Public Release: 

Abgenix Reports Positive Survival Data From A Phase II Trial Of ABX-CBL In Graft Versus Host Disease

Noonan/Russo Communications

FREMONT, Calif., May 18, 1999 -- Abgenix, Inc. (Nasdaq: ABGX) reported today additional results of a Phase II clinical trial of ABX-CBL in graft versus host disease ("GVHD"). ABX-CBL is a proprietary in-licensed mouse antibody that binds to the CBL antigen. The CBL antigen is upregulated on activated immune cells, including T cells, B cells and natural killer cells. The completed trial involved patients in four dose cohorts with severe GVHD, an often fatal side effect of bone marrow transplants ("BMT"). Among patients in the three higher dose cohorts, 56% (10 of 18) survived at least 100 days from the start of treatment with ABX-CBL. This compared favorably to a 22% (2 of 9) survival rate in the low dose cohort. Robert Rivkin, M.D. of the Rocky Mountain Cancer Centers in Denver, Colorado, presented the details of the clinical trial today at the 1999 Annual Meeting of the American Society of Clinical Oncology.

"We believe the survival data reported today strengthens the preliminary safety and response rate data reported earlier," stated R. Scott Greer, president and chief executive officer of Abgenix. "We plan to initiate a pivotal Phase III clinical trial for ABX-CBL as soon as feasible after we have approval from the FDA to proceed."

In March, at the International Bone Marrow Transplant Registry ("IBMTR") meeting, it was reported that, among patients in the three higher dose cohorts, 73% (11 of 15) had a two grade or better improvement in the IBMTR GVHD Severity Scale. This compared favorably to a 25% (2 of 8) response rate in the low dose cohort.

GHVD is a life threatening complication that frequently occurs following an allogeneic BMT. BMTs are used in the treatment of patients with end stage leukemia, certain other serious cancers and immune system disorders. An allogeneic BMT procedure involves transferring marrow, the graft, from a healthy person into an immunosuppressed patient, the host. The transplant is intended to restore normal circulating immune cells to a patient whose own immune system is functionally deficient or has been damaged by the treatment of an underlying disease such as cancer and therefore does not have the ability to mount a sufficient immune response. Often a portion of the graft recognizes the host's own cells as foreign, becomes activated and attacks them, resulting in GVHD. It typically involves damage to multiple organ systems, including the skin, liver and intestines. GVHD causes extreme suffering and is the primary cause of death in allogeneic BMT patients.

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 four proprietary antibody product candidates that are under development internally, two of which are in human clinical trials. For more information about the company, visit its web site at http://www.abgenix.com.

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Statements made in this press release about Abgenix's clinical trials for ABX-CBL, XenoMouse technology, product development activities, clinical trials for other product candidates, product pipelines 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 for ABX-CBL and Abgenix's other product candidates, 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 which may affect Abgenix.


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