Atara Biotherapeutics, Inc.
ATRA- Exchange
- Nasdaq
- Industry
- Biological Products, (No Diagnostic Substances)
- SEC CIK
- 0001604464
In the last 90 days, Atara Biotherapeutics, Inc. insiders filed 1 open-market purchase and 1 sale; 36 institutions reported holding it in 13F filings for Q2 2026, worth $51.3M in total; no superinvestor holds it.
Holders of 5% or more of ATRA
Holders whose latest Schedule 13D or 13G filing reports 5% or more of Atara Biotherapeutics, Inc., largest stake first. The change is against the holder's previous filing.
| Holder | Latest form | Stake | Change | First filed | Latest filing | Filing |
|---|---|---|---|---|---|---|
| Panacea Innovation Ltd | 13D/A | 20.00%1.71M shares | +0.01 ppfrom 19.99% | May 21, 20252 filings | Aug 19, 2025 | SEC |
| Adiumentum Capital Fund I LP | 13D/A | 19.99%1.37M shares | – | May 16, 20251 filing | May 16, 2025 | SEC |
| Redmile Group, LLC | 13D/A | 9.90%751.2K shares | 0.00 ppfrom 9.90% | May 15, 20253 filings | Nov 14, 2025 | SEC |
| EcoR1 Capital, LLC | 13G/A | 9.90%715.9K shares | – | Nov 14, 20251 filing | Nov 14, 2025 | SEC |
| Panacea Innovation Ltd | 13G | 9.50%550.0K shares | New | Feb 6, 20251 filing | Feb 6, 2025 | SEC |
Stakes are as of each holder's latest filing. Holders whose last filing was in the old format (before December 18, 2024) have no stake on record and are not listed, and after an acquisition or delisting holders usually stop filing.
13D and 13G filings
8 Schedule 13D and 13G filings on Atara Biotherapeutics, Inc., newest first, including old-format filings without a stake.
| Filed (ET) | Filer | Form | Stake | Change | Event date | Filing |
|---|---|---|---|---|---|---|
| Nov 14, 20254:19 PM ET | Redmile Group, LLCand 4 others | 13D/A | 9.90%751.2K shares | 0.00 ppfrom 9.90% | Nov 12, 2025 | SEC |
| Nov 14, 20254:05 PM ET | EcoR1 Capital, LLCand 2 others | 13G/A | 9.90%715.9K shares | – | Sep 30, 2025 | SEC |
| Aug 19, 20258:15 PM ET | Panacea Innovation Ltdand 5 others | 13D/A | 20.00%1.71M shares | +0.01 ppfrom 19.99% | Aug 15, 2025 | SEC |
| May 23, 20254:05 PM ET | Redmile Group, LLCand 3 others | 13D | 9.90%705.2K shares | 0.00 ppfrom 9.90% | May 16, 2025 | SEC |
| May 21, 20256:00 PM ET | Panacea Innovation Ltdand 5 others | 13D | 19.99%1.64M shares | New | May 16, 2025 | SEC |
| May 16, 20256:28 PM ET | Adiumentum Capital Fund I LPand 2 others | 13D/A | 19.99%1.37M shares | – | May 14, 2025 | SEC |
| May 15, 20259:00 PM ET | Redmile Group, LLCand 3 others | 13G/A | 9.90%601.2K shares | – | Mar 31, 2025 | SEC |
| Feb 6, 20256:34 PM ET | Panacea Innovation Ltdand 3 others | 13G | 9.50%550.0K shares | New | Jan 30, 2025 | SEC |
Form 144: proposed insider sales
Notices from officers, directors and other affiliates planning to sell Atara Biotherapeutics, Inc. shares.
No Form 144 notices for Atara Biotherapeutics, Inc. are on file.