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Rigel to Present Update on Hepatitis C Drug Development Program

New Research Indicates that Drug Candidate Significantly Decreases Viral Replication in Disease Model

- July 09, 2002

Rigel Pharmaceuticals, Inc. (Nasdaq: RIGL) will present encouraging data from the company's hepatitis C drug development program, showcasing a potentially dramatic new strategy for treating this increasingly prevalent disease. The presentation will take place on Thursday, July 11, at the International Meeting on Hepatitis C and Related Viruses, the major annual conference in the field being held this week in San Diego.

Rigel will present an update on the company's full range of hepatitis C virus (HCV) research, with particular emphasis on its lead focus in this area, a type of small-molecule drug able to block viral replication. This approach is substantially different from the current treatment standard, interferon-alpha, which primarily works indirectly to boost the immune system. In contrast, Rigel's compound appears to target the virus directly, by interfering with a viral protein involved in replication. The company's research in HCV model systems suggests that this type of molecule could dramatically inhibit the ability of the virus to reproduce.

"We've studied these drug candidates biochemically, at the cellular level and in animal systems, and we believe this family of molecules to be both potent, that is, to have significant ability to block viral replication, as well as specific, meaning that they target the virus to the relative exclusion of other cellular mechanisms." said Donald Payan, M.D., Rigel's executive vice president and chief scientific officer.

Another advantage of Rigel's drug candidates is that, because they are small molecules rather than large proteins, they can be more readily manipulated to enhance the drug's profile. Rigel intends to scrutinize the various viral inhibitors in its compound library and select a lead molecule to move into clinical evaluation. The company plans to file an Investigational New Drug (IND) application for its HCV drug with the U.S. Food and Drug Administration next year.

It is estimated that over 170 million people worldwide are infected by the hepatitis C virus, with more than 4 million cases in the United States. Approximately 85 percent of those who contract the disease remain chronically infected. Interferon-alpha is ineffective in a significant portion of HCV-infected individuals, and an increasing number of patients are developing drug resistance. Consequently, there is an urgent need to develop more effective and more direct antiviral agents.

About Rigel Pharmaceuticals, Inc.
Rigel Pharmaceuticals, Inc. is a drug discovery and development company that uses advanced functional genomics tools to discover novel drug targets that can be used to develop orally administered small molecule drugs. Rigel's technology is designed to identify molecules that play an important role in regulating a human cell's response to disease by testing a very large number of proteins in a very large number of cells to determine which proteins will change a cell's response to the disease. Rigel currently has ten product development programs underway, with five programs being proprietary programs in the areas of asthma/allergy, rheumatoid arthritis and inflammatory bowel disease, cancerous tumor growth and hepatitis C. Rigel expects to begin clinical trials during 2002 with one or more drug candidates from these five programs. In addition to the Rigel-owned programs, the company has five joint programs with its corporate partners in the product development areas of asthma/allergy, autoimmunity, transplant rejection and two programs in cancerous tumor growth. With Rigel's support, one of the company's partners is conducting an additional program in chronic bronchitis at its premises. Rigel has multi-year collaborations with Pfizer Inc., Cell Genesys, Inc., Johnson & Johnson Pharmaceutical Research & Development, L.L.C. and Novartis Pharma A.G. Rigel is based in South San Francisco, California.

This press release contains "forward-looking" statements, including statements related to Rigel's drug development programs and clinical trial plans. 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 "believes," "anticipates," "plans," "expects," "will" and similar expressions are intended to identify forward-looking statements. There are a number of important factors that could cause our results to differ materially from those indicated by these forward-looking statements, including the 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, 2001. Rigel does not undertake any obligation to update forward-looking statements.