press release archive

Rigel Presents Preclinical Data at the 68th Annual Scientific Meeting of the American College of Rheumatology

Rigel's R406 Shows Statistical Reduction of Collagen-Induced Arthritis in Animal Model

South San Francisco, CA - October 20, 2004

Rigel Pharmaceuticals, Inc. (Nasdaq: RIGL) today announced that data from a recent study of R406, the company’s lead compound for the treatment of rheumatoid arthritis, will be presented at the American College of Rheumatology (ACR) Annual Scientific Meeting in San Antonio, Texas on October 20, 2004. The data presented in the poster session suggests that Rigel’s R406 compound, an inhibitor of syk kinase, shows a statistically significant reduction in arthritis severity.

The presentation, entitled “Inhibition of Fcg Receptor Signaling Supresses Collagen-Induced Arthritis and Reduces Clearance of IgG Antibodies,” will be presented by Ernest Brahn, M.D., Professor of Medicine and Rheumatology Program Director at the UCLA School of Medicine. Dr. Brahn will present data from a 28-day study of Rigel’s R406 compound, which was tested in a rat collagen-induced arthritis (CIA) model. Dr. Brahn observed a significant dose-related reduction in arthritis severity that was evident within seven days of therapy and continued to improve throughout the study. The data concluded that R406 significantly reduced the severity of established CIA.

“Rigel’s R406 has shown very favorable preclinical results,” said Dr. Brahn. “Based on the compound’s novel mechanism of action, positive and encouraging data, there is great potential for R406 to move into the clinic as an entirely new class of autoimmune therapeutic."

Rheumatoid Arthritis: Current Treatments and Market Opportunities
Rheumatoid arthritis (RA) is a chronic inflammatory disease affecting multiple tissues, but typically producing its most pronounced symptoms in the joints. It is often progressive and debilitating. The chronic inflammation of joints leads to the destruction of the soft tissue as well as to erosion of the articular surfaces of the bone. The disease is estimated to affect nearly one percent of the U.S. population, approximately 2.1 million people. (1)

Currently, RA is not well treated with most therapies having significant potential side effects or other shortfalls. Today, RA patients receive multiple drugs depending on the extent and aggressiveness of the disease. Patients with a mild-to-moderate form of the disease are offered a non-steroidal anti-inflammatory drug (NSAID) or a Cox-2 inhibitor. As the disease progresses, these drugs are then layered with more potent and potentially more toxic therapies. NSAIDs are supplemented with steroids and then a DMARD (disease-modifying anti-rheumatic drug) such as methotrexate, an anti-cancer agent. Due to serious side effects, it is highly desirable to reduce patient reliance on both steroids and conventional DMARDs such as methotrexate. The other major class of RA drugs are the TNF-blocking agents. These block only the inflammatory mediator TNF and are delivered via injection. Rigel believes its syk kinase inhibitors have the potential to achieve better efficacy than current agents treating RA by blocking all major inflammatory mediators, including TNF, various interleukins and other mediators.

How R406 Works:
R406 is a syk kinase inhibitor that has demonstrated inhibition of mast cell and B cell activation by both IgE and IgG, thus blocking major inflammatory mediators. R406 has been shown effective in preliminary animal models of arthritis and appears to be well tolerated in preclinical studies. Rigel believes that R406 may become a first-line DMARD with greater efficacy, safety and improved delivery and patient compliance, and thus may be used early in the course of the disease before significant bone and cartilage damage occurs.

About American College of Rheumatology
The American College of Rheumatology (ACR) and the Association of Rheumatology Health Professionals (ARHP), a division of the ACR, are organizations of physicians, health professionals and scientists serving their members through programs, including education and research. Through these programs, the ACR and the ARHP foster excellence in the care of people with rheumatic and musculoskeletal diseases.

About Rigel (www.rigel.com)
Rigel's mission is to become a source of novel, small-molecule drugs to address large, unmet medical needs. The company has initiated four development programs: asthma/allergy, hepatitis C, rheumatoid arthritis and oncology. Rigel has begun clinical testing of its first two product candidates, R112 for allergic rhinitis and R803 for hepatitis C, and expects to begin clinical trials of R406 for the treatment of rheumatoid arthritis by the end of 2004, which is expected to be followed by clinical trials for product candidates in oncology and asthma.

This press release contains "forward-looking" statements, including statements related to Rigel's plans to pursue clinical development of product candidates and the timing thereof and the potential efficacy of product candidates. Any statements contained in this press release that are not statements of historical fact may be deemed to be forward-looking statements. Words such as "will," "plans," "intends," "expects" and similar expressions are intended to identify these forward-looking statements. There are a number of important factors that could cause Rigel's results to differ materially from those indicated by these forward-looking statements, including risks that early-stage drug discovery and development might not successfully generate good product candidates and that the results of preliminary studies do not necessarily predict clinical or commercial success, and larger, later-stage clinical trials may fail to confirm the results observed in the preliminary studies, as well as other risks detailed from time to time in Rigel's SEC reports, including its Annual Report on Form 10-K for the year ended December 31, 2003 and its Quarterly Report on Form 10-Q for the quarter ended June 30, 2004. Rigel does not undertake any obligation to update forward-looking statements.

Rigel Contacts:
Rigel Pharmaceuticals
Raul Rodriguez
650-624-1302

Schwartz Communications
Melinda Bagatelos or
Ayanna Anderson
415-512-0770
rigel@schwartz-pr.com