Phase 2 Results of Rigel’s R788 Show Clinical Benefit in Diffuse Large B-Cell Lymphoma and CLL

December 7, 2008

SAN FRANCISCO, Dec. 7 /PRNewswire-FirstCall/ — Results of the Phase 2
clinical trial of R788 (fostamatinib disodium) in patients with relapsed or
refractory B-Cell non-Hodgkin’s lymphoma (NHL) will be presented today at a
plenary session during the 50th Annual American Society of Hematology (ASH)
Meeting. The results affirm preliminary reports that Rigel’s oral Syk
inhibitor is well-tolerated by these patients and shows therapeutic benefit in
patients suffering from diffuse large B-Cell lymphoma (DLBCL) and chronic
lymphocytic leukemia/small lymphocytic lymphoma (CLL/SLL).

Rigel will host a conference call today at 4:00 p.m. PST to discuss these
results (see conference call details below).

“Despite the fact that the patients enrolled in this trial had advanced
disease and had failed treatment with marketed therapies, a significant number
of them were particularly responsive to Syk inhibition with R788,” said

Jonathan Friedberg, M.D., M.S.Sc., Associate Professor of Medicine, James P.
Wilmot Cancer Center, University of Rochester and lead investigator for the
clinical trial. “I am encouraged by this data and look forward to conducting
additional trials of R788, particularly in patients with DLBCL and CLL/SLL
types of non-Hodgkin’s lymphomas,” he added.

              Phase 2 Results: R788 in NHL Patients - 200 mg bid

                                       Patients      Overall     % Patients
    NHL Type                        (total n=68)     Response     Responding
    DLBCL                                23               5           22%
    Follicular NHL                       21               2           10%
    Other NHL*                           24
      - CLL/SLL                          11               6           55%
      - MCL                               9               1           11%

    * Other NHL patients included 11 with CLL/SLL, 9 with Mantle cell NHL, 1
      with Lymphoplasmacytic NHL and 3 with MALT/MZL.  The 4 patients with
      Lymphoplasmacytic and MALT are not referenced in the above table as
      they did not show a response to treatment.

Clinical Trial Design

This clinical trial was conducted in two Phases. Phase 1 included a small
group of patients and resulted in the selection of the dosing regimen employed
in Phase 2. Nearly equal numbers of patients were enrolled in the three Phase
2 groups that included, respectively: DLBCL, follicular lymphoma (FL) and
other non-Hodgkin’s lymphomas (specifically CLL/SLL, MCL, MALT, marginal zone,
and lymphoplasmacytic). Prior to enrollment in the R788 trial, all patients
enrolled in the clinical trial had received various standard-of-care
treatments for their disease, including combination chemotherapy, and had
failed to respond to those therapies or suffered a relapse of the disease. A
total of 68 patients received 200 mg PO bid (orally, twice daily) of R788
until disease progression occurred. Response to treatment was evaluated using
standard NHL response criteria (The Cheson Criteria). Treatment-related
adverse events included cytopenias, fatigue, diarrhea/abdominal discomfort and
hypertension. Most adverse events were mild to moderate and were reversible.
Four patients are continuing to receive R788, including 2 from the CLL/SLL
group and 1 from the DLBCL group.

B-Cell Lymphoma and Syk Inhibition

Lymphoma affects an estimated 500,000 people in the United States, with
332,000 of them suffering from non-Hodgkin’s lymphoma. Diffuse large B-cell
lymphoma is the most common type of NHL and is generally categorized as
aggressive, marked by rapidly growing tumors in the lymph nodes, spleen,
liver, bone marrow and other organs. A variety of treatment options for NHL
exist, including chemotherapy and radiation, but the five-year survival rate
for NHL patients is estimated to be around 50%. Even for those who respond to
treatment, recurrence of the disease is common.

A growing field of research on the cellular signaling associated with
these lymphomas indicates that inhibiting Syk (spleen tyrosine kinase) in
aberrant cells may control spread of the disease. Two additional research
studies on the topic are also being presented at the ASH meeting. They are:
Abstract 377, entitled “BCR, Signaling Diversity in Human Lymphoma B Cells
Correlates with Follicular Lymphoma Patient Clinical Outcomes” and Abstract
802, entitled “BCL-6 Regulates Tonic BCR Signaling in Diffuse Large B-Cell
Lymphomas.” Further information on R788 in B-cell lymphoma is available at
Rigel’s website: http://www.rigel.com/rigel/lymphoma.

Conference Call and Webcast Information

To access the live call, please dial 800-561-2693 (domestic) or
617-614-3523 (international) 10 minutes prior to the start time and use the
passcode 36883961. A replay of the call will be available, in webcast and
podcast formats, at approximately 6:00 p.m. PST on December 7, 2008 through
December 14, 2008. To access the replay, please dial 888-286-8010 (domestic)
or 617-801-6888 (international) and use the passcode 47095093. The conference
call will also be webcast live and can be accessed from Rigel’s website at
http://www.rigel.com. Please connect to Rigel’s website several minutes prior
to the start of the live webcast to ensure adequate time for any software
downloads that may be necessary.

About Rigel (http://www.Rigel.com)

Rigel is a clinical-stage drug development company that discovers and
develops novel, small-molecule drugs for the treatment of
inflammatory/autoimmune diseases and cancer, as well as viral 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.

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

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


Source: newswire

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