EcoR1 Capital, LLC

In its 13F for Q2 2026 (holdings as of June 30, 2026, filed August 14, 2026), EcoR1 Capital, LLC reported 30 stock positions worth $2.0 billion. Its top holding was Zymeworks (ZYME) at 29.8% of the portfolio, followed by Anaptysbio (ANAB, 26.4%) and Aktis Oncology (AKTS, 7.7%). Compared with Q1 2026, it opened 9 new positions, sold out of 7, added to 3 and reduced 4. The biggest buy was a new position in First Tracks Biotherapeutics (TRAX) and the biggest sale an exit from Jazz Pharmaceuticals (JAZZ).

Most Recent 13F
Q2 2026
Location
San Francisco, CA
CIK
0001587114
Portfolio Value
$2.0B (Q2 2026)
SEC Filing
0000935836-26-000415 ↗ filed Aug 14, 2026

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 Q2 2025 Q3 2025: $2.1B Q3 2025 Q4 2025: $2.2B Q4 2025 Q1 2026: $2.3B Q1 2026 Q2 2026: $2.0B $2.0B Q2 2026

Holdings 30 stocks · $2.0B
ZYME Zymeworks Inc. 29.77% 22,970,388 $600.4M No change
ANAB Anaptysbio Inc. 26.38% 7,880,094 $531.9M No change
AKTS Aktis Oncology Inc. 7.71% 4,824,469 $155.5M No change
CGON CG Oncology Inc. 5.26% 1,494,300 $106.2M Add +35.6%
ETON Eton Pharmaceuticals Inc. 3.90% 2,171,938 $78.6M No change
CRSP Crispr Therapeutics AG 3.76% 1,389,276 $75.8M No change
ORIC Oric Pharmaceuticals Inc. 3.61% 6,728,116 $72.9M No change
TRAX First Tracks Biotherapeutics 3.17% 3,174,519 $63.9M New
LKFT Lakefront Biotherapeutic-ADR 2.48% 1,667,119 $50.0M No change
NGNE Neurogene Inc. 1.98% 1,271,342 $40.0M No change
STOK Stoke Therapeutics Inc. 1.19% 735,000 $24.0M Add +635.0%
FULC Fulcrum Therapeutics Inc. 1.19% 6,549,866 $24.0M New
LEGN Legend Biotech Corp.-ADR 1.15% 800,000 $23.1M New
BBOT Bridgebio Oncology Therapeut 1.07% 2,823,126 $21.5M No change
MBX MBX Biosciences Inc. 1.06% 388,500 $21.4M Reduce -50.0%
ZBIO Zenas Biopharma Inc. 0.99% 789,500 $20.0M No change
ATRA Atara Biotherapeutics Inc. 0.88% 1,552,000 $17.8M Add +1458.3%
RLAY Relay Therapeutics Inc. 0.65% 697,948 $13.1M Reduce -63.4%
AURA Aura Biosciences Inc. 0.59% 1,666,667 $11.8M New
ODTX Odyssey Therapeutics Inc. 0.52% 555,555 $10.4M New
EIKN Eikon Therapeutics Inc. 0.47% 732,606 $9.6M No change
PHVS Pharvaris NV 0.40% 235,000 $8.1M New
ZURA Zura Bio Ltd. 0.35% 1,179,715 $7.0M No change
PHAT Phathom Pharmaceuticals Inc. 0.34% 625,000 $6.8M No change
NRIX Nurix Therapeutics Inc. 0.32% 270,000 $6.6M New
ERAS Erasca Inc. 0.30% 330,000 $6.0M Reduce -63.3%
ELOX Eloxx Pharmaceuticals Inc. 0.28% 400,000 $5.6M New
AARD Aardvark Therapeutics Inc. 0.11% 396,194 $2.3M New
HLXC Helix Acquisition Corp. Class A 0.11% 200,000 $2.1M No change
MREO Mereo Biopharma Group PL-ADR 0.02% 1,000,000 $318K Reduce -92.5%

Options reported separately and not counted above: CGON calls ($39.9M), AARD calls ($85K).

Other holdings (1): bonds, preferreds, convertibles and warrants · $115K (not counted above)
SecurityClassShares / PrincipalValueChange
SRZNW Surrozen Inc.-CW25 *W EXP 08/01/203 4,444$115KNo change

Total filed on the 13F, all lines: $2.0B.

Portfolio Sells Q1 2026 → Q2 2026
JAZZ Jazz Pharmaceuticals PLC Sold out 0.00% −13.79
CNTA Centessa Pharmaceuticals Ltd. Sold out 0.00% −10.19
CRNX Crinetics Pharmaceuticals Inc. Sold out 0.00% −6.66
XNCR Xencor Inc. Sold out 0.00% −1.13
REPL Replimune Group Inc. Sold out 0.00% −0.33
ERAS Erasca Inc. Reduce -63.3% 0.30% −0.32
MREO Mereo Biopharma Group PL-ADR Reduce -92.5% 0.02% −0.17
RLAY Relay Therapeutics Inc. Reduce -63.4% 0.65% −0.16
PRLD Prelude Therapeutics Inc. Sold out 0.00% −0.14
IBIO Ibio Inc. Sold out 0.00% −0.13
MBX MBX Biosciences Inc. Reduce -50.0% 1.06% +0.07

Portfolio Buys Q1 2026 → Q2 2026
TRAX First Tracks Biotherapeutics New 3.17% +3.17
CGON CG Oncology Inc. Add +35.6% 5.26% +2.08
FULC Fulcrum Therapeutics Inc. New 1.19% +1.19
LEGN Legend Biotech Corp.-ADR New 1.15% +1.15
STOK Stoke Therapeutics Inc. Add +635.0% 1.19% +1.05
ATRA Atara Biotherapeutics Inc. Add +1458.3% 0.88% +0.86
AURA Aura Biosciences Inc. New 0.59% +0.59
ODTX Odyssey Therapeutics Inc. New 0.52% +0.52
PHVS Pharvaris NV New 0.40% +0.40
NRIX Nurix Therapeutics Inc. New 0.32% +0.32
ELOX Eloxx Pharmaceuticals Inc. New 0.28% +0.28
AARD Aardvark Therapeutics Inc. New 0.11% +0.11

Options Activity Q1 2026 → Q2 2026
CGON CG Oncology Inc. call New 561,500 $39.9M
CNTA Centessa Pharmaceuticals Ltd. call Sold out 410,800 $16.3Mbefore exit
AARD Aardvark Therapeutics Inc. call New 14,700 $85K

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