Thursday, Jul 29, 2004

Preliminary Data Showed Sustained Clinical Benefit for Moderate-to-Severe Plaque Psoriasis Patients Treated with Raptiva for 30 Months

New York -- July 29, 2004 --

Genentech, Inc. (NYSE: DNA) and XOMA Ltd. (Nasdaq: XOMA) today announced preliminary 30-month (120 weeks) results from an open-label study evaluating the safety and efficacy of long-term continuous treatment with RAPTIVA® (efalizumab) in adults with moderate-to-severe chronic plaque psoriasis. The study results were presented as a poster at the American Academy of Dermatology ACADEMY 2004 meeting in New York. The results of this study suggest that continuous, weekly dosing of RAPTIVA provided sustained clinical benefit over 2 1/2 years.

Of the 159 subjects participating in the study who completed 30 months of treatment, a 75 percent or greater improvement on the Psoriasis Area Severity Index (PASI 75) was observed in 78 percent (124/159) of patients with weekly RAPTIVA therapy. Ninety-one percent (145/159) of patients achieved a PASI 50 response, and 45 percent of patients (71/159) achieved a 90 percent or greater PASI improvement (PASI 90).

"Given that psoriasis is a chronic condition, dermatologists are looking for treatment options that can provide these patients with continuous control of their disease over the long-term," said Craig Leonardi, M.D., associate clinical professor of dermatology at St. Louis University Medical School, St. Louis, Mo., and a study investigator. "These data represent the first 30-month data available for any advanced therapy for plaque psoriasis and support the continued use of RAPTIVA as an important treatment option for patients afflicted with this chronic disease."

Study Design
In this study, 339 patients received RAPTIVA weekly for an initial 12 weeks and patients with a PASI 50 response or a static Physician's Global Assessment response of 'mild' or better after 12 weeks of treatment were eligible to continue on a once-weekly maintenance dose of 1mg/kg RAPTIVA for 12-week periods starting at week 13. Of the 339 subjects who started the study, 290 qualified for continued treatment beyond 12 weeks. 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.

"Since RAPTIVA was launched in November 2003, this novel therapy has been widely embraced by dermatologists and patients," said Ivor Caro, M.D., Genentech's medical director of dermatology. "These 30-month data give dermatologists additional insight into how RAPTIVA may be used to develop long-term treatment strategies for their moderate-to-severe plaque psoriasis patients."

Adverse events in this study were similar to what has been observed in previous clinical trials of RAPTIVA, and include headache, non-specific infection (e.g., common colds), chills, pain, nausea, asthenia (weakness), and fever, all of which diminished after the first 1-2 doses. Further, there was no evidence of accumulation or cumulative toxicity. At 30-months, the occurrence of serious adverse events was infrequent which is consistent with data from previous RAPTIVA Phase III studies.

About RAPTIVA
RAPTIVA® (efalizumab) is a humanized therapeutic antibody designed to selectively and reversibly block the activation, reactivation and trafficking of T-cells that lead to the development of psoriasis. In October 2003, RAPTIVA received U.S. Food and Drug Administration (FDA) approval for the treatment of chronic moderate-to-severe plaque psoriasis in adults 18 years or older who are candidates for systemic therapy or phototherapy. The recommended dose of RAPTIVA is a single 0.7 mg/kg SC conditioning dose followed by weekly SC doses of 1 mg/kg.

RAPTIVA is the first and only FDA approved biologic therapy that is designed to provide continuous control of chronic moderate-to-severe plaque psoriasis and can be self-administered by patients as a single, once-weekly, subcutaneous injection. In clinical studies, RAPTIVA demonstrated a rapid onset of action in the reductions of symptoms associated with psoriasis, in some patients within four weeks of initial treatment. More than 3,500 patients in the United States and Europe have been included in RAPTIVA trials to date, creating the largest existing database of patients taking part in studies with a biological therapy for psoriasis.

For full prescribing information, please visit http://www.raptiva.com.

Genentech and XOMA are collaborating on the development of RAPTIVA in the United States. Serono S.A., Genentech's marketing partner outside the United States and Japan, announced in June 2004 that it received a unanimous positive opinion from the Committee of Medicinal Products for Human Use (CHMP) recommending approval of RAPTIVA® (efalizumab) in Europe. Serono received authorization for RAPTIVA in Switzerland in March and in Argentina in May, and a positive opinion in Australia this month. Serono is awaiting the outcomes of marketing applications in a number of other territories for which it is responsible.

Important Safety Information
Common adverse events that occurred at least two percent more frequently in RAPTIVA patients than in placebo included headache, infection (mostly upper respiratory infections), chills, nausea, pain, myalgia (muscle pain), flu syndrome, fever, back pain, and acne. Five of these events (headache, chills, fever, nausea and myalgia) were predominantly acute adverse events and were principally seen following the first two injections of RAPTIVA. For the third and subsequent doses, the incidence of acute adverse events was similar between the RAPTIVA and placebo groups. Less than one percent of patients were discontinued from treatment due to acute adverse events.

RAPTIVA is an immunosuppressive agent and has the potential to increase the risk of infection and reactivate latent, chronic infections. Many immunosuppressive agents have the potential to increase the risk of malignancy. The role of RAPTIVA in the development of malignancies is not known. Serious adverse events occurring in clinical studies with RAPTIVA were serious infections (0.4% in RAPTIVA vs. 0.1% in placebo), malignancy (the overall incidence of malignancies of any kind was 1.8 per 100 patient-years for RAPTIVA-treated patients compared with 1.6 per 100 patient-years for placebo-treated patients), thrombocytopenia (0.3% RAPTIVA vs. 0.0% placebo), and worsening of psoriasis, typically upon discontinuation (0.7% in RAPTIVA vs. 0.0% in placebo).

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. Eighteen of the currently approved biotechnology products originated from or are based on Genentech science. Genentech manufactures and commercializes 12 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 under the symbol DNA. For additional information about the company, please visit http://www.gene.com.

About XOMA
XOMA is a biopharmaceutical company focused on developing and commercializing antibody and other protein-based biopharmaceuticals for disease targets that include cancer, immunological and inflammatory disorders, and infectious diseases. XOMA's proprietary and collaborative product development programs include: RAPTIVA™ for moderate to severe plaque psoriasis (marketed) and other indications in collaboration with Genentech, Inc.; XMP.629, a topical formulation of a bactericidal/permeability-increasing protein (BPI)-derived compound for acne (Phase II); MLN 2222, a recombinant protein for reducing the incidence of post-operative events in coronary artery bypass graft surgery patients with Millennium Pharmaceuticals, Inc. (Phase I); NEUPREX®, a BPI product in a study to limit complications following pediatric cardiopulmonary bypass surgery(Phase I/II); a TPO mimetic antibody to treat chemotherapy-induced thrombocytopenia in collaboration with Alexion Pharmaceuticals, Inc. (preclinical) and a multiple antibody product candidate program, including anti-CD40 mAb, for the treatment of cancer in collaboration with Chiron Corporation (preclinical). For more information about XOMA's product pipeline and antibody product development capabilities and technologies, please visit XOMA's website at http://www.xoma.com/.

Regarding XOMA:
Statements contained herein related to product development 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, including those related to safety and efficacy of the products being studied; action, inaction or delay by the U.S. Food and Drug Administration, European regulators or their advisory bodies; analysis and interpretation of scientific data by these entities and others; changes in the status of existing collaborative relationships; the ability of collaborators and other partners to meet their obligations; and market demand for products, are described in more detail in XOMA's most recent annual report on Form 10-K and in other SEC filings.