Filed Pursuant to Rule 424(b)(3)​

 Registration No. 333-293019​

PROSPECTUS

CONSENT SOLICITATION

PROSPECTUS FOR ISSUANCE OF UP TO 7,935,878 SHARES OF COMMON STOCK IN THE MERGER

PROSPECTUS FOR OFFER TO EXCHANGE SHARES OF SERIES C PREFERRED STOCK

FOR

COMMON STOCK

Dear Enzon Stockholders:

On behalf of the board of directors (the “Enzon Board”) of Enzon Pharmaceuticals, Inc. (“Enzon”), we are pleased to provide this letter and enclose the prospectus/consent solicitation/offer to exchange relating to the proposed merger of Enzon and Viskase Companies, Inc. (“Viskase”).

On June 20, 2025, Enzon, Viskase and EPSC Acquisition Corp. (“Merger Sub”) entered into an Agreement and Plan of Merger (the “Original Merger Agreement”), as amended by the First Amendment to the Agreement and Plan of Merger, dated October 24, 2025 (the “Merger Agreement Amendment,” and, together with the Original Merger Agreement, as it may be further amended, modified or supplemented from time to time in accordance with its terms, the “Merger Agreement”). Pursuant to the terms of, and subject to the conditions set forth in, the Merger Agreement, Merger Sub will merge with and into Viskase, with Viskase surviving the Merger as a wholly owned subsidiary of Enzon, and the separate corporate existence of Merger Sub will cease (the “Merger”), and promptly thereafter, Viskase will convert to a limited liability company under Delaware law. If the Merger is completed, the combined company will operate under the name “Viskase Holdings, Inc.” ​(the “Combined Company”) and its common stock will be quoted on the OTCQB tier of the OTC Markets Group, Inc. (the “Combined Company Common Stock”).

Upon consummation of the Merger, each share of Viskase’s common stock, par value $0.01 per share (the “Viskase Common Stock”) issued and outstanding immediately prior to the time at which the Merger becomes effective (the “Effective Time”) (other than shares of Viskase Common Stock (i) held by Viskase as treasury shares, (ii) owned by Enzon, Merger Sub or a wholly owned subsidiary of Viskase, Enzon or Merger Sub immediately prior to the Effective Time and (iii) dissenting shares) will be automatically converted into the right to receive a number of shares of Enzon’s common stock, par value $0.01 per share (the “Enzon Common Stock”) equal to the exchange ratio set forth in the Merger Agreement and described in the enclosed prospectus/consent solicitation/offer to exchange.

No less than twenty-five (25) business days prior to the Effective Time, Enzon will commence an exchange offer pursuant to which Enzon will offer each holder of its Series C Non-Convertible Redeemable Preferred Stock, par value $0.01 per share (the “Enzon Series C Preferred Stock”) to exchange each share of Enzon Series C Preferred Stock held by such stockholder for a number of shares of Enzon Common Stock equal to (i) the aggregate liquidation preference of each share of Enzon Series C Preferred Stock, divided by (ii) the price equal to the average of the volume-weighted average price of Enzon Common Stock on the OTC market for the last twenty (20) trading days prior to (and including) October 24, 2025, rounded down to the nearest 1/100th of a penny (the “Series C Exchange Offer”). The accompanying prospectus/consent solicitation/offer to exchange will also be used in connection with the Series C Exchange Offer. The Series C Exchange Offer will expire at one minute after 11:59 p.m., Eastern Time, on February 27, 2026 unless extended or terminated in Enzon’s sole discretion or in accordance with applicable law.

Additionally, on June 20, 2025, concurrently with the execution of the Original Merger Agreement, Icahn Enterprises Holdings L.P. and certain of its affiliates (together, the “IEH Parties”) entered into a support agreement (as amended by the First Amendment to the Support Agreement, dated October 24, 2025, and as it may be further amended, modified or supplemented from time to time in accordance with its terms, the “IEH Support Agreement”) with Enzon and Viskase, pursuant to which the IEH Parties agreed to, among other things, not participate in the Series C Exchange Offer and, instead, convert their Enzon Series C Preferred Stock into Enzon Common Stock (the “IEH Share Exchange”).

As a result of the foregoing, and assuming that the Enzon Series C Preferred Stock is exchanged for Enzon Common Stock in full pursuant to the Series C Exchange Offer and the IEH Share Exchange, (a) holders of Enzon Common Stock immediately prior to the Effective Time are expected to own approximately 5% of the Combined Company Common Stock, (b) holders of Enzon Series C Preferred Stock are expected to own approximately 40% of the Combined Company Common Stock and (c) holders of Viskase Common Stock are expected to own 55% of the Combined Company Common Stock. On June 20, 2025, the IEH Parties, as the holders of the majority of outstanding shares of Viskase Common Stock, executed and delivered the requisite

action by written consent to Viskase consenting to the adoption of the Merger Agreement and the Merger by Viskase. Furthermore, on November 11, 2025, the IEH Parties, as the holders of the majority of the outstanding shares of Viskase Common Stock, executed and delivered the requisite action by written consent to Viskase consenting to the adoption of the Merger Agreement Amendment and the Merger by Viskase.

Under the Merger Agreement, prior to the Effective Time, Enzon intends to effect an amendment to the Enzon Amended and Restated Certificate of Incorporation (the “Enzon Charter,” and such amendment, the “Enzon Charter Amendment”) to effect the consolidation of the issued and outstanding shares of Enzon Common Stock at a ratio of 1 for 100 (the “Reverse Stock Split”).

Enzon is asking its stockholders to approve the Enzon Charter Amendment to effect the Reverse Stock Split, which will reduce the total number of shares of Enzon Common Stock outstanding, and to approve the adoption of the Merger Agreement.

The adoption of the Merger Agreement and the consummation of the transactions contemplated thereby, including the Reverse Stock Split, requires an affirmative vote by written consent of the holders of a majority of the outstanding shares of Enzon Common Stock entitled to vote thereon. We are therefore sending the accompanying prospectus/consent solicitation/​offer to exchange to the holders of Enzon Common Stockto request that they consider and approve, via written consent, (i) the Reverse Stock Split (the “Reverse Stock Split Proposal”) and (ii) the adoption of the Merger Agreement (the “Merger Proposal” and, together with the Reverse Stock Split Proposal, the “Enzon Proposals”). Because Viskase stockholders have already approved the Merger by written consent, no meeting of Viskase stockholders will be held with respect to the Merger, and their approval of the Merger is not being sought.

Pursuant to the IEH Support Agreement, the IEH Parties agreed to, among other things and subject to certain exceptions, deliver written consents with respect to all of the issued and outstanding shares of Enzon Common Stock held by the IEH Parties approving the Enzon Proposals. As of January 29, 2026 (the “Enzon Record Date”), the IEH Parties are entitled to vote 36,056,636 shares of Enzon Common Stock, or approximately 48.6% of the issued and outstanding shares of Enzon Common Stock. Accordingly, assuming delivery of written consents from the IEH Parties pursuant to the terms of the IEH Support Agreement, written consents with respect to 1,050,666 shares of Enzon Common Stock will be needed to approve the Enzon Proposals.

More information about Enzon, Viskase and the Merger is contained in the accompanying prospectus/consent solicitation/offer to exchange. Enzon urges you to read the accompanying prospectus/consent solicitation/offer to exchange carefully and in its entirety. IN PARTICULAR, YOU SHOULD CAREFULLY CONSIDER THE MATTERS DISCUSSED IN THE SECTION TITLED “RISK FACTORS” BEGINNING ON PAGE 57 OF THE ACCOMPANYING PROSPECTUS/CONSENT SOLICITATION/​OFFER TO EXCHANGE.

Enzon and Viskase are excited about the opportunities the Merger brings to both Enzon and Viskase stockholders and thank you for your consideration and continued support.

/s/ Richard L. Feinstein

Richard L. Feinstein, Enzon Pharmaceuticals, Inc.
Chief Executive Officer, Chief Financial Officer
and Secretary

NEITHER THE SECURITIES AND EXCHANGE COMMISSION NOR ANY STATE SECURITIES REGULATORY AGENCY HAS APPROVED OR DISAPPROVED THE TRANSACTIONS DESCRIBED IN THE ACCOMPANYING PROSPECTUS/CONSENT SOLICITATION/OFFER TO EXCHANGE, PASSED UPON THE MERITS OR FAIRNESS OF THE MERGER OR RELATED TRANSACTIONS OR PASSED UPON THE ADEQUACY OR ACCURACY OF THE DISCLOSURE IN THIS PROSPECTUS/CONSENT SOLICITATION/OFFER TO EXCHANGE. ANY REPRESENTATION TO THE CONTRARY CONSTITUTES A CRIMINAL OFFENSE.

The accompanying prospectus/consent solicitation/offer to exchange is dated January 28, 2026, and is expected to be mailed to Enzon stockholders on or about February 4, 2026.

 

ENZON PHARMACEUTICALS, INC.
20 Commerce Drive, Suite 135
Cranford, New Jersey 07016

NOTICE OF SOLICITATION OF WRITTEN CONSENT OF THE STOCKHOLDERS OF ENZON

Dear Enzon Stockholders:

Pursuant to an Agreement and Plan of Merger, dated as of June 20, 2025 (the “Original Merger Agreement”), by and among Enzon Pharmaceuticals, Inc. (“Enzon”), Viskase Companies, Inc. (“Viskase”) and EPSC Acquisition Corp. (“Merger Sub”), as amended by the First Amendment to the Agreement and Plan of Merger, dated October 24, 2025 (the “Merger Agreement Amendment,” and, together with the Original Merger Agreement, as it may be further amended, modified or supplemented from time to time in accordance with its terms, the “Merger Agreement”), Merger Sub will merge with and into Viskase, with Viskase surviving the merger as a wholly owned subsidiary of Enzon, on the terms and subject to the satisfaction of the conditions described in the Merger Agreement (the “Merger”), and promptly thereafter, Viskase will convert into a limited liability company under Delaware law.

The accompanying prospectus/consent solicitation/offer to exchange is being delivered to you on behalf of the board of directors of Enzon (the “Enzon Board”) to request that holders of Enzon’s common stock, par value $0.001 per share (the “Enzon Common Stock”), as of the record date of January 29, 2026 (the “Enzon Record Date”), execute and return written consents to approve proposals for (i) an amendment to the Enzon Amended and Restated Certificate of Incorporation (the “Enzon Charter,” and such amendment, the “Enzon Charter Amendment”) to effect the consolidation of the issued and outstanding shares of Enzon Common Stock at a ratio of 1 for 100 in connection with the Merger (the “Reverse Stock Split” and, such proposal, the “Reverse Stock Split Proposal”) and (ii) the adoption of the Merger Agreement (the “Merger Proposal” and, together with the Reverse Stock Split Proposal, the “Enzon Proposals”). Only holders of Enzon Common Stock as of the close of business on the Enzon Record Date are entitled to receive notice of solicitation of written consent.

As of the Enzon Record Date, 74,214,603 shares of Enzon Common Stock are issued and outstanding and the consent of 37,107,302 of the issued and outstanding shares of Enzon Common Stock is required to approve each of the Enzon Proposals, which represents a majority of the issued and outstanding shares of Enzon Common Stock as of the Enzon Record Date. As of the Enzon Record Date, Icahn Enterprises Holdings L.P. and its affiliates (together, the “IEH Parties”) are entitled to vote 36,056,636 shares of Enzon Common Stock, or approximately 48.6% of the issued and outstanding shares of Enzon Common Stock. The IEH Parties entered into a support agreement with Enzon and Viskase (as amended by the First Amendment to the Support Agreement, dated October 24, 2025, by and among Enzon, Viskase and the IEH Parties), pursuant to which the IEH Parties agreed to, among other things, and subject to certain exceptions, deliver written consents with respect to all of the issued and outstanding shares of Enzon Common Stock held by the IEH Parties approving the Enzon Proposals. Accordingly, assuming delivery of written consents from the IEH Parties pursuant to the terms of the IEH Support Agreement, written consents with respect to 1,050,666 shares of Enzon Common Stock will be needed to approve the Enzon Proposals.

The accompanying prospectus/consent solicitation/offer to exchange describes the Reverse Stock Split Proposal, the Merger Proposal and the actions to be taken in connection therewith and provides additional information about the parties involved. Please give this information your careful attention. A copy of the Merger Agreement is attached as Annex A to the accompanying prospectus/consent solicitation/offer to exchange and a copy of the Merger Agreement Amendment is attached as Annex A-1 to the accompanying prospectus/consent solicitation/offer to exchange.

 

 

A special committee of the Enzon Board consisting of only independent and disinterested directors (the “Enzon Special Committee”) and the Enzon Board considered the terms of the Merger Agreement. The Enzon Board, upon the unanimous recommendation of the Enzon Special Committee, unanimously recommends that the holders of Enzon common stock entitled to vote deliver a written consent “FOR” the approval of the Reverse Stock Split Proposal and the Merger Proposal by executing and returning the written consent, electronically or by mail, furnished with the prospectus/consent solicitation/offer to exchange.

On June 20, 2025, the IEH Parties, as the holders of the majority of outstanding shares of Viskase, executed and delivered an action by written consent to Viskase consenting to the adoption of the Merger Agreement and the Merger by Viskase. On November 11, 2025, the IEH Parties, as the holders of the majority of the outstanding shares of Viskase, executed and delivered an action by written consent to Viskase consenting to the adoption of the Merger Agreement Amendment and approval of the Merger by Viskase. Such written consents constitute the requisite stockholder approval required for Viskase to consummate the Merger. Neither Enzon nor Viskase will hold a stockholders’ meeting to consider the Reverse Stock Split Proposal or the Merger Proposal.

The consent of the Enzon stockholders is very important.   The Merger cannot be completed unless each of the Reverse Stock Split Proposal and the Merger Proposal is approved by the written consent of the holders of a majority of the issued and outstanding shares of Enzon Common Stock entitled to vote thereon. The enclosed prospectus/consent solicitation/offer to exchange provides Enzon stockholders with detailed information about the Merger, the Reverse Stock Split Proposal and the Merger Proposal. We encourage you to review these materials carefully and provide your written consent as soon as possible by following the instructions in the accompanying prospectus/consent solicitation/offer to exchange to make sure that your shares are properly represented. If your shares are held in “street name” by a brokerage firm, bank or other nominee, please follow the instructions furnished by such brokerage firm, bank or other nominee. If you do not execute and return your written consent, or otherwise withhold your written consent, it will have the same effect as voting against the Reverse Stock Split Proposal and the Merger Proposal.

The Enzon Board has set the Enzon Record Date for determining the holders of Enzon common stock entitled to execute and deliver written consents with respect to this solicitation. If you are a holder of Enzon common stock on the Enzon Record Date, you are urged to complete, date and sign the enclosed written consent and return it to Enzon. Please see the section titled “Enzon Solicitation of Written Consent” of the accompanying prospectus/consent solicitation/offer to exchange for further information.

Please complete, date and sign the written consent furnished with the accompanying prospectus/consent solicitation/offer to exchange and return it promptly to Enzon by one of the means described in the section titled “The Merger — Enzon Solicitation of Written Consents” as soon as possible. Once a sufficient number of consents to adopt the Enzon Proposals has been received, the consent solicitation will conclude.

The Enzon Board has set 5:00 p.m., Eastern Time, on February 27, 2026, as the target date for the receipt of written consents.

By order of the Enzon Board of Directors of Enzon Pharmaceuticals, Inc.​

/s/ Richard L. Feinstein​

Richard L. Feinstein​

Chief Executive Officer, Chief Financial Officer and Secretary​

Cranford, New Jersey

January 28, 2026

 

 

ADDITIONAL INFORMATION

This document, which forms part of a registration statement on Form S-4 filed with the SEC by Enzon (File No. 333-293019) (the “Registration Statement”), constitutes a prospectus of Enzon under Section 5 of the Securities Act, with respect to (i) the issuance of shares of Enzon Common Stock in the event that the merger described in this prospectus/consent solicitation/offer to exchange is consummated and (ii) the issuance of Enzon Common Stock in connection with the Series C Exchange Offer. This document also constitutes a consent solicitation of Enzon stockholders pursuant to which Enzon stockholders are being asked to consider and consent to the merger, among other matters.

Enzon files periodic reports and other information with the SEC as required by the Exchange Act. You can obtain any of the documents delivered with this prospectus/consent solicitation/offer to exchange from the SEC’s website at www.sec.gov, and they are available for you to review at the SEC’s Public Reference Room located at 100 F Street, N.E., Washington, D.C. 20549. This prospectus/consent solicitation/offer to exchange also includes important business and financial information about Viskase. Additional copies are available to you without charge upon your request in writing, by email or by telephone from Enzon or Viskase at their respective addresses and telephone numbers listed below or by accessing such documents on the websites listed below. Any other information provided on the websites listed below is not a part of this prospectus/​consent solicitation/offer to exchange and should not be relied upon in connection with your evaluation of the Reverse Stock Split Proposal and the Merger Proposal described herein.

In addition, if you have questions about the merger or the solicitation of Enzon written consents, or if you need to obtain copies of this prospectus/consent solicitation/offer to exchange or other related documents, you may contact the consent solicitor of Enzon, whose contact information is as follows:

HKL & Co., LLC
3 Columbus Circle, 15FL
New York, New York 10019
Banks and Brokerage Firms Please Call Collect: (212) 468-5380
All Others Call Toll-Free: (800) 326-5997
Email: enzn@hklco.com

To ensure timely delivery, any request must be made no later than February 20, 2026, which is five business days before the expiration date of the Series C Exchange Offer.

For additional details about where you can find information, please see the section titled “Where You Can Find More Information” in this prospectus/consent solicitation/offer to exchange.

 

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ABOUT THIS PROSPECTUS/CONSENT SOLICITATION/OFFER TO EXCHANGE

Enzon has filed with the SEC a registration statement on Form S-4 (File No. 333-293019), of which this prospectus/consent solicitation/offer to exchange forms a part.

You should rely on the information contained in this prospectus/consent solicitation/offer to exchange, including the detailed information regarding Enzon.

Neither Enzon nor Viskase has authorized anyone to provide you with information different from that contained in this prospectus/consent solicitation/offer to exchange. Enzon takes no responsibility for, and can provide no assurance as to the reliability of, any other information that others may give you. You should not assume that the information in this prospectus/consent solicitation/offer to exchange, any document incorporated herein by reference or any Annex or Exhibit is accurate as of any date other than the date on the front of those documents. You should not consider this prospectus/consent solicitation/offer to exchange to be an offer or solicitation relating to the securities in any jurisdiction in which such an offer or solicitation relating to the securities is not authorized. Furthermore, you should not consider this prospectus/consent solicitation/offer to exchange to be an offer or solicitation relating to the securities offered hereby if the Person making the offer or solicitation is not qualified to do so, or if it is unlawful for you to receive such an offer or solicitation.

Except where the context otherwise indicates, the information concerning Enzon contained in or incorporated by reference into this prospectus/consent solicitation/offer to exchange has been provided by Enzon, and the information concerning Viskase contained in this prospectus/consent solicitation/offer to exchange has been provided by Viskase. Enzon has relied on Viskase to provide such information and has not independently verified the information provided by Viskase. Enzon has also relied on Viskase’s representations and warranties related to such information in the Merger Agreement.

Prior to making any decision with respect to the proposals herein, you should read this prospectus/​consent solicitation/offer to exchange, together with the documents incorporated by reference herein and the Annexes and Exhibits thereto, and for additional information, please see the description in the section titled “Where You Can Find More Information” in this prospectus/consent solicitation/offer to exchange.

 

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TABLE OF CONTENTS

 

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FREQUENTLY USED TERMS

Unless otherwise indicated or as the context otherwise requires, all references in this prospectus/​consent solicitation/offer to exchange:

“382 Rights Agreement” means that certain Section 382 Rights Agreement, dated as of August 14, 2020, as amended, by and between Enzon and Continental Stock Transfer & Trust Company.

“Acceptable Confidentiality Agreement” means a customary confidentiality agreement entered into by Enzon containing provisions (i) not less favorable to Enzon in any material respect than those set forth in the Confidentiality Agreement, (ii) that require any counterparty thereto (and any of its Affiliates and Representatives named therein) that receives non-public information of or with respect to Enzon and its Subsidiaries to keep such information confidential; provided that the provisions contained therein are no less restrictive in any material respect to such counterparty (and any of its Affiliates and Representatives named therein) than those set forth in the Confidentiality Agreement (it being understood that an Acceptable Confidentiality Agreement need not include a standstill provision) and (iii) does not prohibit Enzon from providing any information to Viskase in accordance with, and otherwise complying with the Merger Agreement.

“Affiliate” means, with respect to any Person, any other Person that directly, or through one (1) or more intermediaries, controls or is controlled by or is under common control with such Person; provided, however, that with respect to (i) Viskase, “Affiliate” means any Person that is controlled, directly or indirectly, by Viskase and (ii) Enzon, “Affiliate” means any Person that is controlled, directly or indirectly, by Enzon. As used herein, the term “control” means: (A) the power to vote at least ten percent (10%) of the voting power of a Person or (B) the possession, directly or indirectly, of any other power to direct or cause the direction of the management and policies of such a Person, whether through ownership of voting securities, by contract or otherwise.

“Beneficially Own” means, with respect to any securities, having “beneficial ownership” of such securities for purposes of Rule 13d-3 or 13d-5 under the Exchange Act (or any successor statute or regulation).

“Cash on Hand” means all cash and cash equivalents of Enzon, in each case, determined in accordance with U.S. GAAP, and held in any account of Enzon, (i) excluding the amount of any issued but uncleared checks, wires or drafts and any cash overdrafts and restricted cash and (ii) including checks and drafts deposited for the account of Enzon or on hand at Enzon or available for deposit for the account of Enzon.

“Closing” means the Closing of the Merger.

“Closing Date” means date upon which the Closing occurs.

“Code” means the Internal Revenue Code of 1986, as amended.

“Combined Company” means Enzon, after giving effect to the Merger, which will be renamed “Viskase Holdings, Inc.” in connection with the Closing.

“Confidentiality Agreement” means that certain confidentiality agreement between Viskase and Enzon, dated as of January 3, 2025.

“Court” means the Delaware Court of Chancery.

“Delaware LLC Act” means the Limited Liability Company Act of the State of Delaware.

“DGCL” means the General Corporation Law of the State of Delaware.

“Dissenting Viskase Shares” means shares of Viskase Common Stock that are issued and outstanding immediately prior to the Effective Time and held by the stockholders of Viskase who have not voted in favor of the adoption of the Merger Agreement (or consented thereto in writing) and who shall have properly demanded appraisal of such shares of Viskase Common Stock in accordance with, and who have otherwise

 

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complied in all respects with, Section 262 of the DGCL and, as of the Effective Time, have neither effectively withdrawn nor lost their rights to such appraisal under the DGCL.

“Effective Time” means the time at which the Merger shall become effective.

“EisnerAmper” means EisnerAmper LLP, an independent registered public accounting firm, serving as Enzon’s auditor.

“Enzon” means Enzon Pharmaceuticals, Inc., a Delaware corporation.

“Enzon 20-Day VWAP” means the price equal to the average of the volume-weighted average price of Enzon Common Stock on the “OTCQB” tier of the OTC (as reported by Bloomberg or, if not reported thereby, in another authoritative source mutually selected by Enzon, Viskase and IEH) for the last twenty (20) Trading Days prior to (and including) October 24, 2025, rounded down to the nearest 1/100th of a penny (as adjusted to take into account the Reverse Stock Split, to the extent the Reverse Stock Split is effectuated prior to the date of the relevant issuance of Enzon Common Stock). The Enzon 20-Day VWAP as calculated pursuant to the definition provided in the Merger Agreement is $0.08 per share of Enzon Common Stock, which after giving effect to the Reverse Stock Split of 1 for 100, will be adjusted to $7.83.

“Enzon Balance Sheet Date” means the date of the most recent consolidated balance sheet included, prior to the date of the Merger Agreement, in the material reports, schedules, forms, statements and other documents required to be filed or furnished by Enzon with or to the SEC pursuant to the Securities Act or the Exchange Act since January 1, 2023.

“Enzon Board” means the board of directors of Enzon.

“Enzon By-Laws” means the Second Amended and Restated By-Laws of Enzon, as amended and restated from time to time.

“Enzon Charter” means the Amended and Restated Certificate of Incorporation of Enzon, as amended and restated from time to time.

“Enzon Common Stock” means Enzon’s common stock, $0.01 par value per share.

“Enzon Organizational Documents” means the Enzon Charter and the Enzon By-Laws.

“Enzon Recommendation” means the recommendation by the Enzon Board (acting upon the unanimous recommendation of the Enzon Special Committee) that the stockholders of Enzon entitled to vote thereon (i) adopt the Merger Agreement and (ii) approve an amendment to the Enzon Charter in the form of Exhibit B to the Merger Agreement Amendment, which is attached as Annex A-1 to this prospectus/consent solicitation/offer to exchange to, among other things, effect the Reverse Stock Split.

“Enzon Series C Preferred Stock” means Enzon’s Series C Non-Convertible Redeemable Preferred Stock, $0.01 par value per share.

“Enzon Special Committee” means a special committee of the Enzon Board consisting only of independent and disinterested directors that the Enzon Board determined to be disinterested directors within the meaning of the DGCL.

“Enzon Stock” means any and all classes of shares of Enzon, including Enzon Common Stock and Enzon Series C Preferred Stock.

“Enzon Stockholder Approval” means the affirmative vote (in Person, by proxy or by written consent) of the holders of a majority of the outstanding shares of Enzon Common Stock entitled to vote thereon to (i) adopt the Merger Agreement and (ii) approve an amendment to the Enzon Charter in the form of Exhibit B to the Merger Agreement Amendment, which is attached as Annex A-1 to this prospectus/​consent solicitation/offer to exchange to, among other things, effect the Reverse Stock Split.

“Enzon Transaction Litigation” means any stockholder litigation or claim against Enzon and/or its directors or officers relating to the Merger or the other transactions contemplated by the Merger Agreement.

 

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“Exchange Act” means the Securities Exchange Act of 1934, as amended, and the rules and regulations promulgated thereunder.

“FASB” means the Financial Accounting Standards Board.

“Grant Thornton” means Grant Thornton LLP, an independent registered public accounting firm, serving as Viskase’s auditor.

“HSR Act” means the Hart-Scott-Rodino Antitrust Improvements Act of 1976, as amended.

“IEH” means Icahn Enterprises Holdings L.P., a Delaware limited partnership.

“IEH Parties” means, collectively, IEH, American Entertainment Properties Corp., a Delaware corporation (“AEP”), Icahn Partners LP, a Delaware limited partnership (“IPLP”), and Icahn Partners Master Fund LP, a Delaware limited partnership (“IPMF”).

“IEH Share Exchange” means the exchange of all shares of Enzon Series C Preferred Stock Beneficially Owned by each IEH Party for a number of shares of Enzon Common Stock equal to (i) (A) the aggregate Liquidation Preference of such shares of Enzon Series C Preferred Stock, divided by (ii) the Enzon 20-Day VWAP.

“IEH Support Agreement” means the Support Agreement, dated as of June 20, 2025, by and among Enzon, Viskase and the IEH Parties, a copy of which is attached as Annex B to this prospectus/consent solicitation/offer to exchange, as amended by the IEH Support Agreement Amendment and as the same may be amended, modified or supplemented from time to time in accordance with its terms.

“IEH Support Agreement Amendment” means that certain First Amendment to the Support Agreement, dated October 24, 2025, by and among Enzon, Viskase and the IEH Parties, a copy of which is attached as Annex B-1 to this prospectus/consent solicitation/offer to exchange.

“IRS” means the United States Internal Revenue Service.

“Intended Tax Treatment” means (i) the Merger and the conversion of Viskase into a limited liability company undertaken as part of the Merger Agreement will, taken together, qualify as a “reorganization” within the meaning of Section 368(a) of the Code and the regulations promulgated thereunder, (ii) Enzon and Viskase will each be a party to the reorganization within the meaning of Section 368(b) of the Code and (iii) the Merger Agreement will constitute a “plan of reorganization” within the meaning of the Code.

“Lien” means any mortgage, pledge, security interest, encumbrance, title defect, lien (statutory or other), conditional sale agreement, claim, charge, adverse right, prior assignment, hypothecation, limitation or restriction.

“Liquidation Preference” has the meaning given to it in the Certificate of Designation of Series C Non-Convertible Redeemable Preferred Stock of Enzon, which, for the avoidance of doubt, includes accrued and unpaid dividends on the Enzon Series C Preferred Stock.

“Merger” means the Merger of Merger Sub with and into Viskase with Viskase continuing as the surviving corporation and as a wholly owned Subsidiary of Enzon following the Merger.

“Merger Agreement” means the Agreement and Plan of Merger, dated as of June 20, 2025, by and among Enzon, Merger Sub and Viskase, a copy of which is attached as Annex A to this prospectus/consent solicitation/offer to exchange, as amended by the Merger Agreement Amendment and as the same may be amended, modified or supplemented from time to time in accordance with its terms.

“Merger Agreement Amendment” means that certain First Amendment to the Merger Agreement, dated October 24, 2025, by and among Enzon, Merger Sub and Viskase, a copy of which is attached as Annex A-1 to this prospectus/consent solicitation/offer to exchange.

“Merger Sub” means EPSC Acquisition Corp., a Delaware corporation and wholly owned Subsidiary of Enzon.

 

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“Minimum Cash Condition” means at the Closing, Enzon having Cash on Hand of an amount that is equal to or greater than $40,000,000.

“OTC Markets” means OTC Markets Group, Inc.

“Permitted Lien” means (i) Liens for taxes not yet due and payable or that are being contested in good faith by appropriate proceedings and for which adequate reserves have been established in accordance with GAAP on the balance sheet of the applicable Person, (ii) mechanics’, carriers’, workers’, repairers’, materialmen’s, warehousemen’s, lessor’s, landlord’s and other similar Liens arising or incurred in the ordinary course of business, (iii) non-monetary Liens that would be disclosed on title policies, title commitments and/or surveys; provided that the same do not materially interfere with the business of Enzon or its Subsidiaries or Viskase or its Subsidiaries, as applicable, or the operation of the property as presently conducted to which they apply, (iv) Liens arising out of pledges or deposits under worker’s compensation laws, unemployment insurance, old age pensions or other social security or retirement benefits or similar legislation, (v) deposits securing liability to insurance carriers under insurance or self-insurance arrangements, (vi) deposits to secure the performance of bids, tenders, trade contracts (other than contracts for indebtedness for borrowed money), leases, statutory obligations, surety and appeal bonds, performance bonds and other obligations of a like nature incurred in the ordinary course of business, (vii) easements, rights of way, zoning ordinances, variances, any set of facts that would be disclosed by an accurate up-to-date survey and other similar encumbrances affecting a Person’s properties, none of which materially interfere with the business of Enzon or its Subsidiaries or Viskase or its Subsidiaries, as applicable, or the operation of the property as presently conducted to which they apply, (viii) non-exclusive licenses of intellectual property rights granted in the ordinary course of business and (ix) Liens not created by any of Enzon or Viskase (or their Subsidiaries) that affect the underlying fee interest of any leased real property of Enzon or Viskase (or their Subsidiaries).

“Person” means an individual, corporation, limited liability company, partnership, association, trust, other entity or group (as defined in the Exchange Act).

“Proposed Charter Amendment” means the Amendment to the Enzon Charter, the form of which is attached to this prospectus/consent solicitation/offer to exchange as Exhibit B to the Merger Agreement Amendment, which is attached as Annex A-1 to this prospectus/consent solicitation/offer to exchange.

“Representative” means, with respect to any Person, such Person’s Affiliates and its and their respective officers, directors, managers, partners, employees, accountants, counsel, financial advisors, consultants and other advisors or Representatives.

“Reverse Stock Split” means the consolidation of the issued and outstanding shares of Enzon Common Stock at a ratio of 1 for 100 as contemplated by the Merger Agreement and the Proposed Charter Amendment.

“SEC” means the U.S. Securities and Exchange Commission.

“Securities Act” means the Securities Act of 1933, as amended, and the rules and regulations promulgated thereunder.

“Series C Exchange Offer” means the exchange offer pursuant to which Enzon will offer each holder of Enzon Series C Preferred Stock to exchange each such holder’s shares of Enzon Series C Preferred Stock for shares of Enzon Common Stock, pursuant to the terms and subject to the conditions set forth in the Merger Agreement.

“Subsidiary” means, when used with respect to any Person, (i) any corporation, partnership or other organization, whether incorporated or unincorporated, (A) of which such Person or any other Subsidiary of such Person is a general partner (excluding partnerships, the general partnership interests of which held by such Person or any Subsidiary of such Person do not have a majority of the voting interests in such partnership) or (B) at least a majority of the securities or other interests of which having by their terms ordinary voting power to elect a majority of the board of directors or others performing similar functions with respect to such corporation or other organization is directly or indirectly owned or controlled by such Person or by any one (1) or more of its Subsidiaries, or by such Person and one (1) or more of its Subsidiaries, or (ii) any partnership, limited liability company, association, joint venture or other business

 

4

 

entity, of which a majority of the partnership, joint venture or other similar ownership interest thereof is at the time owned or controlled, directly or indirectly, by that Person or one (1) or more Subsidiaries of that Person or a combination thereof.

“Surviving Company” means Viskase Companies, Inc., a Delaware corporation, after giving effect to the Merger of Viskase and Merger Sub, in connection with the Closing.

“Surviving Company Conversion” means the conversion of the Surviving Company into a limited liability company under Section 266 of the DGCL and Section 18-214 of the Delaware LLC Act.

“Takeover Law” means any law that restricts a “business combination,” “control share acquisition,” “fair price,” “moratorium” or other anti-takeover law.

“Total Closing Share Number” means the number equal to (i) the number of shares of Enzon Common Stock issued and outstanding as of immediately prior to the Effective Time (after giving effect to the Reverse Stock Split, the IEH Share Exchange and the shares of Enzon Common Stock issued pursuant to the Series C Exchange Offer), divided by (ii) 0.45.

“Trading Day” means, with respect to Enzon Common Stock, a day on which shares of Enzon Common Stock are traded on OTC.

“U.S. GAAP” means generally accepted accounting principles in the United States.

“Viskase” means Viskase Companies, Inc., a Delaware corporation.

“Viskase Balance Sheet Date” means March 31, 2025.

“Viskase Board” means the board of directors of Viskase.

“Viskase Bylaws” means the Amended and Restated Bylaws of Viskase, as amended and restated from time to time.

“Viskase Charter” means the Amended and Restated Certificate of Incorporation of Viskase, as amended and restated from time to time.

“Viskase Common Stock” means Viskase’s common stock, $0.01 par value per share.

“Viskase Closing Share Number” means the number of shares of Enzon Common Stock equal to (i) the Total Closing Share Number, minus (ii) the number of shares of Enzon Common Stock issued and outstanding as of immediately prior to the Effective Time (after giving effect to the Reverse Stock Split, the IEH Share Exchange and the shares of Enzon Common Stock issued pursuant to the Series C Exchange Offer).

“Viskase Credit Agreement” means that certain Credit Agreement, dated as of October 9, 2020, by and among Viskase, Bank of America, N.A., and other lenders, as amended by the First Amendment, dated August 13, 2021, as further amended by the Second Amendment, dated August 10, 2022, and as further amended by the Limited Waiver Third Amendment to Credit Agreement, dated February 14, 2025, the Fourth Amendment to Credit Agreement, dated July 25, 2025, the Fourth Amendment Fee Letter to Credit Agreement, dated July 25, 2025, the Fifth Amendment to Credit Agreement, dated October 10, 2025 and the Sixth Amendment to the Credit Agreement, dated January 23, 2026.

“Viskase Material Adverse Effect” means any event, change, circumstance, effect, development or state of facts that, individually or in the aggregate, is or would reasonably be expected to (i) be materially adverse to the business, results of operations, assets or financial condition of Viskase and its Subsidiaries, taken as a whole, or (ii) materially delay, impede or prevent the transactions contemplated by the Merger Agreement on or before the Termination Date; provided, however, that for purposes of subclause (i), Viskase Material Adverse Effect shall not include the effect of any event, change, circumstance, effect, development or state of facts to the extent it results from or arises out of (A) general economic or political conditions or securities, credit, financial or other capital markets conditions, in each case in the United States or any foreign jurisdiction, (B) changes or conditions generally affecting the industries, businesses, or segments thereof, in which Viskase or its Subsidiaries operate, (C) any change after the date thereof in applicable law, regulation,

 

5

 

GAAP or accounting standards (or authoritative interpretation of any of the foregoing), (D) the announcement of the IEH Support Agreement or the transactions contemplated thereby or the terms thereof or the consummation of the transactions contemplated by the Merger Agreement, including the impact thereof on the relationships of Viskase or its Subsidiaries with customers, suppliers, distributors, partners, officers or employees, (E) pandemics, epidemics, COVID-19, acts of war (whether or not declared), armed hostilities, sabotage, terrorism or cyber-attack, or any escalation or worsening of any acts of war, armed hostilities, sabotage, terrorism or cyber-attack threatened or underway as of the date of the Merger Agreement (including requirements for business closures, restrictions on operations or “sheltering-in-place”), (F) earthquakes, hurricanes, floods, or other natural disasters or other weather-related or force majeure events, (G) any failure, in and of itself, by Viskase to meet any internal or published projections, forecasts, estimates or predictions in respect of revenues, earnings or other financial or operating metrics for any period, (H) any change in the market price or trading volume of Viskase’s securities or downgrade in Viskase’s credit rating, (I) tariffs, trade wars or similar matters, (J) any demands, litigation or similar actions brought by stockholders of Viskase in connection with the Merger Agreement and the transactions contemplated thereby or (K) the taking of any specific action expressly required by the Merger Agreement or taken with Enzon’s written consent or the failure to take any specific action expressly prohibited by the Merger Agreement and as for which Enzon declined to consent; except, in each case, with respect to the exceptions set forth in (A), (B), (C) or (E), to the extent materially disproportionately affecting Viskase and its Subsidiaries, taken as a whole, relative to other similarly situated companies in the industries in which Viskase operates, then the incremental material disproportionate impact of such event, change, circumstance, effect, development or state of facts shall be taken into account for the purpose of determining whether a Viskase Material Adverse Effect has occurred. Notwithstanding the foregoing, if Enzon, Merger Sub or any of their respective Representatives knew of the material facts of a matter prior to October 24, 2025 (including in connection with any request made pursuant to Section 5.1 of the Merger Agreement), then no effect, change, event or occurrence arising out of, or resulting from, such facts shall constitute a Viskase Material Adverse Effect for all purposes under the Merger Agreement; provided that, for the avoidance of doubt, a Viskase Material Adverse Effect may result from facts that Enzon, Merger Sub or any of their respective Representatives become aware of after October 24, 2025.

“Viskase Organizational Documents” means the Viskase Charter and the Viskase Bylaws.

“Viskase Preferred Stock” means Viskase’s preferred stock, par value $0.01 per share.

“Viskase Special Committee” means a special committee of the Viskase Board consisting only of independent and disinterested directors that the Viskase Board determined to be disinterested directors within the meaning of the DGCL.

“Viskase Stockholder Approval” means the affirmative vote (in person, by proxy or by written consent) of the holders of a majority of the outstanding shares of Viskase Common Stock to (i) adopt the Merger Agreement and (ii) approve the Merger.

“Viskase Transaction Litigation” means any stockholder litigation or claim against Viskase and/or its directors or officers relating to the Merger or the other transactions contemplated by the Merger Agreement.

 

6

 

QUESTIONS AND ANSWERS ABOUT THE MERGER AND THE CONSENT SOLICITATION

The following are answers to certain questions you may have regarding the Merger Agreement, the transactions contemplated thereby and the solicitation of Enzon written consents. You are encouraged to read this entire prospectus/consent solicitation/offer to exchange carefully and in its entirety because the information in this section does not provide all of the information that might be important to you. Additional important information is also contained in the Annexes and exhibits to this prospectus/solicitation statement, as well as described in the section titled “Where You Can Find More Information” in this prospectus/consent solicitation/​offer to exchange.

Q:

What is the proposed transaction?

​

A:

Viskase has agreed to merge with a wholly owned Subsidiary of Enzon under the terms of the Merger Agreement, which is further described in this prospectus/consent solicitation/offer to exchange. Subject to the satisfaction or waiver of the conditions set forth in the Merger Agreement, including the consummation of the Reverse Stock Split, the IEH Share Exchange, the Series C Exchange Offer and receipt of the requisite written consent of Enzon stockholders, Merger Sub will merge with and into Viskase, with Viskase surviving the Merger as a wholly owned Subsidiary of Enzon, and promptly thereafter, Viskase will convert into a limited liability company under Delaware law.

​

Q:

Why am I receiving this consent solicitation statement?

​

A:

Enzon is sending these materials to the holders of Enzon Common Stock at the close of business on the record date of January 29, 2026 (the “Enzon Record Date”), to seek approval of the Reverse Stock Split Proposal and the Merger Proposal. This prospectus/consent solicitation/offer to exchange provides important information about the Merger and the other transactions contemplated by the Merger Agreement, including the Reverse Stock Split, and is intended to help you make an informed decision on whether to provide your written consent.

​

Q:

What are the specific proposals to which Enzon stockholders are being asked to consent?

​

A:

Enzon stockholders are being asked to approve the following proposals:

​

1.

Reverse Stock Split Proposal — Enzon is soliciting stockholder approval for an amendment to the Enzon Charter to, among other things, effect a consolidation of the issued and outstanding shares of Enzon Common Stock, pursuant to which the shares of Enzon Common Stock would be combined and reclassified at a ratio of 1 to 100.

​

2.

Merger Proposal — Enzon is soliciting stockholder approval for the adoption of the Merger Agreement, including the Merger and the other transactions contemplated thereby.

​

Please see the sections titled “Enzon Proposal 1: Approval of the Reverse Stock Split” and “Enzon Proposal 2: Adoption of the Merger Agreement” in this prospectus/consent solicitation/offer to exchange for further information regarding the Enzon Proposals.

Q:

Why is Enzon proposing the Merger?

​

A:

The Enzon Board, acting on the unanimous recommendation of the Enzon Special Committee, unanimously determined that the Merger Agreement and the transactions contemplated thereby, including the Merger, are fair to, and in the best interests of, Enzon and the Enzon stockholders. Please see the section titled “The Merger — Enzon’s Reasons for the Merger; Recommendation of the Enzon Special Committee and the Enzon Board of Directors” in this prospectus/consent solicitation/offer to exchange for further information regarding the reasons for the Merger. Please also see the section titled “Opinion of the Enzon Special Committee’s Financial Advisor” in this prospectus/consent solicitation/​offer to exchange for information regarding the opinion, dated October 21, 2025, of the Enzon Special Committee’s financial advisor which was provided to the Enzon Special Committee (in its capacity as such) for its information and assistance in connection with its consideration of the financial terms of the Merger.

​

 

7

 

Q:

What stockholder consent is required to approve the Enzon Proposals?

​

A:

Approval of each of the Reverse Stock Split Proposal and the Merger Proposal requires the affirmative vote of the holders of a majority of the outstanding shares of Enzon Common Stock entitled to vote thereon.

​

As of the Enzon Record Date, 74,214,603 shares of Enzon Common Stock are issued and outstanding and the consent of 37,107,302 shares of the issued and outstanding shares of Enzon Common Stock are required to approve each of the Enzon Proposals, which represents a majority of the issued and outstanding shares of Enzon Common Stock. As of the Enzon Record Date, the IEH Parties are entitled to vote 36,056,636 shares of Enzon Common Stock, or approximately 48.6% of the issued and outstanding shares of Enzon Common Stock. Pursuant to the IEH Support Agreement, the IEH Parties agreed to, among other things, and subject to certain exceptions, deliver written consents with respect to all of the issued and outstanding shares of Enzon Common Stock held by the IEH Parties approving the Enzon Proposals. Accordingly, assuming delivery of written consents from the IEH Parties pursuant to the terms of the IEH Support Agreement, written consents with respect to 1,050,666 shares of Enzon Common Stock will be needed to approve the Enzon Proposals.

Q:

What is a consent, and why is Enzon requesting written consent in lieu of a meeting with stockholders?

​

A:

Enzon Stockholder Approval is a written consent/authorization approving the Enzon Proposals outlined within this prospectus/consent solicitation/offer to exchange, without the need for a formal stockholders meeting. Under the terms of the Merger Agreement, the Enzon Organizational Documents and applicable law, Enzon is not required to call any meeting of its stockholders in connection with the Enzon Stockholder Approval and may obtain stockholder approvals by written consent in lieu of a meeting by receipt of the consent of a majority of the outstanding shares of Enzon Common Stock. This prospectus/consent solicitation/offer to exchange includes the Enzon Special Committee Recommendation and the Enzon Recommendation.

​

Q:

Who is entitled to consent?

​

A:

The holders of Enzon Common Stock at the close of business on the Enzon Record Date.

​

Q:

Are any Enzon stockholders already committed to vote in favor of the Enzon Proposals?

​

A:

Concurrently with the execution of the Merger Agreement, the IEH Parties entered into the IEH Support Agreement, as amended by the IEH Support Agreement Amendment, with Enzon and Viskase, pursuant to which the IEH Parties agreed to, among other things, and subject to certain exceptions, deliver written consents approving (i) the Merger Proposal and (ii) the Reverse Stock Split Proposal. Please see the section titled “Support Agreement” in this prospectus/consent solicitation/offer to exchange for further information regarding the IEH Support Agreement.

​

Q:

Under what circumstances are the IEH Parties not required to provide approval?

​

A:

The IEH Parties are not required to consent or vote in favor of any transaction, proposal or action if an Enzon Adverse Recommendation Change has occurred and has not been rescinded.

​

Q:

Are Enzon stockholders entitled to appraisal rights?

​

A:

No. Under the DGCL, Enzon stockholders are not entitled to exercise any dissenters’ or appraisal rights in connection with the Merger. However, Viskase stockholders are entitled to appraisal rights in connection with the Merger under the DGCL. Please see the section titled “Appraisal and Dissenters’ Rights” in this prospectus/consent solicitation/offer to exchange for further information.

​

Q:

Are Viskase stockholders entitled to appraisal rights?

​

A:

Holders of Viskase Common Stock who: (i) timely submit to Viskase a proper written demand for appraisal of such shares; (ii) continuously remain the record holders or beneficial owners of such shares

​

 

8

 

through the Effective Time; and (iii) otherwise comply with the applicable procedures and requirements set forth in Section 262 of the DGCL will be entitled to have their shares appraised by the Court and receive payment in cash of the “fair value” of such shares (as determined by the Court, exclusive of any element of value arising from the accomplishment or expectation of the transaction) instead of the Merger Consideration. Any such Person awarded “fair value” for his, her or its shares by the Court would receive payment of that fair value in cash, together with interest, if any, to be paid upon the amount determined to be the “fair value” in lieu of the right to receive the Merger Consideration. It is possible that any such “fair value” as determined by the Court may be more or less than, or the same as, the Merger Consideration that such Person is entitled to receive pursuant to the Merger Agreement. Please see the section titled “Appraisal and Dissenters’ Rights” in this prospectus/consent solicitation/​offer to exchange for further information.

Q:

What happens if I do not return my written consent?

​

A:

If you are an Enzon stockholder and you do not return your written consent, it will have the same effect as delivering consents marked “WITHHOLD CONSENT” as to the Merger Proposal and the Reverse Stock Split Proposal. Because Viskase stockholders have already approved the Merger by written consent, the approval of Viskase stockholders is not being sought.

​

Q:

What if I am a Viskase stockholder, what do I need to do now?

​

A:

Viskase and Enzon urge you to read this prospectus/consent solicitation/offer to exchange carefully, including its Annexes, and to consider how the Merger affects you. Because Viskase stockholders have already approved the Merger by written consent, the approval of Viskase stockholders is not being sought.

​

Q:

What is the value of the Merger consideration that Viskase stockholders will receive in the Merger?

​

A:

At the Effective Time, each share of Viskase Common Stock issued and outstanding immediately prior to the Effective Time (other than shares of Viskase Common Stock (i) held by Viskase as treasury shares, (ii) owned by Enzon, Merger Sub or a wholly owned Subsidiary of Viskase, Enzon or Merger Sub immediately prior to the Effective Time and (iii) Dissenting Viskase Shares) will be automatically converted into the right to receive a number of shares of Enzon Common Stock equal to the Exchange Ratio (such shares, the “Merger Consideration”). As a result of the foregoing, and assuming that the Enzon Series C Preferred Stock is exchanged for Enzon Common Stock in full pursuant to the Series C Exchange Offer and the IEH Share Exchange, (i) holders of Enzon common stock immediately prior to the Effective Time are expected to own approximately 5% of the Combined Company Common Stock, (ii) holders of Enzon’s Series C Preferred Stock are expected to own approximately 40% of the Combined Company Common Stock and (iii) holders of Viskase Common Stock are expected to own 55% of the Combined Company Common Stock.

​

The exact value of the Merger Consideration payable to the holders of Viskase Common Stock will depend on the price per share of Enzon Common Stock at the Effective Time, which may be greater than, less than or the same as the price per share of Enzon Common Stock at the time of the entry into the Merger Agreement or the date of this prospectus/consent solicitation/offer to exchange. Based on the closing price of a share of Enzon Common Stock on the OTC Market on June 20, 2025, the last Trading Day prior to the date of the public announcement of the Merger, the value of Enzon Common Stock was approximately $0.08 per share. Based on the closing price of a share of Enzon Common Stock on the OTC Market on October 23, 2025, the last Trading Day prior to the public announcement of the Merger Agreement Amendment, the value of Enzon Common Stock was approximately $0.08 per share. As of January 27, 2026, the last Trading Day prior to the date of this prospectus/consent solicitation/offer to exchange, the value of Enzon Common Stock was approximately $0.0672 per share. However, as noted above, the prices at the Effective Time may be greater than, less than or the same as such price quotations.

 

9

 

Q:

What is the Exchange Ratio?

​

A:

Under the Exchange Ratio mechanics, the Exchanged Viskase Shares will be automatically converted into the right to receive a number of shares of Enzon Common Stock equal to (i) the number of shares of Enzon Common Stock issued and outstanding as of immediately prior to the Effective Time (after giving effect to each of the Reverse Stock Split, the IEH Share Exchange and the shares of Enzon Common Stock issued pursuant to the Series C Exchange Offer) (such number of shares of Enzon Common Stock, the “Pre-Exchange Enzon Shares”), divided by 0.45, minus (ii) the Pre-Exchange Enzon Shares, divided by (iii) the number of Exchanged Viskase Shares (the “Exchange Ratio”).

​

Q:

What is the IEH Share Exchange?

​

A:

Pursuant to and subject to the terms of the IEH Support Agreement, prior to the Effective Time, the IEH Parties agreed to, among other things, deliver to Enzon each share of Enzon Series C Preferred Stock Beneficially Owned by the IEH Parties in exchange for a number of shares of Enzon Common Stock. Specifically, IEH has agreed to exchange its Enzon Series C Preferred Stock for a number of shares of Enzon Common Stock equal to (i) the aggregate Liquidation Preference of such shares of Enzon Series C Preferred Stock, divided by (ii) the Enzon 20-Day VWAP.

​

Q:

How does the Enzon Common Stock consideration compare to the market price of Viskase Common Stock?

​

A:

The value of Enzon Common Stock was approximately $0.08 per share on the OTC Market on June 20, 2025, the last Trading Day prior to the date of the public announcement of the Merger. On June 20, 2025, the closing price of a share of Viskase Common Stock on the OTC Market was $1.00 per share.

​

The value of Enzon Common Stock was approximately $0.08 per share on the OTC Market on October 23, 2025, the last Trading Day prior to the date of the public announcement of the Merger Agreement Amendment. On October 23, 2025, the closing price of a share of Viskase Common Stock on the OTC Market was $1.21 per share.

The value of Enzon Common Stock was approximately $0.0672 per share on the OTC Market on January 27, 2026, the last Trading Day prior to the date of this prospectus/consent solicitation/offer to exchange.

Changes in the market price of shares of Enzon Common Stock prior to the Closing of the Merger will affect the value of the stock consideration. Accordingly, we urge you to obtain the latest market quotations for shares of Enzon Common Stock prior to submitting your written consent. Shares of Enzon Stock are currently traded on the OTC Market under the symbol “ENZN,” and shares of Viskase Common Stock are currently traded on the OTC Market under the symbol “VKSC.”

Q:

Will any fractional shares of Enzon Common Stock be issued in connection with the Merger or Reverse Stock Split?

​

A:

No fractional shares of Enzon Common Stock will be issued upon the conversion of shares of Viskase Common Stock in connection with the Merger. Each holder of Viskase Common Stock that would have otherwise been entitled to receive a fraction of a share of Enzon Common Stock (after taking into account all shares of Viskase Common Stock evidenced by the certificates and book-entry shares delivered by such holder) will receive, in lieu thereof, cash (without interest) in an amount equal to such fractional amount multiplied by the volume weighted averages of the trading prices of Enzon Common Stock on the “OTCQB” tier of the OTC (as reported by Bloomberg or, if not reported thereby, in another authoritative source mutually selected by Enzon and Viskase) on the five (5) consecutive Trading Days ending on (and including) the Trading Day that is two (2) Trading Days prior to the date of the Effective Time, rounded down to the nearest penny.

​

 

10

 

Q:

How will the Reverse Stock Split be effected?

​

A:

The combination of, and reduction in, the number of shares of outstanding Enzon Common Stock as a result of the Reverse Stock Split will occur automatically and without any action on the part of Enzon stockholders at the date and time set forth in the amendment to the Enzon Charter to effect the Reverse Stock Split following filing with the Secretary of State of the State of Delaware. Enzon intends that such time will be immediately prior to the Effective Time. Please see the section titled “Reverse Stock Split” in this prospectus/consent solicitation/offer to exchange for further information.

​

Q:

What impact will the Reverse Stock Split have?

​

A:

The Reverse Stock Split would be effected simultaneously for all outstanding shares of Enzon Common Stock. The Reverse Stock Split would affect all holders of Enzon Common Stock uniformly. No fractional shares will be issued in connection with the Reverse Stock Split. Instead, any holder of Enzon Common Stock who would have been entitled to receive a fractional share as a result of the Reverse Stock Split will have the right to receive, in lieu thereof, cash (without interest) in an amount equal to such fractional amount multiplied by the volume weighted averages of the trading prices of Enzon Common Stock on the “OTCQB” tier of the OTC (as reported by Bloomberg, or, if not reported thereby, in another authoritative source mutually selected by Enzon and Viskase) on the five (5) consecutive Trading Days ending on (and including) the Trading Day that is two (2) Trading Days prior to the date of the Effective Time, rounded down to the nearest penny. Please see section titled “Reverse Stock Split” in this prospectus/consent solicitation/offer to exchange for further information.

​

Q:

When will the Merger and the Reverse Stock Split be consummated?

​

A:

The Merger and the Reverse Stock Split are expected to be consummated in the first quarter of 2026, subject to the receipt of the required approvals from Enzon stockholders and other customary closing conditions. However, neither Enzon nor Viskase can predict the actual date on which the Merger and the Reverse Stock Split will be consummated, or whether they will be consummated, because the Merger is subject to factors beyond each company’s control. Please see the section titled “The Merger Agreement — Conditions to Completion of the Merger” in this prospectus/consent solicitation/offer to exchange for further information regarding the closing conditions to the Merger.

​

Q:

Did the Viskase stockholders already approve the Merger?

​

A:

Yes. On June 20, 2025, in connection with the execution of the Merger Agreement, the IEH Parties holding sufficient Viskase Common Stock to adopt the Merger Agreement and approve the Merger by written consent provided the Viskase Stockholder Approval under the Merger Agreement.

​

On November 11, 2025, in connection with the execution of the Merger Agreement Amendment, the IEH Parties holding sufficient Viskase Common Stock to provide the Viskase Stockholder Approval under the Merger Agreement adopted the Merger Agreement Amendment and approved the Merger, as amended, by written consent.

Q:

What are the conditions to the Closing?

​

A:

The Merger is subject to a number of closing conditions and, if these conditions are not satisfied or waived (to the extent permitted by law), the Merger will not be completed. The Closing is subject to the satisfaction or waiver of certain conditions, including, among others: (i) the required approvals by the parties’ stockholders (which approval, with respect to Viskase, was obtained on June 20, 2025 and subsequently on November 11, 2025) having been obtained; (ii) the accuracy of the parties’ representations and warranties, subject to certain “materiality” and “material adverse effect” qualifications; (iii) compliance by the parties in all material respects with their respective covenants; (iv) no law or order making the Merger illegal or otherwise prohibiting consummation of the Merger; (v) the shares of Enzon Common Stock to be issued in the Merger having been approved for listing (subject to official notice of issuance) on the OTC Market; (vi) this prospectus/consent solicitation/​offer to exchange having become effective in accordance with the provisions of the Securities Act; (vii) each of the IEH Share Exchange and the Series C Exchange Offer having been consummated and

​

 

11

 

effective; (viii) the consummation of the Reverse Stock Split; (ix) dissenters’ rights not having been exercised by Viskase stockholders representing more than three percent (3%) of the outstanding shares of Viskase Common Stock; (x) Enzon satisfying the Minimum Cash Condition; and (xi) any waiting period applicable to the Merger under the HSR Act, having expired or been terminated. Please see the section titled “The Merger Agreement — Conditions to Completion of the Merger” in this prospectus/​consent solicitation/offer to exchange for further information regarding the closing conditions to the Merger.

Q:

What effect will the Merger have on Enzon, Viskase and Enzon Common Stock?

​

A

Following the consummation of the Merger, it is anticipated that the Combined Company will operate under the name “Viskase Holdings, Inc.” and will be quoted on the OTCQB tier of the OTC. Viskase has agreed to take all actions necessary to remove the Viskase Common Stock from quotation on OTC, effective as of the Effective Time. As such, if the Merger is completed, shares of Viskase Common Stock will no longer be publicly traded and will be removed from quotation on the OTC.

​

As a result of the Merger, and assuming that the Enzon Series C Preferred Stock is exchanged for Enzon Common Stock in full pursuant to the Series C Exchange Offer and the IEH Share Exchange, (i) holders of Enzon Common Stock immediately prior to the Effective Time are expected to own approximately 5% of the Combined Company Common Stock, (ii) holders of Enzon Series C Preferred Stock are expected to own approximately 40% of the Combined Company Common Stock and (iii) holders of Viskase Common Stock are expected to own 55% of the Combined Company Common Stock.

Q:

Will Viskase stockholders be able to trade Enzon Common Stock that they receive pursuant to the Merger?

​

A:

Yes. The Enzon Common Stock issued pursuant to the Merger will be registered under the Exchange Act and is expected to be quoted on the OTCQB tier of the OTC Market under the symbol “VKSC”.

​

Q:

Who will serve as the directors and senior officers of the Combined Company following the Merger?

​

A:

The Chief Executive Officer of the Combined Company will be Thomas D. Davis, who is currently the Chief Executive Officer of Viskase. The Board of Directors of the Combined Company will consist of current Enzon directors, Jordan Bleznick and Randolph C. Read, together with Robert Flint, Colin Kwak, Dustin DeMaria, Peter K. Shea and Kenneth Shea.

​

Q:

Do any of Enzon’s or Viskase’s executive officers or directors have interests in the Merger that may be different from, or in addition to, those of the Enzon stockholders or the Viskase stockholders?

​

A:

Yes. Some of the executive officers and directors have interests in the Merger that may be different from, or in addition to, the interests of the Enzon stockholders and the Viskase stockholders, respectively. Please see the section titled “Interests of Executive Officers and Directors in the Merger” in this prospectus/consent solicitation/offer to exchange for further information. The members of the Enzon Board and the Enzon Special Committee were aware of and considered these interests, among other matters, in evaluating the Merger Agreement and the Merger, and in unanimously recommending that Enzon stockholders approve the Merger Proposal.

​

Q:

Why did the Enzon Board establish the Enzon Special Committee?

​

A:

As of the Enzon Record Date, IEH — through its control of the IEH Parties — Beneficially Owns approximately (i) 48.6% of the issued and outstanding shares of Enzon Common Stock, (ii) 98.2% of the issued and outstanding shares of Enzon Series C Preferred Stock and (iii) 93.97% of the issued and outstanding shares of Viskase Common Stock. Given the significant ownership of the IEH Parties in both Enzon and Viskase, and the potential for conflicts of interest, the Enzon Board established the Enzon Special Committee of independent and disinterested directors to, among other things, analyze, evaluate and oversee a potential transaction with Viskase. The Enzon Board determined that each

​

 

12

 

member of the Enzon Special Committee satisfied the applicable criteria for being a “disinterested director” ​(as defined in Section 144(e)(4) of the DGCL).

Q:

What are the recommendations of the Enzon Special Committee and the Enzon Board of Directors?

​

A:

The Enzon Special Committee unanimously, among other things, (i) determined that the Merger Agreement and the transactions contemplated thereby are fair to, and in the best interests of, Enzon and its stockholders, without regard to the IEH Parties, and (ii) recommended that the Enzon Board (A) approve the Merger Agreement and the transactions contemplated thereby, including the Reverse Stock Split and (B) recommend that the Enzon stockholders entitled to vote thereon approve the Reverse Stock Split Proposal and the Merger Proposal. Upon the unanimous recommendation of the Enzon Special Committee, the Enzon Board unanimously, among other things, (1) determined that the Merger Agreement and the transactions contemplated thereby are fair to, and in the best interests of, Enzon and its stockholders, (2) approved the Merger Agreement and the transactions contemplated thereby, including the Reverse Stock Split and (3) recommended that the holders of Enzon Common Stock entitled to vote thereon approve the Reverse Stock Split Proposal and the Merger Proposal.

​

Q:

Did the Viskase Board establish an independent special committee?

​

A:

Yes, the Viskase Board established a special committee consisting only of independent and disinterested directors that the Viskase Board determined to be disinterested directors within the meaning of the DGCL. All directors on the Viskase Special Committee, with the exception of one director who was unable to attend the meeting at which such determinations took place, (i) determined that the Merger Agreement and the transactions contemplated thereby are fair to, and in the best interests of Viskase and its stockholders, without regard to the IEH Parties and (ii) declared it advisable that Viskase enter into the Merger Agreement and consummate the transactions contemplated thereby. Upon the unanimous recommendation of the Viskase Special Committee, the Viskase Board (A) determined that the Merger Agreement and the transactions contemplated thereby are fair to, and in the best interests of Viskase and Viskase’s stockholders, without regard to the IEH Parties, and declared it advisable, that Viskase enter into the Merger Agreement and consummate the transactions contemplated thereby, (B) adopted resolutions approving and declaring the advisability of the Merger Agreement and the consummation of the transactions contemplated thereby, including the Merger, (C) adopted resolutions recommending that the stockholders of Viskase entitled to vote adopt the Merger Agreement and (D) directed that the Merger Agreement and the transactions contemplated thereby be submitted to the stockholders of Viskase entitled to vote for adoption.

​

Q:

What governmental/regulatory approvals are required for the Merger?

​

A:

Under the HSR Act, the Merger cannot be completed until Enzon and Viskase file a Notification and Report Form with the FTC and the DOJ and the applicable waiting period has expired or been terminated. The parties filed a Notification and Report Form with the FTC and the DOJ on June 30, 2025. The FTC granted early termination of the applicable waiting period to Enzon and Viskase on July 15, 2025. However, the DOJ, the FTC and others may still challenge the Merger on antitrust grounds after the termination of the waiting period. At any time before or after the completion of the Merger, any of the DOJ, the FTC or another Person could take action under the antitrust laws as it deems necessary or desirable in the public interest, including, without limitation, seeking to enjoin the consummation of the Merger, conditionally approve the Merger upon the divestiture of assets of Enzon or Viskase, subject the consummation of the Merger to regulatory conditions or seek other remedies. Enzon and Viskase cannot assure you that a challenge to the Merger will not be made or that, if a challenge is made, it will not succeed. Please see the section titled “HSR Act Filing” in this prospectus/​consent solicitation/offer to exchange for further information regarding the HSR Act filing.

​

Q:

Are there any risks that the Enzon stockholders should consider in deciding whether to vote on the Enzon Proposals?

​

A:

Yes. Before making any decision on whether and how to vote, Enzon stockholders are urged to read carefully and in its entirety the information contained in the section titled “Risk Factors” in this prospectus/consent solicitation/offer to exchange.

​

 

13

 

Q

What are the material U.S. federal income tax consequences of the Merger to the Enzon stockholders?

​

A:

As no U.S. holder of Enzon Stock will transfer or exchange any Enzon Stock pursuant to the Merger, a U.S. Holder of Enzon Stock will not recognize any gain or loss pursuant to the Merger. Please see the section titled “Material U.S. Federal Income Tax Consequences — U.S Federal Income Tax Consequences of the Merger” in this prospectus/consent solicitation/offer to exchange for further information regarding the U.S. federal income tax consequences of the Merger.

​

Q:

What are the material U.S. federal income tax consequences of the Merger to the Viskase stockholders?

​

A:

The parties intend that the Merger, together with the conversion of Viskase into a limited liability company, qualifies as a “reorganization” within the meaning of Section 368(a) of the Code. Assuming the Merger so qualifies, U.S. Holders (as defined in “Material U.S. Federal Income Tax Consequences” of this prospectus/consent solicitation/offer to exchange) of Viskase Common Stock generally will not recognize gain or loss as a result of the Merger, which for U.S. federal income tax purposes would be treated as a deemed exchange of Viskase Common Stock for Enzon Common Stock. A U.S. Holder’s aggregate tax basis in the Enzon Common Stock received pursuant to the Merger will equal the U.S. Holder’s aggregate tax basis in the Viskase Common Stock exchanged therefor. However, U.S. Holders of Viskase Common Stock may recognize gain or loss on any cash received instead of a fractional share of Enzon Common Stock that such U.S. Holder would otherwise be entitled to receive.

​

For further information, see “Material U.S. Federal Income Tax Consequences —  Material U.S. Federal Income Tax Consequences of the Merger” and “Material U.S. Federal Income Tax Consequences — Treatment of Cash in Lieu of Fractional Shares”.

The U.S. federal income tax consequences described above may not apply to all holders of Viskase Common Stock. The tax consequences to a holder of Viskase Common Stock will depend on such holder’s individual situation. Accordingly, we strongly urge each holder of Viskase Common Stock to consult their own tax advisor to determine the particular tax consequences of the Merger to them.

Q:

What are the material U.S. federal income tax consequences of the Reverse Stock Split?

​

A:

Enzon intends that the Reverse Stock Split qualifies as a “recapitalization” within the meaning of Section 368(a)(1)(E) of the Code and/or an exchange under Section 1036 of the Code. Assuming the Reverse Stock Split so qualifies, and subject to special rules that would apply to the receipt of cash in lieu of a fractional share of Enzon Common Stock, U.S. Holders (as defined in “Material U.S. Federal Income Tax Consequences” of this prospectus/consent solicitation/offer to exchange) of Enzon Common Stock generally should not recognize gain or loss as a result of the Reverse Stock Split for U.S. federal income tax purposes. Please see the section titled “Material U.S. Federal Income Tax Consequences — U.S. Federal Income Tax Consequences of the Reverse Stock Split” in this prospectus/​consent solicitation/offer to exchange for further information regarding the U.S. federal income tax consequences of the Reverse Stock Split. Each holder of Enzon Common Stock should consult its own tax advisor as to the specific tax consequences to such Enzon stockholder in light of its personal facts and circumstances.

​

Q:

What happens if the Merger is not consummated?

​

A:

If the Merger is not consummated, the actions contemplated by the Reverse Stock Split Proposal will not be effected, the Series C Exchange Offer and the IEH Share Exchange will not be effected and the holders of Viskase Common Stock will not receive the Merger Consideration in exchange for their shares of Viskase Common Stock. Instead, Enzon and Viskase will remain separate companies and Enzon Common Stock and Viskase Common Stock will continue to be quoted and traded on the “OTCQB” tier of the OTC.

​

Under the terms of the Merger Agreement, Enzon may be required to pay Viskase a termination fee if the Merger Agreement is terminated under certain circumstances, including if Enzon terminates the Merger Agreement to enter into a definitive agreement with respect to an Enzon Superior Proposal.

 

14

 

Please see the section titled “The Merger Agreement — Effect of Termination; Termination Fee” in this prospectus/consent solicitation/offer to exchange for further information regarding circumstances under which such a termination fee may be payable.

Q:

What do I need to do now?

​

A:

After carefully reading and considering the information contained in this prospectus/consent solicitation/​offer to exchange, please return your written consent as soon as possible in accordance with the instructions provided in this prospectus/consent solicitation/offer to exchange or, if you hold your shares through a brokerage firm, bank or other nominee, on the instruction card provided by the brokerage firm, bank or nominee.

​

Q:

If my shares of Enzon Common Stock are held in “street name,” will my brokerage firm, bank or other nominee consent for me?

​

A:

No. If your shares of Enzon Common Stock are held in “street name,” you must instruct your brokerage firm, bank or other nominee whether you consent to or withhold consent from any particular proposal. You should follow the instructions provided by your brokerage firm, bank or other nominee.

​

Q:

What if I am a record holder of Enzon Common Stock and I return a signed written consent without indicating a decision with respect to the Enzon Proposals?

​

A:

If you are a holder of Enzon Common Stock at the close of business on the Enzon Record Date and you return a signed written consent without indicating a decision with respect to the Enzon Proposals, such written consent will be treated as an approval of the Enzon Proposals.

​

Q:

How do I return my written consent?

​

A:

If you are a holder of Enzon Common Stock at the close of business on the Enzon Record Date, and after carefully reading and considering the information contained in this prospectus/consent solicitation/​offer to exchange, you wish to return your written consent, please complete, date and sign the enclosed written consent and deliver your executed consent to Enzon c/o Continental Stock Transfer & Trust Company, 1 State Street Plaza, 30th Floor, New York, New York 10004. Enzon recommends that you also email a .pdf copy of your written consent to Enzon’s consent solicitor, HKL & Co., LLC (“HKL”), at enzn@hklco.com.

​

If you are a beneficial owner and hold your shares in “street name” through a brokerage firm, bank or other nominee, you will receive separate instructions from such brokerage firm, bank or other nominee describing how to submit your written consent. Please check with your brokerage firm, bank or other nominee and follow the consent instructions provided by your brokerage firm, bank or other nominee with these materials. Enzon will not be holding a stockholders’ meeting to consider the Merger Proposal or the Reverse Stock Split Proposal and therefore, you will be unable to vote in person by attending a stockholders’ meeting.

Q:

Should I send my stock certificate to Enzon now?

​

A:

No. As soon as practicable after the Reverse Stock Split Effective Time, Enzon’s transfer agent, Continental Stock Transfer & Trust Company, acting as Enzon’s “exchange agent” for purposes of implementing the exchange of stock certificates, will mail each holder of Enzon Common Stock of record a transmittal form accompanied by instructions specifying other details of the exchange. Upon receipt of the transmittal form, each stockholder should surrender the certificates representing Enzon Common Stock in accordance with the applicable instructions. Each holder who surrenders certificates will receive new certificates representing the whole number of shares of Enzon Common Stock that he, she or it holds as a result of the Reverse Stock Split. New certificates will not be issued to a stockholder until the stockholder has surrendered his, her or its outstanding certificate(s) and submitted with the properly completed and executed transmittal form to the exchange agent.

​

Q:

What is the deadline for Enzon stockholders to submit written consents?

​

A:

Enzon has set 5:00 p.m., Eastern Time, on February 27, 2026, as the Enzon consent deadline. Enzon reserves the right to extend the Enzon consent deadline beyond February 27, 2026. Any such extension

​

 

15

 

may be made without notice to Enzon stockholders. Once a sufficient number of consents to adopt each of the Enzon Proposals has been received, the consent solicitation will conclude. Viskase stockholders are not being requested to return written consents.

Q:

What happens if I sell my shares of Enzon Common Stock after the Enzon Record Date but before submitting my written consent?

​

A:

If you sell or otherwise transfer your shares of Enzon Common Stock after the Enzon Record Date but before submitting your written consent, you will retain your right to execute the written consent with respect to the Enzon Proposals. However, you will not have the right to participate in the Merger and the Reverse Stock Split. In order to participate in the Merger and the Reverse Stock Split, you must hold your Enzon Common Stock through the completion of the Merger.

​

Q:

Can I change or revoke my written consent?

​

A:

Yes. If you are a record holder on the record date of shares of Enzon Common Stock, you may change or revoke your consent to the Enzon Proposals at any time before the consents of a sufficient number of shares to approve and adopt such proposal have been filed with the Secretary of Enzon. If you wish to change or revoke your consent before that time, you may do so by sending in a new written consent with a later date by one of the means described in the section titled “Enzon Solicitation of Written Consent” in this prospectus/consent solicitation/offer to exchange delivering a notice of revocation to the Secretary of Enzon.

​

Q:

Where can I find the results of the solicitation of Enzon written consents?

​

A:

In addition to any other notifications that may be required by applicable law, Enzon intends to file the final results of its solicitation of written consents with the SEC on a Current Report on Form 8-K.

​

Q:

Whom should I contact if I have any questions?

​

A:

If you have questions about the Merger or the solicitation of Enzon written consents, or if you need to obtain copies of this prospectus/consent solicitation/offer to exchange or other documents incorporated by reference into this prospectus/consent solicitation/offer to exchange, you may contact the consent solicitor of Enzon, whose contact information is as follows:

​

HKL & Co., LLC
3 Columbus Circle, 15FL
New York, New York 10019
Banks and Brokerage Firms Please Call Collect: (212) 468-5380
All Others Call Toll-Free: (800) 326-5997
Email: enzn@hklco.com

 

16

 

QUESTIONS AND ANSWERS ABOUT THE SERIES C EXCHANGE OFFER

The following are answers to certain questions that Enzon stockholders may have regarding the Series C Exchange Offer. The following description does not purport to be complete. You are encouraged to read this entire prospectus/consent solicitation/offer to exchange carefully, including the annexes, and the Schedule TO, as each may be amended or supplemented from time to time, and other relevant documents filed by Enzon with the SEC, because the information in this section does not provide all of the information that might be important to you.

Q:

What is the Series C Exchange Offer?

​

A:

Under the terms of the Merger Agreement, Enzon is required to use commercially reasonable efforts to commence an exchange offer no less than twenty-five (25) business days prior to the Closing, pursuant to which Enzon will offer to each holder of Enzon Series C Preferred Stock the right to exchange a number of shares of Enzon Common Stock for each share of Enzon Series C Preferred Stock equal to (i) the aggregate Liquidation Preference of each share of Enzon Series C Preferred Stock, divided by (ii) the Enzon 20-Day VWAP. The consummation of the Merger is conditioned on the consummation of the Series C Exchange Offer. The IEH Parties have agreed not to participate in the Series C Exchange Offer and, instead, effectuate the IEH Share Exchange. Please see the section titled “Series C Exchange Offer” in this prospectus/consent solicitation/offer to exchange for further information regarding the Series C Exchange Offer.

​

Q:

Why is Enzon making the Series C Exchange Offer?

​

A:

In connection with the proposed Merger, Enzon intends to convert outstanding shares of its Series C Preferred Stock into shares of Enzon Stock through the Series C Exchange Offer. The IEH Parties, who collectively hold 39,277 shares of Enzon Series C Preferred Stock — representing approximately 98.2% of the total outstanding Enzon Series C Preferred Stock — have already committed not to participate in the Series C Exchange Offer, and instead to exchange their shares pursuant to the IEH Support Agreement. The Series C Exchange Offer will proceed even if other Series C holders do not participate. The Series C Exchange Offer is based on a formula that includes a volume-weighted average price of Enzon Common Stock, which may not reflect the fair market value of the Series C Preferred Stock or its Liquidation Preference. Under the terms of the Enzon Series C Preferred Stock, following the Merger, Enzon may, and at this time intends to, redeem any outstanding shares of Enzon Series C Preferred Stock for a cash amount equal to the aggregate Liquidation Preference of such shares.

​

Q:

Who is entitled to participate in the Series C Exchange Offer?

​

A:

Any U.S. holder of Enzon Series C Preferred Stock may participate in the Series C Exchange Offer. Non-U.S. stockholders should consult their advisors in considering whether they may participate in this Series C Exchange Offer in accordance with the laws of their home countries and, if they participate, whether there are any restrictions or limitations on transactions in the shares of Enzon Common Stock or Enzon Series C Preferred Stock that that may apply in their home countries.

​

An Enzon stockholder’s decision whether to participate in the Series C Exchange Offer and to exchange his, her or its shares of Enzon Series C Preferred Stock for shares of Enzon Common Stock, however, will involve risks, including, but not limited to, termination, cancellation or delay of the Series C Exchange Offer and waiver of conditions related to the Series C Exchange Offer. Please see the section titled “Risk Factors — Risk Factors Related to the Series C Exchange Offer,” in this prospectus/​consent solicitation/offer to exchange for further information regarding the risk factors as well as the other risk factors set forth in the section titled “Risk Factors,” in this prospectus/consent solicitation/​offer to exchange, along with all of the other information provided or referred to in this prospectus/​consent solicitation/offer to exchange, before deciding whether to participate in the Series C Exchange Offer.

 

17

 

Q:

What are the key terms of the Enzon Common Stock?

​

A:

The key terms of the Enzon Common Stock are set forth below:

​

Authorized Shares

There are currently 170,000,000 authorized shares of Enzon Common Stock.

Voting Rights

Each holder of Enzon Common Stock is entitled to one (1) vote per share on all matters submitted to a vote of stockholders. A matter submitted for stockholder action is approved if a majority of the votes cast at such meeting by the holders of Enzon 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 any applicable law or regulation, the rights of any authorized series of preferred stock or the Enzon Organizational Documents. 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 Enzon Common Stock.

Other than a contested election where directors are elected by a plurality vote, a director nominee is elected if the votes cast “for” such nominee’s election exceed the votes cast “against” such nominee’s election.

Quorum

The holders of one-third of the shares of stock entitled to vote at any meeting of the Enzon stockholders, present in Person or represented by proxy, constitutes a quorum at all meetings of the Enzon stockholders for the transaction of business.

Stockholder Action by Written Consent

Enzon allows any action which could be taken at any annual or special meeting of Enzon stockholders to be taken without a meeting, without prior notice and without a vote, if a consent or consents in writing, setting forth the action so taken, is signed by the holders of outstanding stock entitled to vote thereon having not less than the minimum number of votes that would be necessary to authorize or take such action at a meeting at which all shares entitled to vote thereon were present and voted.

Special Meetings

Enzon allows special meetings of the Enzon stockholders to be called at any time by the Enzon Board, the President or the Secretary.

Please see the section titled “The Series C Exchange Offer — Comparison of Enzon Series C Preferred Stock and Enzon Common Stock” in this prospectus/consent solicitation/offer to exchange for further information regarding the terms of the Enzon Common Stock relative to the Enzon Series C Preferred Stock.

Q:

What will the Enzon Series C Preferred stockholders receive in the Series C Exchange Offer? Will such stockholders have to pay any fees or commissions?

​

A:

In the Series C Exchange Offer, stockholders will have the right to exchange each of their shares of Enzon Series C Preferred Stock for shares of Enzon Common Stock.

​

If you are the record owner of your shares of Enzon Series C Preferred Stock and you tender your shares directly to Continental Stock Transfer & Trust Company, which we refer to as the “Exchange Agent,” you will not have to pay brokerage fees, commissions or similar expenses. If you own shares of Enzon Series C Preferred Stock through a brokerage firm, bank or other nominee and your brokerage firm, bank or other nominee tenders your shares of Enzon Series C Preferred Stock on your behalf, your brokerage firm, bank or other nominee may charge you a fee for doing so. You should consult your

 

18

 

brokerage firm, bank or other nominee to determine whether any charges will apply. Enzon will only deliver whole shares of Enzon Common Stock in the Series C Exchange Offer.

Q:

How will shares of Enzon Series C Preferred Stock that are not tendered in the Series C Exchange Offer be affected after the Merger?

​

A:

Non-tendering holders of shares of Enzon Series C Preferred Stock will continue to hold shares of Enzon Series C Preferred Stock following the Closing. Under the terms of the Enzon Series C Preferred Stock, following the Merger, Enzon may, and at this time intends to, redeem any outstanding shares of Enzon Series C Preferred Stock for a cash amount equal to the aggregate Liquidation Preference of such shares. Accordingly, even if a holder of Series C Preferred Stock does not participate in the Series C Exchange Offer, Enzon may, and currently intends to, redeem such holder’s shares of Series C Preferred Stock after the consummation of the Merger.

​

Q:

Are there risks associated with the Series C Exchange Offer that I should consider?

​

A:

Yes. Please see the section titled “Risk Factors — Risk Factors Related to the Series C Exchange Offer” in this prospectus/consent solicitation/offer to exchange for further information regarding the risks related to the Series C Exchange Offer, as well as the other risks included in the section titled “Risk Factors” in this prospectus/consent solicitation/offer to exchange.

​

Q:

When is the Series C Exchange Offer expected to be completed?

​

A:

Enzon expects to complete the Series C Exchange Offer as soon as reasonably practicable before the completion of the Merger.

​

Q:

Will the Series C Exchange Offer be completed if the Merger is not consummated?

​

A:

No. The Series C Exchange Offer is not expected to be completed if the Merger is not consummated. In that case, the shares of Enzon Series C Preferred Stock will remain outstanding in accordance with their current terms.

​

Q:

What are the anticipated U.S. federal income tax consequences of the Series C Exchange Offer to holders of shares of Enzon Series C Preferred Stock?

​

A:

Enzon intends that an exchange of Series C Preferred Stock for Enzon Common Stock pursuant to the Series C Exchange Offer qualifies as a “recapitalization” within the meaning of Section 368(a)(1)(E) of the Code. Assuming the exchange so qualifies, for U.S. federal income tax purposes, a U.S. Holder (as defined in the section titled “Material U.S. Federal Income Tax Consequences” in this prospectus/​consent solicitation/offer to exchange) of the Series C Preferred Stock generally should not recognize gain or loss upon the exchange of its Series C Preferred Stock for Enzon Common Stock pursuant to the Series C Exchange Offer, provided that no part of the exchange consideration is attributable to accumulated but unpaid dividends on the Series C Preferred Stock. With respect to the portion of a U.S. Holder’s Series C Preferred Stock that is attributable to accumulated but unpaid distributions on the Series C Preferred Stock, the U.S. Holder should generally recognize income in an amount that is deemed to be a taxable stock distribution under Sections 305(b) and (c) of the Code. Please see the section titled “Material U.S. Federal Income Tax Consequences — U.S. Federal Income Tax Consequences of the Series C Exchange Offer” in this prospectus/consent solicitation/offer to exchange for further information regarding the U.S. federal income tax consequences of the Series C Exchange Offer.

​

Q:

Are Enzon’s stockholders entitled to appraisal rights in connection with the Series C Exchange Offer?

​

A:

No. Enzon’s stockholders are not entitled to exercise appraisal rights in connection with the Series C Exchange Offer.

​

 

19

 

Q:

How long do Enzon stockholders have to decide whether to exchange their shares of Enzon Series C Preferred Stock for shares of Enzon Common Stock?

​

A:

You will have until one minute after 11:59 p.m., Eastern Time, on February 27, 2026, unless the Series C Exchange Offer is extended in Enzon’s sole discretion (such time, or such later time to which the Series C Exchange Offer has been so extended, is referred to as the “Series C Exchange Time”). If Enzon makes a material change in the terms of the Series C Exchange Offer or the information concerning the Series C Exchange Offer, or if it waives a material condition to the Series C Exchange Offer, Enzon will disseminate additional Series C Exchange Offer materials and extend the Series C Exchange Offer by five (5) or ten (10) business days, to the extent required by Rules 14d-4(d), 14d-6(c) and 14e-1 under the Exchange Act.

​

In all cases, Enzon will exchange shares validly tendered and accepted for exchange pursuant to the Series C Exchange Offer only after timely receipt by the Exchange Agent of shares (or timely confirmation of a book-entry transfer of such shares into the Exchange Agent’s account at DTC as described elsewhere in this prospectus/consent solicitation/offer to exchange), a properly completed and duly executed letter of transmittal (or an “agent’s message” in connection with a book-entry transfer) and any other required documents.

Q:

What is the process for exchanging shares of Enzon Series C Preferred Stock?

​

A:

For you to validly tender your shares of Enzon Series C Preferred Stock pursuant to the Series C Exchange Offer, prior to the Series C Exchange Time:

​

•

If your shares are directly registered in your own name in Enzon’s stockholders register, including if you are a record holder and you hold shares in book-entry form on the books of Enzon’s transfer agent, the following must be received by the Exchange Agent at one of its addresses set forth in the letter of transmittal prior to the Series C Exchange Time: (i) the letter of transmittal, properly completed and duly executed and (ii) any other documents required by the letter of transmittal.

​

•

If your shares are held in “street” name and are being tendered by book-entry transfer into an account maintained at the DTC, the following must be received by the Exchange Agent in connection with the Series C Exchange Offer, at one of its addresses set forth in the letter of transmittal prior to the Series C Exchange Time: (i) the letter of transmittal, properly completed and duly executed, or an “agent’s message,” ​(ii) a book-entry confirmation from DTC and (iii) any other required documents.

​

•

If you hold your shares through a brokerage firm, bank or other nominee, you must contact your brokerage firm, bank or other nominee and give instructions that your shares be tendered.

​

Please see the section titled “The Series C Exchange Offer — Procedures for Tendering Shares of Enzon Series C Preferred Stock” in this prospectus/consent solicitation/offer to exchange for further information.

Q:

Until what time can the shares of Enzon Series C Preferred Stock tendered pursuant to the Series C Exchange Offer be withdrawn and when do you expect the Series C Exchange Offer to be completed?

​

A:

An Enzon stockholder may properly withdraw shares of Enzon Series C Preferred Stock tendered pursuant to the Series C Exchange Offer at any time prior to the Series C Exchange Time. On and after the Series C Exchange Time, Enzon stockholders that have tendered their shares pursuant to the Series C Exchange Offer will no longer be able to withdraw their shares, and tenders of shares of Enzon Series C Preferred Stock made pursuant to the Series C Exchange Offer will be irrevocable; provided that, if Enzon has not yet accepted shares of Enzon Series C Preferred Stock tendered for exchange, any Enzon stockholder may withdraw its tendered shares after the 60th day following commencement of the Series C Exchange Offer pursuant to Section 14(d)(5) of the Exchange Act.

​

As promptly as practicable following the Series C Exchange Time, Enzon will accept for exchange and, at or as promptly as practicable thereafter (calculated as set forth in Rule 14e-1(c) under the Exchange Act), deliver the Series C Exchange Offer Consideration (by delivery by Enzon of shares of Enzon

 

20

 

Common Stock to the exchange agent appointed by Enzon for the Series C Exchange Offer) for all shares of Enzon Series C Preferred Stock validly tendered and not properly withdrawn pursuant to the Series C Exchange Offer as of the Series C Exchange Time.

Q:

Who is entitled to make the final determination as to whether a share of Enzon Series C Preferred Stock is validly tendered?

​

A:

The determination of shares of Enzon Series C Preferred Stock validly tendered and not properly withdrawn pursuant to the Series C Exchange Offer shall be made in Enzon’s sole discretion.

​

Q:

What is the procedure to withdraw previously tendered shares of Enzon Series C Preferred Stock?

​

A:

To properly withdraw previously tendered shares, Enzon stockholders must instruct the Exchange Agent to arrange for the withdrawal of such shares by a written notice of withdrawal (which may be by email), which must be timely received by the Exchange Agent prior to the Series C Exchange Time at the appropriate address set forth in this prospectus/consent solicitation/offer to exchange. Any notice of withdrawal must specify the name of the Person having tendered the shares of Enzon Series C Preferred Stock to be withdrawn, the number of tendered shares of Enzon Series C Preferred Stock to be withdrawn and the name of the holder of the tendered shares of Enzon Series C Preferred Stock to be withdrawn, if different from that of the Person who tendered such shares.

​

All questions as to the form and validity (including time of receipt) of any notice of withdrawal shall be determined by Enzon, in its sole discretion, which determination shall be final and binding, subject to any judgment of any court of competent jurisdiction. No withdrawal of tendered shares of Enzon Series C Preferred Stock shall be deemed to have been properly made until all defects and irregularities have been cured or waived. None of Enzon or any of its Affiliates or assignees, the Exchange Agent or any other Person shall be under any duty to give notification of any defects or irregularities in any notice of withdrawal or incur any liability for failure to give such notification. Withdrawals of tenders of shares of Enzon Series C Preferred Stock may not be rescinded, and any shares of Enzon Series C Preferred Stock properly withdrawn shall be deemed not to have been validly tendered for purposes of the Series C Exchange Offer. However, withdrawn shares of Enzon Series C Preferred Stock may be retendered by following one of the procedures for tendering described above.

Q:

Can the Series C Exchange Offer be extended and, if so, under what circumstances?

​

A:

Enzon may extend the Series C Exchange Offer to such other date and time in Enzon’s sole discretion, and Enzon will extend the Series C Exchange Offer for any minimum period as required by the SEC applicable to the Series C Exchange Offer.

​

Q:

How will Enzon stockholders be notified if the Series C Exchange Offer is extended?

​

A:

Any extension of the Series C Exchange Offer will be followed by a public announcement of the extension no later than 9:00 a.m., Eastern Time, on the next business day after the day on which the Series C Exchange Offer was otherwise scheduled to expire.

​

Without limiting the manner in which Enzon may choose to make any public announcement, Enzon currently intends to make announcements regarding the Series C Exchange Offer by issuing a press release and making an appropriate filing with the SEC.

Q:

Who can answer my questions?

​

A:

If you have any questions about the Series C Exchange Offer or need additional copies of this prospectus/​consent solicitation/offer to exchange you should contact:

​

HKL & Co., LLC
3 Columbus Circle, 15FL
New York, New York 10019

 

21

 

Banks and Brokerage Firms Please Call Collect: (212) 468-5380
All Others Call Toll-Free: (800) 326-5997
Email: enzn@hklco.com

Q:

Where can I find more information on Enzon relating to the Series C Exchange Offer?

​

A:

You can find more information on the Series C Exchange Offer in the Schedule TO, to be filed by Enzon with the SEC following effectiveness of the Registration Statement, of which this prospectus/​consent solicitation/offer to exchange is a part. Before making any decision with respect to the Series C Exchange Offer, Enzon stockholders are encouraged to read the Schedule TO (including the prospectus, related letter of transmittal and other offer documents), as it may be amended or supplemented from time to time, and other relevant documents filed by Enzon with the SEC carefully when they become available because they will contain important information about the proposed transactions. Investors will be able to obtain free copies of the Schedule TO, as it may be amended from time to time in accordance with its terms, and other relevant documents filed by Enzon with the SEC (when they become available) at http://www.sec.gov, the SEC’s website, or free of charge by contacting Enzon at:

​

Enzon Pharmaceuticals, Inc.
20 Commerce Drive, Suite 135
Cranford, New Jersey 07016
Phone: (732) 980-4500
investor@enzon.com

 

22

 

23

 

24

 

​

25

 

​

26

 

​

27

 

28

 

29

 

30

 

​

31

 

32

 

33

 

34

 

​

​

​

Shares of Enzon Common Stock

​

​

Pro Forma Percentage Ownership

​

Shares held by legacy Viskase common stockholders

​

​

​

​

7,935,878

​

​

​

​

​

55.0%

​

​

Shares held by IEH Parties underlying Enzon Series C Preferred Stock subsequent to IEH Share Exchange

​

​

​

​

5,646,898

​

​

​

​

​

39.2%

​

​

Shares held by legacy Enzon common stockholders

​

​

​

​

742,146

​

​

​

​

​

5.1%

​

​

Shares held by non-IEH Parties underlying Enzon Series C Preferred Stock subsequent to Series C Exchange Offer

​

​

​

​

103,947

​

​

​

​

​

0.7%

​

​

Total shares of Combined Company Common Stock

​

​

​

​

14,428,869

​

​

​

​

​

100.0%

​

​

35

 

36

 

37

 

38

 

UNAUDITED PRO FORMA CONDENSED COMBINED FINANCIAL INFORMATION

Introduction

The following unaudited pro forma condensed combined financial information and accompanying notes are provided to aid you in your analysis of the financial aspects of the Merger, the securities purchase agreement (described in the “Viskase Securities Purchase Agreement” section below), and adjustments for other material events (described in the “Other Material Events” section below). The pro forma adjustments for events described below in the section “Other Material Events” are referred to herein as “Adjustments for Other Material Events.” The following information is also relevant to understanding the unaudited pro forma condensed combined financial information contained herein.

On June 20, 2025, Enzon, Merger Sub and Viskase entered into the initial Merger Agreement which was subsequently amended on October 24, 2025. Both the initial and amended Merger Agreement are collectively referred to herein as the Merger Agreement. The Merger Agreement and related agreements provide for the following:

Prior to the Effective Time the following will occur:

•

Concurrently with the execution of the initial Merger Agreement, the IEH Parties entered into the initial IEH Support Agreement with Enzon and Viskase which was subsequently amended on October 24, 2025, pursuant to which the IEH Parties agreed to, among other things, and subject to certain exceptions, deliver to Enzon each share of Enzon Series C Preferred Stock beneficially owned by the IEH Parties in exchange for a number of shares of Enzon Common Stock equal to (i) the aggregate Liquidation Preference of such shares of Enzon Series C Preferred Stock divided by (ii) the Enzon 20-Day VWAP of Enzon Common Stock. The Merger Agreement also requires that Enzon use commercially reasonable efforts to commence an exchange offer no less than twenty-five (25) business days prior to the Effective Time, pursuant to which Enzon will offer to each holder of Enzon Series C Preferred Stock to exchange a number of shares of Enzon Common Stock for each share of Enzon Series C Preferred Stock equal to (i) the aggregate Liquidation Preference of each share of Enzon Series C Preferred Stock, divided by (ii) the Enzon 20-Day VWAP as calculated pursuant to the terms of the Merger Agreement;

​

•

Enzon has agreed to file the Proposed Charter Amendment to effect the Reverse Stock Split and to change the name of Enzon from “Enzon Pharmaceuticals, Inc.” to “Viskase Holdings, Inc.” in connection with the Closing;

​

•

Effect the Reverse Stock Split of the issued and outstanding shares of Enzon Common Stock at a ratio of 1-for-100;

​

•

Consummate the Series C Exchange Offer in accordance with the terms of the Merger Agreement. Under the Series C Exchange Offer, each holder of Enzon Series C Preferred Stock, other than the IEH Parties, will be offered to exchange their shares of Enzon Series C Preferred Stock for shares of Enzon Common Stock. Holders of such shares who elect not to participate in the Series C Exchange Offer may have their shares redeemed for cash.

​

•

Enzon will use its commercially reasonable efforts to cause the shares of Combined Company Common Stock to be issued in connection with the Merger to be quoted on the OTC, subject to official notice of issuance.

​

At the Effective Time, the following will occur:

•

Merger Sub will merge with and into Viskase, with Viskase surviving the Merger as a wholly owned subsidiary of Enzon and the separate corporate existence of Merger Sub shall cease.

​

•

Each share of Viskase Common Stock issued and outstanding immediately prior to the Effective Time (other than shares of Viskase Common Stock (i) held by Viskase as treasury shares, (ii) owned by Enzon, Merger Sub or a wholly owned Subsidiary of Viskase, Enzon or Merger Sub immediately prior to the Effective Time and (iii) Dissenting Viskase Shares) will be automatically converted into the right to receive the Merger Consideration, which is comprised of Enzon Common Stock equal to the Exchange Ratio.

​

 

39

 

•

Viskase shall take all actions necessary to remove the Viskase Common Stock from quotation on the “Pink Limited” tier of the OTC.

​

Promptly after the Effective Time, the following will occur:

•

Enzon will cause Viskase, as the Surviving Company following the Merger, to be converted from a Delaware corporation into a Delaware limited liability company through a statutory conversion permitted under Delaware law, which will be renamed Viskase Companies, LLC. The corporate existence of the Surviving Company will continue unaffected and unimpaired by the conversion, except that, upon the consummation of the conversion, all of the outstanding shares of Viskase Common Stock will be converted to limited liability company interests. Because the Surviving Company will be a wholly owned Subsidiary of the Combined Company at the Effective Time, the Combined Company will be the sole member of the Surviving Company following the conversion.

​

•

The Combined Company refers to Enzon, which will be renamed Viskase Holdings, Inc. in connection with the Closing. The Combined Company remains the same legal entity as Enzon, with no changes to its authorized shares, par value or issued and outstanding shares. The designation as the Combined Company reflects the post-Merger structure, but the underlying corporate entity and share structure remain unchanged from Enzon prior to the Effective Time.

​

Exchange Ratio:

At the Effective Time, each outstanding share of Viskase Common Stock (other than shares of Viskase Common Stock (i) held by Viskase as treasury shares, (ii) owned by Enzon, Merger Sub or a wholly owned Subsidiary of Viskase, Enzon or Merger Sub immediately prior to the Effective Time and (iii) Dissenting Viskase Shares) will be automatically converted into the right to receive a number of shares of Enzon Common Stock equal to the Exchange Ratio. The Exchange Ratio is calculated as (i) the Viskase Closing Share Number divided by (ii) the number of issued and outstanding shares of Viskase Common Stock immediately prior to the Effective Time.

The tables below present the calculation of the Exchange Ratio and related calculations:

(1)

The Viskase Closing Share Number is calculated as follows, pursuant to the terms of the Merger Agreement:

​

(1)

Consists of 742,146 shares of Enzon Common Stock issued to the current holders of Enzon Common Stock following the Reverse Stock Split. The 74,214,603 shares of Enzon Common Stock outstanding immediately prior to the Closing are assumed to be adjusted using a 1 for 100 Reverse Stock Split ratio, resulting in 742,146 shares of Enzon Common Stock.

​

 

40

 

(2)

The Enzon Common Stock issued in the IEH Share Exchange and the Series C Exchange Offer is determined as follows, pursuant to the Merger Agreement and IEH Support Agreement:

​

(1)

The aggregate Liquidation Preference of Enzon Series C Preferred Stock held by IEH Parties immediately prior to the Closing Date is calculated as (A) (i) the historical Liquidation Preference of $1,102 per share as of September 30, 2025, plus (ii) the prorated 5% annual increase in the Liquidation Preference per share from October 1, 2025 through the estimated Closing Date of $23 per share (resulting in a Liquidation Preference per share of $1,125 as of the estimated Closing Date) pursuant to the Certificate of Designation of Series C Non-Convertible Redeemable Preferred Stock of Enzon, multiplied by (B) the number of shares of Enzon Series C Preferred Stock beneficially owned by non-IEH Parties.

​

(2)

Refer to Note 3(i) for the calculation of the Enzon 20-Day VWAP for the 1 for 100 Reverse Stock Split.

​

(1)

The aggregate Liquidation Preference of Enzon Series C Preferred Stock held by IEH Parties immediately prior to the Closing Date is calculated as (A) (i) the historical Liquidation Preference of $1,102 per share as of September 30, 2025, plus (ii) the prorated 5% annual increase in the Liquidation Preference per share from October 1, 2025 through the estimated Closing Date of $23 per share (resulting in a Liquidation Preference per share of $1,125 as of the estimated Closing Date) pursuant to the Certificate of Designation of Series C Non-Convertible Redeemable Preferred Stock of Enzon, multiplied by (B) the number of shares of Enzon Series C Preferred Stock beneficially owned by non-IEH Parties.

​

(2)

Refer to Note 3(i) for the calculation of the Enzon 20-Day VWAP 1 for 100 Reverse Stock Split.

​

Viskase Securities Purchase Agreement

•

In December 2025 and January 2026, Viskase entered into securities purchase agreements with AEP pursuant to which it issued and sold 43,103,450 shares of its common stock at a purchase price of $0.58 per share, resulting in aggregate cash proceeds of approximately $25.0 million.

​

Other Material Events

•

Under the terms of the Merger Agreement, Enzon is required to have Cash on Hand at the Closing of an amount that is equal to the Minimum Cash Condition, which is defined as an amount equal or greater than $40,000,000.

​

In order to determine whether the Minimum Cash Condition will be satisfied at Closing, Enzon must adjust its Cash on Hand as of September 30, 2025 to reflect its estimated Cash on Hand as of the estimated Closing Date of March 4, 2026. These adjustments include:

•

Actual and estimated interest and dividend income to be earned on Enzon’s invested cash and cash equivalents from October 1, 2025 through the estimated Closing on March 4, 2026 of $0.6 million.

​

•

Actual and estimated cash disbursements for Enzon’s general and administrative costs from October 1, 2025 through the assumed Closing on March 4, 2026 of $0.6 million plus transaction costs of $1.3 million.

​

As of the estimated Closing on March 4, 2026, Enzon estimates it will have $42.0 million of Cash on Hand, which will satisfy the Minimum Cash Condition.

•

On March 26, 2025, Viskase announced a plan to cease production in its plant in Osceola, Arkansas, with the operations ceasing effective April 30, 2025 (the “Plant Closure”) with winddown activities

​

 

41

 

continuing through June 2025. In connection with the Plant Closure, Viskase moved the equipment and personnel from the Osceola plant to existing sites to maintain a materially similar company-wide productive capacity after the Plant Closure. Viskase expects to settle the remaining $0.6 million of accrued plant restructuring costs prior to the Closing.

Additional Information Related to the Unaudited Pro Forma Condensed Combined Financial Information

The unaudited pro forma condensed combined financial information has been prepared based on Enzon’s and Viskase’s historical financial statements as adjusted to give effect to the Closing, and the events described above in the sections “Viskase Securities Purchase Agreement” and “Other Material Events.” The unaudited pro forma condensed combined balance sheet as of September 30, 2025 gives pro forma effect to the Closing as if it had occurred on September 30, 2025. The unaudited pro forma condensed combined statement of operations for the year ended December 31, 2024 reflects adjustments assuming that any adjustments that were made to the unaudited pro forma condensed combined balance sheet as of September 30, 2025 are assumed to have been made on January 1, 2024 for the purpose of adjusting the unaudited pro forma condensed combined statement of operations. The unaudited pro forma condensed combined statement of operations for the nine months ended September 30, 2025 reflects adjustments assuming that any adjustments that were made to the unaudited pro forma condensed combined balance sheet as of September 30, 2025 are assumed to have been made on January 1, 2024 for the purpose of adjusting the unaudited pro forma condensed combined statement of operations.

The unaudited pro forma condensed combined financial information has been derived from and should be read in conjunction with:

•

the accompanying notes to the unaudited pro forma condensed combined financial information;

​

•

the historical unaudited financial statements of Enzon as of and for the nine months ended September 30, 2025 and the related notes included elsewhere in this prospectus/consent solicitation/​offer to exchange;

​

•

the historical audited financial statements of Enzon as of and for the year ended December 31, 2024 and the related notes included elsewhere in this prospectus/consent solicitation/offer to exchange;

​

•

the historical unaudited financial statements of Viskase as of and for the nine months ended September 30, 2025 and the related notes included elsewhere in this prospectus/consent solicitation/​offer to exchange;

​

•

the historical audited financial statements of Viskase as of and for the year ended December 31, 2024 and the related notes included elsewhere in this prospectus/consent solicitation/offer to exchange;

​

•

other information relating to Enzon and Viskase contained in this prospectus/consent solicitation/​offer to exchange, including in the sections entitled “Enzon’s Management’s Discussion and Analysis of Financial Condition and Results of Operations,” “Viskase’s Management’s Discussion and Analysis of Financial Condition and Results of Operations,” the Annexes and other financial information relating to each of Enzon and Viskase included elsewhere in this prospectus/consent solicitation/offer to exchange.

​

The unaudited pro forma condensed combined financial information is provided for illustrative purposes only and is not necessarily indicative of what the actual results of operations and financial position would have been had the Closing and the events described above in the sections “Viskase Securities Purchase Agreement” and “Other Material Events” taken place on the dates indicated, nor are they indicative of the future consolidated results of operations or financial position of Enzon. The unaudited pro forma adjustments are based on information currently available, and assumptions and estimates underlying the unaudited pro forma adjustments are described in the accompanying notes to the unaudited pro forma condensed combined financial information. If the actual facts are different than these assumptions, the amounts and shares outstanding in the unaudited pro forma condensed combined financial information that follows will be different, and those changes could be material.

Except where the context otherwise indicates, the information concerning Enzon contained in or incorporated by reference into this unaudited pro forma condensed combined financial information has been provided by Enzon, and the information concerning Viskase contained in this unaudited pro forma condensed combined financial information has been provided by Viskase.

 

42

 

UNAUDITED PRO FORMA CONDENSED COMBINED BALANCE SHEET
AS OF SEPTEMBER 30, 2025