Press release
Nov 21, 2006

Sosei Announces Results of AD 452 Phase IIb Clinical Trial

Tokyo, Japan - 21 November 2006: Sosei Group Corporation (“Sosei”; TSE Mothers Index: 4565), the biopharmaceutical company, today announced that AD 452, being developed for the treatment of rheumatoid arthritis (RA), failed to meet its primary or secondary efficacy endpoints in the company’s 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 and remove AD 452 from its priority pipeline.

The trial randomized 308 subjects at 35 sites in Europe and the US into a multi-centre, double-blind, parallel group, placebo controlled study to assess the efficacy, safety and tolerability of three strengths of AD 452 administered once daily for 12 weeks to adult subjects with active RA despite a background therapy of methotrexate. The primary efficacy endpoint was ACR20 at week 12.

At 12 weeks in the AD 452 treatment groups, 36% with a 9mg dose, 40% with 18mg and 40% with the top dose of 36mg had achieved ACR20 compared to 32% in the placebo with methotrexate background group. There was no statistically significant difference between the treatment groups and placebo. The trial confirmed that AD 452 has a good safety profile.