Rigel's R788 Demonstrates Significant Improvement in Rheumatoid Arthritis in Phase 2 Clin...( Achieves Statistically Signific...),Health

Achieves Statistically Significant ACR20, ACR50 & ACR70 Results

SOUTH SAN FRANCICSO, Calif., Dec. 13 /PRNewswire-FirstCall/ -- Rigel Pharmaceuticals, Inc. (Nasdaq: RIGL) today announced that its oral syk kinase inhibitor, R788 (tamatinib fosdium), has demonstrated statistically significant results in treating Rheumatoid Arthritis (RA) patients in a recently completed Phase 2 clinical trial. Groups treated with R788 at 100mg and 150mg po bid (orally, twice daily), showed higher ACR20, ACR50, ACR70 and DAS28 response rates than the placebo group. The efficacy results for the 100mg and the 150mg dose groups were fairly comparable. Dramatically, the onset of the effect in these dose groups occurred as early as one week after initiation of therapy. We believe that the significant ACR scores and good tolerability observed in this clinical trial, and the further benefit of oral delivery may make R788 a favorable alternative to the currently marketed biological agents.

Rigel will host a conference call today at 12:30 p.m. EST to discuss these results (see conference call details below).

"This clinical study has shown that R788 treatment can achieve impressive ACR response rates," said Elliott Grossbard, M.D., senior vice president of medical development at Rigel. "In this clinical trial both the 100mg and 150mg doses improved arthritis symptoms and did so quickly. We plan to initiate the next clinical trial with R788 in RA in 2008," he added.

Efficacy Results*

Treatment Assigned Number ACR 20 ACR 50 ACR 70 DAS28-CRP <2.6,

po bid (N) % (N) % (N) % (N) % (N)

Placebo 47 38% (18) 19% (9) 4% (2) 17% (8)

50 mg
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