EcoR1 Capital portfolio
Concentrated managerInvestment firmPortfolio as of Jun 30, 2026 (Q2 2026) · filed with the SEC on Aug 14, 2026 · data updated on Nov 5, 2026 · Q2 2026 13F (filing) ↗ · all its 13F filings ↗
A 13F shows the portfolio at quarter-end and is filed up to 45 days later: these are not real-time positions and they may have changed.
EcoR1 Capital reported a $2.0 bn portfolio of 31 positions to the SEC as of the end of Q2 2026. Its largest positions are ZYME, ANAB, AKTS. During the quarter it opened Fulcrum Therapeutics and Legend Biotech and exited Jazz Pharmaceuticals and Crinetics Pharmaceuticals.
Sections with a free account
What it reported after the quarter end (Q2 2026)
The 13F shows the portfolio as of Jun 30, 2026. Since then EcoR1 Capital has filed these own trades with the SEC (Form 4, when it owns more than 10% of a company or holds a role in it) and stakes above 5% (13D and 13G). It is not everything it did: only what it must report before the next 13F.
What changed this quarter
19 positions with a change (6 new, 3 added to, 4 trimmed, 6 sold); also, 2 entered through an IPO, 1 exited through an acquisition or merger, 1 entered through a spin-off. 11 are listed here: those of 0.5 points of the portfolio or more (up to 12).
- Newly listedOdyssey TherapeuticsODTX0.5% of the portfolio
It started trading this quarter: it appears in a 13F for the first time. The filing does not say whether the manager already held it before the listing, so it is not counted as a purchase.
- Jazz Pharmaceuticals−13.8 ppof portfolioSold out13.8% → —
- Crinetics Pharmaceuticals−6.7 ppof portfolioSold out6.7% → —
- CG Oncology+36%more sharesIncreased3.2% → 5.3%
- Xencor−1.1 ppof portfolioSold out1.1% → —
- Fulcrum Therapeutics+1.0 ppof portfolioNew— → 1.2%
- Legend Biotech+1.0 ppof portfolioNew— → 1.1%
- MBX Biosciences−50%fewer sharesReduced1.0% → 1.1%
- Stoke Therapeutics+635%more sharesIncreased0.1% → 1.2%
- Relay Therapeutics−63%fewer sharesReduced0.8% → 0.6%
- Atara Biotherapeutics+1,458%more sharesIncreasedunder 0.1% → 0.9%
- Aura Biosciences+0.5 ppof portfolioNew— → 0.6%
The figure on the right: for positions added to or trimmed, the change in the number of shares (%); for new and sold ones, the points of the portfolio moved (pp). Below, the portfolio weight before → after. Traded weight: what it bought or sold, excluding price effects.
Top holdings
- ZymeworksZYME29.8%
- AnaptysbioANAB26.4%
- Aktis OncologyAKTS7.7%
- CG OncologyCGON5.3%
- Eton PharmaceuticalsETON3.9%
- Crispr TherapeuticsCRSP3.8%
- ORIC PharmaceuticalsORIC3.6%
- First Tracks BiotherapeuticsTRAX3.2%
- Lakefront BiotherapeuticsLKFT2.5%
- NeurogeneNGNE2.0%
- Stoke TherapeuticsSTOK1.2%
- Fulcrum TherapeuticsFULC1.2%
- Legend BiotechLEGN1.1%
- BridgeBio Oncology TherapeuticsBBOT1.1%
- MBX BiosciencesMBX1.1%
“Since”: first quarter of the current run, unbroken until today. In the details, prices are the quarter-end prices of the quarters in which it added shares, per the 13F. The manager may have bought at any price within each quarter; the SEC only publishes the value at quarter end.
Portfolio by sector
- ● Health Care 100%
How its portfolio changed (8 quarters)
Q2 2026: 31
Q2 2026: 88%
Q2 2026: 15.6%
Traded turnover: the weight it bought plus the weight it sold in the quarter, divided by two, excluding price moves. The plain “turnover” in the header does include that effect. With a free account: the full history and sectors over time.
Declared options (2)
Besides stocks, EcoR1 Capital declared 2 calls (they gain if it rises) with a notional of $40.0M. The 13F reports the value of the underlying shares, not the premium paid, so these figures look large and are not added to the portfolio. Nor does it say whether the option is bought or written, or its strike or expiry: it may be a hedge.
- CALLCG OncologyCGONnew this quarter$39.9M
- CALLAardvark TherapeuticsAARDnew this quarter$84.7K
Stakes above 5% (13D/13G)
Companies where this filer reported holding 5% or more of the shares. It is the figure from its latest filing on each one; history since December 2024.
How we classify it
Investment firm, per its Form ADV of Mar 30, 2026 (high confidence).
The data, as reported: ECOR1 CAPITAL, LLC (CRD 167121): 7.B private funds: 2 hedge, 1 vc (gross assets $3.4 bn); 5.D assets by client type: pooled vehicles 100% (of $3.4 bn)
The type comes from a rule applied to that data. If it looks wrong, tell us.
Similar managers by type and size
Same type of filer and a 13F portfolio value between a third and three times this one. It is not a comparison of what they hold.
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