# EDGAR Filing Document

**Accession Number:** 0000727510
**File Stem:** 0001104659-26-033626
**Filing Date:** 2026-3
**Character Count:** 17145
**Document Hash:** 23776380a4a3cf0933c6f754f824ce26
**Contains OCR:** False
**Source Format:** 

## Filing Content

## Filing Summary
**0001104659-26-033626.hdr.sgml**: 20260324

**ACCESSION NUMBER**: 0001104659-26-033626

**CONFORMED SUBMISSION TYPE**: 8-A12G/A

**PUBLIC DOCUMENT COUNT**: 1

**FILED AS OF DATE**: 20260324

**DATE AS OF CHANGE**: 20260324

**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-A12G/A
- **SEC ACT:** 1934 Act
- **SEC FILE NUMBER:** 000-12957
- **FILM NUMBER:** 26784277

**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

**UNITED STATES**

**SECURITIES AND EXCHANGE COMMISSION**

**Washington, D.C. 20549**

**FORM 8-A/A**

**Amendment No. 11**

**FOR REGISTRATION OF CERTAIN CLASSES OF SECURITIES**

**PURSUANT TO SECTION 12(b) OR (g) OF THE**

**SECURITIES EXCHANGE ACT OF 1934**

**ENZON PHARMACEUTICALS, INC.**

(Exact name of registrant as specified in its charter)

---

| | |
|:---|:---|
| **Delaware**<br> (State or other jurisdiction of incorporation or organization) | **22-2372868**<br> (I.R.S. Employer Identification No.) |

---

---

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

---

Securities to be registered pursuant to Section 12(b) of the Act: None.

---

| | |
|:---|:---|
| **Title of each class**<br> **to be so registered** | **Name of each exchange on which**<br> **each class is to be registered** |
| N/A | N/A |

---

If this form relates to the registration of a class of securities pursuant to Section 12(b) of the Exchange Act and is effective pursuant to General Instruction A.(c) or (e), check the following box. ◻

If this form relates to the registration of a class of securities pursuant to Section 12(g) of the Exchange Act and is effective pursuant to General Instruction A.(d) or (e), check the following box. ⌧

If this form relates to the registration of a class of securities concurrently with a Regulation A offering, check the following box. ◻

Securities Act registration statement or Regulation A offering statement file number to which this form relates: Not applicable.

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

Series A-1 Junior Participating Preferred Stock Purchase Rights

(Title of Class)

**EXPLANATORY NOTE**

This Amendment No. 11 to Form 8-A is filed to amend and supplement Items 1 and 2 of the Registration Statement on Form 8-A filed by Enzon Pharmaceuticals, Inc., a Delaware corporation (the "***Company***"), with the U.S. Securities and Exchange Commission (the "***SEC***") on August 14, 2020, as amended by Amendment No. 1 to Form 8-A filed with the SEC on June 8, 2021, Amendment No. 2 to Form 8-A filed with the SEC on May 22, 2024, Amendment No. 3 to Form 8-A filed with the SEC on April 1, 2025, Amendment No. 4 filed with the SEC on August 14, 2025, Amendment No. 5 to Form 8-A filed with the SEC on September 30, 2025, Amendment No. 6 to Form 8-A filed with the SEC on December 23, 2025, Amendment No. 7 to Form 8-A filed with the SEC on January 30, 2026, Amendment No. 8 to Form 8-A filed with the SEC on February 27, 2026, Amendment No. 9 to Form 8-A filed with the SEC on March 11, 2026, and Amendment No. 10 to the Form 8-A filed with the SEC on March 18, 2026.

**Item 1.** **Description of Registrant's Securities to be Registered.**

On March 23, 2026, the Company entered into the Eleventh Amendment to the Section 382 Rights Agreement (the "***Eleventh 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. Effective as of August 13, 2025, the Company amended the Rights Agreement (the "***Fourth Amendment***") to adjust 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. Effective as of September 30, 2025, the Company amended the Rights Agreement (the "***Fifth Amendment***") to adjust 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. Effective as of December 23, 2025, the Company amended the Rights Agreement (the "***Sixth Amendment***") to adjust 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. Effective as of January 30, 2026, the Company amended the Rights Agreement (the "***Seventh Amendment***") to adjust the Final Expiration Date of the rights issued pursuant to the Rights Agreement from the close of business on January 31, 2026, to noon, New York City time, on March 2, 2026. Effective as of February 27, 2026, the Company amended the Rights Agreement (the "***Eighth Amendment***") to adjust the Final Expiration Date of the rights issued pursuant to the Rights Agreement from noon, New York City time, on March 2, 2026 to noon, New York City time, on March 11, 2026. Effective as of March 10, 2026, the Company amended the Rights Agreement (the "***Ninth Amendment***") to adjust the Final Expiration Date of the rights issued pursuant to the Rights Agreement from noon, New York City time, on March 11, 2026 to noon, New York City time, on March 18, 2026. Effective as of March 18, 2026, the Company amended the Rights Agreement (the "***Tenth Amendment***") to adjust the Final Expiration Date of the rights issued pursuant to the Rights Agreement from noon, New York City time, on March 18, 2026 to noon, New York City time, on March 24, 2026.

On March 23, 2026, the Company entered into the Eleventh Amendment to amend the Final Expiration Date of the rights issued pursuant to the Rights Agreement from noon, New York City time, on March 24, 2026, to noon, New York City time, on March 26, 2026. Except for the adjustment to the Final Expiration Date, the Rights Agreement otherwise remains unmodified.

The foregoing description does not purport to be complete and is qualified in its entirety by reference to the complete text of the Rights Agreement, which was filed as Exhibit 4.1 to the Company's Registration Statement on Form 8-A filed with the SEC on August 14, 2020, the First Amendment, which was filed with the SEC as Exhibit 4.1 to the Company's Current Report on Form 8-K filed on June 8, 2021, the Second Amendment, which was filed with the SEC as Exhibit 4.1 to the Company's Current Report on Form 8-K filed on May 22, 2024, the Third Amendment, which was filed with the SEC as Exhibit 4.1 to the Company's Current Report on Form 8-K filed on April 1, 2025, the Fourth Amendment, which was filed with the SEC as Exhibit 4.1 to the Company's Quarterly Report on Form 10-Q filed on August 14, 2025, the Fifth Amendment, which was filed with the SEC as Exhibit 4.1 to the Company's Current Report on Form 8-K filed on September 30, 2025, the Sixth Amendment, which was filed with the SEC as Exhibit 4.1 to the Company's Current Report on Form 8-K on December 23, 2025, the Seventh Amendment, which was filed with the SEC as Exhibit 4.1 to the Company's Current Report on Form 8-K on January 30, 2026, the Eighth Amendment, which was filed with the SEC as Exhibit 4.1 to the Company's Current Report on Form 8-K on February 27, 2026, the Ninth Amendment, which was filed with the SEC as Exhibit 4.1 to the Company's Current Report on Form 8-K on March 11, 2026, the Tenth Amendment, which was filed with the SEC as Exhibit 4.1 to the Company's Current Report on Form 8-K on March 18, 2026, and the Eleventh Amendment, which is filed as Exhibit 4.12 hereto.

The Rights Agreement, the First Amendment, the Second Amendment, the Third Amendment, the Fourth Amendment, the Fifth Amendment, the Sixth Amendment, the Seventh Amendment, the Eighth Amendment, the Ninth Amendment, the Tenth Amendment, and the Eleventh Amendment are incorporated herein by reference.

**Item 2.** **Exhibits.**

---

| | |
|:---|:---|
| **Exhibit<br> No.** | **Description** |
| [3.1](https://www.sec.gov/Archives/edgar/data/727510/000110465920095639/tm2027628d1_ex3-1.htm) | [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 herein by reference to Exhibit 3.1 of the Company's Registration Statement on Form 8-A filed with the SEC on August 14, 2020).](https://www.sec.gov/Archives/edgar/data/727510/000110465920095639/tm2027628d1_ex3-1.htm) |
| [4.1](https://www.sec.gov/Archives/edgar/data/727510/000110465920095639/tm2027628d1_ex4-1.htm) | [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 herein by reference to Exhibit 4.1 of the Company's Registration Statement on Form 8-A filed with the SEC on August 14, 2020).](https://www.sec.gov/Archives/edgar/data/727510/000110465920095639/tm2027628d1_ex4-1.htm) |
| [4.2](https://www.sec.gov/Archives/edgar/data/727510/000110465921078218/tm2119004d1_ex4-1.htm) | [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 herein by reference to Exhibit 4.1 of the Company's Current Report on Form 8-K filed with the SEC on June 8, 2021).](https://www.sec.gov/Archives/edgar/data/727510/000110465921078218/tm2119004d1_ex4-1.htm) |
| [4.3](https://www.sec.gov/Archives/edgar/data/727510/000110465924064247/tm2415024d1_ex4-1.htm) | [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 herein by reference to Exhibit 4.1 of the Company's Current Report on Form 8-K filed with the SEC on May 22, 2024).](https://www.sec.gov/Archives/edgar/data/727510/000110465924064247/tm2415024d1_ex4-1.htm) |
| [4.4](https://www.sec.gov/Archives/edgar/data/727510/000110465925030585/tm2511075d1_ex4-1.htm) | [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 herein by reference to Exhibit 4.1 of the Company's Current Report on Form 8-K filed with the SEC on April 1, 2025).](https://www.sec.gov/Archives/edgar/data/727510/000110465925030585/tm2511075d1_ex4-1.htm) |
| [4.5](https://www.sec.gov/Archives/edgar/data/727510/000141057825001810/enzn-20250630xex4d1.htm) | [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 herein by reference to Exhibit 4.1 of the Company's Quarterly Report on Form 10-Q filed with the SEC on August 14, 2025).](https://www.sec.gov/Archives/edgar/data/727510/000141057825001810/enzn-20250630xex4d1.htm) |
| [4.6](https://www.sec.gov/Archives/edgar/data/727510/000110465925095078/tm2527543d1_ex4-1.htm) | [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 herein by reference to Exhibit 4.1 of the Company's Current Report on Form 8-K filed with the SEC on September 30, 2025).](https://www.sec.gov/Archives/edgar/data/727510/000110465925095078/tm2527543d1_ex4-1.htm) |

---

---

| | |
|:---|:---|
| [4.7](https://www.sec.gov/Archives/edgar/data/727510/000110465925124254/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 (incorporated herein by reference to Exhibit 4.1 of the Company's Current Report on Form 8-K filed with the SEC on December 23, 2025).](https://www.sec.gov/Archives/edgar/data/727510/000110465925124254/tm2534122d1_ex4-1.htm) |
| [4.8](https://www.sec.gov/Archives/edgar/data/727510/000110465926008322/tm2521156d11_ex4-1.htm) | [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 herein by reference to Exhibit 4.1 of the Company's Current Report on Form 8-K filed with the SEC on January 30, 2026).](https://www.sec.gov/Archives/edgar/data/727510/000110465926008322/tm2521156d11_ex4-1.htm) |
| [4.9](https://www.sec.gov/Archives/edgar/data/727510/000110465926021051/tm267491d2_ex4-1.htm) | [Eighth Amendment to the Section 382 Rights Agreement, dated as of February 27, 2026, by and between Enzon Pharmaceuticals, Inc. and Continental Stock Transfer & Trust Company (incorporated herein by reference to Exhibit 4.1 of the Company's Current Report on Form 8-K filed with the SEC on February 27, 2026).](https://www.sec.gov/Archives/edgar/data/727510/000110465926021051/tm267491d2_ex4-1.htm) |

---

---

| | |
|:---|:---|
| [4.10](https://www.sec.gov/Archives/edgar/data/727510/000110465926026169/tm267492d8_ex4-1.htm) | [Ninth Amendment to the Section 382 Rights Agreement, dated as of March 10, 2026, by and between Enzon Pharmaceuticals, Inc. and Continental Stock Transfer & Trust Company (incorporated herein by reference to Exhibit 4.1 of the Company's Current Report on Form 8-K filed with the SEC on March 11, 2026).](https://www.sec.gov/Archives/edgar/data/727510/000110465926026169/tm267492d8_ex4-1.htm) |
| [4.11](https://www.sec.gov/Archives/edgar/data/727510/000110465926029952/tm267491d4_ex4-1.htm) | [Tenth Amendment to the Section 382 Rights Agreement, dated as of March 18, 2026, by and between Enzon Pharmaceuticals, Inc. and Continental Stock Transfer & Trust Company (incorporated herein by reference to Exhibit 4.1 of the Company's Current Report on Form 8-K filed with the SEC on March 18, 2026).](https://www.sec.gov/Archives/edgar/data/727510/000110465926029952/tm267491d4_ex4-1.htm) |
| [4.12](https://www.sec.gov/Archives/edgar/data/727510/000110465926033624/tm267492d15_ex4-1.htm) | [Eleventh Amendment to the Section 382 Rights Agreement, dated as of March 24, 2026, by and between Enzon Pharmaceuticals, Inc. and Continental Stock Transfer & Trust Company (incorporated herein by reference to Exhibit 4.1 of the Company's Current Report on Form 8-K filed with the SEC on March 24, 2026).](https://www.sec.gov/Archives/edgar/data/727510/000110465926033624/tm267492d15_ex4-1.htm) |

---

**SIGNATURE**

Pursuant to the requirements of Section 12 of the Securities Exchange Act of 1934, the registrant has duly caused this registration statement to be signed on its behalf by the undersigned, thereto duly authorized.

---

| | | |
|:---|:---|:---|
|  | **ENZON PHARMACEUTICALS, INC.** | **ENZON PHARMACEUTICALS, INC.** |
|  | (Registrant) | (Registrant) |
| Dated: March 24, 2026 |  |  |
|  | By: | /s/Richard L. Feinstein |
|  | Name: | Richard L. Feinstein |
|  | Title: | Chief Executive Officer, Chief Financial Officer and Secretary |

---