EcoR1 Capital, LLC

In its 13F for Q2 2025 (holdings as of June 30, 2025, filed August 14, 2025), EcoR1 Capital, LLC reported 34 stock positions worth $1.7 billion. Its top holding was Zymeworks (ZYME) at 17.1% of the portfolio, followed by Apellis Pharmaceuticals (APLS, 12.2%) and Jazz Pharmaceuticals (JAZZ, 10.7%). Compared with Q1 2025, it opened 6 new positions, sold out of 14, added to 5 and reduced 4. The biggest buy was a new position in Iteos Therapeutics (ITOS) and the biggest sale an exit from Prothena (PRTA).

Most Recent 13F
Q2 2026
Location
San Francisco, CA
CIK
0001587114
Portfolio Value
$1.7B (Q2 2025)
SEC Filing
0000935836-25-000506 ↗ filed Aug 14, 2025

Holdings Value

0$1.0B$2.0B$3.0B$4.0B Q1 2024: $3.9B Q1 2024 Q2 2024: $3.3B Q2 2024 Q3 2024: $2.9B Q3 2024 Q4 2024: $2.5B Q4 2024 Q1 2025: $1.7B Q1 2025 Q2 2025: $1.7B $1.7B Q2 2025 Q3 2025: $2.1B Q3 2025 Q4 2025: $2.2B Q4 2025 Q1 2026: $2.3B Q1 2026 Q2 2026: $2.0B Q2 2026

Holdings 34 stocks · $1.7B
ZYME Zymeworks Inc. 17.11% 22,970,388 $288.3M Add +33.1%
APLS Apellis Pharmaceuticals Inc. 12.22% 11,895,808 $205.9M No change
JAZZ Jazz Pharmaceuticals PLC 10.75% 1,706,469 $181.1M No change
ANAB Anaptysbio Inc. 10.38% 7,880,094 $174.9M No change
CRNX Crinetics Pharmaceuticals Inc. 7.32% 4,288,120 $123.3M No change
ITOS Iteos Therapeutics Inc. 6.32% 10,688,978 $106.6M New
CRSP Crispr Therapeutics AG 4.01% 1,389,276 $67.6M No change
QURE Uniqure NV 3.30% 3,988,971 $55.6M No change
TNGX Tango Therapeutics Inc. 3.23% 10,630,736 $54.4M No change
XNCR Xencor Inc. 2.87% 6,144,767 $48.3M No change
IMNM Immunome Inc. 2.25% 4,079,415 $37.9M No change
JANX Janux Therapeutics Inc. 2.02% 1,469,818 $34.0M No change
LKFT Lakefront Biotherapeutic-ADR filed as GALAPAGOS NV 1.72% 1,036,945 $29.0M Add +569.0%
ETON Eton Pharmaceuticals Inc. 1.72% 2,030,544 $28.9M Add +4.7%
KURA Kura Oncology Inc. 1.44% 4,200,000 $24.2M Add +59.1%
AKRO Akero Therapeutics Inc. 1.39% 440,000 $23.5M No change
MDGL Madrigal Pharmaceuticals Inc. 1.35% 75,000 $22.7M No change
NGNE Neurogene Inc. 1.13% 1,271,342 $19.0M No change
VRNA Verona Pharma Ltd. 1.12% 200,000 $18.9M New
TECX Tectonic Therapeutic Inc. 1.10% 935,121 $18.6M No change
ORIC Oric Pharmaceuticals Inc. 0.97% 1,618,068 $16.4M Reduce -52.7%
ALKS Alkermes PLC 0.85% 500,000 $14.3M New
RNAM Avidity Biosciences Inc. 0.84% 500,000 $14.2M Reduce -10.3%
MBX MBX Biosciences Inc. 0.78% 1,149,794 $13.1M Reduce -8.7%
VYGR Voyager Therapeutics Inc. 0.72% 3,917,546 $12.2M No change
PCRX Pacira Biosciences Inc. 0.65% 457,471 $10.9M New
REPL Replimune Group Inc. 0.47% 850,341 $7.9M No change
MTSR Metsera Inc. 0.46% 271,529 $7.7M Add +443.1%
ADAPY Adaptimmune Therapeutics-ADR 0.39% 27,404,070 $6.6M No change
DAWN Day One Biopharmaceuticals I 0.33% 862,068 $5.6M No change
HLVX Hillevax Inc. 0.29% 2,420,243 $4.8M New
ATRA Atara Biotherapeutics Inc. 0.26% 573,183 $4.4M No change
WHWK Whitehawk Therapeutics Inc. 0.12% 1,091,417 $2.0M Reduce -47.6%
MGNX Macrogenics Inc. 0.12% 1,602,717 $1.9M New

Options reported separately and not counted above: QURE calls ($1.9M).

Other holdings (2): bonds, preferreds, convertibles and warrants · $2.5M (not counted above)
SecurityClassShares / PrincipalValueChange
NUVB.WS Nuvation Bio Inc. -CW27 *W EXP 02/10/202 963,333$1.9MNo change
SRZNW Surrozen Inc.-CW25 *W EXP 08/01/203 66,665$596KNo change

Total filed on the 13F, all lines: $1.7B.

Portfolio Sells Q1 2025 → Q2 2025
PRTA Prothena Corp. PLC Sold out 0.00% −8.53
SRPT Sarepta Therapeutics Inc. Sold out 0.00% −4.91
BEAM Beam Therapeutics Inc. Sold out 0.00% −0.61
DNA Ginkgo Bioworks Holdings Inc. Sold out 0.00% −0.50
BCYC Bicycle Therapeutics PLC-ADR Sold out 0.00% −0.46
VERV Verve Therapeutics Inc. Sold out 0.00% −0.34
SLDB Solid Biosciences Inc. Sold out 0.00% −0.16
ORIC Oric Pharmaceuticals Inc. Reduce -52.7% 0.97% −0.16
RNAM Avidity Biosciences Inc. Reduce -10.3% 0.84% −0.14
KROS Keros Therapeutics Inc. Sold out 0.00% −0.11
RLAY Relay Therapeutics Inc. Sold out 0.00% −0.10
WHWK Whitehawk Therapeutics Inc. Reduce -47.6% 0.12% −0.10
KLRS Kalaris Therapeutics Inc. Sold out 0.00% −0.10
PRME Prime Medicine Inc. Sold out 0.00% −0.08
TCRX Tscan Therapeutics Inc. Sold out 0.00% −0.05
ALGS Aligos Therapeutics Inc. Sold out 0.00% −0.04
UPB Upstream Bio Inc. Sold out 0.00% −0.02
MBX MBX Biosciences Inc. Reduce -8.7% 0.78% +0.23

Portfolio Buys Q1 2025 → Q2 2025
ITOS Iteos Therapeutics Inc. New 6.32% +6.32
ZYME Zymeworks Inc. Add +33.1% 17.11% +4.88
LKFT Lakefront Biotherapeutic-ADR Add +569.0% 1.72% +1.49
VRNA Verona Pharma Ltd. New 1.12% +1.12
ALKS Alkermes PLC New 0.85% +0.85
PCRX Pacira Biosciences Inc. New 0.65% +0.65
KURA Kura Oncology Inc. Add +59.1% 1.44% +0.40
MTSR Metsera Inc. Add +443.1% 0.46% +0.38
HLVX Hillevax Inc. New 0.29% +0.29
ETON Eton Pharmaceuticals Inc. Add +4.7% 1.72% +0.22
MGNX Macrogenics Inc. New 0.12% +0.12

Options Activity Q1 2025 → Q2 2025
ETON Eton Pharmaceuticals Inc. call Sold out 50,500 $655Kbefore exit

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

All Filings

QuarterPositions13F Reported ValueTop Holdings
Q2 2026 30$2.0BZYME, ANAB, AKTS, CGON, ETON
Q1 2026 28$2.3BZYME, ANAB, JAZZ, CNTA, CRNX
Q4 2025 26$2.2BZYME, ANAB, JAZZ, CRNX, CNTA
Q3 2025 28$2.1BZYME, ANAB, QURE, JAZZ, CRNX
Q2 2025 34$1.7BZYME, APLS, JAZZ, ANAB, CRNX
Q1 2025 42$1.7BAPLS, JAZZ, ZYME, ANAB, CRNX
Q4 2024 53$2.5BAPLS, ZYME, CRNX, JAZZ, PRTA
Q3 2024 60$2.9BAPLS, ANAB, CRNX, PRTA, JAZZ
Q2 2024 52$3.3BAPLS, PRTA, SRPT, ANAB, CRNX
Q1 2024 54$3.9BAPLS, PRTA, ARVN, SRPT, CRNX