Saturday, Jul 26, 2003

New Data Support Raptiva as a Potential Long-Term Treatment for Moderate-to-Severe Plaque Psoriasis

Chicago -- July 26, 2003 --

Genentech, Inc. (NYSE: DNA) and XOMA Ltd. (Nasdaq: XOMA) today announced positive results from two clinical studies evaluating the long-term safety and efficacy of treatment with Raptiva® (efalizumab) in adults with moderate-to-severe plaque psoriasis. Study investigators will present data from these studies on Monday, July 28 from 2-5 p.m. during a peer-reviewed session at the American Academy of Dermatology ACADEMY 2003 meeting in Chicago.

Findings highlighted during the session will include data at 24 weeks from an open-label, extended treatment period following the first-time treatment with Raptiva in a randomized, double blind, placebo-controlled Phase III study. By the end of the extended treatment, 44 percent (161/368) of patients treated continuously with 1mg/kg Raptiva for up to 24 weeks achieved a 75 percent or greater improvement in Psoriasis Area and Severity Index (PASI) scores (PASI 75). Additionally, 21 months (84 weeks) of data from an open-label study evaluating the long-term safety and tolerability of continuous Raptiva will be presented. The 21-month data analysis results showed that 67 percent (130/194) of patients achieved a PASI 75 response with weekly Raptiva therapy.

"These data further support the sustained and potentially increased clinical benefit of Raptiva when administered continuously for the treatment of moderate-to-severe plaque psoriasis," said Hal Barron M.D., F.A.C.C., Genentech's vice president, Medical Affairs.

New Efficacy Data at 24 Weeks of Treatment
Data evaluating efficacy at 24 weeks from an open-label, extended treatment period following 12 weeks of treatment with Raptiva in a randomized, double blind, placebo-controlled Phase III study will be presented. In this study, a total of 368 patients received at least one dose of Raptiva during the first 12 weeks of the study and were eligible to receive once-weekly 1mg/kg doses of Raptiva for an additional 12 weeks.

At week 24, 44 percent (161/368) of patients who had received at least one dose of Raptiva during the first 12 weeks achieved a PASI 75 response. As previously reported, at week 12, 27 percent (98/369) of the patients receiving Raptiva had achieved PASI 75, suggesting an improvement in the reduction of symptoms with continued treatment. Furthermore, at week 24, 67 percent of patients (245/368) achieved a 50 percent or greater PASI improvement (PASI 50) versus 59 percent of patients (216/369) at week 12. Furthermore, 15 percent (55/368) of patients achieved a 90 percent or greater PASI improvement (PASI 90).

No new adverse events emerged during the extended 12 weeks of Raptiva treatment. The most common events that were reported in greater than or equal to five percent of patients included non-specific infection, headache, and arthritis.

"These results show a high percentage of patients experiencing a clinically meaningful response to Raptiva with 24 weeks of continuous therapy," said Kenneth Gordon, M.D., associate professor of Medicine, Division of Dermatology at Loyola University in Chicago, Illinois. "Further, Raptiva continued to be well-tolerated by patients, suggesting a positive overall clinical profile."

Long-Term Study Suggests Continued Benefit with 21 Months of Treatment
Preliminary results at 21 months (84 weeks) from an open-label, multicenter trial evaluating the long-term safety and tolerability of continuous Raptiva treatment will be presented. In this study, patients received 2 mg/kg Raptiva weekly for an initial 12 weeks and subsequently received a once-weekly dose of 1mg/kg Raptiva starting at week 13. For each successive three-month period of treatment, dropouts during that period were analyzed using their last available PASI assessment, but were excluded from the subsequent cohorts. Among the 194 patients who remained in the trial through week 84, 67 percent (130/194) of patients achieved a PASI 75 response and 86 percent (167/194) of patients achieved a PASI 50 response. Furthermore, 34 percent of patients (66/194) achieved a 90 percent or greater PASI improvement (PASI 90).

The most common adverse events during the first 12 weeks of treatment were headache, non-specific infection (e.g., common colds), chills, pain, nausea, asthenia (weakness), and fever, of which headache, chills, nausea, and fever are protocol-defined acute adverse events that mostly occurred following the first two injections of Raptiva. During continuous therapy, the incidence of adverse events decreased over time from 57 percent during weeks 13-24 to 47.9 percent during weeks 73-84. The occurrence of serious adverse events was infrequent, which is consistent with data from previous Raptiva Phase III studies.

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.

Genentech and XOMA are collaborating in the development and commercialization of Raptiva in the United States. Serono S.A., is Genentech's marketing partner outside the United States and Japan.

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 regulatory process and collaborative arrangements, 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 products being studied; analysis, interpretation and submission of scientific data; action, inaction or delay by the Food and Drug Administration and European regulators; 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 10K and in other SEC filings. Consider such risks carefully in evaluating XOMA's prospects.