Rigel Pharmaceuticals, Inc. To Host Investor Briefing On December 15, 2005

SOUTH SAN FRANCISCO, Calif., Dec. 8 /PRNewswire-FirstCall/ -- Rigel Pharmaceuticals, Inc. announced today that it will host an investor briefing on Thursday, December 15, 2005 from 10:00 a.m. to 12:30 p.m. Eastern time in New York City. Leading clinician, Dr. Lee S. Simon of Harvard Medical School, will provide a briefing on the advancements in rheumatoid arthritis (RA) and inflammatory diseases. Rigel management will review the company’s clinical development programs and provide an update on its pipeline of product candidates. Interested parties can view the webcast of the presentation by going to www.rigel.com and following the links to the Rigel Analyst Day.

Dr. Simon is currently an Associate Clinical Professor at Harvard Medical School and head regulatory consultant with MEDACorp, a management consulting group that offers strategic advice to leading life sciences and healthcare companies. Previously, Dr. Simon was with the FDA, where he was the Division Director of the Arthritis, Analgesic and Ophthalmologic Drug Product Division. Prior to his tenure at the FDA, Dr. Simon was Director of Rheumatology Clinical Research and Associate Chief of Medicine at Beth Israel Deaconess Medical Center in Boston, MA.

Donald G. Payan, M.D., Rigel’s Chief Scientific Officer and Executive Vice President, will provide an overview of Rigel’s development programs in inflammatory diseases, including RA, cancer and other areas. Other members of Rigel’s management team will be available to provide additional information: James M. Gower, Chairman and CEO; Raul R. Rodriguez, Executive Vice President and COO; Elliott B. Grossbard, M.D., Senior Vice President of Medical Development; James H. Welch, Vice President, CFO and Corporate Secretary; and Dolly Vance, General Counsel and Vice President of Intellectual Property.

About Rigel (www.rigel.com)

Rigel is a clinical-stage drug development company that discovers and develops novel, small-molecule drugs for the treatment of inflammatory diseases, cancer and viral diseases. Our goal is to move one new product candidate for a significant indication into the clinic each year. We have achieved this goal since 2002. Our pioneering research focuses on intracellular signaling pathways and related targets that are critical to disease mechanisms. Rigel’s productivity has resulted in strategic collaborations with large pharmaceutical partners to develop and market our product candidates. We have product development programs in allergy/asthma, rheumatoid arthritis and cancer.

Forward Looking Statements

This press release contains “forward-looking” statements, including statements related to Rigel’s plans for the clinical development of product candidates and the timing thereof. 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 the risks associated with the timing and success of clinical trials and the commercialization of product candidates, as well as other risks detailed from time to time in Rigel’s SEC reports, including its Quarterly Report on Form 10-Q for the quarter ended September 30, 2005. Rigel does not undertake any obligation to update forward-looking statements.

Contact: Raul Rodriguez of Rigel, +1-650-624-1302, or invrel@rigel.com; or Carolyn Bumgardner Wang of WeissComm Partners, Inc., +1-415-946-1065, or carolyn@weisscommpartners.com, for Rigel.

Photo: NewsCom: http://www.newscom.com/cgi-bin/prnh/20030226/RIGLLOGOAP Archive: http://photoarchive.ap.orgPRN Photo Desk photodesk@prnewswire.comRigel Pharmaceuticals, Inc.

CONTACT: Raul Rodriguez of Rigel, +1-650-624-1302, or invrel@rigel.com; orCarolyn Bumgardner Wang of WeissComm Partners, Inc., +1-415-946-1065, orcarolyn@weisscommpartners.com, for Rigel

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