Veterans Blvd. South San Francisco, CA 94080 Main Phone: 650.624.1100 FAX: 650.624.1101 http://www.rigel.com Rigel s R788 Significantly Improves Rheumatoid Arthritis in Phase 2b Clinical Trial Expected and Manageable Saf

R788 Significantly Improves Rheumatoid Arthritis in Phase 2b Clinical Trial

and Manageable Safety Profile Demonstrated in TASKi2

SOUTH SAN FRANCISCO, Calif., July 9,

2009 Rigel Pharmaceuticals, Inc. (Nasdaq: RIGL) today announced that

R788 (fostamatinib disodium) produced significant clinical improvement in

rheumatoid arthritis (RA) patients in the recently completed TASKi2 Phase 2b

clinical trial of 457 patients treated for up to 6 months. The groups treated with 100 mg of R788 bid

(twice a day) and 150 mg qd (once a day) reported higher ACR 20, ACR 50, ACR 70

and DAS28 response rates than the placebo group. The efficacy results for the two dosing

groups were comparable, although the response rates for the 100 mg bid group

was uniformly greater. Consistent with

the previous Phase 2a clinical trial (TASKi1), the onset of effect of R788

occurred within one week after the initiation of therapy and was

maintained. The most frequent adverse

events were expected based on TASKi1 and appear to be manageable. The significant, early and sustained

efficacy, combined with a good safety profile, supports Rigel s plans to

conduct corporate partnership discussions with respect to R788 and initiate a

Phase 3 clinical program with R788 in RA in the first half of 2010 with a

Rigel will host a conference

call today at 8:00am EDT/5:00am PDT to discuss these results (see conference

call details below).

These are impressive

results, said James M. Gower, chairman and chief executive officer of

Rigel. The data from this clinical

trial and the soon to be completed TASKi3 clinical trial, a total of over 670

patients, will guide the design of the Phase 3 trials that we plan to launch

with a corporate partner in the first half of next year, he added.

p values compared to placebo

Note: At 6 months. All

patients were on stable doses of methotrexate throughout the clinical trial.

* The results presented are

based on an intention to treat analysis that includes all randomized patients,

regardless of how long treatment lasted.

Any patient who dropped out of the study for any reason, or for whom

month 6 data were unavailable, was considered a treatment failure (ACR

non-responder). Disease Activity Scores are based on a 28 joint count and CRP

or an ESR at week 24 (depending on which was the qualifying biomarker).

The most common clinically

meaningful drug-related adverse events noted in TASKi2 were diarrhea and

hypertension. Dose reduction options

were pre-specified in the trial protocol and in cases where doses were reduced,

patients generally completed the clinical trial with minimal safety issues. The

most common adverse events in the trial overall were related to infections,

though these were generally evenly distributed among the placebo and active

The mean increase in blood

pressure from baseline at 6 months, using a last observation carry forward methodology,

was less than 0.5 mmHg for the 150 mg qd dose group and approximately 1 mmHg

for the 100 mg bid dose group.

Approximately 18% and 23% of patients in the 150 mg qd and the 100 mg

bid dose groups, respectively, had blood pressure medication adjusted or in

some cases initiated during the course of the study, compared with 7% of the

placebo patients. The blood pressure was

successfully reduced in these patients, and their blood pressure was generally

well controlled throughout the trial.

The blood pressure medications were standard doses of common blood

pressure medications such as ACE inhibitors or diuretics.

R788 continues to perform

with strong efficacy and good tolerability in the groups of patients with RA

who have failed to respond to methotrexate, said Elliott Grossbard, M.D.,

chief medical officer for Rigel. We now

have a much better understanding of R788 s safety profile and believe that the

observed side effects may be effectively managed, he added.

Safety Results Tables

Mean Systolic BP if had

Adjustment or Initiation of BP Medication (mmHg)

TASKi2 was a 6 month,

multi-center, randomized, double blind, placebo controlled, parallel dose

clinical trial involving 457 RA patients in the U.S., Latin America and Europe

who had failed to respond to methotrexate alone. The patients were randomly assigned to two

cohorts and thus received R788 orally in either 100 mg bid (twice daily) or 150

mg qd (once daily) doses or placebo for a period of 6 months. Within in each cohort, patients were assigned

on a 2:1 basis to R788 or placebo. All

of the patients continued to receive their same stable dose of methotrexate

throughout the clinical trial period.

Efficacy assessments for

each participant were based on the American College of Rheumatology criteria,

which denotes at least a 20% (ACR 20) improvement, at least a 50% (ACR 50)

improvement, or at least a 70% (ACR 70) improvement, from the

baseline assessment at the

end of the 6 month treatment period. The ACR measurement factors include reported

physician and patient global assessment of disease activity, patient reported

pain score, and any change in C-reactive protein (CRP) in the patients

blood. The primary efficacy endpoint for

the study was the percent of patients assigned to the R788 100 mg bid dose who

were ACR 20 responders at the end of 6 months.

Secondary efficacy endpoints included a comparison of response rates for

the R788 100 mg bid and R788 150 mg qd doses at the ACR 20, ACR 50 and ACR 70

scores, as well as Disease Activity Scores (DAS) over the period of 6 months.

RA is a progressive, painful

and potentially debilitating disease, that affects more than 2 million people

in the U.S. It is a chronic inflammatory disease that puts the body s immune

system into overdrive where it ultimately causes inflammation in the joints and

destroys soft tissues, cartilage and bone.

Rigel s R788 is a novel, orally available syk kinase inhibitor designed

to interrupt the cellular signaling at the trigger point of inflammation, thereby