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ISSUER PROFILE · CIK 0001604464 · CUSIP 046513206

Atara Biotherapeutics, Inc.ATRA

3 13D/G filings 2 distinct filers 6 insider transactions (365d)

Post-Filing Returns · across 2 activist filings on this issuer

Median 30d
+1.6%
avg +1.6%
Median 60d
-1.0%
avg -1.0%
Median 90d
—
avg —
Median 180d
—
avg —

Returns measured from each activist filing's date_of_event, split + dividend adjusted via Yahoo Finance.

Cross-Reference Snapshot

Activist filings
3
3 SCHEDULE 13D/A
Distinct filers
2
multi-activist cluster
Insiders (365d)
6
0 buys · 1 sales
Latest short DTC
8.11
as of 2026-09-30

Institutional Consensus · 2025-12-31

Held by elite portfolio managers
1 holder · $331K
Point72 Asset Mgmt

13D/G Filings Timeline · 3 total

FiledFormFilerStakeSharesIntent
2026-07-24 SCHEDULE 13D/A Redmile Group, LLC 9.90% 950,994 view →
2026-05-14 SCHEDULE 13D/A Redmile Group, LLC 9.90% 950,994 view →
2026-05-11 SCHEDULE 13D/A Panacea Innovation Ltd — 1,318,894 view →

Form 4 Insider Transactions · last 365d

DateInsiderRoleTypeSharesPriceValue
2026-08-17 Nguyen AnhCo director, officer Sale 5,062 $8.08 $41K
2026-07-22 Redmile Group, LLC director Option exercise 195,211 — —
2026-07-22 Redmile Group, LLC director F 60 — —
2026-07-22 Redmile Group, LLC director Option exercise 101,089 $0.00 $253
2026-07-22 Redmile Group, LLC director Option exercise 38,735 $0.00 $97
2026-07-22 Redmile Group, LLC director Option exercise 55,387 $0.00 $138

FINRA Short Interest History

SettlementShort InterestDays to Cover% Δ vs prior
2026-09-30 321,792 8.11 -20.4%
2026-09-15 404,270 7.34 -5.4%
2026-08-31 427,435 11.07 -10.4%
2026-08-14 477,268 9.21 -11.1%
2026-07-31 536,897 9.39 -7.0%
2026-07-15 577,635 6.24 +59.8%
2026-06-30 361,520 3.95 -26.6%
2026-06-15 492,405 6.27 +1.6%
2026-05-29 484,391 2.91 -11.4%
2026-05-15 546,470 1.00 +78.5%
2026-04-30 306,093 6.10 -3.7%
2026-04-15 317,953 4.10 -2.8%

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