# EDGAR Filing Document

**Accession Number:** 0000727510
**File Stem:** 0001104659-26-008573
**Filing Date:** 2026-1
**Character Count:** 110220
**Document Hash:** 9dde25d10bddd42e88c8528964d40995
**Contains OCR:** False
**Source Format:** 

## Filing Content

## Filing Summary
**0001104659-26-008573.hdr.sgml**: 20260130

**ACCESSION NUMBER**: 0001104659-26-008573

**CONFORMED SUBMISSION TYPE**: S-4/A

**PUBLIC DOCUMENT COUNT**: 7

**FILED AS OF DATE**: 20260130

**DATE AS OF CHANGE**: 20260130

**FILER**: 

**COMPANY DATA:**
- **COMPANY CONFORMED NAME:** ENZON PHARMACEUTICALS, INC.
- **CENTRAL INDEX KEY:** 0000727510
- **STANDARD INDUSTRIAL CLASSIFICATION:** BIOLOGICAL PRODUCTS (NO DIAGNOSTIC SUBSTANCES) [2836]
- **ORGANIZATION NAME:** 03 Life Sciences
- **EIN:** 222372868
- **STATE OF INCORPORATION:** DE
- **FISCAL YEAR END:** 1231

**FILING VALUES:**
- **FORM TYPE:** S-4/A
- **SEC ACT:** 1933 Act
- **SEC FILE NUMBER:** 333-293019
- **FILM NUMBER:** 26582879

**BUSINESS ADDRESS:**
- **STREET 1:** 20 COMMERCE DRIVE, SUITE 135
- **CITY:** CRANFORD
- **STATE:** NJ
- **ZIP:** 07016
- **BUSINESS PHONE:** 732-980-4500

**MAIL ADDRESS:**
- **STREET 1:** 20 COMMERCE DRIVE, SUITE 135
- **CITY:** CRANFORD
- **STATE:** NJ
- **ZIP:** 07016

**FORMER COMPANY:**
- **FORMER CONFORMED NAME:** ENZON PHARMACEUTICALS INC
- **DATE OF NAME CHANGE:** 20060324

**FORMER COMPANY:**
- **FORMER CONFORMED NAME:** ENZON PHARMACEUTICALS  INC
- **DATE OF NAME CHANGE:** 20021211

**FORMER COMPANY:**
- **FORMER CONFORMED NAME:** ENZON PHARMACEUTICAL  INC
- **DATE OF NAME CHANGE:** 20021210

#### As filed with the U.S. Securities and Exchange Commission on January 30, 2026

#### Registration No. 333-293019

### UNITED STATES SECURITIES AND EXCHANGE COMMISSION

#### Washington, D.C. 20549

#### AMENDMENT NO. 1 TO

### FORM S-4 REGISTRATION STATEMENT

#### UNDER THE SECURITIES ACT OF 1933

### ENZON PHARMACEUTICALS, INC.
(Exact name of registrant as specified in its charter)

---

| | | |
|:---|:---|:---|
| **Delaware** <br> (State or other jurisdiction of <br> incorporation or organization)  | **2836** <br> (Primary Standard Industrial <br> Classification Code Number)  | **22-2372868** <br> (I.R.S. Employer <br> Identification No.)  |

---

#### 20 Commerce Drive, Suite 135 Cranford, New Jersey 07016 (732) 980-4500
(Address, including zip code, and telephone number, including area code, of registrant's principal executive offices)

#### Richard L. Feinstein Chief Executive Officer, Chief Financial Officer and Secretary Enzon Pharmaceuticals, Inc. 20 Commerce Drive, Suite 135 Cranford, New Jersey 07016 (732) 980-4500
(Name, address, including zip code, and telephone number, including area code, of agent for service)

#### Copies of all communications, including communications sent to agent for service, should be sent to:

---

| | | | |
|:---|:---|:---|:---|
| **Adam J. Agron <br> Evan J. Leitch <br> Brownstein Hyatt Farber <br> Schreck, LLP <br> 675 15th Street, Suite 2900 <br> Denver, Colorado 80202 <br> (303) 223-1100**  | **Todd E. Mason <br> Corby J. Baumann <br> Benjamin M. Russell <br> Thompson Hine LLP <br> 300 Madison Avenue, <br> 27th Floor <br> New York, New York 10017 <br> (212) 344-5680**  | **Joseph D. King <br> Senior Vice President, <br> General Counsel and Secretary <br> Viskase Companies, Inc. <br> 333 East Butterfield Road, Suite 400 <br> Lombard, Illinois 60148 <br> (630) 874-0700**  | **Steven Khadavi <br> Joseph Walsh <br> Troutman Pepper <br> Locke LLP <br> 875 Third Avenue <br> New York, New York 10022 <br> (212) 704-6000**  |

---

**Approximate date of commencement of proposed sale to the public**: As soon as practicable after this Registration Statement is declared effective and upon the satisfaction or waiver of all other conditions to consummation of the transactions described herein.

If the securities being registered on this form are being offered in connection with the formation of a holding company and there is compliance with General Instruction G, check the following box. ☐

If this form is filed to register additional securities for an offering pursuant to Rule 462(b) under the Securities Act of 1933, as amended (the "Securities Act"), check the following box and list the Securities Act registration statement number of the earlier effective registration statement for the same offering. ☐

If this form is a post-effective amendment filed pursuant to Rule 462(d) under the Securities Act, check the following box and list the Securities Act registration statement number of the earlier effective registration statement for the same offering. ☐

Indicate by check mark whether the registrant is a large accelerated filer, an accelerated filer, a non-accelerated filer, a smaller reporting company, or an emerging growth company. See the definitions of "large accelerated filer," "accelerated filer," "smaller reporting company" and "emerging growth company" in Rule 12b-2 of the Securities Exchange Act of 1934, as amended (the "Exchange Act").

Large accelerated filer ☐ Accelerated filer ☐ <br> Non-accelerated filer ☒ Smaller reporting company ☒ <br> Emerging growth company ☐

If an emerging growth company, indicate by check mark if the registrant has elected not to use the extended transition period for complying with any new or revised financial accounting standards provided pursuant to Section 7(a)(2)(B) of the Securities Act. ☐

If applicable, place an X in the box to designate the appropriate rule provision relied upon in conducting this transaction:

Exchange Act Rule 13e-4(i) (Cross-Border Issuer Tender Offer) ☐

Exchange Act Rule 14d-1(d) (Cross-Border Third-Party Tender Offer) ☐

 **THE REGISTRANT HEREBY AMENDS THIS REGISTRATION STATEMENT ON SUCH DATE OR DATES AS MAY BE NECESSARY TO DELAY ITS EFFECTIVE DATE UNTIL THE REGISTRANT SHALL FILE A FURTHER AMENDMENT WHICH SPECIFICALLY STATES THAT THIS REGISTRATION STATEMENT SHALL THEREAFTER BECOME EFFECTIVE IN ACCORDANCE WITH SECTION 8(A) OF THE SECURITIES ACT OF 1933, AS AMENDED, OR UNTIL THE REGISTRATION STATEMENT SHALL BECOME EFFECTIVE ON SUCH DATE AS THE SECURITIES AND EXCHANGE COMMISSION, ACTING PURSUANT TO SAID SECTION 8(A), MAY DETERMINE.** 

------

#### EXPLANATORY NOTE
Enzon Pharmaceuticals, Inc. is filing this Amendment No. 1 to its Registration Statement on Form S-4 (File No. 333-293019) (the "Registration Statement") as an exhibits-only filing. Accordingly, this amendment consists only of the facing page, this explanatory note, Item 21 of Part II of the Registration Statement, the signature page to the Registration Statement and the filed exhibits. The remainder of the Registration Statement is unchanged and has therefore been omitted.

#### Item 21. Exhibits and Financial Statement Schedules

#### EXHIBIT INDEX

---

| | |
|:---|:---|
| **Exhibit <br> Number**  | **Exhibit Description**  |
| &nbsp;&nbsp; 2.1† | [Agreement and Plan of Merger, dated as of June 20, 2025, by and between Enzon Pharmaceuticals, Inc., EPSC Acquisition Corp., and Viskase Companies, Inc. (included as Annex A to the prospectus/consent solicitation/offer to exchange).](https://www.sec.gov/ix?doc=/Archives/edgar/data/727510/000110465926007463/enzn-20250930xs4.htm#AnnexA_201397) |
| &nbsp;&nbsp; 2.2† | [First Amendment to Agreement and Plan of Merger, dated as of October 24, 2025, by and between Enzon Pharmaceuticals, Inc., EPSC Acquisition Corp., and Viskase Companies, Inc. (included as Annex A-1 to the prospectus/consent solicitation/offer to exchange).](https://www.sec.gov/ix?doc=/Archives/edgar/data/727510/000110465926007463/enzn-20250930xs4.htm#AnnexA1_225933) |
| &nbsp;&nbsp; 3.1 | [Amended and Restated Certificate of Incorporation dated May 18, 2006, together with that Certificate of Amendment to the Amended and Restated Certificate of Incorporation dated July 13, 2010 (incorporated by reference to Exhibit 3.1 to the Quarterly Report on Form 10-Q of Enzon Pharmaceuticals, Inc. filed on August 9, 2010).](https://www.sec.gov/Archives/edgar/data/727510/000093041310004342/c62401_ex3-1.txt) |
| &nbsp;&nbsp; 3.2 | [Second Amended and Restated By-Laws effective March 11, 2011, as amended by Amendment No. 1 to the Second Amended and Restated By-Laws effective February 15, 2013 (incorporated by reference to Exhibit 3.2 to the Annual Report on Form 10-K of Enzon Pharmaceuticals, Inc. filed with the SEC on March 18, 2013).](https://www.sec.gov/Archives/edgar/data/727510/000114420413015878/v336897_ex3-2.htm) |
| &nbsp;&nbsp; 3.3 | [First Amendment to the Second Amended and Restated By-Laws, effective February 24, 2022 (incorporated by reference to Exhibit 10.7 to the Annual Report on Form 10-K of Enzon Pharmaceuticals, Inc. filed with the SEC on February 25, 2022).](https://www.sec.gov/Archives/edgar/data/727510/000141057822000226/enzn-20211231xex10d7.htm) |
| &nbsp;&nbsp; 3.4 | [Certificate of Designation of Series A-1 Junior Participating Preferred Stock of Enzon Pharmaceuticals, Inc. filed with the Secretary of State of the State of Delaware on August 14, 2020 (incorporated by reference to Exhibit 3.2 to the Current Report on Form 8-K of Enzon Pharmaceuticals, Inc. filed with the SEC on August 14, 2020).](https://www.sec.gov/Archives/edgar/data/727510/000110465920095642/tm2027628d2_ex3-2.htm) |
| &nbsp;&nbsp; 3.5 | [Certificate of Designation of Series C Non-Convertible Redeemable Preferred Stock of Enzon Pharmaceuticals, Inc., filed with the Secretary of State of the State of Delaware on September 21, 2020 (incorporated by reference to Exhibit 3.1 to the Current Report on Form 8-K of Enzon Pharmaceuticals, Inc. filed with the SEC on September 23, 2020).](https://www.sec.gov/Archives/edgar/data/727510/000110465920107817/tm2031479d1_ex3-1.htm) |
| &nbsp;&nbsp; 3.6\*\* | [Amended and Restated Certificate of Incorporation of Viskase Companies, Inc., filed with the Secretary of State of the State of Delaware on April 3, 2003.](https://www.sec.gov/Archives/edgar/data/727510/000110465926007463/enzn-20250930xex3d6.htm) |
| &nbsp;&nbsp; 3.7\*\* | [Amended and Restated Bylaws of Viskase Companies, Inc., as amended and restated through August 10, 2017.](https://www.sec.gov/Archives/edgar/data/727510/000110465926007463/enzn-20250930xex3d7.htm) |
| &nbsp;&nbsp; 3.8\*\* | [Certificate of Amendment to the Amended and Restated Certificate of Incorporation of Viskase Companies, Inc., filed with the Secretary of State of the State of Delaware on October 7, 2020.](https://www.sec.gov/Archives/edgar/data/727510/000110465926007463/enzn-20250930xex3d8.htm) |
| &nbsp;&nbsp; 4.1 | [Description of Enzon Pharmaceuticals, Inc.'s Registered Securities (incorporated by reference to Exhibit 4.1 to the Annual Report on Form 10-K of Enzon Pharmaceuticals, Inc. filed with the SEC on February 21, 2025).](https://www.sec.gov/Archives/edgar/data/727510/000141057825000177/enzn-20241231xex4d1.htm) |

---

------

---

| | |
|:---|:---|
| **Exhibit <br> Number**  | **Exhibit Description**  |
| &nbsp;&nbsp; 4.2 | [Section 382 Rights Agreement, dated as of August 14, 2020, by and between Enzon Pharmaceuticals, Inc. and Continental Stock Transfer & Trust Company, which includes the Form of Certificate of Designation as Exhibit A, Form of Rights Certificate as Exhibit B and the Form of Summary of Rights as Exhibit C (incorporated by reference to Exhibit 4.1 to the Current Report on Form 8-K of Enzon Pharmaceuticals, Inc. filed with the SEC on August 14, 2020)](https://www.sec.gov/Archives/edgar/data/727510/000110465920095642/tm2027628d2_ex4-1.htm) |
| &nbsp;&nbsp; 4.3 | [First Amendment to the Section 382 Rights Agreement, dated as of June 4, 2021 and effective as of June 2, 2021, by and between Enzon Pharmaceuticals, Inc. and Continental Stock Transfer & Trust Company (incorporated by reference to Exhibit 4.1 to the Current Report on Form 8-K of Enzon Pharmaceuticals, Inc. filed with the SEC on June 8, 2021).](https://www.sec.gov/Archives/edgar/data/727510/000110465921078218/tm2119004d1_ex4-1.htm) |
| &nbsp;&nbsp; 4.4 | [Second Amendment to the Section 382 Rights Agreement, dated as of May 16, 2024, by and between Enzon Pharmaceuticals, Inc., and Continental Stock Transfer & Trust Company (incorporated by reference to Exhibit 4.1 to the Current Report on Form 8-K of Enzon Pharmaceuticals, Inc. filed with the SEC on May 22, 2024).](https://www.sec.gov/Archives/edgar/data/727510/000110465924064247/tm2415024d1_ex4-1.htm) |
| &nbsp;&nbsp; 4.5 | [Third Amendment to the Section 382 Rights Agreement, dated as of March 31, 2025, by and between Enzon Pharmaceuticals, Inc., and Continental Stock Transfer & Trust Company (incorporated by reference to Exhibit 4.1 to the Current Report on Form 8-K of Enzon Pharmaceuticals, Inc. filed with the SEC on April 1, 2025).](https://www.sec.gov/Archives/edgar/data/727510/000110465925030585/tm2511075d1_ex4-1.htm) |
| &nbsp;&nbsp; 4.6 | [Fourth Amendment to the Section 382 Rights Agreement, dated as of August 13, 2025, by and between Enzon Pharmaceuticals, Inc. and Continental Stock Transfer & Trust Company (incorporated by reference to Exhibit 4.1 to the Quarterly Report on Form 10-Q of Enzon Pharmaceuticals, Inc. filed with the SEC on August 14, 2025).](https://www.sec.gov/Archives/edgar/data/727510/000141057825001810/enzn-20250630xex4d1.htm) |
| &nbsp;&nbsp; 4.7 | [Fifth Amendment to the Section 382 Rights Agreement, dated as of September 30, 2025, by and between Enzon Pharmaceuticals, Inc. and Continental Stock Transfer & Trust Company (incorporated by reference to Exhibit 4.1 to the Current Report on Form 8-K of Enzon Pharmaceuticals, Inc. filed with the SEC on September 30, 2025).](https://www.sec.gov/Archives/edgar/data/727510/000110465925095078/tm2527543d1_ex4-1.htm) |
| &nbsp;&nbsp; 4.8 | [Sixth Amendment to the Section 382 Rights Agreement, dated as of December 23, 2025, by and between Enzon Pharmaceuticals, Inc. and Continental Stock Transfer & Trust Company (incorporated by reference to Exhibit 4.1 to the Current Report on Form 8-K of Enzon Pharmaceuticals, Inc. filed with the SEC on December 23, 2025).](https://www.sec.gov/Archives/edgar/data/727510/000110465925124254/tm2534122d1_ex4-1.htm) |
| &nbsp;&nbsp; 4.9 | [Seventh Amendment to the Section 382 Rights Agreement, dated as of January 30, 2026, by and between Enzon Pharmaceuticals, Inc. and Continental Stock Transfer & Trust Company (incorporated by reference to Exhibit 4.1 to the Current Report on Form 8-K of Enzon Pharmaceuticals, Inc. filed with the SEC on January 30, 2026).](https://www.sec.gov/Archives/edgar/data/727510/000110465926008322/tm2521156d11_ex4-1.htm) |
| &nbsp;&nbsp; 5.1\*\* | [Legal Opinion of Thompson Hine LLP.](https://www.sec.gov/Archives/edgar/data/727510/000110465926007463/enzn-20250930xex5d1.htm) |
| 10.1 | [Development, License and Supply Agreement between Enzon, Inc. (now known as Enzon Pharmaceuticals, Inc.) and Schering Corporation dated November 14, 1990, as amended (incorporated by reference to Exhibit 10.15 to the Annual Report on Form 10-K of Enzon Pharmaceuticals, Inc. filed with the SEC on September 26, 2002).](https://www.sec.gov/Archives/edgar/data/727510/000116923202001801/d52002_ex10-15.txt) |
| 10.2 | [Amended and Restated Exclusive IP Marketing Agreement, dated as of June 28, 2004, by and between Micromet AG and Enzon Pharmaceuticals, Inc (incorporated by reference to Exhibit 10.28 to the Annual Report on Form 10-K of Enzon Pharmaceuticals, Inc. filed with the SEC on February 21, 2019).](https://www.sec.gov/Archives/edgar/data/727510/000114420419009301/tv513334_ex10-28.htm) |
| 10.3 | [Letter Agreement, dated January 30, 2019, between Servier IP UK Limited and Enzon Pharmaceuticals, Inc. (incorporated by reference to Exhibit 10.29 to the Annual Report on Form 10-K of Enzon Pharmaceuticals, Inc. filed with the SEC on February 21, 2019).](https://www.sec.gov/Archives/edgar/data/727510/000114420419009301/tv513334_ex10-29.htm) |
| 10.4 | [Investment Agreement, dated as of September 1, 2020, by and between Enzon Pharmaceuticals, Inc. and Icahn Capital LP (incorporated by reference to Exhibit 10.1 to the Current Report on Form 8-K of Enzon Pharmaceuticals, Inc. filed with the SEC on September 1, 2020).](https://www.sec.gov/Archives/edgar/data/727510/000110465920101397/tm2030022d1_ex10-1.htm) |

---

------

---

| | |
|:---|:---|
| **Exhibit <br> Number**  | **Exhibit Description**  |
| 10.5# | [Independent Contractor Agreement, effective as of February 24, 2022, between Enzon Pharmaceuticals, Inc. and Richard L. Feinstein (incorporated by reference to Exhibit 3.5 to the Annual Report on Form 10-K of Enzon Pharmaceuticals, Inc. filed with the SEC on February 25, 2022).](https://www.sec.gov/Archives/edgar/data/727510/000141057822000226/enzn-20211231xex3d5.htm) |
| 10.6# | [Form of Indemnification Agreement for members of the Board of Directors (incorporated by reference to Exhibit 10.2 to the Quarterly Report on Form 10-Q of Enzon Pharmaceuticals, Inc. filed with the SEC on April 26, 2022).](https://www.sec.gov/Archives/edgar/data/727510/000141057822001018/enzn-20220331xex10d2.htm) |
| 10.7\*\*† | [Credit Agreement, dated October 9, 2020, by and between Viskase Companies, Inc., Bank of America, N.A., BMO Harris Bank N.A., Truist Bank, BOFA Securities, Inc., BMO Capital Markets Corp., and BOFA Securities, Inc.](https://www.sec.gov/Archives/edgar/data/727510/000110465926007463/enzn-20250930xex10d7.htm)  |
| 10.8\*\* | [First Amendment to Credit Agreement, dated August 13, 2021.](https://www.sec.gov/Archives/edgar/data/727510/000110465926007463/enzn-20250930xex10d8.htm)  |
| 10.9\*\* | [Second Amendment to Credit Agreement, dated August 10, 2022.](https://www.sec.gov/Archives/edgar/data/727510/000110465926007463/enzn-20250930xex10d9.htm)  |
| 10.10\*\*#  | [Employment Agreement, dated September 6, 2022, by and between Timothy Feast and Viskase Companies, Inc.](https://www.sec.gov/Archives/edgar/data/727510/000110465926007463/enzn-20250930xex10d10.htm)  |
| 10.11\*\*#  | [Viskase Companies, Inc. 2022 Long-Term Incentive Plan.](https://www.sec.gov/Archives/edgar/data/727510/000110465926007463/enzn-20250930xex10d11.htm)  |
| 10.12\*\*#  | [Viskase Companies, Inc. 2024 Management Incentive Plan.](https://www.sec.gov/Archives/edgar/data/727510/000110465926007463/enzn-20250930xex10d12.htm)  |
| 10.13\*\* | [Limited Waiver and Third Amendment to Credit Agreement, dated February 14, 2025.](https://www.sec.gov/Archives/edgar/data/727510/000110465926007463/enzn-20250930xex10d13.htm)  |
| 10.14† | [Support Agreement, dated as of June 20, 2025, by and between Icahn Enterprises Holdings L.P. and certain of its affiliates, Enzon Pharmaceuticals, Inc. and Viskase Companies, Inc. (included as Annex B to the prospectus/consent solicitation/offer to exchange).](https://www.sec.gov/ix?doc=/Archives/edgar/data/727510/000110465926007463/enzn-20250930xs4.htm#AnnexB_270225)  |
| 10.15\*\* | [Fourth Amendment to Credit Agreement, dated July 25, 2025.](https://www.sec.gov/Archives/edgar/data/727510/000110465926007463/enzn-20250930xex10d15.htm)  |
| 10.16\*\* | [Fourth Amendment Fee Letter to Credit Agreement, dated July 25, 2025.](https://www.sec.gov/Archives/edgar/data/727510/000110465926007463/enzn-20250930xex10d16.htm)  |
| 10.17\*\*#  | [Joseph King Offer Letter, dated May 4, 2022, by and between Viskase Companies, Inc. and Joseph King.](https://www.sec.gov/Archives/edgar/data/727510/000110465926007463/enzn-20250930xex10d17.htm)  |
| 10.18\*\*#  | [Thomas Holz Offer Letter, dated December 19, 2022, by and between Viskase Companies, Inc. and Thomas Holz.](https://www.sec.gov/Archives/edgar/data/727510/000110465926007463/enzn-20250930xex10d18.htm)  |
| 10.19\*\*#  | [Armando Herrara Offer Letter, dated March 15, 2024, by and between Viskase Companies, Inc. and Armando Herrara.](https://www.sec.gov/Archives/edgar/data/727510/000110465926007463/enzn-20250930xex10d19.htm)  |
| 10.20\*\*#  | [Jan Stevens Offer Letter, dated June 7, 2024, by and between Viskase Companies, Inc. and Jan Stevens.](https://www.sec.gov/Archives/edgar/data/727510/000110465926007463/enzn-20250930xex10d20.htm)  |
| 10.21\*\*#  | [Marcelo Passos Offer Letter, dated September 13, 2024, by and between Viskase Companies, Inc. and Marcelo Passos.](https://www.sec.gov/Archives/edgar/data/727510/000110465926007463/enzn-20250930xex10d21.htm)  |
| 10.22\*\*#  | [Joseph Marigliano Offer Letter, dated January 30, 2025, by and between Viskase Companies, Inc. and Joseph Marigliano.](https://www.sec.gov/Archives/edgar/data/727510/000110465926007463/enzn-20250930xex10d22.htm)  |
| 10.23\*\* | [Silverman Consulting, Inc. Engagement Letter, dated November 1, 2025, by and between Viskase Companies, Inc. and Silverman Consulting, Inc.](https://www.sec.gov/Archives/edgar/data/727510/000110465926007463/enzn-20250930xex10d23.htm)  |
| 10.24\*\* | [First Amendment to Support Agreement, dated as of October 24, 2025, by and between Icahn Enterprises Holdings L.P. and certain of its affiliates, Enzon Pharmaceuticals, Inc. and Viskase Companies, Inc. (included as Annex B-1 to the prospectus/consent solicitation/offer to exchange).](https://www.sec.gov/ix?doc=/Archives/edgar/data/727510/000110465926007463/enzn-20250930xs4.htm#AnnexB1_368903) |
| 10.25\*\*#  | [Employment Agreement between Viskase Companies, Inc. and Thomas D. Davis, effective December 1, 2025.](https://www.sec.gov/Archives/edgar/data/727510/000110465926007463/enzn-20250930xex10d25.htm)  |
| 10.26\*\*#  | [John Plescia Offer Letter, dated December 8, 2025, by and between Viskase Companies, Inc. and John Plescia.](https://www.sec.gov/Archives/edgar/data/727510/000110465926007463/enzn-20250930xex10d26.htm)  |
| 10.27\*\*#  | [Robert Schouten Offer Letter, dated September 23, 2025, by and between Viskase GmbH and Robert Schouten.](https://www.sec.gov/Archives/edgar/data/727510/000110465926007463/enzn-20250930xex10d27.htm)  |

---

------

---

| | |
|:---|:---|
| **Exhibit <br> Number**  | **Exhibit Description**  |
| 10.28\*\* | [Securities Purchase Agreement, dated December 30, 2025, by and between Viskase Companies, Inc. and American Entertainment Properties Corp.](https://www.sec.gov/Archives/edgar/data/727510/000110465926007463/enzn-20250930xex10d28.htm)  |
| 10.29\*\*† | [Fifth Amendment to Credit Agreement dated October 10, 2025.](https://www.sec.gov/Archives/edgar/data/727510/000110465926007463/enzn-20250930xex10d29.htm)  |
| 10.30\*\* | [Securities Purchase Agreement, dated January 23, 2026, by and between Viskase Companies, Inc. and American Entertainment Properties Corp.](https://www.sec.gov/Archives/edgar/data/727510/000110465926007463/enzn-20250930xex10d30.htm)  |
| 10.31\*\* | [Sixth Amendment to Credit Agreement dated January 23, 2026.](https://www.sec.gov/Archives/edgar/data/727510/000110465926007463/enzn-20250930xex10d31.htm)  |
| 10.32\*\* | [Fifth Amendment Fee Letter to Credit Agreement, dated October 10, 2025.](https://www.sec.gov/Archives/edgar/data/727510/000110465926007463/enzn-20250930xex10d32.htm)  |
| 21.1 | [Subsidiaries of Registrant (incorporated by reference to Exhibit 21.1 to the Annual Report on Form 10-K of Enzon Pharmaceuticals, Inc. filed with the SEC on February 21, 2025).](https://www.sec.gov/Archives/edgar/data/727510/000141057825000177/enzn-20241231xex21d1.htm)  |
| 23.1\*\* | [Consent of EisnerAmper LLP, independent registered public accounting firm for Enzon Pharmaceuticals, Inc.](https://www.sec.gov/Archives/edgar/data/727510/000110465926007463/enzn-20250930xex23d1.htm)  |
| 23.2\*\* | [Consent of Grant Thornton LLP, independent registered public accounting firm for Viskase Companies, Inc.](https://www.sec.gov/Archives/edgar/data/727510/000110465926007463/enzn-20250930xex23d2.htm)  |
| 23.3\*\* | [Consent of Thompson Hine LLP (included in Exhibit 5.1).](https://www.sec.gov/Archives/edgar/data/727510/000110465926007463/enzn-20250930xex5d1.htm)  |
| 24.1\*\* | [Power of Attorney (included on signature page hereto).](https://www.sec.gov/ix?doc=/Archives/edgar/data/727510/000110465926007463/enzn-20250930xs4.htm#POWEROFATTORNEY_942409)  |
| 99.1\*\* | [Form of Written Consent of Holders of Common Stock of Enzon Pharmaceuticals, Inc. (included as Annex G to the prospectus/consent solicitation/offer to exchange).](https://www.sec.gov/ix?doc=/Archives/edgar/data/727510/000110465926007463/enzn-20250930xs4.htm#AnnexG_5489)  |
| 99.2\*\* | [Consent of Robert Flint to be named as a director.](https://www.sec.gov/Archives/edgar/data/727510/000110465926007463/enzn-20250930xex99d2.htm)  |
| 99.3\*\* | [Consent of Colin Kwak to be named as a director.](https://www.sec.gov/Archives/edgar/data/727510/000110465926007463/enzn-20250930xex99d3.htm)  |
| 99.4\*\* | [Consent of Peter K. Shea to be named as a director.](https://www.sec.gov/Archives/edgar/data/727510/000110465926007463/enzn-20250930xex99d4.htm)  |
| 99.5\*\* | [Consent of Kenneth Shea to be named as a director.](https://www.sec.gov/Archives/edgar/data/727510/000110465926007463/enzn-20250930xex99d5.htm)  |
| 99.6\*\* | [Consent of Dustin DeMaria to be named as a director.](https://www.sec.gov/Archives/edgar/data/727510/000110465926007463/enzn-20250930xex99d6.htm)  |
| 99.7\*\* | [Consent of A.G.P./Alliance Global Partners LLC, financial advisor for Enzon Pharmaceuticals, Inc.](https://www.sec.gov/Archives/edgar/data/727510/000110465926007463/enzn-20250930xex99d7.htm)  |
| 99.8\*\* | [Consent of Alvarez & Marsal Valuation Services, LLC, financial advisor for Viskase Companies, Inc.](https://www.sec.gov/Archives/edgar/data/727510/000110465926007463/enzn-20250930xex99d8.htm)  |
| 99.9\* | [Letter of Transmittal.](tm2521156d9_ex99-9.htm)  |
| 99.10\* | [Notice of Guaranteed Delivery.](tm2521156d9_ex99-10.htm)  |
| 99.11\* | [Letter to Brokers, Dealers, Commercial Banks, Trust Companies, Custodians and Similar Institutions.](tm2521156d9_ex99-11.htm)  |
| 99.12\* | [Letter to Clients for Use by Brokers, Dealers, Commercial Banks, Trust Companies, Custodians and Similar Institutions.](tm2521156d9_ex99-12.htm)  |
| 99.13\* | [Press release issued by Enzon Pharmaceuticals, Inc., dated January 30, 2026](tm2521156d10_ex99-13.htm)  |
| 107\*\* | [Filing Fee Table](https://www.sec.gov/Archives/edgar/data/727510/000110465926007463/enzn-20250930xexfees.htm)  |

---

\*

Filed herewith.

\*\*

Previously filed.

^

Portions of this exhibit have been redacted and filed separately with the SEC pursuant to a confidential treatment request.

#

Management contracts or compensatory plans and arrangements required to be filed pursuant to Item 601(b)(10)(ii)(A) or (iii) of Regulation S-K.

†

Schedules, exhibits and/or annexes have been omitted pursuant to Item 601(b)(2) of Regulation S-K. A copy of any such omitted item will be furnished supplementally to the Securities and Exchange Commission upon request

------

#### SIGNATURES
Pursuant to the requirements of the Securities Act of 1933, as amended, the registrant has duly caused this registration statement to be signed on its behalf by the undersigned, thereunto duly authorized, in the City of Cranford, State of New Jersey, on January 30, 2026.

#### ENZON PHARMACEUTICALS, INC.
By:

/s/ Richard L. Feinstein

Richard L. Feinstein

Chief Executive Officer, Chief Financial

Officer and Secretary

Pursuant to the requirements of the Securities Act, this registration statement has been signed by the following persons in the capacities and on the dates indicated, on January 30, 2026.

---

| | |
|:---|:---|
| **Signature**  | **Title**  |
| /s/ Richard L. Feinstein <br>Richard L. Feinstein  | *Chief Executive Officer, Chief Financial <br> Officer and Secretary <br> (Principal Executive Officer)*  |
| \* <br>Randolph C. Read  | *Director (Chairman of the Board)*  |
| \* <br>Jordan Bleznick  | *Director*  |
| \* <br>Jaffrey A. Firestone  | *Director*  |
| \* <br>Stephen T. Wills  | *Director*  |
| &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; \*By: <br>/s/ Richard L. Feinstein <br>Name: Richard L. Feinstein <br> Title: Attorney-in-Fact  |  |

---

------

## Exhibit 99.9

#### Exhibit 99.9

#### LETTER OF TRANSMITTAL

#### OFFER TO EXCHANGE SHARES OF SERIES C NON-CONVERTIBLE REDEEMABLE PREFERRED STOCK OF

### ENZON PHARMACEUTICALS, INC.

#### for

#### Shares of Common Stock of Enzon Pharmaceuticals, Inc. (subject to the terms and conditions described in the prospectus/consent solicitation/offer to exchange and this letter of transmittal)

#### The Depositary and Exchange Agent for the offer is:
![[MISSING IMAGE: lg_continental-bwlr.jpg]](lg_continental-bwlr.jpg)

---

| | |
|:---|:---|
| *<u>If delivering by mail:</u>* <br> Continental Stock Transfer & Trust Company, <br> Attn: Corporate Actions, <br> 1 State Street 30th Floor, New York, NY 10004 <br> Telephone: 800-509-5586  | *<u>If delivering by hand, express mail, courier</u>* <br> *<u>or any other expedited service:</u>* <br> Continental Stock Transfer & Trust Company, <br> Attn: Corporate Actions, <br> 1 State Street 30th Floor, New York, NY 10004 <br> Telephone: 800-509-5586  |

---

 **DELIVERY OF THIS LETTER OF TRANSMITTAL TO AN ADDRESS OTHER THAN AS SET FORTH ABOVE WILL NOT CONSTITUTE A VALID DELIVERY TO THE EXCHANGE AGENT.** 

---

| | | |
|:---|:---|:---|
| **THE OFFER AND THE WITHDRAWAL RIGHTS WILL EXPIRE AT ONE MINUTE AFTER 11:59 P.M., EASTERN TIME, ON FEBRUARY 27, 2026, UNLESS EXTENDED OR TERMINATED. SHARES TENDERED PURSUANT TO THE OFFER MAY BE WITHDRAWN AT ANY TIME PRIOR TO THE EXPIRATION OF THE OFFER.** | **THE OFFER AND THE WITHDRAWAL RIGHTS WILL EXPIRE AT ONE MINUTE AFTER 11:59 P.M., EASTERN TIME, ON FEBRUARY 27, 2026, UNLESS EXTENDED OR TERMINATED. SHARES TENDERED PURSUANT TO THE OFFER MAY BE WITHDRAWN AT ANY TIME PRIOR TO THE EXPIRATION OF THE OFFER.** | **THE OFFER AND THE WITHDRAWAL RIGHTS WILL EXPIRE AT ONE MINUTE AFTER 11:59 P.M., EASTERN TIME, ON FEBRUARY 27, 2026, UNLESS EXTENDED OR TERMINATED. SHARES TENDERED PURSUANT TO THE OFFER MAY BE WITHDRAWN AT ANY TIME PRIOR TO THE EXPIRATION OF THE OFFER.** |
| **DESCRIPTION OF SHARES TENDERED**  | **DESCRIPTION OF SHARES TENDERED**  | **DESCRIPTION OF SHARES TENDERED**  |
| **Name(s) and Address(es) of Registered Holder(s) <br> (Please fill in, if blank, exactly as name(s) <br> appear(s) on security position listing)**  | **Number and Class of Shares Tendered <br> (Attach additional signed list if necessary. See Instruction 4)**  | **Number and Class of Shares Tendered <br> (Attach additional signed list if necessary. See Instruction 4)**  |
|  |  | **Total Number of <br> Shares <br> Tendered (book entry shares <br> and Direct Registration <br> Shares) (2)**  |
|  | **Total Shares** |  |

---

#### THE INSTRUCTIONS SET FORTH IN THIS LETTER OF TRANSMITTAL SHOULD BE READ CAREFULLY AND IN THEIR ENTIRETY BEFORE THIS LETTER OF TRANSMITTAL IS COMPLETED.
 **The offer (described below) is not being made to (nor will tender of shares be accepted from or on behalf of) stockholders in any jurisdiction where it would be illegal to do so.** 

------

Ladies and Gentlemen:

Enzon Pharmaceuticals, Inc., a Delaware corporation (the "Offeror") is offering, upon the terms and subject to the conditions set forth in the Prospectus/Consent Solicitation/Offer to Exchange (as defined below) and in this letter of transmittal, to exchange for each outstanding share of Series C Non-Convertible Redeemable Preferred Stock, $0.01 par value per share (the "Series C Preferred Stock") validly tendered and not validly withdrawn in the offer: a number of shares of the Offeror's common stock, $0.01 par value per share (the "Common Stock") equal to (i) the aggregate liquidation preference of each share of Series C Preferred Stock, divided by (ii) $7.83 after giving effect to the Reverse Stock Split (as defined in the Prospectus/Consent Solicitation/Offer to Exchange, dated January 28, 2026 (the "Prospectus/Consent Solicitation/Offer to Exchange")) (the "Exchange Ratio," and such offer, on the terms and subject to the conditions and procedures set forth in the Prospectus/Consent Solicitation/Offer to Exchange and the Letter of Transmittal, together with any amendments or supplements thereto, the "Offer").

The Offer is being made to all holders of Series C Preferred Stock. The Series C Preferred Stock is governed by the Certificate of Designation, dated September 21, 2020. The Series C Preferred Stock is not listed on a securities exchange nor traded in an over-the-counter market. As of January 30, 2026, a total of 40,000 shares of Series C Preferred Stock were outstanding.

The Offeror has filed with the Securities and Exchange Commission a Registration Statement on Form S-4, dated January 28, 2026 (the "Registration Statement"), relating to (i) the issuance of Common Stock in connection with the proposed merger (the "Merger") of the Company and Viskase Companies, Inc. ("Viskase"), and (ii) the offer to exchange shares of Common Stock to holders of shares of Series C Preferred Stock validly tendered and not validly withdrawn in the Offer.

The Offer is conditioned upon the satisfaction or waiver of all of the conditions to the consummation of the Merger set forth in the Agreement and Plan of Merger, dated June 20, 2025 by and among the Offeror, EPSC Acquisition Corp. ("EPSC") and Viskase (the "Original Merger Agreement"), as amended by the First Amendment to the Agreement and Plan of Merger, dated October 24, 2025, by and among the Offeror, EPSC and Viskase (the "First Amendment to the Merger Agreement," and, as amended, the "Merger Agreement"), including, without limitation, the receipt by the Offeror of the requisite written consent of its stockholders approving the Merger and the other transactions contemplated by the Merger Agreement. The Offeror intends to complete the Offer substantially concurrently with the consummation of the Merger.

Shares of Series C Preferred Stock not exchanged for shares of Common Stock pursuant to the Offer will remain outstanding subject to their current terms. We reserve the right to redeem any of the shares of Series C Preferred Stock, as applicable, pursuant to their terms at any time, including prior to the completion of the Offer.

This letter of transmittal is to be used for tendering shares of Series C Preferred Stock to the Offeror pursuant to the Offer. Holders of Series C Preferred Stock may use this letter of transmittal to tender shares of Series C Preferred Stock held in electronic book-entry form, except that return of this letter of transmittal to the Exchange Agent is not required if a message is transmitted by The Depositary Trust Company ("DTC") to, and is received by, Continental Stock Transfer & Trust (the "Exchange Agent"), forming a part of a book-entry confirmation, which states that DTC has received an express acknowledgement from the DTC participant tendering the shares that are the subject of such transmittal and that the Offeror may enforce this agreement against such participant (an "Agent's Message"). In each case, tendering Offeror stockholders should follow the other instructions set forth in this letter of transmittal and in the Prospectus/Consent Solicitation/Offer to Exchange, including the section of the Prospectus/Consent Solicitation/Offer to Exchange entitled "*Series C Exchange Offer — Procedures for Tendering Shares of Enzon Series C Preferred Stock*."

The Offer is scheduled to expire one minute after 11:59 p.m., Eastern Time, at the end of February 27, 2026, unless extended or terminated. "Expiration of the Offer" means one minute after 11:59 p.m., Eastern Time, at the end of February 27, 2026, unless and until the Offeror has extended the period during which the Offer is open, subject to the terms and conditions of the Merger Agreement, in which event the term "Expiration of the Offer" means the latest time and date at which the Offer, as so extended by the Offeror, will expire. Stockholders whose certificates for shares are not immediately available or who cannot deliver their certificates and all other required documents to the Exchange Agent or complete the procedures for book-entry transfer prior to the Expiration Time may tender their shares by properly completing and duly

------

executing the Notice of Guaranteed Delivery pursuant to the guaranteed delivery procedures set forth the section of the Prospectus/Consent Solicitation/Offer to Exchange entitled "*Series C Exchange Offer — Procedures for Tendering Shares of Enzon Series C Preferred Stock*."

By signing and returning this letter of transmittal, or through delivery of an Agent's Message, the undersigned elects to tender his, her or its shares of Series C Preferred Stock pursuant to the foregoing and agrees to the terms set forth herein.

Each holder of Series C Preferred Stock whose shares of Series C Preferred Stock are exchanged pursuant to the Offer will receive that number of shares of Common Stock calculated pursuant to the Exchange Ratio.

Upon the terms and subject to the conditions of the Offer (and, if the Offer is extended, amended, supplemented or earlier terminated, the terms or the conditions of any such extension, amendment, supplement or termination), and subject to and effective upon acceptance for exchange of the shares of Series C Preferred Stock tendered herewith in accordance with the terms of the Offer, the undersigned hereby (i) sells, assigns and transfers to or upon the order of the Offeror all right, title and interest in and to any and all of the shares of Series C Preferred Stock that are being tendered hereby (and any and all dividends, distributions, rights, other shares of Series C Preferred Stock or other securities issued or issuable in respect thereof on or after the date hereof (or on or after the date of the applicable Agent's Message) (collectively, "Distributions")) and (ii) irrevocably constitutes and appoints the Exchange Agent the true and lawful agent and attorney-in-fact of the undersigned with respect to such shares of Series C Preferred Stock (and any and all Distributions), with full power of substitution (such power of attorney being deemed to be an irrevocable power coupled with an interest), to (1) transfer ownership of such shares of Series C Preferred Stock (and any and all Distributions) on the account books maintained by DTC, together, in any such case, with all accompanying evidences of transfer and authenticity, to or upon the order of the Offeror, (2) present such shares of Series C Preferred Stock (and any and all Distributions) for transfer on the books of the Offeror and (3) receive all benefits and otherwise exercise all rights of beneficial ownership of such shares of Series C Preferred Stock (and any and all Distributions), all in accordance with the terms of the Offer.

For clarity, unless and until the Offeror has accepted the shares of Series C Preferred Stock for exchange in the Offer, the foregoing sale, assignment, transfer and appointment shall have no effect and shall be deemed not to have any effect.

Subject to the following provisions of this paragraph, the undersigned hereby irrevocably appoints the designees of the Offeror as the undersigned's agents, attorneys-in-fact and proxies, each with full power of substitution, to exercise to the full extent the rights of the undersigned with respect to all of the shares of Series C Preferred Stock tendered hereby (and any and all Distributions) that have been accepted for exchange by the Offeror. All such powers of attorney and proxies shall be considered irrevocable and coupled with an interest in the tendered shares of Series C Preferred Stock (and any and all Distributions); provided that such appointment will be effective when, and only to the extent that, the Offeror accepts such shares of Series C Preferred Stock for exchange and deposits with the Exchange Agent the transaction consideration for such shares of Series C Preferred Stock. Such acceptance for exchange will, without further action, revoke any prior powers of attorney and proxies given by the undersigned at any time with respect to such shares of Series C Preferred Stock (and any and all Distributions), and no subsequent powers of attorney, proxies, consents or revocations may be given or executed by the undersigned with respect to such tendered shares of Series C Preferred Stock (and, if given or executed, will not be deemed effective). The designees of the Offeror will, with respect to such shares of Series C Preferred Stock (and any and all Distributions) for which the appointment is effective, be empowered to exercise all voting, consent and other rights of such stockholder with respect to such stockholder's shares of Series C Preferred Stock as they in their discretion may deem proper at any annual or special meeting of Offeror stockholders or any adjournment or postponement thereof, by written consent in lieu of any such meeting or otherwise. The Offeror reserves the right to require that, in order for such shares of Series C Preferred Stock to be deemed validly tendered, immediately upon the Offeror's acceptance of such shares of Series C Preferred Stock for exchange, the Offeror must be able to exercise full voting, consent and other rights with respect to such shares of Series C Preferred Stock (and any and all Distributions). For clarity, unless and until the Offeror has accepted the shares of Series C Preferred Stock for exchange in the Offer, the foregoing appointment and provisions of this paragraph shall have no effect and shall be deemed not to have any effect.

------

The undersigned hereby represents and warrants that (1) the undersigned owns the tendered shares of Series C Preferred Stock (and any and all other shares of Series C Preferred Stock or other securities issued or issuable in respect of such shares of Series C Preferred Stock); (2) the undersigned has the full power and authority to tender, sell, assign and transfer the tendered shares of Series C Preferred Stock (and any and all Distributions); and (3) when the same are accepted for exchange by the Offeror, the Offeror will acquire good and unencumbered title to the same number of shares of Series C Preferred Stock as are tendered hereby, free and clear of all liens, restrictions, charges and encumbrances and not subject to any adverse claims and such shares of Series C Preferred Stock (and any and all Distributions) will not be transferred to the Offeror in violation of any contractual or other restriction on the transfer thereof. The undersigned, upon request, will execute and deliver all additional documents deemed by the Exchange Agent or the Offeror to be necessary or desirable to complete the sale, assignment and transfer of the shares of Series C Preferred Stock tendered hereby (and any and all Distributions). In addition, the undersigned will remit and transfer promptly to the Exchange Agent for the account of the Offeror all Distributions in respect of the shares of Series C Preferred Stock tendered hereby, accompanied by appropriate documentation of transfer, and, pending such remittance and transfer or appropriate assurance thereof, the Offeror will be entitled to all rights and privileges as the owner of each such Distribution and may withhold the entire consideration payable in the Offer in respect of the shares of Series C Preferred Stock tendered hereby or deduct from such consideration the amount or value of such Distribution as determined by the Offeror in its sole discretion.

All authority herein conferred or agreed to be conferred will survive the death or incapacity of the undersigned, and any obligation of the undersigned hereunder will be binding upon the heirs, executors, administrators, personal representatives, trustees in bankruptcy, successors and assigns of the undersigned. Except as stated in the Prospectus/Consent Solicitation/Offer to Exchange, this tender is irrevocable.

The undersigned understands that the acceptance for exchange by the Offeror of shares of Series C Preferred Stock will constitute a binding agreement between the undersigned and the Offeror upon the terms of and subject to the conditions to the Offer (and, if the Offer is extended, amended, supplemented or earlier terminated, the terms or the conditions of any such extension, amendment, supplement or termination). The undersigned recognizes that, under the circumstances set forth in the Prospectus/Consent Solicitation/Offer to Exchange, the Offeror may not be required to accept for exchange any of the shares of Series C Preferred Stock tendered hereby.

The undersigned understands that the delivery and surrender of shares of Series C Preferred Stock that the undersigned has tendered are not effective, and the risk of loss of such shares of Series C Preferred Stock does not pass to the Exchange Agent, unless and until the Exchange Agent receives this letter of transmittal, properly completed and duly executed, or an Agent's Message, together with all accompanying evidences of authority in form satisfactory to the Offeror and any other required documents. THE UNDERSIGNED UNDERSTANDS THAT THE OFFEROR'S INTERPRETATION OF THE TERMS AND CONDITIONS OF THE OFFER (INCLUDING THIS LETTER OF TRANSMITTAL AND THE INSTRUCTIONS HERETO) WILL BE FINAL AND BINDING TO THE FULLEST EXTENT PERMITTED BY LAW. ALL QUESTIONS AS TO THE FORM OF DOCUMENTS AND THE VALIDITY, FORM, ELIGIBILITY (INCLUDING TIME OF RECEIPT) AND ACCEPTANCE FOR EXCHANGE OF ANY SHARES OF SERIES C PREFERRED STOCK WILL BE DETERMINED BY THE OFFEROR IN ITS DISCRETION, WHICH DETERMINATION WILL BE FINAL AND BINDING TO THE FULLEST EXTENT PERMITTED BY LAW. The undersigned also understands that no tender of shares of Series C Preferred Stock will be deemed validly made until all defects and irregularities with respect thereto have been cured or waived. In addition, the undersigned understands that none of the Offeror, Viskase, or any of their respective affiliates or assigns, the Exchange Agent or the information agent identified on the back page of this letter of transmittal or any other person is or will be under any duty to give notification of any defects or irregularities in tenders or will incur any liability for failure to give any such notification.

Unless otherwise indicated under "Special Issuance or Payment Instructions," the undersigned hereby requests that the shares of Series C Preferred Stock and the return of any shares of Series C Preferred Stock not tendered or not accepted for exchange, be in the name(s) of the undersigned and by credit to the applicable account at DTC. The undersigned recognizes that the Offeror has no obligation, pursuant to the

------

"Special Issuance or Payment Instructions," to transfer any shares of Series C Preferred Stock from the name of the registered holder(s) thereof if the Offeror does not accept for exchange such shares of Series C Preferred Stock so tendered.

Similarly, unless otherwise indicated under "Special Delivery Instructions," the undersigned hereby requests that the certificates for shares of Series C Preferred Stock (or, at the Offeror's election, evidence of book-entry of Series C Preferred Stock) be delivered to the undersigned at the address(es) of the registered holder(s). In the event that the boxes titled "Special Issuance or Payment Instructions" and "Special Delivery Instructions" are both completed, the undersigned hereby requests that the certificates for shares of Common Stock (or, at the Offeror's election, evidence of book-entry of Common Stock) be issued in the name(s) of and delivered to the person(s) so indicated.

---

| |
|:---|
| **SPECIAL ISSUANCE OR PAYMENT INSTRUCTIONS <br> (See Instructions 1, 5, 6 and 7)**  |
| To be completed ONLY if the shares of Common Stock are to be issued in the name of someone other than the registered holder(s) listed above in the box titled "Description of Shares Tendered." |
| Issue as follows: |
| Name |
| <br> **(Please Print)**  |
| Address |
| <br> **(Include Zip Code)**  |
| Area Code and <br> Telephone No. |
| Taxpayer Identification or <br> Social Security No. |
| (Also complete the enclosed IRS Form W-9 or an appropriate IRS Form W-8, as applicable)  |
| **SPECIAL DELIVERY INSTRUCTIONS <br> (See Instructions 1, 5 and 7)**  |
| To be completed ONLY if the shares of Common Stock are to be sent to an address other than the address(es) of the registered holder(s) listed above in the box titled "Description of Shares Tendered." |
| Mail as follows: |
| Name |
| <br> **(Please Print)**  |
| Address |
| <br> **(Include Zip Code)**  |
| Area Code and <br> Telephone No. |

---

------

#### IMPORTANT STOCKHOLDER: SIGN HERE (Please complete and return the enclosed IRS Form W-9 or an appropriate IRS Form W-8, as applicable) SIGN HERE:

---

| |
|:---|
| Sign Here: <br>|
| **Signature(s) of Holder(s) of Shares**  |
| Sign Here: <br>|
| **Signature(s) of Holder(s) of Shares**  |
| Date <br>|
| Name <br>|
| **(Please Print)**  |
| Capacity <br> (full title) <br>|
| Address <br>|
| **(Include Zip Code)**  |
| Area Code and <br> Telephone No. <br>|
| Tax <br> Identification or <br> Social Security <br> No. (See <br> enclosed IRS <br> Form W-9) <br>|
| (Must be signed by registered holder(s) exactly as name(s) appear(s) on a security position listing or by person(s) authorized to become registered holder(s) by documents transmitted herewith. If signature is by a trustee, executor, administrator, guardian, attorney-in-fact, agent, officer of a corporation or other person acting in a fiduciary or representative capacity, please set forth full title and see Instruction 5.) |

---

---

| |
|:---|
| **Guarantee of Signature(s) <br> (If Required — See Instructions 1 and 5)**  |
| Authorized Signature <br>|
| Name: <br>|
| Name of Firm <br>|
| Address <br>|
| **(Include Zip Code)**  |
| Area Code and <br> Telephone No. <br>|
| Date <br>|

---

------

#### INSTRUCTIONS FORMING PART OF THE TERMS AND CONDITIONS OF THE OFFER
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; **1. Guarantee of Signatures**. No signature guarantee is required on this letter of transmittal (1) if this letter of transmittal is signed by the registered holder(s) (which term, for purposes of this document, includes any participant in DTC's systems whose name(s) appear(s) on a security position listing as the owner(s) of the shares of Series C Preferred Stock) of shares of Series C Preferred Stock and such holder(s) have not completed either the box titled "Special Issuance or Payment Instructions" or the box titled "Special Delivery Instructions" on this letter of transmittal or (2) if shares of Series C Preferred Stock are tendered for the account of a financial institution (including most commercial banks, savings and loan associations and brokerage houses) that is a member in the Security Transfer Agents Medallion Program or by any other "eligible guarantor institution," as such term is defined in Rule 17Ad-15 under the Securities Exchange Act of 1934, as amended (an "eligible institution"). In all other cases, all signatures on this letter of transmittal must be guaranteed by an eligible institution. See also Instruction 5.

&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; **2. Requirements of Tender**. This letter of transmittal is to be completed and signed by Offeror stockholders, with any required signature guarantees, and returned to the Exchange Agent, together with a properly completed IRS Form W-9 or IRS Form W-8, as applicable, and any other documents required by this letter of transmittal or the Exchange Agent, except that this letter of transmittal does not need to be used if an Agent's Message is utilized. An "Agent's Message" is a message transmitted by DTC to, and received by, the Exchange Agent, forming a part of a book-entry confirmation, which states that DTC has received an express acknowledgment from the DTC participant tendering the shares that are the subject of such book-entry confirmation that such participant has received and agrees to be bound by the terms of this letter of transmittal and that the Offeror may enforce this agreement against such participant. For an Offeror stockholder to validly tender shares of Series C Preferred Stock pursuant to the offer, the Exchange Agent must receive prior to the Expiration of the Offer this letter of transmittal (or a manually signed facsimile thereof), properly completed and duly executed, together with any required signature guarantees or, in the case of a book-entry transfer, an Agent's Message in the case of a book-entry transfer, and any other documents required by this letter of transmittal or the Exchange Agent, at one of the Exchange Agent's addresses set forth on the back cover of this letter of transmittal. See also the section of the Prospectus/Consent Solicitation/Offer to Exchange entitled "*Series C Exchange Offer — Procedures for Tendering Shares of Enzon Series C Preferred Stock*."

 **THE METHOD OF DELIVERY OF THIS LETTER OF TRANSMITTAL AND ALL OTHER REQUIRED DOCUMENTS, INCLUDING DELIVERY THROUGH DTC, IS AT THE OPTION AND THE RISK OF THE TENDERING OFFEROR STOCKHOLDER, AND THE DELIVERY WILL BE DEEMED MADE ONLY WHEN ACTUALLY RECEIVED BY THE EXCHANGE AGENT. IF DELIVERY IS BY MAIL, REGISTERED MAIL WITH RETURN RECEIPT REQUESTED, PROPERLY INSURED, IS RECOMMENDED. IN ALL CASES, SUFFICIENT TIME SHOULD BE ALLOWED TO ENSURE TIMELY DELIVERY. THE OFFEROR IS NOT PROVIDING FOR GUARANTEED DELIVERY PROCEDURES. ACCORDINGLY, OFFEROR STOCKHOLDERS MUST ALLOW SUFFICIENT TIME FOR THE NECESSARY TENDER PROCEDURES TO BE COMPLETED DURING NORMAL BUSINESS HOURS PRIOR TO THE EXPIRATION OF THE OFFER. PLEASE READ THIS ENTIRE LETTER OF TRANSMITTAL AND CONSENT, INCLUDING THE INSTRUCTIONS, CAREFULLY BEFORE COMPLETING THIS LETTER OF TRANSMITTAL.** 

The Offeror will not accept any alternative, conditional or contingent tenders, and no fractional shares of Series C Preferred Stock will be accepted for exchange. By executing this letter of transmittal (or a manual facsimile thereof) or transmitting an Agent's Message, the tendering stockholder waives any right to receive any notice of the acceptance for exchange of the tendered shares of Series C Preferred Stock.

&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; **3. Guaranteed Delivery.** Holders of Series C Preferred Stock desiring to tender shares pursuant to the Offer but whose shares of Series C Preferred Stock cannot otherwise be delivered with all other required documents to the Exchange Agent prior to the Expiration Date may nevertheless tender shares of Series C Preferred Stock, as long as all of the following conditions are satisfied:

&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; (a) the tender must be made by or through an eligible institution (as described in Instruction 1);

------

&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;

&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; (b) the Exchange Agent receives by hand, mail, overnight courier, facsimile or electronic mail transmission, at its address set forth in this letter of transmittal, prior to the Expiration Date, a properly completed and duly executed Notice of Guaranteed Delivery in the form provided by the Company to the undersigned with this letter of transmittal (with any required signature guarantees); and

&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; (c) a confirmation of a book-entry transfer into the Exchange Agent's account at DTC of all shares of Series C Preferred Stock delivered electronically, in each case together with a properly completed and duly executed letter of transmittal with any required signature guarantees (or, in the case of a book-entry transfer without delivery of a letter of transmittal, an Agent's Message in accordance with ATOP), and any other documents required by this letter of transmittal, must be received by the Exchange Agent within two business days after the date the Exchange Agent receives such Notice of Guaranteed Delivery, all as provided in the Prospectus/Consent Solicitation/Offer to Exchange.

A holder of shares of Series C Preferred Stock may deliver the Notice of Guaranteed Delivery by facsimile transmission, e-mail or mail to the Exchange Agent.

Except as specifically permitted by the Prospectus/Consent Solicitation/Offer to Exchange, no alternative or contingent exchanges will be accepted.

&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; **4. Inadequate Space**. If the space provided herein under "Description of Shares Tendered" is inadequate, the number of shares of Series C Preferred Stock tendered should be listed on a separate signed schedule and attached hereto.

5. Signatures; Stock Powers.

&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; (a) *Exact Signatures*. If this letter of transmittal is signed by the registered holder(s) of the shares of Series C Preferred Stock tendered hereby, the signature(s) must correspond with the name(s) as written on the security position listing evidencing such shares of Series C Preferred Stock without any change whatsoever.

&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; (b) *Joint Holders*. If any of the shares of Series C Preferred Stock tendered hereby are held of record by two or more persons, all such persons must sign this letter of transmittal.

&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; (c) *Different Names*. If any of the shares of Series C Preferred Stock tendered hereby are registered in different names, it will be necessary to complete, sign and submit as many separate letters of transmittal as there are different registrations of such shares of Series C Preferred Stock.

&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; (d) *Stock Powers*. If this letter of transmittal is signed by the registered holder(s) of the shares of Series C Preferred Stock tendered hereby, no separate stock powers are required unless the shares of Common Stock are to be issued to a person other than the registered holder(s). In all other cases, such stock powers are required, and signatures on any such stock powers must be guaranteed by an eligible institution as described under Instruction 1.

If this letter of transmittal or any stock power is executed by a trustee, executor, administrator, guardian, attorney-in-fact, officer of a corporation or other person acting in a fiduciary or representative capacity, such person should so indicate when signing, and proper evidence satisfactory to the Offeror of such person so to act must be submitted.

&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; **6. Transfer Taxes**. Except as otherwise provided in this Instruction 6, the Offeror or any successor entity thereto or designated affiliate thereof will pay any stock transfer tax with respect to the transfer of any shares of Series C Preferred Stock to it pursuant to the Offer (for the avoidance of doubt, transfer taxes do not include U.S. federal income or withholding taxes). If, however, the consideration is to be paid to, or if security position listing(s) evidencing shares of Series C Preferred Stock not tendered or not accepted for exchange are to be issued in the name of, any person other than the registered holder(s), or if tendered security position listing(s) evidencing shares of Series C Preferred Stock are registered in the name of any person other than the person(s) signing this letter of transmittal, the Offeror will not be responsible for any transfer or other similar taxes (whether imposed on the registered holder(s) or such other person or otherwise) payable on account of any such issuance or transfer to such other person and no consideration

------

shall be paid or issued in respect of such shares of Series C Preferred Stock pursuant to the offer unless evidence satisfactory to Offeror that such taxes have been paid or are not required to be paid is submitted.

&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; **7. Special Issuance or Payment and Delivery Instructions**. If the certificates for shares of Common Stock (or, at Offeror's election, evidence of book-entry of Common Stock) and any certificates for the shares of Series C Preferred Stock not tendered or not accepted for exchange (and any accompanying documents, as appropriate) are to be issued in the name of and/or delivered to a person other than the registered holder(s) listed above in the box titled "Description of Shares Tendered" or delivered to the registered holder(s) listed above in the box titled "Description of Shares Tendered" at an address other than that listed above in the box titled "Description of Shares Tendered," the appropriate boxes on this letter of transmittal should be completed and the signature will need to be guaranteed as described under Instruction 1.

&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; **8. Tax Withholding**. In order to avoid backup withholding, each Offeror stockholder that is a United States person within the meaning of the Internal Revenue Code of 1986, as amended (a "United States person"), and, if applicable, each other payee that is a United States person, must provide the Exchange Agent with such stockholder's or payee's correct taxpayer identification number ("TIN") and certify that such stockholder or payee is not subject to backup withholding by completing the enclosed IRS Form W-9 or otherwise establish a basis for exemption from backup withholding. If the Exchange Agent is not provided with such stockholder's or payee's correct TIN or an adequate basis for exemption from backup withholding before payment is made, payments of cash made to such stockholder or payee may be subject to backup withholding at the applicable rate and such stockholder or payee may be subject to a penalty imposed by the Internal Revenue Service (the "IRS"). See the enclosed IRS Form W-9 and the instructions thereto for additional information.

Certain stockholders or payees (including, among others, corporations and certain foreign persons) are not subject to backup withholding. An Offeror stockholder or other payee that is not a United States person may qualify as an exempt recipient for purposes of United States federal backup withholding by providing the Exchange Agent with a properly completed IRS Form W-8BEN or IRS Form W-8BEN-E, as applicable, or other appropriate IRS Form W-8, signed under penalties of perjury, attesting to such stockholder's foreign status or by otherwise establishing an exemption. An appropriate IRS Form W-8 may be obtained from the Exchange Agent or the IRS website (*www.irs.gov*). Failure to complete IRS Form W-9 or the appropriate IRS Form W-8 will not, by itself, cause shares of Series C Preferred Stock to be deemed invalidly tendered, but may require the Exchange Agent to withhold from the cash amounts paid pursuant to the offer. Backup withholding is not an additional tax. Rather, the U.S. federal income tax liability, if any, of a person subject to backup withholding will be reduced by the amount of tax withheld. If backup withholding results in the overpayment of taxes, a payee may claim a refund or credit by timely submitting the required information to the IRS. Tax matters can be complicated, and the tax consequences of the Offer to a particular stockholder will depend on such stockholder's particular facts and circumstances. Offeror stockholders should consult their own tax advisors to determine the specific consequences to them of tendering their shares of Series C Preferred Stock pursuant to the offer.

 **FAILURE TO COMPLETE AND RETURN THE ENCLOSED IRS FORM W-9 OR THE APPROPRIATE IRS FORM W-8 MAY RESULT IN BACKUP WITHHOLDING FROM THE CASH AMOUNTS PAID PURSUANT TO THE OFFER.** 

#### IRS CIRCULAR 230 DISCLOSURE
 **TO ENSURE COMPLIANCE WITH REQUIREMENTS IMPOSED BY THE IRS, WE INFORM YOU THAT ANY UNITED STATES TAX ADVICE CONTAINED IN THIS LETTER OF TRANSMITTAL (INCLUDING ANY ATTACHMENTS) IS NOT INTENDED OR WRITTEN TO BE USED, AND CANNOT BE USED, FOR THE PURPOSE OF (I) AVOIDING PENALTIES UNDER THE INTERNAL REVENUE CODE OR (II) PROMOTING, MARKETING OR RECOMMENDING TO ANOTHER PARTY ANY MATTERS ADDRESSED HEREIN.** 

&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; **9. Requests for Additional Copies**. Questions and requests for assistance or additional copies of the Prospectus/Consent Solicitation/Offer to Exchange and this letter of transmittal should be directed to the information agent at its address and telephone number set forth on the back page of this letter of transmittal. Stockholders may also contact their brokers, dealers, commercial banks, trust companies or other nominees for assistance concerning the offer.

------

&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;

&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; **10. Waiver of Conditions**. The Offeror reserves the absolute right to waive any condition of the Offer to the extent permitted by applicable law except as specified in the Prospectus/Consent Solicitation/Offer to Exchange.

&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; **11. Irregularities**. All questions as to form, validity, eligibility (including time of receipt) and acceptance for exchange of any tender of shares of Series C Preferred Stock and any notice of withdrawal will be determined by the Offeror in its sole discretion, which determinations shall be final and binding to the fullest extent permitted by law. The Offeror reserves the absolute right to reject any or all tenders of shares of Series C Preferred Stock it determines not to be in proper form or the acceptance of or exchange for which may, in the opinion of Offeror's counsel, be unlawful. The Offeror also reserves the absolute right to waive any defect or irregularity in the tender of any shares of Series C Preferred Stock of any particular stockholder, whether or not similar defects or irregularities are waived in the case of other stockholders. No tender of shares of Series C Preferred Stock will be deemed to be properly made until all defects and irregularities with respect thereto have been cured or waived. Unless waived, any defects or irregularities in connection with tenders must be cured within such time as the Offeror shall determine. None of the Offeror, Viskase, their respective affiliates and associates, the Exchange Agent, the information agent or any other person is or will be obligated to give notice of any defects or irregularities in tenders of shares of Series C Preferred Stock, or to waive any such defect or irregularity, and none of them will incur any liability for failure to give any such notice or waiver. The Offeror's interpretation of the terms and conditions of the offer, including this letter of transmittal, will be final and binding to the fullest extent permitted by law.

IMPORTANT: THIS LETTER OF TRANSMITTAL, TOGETHER WITH ANY SIGNATURE GUARANTEES, OR, IN THE CASE OF A BOOK-ENTRY TRANSFER, AN AGENT'S MESSAGE, AND ANY OTHER REQUIRED DOCUMENTS, MUST BE RECEIVED BY THE EXCHANGE AGENT PRIOR TO THE EXPIRATION OF THE OFFER OR SHARES MUST BE DELIVERED PURSUANT TO THE PROCEDURES FOR BOOK-ENTRY TRANSFER, IN EACH CASE PRIOR TO THE EXPIRATION OF THE OFFER.

Facsimiles of this letter of transmittal, properly completed and duly signed, will be accepted. In such case, a copy of this letter of transmittal and any other required documents should be sent or delivered by each stockholder or such stockholder's broker, dealer, commercial bank, trust company or other nominee to the Exchange Agent at one of its addresses set forth herein.

If the Offeror becomes aware of any jurisdiction in which the making of the Offer or the tender of shares of Series C Preferred Stock in connection therewith would not be in compliance with applicable law, the Offeror will make a good faith effort to comply with any such law. If, after such good faith effort, the Offeror cannot comply with any such law, the Offer will not be made to (nor will tenders be accepted from or on behalf of) the holders of shares of Series C Preferred Stock in such jurisdiction. In any jurisdiction where the securities, blue sky or other laws require the Offer to be made by a licensed broker or dealer, the Offer shall be deemed to be made on behalf of the Offeror by one or more registered brokers or dealers licensed under the laws of such jurisdiction.

------

#### The Depositary & Exchange Agent for the offer is:
![[MISSING IMAGE: lg_continental-bwlr.jpg]](lg_continental-bwlr.jpg)

---

| | |
|:---|:---|
| *<u>If delivering by mail:</u>* <br> Continental Stock Transfer & Trust Company, <br> Attn: Corporate Actions, <br> 1 State Street 30th Floor, New York, NY 10004 <br> Telephone: 800-509-5586  | *<u>If delivering by hand, express mail, courier</u>* <br> *<u>or any other expedited service:</u>* <br> Continental Stock Transfer & Trust Company, <br> Attn: Corporate Actions, <br> 1 State Street 30th Floor, New York, NY 10004 <br> Telephone: 800-509-5586  |

---

Questions or requests for assistance may be directed to the information agent at its address and telephone number set forth below. Requests for additional copies of the Prospectus/Consent Solicitation/Offer to Exchange and this letter of transmittal may be directed to the information agent at the address and telephone number set forth below. Stockholders may also contact their broker, dealer, commercial bank or trust company for assistance concerning the offer.

#### The information agent for the offer is:

#### HKL & Co., LLC
3 Columbus Circle, 15th Floor

New York, NY 10019

Banks and Brokerage Firms Please Call Collect: +1 (212) 468-5380

All Others Call Toll-Free: +1 (800) 326-5997

Email: enzn@hklco.com

------

## Exhibit 99.10

#### Exhibit 99.10

#### NOTICE OF GUARANTEED DELIVERY OF SHARES OF SERIES C PREFERRED STOCK OF ENZON PHARMACEUTICALS, INC.

#### Pursuant to the Prospectus/Consent Solicitation/Offer to Exchange, dated January 28, 2026

#### Instructions for Use
Unless defined herein, terms used in this Notice of Guaranteed Delivery shall have definitions set forth in the Prospectus/Consent Solicitation/Offer to Exchange, dated January 28, 2026, filed with the U.S. Securities and Exchange Commission on January 28, 2026.

This Notice of Guaranteed Delivery, or one substantially in the form hereof, must be used to accept the Offer if:

&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; • the procedure for book-entry transfer cannot be completed on a timely basis; or

&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; • time will not permit all required documents, including a properly completed and duly executed Letter of Transmittal and any other required documents, to reach Continental Stock Transfer & Trust Company (the "Exchange Agent") prior to the Expiration of the Offer.

 *This Notice of Guaranteed Delivery, properly completed and duly executed, must be delivered by hand, mail, overnight courier, facsimile or electronic mail transmission to the Exchange Agent, as described in the section of the Prospectus/Consent Solicitation/Offer to Exchange entitled "Series C Exchange Offer — Procedure for Tendering Shares of Enzon Series C Preferred Stock — Guaranteed Delivery Procedures." The method of delivery of all required documents is at the holder's option and risk.* 

For this Notice of Guaranteed Delivery to be validly delivered, it must be *received* by the Exchange Agent at the address below prior to the Expiration of the Offer. Delivery of this notice to another address will not constitute a valid delivery. If delivered to the Offeror, the information agent or the book-entry transfer facility, a Notice of Guaranteed Delivery will not be forwarded to the Exchange Agent and such delivery to the Offeror, the information agent or the book-entry transfer facility, as the case may be, will not constitute a valid delivery.

The signature of the holder of Series C Preferred Stock on this Notice of Guaranteed Delivery must be guaranteed by an "Eligible Institution," and the Eligible Institution must also execute the Guarantee of Delivery attached hereto. An "Eligible Institution" is a bank, broker, dealer, credit union, savings association or other entity that is a member in good standing of the Securities Transfer Agents Medallion Program or a bank, broker, dealer, credit union, savings association or other entity which is an "eligible guarantor institution," as that term is defined in Rule 17Ad-15 promulgated under the Securities Exchange Act of 1934, as amended.

 **In addition, if the instructions to the Letter of Transmittal require a signature on a Letter of Transmittal to be guaranteed by an eligible institution, such signature guarantee must appear in the applicable space provided in the signature box on the Letter of Transmittal.** 

------

#### NOTICE OF GUARANTEED DELIVERY OF SHARES OF SERIES C PREFERRED STOCK OF ENZON PHARMACEUTICALS, INC.

#### Pursuant to the Prospectus/Consent Solicitation/Offer to Exchange, dated January 28, 2026

#### TO: CONTINENTAL STOCK TRANSFER & TRUST COMPANY
1 State Street, 30th Floor

New York, NY 10004

Attention: Corporate Actions Department

The undersigned acknowledges receipt of the Prospectus/Consent Solicitation/Offer to Exchange, dated January 28, 2026 (the "Prospectus/Consent Solicitation/Offer to Exchange"), and the related Letter of Transmittal (the "Letter of Transmittal").

By signing this Notice of Guaranteed Delivery, the holder tenders for exchange, upon the terms and subject to the conditions described in the Prospectus/Consent Solicitation/Offer to Exchange and in the Letter of Transmittal, the number of shares of Series C Non-Convertible Redeemable Preferred Stock, $0.01 par value per share (the "Series C Preferred Stock"), of Enzon Pharmaceuticals, Inc. specified below, pursuant to the guaranteed delivery procedures described in the section of the Prospectus/Consent Solicitation/Offer to Exchange entitled "*Series C Exchange Offer — Procedure for Tendering Shares of Enzon Series C Preferred Stock — Guaranteed Delivery Procedures*."

#### DESCRIPTION OF SHARES OF SERIES C PREFERRED STOCK TENDERED
List below the shares of Series C Preferred Stock to which this Notice of Guaranteed Delivery relates.

---

| | |
|:---|:---|
| **Name(s) and Address(es) of Registered Holder(s) of Shares of <br> Preferred Stock** | **Number of Shares of Preferred Stock Tendered**  |
|  | **Total: <br>**  |

---

(1) Unless otherwise indicated above, it will be assumed that all shares of Series C Preferred Stock listed above are being tendered pursuant to this Notice of Guaranteed Delivery.

☐

CHECK HERE IF THE SHARES OF SERIES C PREFERRED STOCK LISTED ABOVE WILL BE DELIVERED BY BOOK-ENTRY TRANSFER MADE TO THE ACCOUNT MAINTAINED BY THE EXCHANGE AGENT WITH THE DEPOSITORY TRUST COMPANY ("DTC") AND COMPLETE THE FOLLOWING (FOR USE BY ELIGIBLE INSTITUTIONS ONLY):

Name of Tendering Institution:

Account Number:

------

#### SIGNATURES

---

| |
|:---|
| Signature(s) of Preferred Stock Holder(s) |
| Name(s) of Preferred Stock Holder(s) (Please Print) |
| Address |
| City, State, Zip Code |
| Telephone Number |
| Date  |

---

#### GUARANTEE OF SIGNATURES

---

| |
|:---|
| Authorized Signature |
| Name (Please Print) |
| Title |
| Name of Firm (must be an Eligible Institution as defined in this Notice of Guaranteed Delivery) |
| Address |
| City, State, Zip Code |
| Telephone Number |
| Date  |

---

------

#### GUARANTEE OF DELIVERY (Not to be used for Signature Guarantee)
The undersigned, a bank, broker, dealer, credit union, savings association or other entity that is a member in good standing of the Securities Transfer Agents Medallion Program or a bank, broker, dealer, credit union, savings association or other entity which is an "eligible guarantor institution," as that term is defined in Rule 17Ad-15 promulgated under the Securities Exchange Act of 1934, as amended (each of the foregoing constituting an "Eligible Institution"), guarantees delivery to the Exchange Agent of the shares of Series C Preferred Stock tendered in proper form for transfer, or a confirmation that the shares of Series C Preferred Stock tendered have been delivered pursuant to the procedure for book-entry transfer described in the Prospectus/Consent Solicitation/Offer to Exchange and the Letter of Transmittal into the Exchange Agent's account at the book-entry transfer facility, in each case together with a properly completed and duly executed Letter(s) of Transmittal, or an Agent's Message in the case of a book-entry transfer, and any other required documents, all within one (1) Over-the-Counter Bulletin Board quotation days after the date of receipt by the Exchange Agent of this Notice of Guaranteed Delivery.

The Eligible Institution that completes this form must communicate the guarantee to the Exchange Agent and must deliver the Letter of Transmittal to the Exchange Agent, or confirmation of receipt of the shares of Series C Preferred Stock pursuant to the procedure for book-entry transfer and an Agent's Message, within the time set forth above. Failure to do so could result in a financial loss to such Eligible Institution.

---

| |
|:---|
| Authorized Signature Name (Please Print) |
| Title |
| Name of Firm |
| Address |
| City, State, Zip Code |
| Telephone Number |
| Date  |

---

------

## Exhibit 99.11

#### Exhibit 99.11

#### LETTER TO BROKERS, DEALERS, COMMERCIAL BANKS, TRUST COMPANIES AND OTHER NOMINEES

#### Offer To Exchange Shares of Series C Preferred Stock of Enzon Pharmaceuticals, Inc. for Shares of Common Stock of Enzon Pharmaceuticals, Inc.
 **THE OFFER (AS DEFINED BELOW) AND WITHDRAWAL RIGHTS WILL EXPIRE AT ONE MINUTE AFTER 11:59 P.M., EASTERN TIME, ON FEBRUARY 27, 2026, OR SUCH LATER TIME AND DATE TO WHICH WE MAY EXTEND. THE SHARES OF SERIES C PREFERRED STOCK (AS DEFINED BELOW) TENDERED PURSUANT TO THE OFFER MAY BE WITHDRAWN PRIOR TO THE EXPIRATION DATE (AS DEFINED BELOW). CONSENTS MAY BE REVOKED ONLY BY WITHDRAWING THE TENDER OF THE RELATED SHARES OF SERIES C PREFERRED STOCK AND THE WITHDRAWAL OF ANY SHARES OF SERIES C PREFERRED STOCK WILL AUTOMATICALLY CONSTITUTE A REVOCATION OF THE RELATED CONSENTS.** 

January 30, 2026

#### To Brokers, Dealers, Commercial Banks, Trust Companies and Other Nominees:
Enclosed are the Prospectus/Consent Solicitation/Offer to Exchange, dated January 28, 2026 (the "Prospectus/Consent Solicitation/Offer to Exchange"), and the related Letter of Transmittal (the "Letter of Transmittal"), which together set forth the offer by Enzon Pharmaceuticals, Inc., a Delaware corporation (the "Company," the "Offeror," "we," "our" and "us"), to each holder of outstanding shares of Series C Non-Convertible Redeemable Preferred Stock, $0.01 par value per share (the "Series C Preferred Stock"), of the Company, the opportunity to receive that number of shares of common stock, $0.01 par value per share ("Common Stock"), equal to (i) the aggregate liquidation preference of each share of Series C Preferred Stock, divided by (ii) $7.83 after giving effect to the Reverse Stock Split (as defined in the Prospectus/Consent Solicitation/Offer to Exchange) (the "Exchange Ratio," and such offer, on the terms and subject to the conditions and procedures set forth in the Prospectus/Consent Solicitation/Offer to Exchange and the Letter of Transmittal, together with any amendments or supplements thereto, the "Offer"). The Offer is made solely upon the terms and conditions in the Prospectus/Consent Solicitation/Offer to Exchange and in the Letter of Transmittal. The Offer will expire at one minute after 11:59 p.m., Eastern Time, on February 27, 2026, or such later time and date to which the Company may extend the Offer. The period during which the Offer is open, giving effect to any withdrawal or extension, is referred to as the "Offer Period." The date and time at which the Offer Period ends is referred to as the "Expiration Date." Unless defined herein, terms used in this Letter to Brokers, Dealers, Commercial Banks, Trust Companies and Other Nominees shall have definitions set forth in the Prospectus/Consent Solicitation/Offer to Exchange.

The Offer is being made to all holders of Series C Preferred Stock. The Series C Preferred Stock is governed by the Certificate of Designation, dated September 21, 2020. The Series C Preferred Stock is not listed on a securities exchange nor traded in an over-the-counter market. As of January 30, 2026, a total of 40,000 shares of Series C Preferred Stock were outstanding.

Each holder of Series C Preferred Stock whose shares of Series C Preferred Stock are exchanged pursuant to the Offer will receive that number of shares of Common Stock calculated pursuant to the Exchange Ratio.

No fractional shares of Common Stock will be issued. Instead, holders will receive a cash payment in lieu of fractional shares. The Company's obligation to complete the Offer is not conditioned on the receipt of a minimum number of tendered shares of Series C Preferred Stock.

------

The Offer is conditioned upon the satisfaction or waiver of all of the conditions to the consummation of the Merger set forth in the Agreement and Plan of Merger, dated June 20, 2025 by and among the Offeror, EPSC Acquisition Corp. ("EPSC") and Viskase Companies Inc. ("Viskase") (the "Original Merger Agreement"), as amended by the First Amendment to the Agreement and Plan of Merger, dated October 24, 2025, by and among the Offeror, EPSC and Viskase (the "First Amendment to the Merger Agreement," and as amended, the "Merger Agreement"), including, without limitation, the receipt by Enzon of the requisite written consent of holders of its Common Stock approving the Merger and the other transactions contemplated by the Merger Agreement. The Offeror intends to complete the Offer substantially concurrently with the consummation of the Merger. Holders of Series C Preferred Stock may withdraw any shares of Series C Preferred Stock tendered by them into the Offer at any time prior to the Expiration Date.

Shares of Series C Preferred Stock not exchanged for shares of our Common Stock pursuant to the Offer will remain outstanding subject to their current terms. We reserve the right to redeem any of the shares of Series C Preferred Stock, as applicable, pursuant to their current terms at any time, including prior to the completion of the Offer.

 **WE ARE NOT AWARE OF ANY U.S. STATE WHERE THE MAKING OF THE OFFER IS NOT IN COMPLIANCE WITH APPLICABLE LAW. IF WE BECOME AWARE OF ANY U.S. STATE WHERE THE MAKING OF THE OFFER OR THE ACCEPTANCE OF THE SHARES OF SERIES C PREFERRED STOCK PURSUANT TO THE OFFER IS NOT IN COMPLIANCE WITH APPLICABLE LAW, WE WILL MAKE A GOOD FAITH EFFORT TO COMPLY WITH THE APPLICABLE LAW. IF, AFTER SUCH GOOD FAITH EFFORT, WE CANNOT COMPLY WITH THE APPLICABLE LAW, THE OFFER WILL NOT BE MADE TO (NOR WILL TENDERS BE ACCEPTED FROM OR ON BEHALF OF) HOLDERS OF SERIES C PREFERRED STOCK.** 

Enclosed with this letter are copies of the following documents:

&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; 1.

The Prospectus/Consent Solicitation/Offer to Exchange;

&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; 2.

The Letter of Transmittal, for your use in accepting the Offer, tendering shares of Series C Preferred Stock for exchange and for the information of your clients for whose accounts you hold shares of Series C Preferred Stock registered in your name or in the name of your nominee. Manually signed copies of the Letter of Transmittal may be used to tender shares of Series C Preferred Stock and provide consent;

&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; 3.

The Notice of Guaranteed Delivery to be used to accept the Offer in the event (i) the procedure for book-entry transfer cannot be completed on a timely basis or (ii) time will not permit all required documents to reach Continental Stock Transfer & Trust Company (the "Exchange Agent") prior to the Expiration Date;

&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; 4.

A form of letter which may be sent by you to your clients for whose accounts you hold shares of Series C Preferred Stock registered in your name or in the name of your nominee, including an Instructions Form provided for obtaining each such client's instructions with regard to the Offer; and

&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; 5.

A return envelope addressed to Exchange Agent.

 **Certain conditions to the Offer are described in the section of the Prospectus/Consent Solicitation/Offer to Exchange entitled "*Series C Exchange Offer — Conditions of the Series C Exchange Offer*."** 

 **We urge you to contact your clients promptly. Please note that the Offer and withdrawal rights will expire at one minute after 11:59 p.m., Eastern Time, on February 27, 2026, or such later time and date to which the Company may extend the Offer.** 

The Company will not pay any fees or commissions to any broker, dealer or other person (other than the Exchange Agent, the information agent, dealer manager and solicitation agent and certain other persons, as described in the sections of the Prospectus/Consent Solicitation/Offer to Exchange entitled "*Series C Exchange Offer — Fees and Expenses*") for soliciting tenders of shares of Series C Preferred Stock pursuant to the Offer. However, the Company will, on request, reimburse you for customary clerical and mailing

------

expenses incurred by you in forwarding copies of the enclosed materials to your clients for whose accounts you hold shares of Series C Preferred Stock.

Any questions you have regarding the Offer should be directed to, and additional copies of the enclosed materials may be obtained from, the information agent in the Offer:

 *The Information Agent for the Offer is:* 

**HKL & Co., LLC** 

3 Columbus Circle, 15th Floor

New York, NY 10019

Banks and Brokerage Firms Please Call Collect: +1 (212) 468-5380

All Others Call Toll-Free: +1 (800) 326-5997

Email: enzn@hklco.com

Very truly yours,

Enzon Pharmaceuticals, Inc.

 **Nothing contained in this letter or in the enclosed documents shall constitute you or any other person the agent of the Company, the Exchange Agent, the dealer manager and solicitation agent, the information agent or any affiliate of any of them, or authorize you or any other person to give any information or use any document or make any statement on behalf of any of them in connection with the Offer other than the enclosed documents and the statements contained therein.** 

------

## Exhibit 99.12

#### Exhibit 99.12

#### LETTER TO CLIENTS OF BROKERS, DEALERS, COMMERCIAL BANKS, TRUST COMPANIES AND OTHER NOMINEES

#### Offer To Exchange Shares of Series C Preferred Stock of Enzon Pharmaceuticals, Inc. for Shares of Common Stock of Enzon Pharmaceuticals, Inc.
 **THE OFFER (AS DEFINED BELOW) AND WITHDRAWAL RIGHTS WILL EXPIRE AT ONE MINUTE AFTER 11:59 P.M., EASTERN TIME, ON FEBRUARY 27, 2026, OR SUCH LATER TIME AND DATE TO WHICH WE MAY EXTEND. THE SHARES OF SERIES C PREFERRED STOCK (AS DEFINED BELOW) TENDERED PURSUANT TO THE OFFER MAY BE WITHDRAWN PRIOR TO THE EXPIRATION DATE (AS DEFINED BELOW). CONSENTS MAY BE REVOKED ONLY BY WITHDRAWING THE TENDER OF THE RELATED SHARES OF SERIES C PREFERRED STOCK AND THE WITHDRAWAL OF ANY SHARES OF SERIES C PREFERRED STOCK WILL AUTOMATICALLY CONSTITUTE A REVOCATION OF THE RELATED CONSENTS.** 

January 30, 2026

#### To Our Clients:
Enclosed are the Prospectus/Consent Solicitation/Offer to Exchange dated January 28, 2026 (the "Prospectus/Consent Solicitation/Offer to Exchange"), and the related Letter of Transmittal (the "Letter of Transmittal"), which together set forth the offer by Enzon Pharmaceuticals, Inc., a Delaware corporation (the "Company" or the "Offeror"), to each holder of outstanding shares of Series C Non-Convertible Redeemable Preferred Stock, $0.01 par value per share (the "Series C Preferred Stock"), of the Company, of the opportunity to receive that number of shares of common stock, $0.01 par value per share ("Common Stock"), equal to (i) the aggregate liquidation preference of each share of Series C Preferred Stock, divided by (ii) $7.83 after giving effect to the Reverse Stock Split (as defined in the Prospectus/Consent Solicitation/Offer to Exchange) (the "Exchange Ratio," and such offer, on the terms and subject to the conditions and procedures set forth in the Prospectus/Consent Solicitation/Offer to Exchange and the Letter of Transmittal, together with any amendments or supplements thereto, the "Offer").

The Offer is made solely upon the terms and conditions in the Prospectus/Consent Solicitation/Offer to Exchange and in the Letter of Transmittal. The Offer will expire at one minute after 11:59 p.m., Eastern Time, on February 27, 2026, or such later time and date to which the Company may extend the Offer. The period during which the Offer is open, giving effect to any withdrawal or extension, is referred to as the "Offer Period." The date and time at which the Offer Period ends is referred to as the "Expiration Date." Unless defined herein, terms used in this Letter to Clients of Brokers, Dealers, Commercial Banks, Trust Companies and Other Nominees shall have definitions set forth in the Prospectus/Consent Solicitation/Offer to Exchange.

The shares of Series C Preferred Stock are not listed on a securities exchange nor traded in an over-the-counter market. As of January 30, 2026, a total of 40,000 shares of Series C Preferred Stock were outstanding.

Each holder of Series C Preferred Stock whose shares of Series C Preferred Stock are exchanged pursuant to the Offer will receive that number of shares of Common Stock calculated pursuant to the Exchange Ratio. Any holder of Series C Preferred Stock that participates in the Offer may tender less than all of their shares of Series C Preferred Stock for exchange.

No fractional shares of Common Stock will be issued. Instead, holders will receive a cash payment in lieu of fractional shares. The Company's obligation to complete the Offer is not conditioned on the receipt of a minimum number of tendered shares of Series C Preferred Stock.

------

The Offer is conditioned upon the satisfaction or waiver of all of the conditions to the consummation of the Merger set forth in the Agreement and Plan of Merger, dated June 20, 2025 by and among the Offeror, EPSC Acquisition Corp. ("EPSC") and Viskase Companies, Inc. ("Viskase") (the "Original Merger Agreement"), as amended by the First Amendment to the Agreement and Plan of Merger, dated October 24, 2025, by and among the Offeror, EPSC and Viskase (the "First Amendment to the Merger Agreement," and, as amended, the "Merger Agreement"), including, without limitation, the receipt by Enzon of the requisite written consent of holders of its Common Stock approving the Merger and the other transactions contemplated by the Merger Agreement. The Offeror intends to complete the Offer substantially concurrently with the consummation of the Merger. Holders of Series C Preferred Stock may withdraw any shares of Series C Preferred Stock tendered by them into the Offer at any time prior to the Expiration Date.

Shares of Series C Preferred Stock not exchanged for shares of our Common Stock pursuant to the Offer will remain outstanding subject to their current terms. We reserve the right to redeem any of the shares of Series C Preferred Stock, as applicable, pursuant to their current terms at any time, including prior to the completion of the Offer.

 **WE ARE NOT AWARE OF ANY U.S. STATE WHERE THE MAKING OF THE OFFER IS NOT IN COMPLIANCE WITH APPLICABLE LAW. IF WE BECOME AWARE OF ANY U.S. STATE WHERE THE MAKING OF THE OFFER OR THE ACCEPTANCE OF THE SHARES OF SERIES C PREFERRED STOCK PURSUANT TO THE OFFER IS NOT IN COMPLIANCE WITH APPLICABLE LAW, WE WILL MAKE A GOOD FAITH EFFORT TO COMPLY WITH THE APPLICABLE LAW. IF, AFTER SUCH GOOD FAITH EFFORT, WE CANNOT COMPLY WITH THE APPLICABLE LAW, THE OFFER WILL NOT BE MADE TO (NOR WILL TENDERS BE ACCEPTED FROM OR ON BEHALF OF) HOLDERS OF SERIES C PREFERRED STOCK.** 

 *Please follow the instructions in this document and the related documents, including the accompanying Letter of Transmittal, to cause your shares of Series C Preferred Stock to be tendered for exchange pursuant to the Offer.* 

On the terms and subject to the conditions of the Offer, the Company will allow the exchange of all shares of Series C Preferred Stock properly tendered before the Expiration Date and not properly withdrawn, at an exchange rate equal to the Exchange Ratio.

We are the owner of record of shares of Series C Preferred Stock held for your account. As such, only we can exchange and tender your shares of Series C Preferred Stock, and then only pursuant to your instructions. We are sending you the Letter of Transmittal for your information only; you cannot use it to exchange and tender shares of Series C Preferred Stock we hold for your account. Please instruct us as to whether you wish us to tender for exchange any or all of the shares of Series C Preferred Stock we hold for your account, on the terms and subject to the conditions of the Offer.

Please note the following:

&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; 1.

Your shares of Series C Preferred Stock may be exchanged at the exchange rate equal to the Exchange Ratio.

&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; 2.

The Offer is made solely upon the terms and conditions set forth in the Prospectus/Consent Solicitation/Offer to Exchange and in the Letter of Transmittal. In particular, please see "*Series C Exchange Offer — Conditions of the Series C Exchange Offer*" in the Prospectus/Consent Solicitation/Offer to Exchange.

&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; 3.

The Offer and withdrawal rights will expire at one minute after 11:59 p.m., Eastern Time, on February 27, 2026, or such later time and date to which the Company may extend the Offer.

 **If you wish to have us tender any or all of your shares of Series C Preferred Stock for exchange pursuant to the Offer, please so instruct us by completing, executing, detaching and returning to us the attached Instructions Form. If you authorize us to tender your shares of Series C Preferred Stock, we will tender for exchange all of your shares of Series C Preferred Stock unless you specify otherwise on the attached Instruction Form.** 

------

**Your prompt action is requested. Your Instruction Form should be forwarded to us in ample time to permit us to submit a tender on your behalf before the Expiration Date. Please note that the Offer and withdrawal rights will expire at one minute after 11:59 p.m., Eastern Time, on February 27, 2026, or such later time and date to which the Company may extend the Offer.

An authorized committee of the Board of Directors of the Company has approved the Offer. However, neither the Company nor any of its management, its Board of Directors, the information agent, or the exchange agent for the Offer is making any recommendation as to whether holders of shares of Series C Preferred Stock should tender shares of Series C Preferred Stock for exchange in the Offer. The Company has not authorized any person to make any recommendation. You should carefully evaluate all information in the Prospectus/Consent Solicitation/Offer to Exchange and in the Letter of Transmittal and should consult your own investment and tax advisors. You must decide whether to have your shares of Series C Preferred Stock exchanged and, if so, how many shares of Series C Preferred Stock to have exchanged. In doing so, you should read carefully the information in the Prospectus/Consent Solicitation/Offer to Exchange and in the Letter of Transmittal.

------**

#### Instructions Form

#### Offer To Exchange Shares of Series C Preferred Stock of Enzon Pharmaceuticals, Inc. for Shares of Common Stock of Enzon Pharmaceuticals, Inc.
The undersigned acknowledges receipt of your letter and the enclosed Prospectus/Consent Solicitation/Offer to Exchange dated January 28, 2026 (the "Prospectus/Consent Solicitation/Offer to Exchange"), and the related Letter of Transmittal (the "Letter of Transmittal"), which together set forth the offer by Enzon Pharmaceuticals, Inc., a Delaware corporation (the "Company" or the "Offeror"), to each holder of outstanding shares of Series C Non-Convertible Redeemable Preferred Stock, $0.01 par value per share (the "Series C Preferred Stock"), of the Company, of the opportunity to receive that number of shares of common stock, $0.01 par value per share ("Common Stock"), equal to (i) the aggregate liquidation preference of each share of Series C Preferred Stock, divided by (ii) $7.83 after giving effect to the Reverse Stock Split (as defined in the Prospectus/Consent Solicitation/Offer to Exchange) (the "Exchange Ratio," and such offer, on the terms and subject to the conditions and procedures set forth in the Prospectus/Consent Solicitation/Offer to Exchange and the Letter of Transmittal, together with any amendments or supplements thereto, the "Offer").

 **The undersigned hereby instructs you to tender for exchange the number of shares of Series C Preferred Stock indicated below or, if no number is indicated, all shares of Series C Preferred Stock you hold for the account of the undersigned, on the terms and subject to the conditions set forth in the Prospectus/Consent Solicitation/Offer to Exchange and in the Letter of Transmittal.** 

By participating in the Offer, the undersigned acknowledges that: (i) the Offer is made solely upon the terms and conditions in the Prospectus/Consent Solicitation/Offer to Exchange and in the Letter of Transmittal; (ii) the Offer will expire at one minute after 11:59 p.m., Eastern Time, on February 27, 2026, or such later time and date to which the Company may extend the Offer (the period during which the Offer is open, giving effect to any withdrawal or extension, is referred to as the "Offer Period"); (iii) the Offer may be extended, modified, suspended or terminated by the Company as provided in the Prospectus/Consent Solicitation/Offer to Exchange; (iv) the undersigned is voluntarily participating in the Offer and is aware of the conditions of the Offer; (v) the future value of shares of the Common Stock is unknown and cannot be predicted with certainty; (vi) the undersigned has received and read the Prospectus/Consent Solicitation/Offer to Exchange and the Letter of Transmittal; and (vii) regardless of any action that the Company takes with respect to any or all income/capital gains tax, social security or insurance, transfer tax or other tax-related items ("Tax Items") related to the Offer and the disposition of shares of Series C Preferred Stock, the undersigned acknowledges that the ultimate liability for all Tax Items is and remains the responsibility solely of the undersigned. In that regard, the undersigned authorizes the Company to withhold all applicable Tax Items legally payable by the undersigned.

------

#### Number of Shares of Preferred Stock to be exchanged by you for the account of the undersigned:
\*

No fractional shares of Common Stock will be issued pursuant to the Offer. In lieu of issuing fractional shares, any holder of Series C Preferred Stock who would otherwise have been entitled to receive fractional shares pursuant to the Offer will, after aggregating all such fractional shares of such holder, be paid in cash (without interest) in an amount equal to such fractional amount multiplied by the volume weighted averages of the trading prices of Common Stock over 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, in lieu of fractional shares. The Company's obligation to complete the Offer is not conditioned on the receipt of a minimum number of tendered shares of Preferred Stock

\*

Unless otherwise indicated it will be assumed that all shares of Series C Preferred Stock held by us for your account are to be exchanged.

---

| | |
|:---|:---|
| Signature(s): | |
| Name(s): | |
|  | (Please Print)  |
| Taxpayer Identification Number: | |
| Address(es): | |
|  | (Including Zip Code)  |
| Area Code/Phone Number: | |
| Date: | |

---

------

## Exhibit 99.13

**Exhibit 99.13**

**Enzon Announces Commencement of Exchange Offer Relating to Series C Non-Convertible Redeemable Preferred Stock in Connection With Viskase Merger**

**Cranford, New Jersey – January 30, 2026** – Enzon Pharmaceuticals, Inc. (OTCQB: ENZN) ("Enzon" or the "Company"), today announced that it has commenced an exchange offer (the "Offer") involving its Series C Non-Convertible Redeemable Preferred Stock (the "Series C Preferred Stock") identified in the Prospectus/Consent Solicitation/Offer to Exchange (as defined below) in connection with Enzon's previously announced merger with Viskase Companies, Inc. ("Viskase").

**What's Being Offered**

Enzon is offering all holders of outstanding shares of Series C Preferred Stock the chance to exchange their shares for shares of Enzon's common stock, par value $0.01 per share (the "Common Stock"). Each share of Series C Preferred Stock can be exchanged for an amount of Common Stock equal to (i) the aggregate liquidation preference of each share of Series C Preferred Stock, divided by (ii) $7.83 after giving effect to the Reverse Stock Split (as defined in the Prospectus/Consent Solicitation/Offer to Exchange, dated January 28, 2026 (the "Prospectus/Consent Solicitation/Offer to Exchange")).

**Key Dates and Information**

&nbsp;&nbsp;&nbsp;&nbsp;· **Deadline to Participate**: The offer expires
at one minute after 11:59 p.m., Eastern Time, on Friday, February 27, 2026, unless extended.

&nbsp;&nbsp;&nbsp;&nbsp;· Holders of Series C Preferred Stock who
elect to participate in the Offer can withdraw their tendered shares any time before the deadline.

**Offer Details**

The Offer is described in full in the Prospectus/Consent Solicitation/Offer to Exchange, filed with the U.S. Securities and Exchange Commission on January 28, 2026, and the Schedule TO (as defined below), filed with the U.S. Securities and Exchange Commission on January 30, 2026.

&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;· **Common Stock Symbol:** ENZN (quoted on the
 "OTCQB" tier of the OTC market)

&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;· **Preferred Stock:** Not publicly traded;
40,000 shares outstanding as of January 30, 2026

HKL & Co., LLC has been appointed as the Information Agent for the Offer, and Continental Stock Transfer & Trust Company has been appointed as the Exchange Agent. Requests for documents should be directed to HKL & Co., LLC at +1 (800) 326-5997 (for individuals) or +1 (212) 468-5380 (for banks and brokers) or via the following email address: enzn@hklco.com.

**About Enzon Pharmaceuticals, Inc.**

Enzon Pharmaceuticals, Inc., together with its subsidiary, is positioned as a public company acquisition vehicle, that has sought to become an acquisition platform.

**Important Additional Information Has Been Filed with the SEC**

The Offer commenced on January 30, 2026. On January 28, 2026, a registration statement on Form S-4 and preliminary prospectus included therein and an exchange offer statement on Schedule TO (the "Schedule TO"), including an offer to exchange, a letter of transmittal and consent and related documents, were filed with the SEC by the Company. The offer to exchange the outstanding shares of Series C Preferred Stock of the Company will only be made pursuant to the Prospectus/Consent Solicitation/Offer to Exchange and Schedule TO, including related documents filed as a part of the Offer. INVESTORS AND SECURITY HOLDERS ARE URGED TO READ THE PROSPECTUS/CONSENT SOLICITATION/OFFER TO EXCHANGE AND SCHEDULE TO FILED OR TO BE FILED WITH THE SEC CAREFULLY, AS THEY MAY BE AMENDED OR SUPPLEMENTED FROM TIME TO TIME, BECAUSE THEY CONTAIN OR WILL CONTAIN IMPORTANT INFORMATION THAT INVESTORS AND SECURITY HOLDERS SHOULD CONSIDER BEFORE MAKING ANY DECISION REGARDING THE EXCHANGE OFFER, INCLUDING THE TERMS AND CONDITIONS OF THE EXCHANGE OFFER. Investors and security holders may obtain a free copy of these statements (when available) and other documents filed with the SEC at the website maintained by the SEC at www.sec.gov or by directing such requests to HKL & Co., LLC at +1 (800) 326-5997 (for individuals) or +1 (212) 468-5380 (for banks and brokers) or via the following email address: <u>enzn@hklco.com</u>. Investors and security holders may also obtain, at no charge, the documents filed or furnished to the SEC by the Company under the "Investors" section of the Company's website at https://investor.enzon.com/.

**No Offer or Solicitation**

This press release shall not constitute an offer to exchange or the solicitation of an offer to exchange or the solicitation of an offer to purchase any securities, nor shall there be any exchange or sale of securities in any jurisdiction in which such offer, solicitation or sale would be unlawful prior to registration or qualification under the securities laws of any such jurisdiction. The Offer is being made only through the Schedule TO and Prospectus/Consent Solicitation/Offer to Exchange, and the complete terms and conditions of the Offer are set forth in the Schedule TO and Prospectus/Consent Solicitation/Offer to Exchange.

None of the Company, any of its management or its board of directors, or the Information Agent or the Exchange Agent makes any recommendation as to whether or not holders of shares of Series C Preferred Stock should tender shares of Series Preferred Stock for exchange in the Offer.

**Forward-Looking Statements**

*Certain statements contained in this filing may be considered forward-looking statements within the meaning of the U.S. Private Securities Litigation Reform Act of 1995, including statements regarding the proposed transaction involving Enzon and Viskase, the ability to consummate the proposed transaction, the ability to consummate the Offer, the timing of the Expiration Date, and the ability to quote the common stock of the combined company on the "OTCQB" tier of the OTC market of the OTC Markets Group, Inc. Forward-looking statements generally include statements that are predictive in nature and depend upon or refer to future events or conditions, and include words such as "may," "will," "should," "would," "expect," "anticipate," "plan," "likely," "believe," "estimate," "project," "intend," and other similar expressions among others. Statements that are not historical facts are forward-looking statements. Forward-looking statements are based on current beliefs and assumptions that are subject to risks and uncertainties and are not guarantees of future performance. Actual results could differ materially from those contained in any forward-looking statement as a result of various factors, including, without limitation: (i) the risk that the conditions to the closing of the proposed transaction are not satisfied, including the failure to obtain the necessary approvals for the proposed transaction; (ii) uncertainties as to the timing of the consummation of the proposed transaction, including timing for satisfaction of the closing conditions, and the ability of each of Enzon and Viskase to consummate the proposed transaction; (iii) the ability of Viskase to timely deliver the financial statements required by the Merger Agreement, as amended; (iv) the possibility that other anticipated benefits of the proposed transaction will not be realized, including without limitation, anticipated revenues, expenses, earnings and other financial results, and growth and expansion of the combined company's operations, and the anticipated tax treatment of the combination; (v) potential litigation relating to the proposed transaction that could be instituted against Enzon, Viskase or their respective officers or directors; (vi) possible disruptions from the proposed transaction that could harm Enzon's or Viskase's respective businesses; (vii) the ability of Viskase to retain, attract and hire key personnel; (viii) potential adverse reactions or changes to relationships with customers, employees, suppliers or other parties resulting from the announcement or completion of the proposed transaction; (ix) potential business uncertainty, including changes to existing business relationships, during the pendency of the proposed transaction that could affect Enzon's or Viskase's financial performance; (x) certain restrictions during the pendency of the proposed transaction that may impact Enzon's or Viskase's ability to pursue certain business opportunities or strategic transactions; (xi) the exchange ratio and relative ownership levels as of the closing of the transactions contemplated by the Merger Agreement, as amended; (xii) estimates regarding future revenue, expenses, and capital requirements following the closing of the transactions contemplated by the Merger Agreement, as amended; (xiii) legislative, regulatory and economic developments; (xiv) unpredictability and severity of catastrophic events, including, but not limited to, acts of terrorism, trade wars, or outbreak of war or hostilities, as well as management's response to any of the aforementioned factors; and (xv) such other risks and uncertainties, including those that are set forth in the Registration Statement under the heading "Risk Factors", in Enzon's periodic public filings with the SEC, and in Viskase's annual and quarterly reports posted to Viskase's website. Enzon and Viskase can give no assurance that the conditions to the proposed transaction will be satisfied. Except as required by applicable law, neither Enzon, nor Viskase undertakes any obligation to revise or update any forward-looking statement, or to make any other forward-looking statements, whether as a result of new information, future events or otherwise.*

**For Media Inquiries:**

Richard L. Feinstein, CEO and CFO

Email: rlfeinsteincpa@enzon.com