Enzon Institutes Labeling and Distribution Modifications For ONCASPAR.

PISCATAWAY, N.J.--(BUSINESS WIRE)--Nov. 2, 1998--Enzon, Inc. (Nasdaq:ENZN) today announced an agreement with the FDA for temporary labeling and distribution modifications for ONCASPAR(R), an agent used in combination chemotherapy for patients with Acute Lymphoblastic Leukemia who are hypersensitive to other available treatments. During this temporary period, Enzon will distribute ONCASPAR directly to patients on an as needed basis.

This action was prompted by the recent observation that particulate matter has formed in some vials of ONCASPAR. Until the current problem can be resolved, Enzon and the FDA have agreed to a label modification that will limit ONCASPAR's use to intra-muscular injection. In addition, Enzon will institute an inspection procedure that will be carried out immediately prior to distribution. These actions will serve as added safety precautions. Rhone-Poulenc Rorer (RPR), Enzon's U.S. distributor of ONCASPAR, has voluntarily instituted an urgent drug notification under which approximately 600 vials of ONCASPAR in the market will be returned to Enzon. Enzon will supply new product that meets all product specifications and is labeled for intra-muscular use only.

"Enzon and the FDA are working diligently to ensure timely and safe therapy for patients who depend on the continued availability of ONCASPAR," said Peter Tombros, president and chief executive officer of Enzon.

Enzon is evaluating modifications to its existing ONCASPAR manufacturing process to reduce the potential for particulates. This manufacturing problem is specific for ONCASPAR.

Under the temporary distribution arrangement, Enzon will receive the full list price for ONCASPAR. When the existing manufacturing problem has been resolved, it is expected that RPR will resume the normal distribution of ONCASPAR.

Enzon is a biopharmaceutical company developing advanced therapeutics for life-threatening diseases through the application of its proprietary drug delivery and targeting technologies, PEG Modification, Pro Drug/Transport technology and Single-Chain Antigen-Binding (SCA(R)) protein technology. Enzon also markets ADAGEN, a treatment for a form of severe combined immunodeficiency disease (SCID), commonly known as the "Bubble Boy Disease".

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 on file with the SEC, including without limitation, risks in obtaining and maintaining regulatory approval for expanded indications, market acceptance of and continuing demand for Enzon's products and the impact of competitive products and pricing.