1. Graduate School of Pharmaceutical Sciences, The University of Tokyo, Hongo 7‐3‐1, Bunkyo‐ku, Tokyo 113‐0033 (Japan)
2. Precursory Research for Embryonic Science and Technology (PRESTO), Japan Science and Technology Agency (JST), Chiyoda‐ku, Tokyo 102‐0075 (Japan)
3. Shionogi Co., Ltd., Discovery Research Laboratories, Osaka 561‐0825 (Japan)