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.
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).
| Fund | Shares | Reported value | % of value | Quarter |
|---|---|---|---|---|
| FMR LLC added | 5,472,315 | $350M | 11.8% | 2026-Q1 |
| RA CAPITAL MANAGEMENT, L.P. added | 2,450,221 | $157M | 5.3% | 2026-Q1 |
| BlackRock, Inc. trimmed | 2,273,831 | $145M | 4.9% | 2026-Q1 |
| WELLINGTON MANAGEMENT GROUP LLP added | 1,713,375 | $110M | 3.7% | 2026-Q1 |
| STATE STREET CORP added | 1,698,244 | $109M | 3.7% | 2026-Q1 |
| PRICE T ROWE ASSOCIATES INC /MD/ trimmed | 1,549,350 | $99M | 3.3% | 2026-Q1 |
| Atlas Venture Life Science Advisors, LLC | 1,513,875 | $97M | 3.3% | 2026-Q1 |
| VANGUARD CAPITAL MANAGEMENT LLC new | 1,375,430 | $88M | 3.0% | 2026-Q1 |
| Frazier Life Sciences Management, L.P. added | 1,354,852 | $87M | 2.9% | 2026-Q1 |
| TCG Crossover Management, LLC added | 1,341,862 | $86M | 2.9% | 2026-Q1 |
| JPMORGAN CHASE & CO trimmed | 1,371,480 | $83M | 2.8% | 2026-Q1 |
| BVF INC/IL added | 1,272,312 | $81M | 2.7% | 2026-Q1 |
| ORBIMED ADVISORS LLC | 1,067,550 | $68M | 2.3% | 2026-Q1 |
| Siren, L.L.C. | 988,401 | $63M | 2.1% | 2026-Q1 |
| Woodline Partners LP added | 958,281 | $61M | 2.1% | 2026-Q1 |
| GEODE CAPITAL MANAGEMENT, LLC added | 744,222 | $48M | 1.6% | 2026-Q1 |
| Vestal Point Capital, LP trimmed | 700,000 | $45M | 1.5% | 2026-Q1 |
| DEERFIELD MANAGEMENT COMPANY, L.P. added | 657,000 | $42M | 1.4% | 2026-Q1 |
| GOLDMAN SACHS GROUP INC trimmed | 639,842 | $41M | 1.4% | 2026-Q1 |
| JENNISON ASSOCIATES LLC added | 610,382 | $39M | 1.3% | 2026-Q1 |
| Logos Global Management LP added | 560,000 | $36M | 1.2% | 2026-Q1 |
| Assenagon Asset Management S.A. added | 546,247 | $35M | 1.2% | 2026-Q1 |
| ARMISTICE CAPITAL, LLC added | 536,000 | $34M | 1.2% | 2026-Q1 |
| Bellevue Group AG new | 459,314 | $29M | 1.0% | 2026-Q1 |
| Saturn V Capital Management LP added | 449,926 | $29M | 1.0% | 2026-Q1 |
| Opaleye Management Inc. added | 421,000 | $27M | 0.9% | 2026-Q1 |
| Palo Alto Investors LP added | 401,719 | $26M | 0.9% | 2026-Q1 |
| EVENTIDE ASSET MANAGEMENT, LLC added | 395,572 | $25M | 0.9% | 2026-Q1 |
| DIMENSIONAL FUND ADVISORS LP added | 394,447 | $25M | 0.9% | 2026-Q1 |
| Pictet Asset Management Holding SA trimmed | 387,005 | $25M | 0.8% | 2026-Q1 |
| Aberdeen Group plc added | 375,614 | $24M | 0.8% | 2026-Q1 |
| Foresite Capital Management V, LLC added | 374,069 | $24M | 0.8% | 2026-Q1 |
| BAKER BROS. ADVISORS LP added | 349,657 | $22M | 0.8% | 2026-Q1 |
| LOOMIS SAYLES & CO L P added | 317,222 | $20M | 0.7% | 2026-Q1 |
| Checkpoint Capital L.P. trimmed | 286,661 | $18M | 0.6% | 2026-Q1 |
| Octagon Capital Advisors LP trimmed | 270,000 | $17M | 0.6% | 2026-Q1 |
| CHARLES SCHWAB INVESTMENT MANAGEMENT INC added | 251,195 | $16M | 0.5% | 2026-Q1 |
| VANGUARD PORTFOLIO MANAGEMENT LLC new | 247,338 | $16M | 0.5% | 2026-Q1 |
| NORTHERN TRUST CORP added | 247,195 | $16M | 0.5% | 2026-Q1 |
| VANGUARD FIDUCIARY TRUST CO new | 217,436 | $14M | 0.5% | 2026-Q1 |
| Bank of New York Mellon Corp added | 204,968 | $13M | 0.4% | 2026-Q1 |
| SILVERARC CAPITAL MANAGEMENT, LLC trimmed | 196,028 | $13M | 0.4% | 2026-Q1 |
| Ensign Peak Advisors, Inc added | 191,487 | $12M | 0.4% | 2026-Q1 |
| Integral Health Asset Management, LLC new | 170,000 | $11M | 0.4% | 2026-Q1 |
| BANK OF AMERICA CORP /DE/ added | 166,775 | $11M | 0.4% | 2026-Q1 |
| Bain Capital Life Sciences Investors, LLC trimmed | 141,234 | $9M | 0.3% | 2026-Q1 |
| BNP PARIBAS FINANCIAL MARKETS added | 127,737 | $8M | 0.3% | 2026-Q1 |
| Alyeska Investment Group, L.P. added | 125,000 | $8M | 0.3% | 2026-Q1 |
| Catalio Capital Management, LP added | 122,978 | $8M | 0.3% | 2026-Q1 |
| UBS AM, a distinct business unit of UBS ASSET MANAGEMENT AMERICAS LLC trimmed | 110,890 | $7M | 0.2% | 2026-Q1 |
| KENNEDY CAPITAL MANAGEMENT LLC added | 108,286 | $7M | 0.2% | 2026-Q1 |
| UBS Group AG trimmed | 98,621 | $6M | 0.2% | 2026-Q1 |
| CITADEL ADVISORS LLC trimmed | 97,930 | $6M | 0.2% | 2026-Q1 |
| DNB Asset Management AS added | 96,755 | $6M | 0.2% | 2026-Q1 |
| MORGAN STANLEY added | 94,264 | $6M | 0.2% | 2026-Q1 |
| MILLENNIUM MANAGEMENT LLC trimmed | 83,259 | $5M | 0.2% | 2026-Q1 |
| Jump Financial, LLC added | 81,829 | $5M | 0.2% | 2026-Q1 |
| Sofinnova Investments, Inc. trimmed | 78,320 | $5M | 0.2% | 2026-Q1 |
| Freestone Grove Partners LP new | 68,687 | $4M | 0.1% | 2026-Q1 |
| iA Global Asset Management Inc. trimmed | 66,243 | $4M | 0.1% | 2026-Q1 |
| Sio Capital Management, LLC added | 65,203 | $4M | 0.1% | 2026-Q1 |
| Casdin Capital, LLC new | 65,000 | $4M | 0.1% | 2026-Q1 |
| KVP Capital Advisors, LP | 58,250 | $4M | 0.1% | 2026-Q1 |
| MOORE CAPITAL MANAGEMENT, LP new | 57,796 | $4M | 0.1% | 2026-Q1 |
| EverSource Wealth Advisors, LLC added | 105,077 | $4M | 0.1% | 2026-Q1 |
| Rafferty Asset Management, LLC added | 53,869 | $3M | 0.1% | 2026-Q1 |
| SPHERA FUNDS MANAGEMENT LTD. trimmed | 53,538 | $3M | 0.1% | 2026-Q1 |
| NEXTBio Capital Management LP added | 52,655 | $3M | 0.1% | 2026-Q1 |
| Nuveen, LLC added | 51,380 | $3M | 0.1% | 2026-Q1 |
| Burkehill Global Management, LP | 50,000 | $3M | 0.1% | 2026-Q1 |
| Atle Fund Management AB added | 107,255 | $3M | 0.1% | 2026-Q1 |
| SCHRODER INVESTMENT MANAGEMENT GROUP added | 50,959 | $3M | 0.1% | 2026-Q1 |
| Swiss National Bank | 48,000 | $3M | 0.1% | 2026-Q1 |
| AMERIPRISE FINANCIAL INC trimmed | 45,837 | $3M | 0.1% | 2026-Q1 |
| RAYMOND JAMES FINANCIAL INC trimmed | 44,700 | $3M | 0.1% | 2026-Q1 |
| BNP PARIBAS ASSET MANAGEMENT Holding S.A. trimmed | 39,910 | $3M | 0.1% | 2026-Q1 |
| LAZARD ASSET MANAGEMENT LLC trimmed | 39,400 | $3M | 0.1% | 2026-Q1 |
| Universal- Beteiligungs- und Servicegesellschaft mbH added | 38,006 | $2M | 0.1% | 2026-Q1 |
| SEVEN GRAND MANAGERS, LLC | 35,000 | $2M | 0.1% | 2026-Q1 |
| XTX Topco Ltd added | 34,418 | $2M | 0.1% | 2026-Q1 |
| VANGUARD GROUP INC added | 1,523,314 | $121M | 4.1% | 2025-Q4 stale |
| First Light Asset Management, LLC added | 523,167 | $42M | 1.4% | 2025-Q4 stale |
| PERCEPTIVE ADVISORS LLC added | 450,743 | $36M | 1.2% | 2025-Q4 stale |
| ADAGE CAPITAL PARTNERS GP, L.L.C. | 450,000 | $30M | 1.0% | 2025-Q3 stale |
| GREAT POINT PARTNERS LLC new | 250,000 | $20M | 0.7% | 2025-Q4 stale |
| Balyasny Asset Management L.P. trimmed | 221,761 | $18M | 0.6% | 2025-Q4 stale |
| Paradigm Biocapital Advisors LP trimmed | 247,716 | $16M | 0.6% | 2025-Q3 stale |
| TimesSquare Capital Management, LLC added | 187,777 | $15M | 0.5% | 2025-Q4 stale |
| First Turn Management, LLC trimmed | 153,206 | $12M | 0.4% | 2025-Q4 stale |
| D. E. Shaw & Co., Inc. added | 219,603 | $11M | 0.4% | 2025-Q1 stale |
| Blue Owl Capital Holdings LP trimmed | 102,260 | $7M | 0.2% | 2025-Q3 stale |
| Hudson Bay Capital Management LP | 102,185 | $7M | 0.2% | 2025-Q4 stale |
| Patient Square Capital LP | 74,000 | $6M | 0.2% | 2025-Q4 stale |
| Verition Fund Management LLC added | 63,535 | $5M | 0.2% | 2025-Q4 stale |
| ExodusPoint Capital Management, LP added | 58,211 | $5M | 0.2% | 2025-Q4 stale |
| SUVRETTA CAPITAL MANAGEMENT, LLC new | 80,000 | $4M | 0.1% | 2025-Q1 stale |
| Nicholas Investment Partners, LP trimmed | 48,082 | $4M | 0.1% | 2025-Q4 stale |
| Exome Asset Management LLC trimmed | 46,743 | $4M | 0.1% | 2025-Q4 stale |
| AMERICAN CENTURY COMPANIES INC added | 30,328 | $2M | 0.1% | 2025-Q4 stale |
| TWINBEECH CAPITAL LP new | 45,448 | $2M | 0.1% | 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.
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.