Amphastar Pharmaceuticals, Inc.
Ownership
Ownership Structure
Who owns Amphastar Pharmaceuticals, Inc. (AMPH)? This page shows the largest institutions and funds, the ownership structure and the latest insider transactions. 73.6% of the shares are freely tradable; institutional investors hold 76.5%.
Largest Shareholders
Institutions
| Name | Stake (%) | Shares | Change (%) | Date |
|---|---|---|---|---|
| BlackRock Inc | 12.28 | 5,224,934 | -3.6 | 06/30/2026 |
| Dimensional Fund Advisors, Inc. | 5.42 | 2,305,107 | +13.7 | 06/30/2026 |
| State Street Corp | 3.86 | 1,642,126 | +2.2 | 06/30/2026 |
| Vanguard Capital Management, LLC | 3.48 | 1,481,952 | -4.0 | 06/30/2026 |
| American Century Companies Inc | 2.77 | 1,176,626 | +15.6 | 06/30/2026 |
| Marshall Wace Asset Management Ltd | 2.51 | 1,066,322 | +4.0 | 06/30/2026 |
| Geode Capital Management, LLC | 2.28 | 969,840 | -0.7 | 06/30/2026 |
Funds
| Name | Stake (%) | Shares | Change (%) | Date |
|---|---|---|---|---|
| iShares Core S&P Small-Cap ETF | 4.40 | 1,873,133 | +0.0 | 09/30/2026 |
| Avantis US Small Cap Value ETF | 3.06 | 1,300,537 | +0.4 | 09/30/2026 |
| TD U.S. Capital Reinvestment I | 2.31 | 981,526 | -5.0 | 12/31/2025 |
Largest reported positions according to regulatory filings; stake as a percentage of shares outstanding, change versus the previous filing. Source: fundamentals data.
Insider holdings
| Person | Role | Shares | Value | As of | Type |
|---|---|---|---|---|---|
| Zhou Rong | SENIOR EVP, PRODUCTION CENTER | 169,203 | 4,737,684 $ | Sep 16, 2026 | direct |
| Peters William J | CFO, EVP & TREASURER | 168,707 | 4,723,796 $ | Sep 21, 2026 | direct |
| Prins Richard K | Director | 29,625 | 829,500 $ | Aug 11, 2026 | direct |
| Pierce Anthony T | Director | 7,886 | 220,808 $ | Jul 9, 2026 | direct |
Holdings as of each person's most recent SEC Form 4 filing — excluding options and RSUs, which are not shares yet. Holdings may have changed between two filings.
Insiders
Insider Transactions
| Date | Person | Role | Type | Shares | Price | Value |
|---|---|---|---|---|---|---|
| Sep 21, 2026 | Peters William J | CFO, EVP & TREASURER | Sell | 4,139 | 25.00 | 103,475 |
| Sep 16, 2026 | Zhou Rong | SENIOR EVP, PRODUCTION CENTER | Sell | 10,000 | 23.94 | 239,404 |
| Sep 16, 2026 | Zhou Rong | SENIOR EVP, PRODUCTION CENTER | Other | 10,000 | 13.35 | 133,500 |
| Sep 2, 2026 | Zhou Rong | SENIOR EVP, PRODUCTION CENTER | Sell | 3,187 | 23.63 | 75,306 |
| Aug 11, 2026 | Prins Richard K | Director | Sell | 7,973 | 20.30 | 161,852 |
| Aug 7, 2026 | Peters William J | CFO, EVP & TREASURER | Sell | 8,180 | 22.48 | 183,886 |
| Aug 7, 2026 | Peters William J | CFO, EVP & TREASURER | Other | 5,053 | 19.79 | 99,999 |
| Jul 9, 2026 | Pierce Anthony T | Director | Other | 7,886 | 0.00 | – |
Reportable transactions by officers and major shareholders from SEC Form 4 filings. "Other" includes things like stock grants and option exercises without a buy/sell character. View all insider transactions →
Data as of: November 4, 2026 · Source: fundamental data & SEC filings (annual and quarterly reports, 10-K/10-Q)
Note: pure fact-based analysis, not investment advice and not a solicitation to buy or sell. All figures without guarantee.