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ISSUER PROFILE · CIK 0001604464 · CUSIP 046513206

Atara Biotherapeutics, Inc.ATRA

3 13D/G filings 2 distinct filers 5 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)
5
0 buys · 0 sales
Latest short DTC
9.39
as of 2026-07-31

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
2026-07-22 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
2026-07-31 536,897 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%
2026-03-31 327,066 3.01 +4.4%
2026-03-13 313,290 1.00 -5.2%
2026-02-27 330,524 2.13 +57.9%
2026-02-13 209,287 2.40 -25.9%

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