Luo Mary Z. 4

What Happened
Jack Y. Zhang, a reported 10% owner of Amphastar Pharmaceuticals, had 8,201 shares withheld to satisfy tax liabilities upon the vesting of restricted stock units (RSUs). The withholding occurred on March 4, 2026, at a reported price of $19.96 per share: 5,769 shares (≈ $115,149) and 2,432 shares (≈ $48,543), for a combined value of about $163,692. This was a tax-withholding disposition tied to RSU vesting—not an open-market sale.

Key Details

• Transaction date: March 4, 2026. Report filed March 6, 2026 (timely within the two-business-day Form 4 window).
• Shares withheld/disposed: 5,769 shares @ $19.96 (≈ $115,149) and 2,432 shares @ $19.96 (≈ $48,543); total 8,201 shares (≈ $163,692).
• Nature of transaction: F (tax withholding to satisfy tax liability on RSU vesting). This is a withholding/cashless disposition, not a market sale indicating directional trading.
• Shares held after transaction: not specified in the filing.
• Footnotes of note:
  • F1: Shares were withheld to cover the reporting person's tax liability in connection with RSU vesting.
  • F2: Some securities are held of record by Mary Z. Luo; the reporting persons are husband and wife.
  • F3: Some shares are held of record by Applied Physics and Chemistry Laboratories, Inc., which is owned by the reporting persons and The Bill Luobei Zhang 2004 Irrevocable Trust.

Context
Tax-withholding dispositions on RSU vesting are routine administrative transactions: shares are withheld (or sold to the company) to cover payroll/tax obligations and do not necessarily reflect a change in the insider’s view of the company. As a 10% owner, Zhang’s filings are principally ownership disclosures rather than routine executive trading signals.