Improvement Seen with Multiple Parameters of Disease Measurement

FREMONT, Calif., November 30, 1999 - Abgenix, Inc. (Nasdaq: ABGX) today reported top level results of its Phase I/II clinical trial with ABX-IL8, a fully human antibody developed with the company's XenoMouse™ technology. Additional details will be presented at the Psoriasis: from Gene to Clinic meeting in London on December 2,1999. The multi-center, placebo controlled trial involved 45 patients with moderate to severe psoriasis. Abgenix reported that ABX-IL8 was safe and well tolerated at all dose levels tested and that a dose-dependent improvement was seen in multiple measures of disease. These efficacy measures included psoriasis area severity index (PASI), total body surface area (BSA), Physician's Global Assessment (PGA), and plaque photographs. The company also indicated that it plans to initiate a Phase II clinical trial in psoriasis during the first half of 2000. Other inflammatory disease indications including rheumatoid arthritis continue to be evaluated.

PASI analysis is a widely accepted measure of drug response in psoriasis patients. Fifty-eight percent (58%) of the patients who received ABX-IL8 1.0 mg/kg and 3.0 mg/kg, administered once every three weeks for four consecutive doses, achieved a >25% improvement, and 21% of patients achieved a >50% improvement in PASI score. This compared favorably to patients receiving 0.3 mg/kg ABX-IL8 (20% of patients achieved a >25% improvement and 0% a >50% improvement) and to patients receiving placebo (0% of patients with improvement of >25%). BSA and PGA measures and plaque photographs also showed dose dependent improvement.

"The Phase I/II trial of ABX-IL8 was primarily designed to demonstrate safety so it is a nice surprise to see such encouraging results on efficacy parameters," stated R. Scott Greer, president and CEO of Abgenix. "We will be optimizing the dose and regimen of ABX-IL8
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Contact: Kurt Leutzinger, Abgenix
510-608-6575
Porter Novelli
30-Nov-1999