EcoR1 Capital, LLC

San Francisco, CA · CIK 1587114 · 13F filing filed 2026-08-14

SEC-registered investment adviser since 2015 · limited liability company

Assets managed$3.4bn
Staff22 · 9 in investment roles
Main clients (by assets)Private funds 100%
Private funds3 (2 hedge) · $3.4bn gross assets
Form ADV · 2026-03-30SEC adviser record

Legal entityECOR1 CAPITAL, LLC (US)

$2.0bn reported value -13.8% vs Q1 2026

31positions

88.0%in top 10

9 new 3 added 4 reduced 7 sold out vs Q1 2026

Options: 2 call positions ($40.0m notional), 0 put positions (— notional) – listed below, not included above.

Holdings, Q2 2026

The small lines show how much was held over the last 4 quarters (adjusted for stock splits).

#	Security	Ticker	Shares	Value	% of portfolio	Change	Shares change
1	ZYMEWORKS INC COM ZYME	ZYME	22,970,388	$600.4m29.77%	29.77%	Unchanged
2	ANAPTYSBIO INC COM ANAB	ANAB	7,880,094	$531.9m26.37%	26.37%	Unchanged
3	AKTIS ONCOLOGY INC COM AKTS	AKTS	4,824,469	$155.5m7.71%	7.71%	Unchanged
4	CG ONCOLOGY INC COM CGON	CGON	1,494,300	$106.2m5.26%	5.26%	Added +392.3k	+392,300 35.6%
5	ETON PHARMACEUTICALS INC COM ETON	ETON	2,171,938	$78.6m3.90%	3.90%	Unchanged
6	CRISPR THERAPEUTICS AG NAMEN AKT CRSP	CRSP	1,389,276	$75.8m3.76%	3.76%	Unchanged
7	ORIC PHARMACEUTICALS INC COM ORIC	ORIC	6,728,116	$72.9m3.61%	3.61%	Unchanged
8	FIRST TRACKS BIOTHERAPEUTICS ORD SHS TRAX	TRAX	3,174,519	$63.9m3.17%	3.17%	New
9	GALAPAGOS NV SPON ADR LKFT	LKFT	1,667,119	$50.0m2.48%	2.48%	Unchanged
10	NEUROGENE INC COM NGNE	NGNE	1,271,342	$40.0m1.98%	1.98%	Unchanged
11	STOKE THERAPEUTICS INC COM STOK	STOK	735,000	$24.0m1.19%	1.19%	Added +635.0k	+635,000 635.0%
12	FULCRUM THERAPEUTICS INC COM FULC	FULC	6,549,866	$24.0m1.19%	1.19%	New
13	LEGEND BIOTECH CORP SPONSORED ADS LEGN	LEGN	800,000	$23.1m1.15%	1.15%	New
14	BRIDGEBIO ONCOLOGY THERAPEUT COM NEW BBOT	BBOT	2,823,126	$21.5m1.07%	1.07%	Unchanged
15	MBX BIOSCIENCES INC COM MBX	MBX	388,500	$21.4m1.06%	1.06%	Reduced -388.5k	-388,500 -50.0%
16	ZENAS BIOPHARMA INC COM ZBIO	ZBIO	789,500	$20.0m0.99%	0.99%	Unchanged
17	ATARA BIOTHERAPEUTICS INC COM NEW ATRA	ATRA	1,552,000	$17.8m0.88%	0.88%	Added +1.5m	+1,452,407 1458.3%
18	RELAY THERAPEUTICS INC COM RLAY	RLAY	697,948	$13.1m0.65%	0.65%	Reduced -1.2m	-1,206,814 -63.4%
19	AURA BIOSCIENCES INC COM AURA	AURA	1,666,667	$11.8m0.59%	0.59%	New
20	ODYSSEY THERAPEUTICS INC COMMON STOCK ODTX	ODTX	555,555	$10.4m0.52%	0.52%	New
21	EIKON THERAPEUTICS INC COM EIKN	EIKN	732,606	$9.6m0.47%	0.47%	Unchanged
22	PHARVARIS N V COM PHVS	PHVS	235,000	$8.1m0.40%	0.40%	New
23	ZURA BIO LTD CLASS A ORD SHS ZURA	ZURA	1,179,715	$7.0m0.35%	0.35%	Unchanged
24	PHATHOM PHARMACEUTICALS INC COM PHAT	PHAT	625,000	$6.8m0.34%	0.34%	Unchanged
25	NURIX THERAPEUTICS INC COM NRIX	NRIX	270,000	$6.6m0.32%	0.32%	New
26	ERASCA INC COM ERAS	ERAS	330,000	$6.0m0.30%	0.30%	Reduced -570.0k	-570,000 -63.3%
27	ELOXX PHARMACEUTICALS INC COM NEW ELOX	ELOX	400,000	$5.6m0.28%	0.28%	New
28	AARDVARK THERAPEUTICS INC COM AARD	AARD	396,194	$2.3m0.11%	0.11%	New
29	HELIX ACQUISITION CORP III USD CL A ORD SHS HLXC	HLXC	200,000	$2.1m0.11%	0.11%	Unchanged
30	MEREO BIOPHARMA GROUP PLC SPON ADS MREO	MREO	1,000,000	$317.7k0.02%	0.02%	Reduced -12.4m	-12,368,855 -92.5%
31	SURROZEN INC W EXP 08/01/203 W EXP 08/01/203		4,444	$115.3k0.01%	0.01%	Unchanged

Sold out since Q1 2026

Security	Ticker	Shares held before	Value then
JAZZ PHARMACEUTICALS PLC JAZZ	JAZZ	1,706,469	$322.6m1.7m shares
CENTESSA PHARMACEUTICALS PLC		6,000,000	$238.3m6.0m shares
CRINETICS PHARMACEUTICALS IN CRNX	CRNX	4,288,120	$155.7m4.3m shares
XENCOR INC XNCR	XNCR	2,183,000	$26.3m2.2m shares
REPLIMUNE GROUP INC REPL	REPL	1,000,000	$7.7m1.0m shares
PRELUDE THERAPEUTICS INC PRLD	PRLD	947,049	$3.2m947.0k shares
IBIO INC IBIO	IBIO	1,583,000	$3.0m1.6m shares

Options (notional value)

Underlying	Ticker	Type	Shares controlled	Notional	Change
CG ONCOLOGY INC CGON · Call	CGON	Call	561,500	$39.9m561.5k shares	New
AARDVARK THERAPEUTICS INC AARD · Call	AARD	Call	14,700	$84.7k14.7k shares	New

Stakes above 5%

Companies where this manager has reported owning more than 5% of a class of shares, on Schedule 13D (may seek influence) or 13G (passive): its latest filing for each, from 19 Dec 2024 on.

Company	Ticker	Stake	Change	Schedule	Last filed
ZYMEWORKS INC ZYME · 13D · filed 2025-11-19	ZYME	30.7%≈ $600.4m	no change	13D	2025-11-19
ITEOS THERAPEUTICS INC ITOS · 13D · filed 2025-05-16	ITOS	27.9%	+13.0 pts	13D	2025-05-16
ATARA BIOTHERAPEUTICS INC ATRA · 13G · filed 2026-05-07	ATRA	17.4%≈ $17.8m	+7.5 pts	13G	2026-05-07
GALAPAGOS NV LKFT · 13D · filed 2025-07-28	LKFT	13.2%	+1.4 pts	13D	2025-07-28
ELOXX PHARMACEUTICALS INC ELOX · 13G · filed 2026-06-16	ELOX	9.9%≈ $5.6m	new	13G	2026-06-16
NEUROGENE INC NGNE · 13G · filed 2025-11-14	NGNE	9.9%≈ $45.4m		13G	2025-11-14
FIRST TRACKS BIOTHERAPEUTICS TRAX · 13G · filed 2026-04-22	TRAX	9.1%≈ $63.9m	new	13G	2026-04-22
AKTIS ONCOLOGY INC AKTS · 13D · filed 2026-01-20	AKTS	9.1%≈ $156.7m	new	13D	2026-01-20
FULCRUM THERAPEUTICS INC FULC · 13G · filed 2026-06-25	FULC	9.0%≈ $22.0m	no change	13G	2026-06-25
ALLOVIR INC 13G · filed 2025-02-14		8.1%		13G	2025-02-14
ETON PHARMACEUTICALS INC ETON · 13G · filed 2025-02-14	ETON	7.7%≈ $71.7m		13G	2025-02-14
ORIC PHARMACEUTICALS INC ORIC · 13G · filed 2025-08-05	ORIC	6.9%≈ $72.9m	new	13G	2025-08-05
ALTO NEUROSCIENCE INC ANRO · 13G · filed 2026-07-20	ANRO	5.8%≈ $58.9m	new	13G	2026-07-20

Trades reported as a company insider since 1 Apr 2026

Owning 10% or more of a company, or having someone on its board, makes this manager an insider there: it reports its trades in that company's shares on Form 4 within two business days. Open-market and private purchases and sales only.

Date	Company	Ticker	Trade	Shares	Value	Their holding
2026-05-07	ATARA BIOTHERAPEUTICS INC 10% owner · See Note	ATRA	Bought	507,407	$4.7m507.4k shares	+49%