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
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 ↗
Period
$2.4B
reported valuesum 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
30
positionsALL retained default holdings for this (filer, period), including NULL-value ones
11
new stakespositions with no comparable holding in the prior quarter (kind new), 2026-03-31
11
exitspositions absent from this quarter's filing after being held last quarter (kind exit), 2026-03-31 — inferred from absence, not a sale record
Position changes — into 2026-03-31
by shares · Δ value · filing link · how changes are classified §Positionposition matched across quarters by exact reported CUSIP over a registry gap — producer-reconciled identity, never a name match identity_reconciled_by_cusip | Changethe reported share count is unchanged across the pair, so the position reads as held rather than as a buy or a sell; only builds before this release inferred a direction from the reported value instead 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 (Add / New / 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 | Δ valuederived by Public Filings from the published aggregate; NULL means the source did not disclose a usable value — never zero | Δ shares | Prev value | Curr value | Prev shares | Curr shares | Flags |
|---|---|---|---|---|---|---|---|---|
CENTESSA PHARMACEUTICALS PLC SPONSORED ADSposition key pos:18882 · issuer key cusip6:152309 | add | +$160M | +2,885,000 | $77.9M | $238M | 3,115,000 | 6,000,000 | |
AKTIS ONCOLOGY INC COM ADDEDposition key pos:11057 · issuer key iss:119 | new | +$86.3M | +4,824,469 | $0 | $86.3M | — | 4,824,469 | |
CG ONCOLOGY INC COMposition key pos:12402 · issuer key iss:558 | add | +$42.5M | +330,000 | $32.1M | $74.6M | 772,000 | 1,102,000 | |
ETON PHARMACEUTICALS INC COMposition key sid:sec:prov:a6062b7020b087adc81a7c6d38642d39 · issuer key cusip6:29772L | add | +$19.3M | +141,394 | $34.3M | $53.6M | 2,030,544 | 2,171,938 | |
XENCOR INC COMposition key sid:sec:prov:bc17a1945987420f684d9107b41fd336 · issuer key cusip6:98401F | trim | −$23.4M | −1,068,112 | $49.8M | $26.3M | 3,251,112 | 2,183,000 | |
MBX BIOSCIENCES INC COMposition key sid:sec:prov:1910147dd0682cb840152de5838d5484 · issuer key cusip6:55287L | trim | −$43.8M | −1,346,604 | $67.0M | $23.2M | 2,123,604 | 777,000 | |
RELAY THERAPEUTICS INC COMposition key pos:13232 · issuer key iss:1829 | new | +$19.0M | +1,904,762 | $0 | $19.0M | — | 1,904,762 | |
CENTESSA PHARMACEUTICALS PLC SPONSORED ADSposition key pos:18882 · issuer key cusip6:152309 CALL | new | +$16.3M | +410,800 | $0 | $16.3M | — | 410,800 | |
ERASCA INC COMposition key pos:12600 · issuer key iss:846 | new | +$14.6M | +900,000 | $0 | $14.6M | — | 900,000 | |
EIKON THERAPEUTICS INC COM ADDEDposition key sid:sec:prov:c25b5f9e8c5b977c71e48306567bac3d · issuer key cusip6:282564 | new | +$7.8M | +732,606 | $0 | $7.8M | — | 732,606 | |
REPLIMUNE GROUP INC COMposition key pos:13385 · issuer key iss:1836 | new | +$7.7M | +1,000,000 | $0 | $7.7M | — | 1,000,000 | |
ZURA BIO LTD CLASS A ORD SHSposition key sid:sec:prov:37f8d7b8f8c97e91dcf78ef12d0dd5a9 · issuer key cusip6:G9TY5A | new | +$7.0M | +1,179,715 | $0 | $7.0M | — | 1,179,715 | |
PHATHOM PHARMACEUTICALS INC COMposition key sid:sec:prov:7715098c333bbe982e541f4b97bf5506 · issuer key cusip6:71722W | new | +$6.9M | +625,000 | $0 | $6.9M | — | 625,000 | |
MEREO BIOPHARMA GROUP PLC SPON ADSposition key sid:sec:prov:3af9f2163c854ed07645fe0c708030c1 · issuer key cusip6:589492 | add | +$1.1M | +5,512,389 | $3.3M | $4.4M | 7,856,466 | 13,368,855 | |
STOKE THERAPEUTICS INC COMposition key sid:sec:prov:3fee4169345e05a49cf14bcc2babfc71 · issuer key cusip6:86150R | new | +$3.3M | +100,000 | $0 | $3.3M | — | 100,000 | |
PRELUDE THERAPEUTICS INC COMposition key sid:sec:prov:52a86e73e5ebd8fb9104a71a48f9c42d · issuer key cusip6:74065P | new | +$3.2M | +947,049 | $0 | $3.2M | — | 947,049 | |
IBIO INC COM NEWposition key sid:sec:prov:1da079c25df03f1597bca8fccb831a3d · issuer key cusip6:451033 | trim | −$1.3M | −645,000 | $4.3M | $3.0M | 2,228,000 | 1,583,000 | |
HELIX ACQUISITION CORP III USD CL A ORD SHS ADDEDposition key pos:17288 · issuer key iss:2530 | new | +$2.0M | +200,000 | $0 | $2.0M | — | 200,000 | |
ATARA BIOTHERAPEUTICS INC COM NEWposition key sid:sec:prov:ccfa94a85000a92d8fff3645c8d29dfb · issuer key cusip6:046513 | trim | −$9.9M | −473,590 | $10.4M | $471K | 573,183 | 99,593 | |
CG ONCOLOGY INC COMposition key pos:12402 · issuer key iss:558 CALL | exit‡e | −$12.2M | −292,800 | $12.2M | $0 | 292,800 | — | |
| pos:12513 | exit‡e | −$20.8M | −450,000 | $20.8M | $0 | 450,000 | — | |
| pos:15236 | exit‡e | −$61.3M | −2,855,590 | $61.3M | $0 | 2,855,590 | — | |
| pos:16467 | 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 | — | |
XENCOR INC COMposition key sid:sec:prov:bc17a1945987420f684d9107b41fd336 · issuer key cusip6:98401F CALL | exit‡e | −$1.0M | −67,500 | $1.0M | $0 | 67,500 | — |
10 more changes below.
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.
Positionposition matched across quarters by exact reported CUSIP over a registry gap — producer-reconciled identity, never a name match identity_reconciled_by_cusip | Changethe reported share count is unchanged across the pair, so the position reads as held rather than as a buy or a sell; only builds before this release inferred a direction from the reported value instead 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 (Add / New / 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 | Δ valuederived by Public Filings from the published aggregate; NULL means the source did not disclose a usable value — never zero | Δ shares | Prev value | Curr value | Prev shares | Curr shares | Flags |
|---|---|---|---|---|---|---|---|---|
ZYMEWORKS INC COMposition key sid:sec:prov:cc436d9af4067ff4382c62284d4ff9e5 · issuer key cusip6:98985Y | no change | −$29.6M | 0 | $605M | $575M | 22,970,388 | 22,970,388 | |
ANAPTYSBIO INC COMposition key pos:18179 · issuer key iss:200 | no change | +$55.0M | 0 | $382M | $437M | 7,880,094 | 7,880,094 | |
JAZZ PHARMACEUTICALS PLC SHS USDposition key pos:15540 · issuer key iss:2545 | no change | +$32.5M | 0 | $290M | $323M | 1,706,469 | 1,706,469 | |
CRINETICS PHARMACEUTICALS IN COMposition key pos:15866 · issuer key iss:682 | no change | −$43.9M | 0 | $200M | $156M | 4,288,120 | 4,288,120 | |
ORIC PHARMACEUTICALS INC COMposition key pos:11546 · issuer key iss:1634 | no change | +$30.2M | 0 | $55.0M | $85.2M | 6,728,116 | 6,728,116 | |
CRISPR THERAPEUTICS AG NAMEN AKTposition key sid:sec:prov:68e0167561be56366c5e5fc78bb6403e · issuer key cusip6:H17182 | no change | −$6.8M | 0 | $72.9M | $66.1M | 1,389,276 | 1,389,276 | |
GALAPAGOS NV SPON ADRposition key sid:sec:prov:856d00daa392df84ca63299ef03992d5 · issuer key cusip6:36315X | no change | −$4.5M | 0 | $54.5M | $50.0M | 1,667,119 | 1,667,119 | |
NEUROGENE INC COMposition key sid:sec:prov:2436d0e4b9db5d946b26deb83a717d5e · issuer key cusip6:64135M | no change | −$559K | 0 | $26.2M | $25.6M | 1,271,342 | 1,271,342 | |
BRIDGEBIO ONCOLOGY THERAPEUT COM NEWposition key pos:12931 · issuer key iss:426 | no change | −$10.1M | 0 | $35.3M | $25.3M | 2,823,126 | 2,823,126 | |
ZENAS BIOPHARMA INC COMposition key sid:sec:prov:f23e65e3d61dbc0d9c26fbeb71e72b85 · issuer key cusip6:98937L | no change | −$13.2M | 0 | $28.7M | $15.4M | 789,500 | 789,500 | |
SURROZEN INC *W EXP 08/01/203position key sid:sec:prov:c4f97db1890f36f80c7a359d19822318 · issuer key cusip6:86889P | no change | +$29.0K | 0 | $100K | $129K | 4,444 | 4,444 |
Quarter ended 2026-03-31Newest filing in this build: 2026-07-31. Per-row filing dates are on each receipt.
Changes derive from the aggregate's top-25 slices and keyable positions only; unkeyable holdings are counted in the registry, not differenced. methodology §13F ↗
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.
null-value positions: 0holdings whose <value> did not parse — retained and counted, never zero-filled · top-N share ·§: 99.6% · HHI (bps) ·§: 1,334integer Herfindahl–Hirschman index in basis points over disclosed position values · 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 — every position this filer reported for the selected quarter, as it reported it. This block is provenance, not a substitute: the filing itself is the record, and it is one click away. Serving this list is M2-CONTRACT §3, amended 2026-08-02; §3.1 keeps live EDGAR for filings newer than this build.
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.
ViewPrior quarter not yet availableThis build carries one quarter for this manager: 2026-03-31. Notable managers carry four published quarters, others two.
Reported positions — 2026-03-31
1–29 of 29 issuers · $2.4B disclosed value over 30 rows · 0 undisclosed-value rowsEvery row below carries ticker not yet mapped — stated once here rather than repeated on every row.
| KindClassification is not joined into this reported-position view. Use the changed-positions view to compare the two published quarters. | TickerThis list carries reported issuer names and security identities, without a dated ticker mapping. Symbols are not inferred from names. | Issuera 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 | WeightShare of total reported value, calculated only when the full position list has disclosed values. This is 13F long value, not total assets. | Valuevalue undisclosed on the filing: retained and counted, excluded from sums, never shown as $0 | Shares | Position changeShare change is available in the separate comparison view; it is not joined into this position list. | Wt | CongressThe congressional transaction join is unavailable in this build. |
|---|---|---|---|---|---|---|---|---|
| — | — | ZYMEWORKS INC ZYMEWORKS INC · COM CUSIP 98985Y108 quarter ended 2026-03-31 filed filed 2026-05-15 +45d | $575M | 22,970,388 | — | 24.4% | — | |
| — | ANABverified against the SEC company list on 2026-09-10 — a reviewed mapping row for this filed issuer name and class (never inferred) | ANAPTYSBIO INC ANAPTYSBIO INC · COM CUSIP — quarter ended 2026-03-31 filed filed 2026-05-15 +45d | $437M | 7,880,094 | — | 18.5% | — | |
| — | JAZZverified 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 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 PLC | $255M | 6,410,800 | — | 10.8% | — | |
| — | CRNXverified 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 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 AKTIS ONCOLOGY INC · COM ADDED CUSIP — quarter ended 2026-03-31 filed filed 2026-05-15 +45d | $86.3M | 4,824,469 | — | 3.7% | — | |
| — | ORICverified 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 ORIC PHARMACEUTICALS INC · COM CUSIP — quarter ended 2026-03-31 filed filed 2026-05-15 +45d | $85.2M | 6,728,116 | — | 3.6% | — | |
| — | CGONverified 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 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 CRISPR THERAPEUTICS AG · NAMEN AKT CUSIP H17182108 quarter ended 2026-03-31 filed filed 2026-05-15 +45d | $66.1M | 1,389,276 | — | 2.8% | — | |
| — | — | ETON PHARMACEUTICALS INC ETON PHARMACEUTICALS INC · COM CUSIP 29772L108 quarter ended 2026-03-31 filed filed 2026-05-15 +45d | $53.6M | 2,171,938 | — | 2.3% | — | |
| — | — | GALAPAGOS NV GALAPAGOS NV · SPON ADR CUSIP 36315X101 quarter ended 2026-03-31 filed filed 2026-05-15 +45d | $50.0M | 1,667,119 | — | 2.1% | — | |
| — | — | XENCOR INC XENCOR INC · COM CUSIP 98401F105 quarter ended 2026-03-31 filed filed 2026-05-15 +45d | $26.3M | 2,183,000 | — | 1.1% | — | |
| — | — | NEUROGENE INC NEUROGENE INC · COM CUSIP 64135M105 quarter ended 2026-03-31 filed filed 2026-05-15 +45d | $25.6M | 1,271,342 | — | 1.1% | — | |
| — | BBOTverified 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 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 MBX BIOSCIENCES INC · COM CUSIP 55287L101 quarter ended 2026-03-31 filed filed 2026-05-15 +45d | $23.2M | 777,000 | — | 1.0% | — | |
| — | RLAYverified 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 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 ZENAS BIOPHARMA INC · COM CUSIP 98937L105 quarter ended 2026-03-31 filed filed 2026-05-15 +45d | $15.4M | 789,500 | — | 0.7% | — | |
| — | ERASverified against the SEC company list on 2026-09-10 — a reviewed mapping row for this filed issuer name and class (never inferred) | ERASCA INC ERASCA INC · COM CUSIP — quarter ended 2026-03-31 filed filed 2026-05-15 +45d | $14.6M | 900,000 | — | 0.6% | — | |
| — | — | EIKON THERAPEUTICS INC EIKON THERAPEUTICS INC · COM ADDED CUSIP 282564103 quarter ended 2026-03-31 filed filed 2026-05-15 +45d | $7.8M | 732,606 | — | 0.3% | — | |
| — | REPLverified 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 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 ZURA BIO LTD · CLASS A ORD SHS CUSIP G9TY5A101 quarter ended 2026-03-31 filed filed 2026-05-15 +45d | $7.0M | 1,179,715 | — | 0.3% | — | |
| — | — | PHATHOM PHARMACEUTICALS INC PHATHOM PHARMACEUTICALS INC · COM CUSIP 71722W107 quarter ended 2026-03-31 filed filed 2026-05-15 +45d | $6.9M | 625,000 | — | 0.3% | — | |
| — | — | MEREO BIOPHARMA GROUP PLC MEREO BIOPHARMA GROUP PLC · SPON ADS CUSIP 589492107 quarter ended 2026-03-31 filed filed 2026-05-15 +45d | $4.4M | 13,368,855 | — | 0.2% | — | |
| — | — | STOKE THERAPEUTICS INC STOKE THERAPEUTICS INC · COM CUSIP 86150R107 quarter ended 2026-03-31 filed filed 2026-05-15 +45d | $3.3M | 100,000 | — | 0.1% | — | |
| — | — | PRELUDE THERAPEUTICS INC PRELUDE THERAPEUTICS INC · COM CUSIP 74065P101 quarter ended 2026-03-31 filed filed 2026-05-15 +45d | $3.2M | 947,049 | — | 0.1% | — | |
| — | — | IBIO INC IBIO INC · COM NEW CUSIP 451033708 quarter ended 2026-03-31 filed filed 2026-05-15 +45d | $3.0M | 1,583,000 | — | 0.1% | — | |
| — | — | HELIX ACQUISITION CORP III USD HELIX ACQUISITION CORP III USD · CL A ORD SHS ADDED CUSIP — quarter ended 2026-03-31 filed filed 2026-05-15 +45d | $2.0M | 200,000 | — | 0.1% | — | |
| — | — | ATARA BIOTHERAPEUTICS INC ATARA BIOTHERAPEUTICS INC · COM NEW CUSIP 046513206 quarter ended 2026-03-31 filed filed 2026-05-15 +45d | $471K | 99,593 | — | 0.0% | — | |
| — | — | SURROZEN INC SURROZEN INC · *W EXP 08/01/203 CUSIP 86889P117 quarter ended 2026-03-31 filed filed 2026-05-15 +45d | $129K | 4,444 | — | 0.0% | — |
1–29 of 29 issuers · page 1 of 1
every row this filer reported for the quarter, as it reported it — cross-filer de-duplication is applied to issuer totals elsewhere and never deletes a row here
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).