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EcoR1 Capital, LLC

Institutional InvestorSimilar funds →SEC EDGAR: CIK 1587114
Institutional-grade research for retail investors

Sector Allocation

  • Healthcare97.4%$2.0B
  • Other2.6%$52.1M

AUM History

13fpro.ai/research/fund/ecor1-capital-llc-1587114

Largest positions — Q2 2026

Top 20 stock positions. Options are left out: 13F reports them at the underlying's value.

13fpro.ai/research/fund/ecor1-capital-llc-1587114

EcoR1 Capital, LLC 13F holdings — Q2 2026

$2.1B portfolio (-12.7% QoQ) · 33 holdings · Q2 2026 13F · top 10 are 88% of the stock portfolio

Includes $40.0M of put/call options ($0 puts, $40.0M calls), which 13F rules report at the value of the underlying shares, not the premium at risk. Stocks alone: $2.0B. Weights use the stock portfolio.

All holdings — EcoR1 Capital, LLC (Q2 2026)

33 disclosed positions from the Form 13F-HR on SEC EDGAR, with quarter-over-quarter share changes. Largest by value first; the ten above are not repeated.

Company
CGON$CGONCALLCG Oncology, Inc.$39.9MNew
STOK$STOKStoke Therapeutics, Inc.$24.0M+635%
FULC$FULCFulcrum Therapeutics, Inc.$24.0MNew
LEGN$LEGNLegend Biotech Corpadr$23.1MNew
BBOT$BBOTBridgeBio Oncology Therapeutics, Inc.$21.5M—
MBX$MBXMBX Biosciences, Inc.$21.4M-50%
ZBIO$ZBIOZenas BioPharma, Inc.$20.0M—
ATRA$ATRAAtara Biotherapeutics, Inc.$17.8M+1458%
RLAY$RLAYRelay Therapeutics, Inc.$13.1M-63%
AURA$AURAAura Biosciences, Inc.$11.8MNew
ODTX$ODTXOdyssey Therapeutics, Inc.$10.4MNew
EIKN$EIKNEikon Therapeutics, Inc.$9.6M—
PHVS$PHVSPharvaris N.V.$8.1MNew
ZURA$ZURAZura Bio Ltd$7.0M—
PHAT$PHATPhathom Pharmaceuticals, Inc.$6.8M—

What changed in Q2 2026

Against the previous quarter's 13F: 11 new, 3 added to, 4 trimmed, 8 sold out. Share-count changes; largest moves by dollar size first.

New positions (11)

  • TRAX$TRAXFirst Tracks Biotherapeutics, Inc.$63.9M

    first bought this quarter

  • CGON$CGONCALLCG Oncology, Inc.$39.9M

    first bought this quarter

  • FULC$FULCFulcrum Therapeutics, Inc.$24.0M

    first bought this quarter

  • LEGN$LEGNLegend Biotech Corp$23.1M

    first bought this quarter

  • AURA$AURAAura Biosciences, Inc.$11.8M

    first bought this quarter

  • ODTX$ODTXOdyssey Therapeutics, Inc.$10.4M

    first bought this quarter

+5 more in the Excel export

Added to (3)

  • CGON$CGONCG Oncology, Inc.+36%

    now $106.2M · held 3 qtrs, 3 adds in a row

  • STOK$STOKStoke Therapeutics, Inc.+635%

    now $24.0M · held 2 qtrs, 2 adds in a row

  • ATRA$ATRAAtara Biotherapeutics, Inc.+1458%

    now $17.8M · held 10+ qtrs

Trimmed (4)

  • RLAY$RLAYRelay Therapeutics, Inc.-63%

    now $13.1M · held 2 qtrs

  • MBX$MBXMBX Biosciences, Inc.-50%

    now $21.4M · held 8 qtrs, 2 trims in a row

  • ERAS$ERASErasca, Inc.-63%

    now $6.0M · held 2 qtrs

  • MREO$MREOMereo BioPharma Group plc-93%

    now $318K · held 3 qtrs

Sold out (8)

  • JAZZ$JAZZJazz Pharmaceuticals plcwas $322.6M

    held 9+ qtrs

  • CNTA$CNTACentessa Pharmaceuticals plcwas $238.3M

    held 3 qtrs

  • CRNX$CRNXCrinetics Pharmaceuticals, Inc.was $155.7M

    held 9+ qtrs

  • XNCR$XNCRXencor Incwas $26.3M

    held 9+ qtrs

  • CNTA$CNTACALLCentessa Pharmaceuticals plcwas $16.3M
  • REPL$REPLReplimune Group, Inc.was $7.7M

    held 1 qtr

+2 more in the Excel export

Firm AUM (Form ADV): $3.4B as of 2025-12-31 · SEC IAPD

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Holdings by quarter

Every 13F EcoR1 Capital, LLC has filed, 38 earlier quarters. Pick one to see what it held then.

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Q2 2026 13F filed with the SEC on Aug 14, 2026. Prices are closing prices as of Oct 26, 2026.

Average quality of EcoR1 Capital's top 20 holdings: 36/100 (our AI quality score, weighted by position size; 12 of the 20 are scored)

Top 10 since filing

-8.6%

Value-weighted move of the 10 largest stock positions

Turnover

10%

Last quarter; 39% over the last 4

Top 10 weight

88%

Share of the stock portfolio in its 10 largest positions

Held 4+ quarters

74%

Share of portfolio value in positions held a year or more

Highest-quality names it owns(among its 100 largest positions)

The 8 highest-scoring companies in this portfolio are a Pro feature.

How these are measured
  • Moves since the quarter-end and since the filing date use our own daily closing prices, from the close on (or just before) each date to the latest close.
  • Turnover is the lesser of shares bought or sold in a quarter, valued at the quarter-end prices in the 13F, divided by the average of the two quarters' stock portfolio values.
  • Quarters held and add/trim streaks count back only through quarters whose filed holdings add up to the filing's own cover-page total (back to Q1 2024 for this fund). A change counts as an add or a trim when the split-adjusted share count moves by more than 1%.
  • Estimate, not the fund's reported cost. For each quarter in the current holding period in which the fund's share count rose (split-adjusted), we take that quarter's average daily close and weight it by the shares added; sales do not change an average cost. Quarters where the stock's price history and the 13F's own implied price disagree by more than 2x are left out.
  • Put and call option rows report the value of the underlying shares, not a position the fund paid for, so they are left out of all of the above.

Portfolio Overview

EcoR1 Capital, LLC disclosed 33 positions worth $2.1B in its Form 13F-HR for Q2 2026 — $2.0B in common stock plus $40.0M of put/call option positions (reported at underlying notional value, not premium at risk), led by $ZYME (Zymeworks Inc.) at 29.8% of the equity portfolio, followed by $ANAB and $AKTS. During the quarter the fund opened 11 new positions and exited 8 — including a new stake in $TRAX and a full exit from $JAZZ. The portfolio is most concentrated in Healthcare (97.4% of disclosed assets). All figures are sourced directly from EcoR1 Capital, LLC’s Form 13F-HR filing with the SEC under CIK 1587114.

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AI-Powered Hedge Fund Analysis: EcoR1 Capital, LLC

13F Pro is an AI hedge fund tracker and stock research platform. For EcoR1 Capital, LLC (SEC CIK: 1587114), the platform ingests every quarterly Form 13F filing and applies AI-powered analysis on top — 10 specialized AI analysts (value, growth, momentum, macro, activist, and more) debate the fund's top positions and publish AI-generated analysis with cited SEC sources.

Every holding in EcoR1 Capital, LLC's portfolio is scored on an AI quality ranking built from its SEC filings (ROIC, FCF margin, revenue growth, institutional flow, earnings quality, shareholder dilution, and more). Track accumulation and distribution quarter over quarter, identify conviction positions, and see AI stock analysis for each position — alongside 8,700+ other institutional filers and 2,800+ AI-ranked companies.