Q2 2026 13F · SEC CIK 2005245

Siren, L.L.C.

Investment managerFiled 2026-08-13 for Q2 2026. Open the filing ↗ · All SEC filings ↗

Reported 13F value: $4.9B
Reported positions: 115
Holdings vs S&P 500, 3 yrs: —
Average holding period: 1.8 yrs

Siren, L.L.C. is an investment manager that reported 115 positions worth $4.9B in its Q2 2026 13F, filed 2026-08-13. Its largest holdings were Scholar Rock Hldg Corp (SRRK, 10.7%), Kymera Therapeutics Inc (KYMR, 6.8%), Erasca, Inc. (ERAS, 4.2%).

Siren, L.L.C. holdings largest 50 of 115 positions.

Weights are shares of the filer's total reported 13F value, compared with Q1 2026. Share changes may reflect splits; weight changes also reflect price moves. A 13F shows long US-listed positions only, up to 135 days after the fact.

Siren, L.L.C. 13F holdings
Stock	% of 13F value	Q1 2026	Shares	Share change	Reported value
SRRKScholar Rock Hldg Corp	10.7%	14.8%	9,575,013	-11.5%	$526.6M
KYMRKymera Therapeutics Inc	6.8%	7.4%	2,935,830	-7.9%	$336.7M
ERASErasca, Inc.	4.2%	5.0%	11,397,781	+1.4%	$208.8M
MANEVeradermics Inc	4.1%	2.6%	1,655,374	+10.0%	$203.5M
TNGXTango Therapeutics Inc	3.9%	3.3%	6,179,364	+9.2%	$193.2M
RVMDRevolution Medicines Inc	3.4%	3.0%	900,000	-19.0%	$168.6M
BCAXBicara Therapeutics Inc	3.4%	3.2%	5,602,970	-3.4%	$166.4M
ARWRArrowhead Pharmaceuticals in	2.8%	2.8%	1,715,476	+6.2%	$139.8M
ONCBeone Medicines Ltd	2.7%	3.8%	465,000	+0.0%	$132.5M
EWTXEdgewise Therapeutics Inc	2.6%	3.9%	3,184,629	-28.1%	$129.4M
RYTMRhythm Pharmaceuticals Inc	2.6%	1.7%	1,136,275	+56.6%	$126.2M
LXRXLexicon Pharmaceuticals Inc	2.2%	1.9%	44,303,518	+0.0%	$106.3M
ELVNEnliven Therapeutics Inc	1.8%	0.8%	1,774,411	+137.8%	$90.1M
SYRESpyre Therapeutics	1.7%	1.1%	968,598	+18.3%	$86.0M
PBLSParabilis Medicines, Inc.	1.7%	—	2,992,259	—	$81.9M
XENEXenon Pharmaceuticals Inc	1.6%	2.1%	1,318,564	+0.0%	$79.6M
SLDBSolid Bioscience Inc.	1.6%	1.5%	7,690,405	+0.0%	$76.8M
ABVXAbivax SA	1.6%	—	576,000	—	$76.8M
COAGHemab Therapeutics Holdings Inc	1.6%	—	2,086,834	—	$76.6M
RCUSArcus Biosciences Inc.	1.5%	1.8%	2,420,430	-19.5%	$74.6M
COGTCogent Biosciences Inc	1.5%	1.8%	1,859,279	+8.8%	$72.0M
RLAYRelay Therapeutics Inc	1.4%	—	3,650,000	—	$68.3M
TSHATaysha Gene Therapies Inc	1.4%	1.1%	9,846,579	+11.5%	$67.1M
24477V105Definium Therapeutics Inc	1.4%	0.5%	1,419,493	+54.4%	$66.8M
STOKStoke Therapeutics Inc	1.3%	1.8%	1,995,347	+0.0%	$65.3M
IRONDisc Medicine Inc	1.3%	1.8%	888,401	-10.1%	$65.0M
CYTKCytokinetics	1.3%	1.1%	758,952	+23.6%	$64.7M
SEPNSepterna Inc	1.3%	1.3%	1,900,000	-5.0%	$63.6M
OLMAOlema Pharmaceuticals Inc	1.2%	2.0%	4,856,949	+2.1%	$60.8M
CRNXCrinetics Pharmaceuticals in	1.1%	1.9%	1,420,788	-25.4%	$53.2M
KLRAKailera Therapeutics Inc	1.0%	—	2,214,286	—	$48.8M
DYNDyne Therapeutics Inc	1.0%	1.1%	2,129,125	-4.5%	$47.3M
GPCRStructure Therapeutics F Unspo	1.0%	1.8%	872,967	-34.3%	$46.9M
TBLATaboola.com Ltd	0.9%	0.9%	8,423,410	-15.5%	$42.1M
PVLAPalvella Therapeutics Inc Ne	0.8%	0.9%	257,485	+0.0%	$39.3M
SLNSilence Therapeutics PLC	0.7%	—	3,311,438	—	$36.4M
DNLIDenali Therapeutics Inc Com	0.7%	0.7%	1,396,513	+0.0%	$35.9M
RELYRemitly Global Inc Com	0.7%	0.7%	1,543,271	+0.0%	$34.6M
CGEMCullinan Therapeutics Inc	0.7%	0.5%	1,893,410	+58.7%	$34.5M
COFCapital One Finl Corp	0.7%	—	171,615	—	$34.4M
TRVITrevi Therapeutics Inc	0.7%	0.6%	1,786,867	+0.0%	$33.3M
ORICOric Pharmaceuticals Inc	0.7%	1.1%	2,998,192	+0.0%	$32.5M
GOOGLAlphabet Inc	0.7%	0.5%	90,000	+37.0%	$32.2M
DBVTDbv Technologies S A	0.6%	1.1%	1,857,362	+0.0%	$30.5M
ABSIAbsci Corporation	0.6%	—	2,474,764	—	$28.7M
829401108Sionna Therapeutics Inc	0.5%	—	610,515	—	$26.9M
RAPPRapport Therapeutics Inc	0.5%	0.6%	641,469	+0.0%	$26.7M
AMLXAmylyx Pharmaceuticals Inc	0.5%	0.5%	1,480,586	+20.4%	$26.6M
ANNXAnnexon Inc	0.5%	0.6%	4,458,646	+12.6%	$25.5M
MNPRMonopar Therapeutics Inc	0.5%	—	270,118	—	$25.0M

What Siren, L.L.C. bought and sold in Q2 2026, against Q1 2026.

New positions

Q1 2026's filing was too long to tell new positions apart.

Share counts compared with the Q1 2026 13F; a split also changes share counts. The latest filing lists more than 50 positions, so a position that left the top 50 may still be held.

How the holdings did against the S&P 500.

1 year: +108.2% /yr; S&P 500 +20.1%
3 years: —
5 years: —

A portfolio of the filer's 20 largest 13F positions, weighted by value, bought the trading day after each 13F was filed and held until the next one was: what copying this filer could have earned. 13Fs show long US-listed positions only, so this is an estimate of the stock picks, not the fund's reported returns.

Reported 13F value by quarter.

13F value by quarter
Quarter	13F value	Positions
Q2 2026	$4.9B	115
Q1 2026	$3.6B	100
Q4 2025	$3.4B	113
Q3 2025	$2.6B	115
Q2 2025	$1.9B	110
Q1 2025	$1.8B	116
Q4 2024	$2.3B	117
Q3 2024	$2.0B	109

Questions about Siren, L.L.C.'s portfolio

What stocks does Siren, L.L.C. own?

Siren, L.L.C.'s latest 13F, for Q2 2026 and filed Aug 13, 2026, lists 115 positions worth $4.9B. The largest are Scholar Rock Hldg Corp (SRRK) at 10.7%, Kymera Therapeutics Inc (KYMR) at 6.8%, Erasca, Inc. (ERAS) at 4.2%, Veradermics Inc (MANE) at 4.1% and Tango Therapeutics Inc (TNGX) at 3.9%.

What did Siren, L.L.C. buy last quarter?

In Q2 2026, Siren, L.L.C. added Enliven Therapeutics Inc (ELVN) (+137.8% shares), Cullinan Therapeutics Inc (CGEM) (+58.7% shares) and Rhythm Pharmaceuticals Inc (RYTM) (+56.6% shares), compared with its Q1 2026 filing.

What did Siren, L.L.C. sell last quarter?

In Q2 2026, Siren, L.L.C. cut from its top 50 Centessa Pharmaceuticals PLC (CNTA), cut from its top 50 enGene Holdings Inc. (ENGN), cut from its top 50 Damora Therapeutics Inc (GLTO), cut from its top 50 Zura Bio Ltd (ZURA), cut from its top 50 Fulcrum Therapeutics Inc (FULC), Structure Therapeutics F Unspo (GPCR) (-34.3% shares), Edgewise Therapeutics Inc (EWTX) (-28.1% shares) and Crinetics Pharmaceuticals in (CRNX) (-25.4% shares), compared with its Q1 2026 filing.

When is Siren, L.L.C.'s next 13F filing due?

13F filings are due 45 days after each quarter ends. Siren, L.L.C.'s filing for the quarter ending Sep 30, 2026 is due by Nov 14, 2026; this page updates the day after it is published.