Tuesday, Jun 8, 1999

Genentech and Immunex Announce Patent License Agreement for Immunoadhesin Technology for ENBREL

South San Francisco, Calif. and Seattle -- June 8, 1999 --

Genentech, Inc. (NYSE: GNE) and Immunex Corporation (NASDAQ: IMNX) announced today that the two companies have signed a license agreement that grants rights under Genentech's immunoadhesin patent portfolio to Immunex for its product ENBREL®. In exchange for a worldwide, co-exclusive license covering p75TNFR:Fc fusion proteins such as ENBREL, Immunex will pay Genentech an initial license fee and royalties on sales of ENBREL from the date of product launch and continuing for the life of the Genentech patents.

Immunoadhesins are genetically engineered, fusion proteins that combine certain structural features of antibodies with high-affinity cell surface receptors. The resulting molecule can inhibit the activity of factors that normally bind to the receptors in the body. ENBREL is a soluble receptor fusion protein, and is the first product utilizing immunoadhesin technology to be approved by the U.S. Food and Drug Administration (FDA) for medical use.

"We are pleased that this deal has been completed, as we have anticipated for some time. This intellectual property strengthens the overall ENBREL patent estate," said Ed Fritzky, chairman and chief executive officer of Immunex.

"As a pioneer in the research of immunoadhesins, Genentech has been issued a number of fundamental patents covering this class of compounds. This is the first license agreement under our immunoadhesin patent portfolio, and we are pleased to have Immunex as our first licensee. We believe immunoadhesins hold great promise for treating a wide variety of human diseases," said Arthur D. Levinson, Ph.D., president and chief executive officer of Genentech.

The first in a new class of rheumatoid arthritis (RA) drugs known as biologic response modifiers, ENBREL is an entirely new approach to the management of rheumatoid arthritis. ENBREL acts by binding tumor necrosis factor (TNF). TNF is one of the dominant cytokines or proteins that play an important role in the cascade of reactions that cause the inflammatory process of RA. ENBREL competitively inhibits the binding of TNF molecules to the TNF receptor (TNFR) sites. The binding of ENBREL to TNF renders the bound TNF biologically inactive, resulting in significant reduction in inflammatory activity.

The FDA approved ENBREL on November 2, 1998, to treat moderately to severely active rheumatoid arthritis. ENBREL is currently indicated for the reduction in signs and symptoms of moderately to severely active rheumatoid arthritis in patients who have an inadequate response to one or more disease-modifying anti-rheumatic drugs (DMARDs). ENBREL is also indicated for the treatment of moderately to severely active polyarticular-course juvenile rheumatoid arthritis (JRA).

The most frequently reported adverse events in studies with ENBREL were mild to moderate injection site reactions. The long-term effects of ENBREL treatment, on the development or course of an active and/or chronic infection, malignancy and autoimmune disease are unknown. Patients with a serious infection, including sepsis, or who are allergic to ENBREL or any of its components should not take ENBREL. If patients develop an infection while on ENBREL, they should talk with their doctor immediately and be monitored closely. ENBREL should not be initiated in patients with active infections, including chronic or localized infections. Physicians should exercise caution in patients with a history of recurring infections or with underlying conditions, which may predispose them to infections, such as advanced or poorly controlled diabetes.

Immunex and Wyeth-Ayerst market ENBREL in North America. Other Wyeth-Ayerst affiliates will market ENBREL outside of North America. Additional information about ENBREL, including full prescribing information, can be found on the company-sponsored web site at www.ENBREL.com or by calling toll-free 1-888-4ENBREL (1-888-436-2735).

Genentech, Inc. is a leading biotechnology company that discovers, develops, manufactures and markets human pharmaceuticals for significant unmet medical needs. Twelve of the currently marketed biotechnology products stem from Genentech science. Genentech markets seven biotechnology products directly in the United States. The company has headquarters in South San Francisco, California, and is traded on the New York Stock Exchange and the Pacific Exchange under the symbol GNE.

Immunex Corporation is a biopharmaceutical company dedicated to developing immune system science to protect human health. The company's products offer hope to patients with cancer, inflammatory and infectious diseases.

American Home Products (AHP) owns a majority interest in Immunex. AHP is one of the world's largest research-based pharmaceutical and health care products companies. It is a leader in the discovery, development, manufacturing and marketing of prescription drugs and over-the-counter medications. It is also a leader in vaccines, biotechnology, agricultural products, and animal health care.

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