X0306 4/A 2015-06-15 2015-06-17 0 0001297184 Amphastar Pharmaceuticals, Inc. AMPH 0001611157 Zhang Jack Y. C/O AMPHASTAR PHARMACEUTICALS, INC. 11570 6TH STREET RANCHO CUCAMONGA CA 91730 1 1 1 0 CEO & Chief Science Officer 0001611156 Luo Mary Z. C/O AMPHASTAR PHARMACEUTICALS, INC. 11570 6TH STREET RANCHO CUCAMONGA CA 91730 1 1 1 0 COO, Chief Scientist, Chairman Common Stock 936955 D On June 12, 2015,the reporting person mistakenly filed a report on Form 4 which reported withholding of shares to satisfy the reporting person's tax liability in connection with the option exercise on June 15, 2015. This reported transaction did not occur and no shares were withheld in connection with the option exercise. Following the reportable transactions, the reporting person directly owned 936,955 shares of common stock. The error in column 5 of Table I also appears in subsequent Forms 4 filed through December 11, 2015. /s/ Ken Stupak, by power of attorney for Jack Y. Zhang 2016-02-03 /s/ Ken Stupak, by power of attorney for Mary Ziping Luo 2016-02-03