Atara Biotherapeutics, Inc. (ATRA) Ownership
ATRA ownership summary
as of October 17, 2026- Institutions
- 57.7% of shares outstanding
- Insiders
- 16.80% of shares outstanding
- Shares outstanding
- 10.0M
- Float
- 4.6M shares available to trade
- Short interest
- 4.38% 322K shares short
- Days to cover
- 6.91 short interest down 20.4% vs prior month
- Institutions 57.67%
- Insiders 16.80%
- Other investors 25.53%
ATRA top institutional holders
20 largest| # | Holder | % of shares | Shares | Value | Change | Reported |
|---|---|---|---|---|---|---|
| 1 | EcoR1 Capital, LLC | 15.46% | 1.6M | $14.2M | +1.5M (+1,458.3%) | June 30, 2026 |
| 2 | Adage Capital Partners Gp LLC | 8.47% | 850K | $7.8M | +150,000 (+21.4%) | June 30, 2026 |
| 3 | Point72 Asset Management, L.P. | 6.85% | 688K | $6.3M | +493,454 (+254.0%) | June 30, 2026 |
| 4 | Redmile Group, LLC | 4.40% | 442K | $4.1M | — | June 30, 2026 |
| 5 | Vanguard Capital Management, LLC | 2.46% | 247K | $2.3M | +29,185 (+13.4%) | June 30, 2026 |
| 6 | Mackenzie Investments | 2.32% | 233K | $2.1M | −80,371 (−25.6%) | June 30, 2026 |
| 7 | BlackRock Inc | 0.84% | 84K | $775,297 | +5,433 (+6.9%) | June 30, 2026 |
| 8 | Geode Capital Management, LLC | 0.75% | 75K | $689,675 | +8,982 (+13.6%) | June 30, 2026 |
| 9 | Staley Capital Advisers Inc | 0.50% | 50K | $459,000 | — | June 30, 2026 |
| 10 | Vanguard Fiduciary Trust Co | 0.43% | 43K | $395,070 | +9,415 (+28.0%) | June 30, 2026 |
| 11 | Acadian Asset Management LLC | 0.39% | 39K | $356,597 | −92,065 (−70.3%) | June 30, 2026 |
| 12 | Jane Street Group LLC | 0.30% | 30K | $278,567 | −3,525 (−10.4%) | June 30, 2026 |
| 13 | State Street Corp | 0.26% | 26K | $242,839 | — | June 30, 2026 |
| 14 | Northern Trust Corp | 0.17% | 17K | $152,305 | +4,251 (+34.4%) | June 30, 2026 |
| 15 | FMR Inc | 0.16% | 16K | $149,065 | — | June 30, 2026 |
| 16 | XTX Topco Ltd | 0.15% | 15K | $140,482 | +15,303 (0.0%) | June 30, 2026 |
| 17 | Bridgeway Capital Management, LLC | 0.14% | 14K | $128,520 | −18,691 (−57.2%) | June 30, 2026 |
| 18 | Millennium Management LLC | 0.13% | 13K | $116,402 | −35,009 (−73.4%) | June 30, 2026 |
| 19 | Citadel Advisors Llc | 0.10% | 10K | $93,260 | +10,159 (0.0%) | June 30, 2026 |
| 20 | Morgan Stanley - Brokerage Accounts | 0.09% | 9,178 | $84,254 | +9 (+0.1%) | June 30, 2026 |
Value at the latest close. Change = shares bought or sold in the latest quarterly filing (13F). In the top 20, 11 holders added 2.2M shares and 5 cut 230K.
ATRA top mutual fund and ETF holders
15 largest| # | Holder | % of shares | Shares | Value | Change | Reported |
|---|---|---|---|---|---|---|
| 1 | Vanguard MStar Total Stk Mkt Idx Invest | 1.58% | 159K | $1.5M | — | August 31, 2026 |
| 2 | Mackenzie GQE US Small Cap F8 | 0.57% | 58K | $528,676 | −9,395 (−14.0%) | July 31, 2026 |
| 3 | Fidelity Extended Market Index | 0.38% | 39K | $354,440 | +3,218 (+9.1%) | August 31, 2026 |
| 4 | iShares Micro-Cap ETF | 0.18% | 18K | $165,919 | −125 (−0.7%) | September 30, 2026 |
| 5 | Fidelity VIP Disciplined Small Cap Init | 0.16% | 16K | $149,065 | — | July 31, 2026 |
| 6 | EA Bridgeway Ultra-Small Company Mkt ETF | 0.14% | 14K | $126,757 | — | September 30, 2026 |
| 7 | Fidelity Total Market Index | 0.12% | 12K | $107,011 | +1,178 (+11.2%) | August 31, 2026 |
| 8 | Fidelity Series Total Market Index | 0.11% | 11K | $102,586 | — | August 31, 2026 |
| 9 | Vanguard MStar Inst Ttl StkMktIdxInstlPl | 0.03% | 2,844 | $26,108 | — | August 31, 2026 |
| 10 | Vanguard Balanced Index Inv | 0.03% | 2,799 | $25,695 | — | August 31, 2026 |
| 11 | Fidelity Nasdaq Composite Index | 0.02% | 1,934 | $17,754 | −2,678 (−58.1%) | August 31, 2026 |
| 12 | Schwab Total Stock Market Index | 0.02% | 1,643 | $15,083 | — | August 31, 2026 |
| 13 | Vanguard U.S. Eq Idx £ Acc | 0.01% | 1,456 | $13,366 | — | August 31, 2026 |
| 14 | 1290 VT Micro Cap K | 0.01% | 1,147 | $10,529 | — | August 31, 2026 |
| 15 | BSF Systematic US Eq Abs Ret A2 USD | 0.01% | 609 | $5,591 | +609 (0.0%) | December 31, 2025 |
Funds report holdings monthly or quarterly; dates differ by fund.
ATRA insider transactions
latest 8| Date | Name | Transaction | Price | Shares | Value |
|---|---|---|---|---|---|
| 2026-01-12 | Innovation Ltd Panacea | Sell | $6.07 | 80,554 | $488,963 |
| 2025-11-17 | Anhco Nguyen | Sell | $13.19 | 2,915 | $38,449 |
| 2025-11-17 | Yanina Grant-Huerta | Sell | $13.19 | 1,804 | $23,795 |
| 2025-11-17 | Yanina Grant-Huerta | Sell | $13.19 | 1,804 | $23,795 |
| 2025-08-15 | Innovation Ltd Panacea | Buy | $12.19 | 55,000 | $670,450 |
| 2025-07-17 | Innovation Ltd Panacea | Buy | $9.64 | 19,335 | $186,389 |
| 2025-05-16 | Anhco Nguyen | Sell | $6.76 | 3,276 | $22,146 |
| 2025-05-16 | Yanina Grant-Huerta | Sell | $6.76 | 2,218 | $14,994 |
Reported trades by company officers, directors and other filers (including disclosures by members of Congress where EODHD lists them). "—" where the filing gives no share count.
ATRA shares outstanding
Year-end shares outstanding, adjusted for splits.
Who owns ATRA
Institutional investors own 57.7% of Atara Biotherapeutics's shares and insiders 16.80%. The largest holder is EcoR1 Capital, LLC with 15.46% of the shares (1.6M), as of June 30, 2026. Among the top 20 institutions, 11 added shares and 5 reduced their stake in the latest filings. Short interest is 4.38% of the float, or 6.91 days of average trading volume. The share count rose 1,911.7% since 2014.
Related: ATRA analyst forecast, ATRA key metrics. See the ATRA stock overview for the latest quote and news.
ATRA ownership FAQ
Who owns the most Atara Biotherapeutics stock?
The largest shareholders of Atara Biotherapeutics are EcoR1 Capital, LLC (15.46%), Adage Capital Partners Gp LLC (8.47%), Point72 Asset Management, L.P. (6.85%), Redmile Group, LLC (4.40%), Vanguard Capital Management, LLC (2.46%).
What percentage of Atara Biotherapeutics is owned by institutions?
Institutions hold 57.7% of Atara Biotherapeutics's shares outstanding; insiders hold 16.80%.
Which funds own Atara Biotherapeutics?
The largest fund holders of Atara Biotherapeutics are Vanguard MStar Total Stk Mkt Idx Invest (1.58%), Mackenzie GQE US Small Cap F8 (0.57%), Fidelity Extended Market Index (0.38%), iShares Micro-Cap ETF (0.18%), Fidelity VIP Disciplined Small Cap Init (0.16%).
What is Atara Biotherapeutics's short interest?
322K shares of Atara Biotherapeutics were sold short, 4.38% of the float; at the average daily volume it would take 6.91 days to cover.
Are insiders buying or selling Atara Biotherapeutics?
Of the latest 8 reported insider transactions in Atara Biotherapeutics (since May 16, 2025), 2 were purchases and 6 were sales.
How many shares of Atara Biotherapeutics are outstanding?
Atara Biotherapeutics has 10.0M shares outstanding, of which 4.6M are in the public float.