You May Vote Your Proxy When You View The Material On The Internet. You Will Be Asked To Follow The Prompts To Vote Your Shares. Enzon Pharmaceuticals, Inc. 20 Commerce Drive, Suite 135 Cranford, New Jersey 07016 *Stockholders are cordially invited to participate in the Virtual 2023 Annual Meeting and vote during the meeting. Dear Stockholder, The 2023 Annual Meeting of Stockholders (the “2023 Annual Meeting”) of Enzon Pharmaceuticals, Inc. (the “Company”) will be held on Thursday, June 8, 2023 at 11:00 a.m., Eastern time. The annual meeting will be a completely “virtual” meeting of stockholders. You will be able to listen and participate in the virtual annual meeting as well as vote and submit your questions during the live webcast of the meeting by visiting https://www.cstproxy.com/enzon/2023 and entering the 12-digit control number included in this Notice Regarding the Availability of Proxy Materials, on your proxy card or in the instructions that accompanied your proxy materials. Your electronic vote authorizes the named proxies to vote your shares in the same manner as if you marked, signed, dated, and returned the proxy card. The Proxy Materials are available for review at: https://www.cstproxy.com/enzon/2023 CONTROL NUMBER ENZON PHARMACEUTICALS, INC. c/o Continental Proxy Services 1 State Street, New York, NY 10004 NOTICE OF ANNUAL MEETING OF STOCKHOLDERS to be held on Thursday, June 8, 2023 Proposals to be considered at the 2023 Annual Meeting: (1) to elect three (3) directors, each for a one-year term expiring at the Company’s next annual meeting of stockholders and until such director’s successor is elected and qualified; (2) to ratify the appointment of EisnerAmper LLP as the Company’s independent registered public accounting firm for the fiscal year ending December 31, 2023; (3) to approve, on an advisory basis, the compensation of the Company’s named executive officers; and (4) to transact such other matters as may properly come before the 2023 Annual Meeting or any adjournment or postponement thereof. The Company’s Board of Directors has proposed and recommends that stockholders vote “FOR” each of the nominees to the Board of Directors listed in Proposal No. 1 and “FOR” Proposals Nos. 2 and 3. Vote Your Proxy on the Internet: Go to http://www.cstproxyvote.com Have your notice available when you access the above website. Follow the prompts to vote your shares. Vote during the Meeting – If you plan to attend the virtual online annual meeting, you will need your 12 digit control number to vote electronically during the annual meeting. To attend the annual meeting, visit: https://www.cstproxy.com/enzon/2023

ENZON PHARMACEUTICALS, INC. 20 Commerce Drive, Suite 135 Cranford, New Jersey 07016 Important Notice Regarding the Availability of Proxy Materials For the 2023 Stockholder Meeting to Be Held On Thursday, June 8, 2023 The following Proxy Materials for the 2023 Annual Meeting are available to you to review at: https://www.cstproxy.com/enzon/2023 ACCESSING YOUR PROXY MATERIALS ONLINE Have this notice available when you request a paper or email copy of the proxy materials or to vote your proxy electronically. You must reference your control number. REQUESTING A PAPER OR EMAIL COPY OF THE PROXY MATERIALS By telephone please call 1-888-221-0691, or By logging on to https://www.cstproxy.com/enzon/2023 or By email at: proxy@continentalstock.com Please include the company name and your control number in the subject line. You may contact the Company at (732) 980-4500 or through an e-mail request to investor@enzon.com for information on how to access the virtual 2023 Annual Meeting. This communication presents only an overview of the more complete proxy materials that are available to you on the Internet. We encourage you to access and review all of the important information contained in the proxy materials before voting. If you would like to receive a paper or e-mail copy of these documents, you must request one. There is no charge for such documents to be mailed to you. Please make your request for a copy as instructed below on or before May 24, 2023 to facilitate a timely delivery. - the Company’s Annual Report on Form 10-K for the fiscal year ended December 31, 2022; - the Company’s Proxy Statement for the 2023 Annual Meeting; - the Proxy Card for the 2023 Annual Meeting; and - any amendments to the foregoing materials that are required to be furnished to stockholders.