Updated Jul 16, 2026 · Last SEC filing 2026-06-15
Atara Biotherapeutics, Inc. (ATRA) has filed 8 SEC Form 4 insider transactions in the last 90 days, with the most recent on 2026-06-15. 5 Form 8-K material event filings were reported by ATRA in the last 90 days. 3 Form 144 notices of proposed sale were filed for ATRA stock. InsiderAlpha tracks every ATRA SEC filing — Form 4, Form 144, and 8-K — in real time, including Rule 10b5-1 plan detection.
| SEC CIK | 0001604464 |
|---|
| Form 4 filings (90d) | 8 |
|---|---|
| Form 8-K filings (90d) | 5 |
| Form 144 notices (90d) | 3 |
| Latest Form 4 filing | 2026-06-15 |
| Date | Insider | Role | Transaction | Shares | Price | Value | Filing |
|---|---|---|---|---|---|---|---|
| Cherry Brian N | Insider | A — Grant or award | 24.0K | $0.00 | — | SEC | |
| HEIDEN WILLIAM K | Insider | A — Grant or award | 12.0K | $0.00 | — | SEC | |
| Fust Matthew K | Insider | A — Grant or award | 12.0K | $0.00 | — | SEC | |
| Ciongoli Gregory Austin | Insider | A — Grant or award | 12.0K | $0.00 | — | SEC | |
| Grant-Huerta Yanina | Chief Accounting Officer | S — Open-market sale | 2.4K | $9.13 | $22K | SEC | |
| Nguyen AnhCo | President and CEO | S — Open-market sale | 5.2K | $9.13 | $48K | SEC | |
| Panacea Innovation Ltd | Insider | S — Open-market sale | 313.4K | $10.10 | $3.17M | SEC | |
| EcoR1 Capital, LLC | 10% Owner | P — Open-market purchase | 507.4K | $9.35 | $4.74M | SEC | |
| Panacea Innovation Ltd | Insider | M — Option exercise | 259.2K | $0.00 | $26 | SEC | |
| Panacea Innovation Ltd | Insider | F — Tax withholding / forfeiture | 5 | $5.23 | $26 | SEC | |
| Grant-Huerta Yanina | Chief Accounting Officer | A — Grant or award | 20.3K | $0.00 | — | SEC | |
| Nguyen AnhCo | President and CEO | A — Grant or award | 81.1K | $0.00 | — | SEC | |
| Grant-Huerta Yanina | Chief Accounting Officer | S — Open-market sale | 24 | $5.08 | $122 | SEC | |
| Grant-Huerta Yanina | Chief Accounting Officer | S — Open-market sale | 377 | $5.08 | $2K | SEC | |
| Grant-Huerta Yanina | Chief Accounting Officer | S — Open-market sale | 1.6K | $5.08 | $8K | SEC |
All transactions sourced from SEC EDGAR Form 4 filings for Atara Biotherapeutics, Inc. (ATRA). Updated in real time as new filings are submitted to the SEC.
| Insider | Form 4 filings | Total transaction value |
|---|---|---|
| HEIDEN WILLIAM K | 1 | — |
| Fust Matthew K | 1 | — |
| Panacea Innovation Ltd | 1 | $3.17M |
| EcoR1 Capital, LLC | 1 | $4.74M |
| Grant-Huerta Yanina | 1 | $22K |
Form 144 must be filed before insiders sell restricted or control stock above SEC thresholds. A cluster of Form 144 notices often precedes a wave of insider distribution.
SEC Form 4 transactions are reported with a one-letter code indicating the type of transaction. Common codes you'll see in ATRA insider filings:
| P | Open-market purchase by the insider |
|---|---|
| S | Open-market sale by the insider |
| A | Grant, award, or other acquisition from the issuer |
| M | Exercise or conversion of derivative security (e.g. options) |
| F | Payment of exercise price or tax liability via share withholding |
| G | Bona-fide gift of securities |
| D | Disposition to the issuer (e.g. share buyback participation) |
| J | Other acquisition or disposition |
| X | Exercise of in-the-money or at-the-money derivative security |
| C | Conversion of derivative security |
| V | Transaction voluntarily reported earlier than required |
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