Comparable stake leader
BlackRock, Inc.
SEC ownership of Atrium Therapeutics, Inc.
Top holders, 13D/G large-stake signals, insider positions, and transaction flow tied to CIK 0002093101.
Disclosed value leader
PRICE T ROWE ASSOCIATES INC /MD/
Comparable rows
50/50
Latest evidence
31 Mar 2026
- Public ticker
- RNA on Nasdaq
- Parsed ownership sources
-
13F and 13D/G
Source: Parsed SEC ownership filingsUse: Compare filing families carefully
- Largest SEC-reported holder
-
BlackRock, Inc.
Ranking: Comparable ownership first, then disclosed value
- Comparable ownership rows
-
50 of 50
Meaning: Rows with safely comparable ownership %
- Latest 13D/G holder
-
BlackRock, Inc.
Source: Latest parsed Schedule 13D/G stake
- Latest parsed ownership date
-
31 Mar 2026
Freshness: Most recent filing date in this holder set
- Issuer CIK
- 0002093101
- Issuer location
- San Diego, CA
Ownership snapshot
CIK-linked ownership evidence from parsed SEC filings.
3 signals
Issuer
Names, identifiers, and filing context for this profile.
2 identity fields
Ownership snapshot
Top shareholders of Atrium Therapeutics, Inc. (13F + 13D/G + 3/4/5)
Grouped by holder across the latest SEC ownership disclosures. Start with comparable ownership when available, then verify the linked 13F, 13D/G, or 3/4/5 evidence.
Comparable stake leader
BlackRock, Inc.
Disclosed value leader
PRICE T ROWE ASSOCIATES I...
Comparable rows
50/50
Latest evidence
31 Mar 2026
13F
13D/G
Lead comparable stake: 6.6%
13D/G row: BlackRock, Inc.
Showing 1-8 of 50 holder rows.
Quick read
BlackRock, Inc. leads the comparable SEC ownership view at 6.6%.
50 of 50 rows have a safely comparable ownership percentage. Use this as a filing-backed starting point, then open the detailed table for source links, reporting role, position value, share count, and filing date.
Open SEC evidence
Opens BlackRock, Inc.'s linked filing trail.
Comparable ownership
Top 5
BlackRock, Inc.
6.6%
RA CAPITAL MANAGEMENT, L.P.
5.6%
PRICE T ROWE ASSOCIATES INC /MD/
9%
VANGUARD CAPITAL MANAGEMENT LLC
3.6%
TIG Advisors, LLC
3.5%
Ownership % is shown only when SEC disclosures are safely comparable across share classes.
Detailed SEC evidence table Showing 1-8 of 50 holder rows
| Holder | Evidence | Ownership % | Position | 12M Net Δ | As of |
|---|---|---|---|---|---|
| BlackRock, Inc. |
13F
13D/G
Company
|
6.6%
from 13D/G
|
$16,114,735
1,205,291 shares
|
— | 31 Mar 2026 |
| RA CAPITAL MANAGEMENT, L.P. |
13F
13D/G
Company
|
5.6%
from 13D/G
|
$11,553,044
864,102 shares
|
— | 31 Mar 2026 |
| PRICE T ROWE ASSOCIATES INC /MD/ |
13F
Company
|
9%
|
$20,767,000
1,553,210 shares
|
— | 31 Mar 2026 |
| VANGUARD CAPITAL MANAGEMENT LLC |
13F
Company
|
3.6%
|
$8,381,239
626,869 shares
|
— | 31 Mar 2026 |
| TIG Advisors, LLC |
13F
Company
|
3.5%
|
$8,122,970
607,552 shares
|
— | 31 Mar 2026 |
| Pentwater Capital Management LP |
13F
Company
|
3.5%
|
$8,057,417
602,649 shares
|
— | 31 Mar 2026 |
| O'Connor Alternative Investments LLC |
13F
Company
|
3.4%
|
$7,728,007
578,011 shares
|
— | 31 Mar 2026 |
| Sessa Capital IM, L.P. |
13F
Company
|
3.2%
|
$7,372,098
551,391 shares
|
— | 31 Mar 2026 |
How to read this table
Rows are grouped by holder and ranked first by SEC-reported ownership % when it is safely comparable, then by disclosed holdings value. — indicates unavailable or non-comparable values; "mixed-class rows" means the latest filing spans non-comparable classes.
Forms 3/4/5 flow
Insider trading overview
Insider buy and sell flow is broadly balanced over the last 12 months. No Buy or Sell transactions have been reported since 13 Aug 2025.
Buys
$0
Insiders: 0
Sells
$0
Insiders: 0
Net
$0
Shares: 0
Window
Last 12 months
4 rolling buckets
Buy value
Sell value
Shares: 0
Shares: 0
| Window (months) | Buy shares | Sell shares | Buy value | Sell value | Net value |
|---|---|---|---|---|---|
| 0-3 | 0 | 0 | $0 | $0 | $0 |
| 3-6 | 0 | 0 | $0 | $0 | $0 |
| 6-9 | 0 | 0 | $0 | $0 | $0 |
| 9-12 | 0 | 0 | $0 | $0 | $0 |
Reporting owners
Insider holders from Forms 3/4/5
Showing 1-11 of 11 reporting-owner rows connected to Atrium Therapeutics, Inc.. Open a relationship link for the CIK-to-CIK filing trail.
Rows
11
Largest Forms 3/4/5 holder
Kathleen P. Gallagher
Net 12M change
$0
Latest report
20 Apr 2026
| Name | Relationship | Holdings Value | Past Year Net Change | Change % | Valuation | Report Date |
|---|---|---|---|---|---|---|
| Kathleen P. Gallagher | Chief Executive Officer and President, Director | $1,756,309 | Mixed | 20 Apr 2026 | ||
| Steven George Hughes | Chief Medical Officer | $977,314 | Mixed | 20 Apr 2026 | ||
| Husam Younis | Chief Scientific Officer | $704,029 | Mixed | 20 Apr 2026 | ||
| Rocio Martin Hoyos | Chief Strategy Officer | $623,848 | Mixed | 20 Apr 2026 | ||
| Brendan R. Winslow | Chief Financial Officer | $582,949 | Mixed | 20 Apr 2026 | ||
| Stephanie Kenney | Chief Corporate Affairs Officer | $474,103 | Mixed | 20 Apr 2026 | ||
| Sarah Boyce | Director | Mixed | 27 Feb 2026 | |||
| Carsten Boess | Director | Mixed | 27 Feb 2026 | |||
| Troy E. Wilson | Director | Mixed | 27 Feb 2026 | |||
| W. Michael Flanagan | Director | Mixed | 27 Feb 2026 | |||
| Simona Skerjanec | Director | Mixed | 27 Feb 2026 |
Recent insider transactions for Atrium Therapeutics, Inc.
Showing up to 300 recent insider transactions from the last 12 months.
| Insider | Symbol | Class | Transaction | % | SEC-reported value | SEC-reported price | Shares | Shares owned | Date | Ownership |
|---|---|---|---|---|---|---|---|---|---|---|
| Stephanie Kenney | RNA | Common Stock | Award | 549.4% | 30,000 | 35,460 | 20 Apr 2026 | Direct | ||
| Stephanie Kenney | RNA | Stock Option (Right to Buy) | Award | 60,000 | 60,000 | 20 Apr 2026 | Direct | |||
| Steven George Hughes | RNA | Common Stock | Award | 69.6% | 30,000 | 73,097 | 20 Apr 2026 | Direct | ||
| Steven George Hughes | RNA | Stock Option (Right to Buy) | Award | 60,000 | 60,000 | 20 Apr 2026 | Direct | |||
| Brendan R. Winslow | RNA | Common Stock | Award | 220.6% | 30,000 | 43,601 | 20 Apr 2026 | Direct | ||
| Brendan R. Winslow | RNA | Stock Option (Right to Buy) | Award | 60,000 | 60,000 | 20 Apr 2026 | Direct | |||
| Kathleen P. Gallagher | RNA | Common Stock | Award | 355.2% | 102,500 | 131,361 | 20 Apr 2026 | Direct | ||
| Kathleen P. Gallagher | RNA | Stock Option (Right to Buy) | Award | 205,000 | 205,000 | 20 Apr 2026 | Direct | |||
| Rocio Martin Hoyos | RNA | Common Stock | Award | 180.1% | 30,000 | 46,660 | 20 Apr 2026 | Direct | ||
| Rocio Martin Hoyos | RNA | Stock Option (Right to Buy) | Award | 60,000 | 60,000 | 20 Apr 2026 | Direct | |||
| Husam Younis | RNA | Common Stock | Award | 132.4% | 30,000 | 52,657 | 20 Apr 2026 | Direct | ||
| Husam Younis | RNA | Stock Option (Right to Buy) | Award | 60,000 | 60,000 | 20 Apr 2026 | Direct | |||
| Sarah Boyce | Stock Option (Right to Buy) | Award | 20,000 | 20,000 | 27 Feb 2026 | Direct | ||||
| Carsten Boess | Stock Option (Right to Buy) | Award | 20,000 | 20,000 | 27 Feb 2026 | Direct | ||||
| Troy Edward Wilson | Stock Option (Right to Buy) | Award | 20,000 | 20,000 | 27 Feb 2026 | Direct | ||||
| W. Michael Flanagan | Stock Option (Right to Buy) | Award | 20,000 | 20,000 | 27 Feb 2026 | Direct | ||||
| Simona Skerjanec | Stock Option (Right to Buy) | Award | 20,000 | 20,000 | 27 Feb 2026 | Direct |
* marks a reported price that did not pass the local price check.