Reported positions
Quarter-end holdings as filed
Explore the full published position list and its source filing. This record excludes the manager’s cash, shorts and non-13(f) assets.
EcoR1 Capital, LLC
- sum of disclosed values for 2026-03-31; 0 positions carry a NULL value and are excluded from the sum, surfaced here rather than folded away
- $2.4B
- ALL retained default holdings for this (filer, period), including NULL-value ones
- 30
- positions with no comparable holding in the prior quarter (kind new), 2026-03-31
- 11
- positions absent from this quarter's filing after being held last quarter (kind exit), 2026-03-31 — inferred from absence, not a sale record
- 11
A quarter-end snapshot. Filed up to 45 days later, so this page is not current holdings and never a complete portfolio. what a 13F is — and is not ↓ methodology §13F ↗
Position changes — into 2026-03-31
by shares · Δ value · filing link · how changes are classified §Period
position matched across quarters by exact reported CUSIP over a registry gap — producer-reconciled identity, never a name match identity_reconciled_by_cusip | the reported share count is unchanged across the pair; this build's data classified the change from its reported value; builds from 2026-09-10 on read it as NO CHANGE classified_by_value · EXIT = absent this quarter: disposed, delisted, under confidential treatment, or reported instead by an affiliated manager — the filing does not say which · change not classifiable: value undisclosed on one side of the quarter pair, or neither shares nor value can classify it · NO CHANGE = the share count is identical in both quarters; the value moved only with price, so the row is mark-to-market and never an ADD or a TRIM (NEW / ADD / TRIM / EXIT / NO CHANGE) · NO PRIOR = this filer has no comparable holdings list for the previous quarter on record — a first filing under this registration, or a quarter reported inside an affiliated manager's filing — so the position is not called a new stake | derived by Public Filings from the published aggregate; NULL means the source did not disclose a usable value — never zero | Prev value | Curr value | Prev shares | Curr shares | |
|---|---|---|---|---|---|---|---|
position key pos:17964 · issuer key cusip6:152309 SPONSORED ADS | ADD | +$160M | +2,885,000 | $77.9M | $238M | 3,115,000 | 6,000,000 |
position key pos:10215 · issuer key iss:62 COM ADDED | NEW | +$86.3M | +4,824,469 | $0 | $86.3M | — | 4,824,469 |
position key pos:11549 · issuer key iss:429 COM | ADD | +$42.5M | +330,000 | $32.1M | $74.6M | 772,000 | 1,102,000 |
position key sid:sec:prov:a6062b7020b087adc81a7c6d38642d39 · issuer key cusip6:29772L COM | ADD | +$19.3M | +141,394 | $34.3M | $53.6M | 2,030,544 | 2,171,938 |
position key sid:sec:prov:bc17a1945987420f684d9107b41fd336 · issuer key cusip6:98401F COM | TRIM | −$23.4M | −1,068,112 | $49.8M | $26.3M | 3,251,112 | 2,183,000 |
position key sid:sec:prov:1910147dd0682cb840152de5838d5484 · issuer key cusip6:55287L COM | TRIM | −$43.8M | −1,346,604 | $67.0M | $23.2M | 2,123,604 | 777,000 |
position key pos:12369 · issuer key iss:1540 COM | NEW | +$19.0M | +1,904,762 | $0 | $19.0M | — | 1,904,762 |
position key pos:17964 · issuer key cusip6:152309 SPONSORED ADS CALL | NEW | +$16.3M | +410,800 | $0 | $16.3M | — | 410,800 |
position key pos:11747 · issuer key iss:680 COM | NEW | +$14.6M | +900,000 | $0 | $14.6M | — | 900,000 |
position key sid:sec:prov:c25b5f9e8c5b977c71e48306567bac3d · issuer key cusip6:282564 COM ADDED | NEW | +$7.8M | +732,606 | $0 | $7.8M | — | 732,606 |
position key pos:12518 · issuer key iss:1547 COM | NEW | +$7.7M | +1,000,000 | $0 | $7.7M | — | 1,000,000 |
position key sid:sec:prov:37f8d7b8f8c97e91dcf78ef12d0dd5a9 · issuer key cusip6:G9TY5A CLASS A ORD SHS | NEW | +$7.0M | +1,179,715 | $0 | $7.0M | — | 1,179,715 |
position key sid:sec:prov:7715098c333bbe982e541f4b97bf5506 · issuer key cusip6:71722W COM | NEW | +$6.9M | +625,000 | $0 | $6.9M | — | 625,000 |
position key sid:sec:prov:3af9f2163c854ed07645fe0c708030c1 · issuer key cusip6:589492 SPON ADS | ADD | +$1.1M | +5,512,389 | $3.3M | $4.4M | 7,856,466 | 13,368,855 |
position key sid:sec:prov:3fee4169345e05a49cf14bcc2babfc71 · issuer key cusip6:86150R COM | NEW | +$3.3M | +100,000 | $0 | $3.3M | — | 100,000 |
position key sid:sec:prov:52a86e73e5ebd8fb9104a71a48f9c42d · issuer key cusip6:74065P COM | NEW | +$3.2M | +947,049 | $0 | $3.2M | — | 947,049 |
position key sid:sec:prov:1da079c25df03f1597bca8fccb831a3d · issuer key cusip6:451033 COM NEW | TRIM | −$1.3M | −645,000 | $4.3M | $3.0M | 2,228,000 | 1,583,000 |
position key pos:16387 · issuer key iss:2129 CL A ORD SHS ADDED | NEW | +$2.0M | +200,000 | $0 | $2.0M | — | 200,000 |
position key sid:sec:prov:ccfa94a85000a92d8fff3645c8d29dfb · issuer key cusip6:046513 COM NEW | TRIM | −$9.9M | −473,590 | $10.4M | $471K | 573,183 | 99,593 |
position key pos:11549 · issuer key iss:429 COM CALL | EXIT‡e | −$12.2M | −292,800 | $12.2M | $0 | 292,800 | — |
| pos:11660 | EXIT‡e | −$20.8M | −450,000 | $20.8M | $0 | 450,000 | — |
| pos:14355 | EXIT‡e | −$61.3M | −2,855,590 | $61.3M | $0 | 2,855,590 | — |
| pos:15574 | EXIT‡e | −$8.6M | −963,333 | $8.6M | $0 | 963,333 | — |
| sid:sec:prov:049c2d4f45ba193716199e4b705e328c | EXIT‡e | −$15.7M | −4,002,847 | $15.7M | $0 | 4,002,847 | — |
| sid:sec:prov:287679ae59495e28d5c5c22eea9bb86e | EXIT‡e | −$17.0M | −2,625,000 | $17.0M | $0 | 2,625,000 | — |
| sid:sec:prov:3c1bdde45f78766466db92da273259f5 | EXIT‡e | −$4.5M | −675,000 | $4.5M | $0 | 675,000 | — |
| sid:sec:prov:45198704ea9cc377c213d31d32f48360 | EXIT‡e | −$2.0M | −325,000 | $2.0M | $0 | 325,000 | — |
| sid:sec:prov:862b191ccb923fc424f39385b48ce4f8 | EXIT‡e | −$23.3M | −334,380 | $23.3M | $0 | 334,380 | — |
| sid:sec:prov:9318e51aacd9a6ead589f2a198b9f099 | EXIT‡e | −$9.4M | −1,660,000 | $9.4M | $0 | 1,660,000 | — |
position key sid:sec:prov:bc17a1945987420f684d9107b41fd336 · issuer key cusip6:98401F COM CALL | EXIT‡e | −$1.0M | −67,500 | $1.0M | $0 | 67,500 | — |
Flags: no row carries a flag.
1–20 of the 30 changes on this page
Mark-to-market only (no share change) · 11
Positions whose share count is identical in both quarters; the value changed with price, not with a decision.
position matched across quarters by exact reported CUSIP over a registry gap — producer-reconciled identity, never a name match identity_reconciled_by_cusip | the reported share count is unchanged across the pair; this build's data classified the change from its reported value; builds from 2026-09-10 on read it as NO CHANGE classified_by_value · EXIT = absent this quarter: disposed, delisted, under confidential treatment, or reported instead by an affiliated manager — the filing does not say which · change not classifiable: value undisclosed on one side of the quarter pair, or neither shares nor value can classify it · NO CHANGE = the share count is identical in both quarters; the value moved only with price, so the row is mark-to-market and never an ADD or a TRIM (NEW / ADD / TRIM / EXIT / NO CHANGE) · NO PRIOR = this filer has no comparable holdings list for the previous quarter on record — a first filing under this registration, or a quarter reported inside an affiliated manager's filing — so the position is not called a new stake | derived by Public Filings from the published aggregate; NULL means the source did not disclose a usable value — never zero | Prev value | Curr value | Prev shares | Curr shares | |
|---|---|---|---|---|---|---|---|
position key sid:sec:prov:cc436d9af4067ff4382c62284d4ff9e5 · issuer key cusip6:98985Y COM | NO CHANGE | −$29.6M | 0 | $605M | $575M | 22,970,388 | 22,970,388 |
position key pos:17269 · issuer key iss:128 COM | NO CHANGE | +$55.0M | 0 | $382M | $437M | 7,880,094 | 7,880,094 |
position key pos:14655 · issuer key iss:2143 SHS USD | NO CHANGE | +$32.5M | 0 | $290M | $323M | 1,706,469 | 1,706,469 |
position key pos:14981 · issuer key iss:535 COM | NO CHANGE | −$43.9M | 0 | $200M | $156M | 4,288,120 | 4,288,120 |
position key pos:10700 · issuer key iss:1374 COM | NO CHANGE | +$30.2M | 0 | $55.0M | $85.2M | 6,728,116 | 6,728,116 |
position key sid:sec:prov:68e0167561be56366c5e5fc78bb6403e · issuer key cusip6:H17182 NAMEN AKT | NO CHANGE | −$6.8M | 0 | $72.9M | $66.1M | 1,389,276 | 1,389,276 |
position key sid:sec:prov:856d00daa392df84ca63299ef03992d5 · issuer key cusip6:36315X SPON ADR | NO CHANGE | −$4.5M | 0 | $54.5M | $50.0M | 1,667,119 | 1,667,119 |
position key sid:sec:prov:2436d0e4b9db5d946b26deb83a717d5e · issuer key cusip6:64135M COM | NO CHANGE | −$559K | 0 | $26.2M | $25.6M | 1,271,342 | 1,271,342 |
position key pos:12072 · issuer key iss:310 COM NEW | NO CHANGE | −$10.1M | 0 | $35.3M | $25.3M | 2,823,126 | 2,823,126 |
position key sid:sec:prov:f23e65e3d61dbc0d9c26fbeb71e72b85 · issuer key cusip6:98937L COM | NO CHANGE | −$13.2M | 0 | $28.7M | $15.4M | 789,500 | 789,500 |
position key sid:sec:prov:c4f97db1890f36f80c7a359d19822318 · issuer key cusip6:86889P *W EXP 08/01/203 | NO CHANGE | +$29.0K | 0 | $100K | $129K | 4,444 | 4,444 |
Flags: no row carries a flag.
Newest filing in this build: 2026-07-31. Per-row filing dates are on each receipt.
Changes compare every position with a security identifier, new and exited included; holdings without one are counted, not compared. methodology §13F ↗
Reported positions — 2026-03-31
1–29 of 29 issuers · $2.4B disclosed value over 30 rows · 0 undisclosed-value rowsViewThis build carries one quarter for this manager: 2026-03-31. Notable managers carry four published quarters, others two.
| This list carries reported issuer names and security identities, without a dated ticker mapping. Symbols are not inferred from names. | a position composed from a base filing plus NEW-HOLDINGS amendments keeps every source row here; the composition's latest filed date is the one shown served from this build's published holdings (derived from the filer's own reported rows); every row resolves to its filing | Share of total reported value, calculated only when the full position list has disclosed values. This is 13F long value, not total assets. | value undisclosed on the filing: retained and counted, excluded from sums, never shown as $0 | Shares | Wt | ||||||
|---|---|---|---|---|---|---|---|---|---|---|---|
| — | ZYMEWORKS INC · COM CUSIP 98985Y108 quarter ended 2026-03-31 filed filed 2026-05-15 +45d ticker not yet mapped | $575M | 22,970,388 | 24.4% | |||||||
| verified against the SEC company list on 2026-09-10 — a reviewed mapping row for this filed issuer name and class (never inferred) | ANAPTYSBIO INC · COM CUSIP — quarter ended 2026-03-31 filed filed 2026-05-15 +45d | $437M | 7,880,094 | 18.5% | |||||||
| verified against the SEC company list on 2026-09-10 — a reviewed mapping row for this filed issuer name and class (never inferred) | JAZZ PHARMACEUTICALS PLC · SHS USD CUSIP — quarter ended 2026-03-31 filed filed 2026-05-15 +45d | $323M | 1,706,469 | 13.7% | |||||||
| — | CENTESSA PHARMACEUTICALS PLC2 positions · 2 reported rows
| $255M | 6,410,800 | 10.8% | |||||||
| verified against the SEC company list on 2026-09-10 — a reviewed mapping row for this filed issuer name and class (never inferred) | CRINETICS PHARMACEUTICALS IN · COM CUSIP — quarter ended 2026-03-31 filed filed 2026-05-15 +45d | $156M | 4,288,120 | 6.6% | |||||||
| — | AKTIS ONCOLOGY INC · COM ADDED CUSIP — quarter ended 2026-03-31 filed filed 2026-05-15 +45d ticker not yet mapped | $86.3M | 4,824,469 | 3.7% | |||||||
| verified against the SEC company list on 2026-09-10 — a reviewed mapping row for this filed issuer name and class (never inferred) | ORIC PHARMACEUTICALS INC · COM CUSIP — quarter ended 2026-03-31 filed filed 2026-05-15 +45d | $85.2M | 6,728,116 | 3.6% | |||||||
| verified against the SEC company list on 2026-09-10 — a reviewed mapping row for this filed issuer name and class (never inferred) | CG ONCOLOGY INC · COM CUSIP — quarter ended 2026-03-31 filed filed 2026-05-15 +45d | $74.6M | 1,102,000 | 3.2% | |||||||
| — | CRISPR THERAPEUTICS AG · NAMEN AKT CUSIP H17182108 quarter ended 2026-03-31 filed filed 2026-05-15 +45d ticker not yet mapped | $66.1M | 1,389,276 | 2.8% | |||||||
| — | ETON PHARMACEUTICALS INC · COM CUSIP 29772L108 quarter ended 2026-03-31 filed filed 2026-05-15 +45d ticker not yet mapped | $53.6M | 2,171,938 | 2.3% | |||||||
| — | GALAPAGOS NV · SPON ADR CUSIP 36315X101 quarter ended 2026-03-31 filed filed 2026-05-15 +45d ticker not yet mapped | $50.0M | 1,667,119 | 2.1% | |||||||
| — | XENCOR INC · COM CUSIP 98401F105 quarter ended 2026-03-31 filed filed 2026-05-15 +45d ticker not yet mapped | $26.3M | 2,183,000 | 1.1% | |||||||
| — | NEUROGENE INC · COM CUSIP 64135M105 quarter ended 2026-03-31 filed filed 2026-05-15 +45d ticker not yet mapped | $25.6M | 1,271,342 | 1.1% | |||||||
| verified against the SEC company list on 2026-09-10 — a reviewed mapping row for this filed issuer name and class (never inferred) | BRIDGEBIO ONCOLOGY THERAPEUT · COM NEW CUSIP — quarter ended 2026-03-31 filed filed 2026-05-15 +45d | $25.3M | 2,823,126 | 1.1% | |||||||
| — | MBX BIOSCIENCES INC · COM CUSIP 55287L101 quarter ended 2026-03-31 filed filed 2026-05-15 +45d ticker not yet mapped | $23.2M | 777,000 | 1.0% | |||||||
| verified against the SEC company list on 2026-09-10 — a reviewed mapping row for this filed issuer name and class (never inferred) | RELAY THERAPEUTICS INC · COM CUSIP — quarter ended 2026-03-31 filed filed 2026-05-15 +45d | $19.0M | 1,904,762 | 0.8% | |||||||
| — | ZENAS BIOPHARMA INC · COM CUSIP 98937L105 quarter ended 2026-03-31 filed filed 2026-05-15 +45d ticker not yet mapped | $15.4M | 789,500 | 0.7% | |||||||
| verified against the SEC company list on 2026-09-10 — a reviewed mapping row for this filed issuer name and class (never inferred) | ERASCA INC · COM CUSIP — quarter ended 2026-03-31 filed filed 2026-05-15 +45d | $14.6M | 900,000 | 0.6% | |||||||
| — | EIKON THERAPEUTICS INC · COM ADDED CUSIP 282564103 quarter ended 2026-03-31 filed filed 2026-05-15 +45d ticker not yet mapped | $7.8M | 732,606 | 0.3% | |||||||
| verified against the SEC company list on 2026-09-10 — a reviewed mapping row for this filed issuer name and class (never inferred) | REPLIMUNE GROUP INC · COM CUSIP — quarter ended 2026-03-31 filed filed 2026-05-15 +45d | $7.7M | 1,000,000 | 0.3% | |||||||
| — | ZURA BIO LTD · CLASS A ORD SHS CUSIP G9TY5A101 quarter ended 2026-03-31 filed filed 2026-05-15 +45d ticker not yet mapped | $7.0M | 1,179,715 | 0.3% | |||||||
| — | PHATHOM PHARMACEUTICALS INC · COM CUSIP 71722W107 quarter ended 2026-03-31 filed filed 2026-05-15 +45d ticker not yet mapped | $6.9M | 625,000 | 0.3% | |||||||
| — | MEREO BIOPHARMA GROUP PLC · SPON ADS CUSIP 589492107 quarter ended 2026-03-31 filed filed 2026-05-15 +45d ticker not yet mapped | $4.4M | 13,368,855 | 0.2% | |||||||
| — | STOKE THERAPEUTICS INC · COM CUSIP 86150R107 quarter ended 2026-03-31 filed filed 2026-05-15 +45d ticker not yet mapped | $3.3M | 100,000 | 0.1% | |||||||
| — | PRELUDE THERAPEUTICS INC · COM CUSIP 74065P101 quarter ended 2026-03-31 filed filed 2026-05-15 +45d ticker not yet mapped | $3.2M | 947,049 | 0.1% | |||||||
| — | IBIO INC · COM NEW CUSIP 451033708 quarter ended 2026-03-31 filed filed 2026-05-15 +45d ticker not yet mapped | $3.0M | 1,583,000 | 0.1% | |||||||
| — | HELIX ACQUISITION CORP III USD · CL A ORD SHS ADDED CUSIP — quarter ended 2026-03-31 filed filed 2026-05-15 +45d ticker not yet mapped | $2.0M | 200,000 | 0.1% | |||||||
| — | ATARA BIOTHERAPEUTICS INC · COM NEW CUSIP 046513206 quarter ended 2026-03-31 filed filed 2026-05-15 +45d ticker not yet mapped | $471K | 99,593 | 0.0% | |||||||
| — | SURROZEN INC · *W EXP 08/01/203 CUSIP 86889P117 quarter ended 2026-03-31 filed filed 2026-05-15 +45d ticker not yet mapped | $129K | 4,444 | 0.0% |
1–20 of 29 issuers
Change kind and share change are in Position changes above; Congress overlap is planned.
1–29 of 29 issuers · page 1 of 1
One line per issuer, largest first; a row with no issuer key stands on its own line. Open a line for its rows as this filer reported them. The list holds every row this filer reported for the quarter. Issuer totals on the holders pages count each manager's own report once; that never removes a row here. how positions are grouped ↗
Book shape
2026-03-31 · concentration · vs tracked median · tick = median- Top-25 concentration
- 99.6%above median 80.0%
- Concentration index
- 1,334 bpsabove median 446 bps
- Positions with value
- 30 / 30median book 97.5 positions
Concentration uses reported 13F long value, not total assets. The index is withheld when any position lacks a value. Medians are over the 8,748 tracked filers with a 2026-03-31 book; the index median over the 8,662 with a complete book.
holdings whose <value> did not parse — retained and counted, never zero-filled: 0 · : 99.6% · integer Herfindahl–Hirschman index in basis points over disclosed position values: 1,334 · QoQ moves: 41
Filing history
AVAILABLE QUARTERS| Period | Source |
|---|---|
| 2026-03-31 | EDGAR ↗ |
PLANNED sector rotation · Congress overlap · signals for this filer
Complete source filings on SEC EDGAR
The complete filing on EDGAR.
The position list above is served from the published Public Filings build, each position as this filer reported it; where the page cannot embed every reported row, the list says how many it leaves out. This block is provenance, not a substitute: the filing itself is the record, and it is one click away. Public Filings decided on 2026-08-01 to serve this list from its published build; filings newer than this build are on EDGAR.
Open EcoR1 Capital, LLC's 13F filings on SEC EDGAR ↗Notes on this data
Share changes
Compare consecutive quarters
Position changes retain the producer’s classification and comparability flags. Share counts and reported values describe different changes.
Coverage
A snapshot, not current holdings
Use the quarter selector to inspect available periods. Unknown values stay unknown and each table states its coverage.
A 13F is a quarterly, long-only snapshot filed up to 45 days late — not current holdings. what a 13F covers ↗
13F reports cover LONG positions in Section 13(f) securities (US exchange-traded equities plus reportable options, warrants, certain convertibles) held by managers with at least $100M in such securities — so managers below that threshold are absent entirely. No short positions, no cash, no non-13(f) assets — not a full portfolio, and not a census of institutional ownership.
Positions are quarter-end snapshots filed up to 45 days late — not current holdings. A position may have been changed or closed before you ever see it, and is older still by however long ago that quarter ended.
Values are the manager's stated market value at quarter-end in era-dependent units (whole dollars for form versions effective 2023-01-03 onward, thousands before), normalized here to whole dollars with unit_basis carried on every record.
Affiliated managers may report the same position (otherManager), so one position can appear under more than one filer.
Positions under confidential treatment may be omitted until a later amendment discloses them.
These are disclosures, not investment advice (ARCHITECTURE.md §5.2 / M2-CONTRACT §5).