Monday, Dec 20, 1999

Genentech and XOMA Announce Initiation of Anti-CD11A Phase III Clinical Trials for Psoriasis

South San Francisco, Calif. -- December 20, 1999 --

Based on promising Phase II trial results for anti-CD11a (hu1124), Genentech, Inc. (NYSE:DNA) and XOMA Ltd. (Nasdaq: XOMA) announced today that they have initiated a Phase III clinical trial for people with moderate-to-severe plaque psoriasis.

Anti-CD11a is an investigational, recombinant, humanized monoclonal antibody designed to prevent the activation of T-cells and their migration to sites of inflammation. The first Phase III randomized trial will involve approximately 30 sites throughout the United States and Canada for patients with moderate-to-severe plaque psoriasis. A second Phase III study is planned to begin in the first quarter 2000.

According to the National Psoriasis Foundation, psoriasis is a chronic skin disorder that affects approximately seven million people in the U.S. and millions of others worldwide. It occurs when new skin cells grow too rapidly, resulting in inflamed, swollen, scaly patches of skin. Psoriasis can be limited to a few spots or can involve more extensive areas of the body, appearing most commonly on the scalp, knees, elbows and trunk. Although the cause of psoriasis is unknown, increased activation, adhesion and migration of T-cells into the skin contributes to the inflammation and abnormal skin cell growth. There currently is no cure.

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 products directly in the United States. The company has headquarters in South San Francisco, California and is traded on the New York Stock Exchange under the symbol DNA.

XOMA Ltd. develops and manufactures biopharmaceuticals at facilities located in Berkeley and Santa Monica, California. Medical targets include bacterial and fungal infections, infectious complications, immunologic and inflammatory disorders. XOMA's primary drug development platform is BPI (bacterial/permeability-increasing protein), a human protein with multiple anti-infective properties.

The statements made in this press release related to product development and clinical testing, or that otherwise relate to future periods, are forward-looking statements within the meaning of Section 27A of the Securities Act of 1933 and Section 21E of the Securities Exchange Act of 1934. These statements are based on assumptions which may not prove accurate. Actual results could differ materially from those anticipated due to certain risks inherent in the biotechnology industry and for companies engaged in the development of new products in a regulated market. These risks, including those related to the timing or results of pending or future clinical trials, changes in the status of collaborative relationships, and actions by the U.S. Food and Drug Administration or the U.S. Patent and Trademark Office, are discussed in XOMA's and Genentech's most recent annual reports on Form 10-K and in other SEC filings.

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