Siren, L.L.C. — 13F Holdings & Portfolio
CIK 2005245 · latest 13F-HR filed 2026-08-13
Siren, L.L.C. manages $4.94B in 13F-reported U.S. long-equity assets across 119 reported positions as of its 2026-06-30 13F-HR filing. Its largest disclosed positions are SRRK (10.66%), KYMR (6.81%), ERAS (4.23%). Quarter over quarter (versus its 2026-03-31 filing) the fund opened 25 new positions and exited 10; 55 existing positions rose in reported value and 24 fell.
AUM is the long-equity portion reported on Form 13F-HR. Excludes short positions, cash, foreign holdings, and non-13F assets. For informational purposes only — not investment advice.
Long-equity book
Distinct positions
Filed 2026-08-13
vs 2026-03-31
Portfolio charts
Latest quarter's book, what changed, and how the portfolio has evolved across filings.
Portfolio map
Q2 26Box size = position value; colour = change in share count vs the prior quarter (green added, red trimmed, blue new). Rows split across managers or share classes are combined. Click a box for the stock.
Sector mix
% of 13F valueSectors from each company's SIC code; funds and ETFs grouped separately.
Biggest buys and sells
Q1 26 → Q2 26Estimated from the change in shares held × the quarter-end price, so price moves alone don't count as buying. New and exited positions are included.
13F assets and positions
4 quartersTotal reported 13F value (bars) and number of positions (line) each quarter. Value changes include market moves.
Top positions over time
reported valueThe eight largest current positions, valued at each quarter end.
Concentration
top 10 = 44.8%Cumulative share of the portfolio held in the largest N positions.
| Name | Title / Status | Ownership | Type |
|---|
Quarter-over-quarter changes
Changes in reported position value vs the prior 13F, so price moves count too, not just shares bought or sold.
Top Adds (vs prior quarter)
- Veradermics Inc$108.4M +114.1%
- Tango Therapeutics Inc$74.8M +63.2%
- Kymera Therapeutics Inc$71.2M +26.8%
- Rhythm Pharmaceuticals Inc$63.1M +99.9%
- Enliven Therapeutics Inc$60.8M +207.8%
Top Trims
- Structure Therapeutics Inc-$17.2M -26.8%
- Crinetics Pharmaceuticals Inc-$16.0M -23.1%
- Olema Pharmaceuticals Inc-$10.2M -14.3%
- Edgewise Therapeutics Inc-$10.2M -7.3%
- Dbv Technologies SA-$8.3M -21.5%
New Positions
- Parabilis Medicines Inc$81.9M
- Abivax SA$76.8M
- Hemab Therapeutics Holdings Inc$76.6M
- Relay Therapeutics Inc$68.3M
- Kailera Therapeutics Inc$48.8M
Exited Positions
- Centessa Pharmaceuticals PLC$41.8M
- enGene Holdings Inc$35.8M
- Fulcrum Therapeutics Inc$18.0M
- WAVE Life Sciences Ltd$17.8M
- Uniqure NV$16.4M
Siren, L.L.C. Holdings (2026-06-30)
Rows tagged Call or Put are options positions, not stock. Per SEC Form 13F-HR, Value shows the notional value of the underlying (shares covered × underlying price), not the option premium. Shares is the number of underlying shares covered (divide by 100 for contract count).
| # | Issuer | Symbol | CUSIP | Value | Weight | Shares | Type |
|---|---|---|---|---|---|---|---|
| 1 | Scholar Rock Holding Corp | SRRK | 80706P103 | $526.6M | 10.66% | 9,575,013 | SH |
| 2 | Kymera Therapeutics Inc | KYMR | 501575104 | $336.7M | 6.81% | 2,935,830 | SH |
| 3 | Erasca Inc | ERAS | 29479A108 | $208.8M | 4.23% | 11,397,781 | SH |
| 4 | Veradermics Inc | MANE | 922967104 | $203.5M | 4.12% | 1,655,374 | SH |
| 5 | Tango Therapeutics Inc | TNGX | 87583X109 | $193.2M | 3.91% | 6,179,364 | SH |
| 6 | Revolution Medicines Inc | RVMD | 76155X100 | $168.6M | 3.41% | 900,000 | SH |
| 7 | Bicara Therapeutics Inc | BCAX | 055477103 | $166.4M | 3.37% | 5,602,970 | SH |
| 8 | Arrowhead Pharmaceuticals Inc | ARWR | 04280A100 | $139.8M | 2.83% | 1,715,476 | SH |
| 9 | BeOne Medicines AG | ONC | 07725L102 | $132.5M | 2.68% | 465,000 | SH |
| 10 | Edgewise Therapeutics Inc | EWTX | 28036F105 | $129.4M | 2.62% | 3,184,629 | SH |
| 11 | Rhythm Pharmaceuticals Inc | RYTM | 76243J105 | $126.2M | 2.55% | 1,136,275 | SH |
| 12 | Lexicon Pharmaceuticals Inc | LXRX | 528872302 | $106.3M | 2.15% | 44,303,518 | SH |
| 13 | Enliven Therapeutics Inc | ELVN | 29337E102 | $90.1M | 1.82% | 1,774,411 | SH |
| 14 | Spyre Therapeutics Inc | SYRE | 00773J202 | $86.0M | 1.74% | 968,598 | SH |
| 15 | Parabilis Medicines Inc | PBLS | 698955101 | $81.9M | 1.66% | 2,992,259 | SH |
| 16 | Xenon Pharmaceuticals Inc | XENE | 98420N105 | $79.6M | 1.61% | 1,318,564 | SH |
| 17 | Solid Biosciences Inc | SLDB | 83422E204 | $76.8M | 1.55% | 7,690,405 | SH |
| 18 | Abivax SA | ABVX | 00370M103 | $76.8M | 1.55% | 576,000 | SH |
| 19 | Hemab Therapeutics Holdings Inc | COAG | 423494103 | $76.6M | 1.55% | 2,086,834 | SH |
| 20 | Cogent Biosciences Inc | COGT | 19240Q201 | $72.0M | 1.46% | 1,859,279 | SH |
| 21 | Relay Therapeutics Inc | RLAY | 75943R102 | $68.3M | 1.38% | 3,650,000 | SH |
| 22 | Taysha Gene Therapies Inc | TSHA | 877619106 | $67.1M | 1.36% | 9,846,579 | SH |
| 23 | Definium Therapeutics Inc | DFTX | 24477V105 | $66.8M | 1.35% | 1,419,493 | SH |
| 24 | Stoke Therapeutics Inc | STOK | 86150R107 | $65.3M | 1.32% | 1,995,347 | SH |
| 25 | Disc Medicine Inc | IRON | 254604101 | $65.0M | 1.31% | 888,401 | SH |
| 26 | Cytokinetics Inc | CYTK | 23282W605 | $64.7M | 1.31% | 758,952 | SH |
| 27 | Septerna Inc | SEPN | 81734D104 | $63.6M | 1.29% | 1,900,000 | SH |
| 28 | Olema Pharmaceuticals Inc | OLMA | 68062P106 | $60.8M | 1.23% | 4,856,949 | SH |
| 29 | Arcus Biosciences Inc | RCUS | 03969F109 | $53.8M | 1.09% | 1,745,000 | SH |
| 30 | Crinetics Pharmaceuticals Inc | CRNX | 22663K107 | $53.2M | 1.08% | 1,420,788 | SH |
| 31 | Kailera Therapeutics Inc | KLRA | 482931102 | $48.8M | 0.99% | 2,214,286 | SH |
| 32 | Dyne Therapeutics, Inc | DYN | 26818M108 | $47.3M | 0.96% | 2,129,125 | SH |
| 33 | Structure Therapeutics Inc | GPCR | 86366E106 | $46.9M | 0.95% | 872,967 | SH |
| 34 | Taboola.com Ltd | TBLA | M8744T106 | $42.1M | 0.85% | 8,423,410 | SH |
| 35 | Palvella Therapeutics Inc | PVLA | 697947109 | $39.3M | 0.80% | 257,485 | SH |
| 36 | Silence Therapeutics PLC | SLN | 82686Q101 | $36.4M | 0.74% | 3,311,438 | SH |
| 37 | Denali Therapeutics Inc | DNLI | 24823R105 | $35.9M | 0.73% | 1,396,513 | SH |
| 38 | Remitly Global Inc | RELY | 75960P104 | $34.6M | 0.70% | 1,543,271 | SH |
| 39 | Cullinan Therapeutics Inc | CGEM | 230031106 | $34.5M | 0.70% | 1,893,410 | SH |
| 40 | Capital One Finl Corp | COF | 14040H105 | $34.4M | 0.70% | 171,615 | SH |
| 41 | Trevi Therapeutics Inc | TRVI | 89532M101 | $33.3M | 0.67% | 1,786,867 | SH |
| 42 | Alphabet Inc | GOOGL | 02079K305 | $32.2M | 0.65% | 90,000 | SH |
| 43 | Dbv Technologies SA | DBVT | 23306J309 | $30.5M | 0.62% | 1,857,362 | SH |
| 44 | Absci Corp | ABSI | 00091E109 | $28.7M | 0.58% | 2,474,764 | SH |
| 45 | Sionna Therapeutics Inc | SION | 829401108 | $26.9M | 0.54% | 610,515 | SH |
| 46 | Rapport Therapeutics Inc | RAPP | 75383L102 | $26.7M | 0.54% | 641,469 | SH |
| 47 | Amylyx Pharmaceuticals Inc | AMLX | 03237H101 | $26.6M | 0.54% | 1,480,586 | SH |
| 48 | Annexon Inc | ANNX | 03589W102 | $25.5M | 0.52% | 4,458,646 | SH |
| 49 | Monopar Therapeutics Inc | MNPR | 61023L207 | $25.0M | 0.51% | 270,118 | SH |
| 50 | Oruka Therapeutics Inc | ORKA | 687604108 | $23.8M | 0.48% | 250,000 | SH |
| Period | Filed | AUM | Holdings | Accession |
|---|---|---|---|---|
| 2026-06-30 | 2026-08-13 | $4.94B | 119 | 0002005245-26-000008 |
| 2026-03-31 | 2026-05-14 | $3.61B | 102 | 0002005245-26-000006 |
| 2025-12-31 | 2026-02-13 | $3.35B | 115 | 0002005245-26-000003 |
| 2025-09-30 | 2025-11-13 | $2.56B | 117 | 0002005245-25-000012 |
GREENWICH, CT 06831