Enzon Announces PEG-INTRON and REBETOL Combination Therapy Receives FDA Approval for Treatment of Chronic Hepatitis C.

Business & Health Editors

PISCATAWAY, N.J--(BUSINESS WIRE)--Aug. 8, 2001

Enzon, Inc. (NASDAQ:ENZN) announced today that Schering-Plough (NYSE:SGP) has reported that the U.S. Food and Drug Administration (FDA) has approved PEG-INTRON(TM) (peginterferon alfa-2b) Powder for Injection for use in combination therapy with REBETOL(R) (ribavirin, USP) Capsules for the treatment of chronic hepatitis C in patients with compensated liver disease who have not been previously treated with interferon alpha and are at least 18 years of age.

PEG-INTRON is a longer-acting form of INTRON(R) A (interferon alfa-2b, recombinant) Injection that uses proprietary PEG technology developed by Enzon. Under the Company's licensing agreement with Schering-Plough, Enzon is entitled to royalties on worldwide sales of PEG-INTRON.

The PEG-INTRON and REBETOL treatment regimen is the first and only pegylated interferon-based combination therapy approved in the United States. As previously reported, REBETOL Capsules are expected to be available nationwide sometime this fall.

"PEG-INTRON and REBETOL combination therapy gives new hope to the estimated 4 million Americans infected with the hepatitis C virus," said John G. McHutchison, M.D., medical director, liver transplantation, division of gastroenterology and hepatology, Scripps Clinic and Research Foundation, La Jolla, Calif. "This combination therapy represents a new standard of care for hepatitis C, increasing our ability to eradicate detectable levels of the virus, while providing patients with the convenience of once-weekly dosing of PEG-INTRON versus the three-times-a-week dosing of standard interferon," McHutchison said.

"This approval demonstrates the value of Enzon's proprietary PEG technology," said Arthur J. Higgins, Enzon's president and chief executive officer. "Expanding royalties from the sale of PEG-INTRON, coupled with the proceeds of our recent convertible notes offering, place Enzon in a unique strategic position. We are now well positioned to accelerate the expansion of our internal pipeline, and at the same time pursue strategic and collaborative arrangements and possible acquisitions to further accelerate growth."

PEG-INTRON was granted marketing approval by FDA on Jan. 19, 2001, as once-weekly monotherapy for the treatment of chronic hepatitis C in patients not previously treated with interferon alpha who have compensated liver disease and are at least 18 years of age. PEG-INTRON, which is approved for dosing according to patient body weight, is the first and only pegylated interferon monotherapy approved for marketing in the United States.

REBETOL was granted FDA approval on July 25, 2001, as a separately marketed product for use only in combination with INTRON A Injection. REBETOL had been previously approved in the United States only as a component of REBETRON(TM) Combination Therapy, which contains REBETOL Capsules and INTRON A in a single package. Schering-Plough continues to market REBETRON Combination Therapy in the United States.

In the European Union (EU), PEG-INTRON and REBETOL combination therapy was granted centralized marketing authorization by the European Commission on March 26, 2001, for the treatment of both relapsed and naive (previously untreated) adult patients with histologically proven chronic hepatitis C.

PEG-INTRON, recombinant interferon alfa-2b linked to a 12,000 dalton polyethylene glycol (PEG) molecule, is a once-weekly therapy designed to optimize the balance between antiviral activity and elimination half-life. Schering-Plough holds an exclusive worldwide license to PEG-INTRON.

Some 4 million Americans are infected with the hepatitis C virus (HCV) and approximately 70 percent of infected patients go on to develop chronic liver disease, according to the Centers for Disease Control and Prevention (CDC). Hepatitis C infection contributes to the deaths of an estimated 8,000 to 10,000 Americans each year. This toll is expected to triple by the year 2010 and exceed the number of annual deaths due to AIDS, according to the CDC. The CDC has reported that HCV-associated end-stage liver disease is the most frequent indication for liver transplantation among adults. It is predicted that direct U.S. medical costs to treat HCV-related disease will exceed $13 billion for the years 2010 through 2019, according to a study published in the American Journal of Public Health.

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. Three products are currently marketed which utilize Enzon's technology: PEG-INTRON marketed by Schering-Plough for hepatitis C, ONCASPAR(R) for Acute Lymphoblastic Leukemia (ALL), and ADAGEN(R) a treatment for a form of Severe Combined Immunodeficiency Disease (SCID), commonly known as the "Bubble Boy Disease." In addition to three approved products, Enzon has several products in various stages of clinical development by itself and with partners, including additional indications for PEG-INTRON with Schering-Plough. A Phase III clinical trial is being conducted for PEG-INTRON for the treatment of malignant melanoma. Enzon develops and markets products on its own and through strategic alliances, which in addition to Schering-Plough Corporation, include Alexion Pharmaceuticals, Inc., Baxter Healthcare Corporation, Bristol-Myers Squibb Company, Eli Lilly & Company, and Aventis.

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/A, Form 10-Q's and Form 8-Ks on file with the SEC, including without limitation, risks in obtaining and maintaining regulatory approval for indications and expanded indications, market acceptance of and continuing demand for Enzon's products and the impact of competitive products and pricing.

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