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Siren, L.L.C.

Institutional InvestorSimilar funds →SEC EDGAR: CIK 2005245
Institutional-grade research for retail investors

Sector Allocation

  • Healthcare93.2%$4.6B
  • Technology4.5%$222.0M
  • Industrials0.9%$43.0M
  • Financials0.9%$42.8M
  • Consumer Discretionary0.4%$21.3M
  • Communication Services0.1%$2.8M
  • Real Estate0.0%$1.5M

AUM History

13fpro.ai/research/fund/siren-l-l-c-2005245

Conviction and streaks

Diversifying · top 10 = 44.8%

From the fund's last 12 quarters of 13F filings: positions held longest at size, and names it added to or trimmed several quarters running.

SRRK$SRRKConviction hold10.7% weight · held 7 quartersKYMR$KYMRConviction hold6.8% weight · held 7 quartersERAS$ERASConviction hold4.2% weight · held 7 quartersTNGX$TNGXConviction hold3.9% weight · held 7 quartersRVMD$RVMDConviction hold3.4% weight · held 7 quartersNOW$NOWAccumulating+1851% shares · 4 quarters runningDT$DTAccumulating+106% shares · 4 quarters runningGTLB$GTLBAccumulating+257% shares · 4 quarters runningMNDY$MNDYAccumulating+2025% shares · 4 quarters runningPDD$PDDAccumulating+119% shares · 3 quarters runningDYN$DYNTrimming-61% shares · 5 quarters runningKYMR$KYMRTrimming-14% shares · 3 quarters runningAMZN$AMZNTrimming-44% shares · 3 quarters runningRVMD$RVMDTrimming-33% shares · 2 quarters runningEWTX$EWTXTrimming-30% shares · 2 quarters running

Largest positions — Q2 2026

Top 20 stock positions. Options are left out: 13F reports them at the underlying's value.

13fpro.ai/research/fund/siren-l-l-c-2005245

Siren, L.L.C. 13F holdings — Q2 2026

$4.9B portfolio (+37.0% QoQ) · 117 holdings · Q2 2026 13F · top 10 are 45% of the stock portfolio

Includes $15.6M of put/call options ($0 puts, $15.6M calls), which 13F rules report at the value of the underlying shares, not the premium at risk. Stocks alone: $4.9B. Weights use the stock portfolio.

All holdings — Siren, L.L.C. (Q2 2026)

117 disclosed positions from the Form 13F-HR on SEC EDGAR, with quarter-over-quarter share changes. Largest by value first; the ten above are not repeated.

Company
RYTM$RYTMRHYTHM PHARMACEUTICALS, INC.$126.2M+57%
LXRX$LXRXLEXICON PHARMACEUTICALS, INC.$106.3M—
ELVN$ELVNEnliven Therapeutics, Inc.$90.1M+138%
SYRE$SYRESpyre Therapeutics, Inc.$86.0M+18%
PBLS$PBLSParabilis Medicines, Inc.$81.9MNew
XENE$XENEXenon Pharmaceuticals Inc.$79.6M—
SLDB$SLDBSolid Biosciences Inc.$76.8M—
ABVX$ABVXAbivax S.A.adr$76.8MNew
COAG$COAGHemab Therapeutics Holdings, Inc.$76.6MNew
RCUS$RCUSArcus Biosciences, Inc.$74.6M-20%
COGT$COGTCogent Biosciences, Inc.$72.0M+9%
RLAY$RLAYRelay Therapeutics, Inc.$68.3MNew
TSHA$TSHATaysha Gene Therapies, Inc.$67.1M+12%
DFTX$DFTXDefinium Therapeutics, Inc.$66.8M+54%
STOK$STOKStoke Therapeutics, Inc.$65.3M—

What changed in Q2 2026

Against the previous quarter's 13F: 26 new, 32 added to, 21 trimmed, 9 sold out. Share-count changes; largest moves by dollar size first.

New positions (26)

  • PBLS$PBLSParabilis Medicines, Inc.$81.9M

    first bought this quarter

  • ABVX$ABVXAbivax S.A.$76.8M

    first bought this quarter

  • COAG$COAGHemab Therapeutics Holdings, Inc.$76.6M

    first bought this quarter

  • RLAY$RLAYRelay Therapeutics, Inc.$68.3M

    first bought this quarter

  • KLRA$KLRAKailera Therapeutics, Inc.$48.8M

    first bought this quarter

  • COF$COFCAPITAL ONE FINANCIAL CORP$34.4M

    first bought this quarter

+20 more in the Excel export

Added to (32)

  • ELVN$ELVNEnliven Therapeutics, Inc.+138%

    now $90.1M · held 2 qtrs, 2 adds in a row

  • RYTM$RYTMRHYTHM PHARMACEUTICALS, INC.+57%

    now $126.2M · held 5+ qtrs, 2 adds in a row

  • DFTX$DFTXDefinium Therapeutics, Inc.+54%

    now $66.8M · held 2 qtrs, 2 adds in a row

  • MANE$MANEVeradermics, Inc+10%

    now $203.5M · held 2 qtrs, 2 adds in a row

  • TNGX$TNGXTango Therapeutics, Inc.+9%

    now $193.2M · held 5+ qtrs

  • SION$SIONSionna Therapeutics, Inc.+104%

    now $26.9M · held 5+ qtrs

+26 more in the Excel export

Trimmed (21)

  • SRRK$SRRKScholar Rock Holding Corp-12%

    now $526.6M · held 5+ qtrs

  • EWTX$EWTXEdgewise Therapeutics, Inc.-28%

    now $129.4M · held 5+ qtrs, 2 trims in a row

  • RVMD$RVMDRevolution Medicines, Inc.-19%

    now $168.6M · held 5+ qtrs, 2 trims in a row

  • KYMR$KYMRKymera Therapeutics, Inc.-8%

    now $336.7M · held 5+ qtrs, 3 trims in a row

  • GPCR$GPCRStructure Therapeutics Inc.-34%

    now $46.9M · held 4 qtrs

  • RCUS$RCUSArcus Biosciences, Inc.-20%

    now $74.6M · held 5+ qtrs

+15 more in the Excel export

Sold out (9)

  • CNTA$CNTACentessa Pharmaceuticals plcwas $41.8M

    held 6+ qtrs

  • FULC$FULCFulcrum Therapeutics, Inc.was $18.0M

    held 2 qtrs

  • WVE$WVEWave Life Sciences, Inc.was $17.8M

    held 6+ qtrs

  • QURE$QUREuniQure N.V.was $16.4M

    held 1 qtr

  • BCYC$BCYCBICYCLE THERAPEUTICS PLCwas $7.2M
  • FPS$FPSForgent Power Solutions, Inc.was $2.9M

+3 more in the Excel export

Share

Holdings by quarter

Every 13F Siren, L.L.C. has filed, 7 earlier quarters. Pick one to see what it held then.

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Is it too late to follow Siren, L.L.C.?

Q2 2026 13F filed with the SEC on Aug 13, 2026. Prices are closing prices as of Oct 26, 2026.

Average quality of Siren, L.L.C.'s top 20 holdings: 24/100 (our AI quality score, weighted by position size; 7 of the 20 are scored)

Top 10 since filing

-10.7%

Value-weighted move of the 10 largest stock positions

Turnover

10%

Last quarter; 52% over the last 4

Top 10 weight

45%

Share of the stock portfolio in its 10 largest positions

Held 4+ quarters

73%

Share of portfolio value in positions held a year or more

Highest-quality names it owns(among its 100 largest positions)

The 8 highest-scoring companies in this portfolio are a Pro feature.

How these are measured
  • Moves since the quarter-end and since the filing date use our own daily closing prices, from the close on (or just before) each date to the latest close.
  • Turnover is the lesser of shares bought or sold in a quarter, valued at the quarter-end prices in the 13F, divided by the average of the two quarters' stock portfolio values.
  • Quarters held and add/trim streaks count back only through quarters whose filed holdings add up to the filing's own cover-page total (back to Q2 2025 for this fund). A change counts as an add or a trim when the split-adjusted share count moves by more than 1%.
  • Estimate, not the fund's reported cost. For each quarter in the current holding period in which the fund's share count rose (split-adjusted), we take that quarter's average daily close and weight it by the shares added; sales do not change an average cost. Quarters where the stock's price history and the 13F's own implied price disagree by more than 2x are left out.
  • Put and call option rows report the value of the underlying shares, not a position the fund paid for, so they are left out of all of the above.

Portfolio Overview

Siren, L.L.C. disclosed 117 positions worth $4.9B in its Form 13F-HR for Q2 2026 — $4.9B in common stock plus $15.6M of put/call option positions (reported at underlying notional value, not premium at risk), led by $SRRK (Scholar Rock Holding Corp) at 10.7% of the equity portfolio, followed by $KYMR and $ERAS. During the quarter the fund opened 26 new positions and exited 9 — including a new stake in $PBLS and a full exit from $CNTA. The portfolio is most concentrated in Healthcare (93.2% of disclosed assets). All figures are sourced directly from Siren, L.L.C.’s Form 13F-HR filing with the SEC under CIK 2005245.

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AI-Powered Hedge Fund Analysis: Siren, L.L.C.

13F Pro is an AI hedge fund tracker and stock research platform. For Siren, L.L.C. (SEC CIK: 2005245), the platform ingests every quarterly Form 13F filing and applies AI-powered analysis on top — 10 specialized AI analysts (value, growth, momentum, macro, activist, and more) debate the fund's top positions and publish AI-generated analysis with cited SEC sources.

Every holding in Siren, L.L.C.'s portfolio is scored on an AI quality ranking built from its SEC filings (ROIC, FCF margin, revenue growth, institutional flow, earnings quality, shareholder dilution, and more). Track accumulation and distribution quarter over quarter, identify conviction positions, and see AI stock analysis for each position — alongside 8,700+ other institutional filers and 2,800+ AI-ranked companies.