Rigel Commences Phase 2 Trial of R788 in Peripheral T-Cell Lymphomas

Preclinical Rationale for Clinical Trial Presented at USCAP Meeting

SOUTH SAN FRANCISCO, Calif., March 13 /PRNewswire-FirstCall/ — Rigel Pharmaceuticals, Inc. (Nasdaq: RIGL) today announced the enrollment of the first patient in a Phase 2, multi-center clinical trial of R788 (fostamatinib disodium) in patients with refractory or relapsed peripheral T-cell lymphoma (PTCL). The clinical trial’s primary objective is to assess the efficacy of R788, an orally bio-available Syk kinase inhibitor, in patients suffering from this subset of non-Hodgkin’s lymphoma that originates in the patient’s T-cells. Prior studies have suggested increased expression of Syk at the cellular level in many of these patients with PTCL.

“Since we have seen that R788 shows clinical therapeutic benefit in certain types of B-cell lymphomas and that Syk kinase appears to play an important role in certain PTCLs, we believe that R788 may offer new hope to the 12-15% of non-Hodgkin’s lymphoma patients with the T-cell variety,” said Elliott Grossbard, M.D., executive vice president and chief medical officer of Rigel.

In general, patients with PTCL have a poorer prognosis and fewer treatment options than B-cell lymphoma patients. The standard treatment regimen for PTCL, known as CHOP, fails to provide adequate or durable responses in many patients. CHOP is a treatment regimen consisting of cyclophosphamide, hydroxydoxorubicin, vincristine (oncovin) and prednisone.

Pre-clinical Results Presented at USCAP Meeting

In a related matter, results of a pre-clinical study of R788 were presented in an oral session of the United States and Canadian Academy of Pathology annual meeting in Boston this week on March 9, 2009. The presentation, entitled, “An Orally Available Syk Tyrosine Kinase Inhibitor Induces Apoptosis in Peripheral T-Cell Lymphomas Overexpressing Activated Syk” suggested that Syk may play a critical role in some PTCLs and represents a feasible therapeutic target for further clinical study.

Phase 2 Design

The Phase 2 trial will be conducted in two stages at several centers in North America with each patient receiving 200mg of R788 twice a day for a minimum of 8 weeks, or until disease progression or withdrawal from the trial. During stage one, 19 men and women with PTCL who have previously failed to respond to standard of care treatment for their disease are expected to be evaluated. Stage two is expected to include the enrollment of approximately 36 patients. Efficacy will be assessed by CT/PET scans at baseline and CT scans of the disease-involved areas at 8 weeks. Safety will be assessed by periodic physical exams, blood tests and clinical laboratory work, among others. Results of the clinical trial are expected in the second half of 2010.

In June 2008, Rigel first reported results of a Phase 2 clinical trial of R788 in the treatment of patients with relapsed or refractory B-cell non-Hodgkin’s lymphomas. R788 was well-tolerated in this patient population and showed therapeutic benefit in patients suffering from certain subcategories of the disease, especially small lymphocytic lymphoma/chronic lymphocytic leukemia (SLL/CLL) and diffuse large B-cell lymphoma. More details about the outcome of that clinical trial and the role that Syk inhibition may play in the treatment of lymphoma patients can be found at Rigel’s website, http://www.rigel.com/rigel/lymphoma.

About Rigel

Rigel is a clinical-stage drug development company that discovers and develops novel, small-molecule drugs for the treatment of inflammatory/autoimmune diseases and metabolic diseases. 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. Rigel has product development programs in inflammatory/autoimmune diseases such as rheumatoid arthritis thrombocytopenia and asthma, as well as in cancer.

This press release contains “forward-looking” statements, including statements related to the potential efficacy of R788 for the treatment of refractory or relapsed PTCL, Rigel’s plans to pursue further clinical development of R788, enrollment rate in clinical trials of R788 and the timing of results 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 “believes,” “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, potential problems that may arise in the clinical testing and approval process and Rigel’s need for additional capital, as well as other risks detailed from time to time in Rigel’s reports filed with the Securities and Exchange Commission, including its Form 10-K for the year ended December 31, 2008. Rigel does not undertake any obligation to update forward-looking statements.

    Contact: Raul Rodriguez
    Phone: 650.624.1302
    Email: invrel@rigel.com

    Media Contact: Susan C. Rogers, Alchemy Consulting, Inc.
    Phone: 650.430.3777
    Email: susan@alchemyemail.com

SOURCE Rigel Pharmaceuticals, Inc.