News Release

Abgenix reports positive clinical data with ABX-IL8 in Psoriasis

Peer-Reviewed Publication

Porter Novelli

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 for psoriasis treatment in one or more Phase II trials to begin next year."

ABX-IL8 is a proprietary fully human monoclonal antibody developed using the company's XenoMouse technology. ABX-IL8 targets Interleukin-8 ("IL-8"), which is a cytokine that can cause unwanted inflammation by first enabling immune cells, including neutrophils, to migrate to inflammatory sites and subsequently activating them. There is substantial evidence that IL-8 contributes to a number of inflammatory diseases, including psoriasis, rheumatoid arthritis, and inflammatory bowel disease.

ABX-IL8 is being studied initially in psoriasis because of its potential to intervene at multiple steps in the disease pathology by blocking IL-8. Scientific studies have shown that IL-8 levels can be elevated 150-fold in psoriatic tissue when compared to normal tissue. In addition to contributing to the inflammation process, IL-8 is also a growth factor for skin cells that are proliferating in psoriatic tissue. Finally, IL-8 is a potent angiogenesis factor, so it may be contributing to the ingrowth of blood vessels that nourish psoriatic tissue.

Psoriasis is a chronic disease that results in plaques, a thickening and scaling of the skin accompanied by local inflammation. The disease affects approximately four to five million people in the United States and can be debilitating in its most severe form. Approximately 500,000 psoriasis patients suffer from a severe enough form of the disease to require systemic therapy with immune suppressants and ultraviolet phototherapy. The risk of serious adverse side effects associated with these therapies often requires the patients to alternate between various therapeutic modalities as a precautionary measure.

Abgenix is a biopharmaceutical company that develops and intends to commercialize antibody therapeutic products for the treatment of a variety of disease conditions, including transplant-related diseases, inflammatory and autoimmune disorders, cardiovascular disease and cancer. Abgenix has developed XenoMouse technology, which it believes enables quick generation of high affinity, fully human antibody product candidates to essentially any disease target appropriate for antibody therapy. Abgenix has collaborative arrangements with multiple pharmaceutical and biotechnology companies involving its XenoMouse technology. In addition, Abgenix has multiple proprietary antibody product candidates that are under development internally, three of which are in human clinical trials.

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Statements made in this press release about ABX-IL8, Abgenix's XenoMouse technology, product development activities and collaborative arrangements other than statements of historical fact, are forward looking statements and are subject to a number of uncertainties that could cause actual results to differ materially from the statements made, including risks associated with the success of clinical trials, the progress of research and product development programs, the regulatory approval process, competitive products, future capital requirements and the extent and breadth of Abgenix's patent portfolio. Please see Abgenix's public filings with the Securities and Exchange Commission for information about risks that may affect Abgenix.

Contact:
Kurt Leutzinger
Vice President and
Chief Financial Officer
Abgenix Inc.
510-608-6575


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