How We Invest

13F FILER • OLEG NODELMAN

EcoR1 Capital

Oleg Nodelman — EcoR1 Capital, LLC

No writing by this manager has been read and indexed yet, so this page carries the filings only. Holdings come straight from the Form 13F-HR on EDGAR.

33

Positions

$2.1B

Reported Value

86.3%

In Top 10

—

Claims Indexed

Largest reported positions

ECOR1 CAPITAL, LLC • CIK 0001587114 • 2026-06-30 • FILED 2026-08-14

WHAT CHANGED THIS QUARTER

In its Q2 2026 13F, filed Aug 14, 2026, EcoR1 Capital reported 33 positions worth $2.0B in US-listed stock. The largest stock position is Zymeworks Inc at 29.2% of the reported book, and the ten largest lines of any type make up 86.3% of it.

It opened 11 new positions, the largest stock positions being First Tracks Biotherapeutics ($63.9M), Fulcrum Therapeutics Inc ($24.0M) and Legend Biotech Corp ($23.1M), and exited 8, the largest stock exits being Jazz Pharmaceuticals Plc ($322.6M last quarter), Centessa Pharmaceuticals Plc ($238.3M last quarter) and Crinetics Pharmaceuticals In ($155.7M last quarter).

Among positions it already held, the biggest increases by share count were Atara Biotherapeutics Inc (+1458%), Stoke Therapeutics Inc (+635%) and Cg Oncology Inc (+36%), and the biggest cuts were Mereo Biopharma Group Plc (−92%), Relay Therapeutics Inc (−63%) and Erasca Inc (−63%).

Largest reported positions, quarter ended 2026-06-30
IssuerValueWeightShares QoQ
ZYMEWORKS INC$600.4M29.2%—
ANAPTYSBIO INC$531.9M25.9%—
AKTIS ONCOLOGY INC$155.5M7.6%—
CG ONCOLOGY INC$106.2M5.2%+36%
ETON PHARMACEUTICALS INC$78.6M3.8%—
CRISPR THERAPEUTICS AG$75.8M3.7%—
ORIC PHARMACEUTICALS INC$72.9M3.5%—
FIRST TRACKS BIOTHERAPEUTICS$63.9M3.1%New
LAKEFRONT BIOTHERAPEUTICS NV$50.0M2.4%—
NEUROGENE INC$40.0M1.9%—
CG ONCOLOGY INC (Call)$39.9M1.9%New
STOKE THERAPEUTICS INC$24.0M1.2%+635%
FULCRUM THERAPEUTICS INC$24.0M1.2%New
LEGEND BIOTECH CORP$23.1M1.1%New
BRIDGEBIO ONCOLOGY THERAPEUT$21.5M1.1%—
MBX BIOSCIENCES INC$21.4M1.0%-50%
ZENAS BIOPHARMA INC$20.0M1.0%—
ATARA BIOTHERAPEUTICS INC$17.8M0.9%+1458%
RELAY THERAPEUTICS INC$13.1M0.6%-63%
AURA BIOSCIENCES INC$11.8M0.6%New

20 of 33 positions. 1.9% of reported value is options, where the figure is the notional value of the underlying rather than money spent. A 13F covers long US-listed positions at a quarter end only — no shorts, leverage, cash, ordinary bonds or private holdings — and is 45 days old on publication.

NEW POSITIONS

  • First Tracks Biotherapeutics$63.9M · 3.1%
  • Fulcrum Therapeutics Inc$24.0M · 1.2%
  • Legend Biotech Corp$23.1M · 1.1%
  • Aura Biosciences Inc$11.8M · 0.6%
  • Odyssey Therapeutics Inc$10.4M · 0.5%

EXITS

  • Jazz Pharmaceuticals Plc$322.6M last quarter
  • Centessa Pharmaceuticals Plc$238.3M last quarter
  • Crinetics Pharmaceuticals In$155.7M last quarter
  • Xencor Inc$26.3M last quarter
  • Replimune Group Inc$7.7M last quarter

QUESTIONS PEOPLE ASK

What are EcoR1 Capital's largest holdings?

OPEN
As of Jun 30, 2026, the three largest stock positions are Zymeworks Inc (29.2%), Anaptysbio Inc (25.9%) and Aktis Oncology Inc (7.6%), together 62.6% of the reported book.

How big is EcoR1 Capital's 13F portfolio?

OPEN
The Q2 2026 13F, filed Aug 14, 2026, reports 33 positions worth $2.1B. The ten largest make up 86.3% of it. 1.9% of that value is options, reported at the notional value of the underlying rather than money spent.

What did EcoR1 Capital buy and sell in Q2 2026?

OPEN
It opened 11 new positions, the largest stock positions being First Tracks Biotherapeutics ($63.9M), Fulcrum Therapeutics Inc ($24.0M) and Legend Biotech Corp ($23.1M), and exited 8, the largest stock exits being Jazz Pharmaceuticals Plc ($322.6M last quarter), Centessa Pharmaceuticals Plc ($238.3M last quarter) and Crinetics Pharmaceuticals In ($155.7M last quarter). Among positions it already held, the biggest increases by share count were Atara Biotherapeutics Inc (+1458%), Stoke Therapeutics Inc (+635%) and Cg Oncology Inc (+36%), and the biggest cuts were Mereo Biopharma Group Plc (−92%), Relay Therapeutics Inc (−63%) and Erasca Inc (−63%).

When is EcoR1 Capital's next 13F due?

OPEN
The Q3 2026 13F is due Nov 16, 2026. Forty-five days after the quarter ends is November 14, 2026 (Saturday), so the deadline moves to the next business day. Oleg Nodelman's filing usually lands close to the deadline.

Filers with overlapping books