Atara Biotherapeutics, Inc. SEC filings ATRA
Atara Biotherapeutics, Inc. has 1,002 filings in SEC EDGAR's recent list, going back to Jul 9, 2015. Its latest annual report, Form 10-K, was filed on Mar 16, 2026 for the period ended Dec 31, 2025. The latest quarterly report (Form 10-Q) was filed on Aug 12, 2026, covering the quarter ended Jun 30, 2026. The most recent current report (Form 8-K) was filed on Aug 12, 2026 (results of operations). The company's fiscal year ends on December 31.
| Form | Description | Filed | Period |
|---|---|---|---|
| 4 | Insider transaction | Sep 4, 2026 | Sep 4, 2026 |
| 144 | Notice of proposed sale | Aug 26, 2026 | — |
| 4 | Insider transaction | Aug 26, 2026 | Aug 17, 2026 |
| SCHEDULE 13G/A | Amended ownership over 5% (passive) | Aug 14, 2026 | — |
| 10-Q | Quarterly report | Aug 12, 2026 | Jun 30, 2026 |
| 8-K |
Current report
Results of operations
|
Aug 12, 2026 | Aug 12, 2026 |
| 4 | Insider transaction | Jul 24, 2026 | Jul 22, 2026 |
| SCHEDULE 13D/A | Amended ownership over 5% (active) | Jul 24, 2026 | — |
| 3 | Initial insider ownership | Jul 6, 2026 | Jun 26, 2026 |
| 8-K |
Current report
Officer or director change
|
Jun 26, 2026 | Jun 22, 2026 |
| 4 | Insider transaction | Jun 15, 2026 | Jun 11, 2026 |
| 3 | Initial insider ownership | Jun 15, 2026 | Jun 11, 2026 |
| S-8 | Employee stock plan registration | Jun 12, 2026 | — |
| 8-K |
Current report
Officer or director change, Shareholder vote results
|
Jun 12, 2026 | Jun 9, 2026 |
| 4 | Insider transaction | Jun 11, 2026 | Jun 9, 2026 |
| 4 | Insider transaction | Jun 11, 2026 | Jun 9, 2026 |
| 4 | Insider transaction | Jun 11, 2026 | Jun 9, 2026 |
| 4 | Insider transaction | May 20, 2026 | May 18, 2026 |
| 4 | Insider transaction | May 20, 2026 | May 18, 2026 |
| 144 | Notice of proposed sale | May 18, 2026 | — |
| 144 | Notice of proposed sale | May 18, 2026 | — |
| SCHEDULE 13D/A | Amended ownership over 5% (active) | May 14, 2026 | — |
| SCHEDULE 13G | Ownership over 5% (passive) | May 13, 2026 | — |
| 424B5 | Prospectus supplement | May 12, 2026 | — |
| 10-Q | Quarterly report | May 12, 2026 | Mar 31, 2026 |
| 8-K | Current report | May 12, 2026 | May 12, 2026 |
| SCHEDULE 13D/A | Amended ownership over 5% (active) | May 11, 2026 | — |
| 4 | Insider transaction | May 11, 2026 | May 7, 2026 |
| 4 | Insider transaction | May 11, 2026 | May 7, 2026 |
| 3 | Initial insider ownership | May 11, 2026 | May 7, 2026 |
| SCHEDULE 13G | Ownership over 5% (passive) | May 8, 2026 | — |
| 144 | Notice of proposed sale | May 7, 2026 | — |
| SCHEDULE 13G/A | Amended ownership over 5% (passive) | May 7, 2026 | — |
| 8-K |
Current report
Other events
|
May 7, 2026 | May 7, 2026 |
| 8-K |
Current report
Listing notice
|
May 1, 2026 | Apr 30, 2026 |
| DEF 14A | Proxy statement | Apr 24, 2026 | Apr 24, 2026 |
| DEFA14A | Additional proxy material | Apr 24, 2026 | — |
| EFFECT | Filing | Mar 25, 2026 | — |
| 424B3 | Prospectus | Mar 25, 2026 | — |
| CORRESP | Letter to the SEC | Mar 23, 2026 | — |
| UPLOAD | Letter from the SEC | Mar 20, 2026 | — |
| 4 | Insider transaction | Mar 19, 2026 | Mar 17, 2026 |
| S-3 | Shelf registration | Mar 17, 2026 | — |
| 424B5 | Prospectus supplement | Mar 16, 2026 | — |
| 10-K | Annual report | Mar 16, 2026 | Dec 31, 2025 |
| 8-K |
Current report
Results of operations
|
Mar 16, 2026 | Mar 16, 2026 |
| 8-K |
Current report
Other events
|
Mar 12, 2026 | Mar 12, 2026 |
| 4 | Insider transaction | Mar 11, 2026 | Mar 9, 2026 |
| 4 | Insider transaction | Mar 11, 2026 | Mar 9, 2026 |
| 4 | Insider transaction | Mar 4, 2026 | Mar 2, 2026 |
| 4 | Insider transaction | Mar 4, 2026 | Mar 2, 2026 |
| 8-K |
Current report
Other events
|
Mar 3, 2026 | Mar 3, 2026 |
| 144 | Notice of proposed sale | Mar 2, 2026 | — |
| 144 | Notice of proposed sale | Mar 2, 2026 | — |
| 8-K |
Current report
Material agreement, Unregistered share sale, Other events
|
Feb 23, 2026 | Feb 20, 2026 |
| SCHEDULE 13D/A | Amended ownership over 5% (active) | Jan 14, 2026 | — |
| 4 | Insider transaction | Jan 14, 2026 | Jan 12, 2026 |
| 144 | Notice of proposed sale | Jan 12, 2026 | — |
| 8-K |
Current report
Results of operations, Other events
|
Jan 12, 2026 | Jan 12, 2026 |
| 8-K |
Current report
Material agreement
|
Jan 2, 2026 | Dec 30, 2025 |
| 4 | Insider transaction | Dec 1, 2025 | Nov 28, 2025 |
| 4 | Insider transaction | Nov 19, 2025 | Nov 17, 2025 |
| 4 | Insider transaction | Nov 19, 2025 | Nov 17, 2025 |
| 144 | Notice of proposed sale | Nov 17, 2025 | — |
| 144 | Notice of proposed sale | Nov 17, 2025 | — |
| SCHEDULE 13D/A | Amended ownership over 5% (active) | Nov 14, 2025 | — |
| SCHEDULE 13G/A | Amended ownership over 5% (passive) | Nov 14, 2025 | — |
| 10-Q | Quarterly report | Nov 12, 2025 | Sep 30, 2025 |
| 8-K |
Current report
Results of operations
|
Nov 12, 2025 | Nov 12, 2025 |
| 8-K |
Current report
Exit or restructuring costs
|
Oct 7, 2025 | Oct 6, 2025 |
| 8-K |
Current report
Officer or director change
|
Sep 4, 2025 | Sep 2, 2025 |
| 4 | Insider transaction | Aug 20, 2025 | Aug 18, 2025 |
| 4 | Insider transaction | Aug 20, 2025 | Aug 18, 2025 |
| 4 | Insider transaction | Aug 19, 2025 | Aug 15, 2025 |
| SCHEDULE 13D/A | Amended ownership over 5% (active) | Aug 19, 2025 | — |
| 144 | Notice of proposed sale | Aug 18, 2025 | — |
| 144 | Notice of proposed sale | Aug 18, 2025 | — |
| 10-Q | Quarterly report | Aug 11, 2025 | Jun 30, 2025 |
| 8-K |
Current report
Results of operations
|
Aug 11, 2025 | Aug 11, 2025 |
| 4 | Insider transaction | Jul 21, 2025 | Jul 17, 2025 |
| 8-K |
Current report
Results of operations, Other events
|
Jul 14, 2025 | Jul 14, 2025 |
| 4 | Insider transaction | Jun 12, 2025 | Jun 10, 2025 |
| 4 | Insider transaction | Jun 12, 2025 | Jun 10, 2025 |
| 4 | Insider transaction | Jun 12, 2025 | Jun 10, 2025 |
| 4 | Insider transaction | Jun 12, 2025 | Jun 10, 2025 |
| 4 | Insider transaction | Jun 12, 2025 | Jun 10, 2025 |
| 4 | Insider transaction | Jun 12, 2025 | Jun 10, 2025 |
| 8-K |
Current report
Shareholder vote results
|
Jun 11, 2025 | Jun 10, 2025 |
| SCHEDULE 13D | Ownership over 5% (active) | May 23, 2025 | — |
| 3 | Initial insider ownership | May 23, 2025 | May 16, 2025 |
| 3 | Initial insider ownership | May 23, 2025 | May 16, 2025 |
| 3 | Initial insider ownership | May 21, 2025 | May 16, 2025 |
| SCHEDULE 13D | Ownership over 5% (active) | May 21, 2025 | — |
| 4 | Insider transaction | May 20, 2025 | May 16, 2025 |
| 4 | Insider transaction | May 20, 2025 | May 16, 2025 |
| 144 | Notice of proposed sale | May 16, 2025 | — |
| 144 | Notice of proposed sale | May 16, 2025 | — |
| SCHEDULE 13D/A | Amended ownership over 5% (active) | May 16, 2025 | — |
| 4 | Insider transaction | May 16, 2025 | May 16, 2025 |
| 8-K |
Current report
Other events
|
May 16, 2025 | May 14, 2025 |
| SCHEDULE 13G/A | Amended ownership over 5% (passive) | May 15, 2025 | — |
| 424B5 | Prospectus supplement | May 15, 2025 | — |
| 10-Q | Quarterly report | May 15, 2025 | Mar 31, 2025 |
| 8-K |
Current report
Results of operations, Officer or director change
|
May 15, 2025 | May 14, 2025 |
| 8-K |
Current report
Exit or restructuring costs
|
May 12, 2025 | May 12, 2025 |
| 8-K |
Current report
Other events
|
May 6, 2025 | May 5, 2025 |
| DEFA14A | Additional proxy material | Apr 28, 2025 | — |
| DEF 14A | Proxy statement | Apr 28, 2025 | Jun 10, 2025 |
| 3 | Initial insider ownership | Apr 10, 2025 | Mar 31, 2025 |
| 8-K |
Current report
Material agreement
|
Apr 4, 2025 | Mar 31, 2025 |
| 4 | Insider transaction | Apr 2, 2025 | Mar 31, 2025 |
| 8-K |
Current report
Officer or director change
|
Mar 31, 2025 | Mar 25, 2025 |
| 10-K | Annual report | Mar 7, 2025 | Dec 31, 2024 |
| 8-K |
Current report
Results of operations
|
Mar 7, 2025 | Mar 7, 2025 |
| 4 | Insider transaction | Mar 5, 2025 | Mar 3, 2025 |
| 4 | Insider transaction | Mar 5, 2025 | Mar 3, 2025 |
| 4 | Insider transaction | Mar 5, 2025 | Mar 3, 2025 |
| 144 | Notice of proposed sale | Mar 3, 2025 | — |
| 144 | Notice of proposed sale | Mar 3, 2025 | — |
| 144 | Notice of proposed sale | Mar 3, 2025 | — |
| 8-K |
Current report
Exit or restructuring costs
|
Mar 3, 2025 | Mar 3, 2025 |
| SCHEDULE 13G | Ownership over 5% (passive) | Feb 6, 2025 | — |
| 4 | Insider transaction | Jan 29, 2025 | Jan 27, 2025 |
| 8-K |
Current report
Exit or restructuring costs
|
Jan 27, 2025 | Jan 27, 2025 |
| 8-K |
Current report
Other events
|
Jan 21, 2025 | Jan 21, 2025 |
| S-8 | Employee stock plan registration | Jan 17, 2025 | — |
| 8-K |
Current report
Results of operations, Other events
|
Jan 16, 2025 | Jan 16, 2025 |
| 8-K |
Current report
Bylaw or fiscal year change
|
Dec 23, 2024 | Dec 20, 2024 |
| 4 | Insider transaction | Nov 20, 2024 | Nov 18, 2024 |
| 4 | Insider transaction | Nov 20, 2024 | Nov 18, 2024 |
| 4 | Insider transaction | Nov 20, 2024 | Nov 18, 2024 |
| 144 | Notice of proposed sale | Nov 18, 2024 | — |
| 144 | Notice of proposed sale | Nov 18, 2024 | — |
| 144 | Notice of proposed sale | Nov 18, 2024 | — |
| 144 | Notice of proposed sale | Nov 18, 2024 | — |
| SC 13G/A | Amended ownership over 5% (passive) | Nov 14, 2024 | — |
| SC 13G/A | Amended ownership over 5% (passive) | Nov 14, 2024 | — |
| 10-Q | Quarterly report | Nov 12, 2024 | Sep 30, 2024 |
| 8-K |
Current report
Results of operations, Officer or director change
|
Nov 12, 2024 | Nov 8, 2024 |
| SC 13G/A | Amended ownership over 5% (passive) | Nov 12, 2024 | — |
| SC 13G/A | Amended ownership over 5% (passive) | Nov 4, 2024 | — |
| 8-K |
Current report
Officer or director change
|
Oct 15, 2024 | Oct 14, 2024 |
| SC 13G/A | Amended ownership over 5% (passive) | Sep 13, 2024 | — |
| 4 | Insider transaction | Sep 11, 2024 | Sep 9, 2024 |
| 3 | Initial insider ownership | Sep 5, 2024 | Sep 3, 2024 |
| SC 13D/A | Amended ownership over 5% (active) | Sep 5, 2024 | — |
| 424B5 | Prospectus supplement | Sep 4, 2024 | — |
| 8-K |
Current report
Officer or director change, Other events
|
Sep 3, 2024 | Sep 3, 2024 |
| 4 | Insider transaction | Aug 20, 2024 | Aug 16, 2024 |
| 4 | Insider transaction | Aug 20, 2024 | Aug 16, 2024 |
| 4 | Insider transaction | Aug 20, 2024 | Aug 16, 2024 |
| 4 | Insider transaction | Aug 20, 2024 | Aug 16, 2024 |
| 4 | Insider transaction | Aug 20, 2024 | Aug 16, 2024 |
| 144 | Notice of proposed sale | Aug 16, 2024 | — |
| 144 | Notice of proposed sale | Aug 16, 2024 | — |
| 144 | Notice of proposed sale | Aug 16, 2024 | — |
| 144 | Notice of proposed sale | Aug 16, 2024 | — |
| 144 | Notice of proposed sale | Aug 16, 2024 | — |
| 4 | Insider transaction | Aug 14, 2024 | Aug 12, 2024 |
| 10-Q | Quarterly report | Aug 12, 2024 | Jun 30, 2024 |
| 8-K |
Current report
Results of operations, Officer or director change
|
Aug 12, 2024 | Aug 10, 2024 |
| 8-K |
Current report
Other events
|
Jul 17, 2024 | Jul 17, 2024 |
| SC 13G/A | Amended ownership over 5% (passive) | Jul 8, 2024 | — |
| 8-K |
Current report
Change to shareholder rights, Bylaw or fiscal year change
|
Jun 20, 2024 | Jun 20, 2024 |
| 8-K |
Current report
Other events
|
Jun 17, 2024 | Jun 17, 2024 |
| S-8 | Employee stock plan registration | Jun 11, 2024 | — |
| S-8 | Employee stock plan registration | Jun 11, 2024 | — |
| 8-K |
Current report
Shareholder vote results
|
Jun 11, 2024 | Jun 10, 2024 |
| SC 13D | Ownership over 5% (active) | May 22, 2024 | — |
| 4 | Insider transaction | May 20, 2024 | May 16, 2024 |
| 4 | Insider transaction | May 20, 2024 | May 16, 2024 |
| 4 | Insider transaction | May 20, 2024 | May 16, 2024 |
| 4 | Insider transaction | May 20, 2024 | May 16, 2024 |
| 4 | Insider transaction | May 20, 2024 | May 16, 2024 |
| 144 | Notice of proposed sale | May 16, 2024 | — |
| 144 | Notice of proposed sale | May 16, 2024 | — |
| 144 | Notice of proposed sale | May 16, 2024 | — |
| 144 | Notice of proposed sale | May 16, 2024 | — |
| 144 | Notice of proposed sale | May 16, 2024 | — |
| 144 | Notice of proposed sale | May 16, 2024 | — |
| DEFR14A | Filing | May 10, 2024 | — |
| 10-Q | Quarterly report | May 9, 2024 | Mar 31, 2024 |
| 8-K |
Current report
Results of operations
|
May 9, 2024 | May 9, 2024 |
| DEFA14A | Additional proxy material | Apr 26, 2024 | — |
| DEF 14A | Proxy statement | Apr 26, 2024 | Jun 10, 2024 |
| PRE 14A | Preliminary proxy statement | Apr 12, 2024 | Jun 10, 2024 |
| 4 | Insider transaction | Apr 2, 2024 | Mar 31, 2024 |
| 4 | Insider transaction | Apr 2, 2024 | Mar 31, 2024 |
| 4 | Insider transaction | Apr 2, 2024 | Mar 31, 2024 |
| 4 | Insider transaction | Apr 2, 2024 | Mar 31, 2024 |
| 4 | Insider transaction | Apr 2, 2024 | Mar 31, 2024 |
| 8-K |
Current report
Officer or director change
|
Mar 29, 2024 | Mar 26, 2024 |
| 10-K | Annual report | Mar 28, 2024 | Dec 31, 2023 |
| 8-K |
Current report
Results of operations
|
Mar 28, 2024 | Mar 28, 2024 |
| SC 13G | Ownership over 5% (passive) | Mar 18, 2024 | — |
| 4 | Insider transaction | Mar 6, 2024 | Mar 4, 2024 |
| 4 | Insider transaction | Mar 6, 2024 | Mar 4, 2024 |
| 4 | Insider transaction | Mar 6, 2024 | Mar 4, 2024 |
| 4 | Insider transaction | Mar 6, 2024 | Mar 4, 2024 |
| 4 | Insider transaction | Mar 6, 2024 | Mar 4, 2024 |
Showing 200 filings, the most recent 200. Main filings leave out insider and ownership forms such as Form 4; choose a type above to see them. Each form opens on SEC.gov. Older filings are on SEC EDGAR.
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Company profile
- Industry
- Biological Products, (No Diagnostic Substances) (SIC 2836)
- Listed as
- ATRA (Nasdaq)
- Fiscal year ends
- December 31
- Incorporated in
- DE
- Headquarters
- Thousand Oaks, CA
- SEC filer status
- Non-accelerated filer, Smaller reporting company
- SEC CIK
- 1604464
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All 182 Biological Products, (No Diagnostic Substances) companies
Source: SEC EDGAR filings. This is company-reported data, not investment advice.