1. Department of Discovery Modalities, Amgen Asia R&D Center, Amgen Research, 4560 Jinke Road, Pudong, Shanghai 201210, P. R. China
2. State Key Laboratory of Drug Research, Shanghai Institute of Materia Medica, Chinese Academy of Science, 501 Haike Road, Zhang Jiang Hi-Tech Park, Pudong, Shanghai 201203, P. R. China