Ranked by reported Q1 2026 13F market value
Share of total reported institutional value in AMPH held by the largest 10 / 25 filers.
| # | Institution | Shares Held | Market Value | QoQ Change | Ownership % | % of Fund |
|---|---|---|---|---|---|---|
| 1 | BlackRock, Inc. | 5.4M | $106.2M | -0.7% | 12.295% | 0.00% |
| 2 | DIMENSIONAL FUND ADVISORS LP | 2.0M | $39.7M | +12.7% | 4.599% | 0.01% |
| 3 | STATE STREET CORP | 1.6M | $31.5M | +4.9% | 3.646% | 0.00% |
| 4 | VANGUARD CAPITAL MANAGEMENT LLC | 1.5M | $30.2M | — | 3.501% | 0.00% |
| 5 | TD ASSET MANAGEMENT INC | 1.5M | $30.2M | -21.5% | 3.495% | 0.02% |
| 6 | FULLER & THALER ASSET MANAGEMENT, INC. | 1.4M | $27.3M | +0.1% | 3.164% | 0.09% |
| 7 | MARSHALL WACE, LLP | 1.0M | $20.1M | -17.1% | 2.326% | 0.02% |
| 8 | AMERICAN CENTURY COMPANIES INC | 1.0M | $19.9M | +52.9% | 2.308% | 0.01% |
| 9 | GEODE CAPITAL MANAGEMENT, LLC | 977K | $19.1M | +10.1% | 2.215% | 0.00% |
| 10 | Boston Trust Walden Corp | 945K | $18.5M | -13.1% | 2.143% | 0.15% |
| 11 | Epoch Investment Partners, Inc. | 899K | $17.6M | -20.2% | 2.039% | 0.11% |
| 12 | VANGUARD PORTFOLIO MANAGEMENT LLC | 788K | $15.4M | — | 1.787% | 0.00% |
| 13 | D. E. Shaw & Co., Inc. | 666K | $13.0M | +19.5% | 1.509% | 0.01% |
| 14 | Invesco Ltd. | 605K | $11.8M | +20.6% | 1.372% | 0.00% |
| 15 | RENAISSANCE TECHNOLOGIES LLC | 554K | $10.9M | +1.7% | 1.256% | 0.02% |
| 16 | SYSTEMATIC FINANCIAL MANAGEMENT LP | 453K | $8.9M | +4.0% | 1.027% | 0.20% |
| 17 | MORGAN STANLEY | 420K | $8.2M | -28.9% | 0.953% | 0.00% |
| 18 | UBS Group AG | 420K | $8.2M | +63.8% | 0.953% | 0.00% |
| 19 | ROYCE & ASSOCIATES LP | 406K | $8.0M | +15.3% | 0.921% | 0.08% |
| 20 | NORTHERN TRUST CORP | 372K | $7.3M | +0.2% | 0.844% | 0.00% |
| 21 | MILLENNIUM MANAGEMENT LLC | 371K | $7.3M | +27.8% | 0.842% | 0.00% |
| 22 | Bridge City Capital, LLC | 335K | $6.6M | +42.3% | 0.760% | 1.82% |
| 23 | BRIDGEWAY CAPITAL MANAGEMENT, LLC | 330K | $6.5M | +2.1% | 0.749% | 0.13% |
| 24 | GOLDMAN SACHS GROUP INC | 329K | $6.5M | -40.8% | 0.747% | 0.00% |
| 25 | ARROWSTREET CAPITAL, LIMITED PARTNERSHIP | 325K | $6.4M | -41.9% | 0.738% | 0.00% |
denotes a marquee investor (Buffett, Burry, ARK, Tiger Global, Pershing Square, Baupost and other widely-followed managers). “% of Fund” shows how much of that investor’s total 13F portfolio is invested in AMPH — a direct measure of their conviction.
Filings activity in AMPH during Q1 2026, grouped by how each filer changed its position.
8 quarters of 13F filings · Δ columns show change vs prior quarter
| Quarter | Inst. Holders | Δ Holders | Ownership % | Δ Ownership | Total 13F Value | Δ Value |
|---|---|---|---|---|---|---|
| Q1 2026 | 208 | 11% | 67.82% | 30.88 pp | $601M | 31% |
| Q4 2025 | 234 | 1.3% | 98.70% | +3.55 pp | $874M | +3.7% |
| Q3 2025 | 237 | 1.3% | 95.15% | +13.38 pp | $843M | +16% |
| Q2 2025 | 240 | +2.1% | 81.77% | 21.61 pp | $724M | 21% |
| Q1 2025 | 235 | 10% | 103.38% | 39.01 pp | $916M | 27% |
| Q4 2024 | 262 | 3.3% | 142.39% | 41.41 pp | $1.26B | 23% |
| Q3 2024 | 271 | +3.4% | 183.80% | +35.29 pp | $1.63B | +24% |
| Q2 2024 | 262 | — | 148.51% | — | $1.32B | — |
Source: SEC 13F institutional filings. Ownership % requires market cap data and will show once linked. Δ columns compare to the immediately prior filed quarter.
Quick answers to the most common questions about buying AMPH stock.
Based on Q1 2026 13F filings, institutional ownership of Amphastar Pharmaceuticals, Inc. stands at 67.8%, held across 208 reporting institutions.
BlackRock, Inc. is the largest reported institutional holder of AMPH, with approximately 5,421,343 shares worth $0.11B as of Q1 2026.
Yes — 2 widely-followed marquee investors appear among the top 25 institutional holders of AMPH, including RENAISSANCE TECHNOLOGIES LLC, MILLENNIUM MANAGEMENT LLC.
Our composite Smart Money Score for AMPH is 32 out of 100 (Bearish). It combines net institutional buying activity, ownership shift, marquee investor presence, and holder-count growth.
30 institutions opened new positions in AMPH during Q1 2026, while 56 fully exited. 23 added to existing positions and 153 trimmed.
AMPH institutional ownership fell by 30.88 percentage points quarter-over-quarter, with a net change of -26 holders.
The top 10 institutions account for 57.1% of all reported 13F value in AMPH, and the top 25 account for 80.8%.
All data is sourced from SEC Form 13F filings, which institutional investment managers with at least $100M in assets are required to file each quarter. We process every 13F filing from EDGAR and recompute the aggregates after each cycle. Insider transactions are sourced from Form 4 filings.
Amphastar Pharmaceuticals, Inc. (AMPH) Institutional Ownership