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EcoR1 Capital 13F Holdings (Q2 2026)
According to its SEC 13F filed on Aug 14, 2026, EcoR1 Capital reported 31 long positions worth $2.06B as of Jun 30, 2026. ZYME is 29.2% of the portfolio and the top 10 holdings are 86%. Against Q1 2026 it opened 11 new positions, added to 3, trimmed 4 and exited 8. 7 holdings have a dated FDA decision or data readout in the next 90 days, and 9 more expect one in a stated window such as "H2 2026".
Holdings
Every position in the 13F, with the change since the fund's previous filing, how many of the 45 specialist funds also own it, and its next FDA catalyst. Option positions are labelled CALL or PUT.
| Stock | Company Name | Shares Held | Market Value | % of Portfolio | QoQ Change | Position Change | Also Held By | Stage | Next Catalyst |
|---|---|---|---|---|---|---|---|---|---|
 ELOX | ELOXX PHARMACEUTICALS INC | 400.00 K | 5.55 M | 0.3 | New | — | None in 90 days | ||
TRAX | FIRST TRACKS BIOTHERAPEUTICS | 3.17 M | 63.87 M | 3.1 | New | — | Nov 30, 2026 Phase 1b data presentation | ||
 MBX | MBX BIOSCIENCES INC | 388.50 K | 21.45 M | 1 | Trimmed -50% | Clinical | Expected 2026 Phase 2a data readout | ||
 ETON | ETON PHARMACEUTICALS INC | 2.17 M | 78.62 M | 3.8 | Unchanged | — | Expected by end of 2026 NDA Submission | ||
 ERAS | ERASCA INC | 330.00 K | 6.05 M | 0.3 | Trimmed -63% | Clinical | Nov 20, 2026 Pre-clinical data presentation | ||
 NRIX | NURIX THERAPEUTICS INC | 270.00 K | 6.55 M | 0.3 | New | Clinical | None in 90 days |
Top 20 Holdings
Size = share of the portfolio. Option positions show CALL or PUT.
Who else owns these stocks?
All Stock Holdings ranks every biotech stock by how many of the 45 specialist funds own it, and whether that number rose or fell this quarter. Click "of 45 funds" on any row above, or open the full view.
Questions about EcoR1 Capital's 13F
What does EcoR1 Capital own?
31 stocks worth $2.06B at Jun 30, 2026, as reported in its 13F, led by ZYME (29.2% of the portfolio). The full list is in the Holdings table above.
What did it buy and sell last quarter?
Against Q1 2026: 11 new positions, 3 increases, 4 reductions and 8 full exits, from its 13F filings.
How current is this data?
13F filings are due 45 days after each quarter ends, so they show positions at quarter end, not today. The next filing (Q3 2026) is due Nov 16, 2026.
Why are some positions labelled CALL or PUT?
Those are option positions (calls and puts). The 13F reports them as the shares underlying the option, with no strike or expiry, so they are listed apart from share positions.
Source: SEC EDGAR Form 13F-HR filed by EcoR1 Capital, LLC, accession 0000935836-26-000415, filed Aug 14, 2026. Values as filed; option positions are shown at the value of the underlying shares and labelled CALL or PUT.