Siren, L.L.C.
Long book
$3.61B
Q1 2026
Positions
100
Top-10 weight
50%
concentration
Last quarter
+27.5%
SPY +14.8%
Turnover
39%
of book per quarter
Strategy in plain words
auto-generated from filingsSiren, L.L.C. is a diversified fundamental manager, specialised in healthcare (93% of the long book), running a $3.61B US long book across 100 positions.
The portfolio is moderately concentrated (top 10 ≈ 50% of the book). The portfolio is actively managed, with meaningful quarterly turnover. Current anchor positions: SCHOLAR ROCK HOLDING CORP, KYMERA THERAPEUTICS INC, ERASCA INC, EDGEWISE THERAPEUTICS INC, BEONE MEDICINES LTD-ADR.
Over the last 7 quarters its long book ran on average 7.6pp per quarter ahead of the S&P 500, beating the index in 5 of 7 quarters. We rate its filings as signal-bearing: position changes reflect genuine views.
Implied long-book return vs S&P 500
methodology: positions priced quarterly, no shorts/options Fund long book S&P 500
Q3 2024
+12.8%
Q4 2024
-24.3%
Q1 2025
+10.5%
Q2 2025
+28.5%
Q3 2025
+23.4%
Q4 2025
+5.4%
Q1 2026
+27.5%
Sector allocation
Healthcare 93%
Technology 5%
Services media 1%
Materials 1%
Industrials 0%
Consumer discretionary 0%
Financials 0%
Other 0%
Long book by quarter
What does Siren, L.L.C. own?
Q1 2026 13F| Company | Sector | Shares | Value | % of book | Change |
|---|---|---|---|---|---|
| SRRK SCHOLAR ROCK HOLDING CORP | Healthcare | 10.8M | $532.2M | 14.8% | Held |
| KYMR KYMERA THERAPEUTICS INC | Healthcare | 3.2M | $265.4M | 7.4% | -3.0% |
| ERAS ERASCA INC | Healthcare | 11.2M | $181.9M | 5.0% | +28.4% |
| EWTX EDGEWISE THERAPEUTICS INC | Healthcare | 4.4M | $139.6M | 3.9% | -2.2% |
| TNGX TANGO THERAPEUTICS INC | Healthcare | 5.7M | $118.3M | 3.3% | -30.7% |
| BCAX BICARA THERAPEUTICS INC | Healthcare | 5.8M | $115.4M | 3.2% | +11.2% |
| RVMD REVOLUTION MEDICINES INC | Healthcare | 1.1M | $108.0M | 3.0% | -16.8% |
| ARWR ARROWHEAD PHARMACEUTICALS IN | Healthcare | 1.6M | $101.3M | 2.8% | +7.7% |
| MANE VERADERMICS INC | Healthcare | 1.5M | $95.1M | 2.6% | New |
| XENE XENON PHARMACEUTICALS INC | Healthcare | 1.3M | $76.7M | 2.1% | +62.2% |
| OLMA OLEMA PHARMACEUTICALS INC | Healthcare | 4.8M | $70.9M | 2.0% | +44.1% |
| CRNX CRINETICS PHARMACEUTICALS IN | Healthcare | 1.9M | $69.1M | 1.9% | +26.3% |
| LXRX LEXICON PHARMACEUTICALS INC | Healthcare | 44.3M | $69.1M | 1.9% | +13.8% |
| COGT COGENT BIOSCIENCES INC | Healthcare | 1.7M | $65.8M | 1.8% | +4.9% |
| STOK STOKE THERAPEUTICS INC | Healthcare | 2.0M | $65.0M | 1.8% | -11.2% |
| RCUS ARCUS BIOSCIENCES INC | Healthcare | 3.0M | $65.0M | 1.8% | Held |
| IRON DISC MEDICINE INC | Healthcare | 988.4K | $63.2M | 1.8% | Held |
| RYTM RHYTHM PHARMACEUTICALS INC | Healthcare | 725.5K | $63.1M | 1.7% | +45.1% |
| SLDB SOLID BIOSCIENCES INC | Healthcare | 7.7M | $55.4M | 1.5% | Held |
| SEPN SEPTERNA INC | Healthcare | 2.0M | $48.1M | 1.3% | Held |
| SYRE SPYRE THERAPEUTICS INC | Healthcare | 818.6K | $41.3M | 1.1% | Held |
| CYTK CYTOKINETICS INC | Healthcare | 614.0K | $40.5M | 1.1% | New |
| DYN DYNE THERAPEUTICS INC | Healthcare | 2.2M | $40.4M | 1.1% | -36.4% |
| TSHA TAYSHA GENE THERAPIES INC | Healthcare | 8.8M | $39.5M | 1.1% | -12.8% |
| ORIC ORIC PHARMACEUTICALS INC | Healthcare | 3.0M | $38.0M | 1.1% | +197.6% |
| ENGN enGene Therapeutics Inc | Healthcare | 5.3M | $35.8M | 1.0% | +57.5% |
| PVLA PALVELLA THERAPEUTICS INC | Healthcare | 257.5K | $32.1M | 0.9% | +243.3% |
| TBLA TABOOLA.COM LTD | Technology | 10.0M | $30.9M | 0.9% | Held |
| ELVN ENLIVEN THERAPEUTICS INC | Healthcare | 746.2K | $29.3M | 0.8% | New |
| DNLI DENALI THERAPEUTICS INC | Healthcare | 1.4M | $26.8M | 0.7% | Held |
| RELY REMITLY GLOBAL INC | Services media | 1.5M | $24.2M | 0.7% | -4.6% |
| DMRA DAMORA THERAPEUTICS INC | Healthcare | 900.0K | $23.3M | 0.6% | New |
| ZURA ZURA BIO LTD | Healthcare | 3.7M | $22.2M | 0.6% | +187.3% |
| ANNX ANNEXON INC | Healthcare | 4.0M | $21.9M | 0.6% | New |
| TRVI TREVI THERAPEUTICS INC | Healthcare | 1.8M | $21.3M | 0.6% | -21.9% |
| RAPP RAPPORT THERAPEUTICS INC | Healthcare | 641.5K | $20.1M | 0.6% | -9.5% |
| GOOGL ALPHABET INC-CL A | Technology | 65.7K | $18.9M | 0.5% | +217.4% |
| FULC FULCRUM THERAPEUTICS INC | Healthcare | 2.4M | $18.0M | 0.5% | +20.5% |
| WVE WAVE LIFE SCIENCES LTD | Healthcare | 2.5M | $17.8M | 0.5% | Held |
| DFTX DEFINIUM THERAPEUTICS INC | Materials | 919.5K | $17.4M | 0.5% | New |
| AMLX AMYLYX PHARMACEUTICALS INC | Healthcare | 1.2M | $17.1M | 0.5% | New |
| CGEM CULLINAN THERAPEUTICS INC | Healthcare | 1.2M | $17.0M | 0.5% | Held |
| NMRA NEUMORA THERAPEUTICS INC | Healthcare | 8.5M | $16.6M | 0.5% | +35.1% |
| QURE UNIQURE NV | Healthcare | 1.0M | $16.4M | 0.5% | New |
| CTMX CYTOMX THERAPEUTICS INC | Healthcare | 3.5M | $16.3M | 0.5% | New |
| NVDA NVIDIA CORP | Technology | 89.1K | $15.5M | 0.4% | +137.7% |
| MSFT MICROSOFT CORP | Technology | 41.4K | $15.3M | 0.4% | +175.9% |
| MNPR MONOPAR THERAPEUTICS INC | Healthcare | 270.1K | $14.8M | 0.4% | +27.2% |
| SION SIONNA THERAPEUTICS INC | Healthcare | 300.0K | $12.0M | 0.3% | Held |
| NBIS NEBIUS GROUP NV | Technology | 113.6K | $11.8M | 0.3% | +49.1% |
13F filing history
| Period | Form | Filed | Entries | Reported value | Flags | Source |
|---|---|---|---|---|---|---|
| Q1 2026 | 13F-HR | May 14, 2026 | 102 | $3.61B | canonical | SEC ↗ |
| Q4 2025 | 13F-HR | Feb 13, 2026 | 115 | $3.35B | canonical | SEC ↗ |
| Q3 2025 | 13F-HR | Nov 13, 2025 | 117 | $2.56B | canonical | SEC ↗ |
| Q2 2025 | 13F-HR | Aug 13, 2025 | 111 | $1.93B | canonical | SEC ↗ |
| Q1 2025 | 13F-HR/ARESTATEMENT | May 23, 2025 | 117 | $1.77B | canonical | SEC ↗ |
| Q1 2025 | 13F-HR | May 14, 2025 | 117 | $1.76B | SEC ↗ | |
| Q4 2024 | 13F-HR | Feb 14, 2025 | 119 | $2.26B | canonical | SEC ↗ |
| Q3 2024 | 13F-HR | Nov 13, 2024 | 112 | $2.00B | canonical | SEC ↗ |