Sosei Group Corporation (TOKYO, Japan), a biopharmaceutical company, announced that AD 452, a novel, small molecule cytokine modulator, disease modifying anti-rheumatic drug (DMARD) being developed for the treatment of rheumatoid arthritis (RA) on a background of methotrexate, failed to meet its primary or secondary efficacy endpoints in a phase IIb clinical trial. As a consequence of these results Sosei has decided to discontinue with the development of this compound for the treatment of RA.

The randomized, double-blind, parallel group, placebo controlled, multicenter study enrolled 308 adult subjects with active RA, despite treatment with methotrexate, at 35 sites in Europe and the US to assess the efficacy, safety, and tolerability of three strengths of AD 452 administered once daily for 12 weeks. The primary efficacy endpoint was ACR20 at week 12. At 12 weeks in the AD 452 treatment groups, 36% with a 9 mg dose, 40% with 18 mg, and 40% with the top dose of 36 mg had achieved ACR20 compared to 32% in the placebo with methotrexate group. There was no statistically significant difference between the treatment groups and placebo. The trial confirmed that AD 452 has a good safety profile. Results from a phase IIa trial completed in 2005 in 98 subjects with RA on stable background therapy confirmed that AD 452 has an attractive pharmacokinetic profile following once-daily oral dosing and was well tolerated at the three dose levels tested.

Sosei, founded in 1990 by Shinichi Tamura, the former CEO of Genentech Japan, is a leading Japanese biopharmaceutical company with significant expertise in drug development. Sosei acquired AD 452 as part of its 2005 acquisition of Arakis Ltd, a UK-based, wholly-owned subsidiary focused on inflammatory disease and pain.

—A. Techman

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