Rigel study shows R406 blocks activation of cells that promote swelling, inflammation of rheumatoid arthritis

By E. Janene Geiss

Philadelphia, Nov. 14 - Rigel Pharmaceuticals, Inc. said Monday that data from a phase 1 study of R406 shows that this novel, syk kinase inhibitor blocks the activation of mast cells, B cells and macrophages that promote swelling and inflammation.

Data from the phase 1 study was used to inform the clinical study of R788, an oral dosage formulation of R406, according to a company news release.

The phase I study evaluated the safety and pharmacokinetics of R406 in two sequential parts. Researchers conducted a placebo-controlled, escalating single-dose human safety/pharmacokinetic clinical trial that included 35 healthy volunteers. Results showed that R406 was well tolerated and showed a prolonged biological effect, officials said.

The second part of the study was a placebo-controlled, seven-day multiple-dose human safety clinical trial in an additional 24 volunteers. Results showed that R406 was well tolerated up to the 200 mg dose level and produced a prolonged biological effect with a half-life of over 12 hours, officials said.

These studies established a strong correlation between R406 plasma levels and the inhibition of the target, officials said.

"This data shows that R406 was well tolerated and a potent inhibitor of syk kinase, which may play a key role in the inflammation associated with [rheumatoid arthritis]. We believe that R406/788 will inhibit the inflammatory cascade associated with the autoimmune response in this debilitating disease and thus is a potentially promising new disease-modifying anti-rheumatic drug," Elliott B. Grossbard, Rigel's senior vice president of medical development, said in the release.

The data was presented Monday at the American College of Rheumatology's annual meeting.

South San Francisco, Calif.-based Rigel is a clinical-stage drug development company focused on small-molecule drugs for the treatment of inflammatory diseases, cancer and viral diseases.

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