Thursday, Jul 31, 2003

Genentech and XOMA Announce FDA Advisory Committee Review of Raptiva

South San Francisco and Berkeley, Calif. -- July 31, 2003 --

Genentech, Inc. (NYSE: DNA) and XOMA Ltd. (Nasdaq: XOMA) today announced that the U.S. Food and Drug Administration's Dermatologic and Ophthalmic Drugs Advisory Committee (DODAC) will review the companies' Biologics License Application (BLA) for Raptiva® (Efalizumab) for the treatment of moderate-to-severe plaque psoriasis in adults on September 9, 2003. The BLA, filed in December 2002, includes data from more than 2,700 patients treated with Raptiva and is the largest existing database of patients treated with a targeted biologic therapy for psoriasis.

"Psoriasis is a chronic disease that can have a significant physical, emotional and social impact on a patient's life. We believe the FDA Advisory Committee review is an important step toward providing physicians and their patients with a potential therapy for continuous control of moderate-to-severe plaque psoriasis," said Hal Barron, M.D., F.A.C.C., Genentech's vice president, Medical Affairs.

"We are excited to have reached this critical milestone for Raptiva and look forward to working with the FDA and Genentech toward a rigorous scientific review of the efficacy and safety data supporting the BLA," said John L. Castello, XOMA's chairman, president and chief executive officer.

Genentech and XOMA are collaborating in the development and commercialization of Raptiva in the United States. Serono S.A., Genentech's marketing partner outside the United States and Japan, announced in February 2003 that it had submitted a Marketing Authorization Application (MAA) to the European Agency for the Evaluation of Medicinal Products (EMEA) for European Union approval of Raptiva in psoriasis. Serono has also submitted Raptiva data for marketing approval in Canada, Switzerland, Australia and New Zealand and is filing in additional countries.

About Raptiva
As a targeted T-cell modulator, Raptiva is designed to block the activation of T-cells that cause psoriasis without destroying them. Raptiva has been studied as a once-weekly therapy for the continuous treatment of moderate-to-severe plaque psoriasis. In clinical trials, Raptiva was administered via subcutaneous injection and in several of the trials was self-administered by some patients in their homes. In December 2002, Genentech and XOMA filed a Biologics License Application (BLA) with the U.S. Food and Drug Administration for Raptiva for the treatment of moderate-to-severe plaque psoriasis in patients 18 years or older. More than 2,700 patients have been treated with Raptiva to date, creating the largest existing database of patients treated with a biologic therapy for psoriasis.

About Psoriasis
Psoriasis occurs when new skin cells grow abnormally, resulting in thick, red, scaly, inflamed patches. Plaque psoriasis, the most common form of the disease, affects approximately 2.3 million Americans and is characterized by inflamed patches of skin ("lesions") topped with silvery white scales. Psoriasis can be limited to a few spots or involve extensive areas of the body, appearing most commonly on the scalp, knees, elbows and trunk. Although it is highly visible, psoriasis is not a contagious disease. While there are a number of medications that may help control the symptoms of psoriasis, there currently is no known cure.

About Genentech
Genentech is a leading biotechnology company that discovers, develops, manufactures and commercializes biotherapeutics for significant unmet medical needs. Sixteen of the currently approved biotechnology products originated from or are based on Genentech science. Genentech manufactures and commercializes 11 biotechnology products 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. For additional information about the company, please visit http://www.gene.com.

About XOMA
XOMA develops and manufactures antibody and other protein-based biopharmaceuticals for disease targets that include immunological and inflammatory disorders, cancer and infectious diseases. XOMA's programs include collaborations: with Genentech, Inc. on the Raptiva antibody for psoriasis (BLA submission), psoriatic arthritis (Phase II) and other indications; and with Millennium Pharmaceuticals, Inc. on two biotherapeutic agents, CAB-2 and MLN2201, for vascular inflammation indications (preclinical and phase I, respectively). Earlier-stage development programs focus on antibodies and other compounds developed by XOMA for the treatment of cancer, retinopathies and acne. For more information about XOMA's pipeline and activities, please visit XOMA's website at http://www.xoma.com.

Regarding XOMA:
Statements made in this news release related to the DODAC review and other aspects of the regulatory process, as well as the collaborative arrangements regarding Raptiva?, 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 that 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 include those related to safety and efficacy of the product being studied; action, inaction or delay by the Food and Drug Administration, European regulators and/or their advisory bodies; analysis and interpretation by these entities and others of scientific data; changes in the status of existing collaborative relationships; the ability of collaborators to meet their obligations; and market demand for products. These risks are discussed in XOMA's most recent annual report on Form 10-K and in other SEC filings. Consider such risks carefully in evaluating XOMA's prospects.