Abgenix and SangStat Sign Antibody Therapy Agreement; Global Development and Commercialization for ABX-CBL.

Business Editors and Medical Writers

FREMONT, Calif.--(BW HealthWire)--Aug. 8, 2000

Abgenix, Inc. (Nasdaq:ABGX), and SangStat, The Transplant Company,(R), (Nasdaq:SANG) reported today that they have entered into a global co-development, supply and license agreement for ABX-CBL, an antibody developed by Abgenix. SangStat will have an exclusive worldwide license for the marketing and sale of ABX-CBL and, subject to the terms and conditions of the agreement, the right to commercialize other anti-CD147 antibodies. Abgenix will be responsible for manufacturing ABX-CBL.

"Abgenix is pleased to be collaborating with SangStat, a leading supplier of products and services in the transplant field," said R. Scott Greer, chairman and CEO of Abgenix. "We believe SangStat has the development and commercialization experience to maximize the potential of ABX-CBL, which is in a Phase II/III clinical trial for steroid resistant GVHD."

"This is a very exciting development for SangStat and is a great fit with our expertise in specialized marketing and our efforts to expand into other therapeutic areas," said Jean-Jacques Bienaime, President and CEO of SangStat. "We look forward to working with Abgenix on the development of ABX-CBL and potentially a next generation anti-CD147 product.

"Under the agreement, SangStat will make an initial license fee payment and additional milestone payments to Abgenix. Development costs will be shared equally, as would any potential profits from sales of collaboration products. SangStat and Abgenix will share responsibility for product development, including the ongoing trial.

ABX-CBL is an anti-CD147 monoclonal antibody for the treatment of steroid resistant graft versus host disease (GVHD) and is currently in a multicenter, randomized, and controlled Phase II/III study. The study is designed to demonstrate statistically significant efficacy of a single dose level of ABX CBL in comparison to a control group of patients. In an earlier Phase II trial completed in the fall of 1999, 52% of patients receiving 0.1 - 0.3 mg/kg ABX-CBL survived at least 100 days following initiation of therapy, compared to 22% of patients receiving the presumed no effect dose of 0.01 mg/kg. Approximately 25% of patients that undergo an allogeneic bone marrow transplant develop steroid resistant GVHD for which there is currently no standard approved therapy available.

SangStat shall have the right to commercialize any anti-CD147 antibody developed by Abgenix, subject to certain terms and conditions of the agreement, including ABX-RB2, the next generation fully human antibody to CD 147, generated with Abgenix's proprietary XenoMouse(TM) technology. ABX-RB2 is currently in pre-clinical development with potential target indications beyond GVHD, including solid organ transplantation and autoimmune diseases such as rheumatoid arthritis.

Abgenix Inc.

Abgenix is a biopharmaceutical company that develops and intends to commercialize antibody therapies for the treatment of such conditions as transplant-related diseases, inflammatory and autoimmune disorders, cardiovascular disease, infectious diseases, and cancer. For more information on Abgenix, visit the company's Web site at www.abgenix.com.

Abgenix developed XenoMouse technology to enable the rapid 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, genomics and biotechnology companies involving its XenoMouse technology. In addition, Abgenix has multiple proprietary antibody product candidates under development internally, three of which are in human clinical trials for graft-versus-host disease, psoriasis, rheumatoid arthritis, and cancer.

SangStat, The Transplant Company(R)

SangStat, The Transplant Company(R), is a global bio-pharmaceutical company applying a disease management approach to improving the outcome of organ, bone marrow, and stem cell transplantation. Since 1988, we have built a family of products and services to address the pre-transplant, acute care and chronic phases of transplant in the worldwide market. SangStat's The Transplant Pharmacy, is a dedicated mail order pharmacy that provides direct drug distribution and patient-focused management services. TransplantRx.com was introduced in 1999 as an on-line component and one-stop-shop providing e-commerce, content, and community for transplant recipients and providers. The company's long-term goal is to expand this success in transplantation to the broader immunosuppressive market.

Statements made in this press release about 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.

This press release contains forward-looking statements that involve risks and uncertainties, including statements regarding the company's (1) commitments, intents and goals, and (2) potential future sales, marketing efforts and product development. Forward-looking statements reflect SangStat's current views with respect to future events. Actual results may vary materially and adversely from those anticipated, believed, estimated, or otherwise indicated. In addition, competitive pressures, manufacturing or supply interruptions, regulatory matters, marketing or pricing actions, other generic competition, reimbursement practices of third party payors, product liability claims or other factors could adversely impact sales of the products; and there can be no assurance that any product candidate under development will be safe, effective or capable of being manufactured in commercial quantities at an economical cost, or that any product will not infringe the proprietary rights of others or will achieve market acceptance. Other factors that could cause actual results to differ materially include, without limitation, the expenses associated with and uncertainty related to the lawsuits pending against the MCA by Novartis with respect to SangCya oral solution. For a discussion of these and other factors that might result in different outcomes, see "Risk Factors" in SangStat's 1999 Annual Report on Form 10-K and 2000 Form 10-Qs filed with the Securities and Exchange Commission.

You can find full copies of the prescribing information for Thymoglobulin and Gengraf and copies of our latest press releases on the web at www.sangstat.com.