Insider Transaction Report for Richard K. Prins

This filing details insider transactions by Richard K. Prins, a director at Amphastar Pharmaceuticals, Inc. On August 19, 2024, Mr. Prins disposed of 1,500 shares of Common Stock. Subsequently, on June 1, 2026, he acquired 8,143 shares of Common Stock, represented by restricted stock units vesting on June 1, 2027. Additionally, on the same date, he was granted an option to purchase 17,365 shares of Common Stock, with all shares subject to the option vesting on June 1, 2027. The post-transaction shares reflect a reconciliation adjustment as noted in footnote F1.