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EcoR1 Capital, LLC

CIK 1587114 · latest 13F filed 14 August 2026 · Read the filing on EDGAR

EcoR1 Capital, LLC reported 31 US-listed holdings worth $2.02 billion in its 13F for the quarter ended 30 June 2026, filed 14 August 2026. Its largest: Zymeworks Inc. (29.8%), Anaptysbio Inc. (26.4%) and Aktis Oncology Inc. (7.7%). Against the quarter before, it opened 9 positions, added to 3, trimmed 4 and sold out of 7.

Reported holdings$2.02B-13.8% on Q1 2026
Positions31+2 on Q1 2026
The largest ten88.0%of its reported holdings
Latest 13FQ2 2026filed 14 August 2026
Where the money is
OpenedAdded toHeld
ZYME29.8%ANAB26.4%AKTS7.7%CGON5.3%ETON3.9%CRSP3.8%ORIC3.6%TRAX3.2%LKFT2.5%NGNE2.0%STOK1.2%FULC1.2%LEGN1.1%BBOT1.1%17 more7.4%

The 14 largest of its 31 positions, each sized by its share of the reported holdings, coloured by the change in shares against Q1 2026.

Reported holdings, quarter by quarter
Q3 2024: $2.92 billion in 63 positions$2.92BQ3 24Q4 2024: $2.50 billion in 55 positions$2.50BQ4 24Q1 2025: $1.68 billion in 44 positions$1.68BQ1 25Q2 2025: $1.69 billion in 36 positions$1.69BQ2 25Q3 2025: $2.08 billion in 30 positions$2.08BQ3 25Q4 2025: $2.19 billion in 28 positions$2.19BQ4 25Q1 2026: $2.34 billion in 29 positions$2.34BQ1 26Q2 2026: $2.02 billion in 31 positions$2.02BQ2 26

What the fund reported holding at each quarter's end; hover a bar for the number of positions

What it did on the quarter

Opened 9Added 3Held 15Trimmed 4Sold out 7
Opened: 9Added: 3Held: 15Trimmed: 4Sold out: 7

Its positions against its 13F for the quarter to 31 March 2026; a change under 0.1% of a position counts as held

Opened 9

  1. First Tracks Biotherapeutics TRAX$63.9 million
  2. Fulcrum Therapeutics Inc. FULC$24.0 million
  3. Legend Biotech Corp. LEGN$23.1 million
  4. Aura Biosciences Inc. AURA$11.8 million
  5. Odyssey Therapeutics, Inc. ODTX$10.4 million
  6. Pharvaris N V PHVS$8.1 million
  7. Nurix Therapeutics Inc. NRIX$6.6 million
  8. Eloxx Pharmaceuticals Inc. ELOX$5.6 million

and 1 more in the table below

Added to 3

  1. CG Oncology Inc. CGON+392,300 shares · +36%
  2. Stoke Therapeutics Inc. STOK+635,000 shares · +635%
  3. Atara Biotherap ATRA+1.5 million shares · +1458%

Trimmed 4

  1. Relay Therapeutics Inc. RLAY-1.2 million shares · -63%
  2. MBX Biosciences Inc. MBX-388,500 shares · -50%
  3. Erasca Inc. ERAS-570,000 shares · -63%
  4. Mereo Biopharma Group PLC MREO-12.4 million shares · -93%

Sold out of 7

  1. Jazz Pharmaceuticals plc JAZZ$322.6 million last quarter
  2. Centessa Pharmaceuticals PLC CNTA$238.3 million last quarter
  3. Crinetics Pharmaceuticals in CRNX$155.7 million last quarter
  4. Xencor Inc. XNCR$26.3 million last quarter
  5. Replimune Group, Inc. REPL$7.7 million last quarter
  6. Prelude Therapeutics Inc. PRLD$3.2 million last quarter
  7. Ibio Inc. Com IBIO$3.0 million last quarter

What it holds

CompanySharesValueOf its bookChange in shares
Zymeworks Inc. ZYME22,970,388$600.4 million29.77%no change
Anaptysbio Inc. ANAB7,880,094$531.9 million26.37%no change
Aktis Oncology Inc. AKTS4,824,469$155.5 million7.71%no change
CG Oncology Inc. CGON1,494,300$106.2 million5.26%+392,300
Eton Pharmaceuticals Inc. ETON2,171,938$78.6 million3.90%no change
Crispr Therapeutics AG CRSP1,389,276$75.8 million3.76%no change
Oric Pharmaceuticals Inc. ORIC6,728,116$72.9 million3.61%no change
First Tracks Biotherapeutics TRAX3,174,519$63.9 million3.17%new
Galapagos NV LKFT1,667,119$50.0 million2.48%no change
Neurogene Inc. NGNE1,271,342$40.0 million1.98%no change
Stoke Therapeutics Inc. STOK735,000$24.0 million1.19%+635,000
Fulcrum Therapeutics Inc. FULC6,549,866$24.0 million1.19%new
Legend Biotech Corp. LEGN800,000$23.1 million1.15%new
Bridgebio Oncology Therapeutics Ord BBOT2,823,126$21.5 million1.07%no change
MBX Biosciences Inc. MBX388,500$21.4 million1.06%-388,500
Zenas Biopharma Inc. ZBIO789,500$20.0 million0.99%no change
Atara Biotherap ATRA1,552,000$17.8 million0.88%+1,452,407
Relay Therapeutics Inc. RLAY697,948$13.1 million0.65%-1,206,814
Aura Biosciences Inc. AURA1,666,667$11.8 million0.59%new
Odyssey Therapeutics, Inc. ODTX555,555$10.4 million0.52%new
Eikon Therapeutics Inc. EIKN732,606$9.6 million0.47%no change
Pharvaris N V PHVS235,000$8.1 million0.40%new
Zura Bio Ltd ZURA1,179,715$7.0 million0.35%no change
Phathom Pharmaceuticals Inc. PHAT625,000$6.8 million0.34%no change
Nurix Therapeutics Inc. NRIX270,000$6.6 million0.32%new
Erasca Inc. ERAS330,000$6.0 million0.30%-570,000
Eloxx Pharmaceuticals Inc. ELOX400,000$5.6 million0.28%new
Aardvark Therapeutics Inc. AARD396,194$2.3 million0.11%new
Helix Acquisition Corp. III HLXC200,000$2.1 million0.11%no change
Mereo Biopharma Group PLC MREO1,000,000$317,7000.02%-12,368,855
Surrozen Inc SRZNW4,444$115,3220.01%no change
Every US-listed position in the fund's 13F for the quarter ended 30 June 2026, by the value it reported.
Read moreChange is shares against its 13F for the quarter before; the 7 it sold out of are in the box above.

Options it reported

CompanyOptionShares under the optionsValue of those shares
CG Oncology Inc. CGONCalls561,500$39.9 million
Aardvark Therapeutics Inc. AARDCalls14,700$84,672

2 option lines. A 13F lists calls and puts by the shares they cover and what those shares were worth at the quarter's end, not what the options cost; they are not counted in the holdings above.