EcoR1 Capital, LLC

Name: EcoR1 Capital, LLC 13F holdings, Q1 2026
Creator: EcoR1 Capital, LLC
Published: 2026-05-15

Q2 2026Q4 2025Q3 2025Q2 2025Q1 2025Q4 2024Q3 2024Q2 2024Q1 2024

In its 13F for Q1 2026 (holdings as of March 31, 2026, filed May 15, 2026), EcoR1 Capital, LLC reported 28 stock positions worth $2.3 billion. Its top holding was Zymeworks (ZYME) at 24.6% of the portfolio, followed by Anaptysbio (ANAB, 18.7%) and Jazz Pharmaceuticals (JAZZ, 13.8%). Compared with Q4 2025, it opened 10 new positions, sold out of 8, added to 4 and reduced 4. The biggest buy was Centessa Pharmaceuticals (CNTA, shares +93%) and the biggest sale an exit from Immunome (IMNM).

Most Recent 13F: Q2 2026
Location: San Francisco, CA
CIK: 0001587114
Portfolio Value: $2.3B (Q1 2026)
SEC Filing: 0000935836-26-000270 ↗ filed May 15, 2026

Holdings Value

Holdings 28 stocks · $2.3B


ZYME Zymeworks Inc.	24.58%	22,970,388	$575.2M	No change
ANAB Anaptysbio Inc.	18.68%	7,880,094	$437.0M	No change
JAZZ Jazz Pharmaceuticals PLC	13.79%	1,706,469	$322.6M	No change
CNTA Centessa Pharmaceuticals Ltd.	10.19%	6,000,000	$238.3M	Add +92.6%
CRNX Crinetics Pharmaceuticals Inc.	6.66%	4,288,120	$155.7M	No change
AKTS Aktis Oncology Inc.	3.69%	4,824,469	$86.3M	New
ORIC Oric Pharmaceuticals Inc.	3.64%	6,728,116	$85.2M	No change
CGON CG Oncology Inc.	3.19%	1,102,000	$74.6M	Add +42.8%
CRSP Crispr Therapeutics AG	2.82%	1,389,276	$66.1M	No change
ETON Eton Pharmaceuticals Inc.	2.29%	2,171,938	$53.6M	Add +7.0%
LKFT Lakefront Biotherapeutic-ADR filed as GALAPAGOS NV	2.14%	1,667,119	$50.0M	No change
XNCR Xencor Inc.	1.13%	2,183,000	$26.3M	Reduce -32.9%
NGNE Neurogene Inc.	1.10%	1,271,342	$25.6M	No change
BBOT Bridgebio Oncology Therapeut	1.08%	2,823,126	$25.3M	No change
MBX MBX Biosciences Inc.	0.99%	777,000	$23.2M	Reduce -63.4%
RLAY Relay Therapeutics Inc.	0.81%	1,904,762	$19.0M	New
ZBIO Zenas Biopharma Inc.	0.66%	789,500	$15.4M	No change
ERAS Erasca Inc.	0.62%	900,000	$14.6M	New
EIKN Eikon Therapeutics Inc.	0.33%	732,606	$7.8M	New
REPL Replimune Group Inc.	0.33%	1,000,000	$7.7M	New
ZURA Zura Bio Ltd.	0.30%	1,179,715	$7.0M	New
PHAT Phathom Pharmaceuticals Inc.	0.30%	625,000	$6.9M	New
MREO Mereo Biopharma Group PL-ADR	0.19%	13,368,855	$4.4M	Add +70.2%
STOK Stoke Therapeutics Inc.	0.14%	100,000	$3.3M	New
PRLD Prelude Therapeutics Inc.	0.14%	947,049	$3.2M	New
IBIO Ibio Inc.	0.13%	1,583,000	$3.0M	Reduce -28.9%
HLXC Helix Acquisition Corp. Class A	0.09%	200,000	$2.0M	New
ATRA Atara Biotherapeutics Inc.	0.02%	99,593	$471K	Reduce -82.6%

Options reported separately and not counted above: CNTA calls ($16.3M).

Other holdings (1): bonds, preferreds, convertibles and warrants · $129K (not counted above)

Security	Class	Shares / Principal	Value	Change
SRZNW Surrozen Inc.-CW25	*W EXP 08/01/203	4,444	$129K	No change

Total filed on the 13F, all lines: $2.3B.

Portfolio Sells Q4 2025 → Q1 2026


IMNM Immunome Inc.	Sold out	0.00%	−2.81
MBX MBX Biosciences Inc.	Reduce -63.4%	0.99%	−2.08
XNCR Xencor Inc.	Reduce -32.9%	1.13%	−1.16
GPCR Structure Therapeutics Inc.	Sold out	0.00%	−1.07
PCVX Vaxcyte Inc.	Sold out	0.00%	−0.95
AQST Aquestive Therapeutics Inc.	Sold out	0.00%	−0.78
VYGR Voyager Therapeutics Inc.	Sold out	0.00%	−0.72
ATRA Atara Biotherapeutics Inc.	Reduce -82.6%	0.02%	−0.46
MNKD Mannkind Corp.	Sold out	0.00%	−0.43
EOLS Evolus Inc.	Sold out	0.00%	−0.21
CAMP CAMP4 Therapeutics Corp.	Sold out	0.00%	−0.09
IBIO Ibio Inc.	Reduce -28.9%	0.13%	−0.07

Portfolio Buys Q4 2025 → Q1 2026


CNTA Centessa Pharmaceuticals Ltd.	Add +92.6%	10.19%	+6.61
AKTS Aktis Oncology Inc.	New	3.69%	+3.69
CGON CG Oncology Inc.	Add +42.8%	3.19%	+1.72
RLAY Relay Therapeutics Inc.	New	0.81%	+0.81
ETON Eton Pharmaceuticals Inc.	Add +7.0%	2.29%	+0.72
ERAS Erasca Inc.	New	0.62%	+0.62
EIKN Eikon Therapeutics Inc.	New	0.33%	+0.33
REPL Replimune Group Inc.	New	0.33%	+0.33
ZURA Zura Bio Ltd.	New	0.30%	+0.30
PHAT Phathom Pharmaceuticals Inc.	New	0.30%	+0.30
STOK Stoke Therapeutics Inc.	New	0.14%	+0.14
PRLD Prelude Therapeutics Inc.	New	0.14%	+0.14
HLXC Helix Acquisition Corp. Class A	New	0.09%	+0.09
MREO Mereo Biopharma Group PL-ADR	Add +70.2%	0.19%	+0.04

Options Activity Q4 2025 → Q1 2026


CNTA Centessa Pharmaceuticals Ltd.	call	New	410,800	$16.3M
CGON CG Oncology Inc.	call	Sold out	292,800	$12.2Mbefore exit
XNCR Xencor Inc.	call	Sold out	67,500	$1.0Mbefore exit

Calls and puts are listed by the shares they cover; their value is not part of the stock holdings above.

Notes & Other Activity Q4 2025 → Q1 2026


NUVB.WS Nuvation Bio Inc. -CW27	*W EXP 02/10/202	Sold out	963,333	$8.6Mbefore exit

Bonds, preferreds, convertibles and warrants; not part of the stock holdings or percentages above.

All Filings

Quarter	Positions	13F Reported Value	Top Holdings
Q2 2026	30	$2.0B	ZYME, ANAB, AKTS, CGON, ETON
Q1 2026	28	$2.3B	ZYME, ANAB, JAZZ, CNTA, CRNX
Q4 2025	26	$2.2B	ZYME, ANAB, JAZZ, CRNX, CNTA
Q3 2025	28	$2.1B	ZYME, ANAB, QURE, JAZZ, CRNX
Q2 2025	34	$1.7B	ZYME, APLS, JAZZ, ANAB, CRNX
Q1 2025	42	$1.7B	APLS, JAZZ, ZYME, ANAB, CRNX
Q4 2024	53	$2.5B	APLS, ZYME, CRNX, JAZZ, PRTA
Q3 2024	60	$2.9B	APLS, ANAB, CRNX, PRTA, JAZZ
Q2 2024	52	$3.3B	APLS, PRTA, SRPT, ANAB, CRNX
Q1 2024	54	$3.9B	APLS, PRTA, ARVN, SRPT, CRNX