to prevent dilution that may occur as a result of certain events, including among others, a share dividend, a share split or a reclassification of the Series A-1 Junior Participating Preferred Stock or of the Common Stock. With certain exceptions, no adjustments to the Purchase Price will be required until cumulative adjustments amount to at least 1% of the Purchase Price.

Amendments

Prior to the Distribution Date, the Board may supplement or amend any provision of the Section 382 Rights Agreement in any respect without the approval of the holders of the Rights. From and after the Distribution Date, no amendment can materially adversely affect the interests of the holders of the Rights (excluding the interests of any Acquiring Person).

Other Provisions of Our Certificate and By-Laws and State Law Provisions That May Have Anti-Takeover Effects

Advance Notice Provisions

Our By-Laws provide that a stockholder must notify us in writing, within timeframes specified in the By-Laws, of any stockholder nomination of a director and of any other business that the stockholder intends to bring at a meeting of stockholders.

Amendments to Bylaws

Our Certificate and By-Laws provide that our By-Laws may be amended by our Board or by vote of the holders of the shares entitled to vote in the election of directors.

Changes to Board and Vacancies

Our By-Laws provide that directors may be removed only for cause by the affirmative vote of the holders of a majority of the shares then entitled to vote at an election of directors. The By-Laws also provide that the number of directors may be increased or decreased, within established limits, by affirmative vote of a majority of the whole Board. Under our Certificate, any vacancy on the Board, however occurring, including a vacancy resulting from an enlargement of the Board, may only be filled by vote of a majority of the directors then in office, whether or not a quorum.

State Law Provisions

In general, Section 203 of the DGCL prohibits a Delaware corporation with a class of voting stock listed on a national securities exchange or held of record by 2,000 or more shareholders from engaging in a business combination with an interested stockholder (generally, the beneficial owner of 15% or more of the corporation’s outstanding voting stock) for three years following the time the stockholder became an interested stockholder, unless, prior to that time: (1) the corporation’s board of directors approved either the business combination or the transaction that resulted in the stockholder becoming an interested stockholder, (2) at least two-thirds of the outstanding shares not owned by that interested stockholder approve the business combination, or (3) upon becoming an interested stockholder, that stockholder owned at least 85% of the outstanding shares, excluding those held by officers, directors and some employee stock plans. A “business combination” includes a merger, asset sale, or other transaction resulting in a financial benefit, other than proportionately as a stockholder, to the interested stockholder.

Exhibit 10.7

FIRST AMENDMENT TO THE

SECOND AMENDED AND RESTATED BY-LAWS

OF

ENZON PHARMACEUTICALS, INC.

On February 24, 2022, the Board of Directors of Enzon Pharmaceuticals, Inc., a Delaware corporation (the “Corporation”), unanimously approved and adopted the following amendment to the Corporation’s Second Amended and Restated By-Laws (the “By-Laws”) to be effective immediately:

The Board shall consist of at least one but no more than fifteen directors, the exact number of directors to be determined from time to time by resolution adopted by affirmative vote of a majority of the whole Board and such exact number shall be two until otherwise determined by resolution adopted by affirmative vote of a majority of the whole Board. As used in this Article 3, the term “whole Board” means the total number of directors which the Corporation would have if there were no vacancies.

EXHIBIT 21.1

ENZON PHARMACEUTICALS, INC.

Subsidiaries of Registrant

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EXHIBIT 23.1

CONSENT OF INDEPENDENT REGISTERED PUBLIC ACCOUNTING FIRM

We consent to the incorporation by reference in the Registration Statements of Enzon Pharmaceutical Inc. and Subsidiaries on Form S-1 (No. 333-250031) of our report dated February 25, 2022, on our audits of the consolidated financial statements as of year ended December 31, 2021 and December 31, 2020 and for each of the years then ended, which report is included in this Annual Report on Form 10-K to be filed on or about February 25, 2022.

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EXHIBIT 31.1

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CERTIFICATION PURSUANT TO

SECTION 302 OF

THE SARBANES-OXLEY ACT OF 2002

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I,Richard L. Feinstein, certify that:

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EXHIBIT 32.1

CERTIFICATION PURSUANT TO

18 U.S.C. §1350,

AS ADOPTED PURSUANT TO

SECTION 906 OF THE SARBANES-OXLEY ACT OF 2002

In connection with the Annual Report of Enzon Pharmaceuticals, Inc. (the “Company”) on Form 10-K for the year ended December 31, 2021 as filed with the Securities and Exchange Commission on the date hereof (the “Report”), I, Richard L. Feinstein, Chief Executive Officer, Chief Financial Officer and Secretary of the Company, certify, pursuant to 18 U.S.C. Section 1350, as adopted pursuant to Section 906 of the Sarbanes-Oxley Act of 2002, that to my knowledge:

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A signed original of this written statement required by Section 906 of the Sarbanes-Oxley Act of 2002 has been provided to Enzon Pharmaceuticals, Inc. and will be furnished to the Securities Exchange Commission or its staff upon request.