1. Sankyo Co., Ltd., 1-12-1 Shinomiya, Hiratsuka-shi, Kanagawa 254-8560, Japan, Tokyo University of Pharmacy and Life Science, 1432-1 Horinouchi, Hachioji-shi, Tokyo 192-0392, Japan, and Showa Pharmaceutical University, 3-3165 Higashi-tamagawagakuen, Machida-shi, Tokyo 194-8543, Japan