Atrium Therapeutics Ownership | Who Owns Atrium Therapeutics?

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Atrium Therapeutics Ownership Summary

Atrium Therapeutics is owned by 9.78% institutional investors, 4.27% insiders, and 85.95% retail investors. Vanguard group is the largest institutional shareholder, holding 9.90% of RNA shares. Fidelity Growth Compy Commingled Pl S is the top mutual fund, with 4.27% of its assets in Atrium Therapeutics shares.

RNA Ownership Benchmark

Type	Name	% Inst	% Insiders	% Retail
Stock	Atrium Therapeutics	9.78%	4.27%	85.95%
Sector	Healthcare Stocks	35.58%	11.87%	52.55%
Industry	Biotech Stocks	35.75%	11.83%	52.41%

Institutional Shareholders

Top Institutional Shareholders by Total Shares

Holder	Shares	% Holding	Value
Vanguard group	13.65M	9.90%	$984.52M
Blackrock	8.62M	9.89%	$352.23M
Rtw investments, lp	11.37M	8.77%	$495.51M
Sessa capital im	551.39K	3.22%	$7.37M
Norges bank	3.05M	2.21%	$219.74M
Polar capital	2.80M	2.16%	$121.85M
Boxer capital	1.73M	1.98%	$70.56M
Cantor fitzgerald, l. p.	235.64K	1.38%	$3.15M
Arbiter partners capital management	230.00K	1.34%	$3.08M
T. rowe price investment management	1.40M	1.08%	$61.08M

Top Institutional Shareholders by % of Total Assets

Holder	Shares	% Assets	Value
Rtw investments, lp	11.37M	6.11%	$495.51M
Bioimpact capital	760.02K	5.42%	$33.11M
Boxer capital	1.73M	3.72%	$70.56M
Catalio capital management, lp	263.26K	2.12%	$11.47M
Arbiter partners capital management	230.00K	1.76%	$3.08M
Ecor1 capital	765.00K	1.60%	$33.33M
Stempoint capital lp	114.05K	1.00%	$4.97M
Eversept partners, lp	302.91K	0.91%	$13.20M
Cormorant asset management, lp	300.00K	0.90%	$13.07M
Palo alto investors lp	109.83K	0.89%	$4.79M

Top Buyers

Holder	Shares	% Assets	Change
Norges bank	3.05M	0.02%	3.05M
Blackrock	8.62M	0.01%	2.46M
Rtw investments, lp	11.37M	6.11%	1.75M
Polar capital	2.80M	0.59%	1.03M
Suvretta capital management	750.00K	0.84%	750.00K

Top Sellers

Holder	Shares	% Assets	Change
Blackrock funding, inc. /de	-	-	-12.85M
Ra capital management	-	-	-8.64M
Janus henderson group	-	-	-6.94M
Balyasny asset management	-	-	-6.04M
Pentwater capital management lp	-	-	-6.03M

New Positions

Holder	Shares	% Assets	Change	Value
Norges bank	3.05M	0.02%	3.05M	$219.74M
Suvretta capital management	750.00K	0.84%	750.00K	$32.68M
Artal group	655.55K	0.68%	655.55K	$26.78M
Baker bros. advisors lp	625.00K	0.20%	625.00K	$27.23M
Sessa capital im	551.39K	0.13%	551.39K	$7.37M

Sold Out

Holder	Change
Sjs investment consulting	-1.00
Mai capital management	-1.00
Massmutual trust co fsb/adv	-1.00
American capital advisory	-1.00
Dinuzzo private wealth	-1.00

Institutional Ownership Trends

Date	Holdings	Change %	Shares	Change %	Ownership	Change %	Increased Position	Change %	Decreased Position	Change %
Mar 31, 2026	53	-85.40%	1,674,179	-98.81%	9	0.00%	13	-94.20%	38	-56.32%
Dec 31, 2025	226	-23.39%	67,965,698	-57.78%	49	0.32%	133	-34.48%	57	1.79%
Sep 30, 2025	164	-23.72%	64,667,711	-52.44%	49	0.45%	117	6.36%	37	-51.32%
Jun 30, 2025	214	-6.96%	135,949,346	3.28%	104	1.01%	109	-16.15%	76	16.92%
Mar 31, 2025	231	-7.23%	133,386,370	4.47%	103	0.96%	130	-7.14%	65	-12.16%

Top Mutual Funds Shareholders

Holder	Shares	% Holding	Change
Fidelity Growth Compy Commingled Pl S	5.49M	4.27%	109.14K
Fidelity Growth Compy Commingled Pl O	4.86M	4.11%	-69.00K
US Small-Cap Growth II Equity Comp	3.95M	3.28%	-484.27K
Fidelity Growth Company Fund	3.99M	3.10%	77.74K
Vanguard US Total Market Shares ETF	3.53M	2.93%	3.12K
Vanguard Total Stock Mkt Idx Inv	4.54M	2.92%	10.44K
T. Rowe Price New Horizons	3.54M	2.75%	-414.46K
Vanguard Health Care Inv	2.83M	2.35%	-196.40K
Vanguard Small Cap Index	3.25M	2.09%	3.86K
iShares Russell 2000 ETF	2.77M	1.79%	2.77M

Recent Insider Transactions

Date	Name	Role	Activity	Value
Jan 21, 2026	Hughes Steven George	Chief Medical Officer	Sell	$208.51K
Jan 21, 2026	Hughes Steven George	Chief Medical Officer	Sell	$146.13K
Jan 21, 2026	Boyce Sarah	President and CEO	Sell	$463.25K
Jan 21, 2026	Boyce Sarah	President and CEO	Sell	$579.09K
Jan 21, 2026	Flanagan W. Michael	Chief Scientific Officer	Sell	$288.06K

Insider Transactions Trends

Date	Buy	Sell
2026 Q1	-	18
2025 Q4	-	3
2025 Q3	-	23
2025 Q2	-	5
2025 Q1	-	23

RNA Ownership FAQ

Who Owns Atrium Therapeutics?

Atrium Therapeutics shareholders are primarily institutional investors at 9.78%, followed by 4.27% insiders and 85.95% retail investors. The average institutional ownership in Atrium Therapeutics's industry, Biotech Stocks , is 35.75%, which Atrium Therapeutics falls below.

Who owns the most shares of Atrium Therapeutics?

Atrium Therapeutics’s largest shareholders are Vanguard group (13.65M shares, 9.90%), Blackrock (8.62M shares, 9.89%), and Rtw investments, lp (11.37M shares, 8.77%). Together, they hold 28.56% of Atrium Therapeutics’s total shares outstanding.

Does Blackrock own Atrium Therapeutics?

Yes, BlackRock owns 9.89% of Atrium Therapeutics, totaling 8.62M shares as of Jun 2024. This represents 0.01% of BlackRock's total assets, with a market value of 352.23M$. In the last quarter, BlackRock increased its holdings by 2.46M shares, a 39.84% change.

Who is Atrium Therapeutics’s biggest shareholder by percentage of total assets invested?

Rtw investments, lp is Atrium Therapeutics’s biggest shareholder by percentage of total assets invested, with 6.11% of its assets in 11.37M Atrium Therapeutics shares, valued at 495.51M$.

Who is the top mutual fund holder of Atrium Therapeutics shares?

Fidelity Growth Compy Commingled Pl S is the top mutual fund holder of Atrium Therapeutics shares, with 4.27% of its total shares outstanding invested in 5.49M Atrium Therapeutics shares.

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