Enzon Reports Schering-Plough's PEG-INTRON Accepted by the FDA For Review.

Business &Medical Editors

PISCATAWAY, N.J.--(BUSINESS WIRE)--Feb. 10, 2000

Enzon, Inc. (NASDAQ: ENZN) announced today that Schering-Plough Corporations' (NYSE: SGP) Biologics License Application (BLA) for PEG-INTRON(TM) has been accepted for standard review by the FDA.

PEG-INTRON is a modified form of Schering-Plough's INTRON(R) A (interferon alfa-2b) that uses proprietary PEG technology developed by Enzon. Schering-Plough submitted its BLA to the FDA on Dec. 23, 1999 seeking marketing clearance for PEG-INTRON (peginterferon alfa-2b) for the treatment of chronic hepatitis C in patients 18 years of age or older with compensated liver disease.

Under the Prescription Drug Users Fee Act, the FDA should act on Schering-Plough's BLA within 12 months from the date of receipt. While Schering-Plough had requested priority review status for the drug, which would have taken six months, the FDA granted a standard review.

&uot;We have always assumed that PEG-INTRON would receive the standard twelve month FDA review,&uot; said Peter Tombros, Enzon's president and CEO. Mr. Tombros further stated, &uot;Schering-Plough has to be commended for the speed at which they have conducted their clinical trial program.&uot;

&uot;The Agency's acceptance of our application for PEG-INTRON moves us another step forward in the regulatory review of this product,&uot; said Tom Lauda, Executive Vice President of Schering-Plough Pharmaceuticals. &uot;We continue to be pleased with the progress of our PEG-INTRON filings.&uot;

In Europe, Schering-Plough has submitted a centralized Marketing Authorization Application for PEG-INTRON to the European Union's (EU) European Agency for the Evaluation of Medicinal Products (EMEA) seeking marketing approval for the same indication. Approval of the centralized Marketing Authorization Application for PEG-INTRON would result in unified labeling that would be valid in all 15 EU-Member States. The application is currently under CPMP review.

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's research activities are focused primarily in the area of oncology. In addition to two FDA approved products, Enzon has several products in various stages of clinical development by itself and with partners. Enzon develops and markets products on its own and through its alliance partners, which in addition to Schering-Plough include Alexion Pharmaceuticals, Baxter Healthcare, Bristol-Myers Squibb, Eli Lilly, and Rhone-Poulenc Rorer Pharmaceuticals.

Certain statements made in this press release related to potential government approvals, market potential, commercialization and sales revenues of medical products and biologics, as well as their therapeutic applications and outcomes, are forward-looking and are made pursuant to the safe harbor provisions of the Securities Litigation Reform Act of 1995. Such statements involve risks and uncertainties, which may differ materially from those set forth in these statements. In addition, the economic, competitive, governmental, technological and other factors identified in the Company's filings with the Securities and Exchange Commission could affect such results.

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