[SCHEDULE 13D/A] ENZON PHARMACEUTICALS, INC. SEC Filing

Rhea-AI Filing Summary

Enzon Pharmaceuticals (ENZN) filed Amendment No. 17 to Schedule 13D55% of the combined company after the merger, the exchange ratio for Enzon’s Series C Preferred will be based on the 20‑Day VWAP, and Enzon will conduct a 1‑for‑100 reverse stock split before the merger’s effective time. The minimum cash required at closing is reduced, and the outside date to terminate the agreement is extended to March 31, 2026.

Icahn Enterprises Holdings agreed to deliver written consents approving the merger and a charter amendment, and to exchange all of its Series C Preferred into common shares based on full liquidation preference and the 20‑Day VWAP. The filing reports 36,056,636 shares beneficially owned with 48.6% of the class, with shared voting and dispositive power.

Insights

M&A and governance analyst

Merger terms reset: 55% to Viskase holders; reverse split; deadline extended.

The amended deal reallocates ownership so that Viskase holders will own 55% post‑merger, clarifying the exchange mechanics. Enzon will implement a 1‑for‑100 reverse stock split prior to closing, which adjusts the share count without altering proportional interests.

The parties reduced Enzon’s minimum cash at closing and extended the outside date to March 31, 2026. Icahn affiliates committed to deliver written consents and to exchange all Series C Preferred into common based on the 20‑Day VWAP and full liquidation preference, simplifying the capital structure at closing.

The amendment includes waivers of certain known Viskase breaches as of Oct 24, 2025 and refines “Material Adverse Effect” with a knowledge qualifier. Actual outcomes depend on completion conditions and holder actions disclosed in the agreements.

10/24/2025 - 04:14 PM

SECURITIES AND EXCHANGE COMMISSION
Washington, D.C. 20549

SCHEDULE 13D

Under the Securities Exchange Act of 1934

(Amendment No. 17)

ENZON PHARMACEUTICALS, INC.

(Name of Issuer)

Common Stock, par value $0.01 per share

(Title of Class of Securities)

293904108

(CUSIP Number)

Jesse Lynn, Esq.
Icahn Capital LP, 16690 Collins Avenue, Suite PH-1
Sunny Isles Beach, FL, 33160
305-442-4000

Joshua Apfelroth
Proskauer Rose LLP, Eleven Times Square
New York, NY, 10036
212-969-3000

Louis Rambo
Proskauer Rose LLP, 1001 Pennsylvania Ave. NW, Suite 600
Washington, DC, 20004
202-416-6800

(Name, Address and Telephone Number of Person Authorized to Receive Notices and Communications)

10/24/2025

(Date of Event Which Requires Filing of This Statement)

If the filing person has previously filed a statement on Schedule 13G to report the acquisition that is the subject of this Schedule 13D, and is filing this schedule because of §§ 240.13d-1(e), 240.13d-1(f) or 240.13d-1(g), check the following box.

The information required on the remainder of this cover page shall not be deemed to be "filed" for the purpose of Section 18 of the Securities Exchange Act of 1934 ("Act") or otherwise subject to the liabilities of that section of the Act but shall be subject to all other provisions of the Act (however, see the Notes).

SCHEDULE 13D

CUSIP No. 293904108

1

Name of reporting person

CARL C ICAHN

2

Check the appropriate box if a member of a Group (See Instructions)

(a)
(b)

3

SEC use only

4

Source of funds (See Instructions)

OO

5

Check if disclosure of legal proceedings is required pursuant to Items 2(d) or 2(e)

6

Citizenship or place of organization

UNITED STATES

Number of Shares Beneficially Owned by Each Reporting Person With:

7	Sole Voting Power 0.00
8	Shared Voting Power 36,056,636.00
9	Sole Dispositive Power 0.00
10	Shared Dispositive Power 36,056,636.00

11

Aggregate amount beneficially owned by each reporting person

36,056,636.00

12

Check if the aggregate amount in Row (11) excludes certain shares (See Instructions)

13

Percent of class represented by amount in Row (11)

48.6 %

14

Type of Reporting Person (See Instructions)

IN

Comment for Type of Reporting Person:

The Reporting Person may also be deemed to beneficially own shares of Preferred Stock.

SCHEDULE 13D

CUSIP No. 293904108

1

Name of reporting person

ICAHN ENTERPRISES HOLDINGS L.P.

2

Check the appropriate box if a member of a Group (See Instructions)

(a)
(b)

3

SEC use only

4

Source of funds (See Instructions)

OO

5

Check if disclosure of legal proceedings is required pursuant to Items 2(d) or 2(e)

6

Citizenship or place of organization

DELAWARE

Number of Shares Beneficially Owned by Each Reporting Person With:

7	Sole Voting Power 0.00
8	Shared Voting Power 36,056,636.00
9	Sole Dispositive Power 0.00
10	Shared Dispositive Power 36,056,636.00

11

Aggregate amount beneficially owned by each reporting person

36,056,636.00

12

Check if the aggregate amount in Row (11) excludes certain shares (See Instructions)

13

Percent of class represented by amount in Row (11)

48.6 %

14

Type of Reporting Person (See Instructions)

PN

Comment for Type of Reporting Person:

The Reporting Person may also be deemed to beneficially own shares of Preferred Stock.

SCHEDULE 13D

CUSIP No. 293904108

1

Name of reporting person

ICAHN ENTERPRISES G.P. INC.

2

Check the appropriate box if a member of a Group (See Instructions)

(a)
(b)

3

SEC use only

4

Source of funds (See Instructions)

OO

5

Check if disclosure of legal proceedings is required pursuant to Items 2(d) or 2(e)

6

Citizenship or place of organization

DELAWARE

Number of Shares Beneficially Owned by Each Reporting Person With:

7	Sole Voting Power 0.00
8	Shared Voting Power 36,056,636.00
9	Sole Dispositive Power 0.00
10	Shared Dispositive Power 36,056,636.00

11

Aggregate amount beneficially owned by each reporting person

36,056,636.00

12

Check if the aggregate amount in Row (11) excludes certain shares (See Instructions)

13

Percent of class represented by amount in Row (11)

48.6 %

14

Type of Reporting Person (See Instructions)

CO

Comment for Type of Reporting Person:

The Reporting Person may also be deemed to beneficially own shares of Preferred Stock.

SCHEDULE 13D

Item 1.	Security and Issuer
(a)	Title of Class of Securities: Common Stock, par value $0.01 per share
(b)	Name of Issuer: ENZON PHARMACEUTICALS, INC.
(c)	Address of Issuer's Principal Executive Offices: 20 Commerce Drive (Suite 135), Cranford, NEW JERSEY , 07016.
Item 1 Comment: This statement constitutes Amendment No. 17 to the Schedule 13D relating to the shares of Common Stock, par value $0.01 per share (the "Shares"), issued by Enzon Pharmaceuticals, Inc., a Delaware corporation (the "Issuer"), and amends the Schedule 13D relating to the Shares filed on March 14, 2008 (as previously amended, the "Original 13D"), on behalf of the Reporting Persons (as defined in Item 2 of Amendment No. 16 to the Schedule 13D). Capitalized terms used herein and not otherwise defined have the respective meanings ascribed thereto in the Original 13D.
Item 4.	Purpose of Transaction
	Item 4 of the Original 13D is hereby amended and supplemented as follows: Amendment to the Agreement and Plan of Merger of the Issuer and Viskase On October 24, 2025, the Issuer, Merger Sub, and Viskase entered into an amendment to the Merger Agreement (the "Merger Agreement Amendment"). Pursuant to the terms of the Merger Agreement Amendment, the parties to the Merger Agreement agreed, among other things, to the following: (i) an adjustment to the exchange ratio as calculated under the Merger Agreement for the exchange of each share of Viskase Common Stock issued and outstanding immediately prior to the Merger (other than shares held by holders that properly exercise dissenters rights, shares held in treasury, and shares held by the Issuer, Merger Sub, or a wholly owned subsidiary of Viskase, the Issuer, or Merger Sub) into Shares, such that the current Viskase stockholders will own 55% of the combined company following the Merger; (ii) an adjustment to the exchange ratio for the exchange of each share of the Issuer's Series C Preferred Stock for Shares, to be based upon the 20-day volume weighted average price of the Shares prior to the execution of the Merger Agreement Amendment (the "20-Day VWAP"); (iii) a reduction in the minimum amount of cash that the Issuer is required to have at Closing; (iv) the Issuer effecting a 1-for-100 reverse stock split with respect to all Shares prior to the effective time of the Merger; (v) an extension to the date on which either party may terminate the Merger Agreement if the Merger has not yet occured from 11:59 p.m. Eastern Time on December 31, 2025 to 11:59 p.m. Eastern Time on March 31, 2026; (vi) with respect to each of the Issuer and Merger Sub (each, a "Waiving Party"), waive, consent to and release (a) any inaccuracy in, breach of or failure to comply with any representation, warranty, covenant or agreement of Viskase in the Merger Agreement, to the extent known to such Waiving Party as of the date of the Merger Agreement Amendment (each, a "Viskase Breach") and (b) any fact, event, circumstance or condition giving rise to a Viskase Breach, in each case to the extent known to such Waiving Party as of the date of the Merger Agreement Amendment and occurring or existing on or prior to such date; and (vii) a modification to the definition of "Viskase Material Adverse Effect" in the Merger Agreement to provide that, if the Issuer, Merger Sub or any of their respective representatives knew of the material facts of a matter prior to the date of the Merger Agreement Amendment, then no effect, change, event or occurrence arising out of, or resulting from such facts shall constitute a Viskase Material Adverse Effect for all purposes under the Merger Agreement; provided that, for the avoidance of doubt, a Viskase Material Adverse Effect may result from facts that the Issuer, Merger Sub or any of their respective representatives become aware of after the date of the Merger Agreement Amendment The foregoing description does not purport to be complete, and is qualified in its entirety by reference to the complete text of the Merger Agreement Amendment, a copy of which is attached as Exhibit 99.1 hereto and incorporated herein by reference. IEH Support Agreement In connection with the execution and delivery of the Merger Agreement Amendment, on October 24, 2025 Icahn Enterprises Holdings and certain of its affiliates entered into an amendment to the IEH Support Agreement (the "Support Agreement Amendment") with the Issuer and Viskase. Pursuant to the terms of the IEH Support Agreement (as amended by the Support Agreement Amendment), Icahn Enterprises Holdings agreed to, among other things, (i) deliver or cause the delivery of written consents with respect to all of the issued and outstanding Shares held by Icahn Enterprises Holdings and its affiliates approving the Merger and the amendment to the Issuer's certificate of incorporation, and (ii) exchange all of the shares of Series C Preferred Stock held by Icahn Enterprises Holdings and its affiliates into Shares prior to the consummation of the Merger, based on the full liquidation preference of such shares of Series C Preferred Stock and the 20-Day VWAP. The foregoing description does not purport to be complete, and is qualified in its entirety by reference to the complete text of the Support Agreement Amendment, a copy of which is attached as Exhibit 99.2 hereto and incorporated herein by reference.
Item 6.	Contracts, Arrangements, Understandings or Relationships With Respect to Securities of the Issuer
	Item 6 of the Original 13D is hereby amended and supplemented as follows: The disclosure set forth in Item 4 of this Schedule 13D is incorporated herein by reference.
Item 7.	Material to be Filed as Exhibits.
	The exhibit list in Item 7 of the Original 13D is hereby amended and supplemented by adding the following exhibits: 3. Merger Agreement Amendment, dated October 24, 2025 (incorporated by reference to Exhibit 2.1 to the Current Report on Form 8-K filed by Enzon Pharmaceuticals, Inc. on October 24, 2025) 4. Support Agreement Amendment, dated October 24, 2025 (incorporated by reference to Exhibit 10.1 to the Current Report on Form 8-K filed by Enzon Pharmaceuticals, Inc. on October 24, 2025)

SIGNATURE

After reasonable inquiry and to the best of my knowledge and belief, I certify that the information set forth in this statement is true, complete and correct.

CARL C ICAHN

Signature:	/s/ Carl C. Icahn
Name/Title:	Carl C. Icahn
Date:	10/24/2025

ICAHN ENTERPRISES HOLDINGS L.P.

Signature:	/s/ Ted Papapostolou
Name/Title:	Ted Papapostolou, Chief Financial Officer
Date:	10/24/2025

ICAHN ENTERPRISES G.P. INC.

Signature:	/s/ Ted Papapostolou
Name/Title:	Ted Papapostolou, Chief Financial Officer
Date:	10/24/2025

FAQ

What did ENZN change in the Viskase merger terms?

Viskase holders will own 55% post‑merger, the Series C Preferred exchange uses the 20‑Day VWAP, and Enzon will do a 1‑for‑100 reverse split.

What is Carl Icahn’s reported ownership in ENZN?

The filing reports 36,056,636 shares beneficially owned, representing 48.6% of the class, with shared voting and dispositive power.

Did ENZN extend the merger outside date?

Yes. The termination right date moved to March 31, 2026.

What did Icahn Enterprises agree to under the Support Agreement?

To deliver written consents approving the merger and charter amendment, and to exchange all Series C Preferred into common based on full liquidation preference and the 20‑Day VWAP.

Will ENZN conduct a reverse stock split?

Yes. Enzon will effect a 1‑for‑100 reverse stock split before the merger’s effective time.

Were there changes to conditions and representations?

The amendment includes waivers of certain known Viskase breaches as of Oct 24, 2025 and modifies the Material Adverse Effect definition with a knowledge qualifier.