Ticker · CUSIP 03209R103
Holders (tracked)
8
Combined shares
1,836,589
Combined value
$49.18M
Last close
$22.88
Quarter
2025Q4
Price · 1Y$22.88-0.47 (-2.01%)H $30.81 · L $18.18 · Avg Vol 478K
Tracked holders · last 8 quarters
-2 vs previous quarter over the last 8.
Price is -14.6% vs the avg quarter-end implied price across tracked holders.
SEC event timeline
15 events
- Wellington Management exited2026-02-17−17,199 shares · 2025Q4Position
- AQR Capital Management added2026-02-17+5,507 shares · 2025Q4Position
- D.E. Shaw & Co. added2026-02-17+39,844 shares · 2025Q4Position
- Izzy Englander (Millennium Mgmt) trimmed2026-02-17−407,092 shares · 2025Q4Position
- T. Rowe Price trimmed2026-02-17−238,426 shares · 2025Q4Position
- Ken Griffin (Citadel Advisors) added2026-02-17+1,949 shares · 2025Q4Position
- Renaissance Technologies trimmed2026-02-12−42,200 shares · 2025Q4Position
- −12,916 shares · 2025Q3Position
- Two Sigma Investments added2025-11-14+18,548 shares · 2025Q3Position
- D.E. Shaw & Co. added2025-11-14+223,294 shares · 2025Q3Position
- T. Rowe Price added2025-11-14+1,934 shares · 2025Q3Position
- Wellington Management added2025-11-14+1,581 shares · 2025Q3Position
- AQR Capital Management trimmed2025-11-14−13,700 shares · 2025Q3Position
- Izzy Englander (Millennium Mgmt) added2025-11-14+78,781 shares · 2025Q3Position
- Renaissance Technologies added2025-11-13+10,400 shares · 2025Q3Position
Insider activity
No insider transactions in the last 30 days.
Follow-the-investor returns
If you'd copied each holder of AMPH…
Cost basis inferred from each manager's quarter-over-quarter position changes. Sorted by % return on the position they're still holding.
| Investor | First in | Cost basis | Return | Position value today |
|---|---|---|---|---|
| D.E. Shaw & Co. | 2016Q1 | $25.42 | -10.0% | $12.7M |
| Ken Griffin (Citadel Advisors) | 2016Q1 | $26.76 | -14.5% | $281K |
| Ken Griffin (Citadel Advisors) | 2016Q1 | $26.76 | -14.5% | $281K |
| Renaissance Technologies | 2016Q3 | $30.55 | -25.1% | $12.5M |
| AQR Capital Management | 2016Q1 | $31.29 | -26.9% | $1.5M |
| Izzy Englander (Millennium Mgmt) | 2016Q1 | $31.69 | -27.8% | $6.7M |
| T. Rowe Price | 2022Q2 | $33.94 | -32.6% | $842K |
| Two Sigma Investments | 2016Q1 | $38.77 | -41.0% | $2.3M |
Who moved on this name in 2025Q4
Position changes reported for the latest quarter, grouped by direction.
New positions0
—
Added to3
- D.E. Shaw & Co.+39,844$1.1M
- AQR Capital Management+5,507$147K
- Ken Griffin (Citadel Advisors)+1,949$52K
Trimmed3
- Izzy Englander (Millennium Mgmt)−407,092$10.9M
- Renaissance Technologies−42,200$1.1M
- T. Rowe Price−238,426$6K
Exited1
- Wellington Management−17,199$458K
Institutional ownership over time
Distinct super-investors holding this ticker · combined dollar value, by quarter.
| Quarter | Holders | Combined value |
|---|---|---|
| 2022Q1 | 9 | $286.0M |
| 2022Q2 | 12 | $277.5M |
| 2022Q3 | 8 | $246.0M |
| 2022Q4 | 9 | $240.8M |
| 2023Q1 | 11 | $309.2M |
| 2023Q2 | 11 | $444.9M |
| 2023Q3 | 13 | $365.6M |
| 2023Q4 | 10 | $474.3M |
| 2024Q1 | 10 | $358.9M |
| 2024Q2 | 11 | $339.4M |
| 2024Q3 | 12 | $83.0M |
| 2024Q4 | 10 | $65.5M |
| 2025Q1 | 11 | $66.4M |
| 2025Q2 | 11 | $52.1M |
| 2025Q3 | 10 | $66.9M |
| 2025Q4 | 8 | $49.2M |
Who owns AMPH
8 super-investors · 2025Q4
Tracked stake
1.84M
shares
Combined value
$49M
% of shares outstanding
—
shares-out unknown
Quarter action mix
Added4Trim3Held1
| # | Manager | Shares | Value |
|---|---|---|---|
| 1 | D.E. Shaw & Co. | 557.1K | $15M |
| 2 | Renaissance Technologies | 544.7K | $15M |
| 3 | Izzy Englander Millennium Mgmt | 290.7K | $8M |
| 4 | Ken Griffin Citadel Advisors | 228.7K | $6M |
| 5 | Two Sigma Investments | 98.7K | $3M |
| 6 | AQR Capital Management | 67.7K | $2M |
| 7 | T. Rowe Price | 36.8K | $986K |
| 8 | Ken Griffin Citadel Advisors | 12.3K | $329K |
Recent moves
20 transactions
- +5,507 · 2025Q4
- −17,199 · 2025Q4
- −407,092 · 2025Q4
- TRIMT. Rowe Price−238,426 · 2025Q4
- +39,844 · 2025Q4
- +1,949 · 2025Q4
- −42,200 · 2025Q4
- −12,916 · 2025Q3
- +18,548 · 2025Q3
- +223,294 · 2025Q3
- +78,781 · 2025Q3
- +1,581 · 2025Q3
- +1,934 · 2025Q3
- −13,700 · 2025Q3
- +10,400 · 2025Q3
- +264,740 · 2025Q2
- −249,567 · 2025Q2
- +4,802 · 2025Q2
- TRIMT. Rowe Price−267,933 · 2025Q2
- −1,295 · 2025Q2
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- AMPH insider tradingEvery Form 4 filing by AMPH officers, directors, and 10%+ holders.
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