Institutional ownership · Form 13F
AMPH institutional ownership
Amphastar Pharmaceuticals, Inc. - Common Stock: reported institutional holdings as of 2026-06-30 (filed through 2026-08-31), aggregated by StockEyes from SEC Form 13F information tables. AMPH is one of 2732 tickers in the validated publication set. Mapping coverage in this publication set: 4562 of 6046 universe tickers have at least one validated CUSIP mapping (75.5%). Latest-quarter filed value resolved to any listed ticker: 77.3%; resolved to this universe: 77.2%.
AMPH: change since the prior quarter's filings
The number of reporting managers slipped from 213 in the quarter ended 2026-03-31 to 211 in the quarter ended 2026-06-30 (-2, 0.9%). Total reported shares fell to 28,333,453 (-3,747,572, 11.7%), moving the same way as the manager count. Among the 23 managers listed as top holders in both quarters, the largest increases were DIMENSIONAL FUND ADVISORS LP (+277,160 shares) and D. E. Shaw & Co., Inc. (+221,506 shares), among 10 managers who added shares, and the largest decreases were FULLER & THALER ASSET MANAGEMENT, INC. (-445,901 shares) and BlackRock, Inc. (-196,409 shares), among 13 managers who reduced shares. TWO SIGMA INVESTMENTS, LP (248,115 shares), FIRST TRUST ADVISORS LP (246,951 shares) and 5 more entered the listed top holders; TD Asset Management Inc (1,541,044 shares in the prior quarter), Boston Trust Walden Corp (944,789 shares in the prior quarter) and 5 more dropped out of the listed top holders.
New to 13F data? Read how to read a 13F filing, or see where institutions moved overall in the Smart Money Report.
Reported totals, quarter ended 2026-06-30
211 reporting managers held 28,333,453 shares, reported value $539,513,362 exactly as filed. Values are position values transcribed from the filings, not current market prices.
Reported quarter-over-quarter change (quarter ended 2026-03-31 to quarter ended 2026-06-30): reporting managers -2, reported shares -3,747,572 (-11.68%), reported value -11.05%. These changes compare two filing snapshots.
Shares outstanding check: 42,537,944 shares reported by the issuer (SEC XBRL, period ended 2026-07-31). Reported 13F shares equal 66.6% of that figure. This page passed the publication sanity gate before listing.
AMPH in this quarter's filings
Concentration check: the largest reported position, BlackRock, Inc. with 5,224,934 shares, is 18.4% of all shares reported for AMPH this quarter. The five largest reporting managers together account for 41.8% of the reported total, so the headline total is spread across a broad manager base rather than a few holders.
Reported quarter-over-quarter change: the reporting-manager count fell by 2 versus the quarter ended 2026-03-31, and reported shares moved -11.68% (-3,747,572 shares). That is a comparison of two filing snapshots, not a record of trades on any single day.
Shares-outstanding cross-check: reported 13F shares equal 66.6% of the issuer share count used at the publication gate (42,537,944 shares, issuer period ended 2026-07-31). The gate publishes a ticker only when that relationship is plausible; lending chains can push reported totals above a simple ownership share, which is why the figure is a sanity check and not an ownership percentage.
Largest reporting managers, AMPH
| # | Manager | Shares | Value as filed | Share of reported total |
|---|---|---|---|---|
| 1 | BlackRock, Inc. | 5,224,934 | $105,439,168 | 18.4% |
| 2 | DIMENSIONAL FUND ADVISORS LP | 2,305,107 | $46,519,189 | 8.1% |
| 3 | STATE STREET CORP | 1,642,126 | $33,138,103 | 5.8% |
| 4 | VANGUARD CAPITAL MANAGEMENT LLC | 1,481,952 | $29,905,791 | 5.2% |
| 5 | AMERICAN CENTURY COMPANIES INC | 1,176,626 | $23,744,313 | 4.2% |
| 6 | MARSHALL WACE, LLP | 1,066,322 | $21,518,378 | 3.8% |
| 7 | GEODE CAPITAL MANAGEMENT, LLC | 969,840 | $19,575,036 | 3.4% |
| 8 | FULLER & THALER ASSET MANAGEMENT, INC. | 949,238 | $19,155,615 | 3.4% |
| 9 | D. E. Shaw & Co., Inc. | 887,048 | $17,900,629 | 3.1% |
| 10 | VANGUARD PORTFOLIO MANAGEMENT LLC | 809,568 | $16,337,082 | 2.9% |
| 11 | RENAISSANCE TECHNOLOGIES LLC | 525,100 | $10,596,518 | 1.9% |
| 12 | GOLDMAN SACHS GROUP INC | 505,360 | $10,198,165 | 1.8% |
| 13 | SYSTEMATIC FINANCIAL MANAGEMENT LP | 437,384 | $8,826,439 | 1.5% |
| 14 | MORGAN STANLEY | 434,840 | $8,775,081 | 1.5% |
| 15 | UBS Group AG | 393,110 | $7,932,960 | 1.4% |
Manager names and figures are transcribed from each manager's own Form 13F information table. A manager listing shares in this snapshot does not mean it holds them today.
Reported change, 2026-03-31 to 2026-06-30
| Quarter ended | Filed through | Reporting managers | Reported shares | Value as filed |
|---|---|---|---|---|
| 2026-03-31 | 2026-05-29 | 213 | 32,081,025 | $606,540,961 |
| 2026-06-30 | 2026-08-31 | 211 | 28,333,453 | $539,513,362 |
Every change figure on this page is a reported quarter-over-quarter change between filing snapshots. It is not real-time trading activity.
AMPH reported totals over time
Quarter ended 2026-06-30: 211 reporting managers · 28,333,453 reported shares · $539,513,362 value as filed.
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Quarter-end 13F filed data, long positions only; filings arrive up to 45 days after quarter end.
CUSIPs behind the AMPH total
The validated bridge mapped 1 current CUSIP(s) to AMPH for this quarter: 03209R103. Option pseudo-CUSIPs, units, warrants, and preferred classes are excluded from these common-share totals. Mapping coverage in this publication set: 4562 of 6046 universe tickers have at least one validated CUSIP mapping (75.5%). Latest-quarter filed value resolved to any listed ticker: 77.3%; resolved to this universe: 77.2%.
What this page is and is not
Form 13F reports are quarterly holdings snapshots. Managers file up to about 45 days after quarter-end, so these figures describe reported positions as of the quarter-end date, not holdings today. 13F lists reportable long positions from managers above the SEC reporting threshold and omits short positions entirely.
This page is informational only. It is not investment advice, a recommendation, or a signal to buy or sell. Source: SEC Form 13F bulk data set for filings through 2026-08-31 (period ended 2026-06-30), joined to tickers through StockEyes' validated CUSIP bridge. Methodology and coverage are documented on the institutional ownership hub.
Insider transactions for AMPH (officer and director buys and sells) are covered by InsiderTrace: insidertrace.com/stock/amph. StockEyes does not duplicate insider transaction tables.
Related StockEyes pages
Latest headlines tagged AMPH are on the market news wire. Upcoming earnings and market dates are on the events calendar. The term itself is defined in the institutional investor glossary entry, and the research workflow behind pages like this one is walked through in how to research a stock and how to compare SEC filings.