Press release
May 31, 2010

Sosei Announces Stock Option (Stock Acquisition Rights) Allotment

Tokyo – 31 May 2010 – Sosei Group Corporation (“Sosei”; TSE, Mothers Index: 4565), a biopharmaceutical company, announces the allotment of stock options (stock acquisition rights) to directors, officers, employees, as well as to directors and employees of its subsidiaries to purchase up to an aggregate of 3,265 common shares subject to the approval of the shareholders at the Annual Shareholders Meeting on 22 June.

The price at which the stock options will be exercisable will be the mean value of the 5 business days’ closing price of Sosei shares prior to the allotment. All stock options are subject to a hold period of two years from the date of the option allotment, and will expire after 10 years from the day of allotment.