EcoR1 Capital, LLC

Position in ATRA — Atara Biotherapeutics, Inc.

CIK 1587114 San Francisco, CA

Position in ATRA

as of Jun 30, 2026 · filed Aug 14, 2026 Compact

Position Value

$17,816,960

+$17,345,886 QoQ

Shares Held

1,552,000

+1458.3% QoQ

Ownership

15.5%

of shares outstanding

% of Portfolio

0.88%

of 13F equity value

Holder Rank

of 36 holders

Holding Since

Dec 2023

11 quarters on record

Voting authority Sole 100% Shared 0% None 0%

Healthcare · as of Jun 30, 2026

EcoR1 Capital, LLC holds $1,935,887,028 across 29 Biotechnology names. ATRA ranks #16 (0.9% of the industry book) .

#	Ticker	Company	Shares	Value (USD)
1	ZYME	Zymeworks Inc.	22,970,388	$600,445,942
2	ANAB	Anaptysbio, Inc	7,880,094	$531,906,345
3	AKTS	Aktis Oncology, Inc.	4,824,469	$155,492,635
4	CGON	CG Oncology, Inc.	1,494,300	$106,170,015
5	CRSP	CRISPR Therapeutics AG	1,389,276	$75,771,113
6	ORIC	Oric Pharmaceuticals, Inc.	6,728,116	$72,865,496
7	TRAX	First Tracks Biotherapeutics, Inc.	3,174,519	$63,871,322
8	LKFT	Lakefront Biotherapeutics NV	1,667,119	$49,980,227

12 filing rows on record

Report Date	Value (USD)	Shares	Change	Type	Discretion	Filed
2026-06-30	$17,816,960	1,552,000	+1458.3%	Shares	Sole	2026-08-14
2026-05-07	$15,411,360	1,552,000	—	Shares	Sole	2026-05-07
2026-03-31	$471,074	99,593	-82.6%	Shares	Sole	2026-05-15
2025-12-31	$10,368,880	573,183	0.0%	Shares	Sole	2026-02-17
2025-09-30	$8,213,712	573,183	0.0%	Shares	Sole	2025-11-14
2025-06-30	$4,424,972	573,183	0.0%	Shares	Sole	2025-08-14
2025-03-31	$3,404,707	573,183	+7.7%	Shares	Sole	2025-05-15
2024-12-31	$7,082,703	532,134	+13.5%	Shares	Sole	2025-02-14
2024-09-30	$3,812,465	468,938	+15.3%	Shares	Sole	2024-11-14
2024-06-30	$3,456,771	406,679	-96.0%	Shares	Sole	2024-08-14
2024-03-31	$7,055,927	10,167,043	+1.0%	Shares	Sole	2024-05-15
2023-12-31	$5,164,393	10,067,043	—	Shares	Sole	2024-02-14
No filing history on record for this holder in this stock.