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Institutional Ownership · SEC Form 13F

Who owns IRON (IRON)


Which tracked institutional funds hold IRON, how they are positioned, and who is buying versus exiting — from SEC Form 13F-HR filings. See IRON company fundamentals →

Ownership as of the 2026-Q1 13F filings. 13F is disclosed up to 45 days after quarter-end, so the most recent quarter fills in over the following weeks.

204
Institutional holders
41,866,135
Shares held (tracked funds)

How the tape is positioned

44 tracked funds added or opened IRON while 94 trimmed or exited it between 2025-Q4 and 2026-Q1 — the tape is split. When large holders disagree on a name, the funds moving first are sometimes ahead of the story.

A prompt to read the filings, not a verdict. 13F is a quarter-end snapshot disclosed up to 45 days late; a fund adds or exits for mandate, benchmark, and timing reasons that have nothing to do with a view on the stock. This is a starting question, not a signal to trade.

Conviction spread

IRON’s largest tracked holder by dollar value, FMR LLC, sizes it at 0.0% of its own reported 13F book, while the median holder sizes it at 0.1% of theirs — a 0.1pp gap the other way — the median holder sizes IRON more heavily than its largest holder by dollar value does.

Book-share is each fund’s reported value in IRON divided by its whole reported 13F book, so it is comparable across funds of different sizes and is unaffected by stock splits. A higher share means a fund has committed more of its book to the name — a starting question about conviction, not a verdict or a signal to trade.

Institutional & insider positioning

Between 2025-Q4 and 2026-Q1, across 204 tracked filers holding IRON, 127 increased or opened the position and 86 reduced or closed it; over the same quarter, open-market insider Form 4 buying and selling roughly offset.

This fuses two public signals for the same quarter — how tracked institutions changed their positions and whether insiders bought or sold in the open market. It describes what was filed; it is a starting question, not a verdict or a signal to trade.

New buyers & exits

Funds opening or closing a position in IRON between the 2025-Q4 and 2026-Q1 13F filings, and the largest changes among funds holding it in both. New buyers and exits are counted on fund presence (split-invariant); adds and trims are measured on reported value.

New buyers 24

  • VANGUARD CAPITAL MANAGEMENT LLC$88M
  • TCG Crossover Management, LLC$86M
  • Bellevue Group AG$29M
  • Octagon Capital Advisors LP$17M
  • VANGUARD PORTFOLIO MANAGEMENT LLC$16M
  • VANGUARD FIDUCIARY TRUST CO$14M

Full exits 24

  • VANGUARD GROUP INC$121M
  • First Light Asset Management, LLC$42M
  • PERCEPTIVE ADVISORS LLC$36M
  • GREAT POINT PARTNERS LLC$20M
  • Balyasny Asset Management L.P.$18M
  • TimesSquare Capital Management, LLC$15M

Largest adds

  • BVF INC/IL$30M
  • STATE STREET CORP$14M
  • Opaleye Management Inc.$11M
  • Bank of New York Mellon Corp$8M
  • DIMENSIONAL FUND ADVISORS LP$7M
  • Assenagon Asset Management S.A.$7M

Largest trims

  • FMR LLC$83M
  • JPMORGAN CHASE & CO$42M
  • PRICE T ROWE ASSOCIATES INC /MD/$36M
  • BlackRock, Inc.$35M
  • Atlas Venture Life Science Advisors, LLC$23M
  • GOLDMAN SACHS GROUP INC$19M

Institutional holders

One row per tracked fund, largest reported value first. “% of value” is the fund’s share of this security’s tracked institutional value — not of shares outstanding. Rows marked stale are from an earlier filing than the security’s latest quarter — that fund is absent from the newest snapshot (position exited, or reported under a different name).

FundSharesReported value% of valueQuarter
FMR LLC added5,472,315$350M11.8%2026-Q1
RA CAPITAL MANAGEMENT, L.P. added2,450,221$157M5.3%2026-Q1
BlackRock, Inc. trimmed2,273,831$145M4.9%2026-Q1
WELLINGTON MANAGEMENT GROUP LLP added1,713,375$110M3.7%2026-Q1
STATE STREET CORP added1,698,244$109M3.7%2026-Q1
PRICE T ROWE ASSOCIATES INC /MD/ trimmed1,549,350$99M3.3%2026-Q1
Atlas Venture Life Science Advisors, LLC1,513,875$97M3.3%2026-Q1
VANGUARD CAPITAL MANAGEMENT LLC new1,375,430$88M3.0%2026-Q1
Frazier Life Sciences Management, L.P. added1,354,852$87M2.9%2026-Q1
TCG Crossover Management, LLC added1,341,862$86M2.9%2026-Q1
JPMORGAN CHASE & CO trimmed1,371,480$83M2.8%2026-Q1
BVF INC/IL added1,272,312$81M2.7%2026-Q1
ORBIMED ADVISORS LLC1,067,550$68M2.3%2026-Q1
Siren, L.L.C.988,401$63M2.1%2026-Q1
Woodline Partners LP added958,281$61M2.1%2026-Q1
GEODE CAPITAL MANAGEMENT, LLC added744,222$48M1.6%2026-Q1
Vestal Point Capital, LP trimmed700,000$45M1.5%2026-Q1
DEERFIELD MANAGEMENT COMPANY, L.P. added657,000$42M1.4%2026-Q1
GOLDMAN SACHS GROUP INC trimmed639,842$41M1.4%2026-Q1
JENNISON ASSOCIATES LLC added610,382$39M1.3%2026-Q1
Logos Global Management LP added560,000$36M1.2%2026-Q1
Assenagon Asset Management S.A. added546,247$35M1.2%2026-Q1
ARMISTICE CAPITAL, LLC added536,000$34M1.2%2026-Q1
Bellevue Group AG new459,314$29M1.0%2026-Q1
Saturn V Capital Management LP added449,926$29M1.0%2026-Q1
Opaleye Management Inc. added421,000$27M0.9%2026-Q1
Palo Alto Investors LP added401,719$26M0.9%2026-Q1
EVENTIDE ASSET MANAGEMENT, LLC added395,572$25M0.9%2026-Q1
DIMENSIONAL FUND ADVISORS LP added394,447$25M0.9%2026-Q1
Pictet Asset Management Holding SA trimmed387,005$25M0.8%2026-Q1
Aberdeen Group plc added375,614$24M0.8%2026-Q1
Foresite Capital Management V, LLC added374,069$24M0.8%2026-Q1
BAKER BROS. ADVISORS LP added349,657$22M0.8%2026-Q1
LOOMIS SAYLES & CO L P added317,222$20M0.7%2026-Q1
Checkpoint Capital L.P. trimmed286,661$18M0.6%2026-Q1
Octagon Capital Advisors LP trimmed270,000$17M0.6%2026-Q1
CHARLES SCHWAB INVESTMENT MANAGEMENT INC added251,195$16M0.5%2026-Q1
VANGUARD PORTFOLIO MANAGEMENT LLC new247,338$16M0.5%2026-Q1
NORTHERN TRUST CORP added247,195$16M0.5%2026-Q1
VANGUARD FIDUCIARY TRUST CO new217,436$14M0.5%2026-Q1
Bank of New York Mellon Corp added204,968$13M0.4%2026-Q1
SILVERARC CAPITAL MANAGEMENT, LLC trimmed196,028$13M0.4%2026-Q1
Ensign Peak Advisors, Inc added191,487$12M0.4%2026-Q1
Integral Health Asset Management, LLC new170,000$11M0.4%2026-Q1
BANK OF AMERICA CORP /DE/ added166,775$11M0.4%2026-Q1
Bain Capital Life Sciences Investors, LLC trimmed141,234$9M0.3%2026-Q1
BNP PARIBAS FINANCIAL MARKETS added127,737$8M0.3%2026-Q1
Alyeska Investment Group, L.P. added125,000$8M0.3%2026-Q1
Catalio Capital Management, LP added122,978$8M0.3%2026-Q1
UBS AM, a distinct business unit of UBS ASSET MANAGEMENT AMERICAS LLC trimmed110,890$7M0.2%2026-Q1
KENNEDY CAPITAL MANAGEMENT LLC added108,286$7M0.2%2026-Q1
UBS Group AG trimmed98,621$6M0.2%2026-Q1
CITADEL ADVISORS LLC trimmed97,930$6M0.2%2026-Q1
DNB Asset Management AS added96,755$6M0.2%2026-Q1
MORGAN STANLEY added94,264$6M0.2%2026-Q1
MILLENNIUM MANAGEMENT LLC trimmed83,259$5M0.2%2026-Q1
Jump Financial, LLC added81,829$5M0.2%2026-Q1
Sofinnova Investments, Inc. trimmed78,320$5M0.2%2026-Q1
Freestone Grove Partners LP new68,687$4M0.1%2026-Q1
iA Global Asset Management Inc. trimmed66,243$4M0.1%2026-Q1
Sio Capital Management, LLC added65,203$4M0.1%2026-Q1
Casdin Capital, LLC new65,000$4M0.1%2026-Q1
KVP Capital Advisors, LP58,250$4M0.1%2026-Q1
MOORE CAPITAL MANAGEMENT, LP new57,796$4M0.1%2026-Q1
EverSource Wealth Advisors, LLC added105,077$4M0.1%2026-Q1
Rafferty Asset Management, LLC added53,869$3M0.1%2026-Q1
SPHERA FUNDS MANAGEMENT LTD. trimmed53,538$3M0.1%2026-Q1
NEXTBio Capital Management LP added52,655$3M0.1%2026-Q1
Nuveen, LLC added51,380$3M0.1%2026-Q1
Burkehill Global Management, LP50,000$3M0.1%2026-Q1
Atle Fund Management AB added107,255$3M0.1%2026-Q1
SCHRODER INVESTMENT MANAGEMENT GROUP added50,959$3M0.1%2026-Q1
Swiss National Bank48,000$3M0.1%2026-Q1
AMERIPRISE FINANCIAL INC trimmed45,837$3M0.1%2026-Q1
RAYMOND JAMES FINANCIAL INC trimmed44,700$3M0.1%2026-Q1
BNP PARIBAS ASSET MANAGEMENT Holding S.A. trimmed39,910$3M0.1%2026-Q1
LAZARD ASSET MANAGEMENT LLC trimmed39,400$3M0.1%2026-Q1
Universal- Beteiligungs- und Servicegesellschaft mbH added38,006$2M0.1%2026-Q1
SEVEN GRAND MANAGERS, LLC35,000$2M0.1%2026-Q1
XTX Topco Ltd added34,418$2M0.1%2026-Q1
VANGUARD GROUP INC added1,523,314$121M4.1%2025-Q4 stale
First Light Asset Management, LLC added523,167$42M1.4%2025-Q4 stale
PERCEPTIVE ADVISORS LLC added450,743$36M1.2%2025-Q4 stale
ADAGE CAPITAL PARTNERS GP, L.L.C.450,000$30M1.0%2025-Q3 stale
GREAT POINT PARTNERS LLC new250,000$20M0.7%2025-Q4 stale
Balyasny Asset Management L.P. trimmed221,761$18M0.6%2025-Q4 stale
Paradigm Biocapital Advisors LP trimmed247,716$16M0.6%2025-Q3 stale
TimesSquare Capital Management, LLC added187,777$15M0.5%2025-Q4 stale
First Turn Management, LLC trimmed153,206$12M0.4%2025-Q4 stale
D. E. Shaw & Co., Inc. added219,603$11M0.4%2025-Q1 stale
Blue Owl Capital Holdings LP trimmed102,260$7M0.2%2025-Q3 stale
Hudson Bay Capital Management LP102,185$7M0.2%2025-Q4 stale
Patient Square Capital LP74,000$6M0.2%2025-Q4 stale
Verition Fund Management LLC added63,535$5M0.2%2025-Q4 stale
ExodusPoint Capital Management, LP added58,211$5M0.2%2025-Q4 stale
SUVRETTA CAPITAL MANAGEMENT, LLC new80,000$4M0.1%2025-Q1 stale
Nicholas Investment Partners, LP trimmed48,082$4M0.1%2025-Q4 stale
Exome Asset Management LLC trimmed46,743$4M0.1%2025-Q4 stale
AMERICAN CENTURY COMPANIES INC added30,328$2M0.1%2025-Q4 stale
TWINBEECH CAPITAL LP new45,448$2M0.1%2025-Q1 stale

Ownership over time

Tracked institutional holder count and total shares held by filing quarter (independent scales). The curated-era tail and any mid-ingest latest quarter are handled honestly — a partial quarter is not drawn as a collapse.

HoldersTotal shares

Reading this table

Funds hold the same stock for different reasons — an index fund “holds” almost everything, an active manager sizes a name to a mandate and a benchmark, and each fund entered at its own price and time. Because 13F is filed up to 45 days after quarter-end, every row is a backward-looking snapshot; a manager may have traded since. Share-class siblings (a company’s A and C shares) are rolled up to one line so a dual-class name is never double-counted. Compare like-for-like. A large holder is not an endorsement, and a fund exiting is not a warning — this is a starting question, not a verdict.

About 13F filings

A Form 13F is a quarterly disclosure that institutional investment managers with over $100 million in US-listed equities must file with the SEC. In plain English: it is a snapshot of the long stock positions a fund held at the end of a quarter. It covers long US-listed equities only — not short positions, options, cash, or private holdings — and the funds shown are the large sample we track, not the complete 13F universe.

Learn how to read institutional ownership