Officer and Director Stock Transaction

Liawatidewi Yakob, EVP CORP ADMIN CENTER and Director at Amphastar Pharmaceuticals, Inc., reported a transaction on March 15, 2026. The transaction involved the withholding of 1033 shares of Common Stock to cover tax liabilities associated with the vesting of restricted stock units. This transaction resulted in a post-transaction share count of 121,892 shares. Additionally, 2,459 shares are held indirectly through the Yakob and Sunmoon Trust, for which Ms. Yakob serves as trustee.