AMPHASTAR PHARMACEUTICALS IN AMPH
COM · Common Stock · CUSIP 03209R103 · ISIN US03209R1032
Publicly traded American pharmaceutical company
- SectorHealth care
- IndustryPharmaceutical Preparations
- HeadquartersRancho Cucamonga, CA
- Founded1996
- Websiteamphastar.com
- FilingsSEC EDGAR
* Summed across managers. Shares that two managers' reports both contain – a subsidiary's holdings that its parent's report includes too, or a sub-adviser's in its client's – are counted once ($3.8m this quarter). Holder counts are more reliable. Shares outstanding: 42.5m as of 2026-07-31, from the company's own SEC filing; the percentage can still exceed 100%: lent-out shares are counted by the lender and the buyer, and some reports overlap without saying so. Implied quarter-end price ≈ $20.20. Options: 4 managers hold calls ($561.0k notional), 1 hold puts ($209.9k).
Trends to Q2 2026
Institutional holders
Managers reporting a position, each quarter
Numbers
| Quarter | Holders |
|---|---|
| Q3 2022 | 208 |
| Q4 2022 | 212 |
| Q1 2023 | 218 |
| Q2 2023 | 246 |
| Q3 2023 | 256 |
| Q4 2023 | 277 |
| Q1 2024 | 271 |
| Q2 2024 | 269 |
| Q3 2024 | 279 |
| Q4 2024 | 264 |
| Q1 2025 | 242 |
| Q2 2025 | 246 |
| Q3 2025 | 243 |
| Q4 2025 | 236 |
| Q1 2026 | 215 |
| Q2 2026 | 211 |
Buyers vs sellers
Managers adding to or starting a position, vs cutting or selling out
Numbers
| Quarter | Bought or added | Cut or sold out |
|---|---|---|
| Q3 2024 | 137 | 125 |
| Q4 2024 | 112 | 149 |
| Q1 2025 | 109 | 144 |
| Q2 2025 | 133 | 113 |
| Q3 2025 | 117 | 125 |
| Q4 2025 | 117 | 118 |
| Q1 2026 | 89 | 141 |
| Q2 2026 | 94 | 108 |
Calls vs puts
Options held, notional value, last 4 quarters. P/C = puts ÷ calls
Numbers
| Quarter | Calls | Puts | P/C |
|---|---|---|---|
| Q3 2025 | $2.0m | $380.8k | 0.19 |
| Q4 2025 | $739.1k | $16.1k | 0.02 |
| Q1 2026 | $1.9m | $33.3k | 0.02 |
| Q2 2026 | $561.0k | $209.9k | 0.37 |
Biggest buyers
| HRT FINANCIAL LP | Added | +331.3k |
| DIMENSIONAL FUND ADVISORS LP | Added | +277.2k |
| D. E. Shaw & Co., Inc. | Added | +221.5k |
| GOLDMAN SACHS GROUP INC | Added | +176.0k |
| AMERICAN CENTURY COMPANIES INC | Added | +159.1k |
| AQR CAPITAL MANAGEMENT LLC | Added | +129.9k |
| TWO SIGMA INVESTMENTS, LP | Added | +110.0k |
| DENALI ADVISORS LLC | Added | +109.5k |
| FIRST TRUST ADVISORS LP | Added | +96.4k |
| JANE STREET GROUP, LLC | Added | +86.3k |
Biggest sellers
| TD Asset Management Inc | Sold out | -1.5m |
| Boston Trust Walden Corp | Sold out | -944.8k |
| Epoch Investment Partners, Inc. | Sold out | -898.9k |
| Invesco Ltd. | Reduced | -446.7k |
| FULLER & THALER ASSET MANAGEMENT, INC. | Reduced | -445.9k |
| MILLENNIUM MANAGEMENT LLC | Reduced | -339.6k |
| ARROWSTREET CAPITAL, LIMITED PARTNERSHIP | Reduced | -208.6k |
| BlackRock, Inc. | Reduced | -196.4k |
| RICE HALL JAMES & ASSOCIATES, LLC | Sold out | -187.3k |
| VOLORIDGE INVESTMENT MANAGEMENT, LLC | Reduced | -120.3k |
Biggest calls
| SUSQUEHANNA INTERNATIONAL GROUP, LLP | New | $226.0k11.2k shares |
| CITADEL ADVISORS LLC | Reduced | $222.0k11.0k shares |
| GROUP ONE TRADING LLC | Added | $102.9k5.1k shares |
| SIMPLEX TRADING, LLC | Reduced | $10.1k500 shares |
Biggest puts
| CITADEL ADVISORS LLC | New | $209.9k10.4k shares |
Options at notional value: the value of the shares the contracts control, as filers report them, not what the options cost. Not included in the holders, shares or buying above.
Major shareholders (over 5%)
Anyone who owns more than 5% of a class of the company's shares has to say so: on Schedule 13D if they may try to influence or control the company, on 13G if they're a passive investor, and update it as the stake changes. Each holder's latest filing, from 19 Dec 2024 on; percentages are of the share class, as the holder worked them out.
| Holder | Stake |
|---|---|
| Zhang Jack Y. 13G · exempt (held before listing) filed 2025-02-07 | 24.8% |
| BlackRock, Inc. 13G · institution filed 2025-10-17 | 11.5% |
| DIMENSIONAL FUND ADVISORS LP 13G · institution new · filed 2026-07-14 | 5.2% |
Fell to 5% or below in the last year: VANGUARD GROUP INC (0.0%, 2026-03-26)
Insider purchases and sales since 1 Apr 2026
Shares bought or sold by the company's own officers, directors and 10% owners, in the open market or privately, as they reported to the SEC on Form 4 (due within two business days of the trade). Grants, option exercises, shares withheld for tax and gifts aren't included.
Officers and directors buying vs selling
Number of people, by quarter (10% owners not included)
Numbers
| Quarter | Buying | Bought | Selling | Sold | Sold under a plan |
|---|---|---|---|---|---|
| Q4 2024 | 0 | — | 4 | $2.3m | $657.9k |
| Q1 2025 | 0 | — | 2 | $144.5k | $144.5k |
| Q2 2025 | 0 | — | 1 | $39.1k | $39.1k |
| Q3 2025 | 0 | — | 1 | $37.6k | $37.6k |
| Q4 2025 | 0 | — | 3 | $945.2k | $26.2k |
| Q1 2026 | 0 | — | 0 | — | — |
| Q2 2026 | 0 | — | 0 | — | — |
| Q3 2026 | 0 | — | 3 | $763.9k | $287.4k |
| Date | Insider | Trade | Value |
|---|---|---|---|
| 2026-09-21 | PETERS WILLIAM J CFO, EVP & TREASURER, director | Sold plan | $103.5k4.1k shares |
| 2026-09-16 | Zhou Rong SENIOR EVP, PRODUCTION CENTER | Sold | $239.4k10.0k shares |
| 2026-09-02 | Zhou Rong SENIOR EVP, PRODUCTION CENTER | Sold | $75.3k3.2k shares |
| 2026-08-11 | PRINS RICHARD K Director | Sold | $161.9k8.0k shares |
| 2026-08-07 | PETERS WILLIAM J CFO, EVP & TREASURER, director | Sold plan | $183.9k8.2k shares |
Their holding: how much the trade added to or took from the insider's holding (direct, or the trust or fund named). The same trade is sometimes reported by more than one insider, such as a fund and the director who represents it; totals count it once. A value is left blank where the reported price is far from the market price (usually a typo).
Holders, Q2 2026
| Manager | Shares | Change |
|---|---|---|
| BlackRock, Inc. 0.00% of their portfolio | 5.2m $105.4m | Reduced -196.4k |
| DIMENSIONAL FUND ADVISORS LP 0.01% of their portfolio | 2.3m $46.5m | Added +277.2k |
| STATE STREET CORP 0.00% of their portfolio | 1.6m $33.1m | Added +34.6k |
| VANGUARD CAPITAL MANAGEMENT LLC 0.00% of their portfolio | 1.5m $29.9m | Reduced -61.7k |
| AMERICAN CENTURY COMPANIES INC 0.01% of their portfolio | 1.2m $23.7m | Added +159.1k |
| MARSHALL WACE, LLP 0.02% of their portfolio | 1.1m $21.5m | Added +40.7k |
| GEODE CAPITAL MANAGEMENT, LLC 0.00% of their portfolio | 969.8k $19.6m | Reduced -6.8k |
| FULLER & THALER ASSET MANAGEMENT, INC. 0.05% of their portfolio | 949.2k $19.2m | Reduced -445.9k |
| D. E. Shaw & Co., Inc. 0.01% of their portfolio | 887.0k $17.9m | Added +221.5k |
| VANGUARD PORTFOLIO MANAGEMENT LLC 0.00% of their portfolio | 809.6k $16.3m | Added +21.8k |
| LSV ASSET MANAGEMENT 0.02% of their portfolio | 642.0k $13.0m | Reduced -9.7k |
| RENAISSANCE TECHNOLOGIES LLC 0.01% of their portfolio | 525.1k $10.6m | Reduced -28.8k |
| GOLDMAN SACHS GROUP INC 0.00% of their portfolio | 505.4k $10.2m | Added +176.0k |
| SYSTEMATIC FINANCIAL MANAGEMENT LP 0.18% of their portfolio | 437.4k $8.8m | Reduced -15.5k |
| MORGAN STANLEY 0.00% of their portfolio | 434.8k $8.8m | Added +14.5k |
| UBS Group AG 0.00% of their portfolio | 393.1k $7.9m | Reduced -27.2k |
| HRT FINANCIAL LP 0.02% of their portfolio | 387.5k $7.8m | Added +331.3k |
| DENALI ADVISORS LLC 0.76% of their portfolio | 376.0k $7.6m | Added +109.5k |
| NORTHERN TRUST CORP 0.00% of their portfolio | 371.0k $7.5m | Reduced -1.3k |
| Bridge City Capital, LLC 1.56% of their portfolio | 338.7k $6.8m | Added +3.6k |
| CHARLES SCHWAB INVESTMENT MANAGEMENT INC 0.00% of their portfolio | 310.2k $6.3m | Reduced -10.9k |
| BRIDGEWAY CAPITAL MANAGEMENT, LLC 0.11% of their portfolio | 299.0k $6.0m | Reduced -31.5k |
| ROYCE & ASSOCIATES LP 0.05% of their portfolio | 294.8k $5.9m | Reduced -111.4k |
| TWO SIGMA INVESTMENTS, LP 0.00% of their portfolio | 248.1k $5.0m | Added +110.0k |
| FIRST TRUST ADVISORS LP 0.00% of their portfolio | 247.0k $5.0m | Added +96.4k |
| Pacer Advisors, Inc. 0.01% of their portfolio | 241.2k $4.9m | Reduced -20.3k |
| Bank of New York Mellon Corp 0.00% of their portfolio | 232.3k $4.7m | Reduced -10.9k |
| VANGUARD FIDUCIARY TRUST CO 0.00% of their portfolio | 224.5k $4.5m | Reduced -6.6k |
| AQR CAPITAL MANAGEMENT LLC 0.00% of their portfolio | 208.7k $4.2m | Added +129.9k |
| PRINCIPAL FINANCIAL GROUP INC 0.00% of their portfolio | 204.2k $4.1m | Reduced -4.9k |
| NEW YORK STATE COMMON RETIREMENT FUND 0.00% of their portfolio | 181.1k $3.7m | Added +32.4k |
| JANE STREET GROUP, LLC 0.00% of their portfolio | 178.7k $3.6m | Added +86.3k |
| Empowered Funds, LLC 0.02% of their portfolio | 162.8k $3.3m | Reduced -18.5k |
| O'SHAUGHNESSY ASSET MANAGEMENT, LLC 0.01% of their portfolio | 159.4k $3.2m | Added +55.5k |
| Invesco Ltd. 0.00% of their portfolio | 158.1k $3.2m | Reduced -446.7k |
| VICTORY CAPITAL MANAGEMENT INC 0.00% of their portfolio | 149.6k $3.0m | Reduced -100.0k |
| Universal- Beteiligungs- und Servicegesellschaft mbH 0.00% of their portfolio | 139.4k $2.8m | Unchanged |
| BANK OF AMERICA CORP /DE/ 0.00% of their portfolio | 136.8k $2.8m | Reduced -37.5k |
| ALGERT GLOBAL LLC 0.03% of their portfolio | 131.4k $2.7m | Added +69.0k |
| LAM GROUP, INC. 1.31% of their portfolio | 130.8k $2.6m | Unchanged |
| NORDEA INVESTMENT MANAGEMENT AB 0.00% of their portfolio | 126.9k $2.6m | Added +3.1k |
| BESSEMER GROUP INC 0.00% of their portfolio | 121.3k $2.4m | Reduced -701 |
| ARROWSTREET CAPITAL, LIMITED PARTNERSHIP 0.00% of their portfolio | 116.7k $2.4m | Reduced -208.6k |
| Public Sector Pension Investment Board 0.01% of their portfolio | 116.6k $2.4m | Reduced -9.9k |
| Nuveen, LLC 0.00% of their portfolio | 88.4k $1.8m | Added +11.8k |
| Vanguard Global Advisers, LLC 0.00% of their portfolio | 87.6k $1.8m | Added +37.5k |
| EXCHANGE TRADED CONCEPTS, LLC 0.01% of their portfolio | 87.1k $1.8m | Added +4.6k |
| RHUMBLINE ADVISERS 0.00% of their portfolio | 80.5k $1.6m | Reduced -3.3k |
| Squarepoint Ops LLC 0.00% of their portfolio | 78.8k $1.6m | Added +50.5k |
| Legal & General Group Plc 0.00% of their portfolio | 78.3k $1.6m | Reduced -2.6k |
| ASSETMARK, INC 0.00% of their portfolio | 68.6k $1.4m | Added +14.9k |
| AMERIPRISE FINANCIAL INC 0.00% of their portfolio | 68.2k $1.4m | Reduced -10.5k |
| Robeco Institutional Asset Management B.V. 0.00% of their portfolio | 66.4k $1.3m | Unchanged |
| Swiss National Bank 0.00% of their portfolio | 64.8k $1.3m | Reduced -7.8k |
| JPMORGAN CHASE & CO 0.00% of their portfolio | 57.6k $1.2m | Reduced -47.0k |
| Jump Financial, LLC 0.01% of their portfolio | 56.8k $1.1m | New |
| ALLIANCEBERNSTEIN L.P. 0.00% of their portfolio | 56.4k $1.1m | Unchanged |
| WELLS FARGO & COMPANY/MN 0.00% of their portfolio | 55.9k $1.1m | Added +13.9k |
| CITIGROUP INC 0.00% of their portfolio | 55.8k $1.1m | Added +19.9k |
| Point72 Asset Management, L.P. 0.00% of their portfolio | 55.0k $1.1m | New |
| BNP PARIBAS FINANCIAL MARKETS 0.00% of their portfolio | 54.7k $1.1m | Reduced -101.4k |
| Creative Planning 0.00% of their portfolio | 51.4k $1.0m | Added +35.0k |
| PRICE T ROWE ASSOCIATES INC /MD/ 0.00% of their portfolio | 51.1k $1.0m | Added +6.2k |
| VOLORIDGE INVESTMENT MANAGEMENT, LLC 0.00% of their portfolio | 50.9k $1.0m | Reduced -120.3k |
| SUSQUEHANNA INTERNATIONAL GROUP, LLP 0.00% of their portfolio | 50.6k $1.0m | Added +36.0k |
| INTECH INVESTMENT MANAGEMENT LLC 0.01% of their portfolio | 49.8k $1.0m | Added +25.6k |
| SteelPeak Wealth, LLC 0.03% of their portfolio | 48.7k $982.4k | Added +222 |
| XTX Topco Ltd 0.01% of their portfolio | 46.8k $944.6k | Reduced -40.9k |
| UBS AM, a distinct business unit of UBS ASSET MANAGEMENT AMERICAS LLC 0.00% of their portfolio | 44.1k $889.2k | Reduced -11.3k |
| Polaris Capital Management, LLC 0.08% of their portfolio | 43.2k $872.4k | Unchanged |
| CALIFORNIA STATE TEACHERS RETIREMENT SYSTEM 0.00% of their portfolio | 36.2k $729.5k | Added +7.9k |
| DEUTSCHE BANK AG\ 0.00% of their portfolio | 35.3k $712.5k | Added +2.2k |
| PRUDENTIAL FINANCIAL INC 0.00% of their portfolio | 35.1k $709.0k | Reduced -15.6k |
| Y-Intercept (Hong Kong) Ltd 0.01% of their portfolio | 34.7k $700.3k | New |
| Vident Advisory, LLC 0.01% of their portfolio | 34.2k $690.6k | Added +11.0k |
| Brevan Howard Capital Management LP 0.01% of their portfolio | 34.2k $690.2k | Added +22.6k |
| Legato Capital Management LLC 0.06% of their portfolio | 34.1k $688.8k | Unchanged |
| Janney Montgomery Scott LLC 0.00% of their portfolio | 33.8k $683.0k | Added +20.0k |
| SEGALL BRYANT & HAMILL, LLC 0.01% of their portfolio | 33.3k $672.4k | Unchanged |
| SummerHaven Investment Management, LLC 0.35% of their portfolio | 32.6k $658.5k | Unchanged |
| MILLENNIUM MANAGEMENT LLC 0.00% of their portfolio | 31.8k $642.0k | Reduced -339.6k |
| SG Americas Securities, LLC 0.00% of their portfolio | 31.7k $640.0k | Reduced -1.1k |
| Assenagon Asset Management S.A. 0.00% of their portfolio | 30.4k $614.1k | Added +15.2k |
| Engineers Gate Manager LP 0.01% of their portfolio | 30.2k $609.3k | New |
| FMR LLC 0.00% of their portfolio | 29.0k $584.4k | Added +27.7k |
| CANADA LIFE ASSURANCE Co 0.00% of their portfolio | 26.8k $541.0k | Reduced -3.4k |
| State of Alaska, Department of Revenue 0.01% of their portfolio | 26.4k $531.0k | Reduced -977 |
| Advisor OS, LLC 0.03% of their portfolio | 25.4k $512.7k | Unchanged |
| ADVISORY RESEARCH INC 0.05% of their portfolio | 25.3k $511.3k | Added +2 |
| BARCLAYS PLC 0.00% of their portfolio | 25.2k $508.9k | Added +3.9k |
| FRANKLIN RESOURCES INC 0.00% of their portfolio | 25.0k $504.2k | Reduced -114.3k |
| Quadrature Capital Ltd 0.00% of their portfolio | 24.4k $493.0k | Reduced -6.1k |
| Campbell & CO Investment Adviser LLC 0.02% of their portfolio | 23.2k $468.4k | New |
| VANGUARD ASSET MANAGEMENT, Ltd 0.00% of their portfolio | 23.1k $465.2k | Unchanged |
| Thrivent Financial for Lutherans 0.00% of their portfolio | 22.3k $450.0k | Reduced -1.3k |
| NEW YORK STATE TEACHERS RETIREMENT SYSTEM 0.00% of their portfolio | 21.2k $427.0k | Reduced -645 |
| Quantinno Capital Management LP 0.00% of their portfolio | 20.8k $420.3k | New |
| MetLife Investment Management, LLC 0.00% of their portfolio | 20.8k $419.0k | Unchanged |
| RAYMOND JAMES FINANCIAL INC 0.00% of their portfolio | 19.3k $389.7k | Added +258 |
| Russell Investments Group, Ltd. 0.00% of their portfolio | 18.1k $365.4k | Added +14.7k |