Amphastar Pharmaceuticals, Inc.
Amphastar Pharmaceuticals, Inc. (AMPH) Stock Ownership
Institutional vs insider vs public ownership from 13F and float data — top holders, activity, and insider trades below.
SEC 13F · FMP · AMPH · as of Sep 30, 2025
Ownership Breakdown
246
Institutional Holders
▼ 3 vs Q2
$872.76M
Total Inst. Value
▲ $119.53M vs Q2
44.09M
Shares Outstanding
freeFloat 74.48%
32.75M
13F Shares Held
▼ 24,121 vs Q2
Institutional ownership = 13F shares ÷ total outstanding. Insider % = 100 − free float. Public % = free float − institution %. Data: FMP /symbol-positions-summary + /shares-float + SEC EDGAR.
Top Institutional Holders
AMPH largest shareholders · institutional ownership
Q3 2025 · SEC 13F
Showing top 10 holders
| Holder | Shares | % Owned | Weight | Value | Reported | Change |
|---|---|---|---|---|---|---|
BLACKROCK, INC. pharmaceutical preparations | 5.49M | 11.68% | 11.68% | $146.18B | Nov 12, 2025 | ▼ 183.7K |
VANGUARD GROUP INC pharmaceutical preparations | 2.63M | 5.60% | 5.60% | $70.12B | Nov 7, 2025 | ▼ 55.9K |
TD ASSET MANAGEMENT INC pharmaceutical preparations | 1.93M | 4.11% | 4.11% | $51.48B | Nov 10, 2025 | ▼ 103.0K |
DIMENSIONAL FUND ADVISORS LP pharmaceutical preparations | 1.76M | 3.74% | 3.74% | $46.79B | Nov 12, 2025 | ▲ 128.8K |
STATE STREET CORP pharmaceutical preparations | 1.50M | 3.20% | 3.20% | $39.99B | Nov 14, 2025 | ▼ 75.5K |
FULLER & THALER ASSET MANAGEMENT, INC. pharmaceutical preparations | 1.35M | 2.88% | 2.88% | $36.08B | Nov 13, 2025 | ▲ 90.2K |
BOSTON TRUST WALDEN CORP pharmaceutical preparations | 1.17M | 2.50% | 2.50% | $31.26B | Oct 17, 2025 | ▼ 3.3K |
EPOCH INVESTMENT PARTNERS, INC. pharmaceutical preparations | 1.13M | 2.42% | 2.42% | $30.22B | Nov 13, 2025 | ▼ 107.4K |
GEODE CAPITAL MANAGEMENT, LLC pharmaceutical preparations | 922.6K | 1.97% | 1.97% | $24.59B | Nov 12, 2025 | ▼ 50.7K |
MARSHALL WACE, LLP pharmaceutical preparations | 874.1K | 1.86% | 1.86% | $23.29B | Nov 13, 2025 | ▲ 25.4K |
Data from SEC Form 13F filings. Ownership bar normalised to largest holder. Change flags: isNew / isSoldOut / changeInSharesNumber (FMP extract-analytics/holder).
Institutional Activity
Q3 2025 vs prior quarter
Q3 2025
25
Increased
+2.36M shares3
New Positions
first time holders21
Decreased
−1.45M shares0
Sold Out
fully exitedNet shares change (top 50)
+915.8K
+2.36M / −1.45M
Net new holders
+7
3 new / 0 exited
Based on top 50 institutional holders by position size. Fields: isNew, isSoldOut, changeInSharesNumber (FMP extract-analytics/holder, limit=50).
Insider Buying vs Selling
AMPH insider trading · insider activity
Source: SEC Form 4
12
Buy transactions
1
Sell transactions
12.00
Buy/Sell ratio
$0M
Total disposed
Recent Insider Transactions
Showing 10 most recent · Common Stock only
| Name · Role | Date | Type | Shares | Price | Value | After Trans. | Filing |
|---|---|---|---|---|---|---|---|
PRINS RICHARD K director | Jun 1, 2026 | Award | 8,143 | — | — | 37.6K | Form 4 ↗ |
PRINS RICHARD K director | Aug 19, 2024 | Gift | 1,500 | — | — | 29.5K | Form 4 ↗ |
PRINS RICHARD K director | Jun 1, 2026 | Award | 17,365 | $18.42 | $319.9K | 17.4K | Form 4 ↗ |
Lee Howard director | Jun 1, 2026 | Award | 8,143 | — | — | 160.1K | Form 4 ↗ |
Lee Howard director | Jun 2, 2026 | Tax Withhold | 769 | $18.45 | $14.2K | 159.3K | Form 4 ↗ |
Lee Howard director | Jun 1, 2026 | Award | 17,365 | $18.42 | $319.9K | 17.4K | Form 4 ↗ |
ZASLOFF MICHAEL A director | Jun 1, 2026 | Award | 8,143 | — | — | 37.7K | Form 4 ↗ |
ZASLOFF MICHAEL A director | Jun 1, 2026 | Award | 17,365 | $18.42 | $319.9K | 17.4K | Form 4 ↗ |
Gerst Diane G. director | Jun 1, 2026 | Award | 8,143 | — | — | 31.9K | Form 4 ↗ |
Gerst Diane G. director | Jun 1, 2026 | Award | 17,365 | $18.42 | $319.9K | 17.4K | Form 4 ↗ |
Source: /insider-trading/search (FMP stable). Buy/Sell direction: acquisitionOrDisposition A=Buy, D=Sell. RSU vesting (M-Exempt) excluded from sentiment bar. All data from SEC EDGAR public filings.
About institutional & insider ownership
Amphastar Pharmaceuticals, Inc. (AMPH) is primarily owned by institutional investors, who hold approximately 74.3% of total shares outstanding. Company insiders own approximately 25.52%, while retail and public investors account for the remaining 0.21%.
The largest institutional shareholder of Amphastar Pharmaceuticals, Inc. is BLACKROCK, INC., holding approximately 5.49 million shares — equal to 11.68% of outstanding shares — as of September 30, 2025.
A total of 246 institutional investors currently hold AMPH stock, with a combined institutional value of approximately $872,758,368 as of the most recent 13F filing period.
Frequently asked questions
AMPH ownershipAmphastar Pharmaceuticals, Inc. (AMPH) is primarily owned by institutional investors, who hold approximately 74.3% of shares. The largest shareholder is BLACKROCK, INC. with a 11.68% stake. Company insiders hold 25.52%. Data sourced from SEC Form 13F as of September 30, 2025.