# EDGAR Filing Document

**Accession Number:** 0000727510
**File Stem:** 0001104659-25-124254
**Filing Date:** 2025-12
**Character Count:** 15471
**Document Hash:** 2597375c4b70bce7c715bc6de74d2a58
**Contains OCR:** False
**Source Format:** 

## Filing Content

## Filing Summary
**0001104659-25-124254.hdr.sgml**: 20251223

**ACCESSION NUMBER**: 0001104659-25-124254

**CONFORMED SUBMISSION TYPE**: 8-K

**PUBLIC DOCUMENT COUNT**: 13

**CONFORMED PERIOD OF REPORT**: 20251223

**ITEM INFORMATION**: Entry into a Material Definitive Agreement

**ITEM INFORMATION**: Material Modifications to Rights of Security Holders

**ITEM INFORMATION**: Financial Statements and Exhibits

**FILED AS OF DATE**: 20251223

**DATE AS OF CHANGE**: 20251223

**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:** 8-K
- **SEC ACT:** 1934 Act
- **SEC FILE NUMBER:** 000-12957
- **FILM NUMBER:** 251601317

**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

?xml version='1.0' encoding='ASCII'?

**UNITED STATES**

**SECURITIES AND EXCHANGE COMMISSION**

**Washington, D.C. 20549**

**FORM 8-K**

**CURRENT REPORT**

Pursuant to Section 13 OR 15(d) of The Securities Exchange Act of 1934

Date of Report (Date of earliest event reported): **December 23, 2025**

**ENZON PHARMACEUTICALS, INC.**

(Exact name of registrant as specified in its charter)

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| | | |
|:---|:---|:---|
| **Delaware**<br> (State or other jurisdiction<br> of incorporation) | **001-36435**<br> (Commission File Number) | **22-2372868**<br> (IRS Employer Identification No.) |

---

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| | |
|:---|:---|
| &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; **20 Commerce Drive (Suite 135), Cranford, New Jersey**<br> (Address of principal executive offices) | **07016**<br> (Zip Code) |

---

**(732) 980-4500**

(Registrant's telephone number, including area code)

**Not Applicable**

(Former name or former address, if changed since last report)

Check the appropriate box below if the Form 8-K filing is intended to simultaneously satisfy the filing obligation of the registrant under any of the following provisions:

◻ Written communications pursuant to Rule 425 under the Securities Act (17 CFR 230.425)

◻ Soliciting material pursuant to Rule 14a-12 under the Exchange Act (17 CFR 240.14a-12)

◻ Pre-commencement communications pursuant to Rule 14d-2(b) under the Exchange Act (17 CFR 240.14d-2(b))

◻ Pre-commencement communications pursuant to Rule 13e-4(c) under the Exchange Act (17 CFR 240.13e-4(c))

Securities registered pursuant to Section 12(b) of the Act:

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| | | |
|:---|:---|:---|
| **Title of each class** | **Trading Symbol(s)** | **Name of each exchange on which registered** |
| None | N/A | N/A |

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Indicate by check mark whether the registrant is an emerging growth company as defined in Rule 405 of the Securities Act of 1933 (§230.405 of this chapter) or Rule 12b-2 of the Securities Exchange Act of 1934 (§240.12b-2 of this chapter).

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 13(a) of the Exchange Act. ◻

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| | |
|:---|:---|
| **Item 1.01** | **Entry into a Material Definitive Agreement.** |

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On December 23, 2025, Enzon Pharmaceuticals, Inc. (the "***Company***") entered into the Sixth Amendment to the Section 382 Rights Agreement (the "***Sixth Amendment***"), which amends the Section 382 Rights Agreement, dated as of August 14, 2020 (the "***Rights Agreement***"), by and between the Company and Continental Stock Transfer & Trust Company, as rights agent. Effective as of June 2, 2021, the Company amended the Rights Agreement (the "***First Amendment***") to extend the Final Expiration Date (as defined in the Rights Agreement) of the rights issued pursuant to the Rights Agreement from the close of business on August 13, 2021 to the close of business on June 2, 2024. Effective as of May 16, 2024, the Company amended the Rights Agreement (the "***Second Amendment***") to extend the Final Expiration Date of the rights issued pursuant to the Rights Agreement from the close of business on June 2, 2024 to the close of business on March 31, 2025. Effective as of March 31, 2025, the Company entered into the Third Amendment (the "***Third Amendment***") to extend the Final Expiration Date of the rights issued pursuant to the Rights Agreement from the close of business on March 31, 2025 to the close of business on June 30, 2026. On August 13, 2025, the Company entered into the Fourth Amendment (the "***Fourth Amendment***"), to amend the Final Expiration Date of the rights issued pursuant to the Rights Agreement from the close of business on June 30, 2026 to the close of business on September 30, 2025. On September 30, 2025, the Company entered into the Fifth Amendment (the "***Fifth Amendment***") to amend the Final Expiration Date of the rights issued pursuant to the Rights Agreement from the close of business on September 30, 2025 to the close of business on December 31, 2025.

On December 23, 2025, the Company entered into the Sixth Amendment (the "***Sixth Amendment***") to amend the Final Expiration Date of the rights issued pursuant to the Rights Agreement from the close of business on December 31, 2025 to the close of business on January 31, 2026. Except for the adjustment to the Final Expiration Date, the Rights Agreement otherwise remains unmodified.

The Sixth Amendment has been adopted because the Company's management believes that it is in the best interests of the Company and its stockholders to provide for a Final Expiration Date of January 31, 2026, as established in the Sixth Amendment.

The foregoing description does not purport to be complete and is qualified in its entirety by reference to the complete text of (i) the Rights Agreement, which was filed with the U.S. Securities and Exchange Commission (the "***SEC***") as Exhibit 4.1 to the Company's Registration Statement on Form 8-A filed with the SEC on August 14, 2020, (ii) the First Amendment, which was filed with the SEC as Exhibit 4.1 to the Current Report on Form 8-K filed on June 8, 2021, (iii) the Second Amendment, which was filed with the SEC as Exhibit 4.1 to the Current Report on Form 8-K filed on May 22, 2024, (iv) the Third Amendment, which was filed with the SEC as Exhibit 4.1 to the Current Report on Form 8-K filed on April 1, 2025, (v) the Fourth Amendment, which was filed with the SEC as Exhibit 4.1 to the Quarterly Report on Form 10-Q filed on August 14, 2025, (vi) the Fifth Amendment, a copy of which was filed with the SEC as Exhibit 4.1 to the Current Report on Form 8-K on September 30, 2025, and (vii) the Sixth Amendment, a copy of which is attached as Exhibit 4.1 hereto and incorporated herein by reference. The Rights Agreement, the First Amendment, the Second Amendment, the Third Amendment, the Fourth Amendment, the Fifth Amendment, and Sixth are incorporated herein by reference.

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| | |
|:---|:---|
| **Item 3.03** | **Material Modification to Rights of Security Holders.** |

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The information set forth in Item 1.01 of this Current Report on Form 8-K is incorporated by reference into this Item 3.03.

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| | |
|:---|:---|
| **Item 9.01** | **Financial Statements and Exhibits.** |

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(d) Exhibits.

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| | |
|:---|:---|
| **Exhibit** | **Description** |
| [4.1](tm2534122d1_ex4-1.htm) | [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.](tm2534122d1_ex4-1.htm) |
| 104 | Cover Page Interactive Data File (embedded within the Inline XBRL document). |

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**SIGNATURES**

Pursuant to the requirements of the Securities Exchange Act of 1934, the registrant has duly caused this report to be signed on its behalf by the undersigned hereunto duly authorized.

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| | | |
|:---|:---|:---|
|  | **ENZON PHARMACEUTICALS, INC.** | **ENZON PHARMACEUTICALS, INC.** |
|  | (Registrant) | (Registrant) |
| Date: December 23, 2025 |  |  |
|  | By: | /s/ Richard L. Feinstein |
|  | Name: | Richard L. Feinstein |
|  | Title: | Chief Executive Officer, Chief Financial Officer and Secretary |

---

## Exhibit 4.1

**<u>Exhibit 4.1</u>**

**SIXTH AMENDMENT TO THE**

**SECTION 382 RIGHTS AGREEMENT**

**by and between**

**ENZON PHARMACEUTICALS, INC.**

**and**

**CONTINENTAL STOCK TRANSFER & TRUST COMPANY, as Rights Agent**

This **SIXTH AMENDMENT TO THE SECTION 382 RIGHTS AGREEMENT** (this "<u>Sixth Amendment</u>") is made and entered into December 23, 2025 and is effective immediately, by and between Enzon Pharmaceuticals, Inc., a Delaware corporation (the "<u>Company</u>"), and Continental Stock Transfer & Trust Company, a New York corporation, as rights agent (the "<u>Rights Agent</u>").

**WHEREAS**, the Company and the Rights Agent are parties to that certain Section 382 Rights Agreement, dated as of August 14, 2020 (the "<u>Rights Agreement</u>"), as initially amended on June 4, 2021, further amended on May 16, 2024, further amended on March 31, 2025, further amended on August 13, 2025, and further amended on September 30, 2025 (the "<u>Fifth Amendment</u>");

**WHEREAS**, the Rights Agreement, under the terms of the Fifth Amendment, will expire on December 31, 2025;

**WHEREAS**, the Company may amend the Rights Agreement pursuant to Section 26 thereof; and

**WHEREAS**, the Board of Directors of the Company has determined that it is in the best interests of the Company and its stockholders to extend the Final Expiration Date to January 31, 2026, in accordance with the terms set forth in this Sixth Amendment.

**NOW, THEREFORE**, in consideration of the foregoing and other good and valuable consideration, the receipt and sufficiency of which the parties hereby acknowledge, the Company and the Rights Agent agree as follows:

&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;1. **<u>Amendments</u>**.

&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;(a) Section 7(a) of the Rights Agreement is hereby amended and restated to read as follows:

"Subject to Section 7(e) and Section 27 hereof, the registered holder of any Rights Certificate may exercise the Rights evidenced thereby (except as otherwise provided herein including, without limitation, the restrictions on exercisability set forth in Section 9(c), Section 11(a)(iii) and Section 23(a) hereof) in whole or in part at any time after the Distribution Date upon surrender of the Rights Certificate, with the form of election to purchase and the certificate on the reverse side thereof duly executed, to the Rights Agent at the principal office or offices of the Rights Agent designated for such purpose, together with payment of the aggregate Purchase Price with respect to the total number of one one-thousandth of a share of Preferred Stock (or other securities, cash or other assets, as the case may be) as to which such surrendered Rights are then exercisable, at or prior to the earliest of (i) the Close of Business on January 31, 2026 (the "<u>Final Expiration Date</u>"), (ii) the time at which the Rights are redeemed as provided in Section 23 hereof, (iii) the time at which all of the Rights (other than Rights that have become void pursuant to the provisions of Section 7(e) hereof) are exchanged for Common Stock or other assets or securities as provided in Section 27 hereof, (iv) the Close of Business on the effective date of the repeal of Section 382 of the Code or any successor statute if the Board of Directors determines that this Agreement is no longer necessary or desirable for the preservation of Tax Benefits, or (v) the Close of Business on the first day of a taxable year of the Company to which the Board of Directors determines that no Tax Benefits may be carried forward (the earliest of (i) and (ii) and (iii) and (iv) and (v) being herein referred to as the "<u>Expiration Date</u>").

&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;(b) All references to "December 31, 2025" in <u>Exhibit B</u> (Form of
Rights Certificate) and <u>Exhibit C</u> (Summary of Rights to Purchase Series A-1 Junior Participating Preferred Stock) to
the Rights Agreement are amended to replace each such reference with "January 31, 2026."

&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;2. **<u>Capitalized Terms</u>**. Capitalized terms not defined herein shall have the meanings given such terms in the Rights Agreement.

&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;3. **<u>Descriptive Headings</u>**. Descriptive headings of the several Sections of this Sixth Amendment are included for convenience of reference only and shall not control or affect the meaning or construction of any of the provisions hereof.

&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;4. **<u>Governing Law</u>**. This Sixth Amendment shall be deemed to be a contract made under the laws of the State of Delaware and for all purposes shall be governed by and construed and enforced in accordance with the laws of such state applicable to contracts to be made and performed entirely within such State.

&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;5. **<u>Counterparts</u>**. This Sixth Amendment may be executed in any number of counterparts and each of such counterparts shall for all purposes be deemed to be an original, and all such counterparts shall together constitute but one and the same instrument. A signature to this Sixth Amendment executed and/or transmitted electronically shall have the same authority, effect and enforceability as an original signature.

&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;6. **<u>Effect of Sixth Amendment</u>**. Except as expressly modified by this Sixth Amendment, the Rights Agreement remains in full force and effect and is hereby ratified and confirmed.

*[Remainder of page left intentionally blank]*

**IN WITNESS WHEREOF**, the parties hereto have caused this Sixth Amendment to be duly executed as of the date first written above.

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| | |
|:---|:---|
| **ENZON PHARMACEUTICALS, INC.** | **ENZON PHARMACEUTICALS, INC.** |
| By: | /s/ Richard L. Feinstein |
| Name: | Richard L. Feinstein |
| Title: | Chief Executive Officer, Chief Financial Officer and Secretary |
| **CONTINENTAL STOCK TRANSFER & TRUST COMPANY** | **CONTINENTAL STOCK TRANSFER & TRUST COMPANY** |
| By: | /s/ Henry Farrell |
| Name: | Henry Farrell |
| Title: | Vice President |

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*[Signature Page to Sixth Amendment to Rights Agreement]*