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Rigel Presents Clinical Data at the American Academy of Allergy, Asthma and Immunology

Rigel’s R112 Compound, an Intranasal Syk-kinase Inhibitor, Shows Statistical Improvement for Symptoms of Seasonal Allergic Rhinitis in a Park Environment

South San Francisco, CA - March 17, 2005

Rigel Pharmaceuticals, Inc. (Nasdaq: RIGL) today announced that data from a recent Phase II clinical study of R112, Rigel’s lead compound for the treatment of allergic rhinitis, will be presented at the American Academy of Allergy, Asthma and Immunology (AAAAI) conference on Sunday, March 20, 2005 from 1:30 p.m. - 2:45 p.m. CT. Dr. Eli O. Meltzer of the Allergy & Asthma Medical Group and Research Center will present the data at a podium session that suggests Rigel’s R112 compound shows potential as a promising new treatment for seasonal allergic rhinitis.

About Allergic Rhinitis and R112
Allergic rhinitis involves inflammation of the mucous membranes of the nose, eyes, eustachian tubes, middle ear, sinuses and pharynx. This inflammation is characterized by a complex interaction of inflammatory mediators but ultimately is triggered by an immunoglobulin E (IgE)–mediated response to a foreign allergen. Rigel’s R112 compound enters mast cells, binds to an intracellular target and interrupts the signal from the IgE receptor, thus preventing downstream signaling and subsequent chemical mediator release. However, unlike common allergy drugs such as antihistamines or antileukotrienes that block only a single mediator, R112 is designed to block all of the major pathways that are triggered in an allergic attack, potentially making R112 a more effective and comprehensive drug.

Rigel’s R112 Phase II clinical studies evaluated 319 patients with seasonal allergic rhinitis and demonstrated that after 8 hours, R112 significantly reduced the global symptom complex compared to placebo (P=0.0005 and P=0.0016 on day 1 and 2, respectively). Individual symptoms were also significantly improved compared to placebo. As early as 45 minutes after dosing, R112 showed a significant improvement in symptoms over placebo. Adverse effects were indistinguishable between the groups and clinically insignificant.

About Rigel (www.rigel.com)
Rigel's mission is to become a source of novel, small-molecule drugs to address large, unmet medical needs. We have four research and development programs investigating treatments for asthma/allergy, rheumatoid arthritis, hepatitis C and oncology. Our strategy is to initiate clinical trials with at least one new product candidate annually and to pursue partnerships with pharmaceutical and biotechnology companies for late-stage clinical development and commercialization of those product candidates.

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 "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 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 Annual Report on Form 10-K for the year ended December 31, 2004. Rigel does not undertake any obligation to update forward-looking statements.