Atrium Therapeutics, Inc.
Ownership
Ownership Structure
Who owns Atrium Therapeutics, Inc. (RNA)? This page shows the largest institutions and funds, the ownership structure and the latest insider transactions. 88.2% of the shares are freely tradable; institutional investors hold 84.9%.
Largest Shareholders
Funds
| Name | Stake (%) | Shares | Change (%) | Date |
|---|---|---|---|---|
| iShares Russell 2000 ETF | 1.79 | 2,774,867 | +0.0 | 02/28/2026 |
| BlackRock Event Driven Equity Instl | 1.13 | 1,753,889 | +0.0 | 01/31/2026 |
| iShares Russell 2000 Growth ETF | 0.57 | 887,885 | +0.0 | 02/28/2026 |
| NexPoint Merger Arbitrage Z | 0.53 | 824,400 | +0.0 | 12/31/2025 |
| The Merger Fund A | 0.53 | 817,749 | +0.0 | 12/31/2025 |
| Vanguard Russell 2000 ETF | 0.36 | 551,069 | -3.1 | 01/31/2026 |
| Amundi Tiedemann Arbitrage Strat I USD | 0.34 | 529,311 | +7.0 | 11/30/2025 |
| BSF Global Event Driven Z2 USD | 0.29 | 442,961 | +30.9 | 12/31/2025 |
| PICTON Arbitrage Plus Alternative Fund F | 0.22 | 346,300 | +10.9 | 12/31/2025 |
| Vanguard Health Care ETF | 0.21 | 330,291 | +0.0 | 01/31/2026 |
Largest reported positions according to regulatory filings; stake as a percentage of shares outstanding, change versus the previous filing. Source: fundamentals data.
Insider holdings
| Person | Role | Shares | Value | As of | Type |
|---|---|---|---|---|---|
| Boyce Sarah | Director | 138,668 | 1,150,944 $ | Sep 18, 2026 | direct |
| Gallagher Kathleen P. | See Remarks | 119,729 | 993,751 $ | Sep 18, 2026 | direct |
| Hughes Steven George | Chief Medical Officer | 51,638 | 428,595 $ | Sep 18, 2026 | direct |
| Younis Husam | Chief Scientific Officer | 41,441 | 343,960 $ | Sep 18, 2026 | direct |
| Hoyos Rocio Martin | Chief Strategy Officer | 38,340 | 318,222 $ | Sep 18, 2026 | direct |
| Winslow Brendan R. | Chief Financial Officer | 36,859 | 305,930 $ | Sep 18, 2026 | direct |
| Kenney Stephanie | See Remarks | 33,085 | 274,606 $ | Sep 18, 2026 | direct |
| Flanagan W. Michael | Director | 31,974 | 265,384 $ | Sep 18, 2026 | direct |
Holdings as of each person's most recent SEC Form 4 filing — excluding options and RSUs, which are not shares yet. Holdings may have changed between two filings.
Insiders
Insider Transactions
| Date | Person | Role | Type | Shares | Price | Value |
|---|---|---|---|---|---|---|
| Sep 18, 2026 | Younis Husam | Chief Scientific Officer | Other | 11,216 | 8.95 | 100,383 |
| Sep 18, 2026 | Hughes Steven George | Chief Medical Officer | Other | 21,459 | 8.95 | 192,058 |
| Sep 18, 2026 | Flanagan W. Michael | Director | Other | 22,812 | 8.95 | 204,167 |
| Sep 18, 2026 | Boyce Sarah | Director | Other | 126,418 | 8.95 | 1,131,441 |
| Sep 18, 2026 | Kenney Stephanie | See Remarks | Other | 2,375 | 8.95 | 21,256 |
| Sep 18, 2026 | Gallagher Kathleen P. | See Remarks | Other | 11,632 | 8.95 | 104,106 |
| Sep 18, 2026 | Winslow Brendan R. | Chief Financial Officer | Other | 6,742 | 8.95 | 60,341 |
| Sep 18, 2026 | Hoyos Rocio Martin | Chief Strategy Officer | Other | 8,320 | 8.95 | 74,464 |
Reportable transactions by officers and major shareholders from SEC Form 4 filings. "Other" includes things like stock grants and option exercises without a buy/sell character. View all insider transactions →
Data as of: September 25, 2026 · Source: fundamental data & SEC filings (annual and quarterly reports, 10-K/10-Q)
Note: pure fact-based analysis, not investment advice and not a solicitation to buy or sell. All figures without guarantee.