Rigel Pharmaceuticals has announced that data from a Phase I study of R406 will be presented at the American College of Rheumatology's annual meeting, currently taking place in San Diego, Calif. This novel, oral syk kinase inhibitor blocks the activation of mast cells, B cells and macrophages, which promote swelling and inflammatory responses. Data from the Phase I study was used to inform the clinical study of R788, an oral solid dosage formulation of R406.

The study evaluated the safety and pharmacokinetics of R406. Researchers first 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. The second part of the study was a placebo-controlled, 7-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. These studies established a strong correlation between R406 plasma levels and the inhibition of the target.