Atara Biotherapeutics, Inc. (ATRA)
Nasdaq: ATRA · Biological Products, (No Diagnostic Substances) · Thousand Oaks, CA · filing with the SEC since 2014
Who owns Atara Biotherapeutics, Inc.
As filed with the SECHolders of 5% or more
6
Adiumentum Capital Fund I LP holds 20% of Common Stock, par value $0.0001 per share, as its SCHEDULE 13D/A filed May 16, 2025 says.
Directors and officers
10
report now, of 40 people on the record since 2014. Their holdings as a group are not read here.
Institutions as a whole
n/a
The record does not read the share held by managers that file Form 13F, so none is printed and no split of the rest is estimated. What it holds is the 6 named at left.
Holders of 5% or moreshare of the class, as filed
Adiumentum Capital Fund I LP
SCHEDULE 13D/A · filed May 16, 2025 · Common Stock, par value $0.0001 per share
EcoR1 Capital, LLC
SCHEDULE 13G/A · filed May 7, 2026 · Common Stock · 9.9% in Nov 14, 2025
Panacea Innovation Limited
SCHEDULE 13D/A · filed May 11, 2026 · Common Stock · 20% in Jan 14, 2026
Redmile Group, LLC
SCHEDULE 13D/A · filed Jul 24, 2026 · Common Stock, par value $0.0001 per share · 9.9% in May 14, 2026
Adage Capital Management, L.P.
SCHEDULE 13G · filed May 13, 2026 · Common Stock, par value $0.0001 per share
Point72 Asset Management, L.P.
SCHEDULE 13G/A · filed Aug 14, 2026 · Common Stock, par value $0.0001 per share · 6.2% in May 8, 2026
What ATRA reports owning in othersstakes of 5% or more, and other ties
1 subsidiary in 1 country, from the list filed with the 10-K filed Mar 16, 2026.
Insider tradesForm 4
17sales
1purchases
0sales on a scheduled plan
3people selling
$700,000sold, in dollars
$1.0Mbought, in dollars
Open-market trades on Form 4 from Sep 30, 2025 to Sep 30, 2026. A scheduled plan is a selling program set in advance under SEC rule 10b5-1. The trades are listed as filed and do not feed the grade.
By calendar yearSoldBought
2026 runs to Sep 30, 2026. Dollars as filed, summed by the transaction date.
People who traded in the window6 of 42 on the roster
| Person | Role as filed | Sales | Sold | On a plan | Buys | Bought |
|---|---|---|---|---|---|---|
| Panacea Innovation Ltd | 10% owner | 1 | $3.2M | 0 | 0 | $0 |
| Huang James | director | 1 | $500,000 | 0 | 0 | $0 |
| Nguyen Anhco | President and CEO | 8 | $100,000 | 0 | 0 | $0 |
| Grant-Huerta Yanina | Chief Accounting Officer | 8 | $100,000 | 0 | 0 | $0 |
| Cherry Brian N | director | 0 | $0 | 0 | 1 | $1.0M |
| Ecor1 Capital, LLC | 10% owner | 0 | $0 | 0 | 1 | $4.7M |