SEC Form 4 · Updated Daily

AMPH

— AMPHASTAR PHARMACEUTICALS, INC. Ownership

Insider 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.

Financials Ownership

Current Reporting Owners

Owner	Role	Shares Owned	As Of	Last Activity
Luo Mary Z.	10%+ Owner · Director · Officer	1,245,125	2026-03-15	F
Zhang Jack Y.	10%+ Owner · Director · Officer	1,245,125	2026-03-15	F
PETERS WILLIAM J	Director · Officer	172,846	2026-08-07	S
Zhou Rong	Officer	169,203	2026-09-02	S
Lee Howard	Director	159,350	2026-06-02	F
Liawatidewi Yakob	Director · Officer	121,892	2026-03-15	F
Petersen Floyd F.	Director	71,368	2025-12-12	S
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
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
2026-09-02	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
2026-03-09	Luo Mary Z.	Grant / award	72,462	$0.00	1,252,428
2026-03-09	Luo Mary Z.	Grant / award	180,504	$0.00	3,014,621
2026-03-09	Zhang Jack Y.	Grant / award (derivative)	149,472	$0.00	149,472
2026-03-09	Zhang Jack Y.	Grant / award (derivative)	372,338	$0.00	372,338

Source: SEC EDGAR Form 4 filings. For informational purposes only — not investment advice.