Enzon Accesses Phase III Clinical Candidate.

Business Editors/Health/Medical Writers

BRIDGEWATER, N.J.--(BUSINESS WIRE)--June 17, 2003

Enzon Pharmaceuticals, Inc. (NASDAQ:ENZN):

Company Licenses the Exclusive North American Rights to

Develop and Commercialize Fresenius' Transplant Rejection Product

ATG-Fresenius S

Enzon Pharmaceuticals, Inc. (NASDAQ:ENZN) announced today that the Company and Fresenius Biotechnology, a division of Fresenius, have signed an agreement in which Fresenius will license to Enzon exclusive North American rights to develop and commercialize ATG-Fresenius S, a polyclonal antibody preparation used for T-lymphocyte suppression in organ transplant patients and currently marketed by Fresenius in over 60 countries worldwide.

Enzon intends to initiate a Phase III clinical program for this product subject to, and in accordance with, the U.S. Food and Drug Administration (FDA) requirements during the first half of calendar year 2004. Under the terms of the agreement, Enzon will be responsible for the costs related to the North American clinical development and regulatory approval and Fresenius will be responsible for the drug supplies and all manufacturing aspects necessary to obtain US regulatory approval.

"ATG-Fresenius S is a great strategic fit, which will not only significantly enhance our pipeline but will also create future marketing synergies for our sales team that is already calling on physicians within this treatment setting," said Arthur Higgins, Enzon chairman and chief executive officer. "What is also notable about this transaction is the potential to generate more than $50 million in annual revenue with an attractive level of investment and development risk, given this product's demonstrated clinical efficacy. Furthermore, this agreement exemplifies Enzon's continuing commitment to research and development and enhancing its existing product offering."

"We are very happy to have Enzon as our North American partner. With complete development, regulatory, and commercialization expertise, Enzon is more than capable of successfully and efficiently moving ATG-Fresenius S into the North American marketplace," said Thomas Gottwald, MD, PhD, President of Fresenius Biotechnology.

For the first indication, Fresenius will provide clinical supplies at no charge to Enzon. Fresenius will receive two separate milestone payments of $1 million each, the first payment upon FDA approval of an Investigational New Drug Application and the second at the submission of a Biologics License Application. Upon the commercialization of the product in North America, Enzon will purchase the finished product from Fresenius at a specified percentage of net sales.

ATG-Fresenius S is a polyclonal antibody preparation. As opposed to monoclonal antibodies, the product targets a range of antigens on activated T-cells and depletes T-cells that otherwise would result in an immunologic attack on the transplanted organ leading to its rejection. For solid organ transplantation, ATG Fresenius S has been shown to be very effective, typically leading to a substantial improvement of graft survival. ATG-Fresenius S more recently has been administered conveniently as a single high dose just prior to the surgical procedure. ATG-Fresenius S is approved outside the US for the prevention of organ rejection and the treatment of acute rejection episodes. Moreover, clinical experience with ATG-Fresenius S for conditioning regimens and prevention of graft versus host disease in bone marrow transplantation has been described.

Enzon Pharmaceuticals is a biopharmaceutical company dedicated to the discovery, development, and commercialization of therapeutics to treat life-threatening diseases. The company has developed or acquired a number of marketed products, including ABELCET, which is marketed in North America by Enzon, and PEG-INTRON, marketed by Schering-Plough. Enzon's product-focused strategy includes an extensive drug development program that leverages the Company's PEG modification and single-chain antibody (SCA(R)) technologies. Internal research and development efforts are complemented by strategic transactions that provide access to additional products, projects, and technologies. Enzon has several drug candidates in various stages of development, independently and with partners.

Except for the historical information herein, the matters discussed in this news release include forward-looking statements that may involve a number of risks and uncertainties. Actual results may vary significantly based upon a number of factors, which are described in the Company's Form 10-K, Form 10-Q's and Form 8-K's on file with the SEC, including without limitation, Enzon's dependence on Schering-Plough's effective marketing of PEG-INTRON; Enzon's ability to sustain profitability; risks in obtaining and maintaining regulatory approval for indications and expanded indications for Enzon's products; market acceptance of and continuing demand for Enzon's products; timing and results of clinical trials and the impact of competitive products and pricing, All information in this press release is as of June 17, 2003, and the Company undertakes no duty to update this information.

This release is also available at http://www.enzon.com