SEC Form 4 · Updated Daily
AMPH
— AMPHASTAR PHARMACEUTICALS, INC. OwnershipInsider and institutional ownership derived from SEC Form 4 filings. Click any owner to see their holdings across every company they’ve filed on, and how their position has changed over time.
Current Reporting Owners
| Owner | Role | Shares Owned | As Of | Last Activity |
|---|---|---|---|---|
| Applied Physics & Chemistry Laboratories, Inc. | 10%+ Owner | 6,841,887 | 2021-02-16 | S |
| Zhang Jack Y. | 10%+ Owner · Director · Officer | 2,990,052 | 2026-03-15 | F |
| Luo Mary Z. | 10%+ Owner · Director · Officer | 2,990,052 | 2026-03-15 | F |
| Koo Richard | Director | 259,289 | 2021-06-07 | A |
| Shandell Jason B. | Director · Officer | 188,575 | 2020-03-16 | A |
| Zhou Rong | Officer | 179,203 | 2026-09-16 | M |
| PETERS WILLIAM J | Director · Officer | 168,707 | 2026-09-21 | S |
| Lee Howard | Director | 160,119 | 2026-06-01 | A |
| Liawatidewi Yakob | Director · Officer | 121,892 | 2026-03-15 | F |
| Shohet Stephen B. | Director | 89,263 | 2018-12-10 | M |
| Petersen Floyd F. | Director | 73,794 | 2025-12-11 | S |
| Purchase Marilyn J. | Reporting Owner | 43,263 | 2015-03-27 | F |
| ZASLOFF MICHAEL A | Director | 37,667 | 2026-06-01 | A |
| Gerst Diane G. | Director | 31,899 | 2026-06-01 | A |
| PRINS RICHARD K | Director | 29,625 | 2026-08-11 | S |
| Maris David | Director | 19,170 | 2021-06-07 | A |
| Deflin Gayle | Director | 19,057 | 2026-06-01 | A |
| Gaugh David Russell | Director | 14,447 | 2026-06-01 | A |
| Pierce Anthony T | Director | 7,886 | 2026-07-09 | A |
Recent Filings
| Date | Owner | Activity | Shares | Price | Owned After |
|---|---|---|---|---|---|
| 2026-09-21 | PETERS WILLIAM J | Open-market sale | 4,139 | $25.00 | 168,707 |
| 2026-09-16 | Zhou Rong | Option exercise (derivative) | 10,000 | $0.00 | 19,424 |
| 2026-09-16 | Zhou Rong | Open-market sale | 10,000 | $23.94 | 169,203 |
| 2026-09-16 | Zhou Rong | Option exercise | 10,000 | $13.35 | 179,203 |
| 2026-09-02 | Zhou Rong | Open-market sale | 3,187 | $23.63 | 169,203 |
| 2026-08-11 | PRINS RICHARD K | Open-market sale | 7,973 | $20.30 | 29,625 |
| 2026-08-07 | PETERS WILLIAM J | Option exercise (derivative) | 5,053 | $0.00 | 0 |
| 2026-08-07 | PETERS WILLIAM J | Open-market sale | 8,180 | $22.48 | 172,846 |
| 2026-08-07 | PETERS WILLIAM J | Option exercise | 5,053 | $19.79 | 181,026 |
| 2026-07-09 | Pierce Anthony T | Grant / award (derivative) | 16,646 | $0.00 | 16,646 |
| 2026-07-09 | Pierce Anthony T | Grant / award | 7,886 | $0.00 | 7,886 |
| 2026-06-02 | Lee Howard | Tax withholding | 769 | $18.45 | 159,350 |
| 2026-06-01 | Deflin Gayle | Grant / award (derivative) | 17,365 | $0.00 | 17,365 |
| 2026-06-01 | Deflin Gayle | Grant / award | 8,143 | $0.00 | 19,057 |
| 2026-06-01 | Gaugh David Russell | Grant / award (derivative) | 17,365 | $0.00 | 17,365 |
| 2026-06-01 | Gaugh David Russell | Grant / award | 8,143 | $0.00 | 14,447 |
| 2026-06-01 | Gerst Diane G. | Grant / award (derivative) | 17,365 | $0.00 | 17,365 |
| 2026-06-01 | Gerst Diane G. | Grant / award | 8,143 | $0.00 | 31,899 |
| 2026-06-01 | ZASLOFF MICHAEL A | Grant / award (derivative) | 17,365 | $0.00 | 17,365 |
| 2026-06-01 | ZASLOFF MICHAEL A | Grant / award | 8,143 | $0.00 | 37,667 |
| 2026-06-01 | Lee Howard | Grant / award (derivative) | 17,365 | $0.00 | 17,365 |
| 2026-06-01 | Lee Howard | Grant / award | 8,143 | $0.00 | 160,119 |
| 2026-06-01 | PRINS RICHARD K | Grant / award (derivative) | 17,365 | $0.00 | 17,365 |
| 2026-06-01 | PRINS RICHARD K | Grant / award | 8,143 | $0.00 | 37,598 |
| 2026-03-15 | Luo Mary Z. | Tax withholding | 2,908 | $18.18 | 1,245,125 |
| 2026-03-15 | Luo Mary Z. | Tax withholding | 9,784 | $18.18 | 2,990,052 |
| 2026-03-15 | Zhang Jack Y. | Tax withholding | 2,908 | $18.18 | 1,245,125 |
| 2026-03-15 | Zhang Jack Y. | Tax withholding | 9,784 | $18.18 | 2,990,052 |
| 2026-03-15 | PETERS WILLIAM J | Tax withholding | 1,973 | $18.18 | 175,063 |
| 2026-03-15 | Zhou Rong | Tax withholding | 1,225 | $18.18 | 171,554 |
| 2026-03-15 | Liawatidewi Yakob | Tax withholding | 1,033 | $18.18 | 121,892 |
| 2026-03-10 | Luo Mary Z. | Tax withholding | 4,395 | $18.91 | 1,248,033 |
| 2026-03-10 | Luo Mary Z. | Tax withholding | 14,785 | $18.91 | 2,999,836 |
| 2026-03-10 | Zhang Jack Y. | Tax withholding | 4,395 | $18.91 | 1,248,033 |
| 2026-03-10 | Zhang Jack Y. | Tax withholding | 14,785 | $18.91 | 2,999,836 |
| 2026-03-10 | Liawatidewi Yakob | Tax withholding | 1,870 | $18.91 | 122,925 |
| 2026-03-10 | Zhou Rong | Tax withholding | 2,215 | $18.91 | 172,779 |
| 2026-03-10 | PETERS WILLIAM J | Tax withholding | 3,297 | $18.91 | 177,036 |
| 2026-03-09 | Luo Mary Z. | Grant / award (derivative) | 149,472 | $0.00 | 149,472 |
| 2026-03-09 | Luo Mary Z. | Grant / award (derivative) | 372,338 | $0.00 | 372,338 |
Source: SEC EDGAR Form 4 filings. For informational purposes only — not investment advice.