13-F holdings, Q2 2026
EcoR1 Capital, LLC
A 13-F is the report large US investment managers file with the SEC each quarter, listing the stocks they held at quarter end.
- Reported value
- $2.1B
- Positions
- 31
- Filed
- Data as of
These holdings are as of , 136 days ago.
13-Fs for Q3 2026 are due by .
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Top holdings
- ZYME$600.4M22,970,388 shares29.2% of the book
- ANAB$531.9M7,880,094 shares25.9% of the book
- AKTS$155.5M4,824,469 shares7.6% of the book
- CGON$106.2M1,494,300 shares5.2% of the book
- ETON$78.6M2,171,938 shares3.8% of the book
- CRSP$75.8M1,389,276 shares3.7% of the book
- ORIC$72.9M6,728,116 shares3.5% of the book
- TRAX$63.9M3,174,519 shares3.1% of the book
- GLPG$50M1,667,119 shares2.4% of the book
- NGNE$40M1,271,342 shares1.9% of the book
What changed this quarter
6 new positions and 7 sold out, against Q1 2026. Added and trimmed positions use the change in split-adjusted shares at the Q2 2026 implied price; full exits use their Q1 2026 reported value, not sale proceeds.
Largest buys
- CGON
CG ONCOLOGY INC
+$27.9M
+35.6% shares
Your stake and evidence for CGON
What it means for you
This public view does not read your holdings or watchlist; open the member view to check your stake.
Use this to decide what to research, rather than as an instruction to copy a trade.
What happened
Reported shares increased between Q1 2026 and Q2 2026.
Displayed change: +$27.9M. The current book reports 1,494,300 shares.
Why it can matter
A change between quarter-end disclosures can prompt a question about the manager's exposure. It does not reveal the trade date, the execution price or why the position changed; a full exit is not proof of a bearish decision.
How we got this
For an added or trimmed position, subtract split-adjusted prior shares from current shares, then multiply by the current book's reported value per share; this is not the execution price.
1,494,300 current shares − 1,102,000 prior shares on the same basis = +392,300 shares.
Comparable books exclude identified CUSIP, share-basis and new-security events from trades. Exit-size bands describe prior book weight, not the manager's intent.
Where the data comes from
SEC 13F quarter-end holdings for Q1 2026 and Q2 2026; these delayed disclosures omit shorts and many other assets.
Current source filed .
Technical details
Reported dollar change: 27872915 USD. Current reported shares: 1494300. Prior shares on current basis: 1102000.
- FULC
FULCRUM THERAPEUTICS INC
+$24M
New
Your stake and evidence for FULC
What it means for you
This public view does not read your holdings or watchlist; open the member view to check your stake.
Use this to decide what to research, rather than as an instruction to copy a trade.
What happened
A position newly appears in the Q2 2026 book.
Displayed change: +$24M. The current book reports 6,549,866 shares.
Why it can matter
A change between quarter-end disclosures can prompt a question about the manager's exposure. It does not reveal the trade date, the execution price or why the position changed; a full exit is not proof of a bearish decision.
How we got this
A new position uses its current quarter's reported dollar value; this is not the amount spent buying it.
Comparable books exclude identified CUSIP, share-basis and new-security events from trades. Exit-size bands describe prior book weight, not the manager's intent.
Where the data comes from
SEC 13F quarter-end holdings for Q1 2026 and Q2 2026; these delayed disclosures omit shorts and many other assets.
Current source filed .
Technical details
Reported dollar change: 23972510 USD. Current reported shares: 6549866. Prior shares on current basis: not recorded.
- LEGN
LEGEND BIOTECH CORP
+$23.1M
New
Your stake and evidence for LEGN
What it means for you
This public view does not read your holdings or watchlist; open the member view to check your stake.
Use this to decide what to research, rather than as an instruction to copy a trade.
What happened
A position newly appears in the Q2 2026 book.
Displayed change: +$23.1M. The current book reports 800,000 shares.
Why it can matter
A change between quarter-end disclosures can prompt a question about the manager's exposure. It does not reveal the trade date, the execution price or why the position changed; a full exit is not proof of a bearish decision.
How we got this
A new position uses its current quarter's reported dollar value; this is not the amount spent buying it.
Comparable books exclude identified CUSIP, share-basis and new-security events from trades. Exit-size bands describe prior book weight, not the manager's intent.
Where the data comes from
SEC 13F quarter-end holdings for Q1 2026 and Q2 2026; these delayed disclosures omit shorts and many other assets.
Current source filed .
Technical details
Reported dollar change: 23104000 USD. Current reported shares: 800000. Prior shares on current basis: not recorded.
- STOK
STOKE THERAPEUTICS INC
+$20.8M
+635% shares
Your stake and evidence for STOK
What it means for you
This public view does not read your holdings or watchlist; open the member view to check your stake.
Use this to decide what to research, rather than as an instruction to copy a trade.
What happened
Reported shares increased between Q1 2026 and Q2 2026.
Displayed change: +$20.8M. The current book reports 735,000 shares.
Why it can matter
A change between quarter-end disclosures can prompt a question about the manager's exposure. It does not reveal the trade date, the execution price or why the position changed; a full exit is not proof of a bearish decision.
How we got this
For an added or trimmed position, subtract split-adjusted prior shares from current shares, then multiply by the current book's reported value per share; this is not the execution price.
735,000 current shares − 100,000 prior shares on the same basis = +635,000 shares.
Comparable books exclude identified CUSIP, share-basis and new-security events from trades. Exit-size bands describe prior book weight, not the manager's intent.
Where the data comes from
SEC 13F quarter-end holdings for Q1 2026 and Q2 2026; these delayed disclosures omit shorts and many other assets.
Current source filed .
Technical details
Reported dollar change: 20777200 USD. Current reported shares: 735000. Prior shares on current basis: 100000.
- ATRA
ATARA BIOTHERAPEUTICS INC
+$16.7M
+1,458.3% shares
Your stake and evidence for ATRA
What it means for you
This public view does not read your holdings or watchlist; open the member view to check your stake.
Use this to decide what to research, rather than as an instruction to copy a trade.
What happened
Reported shares increased between Q1 2026 and Q2 2026.
Displayed change: +$16.7M. The current book reports 1,552,000 shares.
Why it can matter
A change between quarter-end disclosures can prompt a question about the manager's exposure. It does not reveal the trade date, the execution price or why the position changed; a full exit is not proof of a bearish decision.
How we got this
For an added or trimmed position, subtract split-adjusted prior shares from current shares, then multiply by the current book's reported value per share; this is not the execution price.
1,552,000 current shares − 99,593 prior shares on the same basis = +1,452,407 shares.
Comparable books exclude identified CUSIP, share-basis and new-security events from trades. Exit-size bands describe prior book weight, not the manager's intent.
Where the data comes from
SEC 13F quarter-end holdings for Q1 2026 and Q2 2026; these delayed disclosures omit shorts and many other assets.
Current source filed .
Technical details
Reported dollar change: 16673632.360000001 USD. Current reported shares: 1552000. Prior shares on current basis: 99593.
Largest sells
- JAZZ
JAZZ PHARMACEUTICALS PLC
−$322.6M
Sold out, was 13.8% of the book
Your stake and evidence for JAZZ
What it means for you
This public view does not read your holdings or watchlist; open the member view to check your stake.
Use this to decide what to research, rather than as an instruction to copy a trade.
What happened
The position reported in Q1 2026 is absent from the comparable Q2 2026 book.
Displayed change: −$322.6M. This was 13.8% of the prior book.
Why it can matter
A change between quarter-end disclosures can prompt a question about the manager's exposure. It does not reveal the trade date, the execution price or why the position changed; a full exit is not proof of a bearish decision.
How we got this
A full exit is shown as the negative of its prior reported value, not sale proceeds or a value at today's price.
Comparable books exclude identified CUSIP, share-basis and new-security events from trades. Exit-size bands describe prior book weight, not the manager's intent.
Where the data comes from
SEC 13F quarter-end holdings for Q1 2026 and Q2 2026; these delayed disclosures omit shorts and many other assets.
Current source filed .
Technical details
Reported dollar change: -322608000 USD. Current reported shares: not recorded. Prior shares on current basis: 1706469.
- CNTA
CENTESSA PHARMACEUTICALS PLC
−$238.3M
Sold out, was 10.2% of the book
Your stake and evidence for CNTA
What it means for you
This public view does not read your holdings or watchlist; open the member view to check your stake.
Use this to decide what to research, rather than as an instruction to copy a trade.
What happened
The position reported in Q1 2026 is absent from the comparable Q2 2026 book.
Displayed change: −$238.3M. This was 10.2% of the prior book.
Why it can matter
A change between quarter-end disclosures can prompt a question about the manager's exposure. It does not reveal the trade date, the execution price or why the position changed; a full exit is not proof of a bearish decision.
How we got this
A full exit is shown as the negative of its prior reported value, not sale proceeds or a value at today's price.
Comparable books exclude identified CUSIP, share-basis and new-security events from trades. Exit-size bands describe prior book weight, not the manager's intent.
Where the data comes from
SEC 13F quarter-end holdings for Q1 2026 and Q2 2026; these delayed disclosures omit shorts and many other assets.
Current source filed .
Technical details
Reported dollar change: -238320000 USD. Current reported shares: not recorded. Prior shares on current basis: 6000000.
- CRNX
CRINETICS PHARMACEUTICALS IN
−$155.7M
Sold out, was 6.7% of the book
Your stake and evidence for CRNX
What it means for you
This public view does not read your holdings or watchlist; open the member view to check your stake.
Use this to decide what to research, rather than as an instruction to copy a trade.
What happened
The position reported in Q1 2026 is absent from the comparable Q2 2026 book.
Displayed change: −$155.7M. This was 6.7% of the prior book.
Why it can matter
A change between quarter-end disclosures can prompt a question about the manager's exposure. It does not reveal the trade date, the execution price or why the position changed; a full exit is not proof of a bearish decision.
How we got this
A full exit is shown as the negative of its prior reported value, not sale proceeds or a value at today's price.
Comparable books exclude identified CUSIP, share-basis and new-security events from trades. Exit-size bands describe prior book weight, not the manager's intent.
Where the data comes from
SEC 13F quarter-end holdings for Q1 2026 and Q2 2026; these delayed disclosures omit shorts and many other assets.
Current source filed .
Technical details
Reported dollar change: -155745000 USD. Current reported shares: not recorded. Prior shares on current basis: 4288120.
- XNCR
XENCOR INC
−$26.3M
Sold out, was 1.1% of the book
Your stake and evidence for XNCR
What it means for you
This public view does not read your holdings or watchlist; open the member view to check your stake.
Use this to decide what to research, rather than as an instruction to copy a trade.
What happened
The position reported in Q1 2026 is absent from the comparable Q2 2026 book.
Displayed change: −$26.3M. This was 1.1% of the prior book.
Why it can matter
A change between quarter-end disclosures can prompt a question about the manager's exposure. It does not reveal the trade date, the execution price or why the position changed; a full exit is not proof of a bearish decision.
How we got this
A full exit is shown as the negative of its prior reported value, not sale proceeds or a value at today's price.
Comparable books exclude identified CUSIP, share-basis and new-security events from trades. Exit-size bands describe prior book weight, not the manager's intent.
Where the data comes from
SEC 13F quarter-end holdings for Q1 2026 and Q2 2026; these delayed disclosures omit shorts and many other assets.
Current source filed .
Technical details
Reported dollar change: -26327000 USD. Current reported shares: not recorded. Prior shares on current basis: 2183000.
- RLAY
RELAY THERAPEUTICS INC
−$22.6M
-63.4% shares
Your stake and evidence for RLAY
What it means for you
This public view does not read your holdings or watchlist; open the member view to check your stake.
Use this to decide what to research, rather than as an instruction to copy a trade.
What happened
Reported shares decreased between Q1 2026 and Q2 2026.
Displayed change: −$22.6M. The current book reports 697,948 shares.
Why it can matter
A change between quarter-end disclosures can prompt a question about the manager's exposure. It does not reveal the trade date, the execution price or why the position changed; a full exit is not proof of a bearish decision.
How we got this
For an added or trimmed position, subtract split-adjusted prior shares from current shares, then multiply by the current book's reported value per share; this is not the execution price.
697,948 current shares − 1,904,762 prior shares on the same basis = -1,206,814 shares.
Comparable books exclude identified CUSIP, share-basis and new-security events from trades. Exit-size bands describe prior book weight, not the manager's intent.
Where the data comes from
SEC 13F quarter-end holdings for Q1 2026 and Q2 2026; these delayed disclosures omit shorts and many other assets.
Current source filed .
Technical details
Reported dollar change: -22579489.801672906 USD. Current reported shares: 697948. Prior shares on current basis: 1904762.
What was sold out, by size
- 5 real positions, 0.25% of the book or more
- 2 small, between 0.015% and 0.25%
Not counted as trades: TRAX (newly listed or spun off), ODTX (newly listed or spun off), ELOXX PHARMACEUTICALS INC (newly listed or spun off).
All of this comes from the filer's public SEC filings. A 13-F shows long positions in US-listed securities at quarter end and can leave out short positions, cash and non-US holdings, so it is not the whole portfolio. This is filing data, not investment advice.