press release archive

Rigel Announces Issuance of HCV and Inflammation Patents

20 Patents Issued in Last 18 Months

South San Francisco, CA - January 06, 2004

Rigel Pharmaceuticals, Inc. (Nasdaq: RIGL) today announced that it has been granted a patent (U.S. Patent No. 6,623,961) that covers any cell comprising the Hepatitis C virus (HCV) internal ribozyme entry site (IRES target) linked to a reporter gene. This patent is in addition to the 19 other U.S. patents that have been issued to Rigel during the last 18 months. These patents cover core technology useful in Rigel's HCV program, as well as its immunology and oncology programs.

Rigel's patent portfolio in HCV covers potential lead compounds, HCV targets and various methodologies. This recently issued patent relates to the discovery that an inhibitor of the HCV IRES target will inhibit HCV replication. The patent builds on Rigel's HCV patent acquired from Questcor in September 2000. Rigel recently announced that it has initiated human clinical trials with its lead HCV drug candidate, R803.

"We believe that our HCV patent portfolio is comprehensive and provides us with many different avenues to pursue for possible treatment options to this difficult disease," stated Dr. Donald G. Payan, Chief Scientific Officer and Executive Vice President of Rigel. "Rigel's research and development efforts have rapidly produced several novel approaches to identifying and developing lead candidates in each of our program areas. The growth of our patent assets is a testament to the considerable progress we have made in a short time."

Other Recently-Issued Patents
In the area of inflammation, U.S. Patent No. 6,623,980 recently issued. This patent covers screening drug candidates that bind to a certain protein believed to be involved in exocytosis. Exocytosis is the secretion of substances from cells, including substances such as histamines and cytokines which play a major role in the respiratory response to antigens.

Several patents have issued to Rigel in the area of oncology. U.S. Patent Nos. 66717102 and 6,589725 cover screening the homolog of tankyrase (taho), a cell cycle protein. As previously announced, this target has been accepted by Johnson & Johnson as part of a collaboration with Rigel. Other oncology-related patents cover various molecules and screening techniques associated with proteins and genes involved in cell cycle and apoptosis functions (U.S. Patent Nos. 6,660,511, 6569658, 6562591, 6562580, 6,555314 and 6,428,980).

In addition to the patents named above, patents related to screening using FACS (Fluorescent Activated Cell Sorting) have issued (U.S. Patent Nos. 6,461,813 and 6,455,247). This technology allows multi-parameter screening to efficiently identify potential lead molecules. Rigel will begin a licensing program for this patent estate making it available to companies interested in using FACS for identifying lead molecules. Furthermore, Rigel continues to grow its proprietary portfolio of lead compounds as well as tools and assays which allow for its high productivity in discovering potential lead compounds to treat disease states related to HCV, asthma/allergy, immunology and oncology.

About Rigel (www.rigel.com)
Rigel's mission is to become a source of novel, small-molecule drugs to meet large, unmet medical needs. Rigel has identified three lead product development programs: mast cell inhibition to treat immunologic diseases such as asthma/allergy and autoimmune disorders, antiviral agents to treat hepatitis C, and ligases, a new class of cancer drug targets. Rigel has begun clinical testing of its first two product candidates, R112 for allergic rhinitis and R803 for hepatitis C, and plans to begin clinical trials of two additional drug candidates, for the treatment of rheumatoid arthritis and asthma, by the end of 2004.

Forward Looking Statements
This press release contains "forward-looking" statements, including statements related to the timing and subject matter of future clinical trials. 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," "believes" and similar expressions are intended to identify these forward-looking statements. There are a number of important factors that could cause Rigel's results and plans to differ materially from those indicated by these forward-looking statements, including risks associated with the timing and success of clinical trials, 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, 2003 and Annual Report on Form 10-K, as amended, for the year ended December 31, 2002. Rigel does not undertake any obligation to update forward-looking statements.