🕵️ Atara Biotherapeutics, Inc. ($ATRA)
SEC insider & ownership activity, last 12 months · CIK 1604464 · every row links its SEC filing
Insider buy and sell values were withheld pending verification over the last 12 months. 1 planned sale is pending, the largest $42K (Nguyen AnhCo). One red-flag 8-K in the window: Delisting notice (3.01), Apr 30, 2026.
Insider flow
2 buyers, value withheld pending verification (2 lots) · 3 sellers, value withheld pending verification (18 lots)
| Insider | Buys | Bought | Sells | Sold | Last |
|---|---|---|---|---|---|
| Nguyen Anhco | 0 | – | 8 | value withheld pending verification | Aug 17, 2026 |
| Grant-Huerta Yanina | 0 | – | 8 | value withheld pending verification | May 18, 2026 |
| Brian N. Cherry | 1 | value withheld pending verification | 0 | – | Sep 4, 2026 |
| Panacea Innovation Ltd | 0 | – | 2 | value withheld pending verification | May 7, 2026 |
| ECOR1 Capital, LLC | 1 | value withheld pending verification | 0 | – | May 7, 2026 |
5%+ holders
| Holder | Stake | Class | Schedule | Event | |
|---|---|---|---|---|---|
| Gregory A. Ciongoli | 20.0% | 13D | May 14, 2025 | filing ↗ | |
| Adiumentum Capital Fund I LP | 20.0% | 13D | May 14, 2025 | filing ↗ | |
| Adiumentum Capital Fund I GP LLC | 20.0% | 13D | May 14, 2025 | filing ↗ | |
| ECOR1 Capital, LLC | 17.4% | 13G | May 7, 2026 | filing ↗ | |
| Oleg Nodelman | 17.4% | 13G | May 7, 2026 | filing ↗ | |
| ECOR1 Capital Fund Qualified, L.P. | 16.2% | 13G | May 7, 2026 | filing ↗ | |
| James Huang | 16.1% | 13D | May 7, 2026 | filing ↗ | |
| Panacea Innovation Limited | 16.1% | 13D | May 7, 2026 | filing ↗ | |
| Panacea Venture Healthcare Fund II GP Company, Ltd. | 12.4% | 13D | May 7, 2026 | filing ↗ | |
| Panacea Venture Healthcare Fund II, L.P. | 12.4% | 13D | May 7, 2026 | filing ↗ | |
| Redmile Group, LLC | 9.9% | 13D | Jul 22, 2026 | filing ↗ | |
| Green Jeremy | 9.9% | 13D | Jul 22, 2026 | filing ↗ | |
| Adage Capital Management, L.P. | 8.6% | 13G | May 13, 2026 | filing ↗ | |
| Robert Atchinson | 8.6% | 13G | May 13, 2026 | filing ↗ | |
| Phillip Gross | 8.6% | 13G | May 13, 2026 | filing ↗ | |
| POINT72 Asset Management, L.P. | 7.6% | 13G | Aug 14, 2026 | filing ↗ | |
| POINT72 Capital Advisors, Inc. | 7.6% | 13G | Aug 14, 2026 | filing ↗ | |
| Steven A. Cohen | 7.6% | 13G | Aug 14, 2026 | filing ↗ | |
| Redmile Biopharma Investments II, L.P. | 6.6% | 13D | Jul 22, 2026 | filing ↗ |
Planned insider sales (Form 144)
| Seller | Planned | Approx. sale date | |
|---|---|---|---|
| Nguyen AnhCo | $42K | Aug 17, 2026 | filing ↗ |
| Nguyen AnhCo | $63K | May 18, 2026 | filing ↗ |
| Grant-Huerta Yanina | $29K | May 18, 2026 | filing ↗ |
| Panacea Innovation Ltd | $3.2M | May 7, 2026 | filing ↗ |
| Nguyen AnhCo | $18K | Mar 2, 2026 | filing ↗ |
| Grant-Huerta Yanina | $13K | Mar 2, 2026 | filing ↗ |
| Panacea Innovation Ltd | $235K | Jan 12, 2026 | filing ↗ |
| Panacea Innovation Ltd | $118K | Jan 12, 2026 | filing ↗ |
| Panacea Innovation Ltd | $121K | Jan 12, 2026 | filing ↗ |
| Nguyen AnhCo | $46K | Nov 17, 2025 | filing ↗ |
| Grant-Huerta Yanina | $28K | Nov 17, 2025 | filing ↗ |
Material events (8-K)
| Item | Event date | |
|---|---|---|
| Earnings (2.02) | Aug 12, 2026 | filing ↗ |
| Officer/director changes (5.02) | Jun 22, 2026 | filing ↗ |
| Officer/director changes (5.02) | Jun 9, 2026 | filing ↗ |
| Shareholder vote (5.07) | Jun 9, 2026 | filing ↗ |
| Financial Statements and Exhibits (9.01) | May 12, 2026 | filing ↗ |
| Other events (8.01) | May 7, 2026 | filing ↗ |
| Delisting notice (3.01) | Apr 30, 2026 | filing ↗ |
| Earnings (2.02) | Mar 16, 2026 | filing ↗ |
| Financial Statements and Exhibits (9.01) | Mar 16, 2026 | filing ↗ |
| Other events (8.01) | Mar 12, 2026 | filing ↗ |
| Financial Statements and Exhibits (9.01) | Mar 12, 2026 | filing ↗ |
| Other events (8.01) | Mar 3, 2026 | filing ↗ |
| Financial Statements and Exhibits (9.01) | Mar 3, 2026 | filing ↗ |
| Material agreement (1.01) | Feb 20, 2026 | filing ↗ |
| Unregistered equity sale (3.02) | Feb 20, 2026 | filing ↗ |
| Other events (8.01) | Feb 20, 2026 | filing ↗ |
| Financial Statements and Exhibits (9.01) | Feb 20, 2026 | filing ↗ |
| Earnings (2.02) | Jan 12, 2026 | filing ↗ |
| Other events (8.01) | Jan 12, 2026 | filing ↗ |
| Financial Statements and Exhibits (9.01) | Jan 12, 2026 | filing ↗ |
| Material agreement (1.01) | Dec 30, 2025 | filing ↗ |
| Financial Statements and Exhibits (9.01) | Dec 30, 2025 | filing ↗ |
| Earnings (2.02) | Nov 12, 2025 | filing ↗ |
| Financial Statements and Exhibits (9.01) | Nov 12, 2025 | filing ↗ |
| Exit or disposal costs (2.05) | Oct 6, 2025 | filing ↗ |