EcoR1 Capital, LLC
Reported holdings as of Q2 2026, from 31 quarterly filings.
This filer last reported in Q2 2026; the most recent quarter on file across all filers is Q3 2026. Firms that restructure stop filing under one CIK and start under another, so a successor entity may hold these positions now under a similar name.
Holdings
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| Security | Ticker | Value | Shares | Weight | Weight change | Held | Change |
|---|---|---|---|---|---|---|---|
| ZYMEWORKS INC | ZYME | $600.4M | 22,970,388 | +4.78pp | 15q | HELD | |
| ANAPTYSBIO INC | ANAB | $531.9M | 7,880,094 | +7.31pp | 27q | HELD | |
| AKTIS ONCOLOGY INC | AKTS | $155.5M | 4,824,469 | +3.90pp | 2q | HELD | |
| CG ONCOLOGY INC CALL | CGON | $146.1M | 1,494,300 | +3.94pp | 3q | +35.6%+$38.3M | |
| ETON PHARMACEUTICALS INC | ETON | $78.6M | 2,171,938 | +1.55pp | 8q | HELD | |
| CRISPR THERAPEUTICS AG | CRSP | $75.8M | 1,389,276 | +0.88pp | 10q | HELD | |
| ORIC PHARMACEUTICALS INC | ORIC | $72.9M | 6,728,116 | -0.07pp | 25q | HELD | |
| FIRST TRACKS BIOTHERAPEUTICS | TRAX | $63.9M | 3,174,519 | - | new | NEW | |
| LAKEFRONT BIOTHERAPEUTICS NV | LKFT | $50.0M | 1,667,119 | +0.31pp | 20q | HELD | |
| NEUROGENE INC | NGNE | $40.0M | 1,271,342 | +0.86pp | 11q | HELD | |
| STOKE THERAPEUTICS INC | STOK | $24.0M | 735,000 | +1.03pp | 2q | +635.0%+$20.8M | |
| FULCRUM THERAPEUTICS INC | FULC | $24.0M | 6,549,866 | - | new | NEW | |
| LEGEND BIOTECH CORP | LEGN | $23.1M | 800,000 | - | new | NEW | |
| BRIDGEBIO ONCOLOGY THERAPEUT | BBOT | $21.5M | 2,823,126 | -0.03pp | 4q | HELD | |
| MBX BIOSCIENCES INC | MBX | $21.4M | 388,500 | +0.06pp | 8q | -50.0%-$21.4M | |
| ZENAS BIOPHARMA INC | ZBIO | $20.0M | 789,500 | +0.32pp | 3q | HELD | |
| ATARA BIOTHERAPEUTICS INC | ATRA | $17.8M | 1,552,000 | +0.85pp | 9q | +1458.3%+$16.7M | |
| RELAY THERAPEUTICS INC | RLAY | $13.1M | 697,948 | -0.17pp | 2q | -63.4%-$22.6M | |
| AURA BIOSCIENCES INC | AURA | $11.8M | 1,666,667 | - | new | NEW | |
| ODYSSEY THERAPEUTICS INC | ODTX | $10.4M | 555,555 | - | new | NEW | |
| EIKON THERAPEUTICS INC | EIKN | $9.6M | 732,606 | +0.14pp | 2q | HELD | |
| PHARVARIS N V | PHVS | $8.1M | 235,000 | - | new | NEW | |
| ZURA BIO LTD | ZURA | $7.0M | 1,179,715 | +0.04pp | 2q | HELD | |
| PHATHOM PHARMACEUTICALS INC | PHAT | $6.8M | 625,000 | +0.04pp | 2q | HELD | |
| NURIX THERAPEUTICS INC | NRIX | $6.6M | 270,000 | - | new | NEW | |
| ERASCA INC | ERAS | $6.0M | 330,000 | -0.32pp | 2q | -63.3%-$10.4M | |
| ELOXX PHARMACEUTICALS INC | $5.6M | 400,000 | - | new | NEW | ||
| AARDVARK THERAPEUTICS INC CALL | AARD | $2.4M | 396,194 | - | new | NEW | |
| HELIX ACQUISITION CORP III | HLXC | $2.1M | 200,000 | +0.02pp | 2q | HELD | |
| MEREO BIOPHARMA GROUP PLC | MREO | $317.7K | 1,000,000 | -0.17pp | 3q | -92.5%-$3.9M | |
| SURROZEN INC? | SRZNW | $115.3K | 4,444? | flat | 20q |
By sector
Industry comes from the SIC code on each company's own SEC filings, which is self-reported and sometimes out of date. Derivative exposure is counted with the shares. Securities the SEC assigns no industry - funds, trusts, foreign issues - are shown as not classified rather than dropped.
| Sector | Value | Share |
|---|---|---|
| Biotech & Pharma | $2.0B | 96.0% |
| Other sectors | $2.1M | 0.1% |
| Not classified | $79.8M | 3.9% |
What the disclosed book did
This is not the fund's return. A 13F shows long US equity positions only, so shorts, bonds, foreign listings, private holdings and cash are all invisible here. What this measures is the quarter's change in value of the positions this manager disclosed, had they been left untouched - the return a reader following the filing would have earned.
| Quarter | Book | Market | Difference | Priced |
|---|---|---|---|---|
| Q2 2026 | +18.0% | +14.8% | +3.2% | 89% |
| Q1 2026 | +2.5% | -4.6% | +7.1% | 99% |
| Q4 2025 | +19.0% | +2.4% | +16.6% | 99% |
| Q3 2025 | +43.1% | +7.8% | +35.3% | 93% |
| Q2 2025 | -5.5% | +10.5% | -16.0% | 100% |
| Q1 2025 | -29.0% | -4.6% | -24.5% | 100% |
| Q4 2024 | -13.4% | +2.1% | -15.6% | 100% |
| Q3 2024 | +0.6% | +5.4% | -4.9% | 95% |
Market is SPY over the same two quarter ends, priced the same way as everything else here - the median across every filer reporting it. It is a large-cap US proxy, so a manager holding small caps or biotech will beat or trail it for reasons that are not skill. Prices are quarter-end to quarter-end and say nothing about the path in between, or about trades opened and closed inside a quarter.
Quarter by quarter
| Quarter | Value | Positions | New | Added | Trimmed | Exited | Top 10 | Days to file |
|---|---|---|---|---|---|---|---|---|
| Q2 2026 | $2.1B | 31 | 9 | 3 | 4 | 7 | 88.2% | 45 |
| Q1 2026 | $2.4B | 29 | 10 | 4 | 4 | 9 | 89.6% | 45 |
| Q4 2025 | $2.2B | 28 | 9 | 2 | 3 | 11 | 84.6% | 48 |
| Q3 2025 | $2.1B | 30 | 6 | 4 | 3 | 12 | 80.6% | 45 |
| Q2 2025 | $1.7B | 36 | 6 | 5 | 4 | 14 | 77.4% | 45 |
| Q1 2025 | $1.7B | 44 | 5 | 8 | 4 | 18 | 80.1% | 45 |
| Q4 2024 | $2.6B | 57 | 10 | 7 | 9 | 16 | 67.7% | 45 |
| Q3 2024 | $2.9B | 63 | 14 | 7 | 5 | 6 | 63.8% | 45 |
| Q2 2024 | $3.3B | 55 | 7 | 5 | 4 | 9 | 61.4% | 45 |
| Q1 2024 | $4.0B | 57 | 16 | 8 | 3 | 10 | 61.5% | 45 |
| Q4 2023 | $3.9B | 51 | 10 | 9 | 4 | 8 | 72.2% | 45 |
| Q3 2023 | $3.0B | 49 | 7 | 6 | 3 | 10 | 73.5% | 45 |
| Q2 2023 | $4.1B | 52 | 10 | 11 | 5 | 16 | 75.1% | 45 |
| Q1 2023 | $3.1B | 58 | 5 | 9 | 9 | 13 | 73.6% | 45 |
| Q4 2022 | $3.3B | 66 | 9 | 10 | 4 | 18 | 70.2% | 45 |
| Q3 2022 | $3.4B | 75 | 8 | 8 | 15 | 13 | 67.9% | 45 |
| Q2 2022 | $2.9B | 80 | 12 | 14 | 5 | 19 | 60.6% | 46 |
| Q1 2022 | $3.2B | 87 | 22 | 20 | 16 | 10 | 58.8% | 46 |
| Q4 2021 | $3.1B | 75 | 20 | 9 | 2 | 16 | 65.4% | 45 |
| Q3 2021 | $2.9B | 71 | 12 | 13 | 9 | 13 | 71.7% | 53 |
| Q2 2021 | $2.7B | 72 | 13 | 15 | 6 | 11 | 68.0% | 47 |
| Q1 2021 | $2.3B | 70 | 20 | 9 | 4 | 16 | 65.0% | 47 |
| Q4 2020 | $1.9B | 66 | 31 | 3 | 8 | 12 | 60.4% | 47 |
| Q3 2020 | $1.4B | 47 | 17 | 6 | 5 | 18 | 65.7% | 47 |
| Q2 2020 | $1.4B | 48 | 19 | 13 | 8 | 22 | 60.3% | 45 |
| Q1 2020 | $957.2M | 51 | 21 | 8 | 13 | 13 | 58.5% | 45 |
| Q4 2019 | $1.1B | 43 | 18 | 9 | 9 | 11 | 64.3% | 49 |
| Q3 2019 | $791.9M | 36 | 9 | 6 | 13 | 11 | 74.8% | 45 |
| Q2 2019 | $989.6M | 38 | 11 | 8 | 10 | 14 | 71.9% | 45 |
| Q1 2019 | $1.1B | 41 | 9 | 6 | 13 | 21 | 60.8% | 45 |
| Q4 2018 | $999.4M | 53 | 0 | 0 | 0 | 0 | 53.5% | 45 |
Rows marked UNVERIFIED ID, PLACEHOLDER ID, TICKER AS ID or NON-CUSIP ID carry an identifier that is not a valid CUSIP. They are shown because the filer reported that money, but treat the security named with caution - hover the chip for what is wrong with it, and see the methodology.
Held counts consecutive filings in which this manager reported the position, and can reach further back than the quarters listed above: the tabs begin at Q4 2018 because earlier coverage is too sparse to describe a market, but tenure is counted over every filing we hold, some reaching to 2007. A position sold and later rebought starts again from one.
Weight change is the shift in this position's share of the whole book, in percentage points. It is the more useful column: when money flows into or out of a broad fund, almost every holding is bought or sold at once, so added and trimmed largely track flows. A weight that rose while the book shrank is a decision. Both compare with the previous quarter this filer reported, not the previous calendar quarter.