Institutional HoldersBeta

Who holds a company, from every 13F filed for the quarter, one row per filer exactly as filed, against the latest share count the company reported.

Atrium Therapeutics, Inc.

CIK 0002093101RNA· quarter ending 2026-06-30

Shares outstanding

17,105,643

as of 2026-08-03 · 10-Q cover page, filed 2026-08-13

Held by 13F filers

15,751,559

92.1% of shares outstanding

Holders

154

-9 vs 2026-03-31 · 39 new, 48 exited

Value

$211.9M

shares +6.2% vs prior quarter

Share classes (cover page of the 10-Q filed 2026-08-13, as of 2026-08-03)

Class	Listed	Shares outstanding	Held by 13F filers	% of class	Holders	CUSIP
Common stock	RNA · NASDAQ	17,105,643	15,751,559	92.1%	154	04965N104

Each class is compared with its own share count; classes are not added together. A class that is not exchange-listed cannot be held by 13F filers.

Securities (CUSIPs held in 13F this quarter)

tick to combine

Count	CUSIP	Class (as filers write it)	Holders	Shares held	Class shares	% of class	Value	Options	Mapped via
	04965N104	COM	154	15,751,559	17,105,643	92.1%	$211.9M	3 call / 3 put	13DG	holders →

Totals combine the ticked CUSIPs and update as you tick: common-stock classes by default; preferreds, notes, warrants and depositary shares are listed but not counted. "holders →" shows a single CUSIP on its own. Bonds are held as a principal amount, not shares. Options positions are never counted as holdings.

Top holders (154 of 154 · 04965N104)

change vs 2026-03-31

#	Filer	Shares	% of class	Value	Change
1	Sessa Capital IM, L.P.	1,500,000	8.77%	$20.2M	+948,609 (+172.0%)
2	PRICE T ROWE ASSOCIATES INC /MD/	1,472,984	8.61%	$19.8M	-80,226 (-5.2%)
3	BlackRock, Inc.	1,447,476	8.46%	$19.5M	+242,185 (+20.1%)
4	CRCM LP	1,283,078	7.50%	$17.3M	NEW
5	Arbiter Partners Capital Management LLC	783,864	4.58%	$10.5M	+553,864 (+240.8%)
6	VANGUARD CAPITAL MANAGEMENT LLC	730,831	4.27%	$9.8M	+103,962 (+16.6%)
7	TIG Advisors, LLC	561,533	3.28%	$7.6M	-46,019 (-7.6%)
8	CANTOR FITZGERALD, L. P.	513,834	3.00%	$6.9M	+278,197 (+118.1%)
9	GEODE CAPITAL MANAGEMENT, LLC	386,929	2.26%	$5.2M	+67,098 (+21.0%)
10	TWO SIGMA INVESTMENTS, LP	345,481	2.02%	$4.6M	+166,921 (+93.5%)
11	GOLDMAN SACHS GROUP INC	310,341	1.81%	$4.2M	-39,609 (-11.3%)
12	683 Capital Management, LLC	300,000	1.75%	$4.0M	—
13	STATE STREET CORP	271,762	1.59%	$3.7M	+14,676 (+5.7%)
14	Slotnik Capital, LLC	237,637	1.39%	$3.2M	+56,692 (+31.3%)
15	Weiss Asset Management LP	219,730	1.28%	$3.0M	-20,971 (-8.7%)
16	MILLENNIUM MANAGEMENT LLC	200,559	1.17%	$2.7M	+9,700 (+5.1%)
17	Schonfeld Strategic Advisors LLC	199,158	1.16%	$2.7M	+36,399 (+22.4%)
18	AQR CAPITAL MANAGEMENT LLC	172,235	1.01%	$2.3M	NEW
19	NEXPOINT ASSET MANAGEMENT, L.P.	150,025	0.88%	$2.0M	—
20	Polar Asset Management Partners Inc.	150,000	0.88%	$2.0M	+80,000 (+114.3%)
21	Squarepoint Ops LLC	146,743	0.86%	$2.0M	-84,723 (-36.6%)
22	Bracebridge Capital, LLC	139,239	0.81%	$1.9M	—
23	NOMURA HOLDINGS INC	137,394	0.80%	$1.8M	+14 (+0.0%)
24	Yakira Capital Management, Inc.	133,047	0.78%	$1.8M	+6,402 (+5.1%)
25	BANK OF AMERICA CORP /DE/	132,833	0.78%	$1.8M	-3,415 (-2.5%)
26	CHARLES SCHWAB INVESTMENT MANAGEMENT INC	130,217	0.76%	$1.8M	+13,619 (+11.7%)
27	TUDOR INVESTMENT CORP ET AL	129,591	0.76%	$1.7M	+58,232 (+81.6%)
28	DAFNA Capital Management LLC	128,000	0.75%	$1.7M	NEW
29	Creek Drive Management Group LLC	127,600	0.75%	$1.7M	+7,600 (+6.3%)
30	NORGES BANK	126,575	0.74%	$1.7M	NEW
31	Anson Funds Management LP	125,000	0.73%	$1.7M	NEW
32	NORTHERN TRUST CORP	119,781	0.70%	$1.6M	+21,196 (+21.5%)
33	ExodusPoint Capital Management, LP	117,275	0.69%	$1.6M	+39,833 (+51.4%)
34	Trium Capital LLP	113,278	0.66%	$1.5M	NEW
35	TD Asset Management Inc	111,200	0.65%	$1.5M	—
36	VANGUARD FIDUCIARY TRUST CO	109,961	0.64%	$1.5M	+14,833 (+15.6%)
37	JANE STREET GROUP, LLC	109,810	0.64%	$1.5M	+89,855 (+450.3%)
38	Athos Capital Ltd	107,965	0.63%	$1.5M	—
39	AWM Investment Company, Inc.	107,500	0.63%	$1.4M	+57,500 (+115.0%)
40	Balyasny Asset Management L.P.	105,875	0.62%	$1.4M	-129,240 (-55.0%)
41	Marble Bar Asset Management LLP	103,849	0.61%	$1.4M	-43,151 (-29.4%)
42	VANGUARD PORTFOLIO MANAGEMENT LLC	101,195	0.59%	$1.4M	-243,174 (-70.6%)
43	ADAGE CAPITAL PARTNERS GP, L.L.C.	100,000	0.58%	$1.3M	-83,580 (-45.5%)
44	BlueCrest Capital Management Ltd	100,000	0.58%	$1.3M	NEW
45	CREDIT INDUSTRIEL ET COMMERCIAL	89,723	0.52%	$1.2M	+66,723 (+290.1%)
46	Groupe la Francaise	80,273	0.47%	$1.1M	+50,575 (+170.3%)
47	FIL Ltd	76,500	0.45%	$1.0M	-2,000 (-2.5%)
48	Caption Management, LLC	75,277	0.44%	$1.0M	-28,315 (-27.3%)
49	CITADEL ADVISORS LLC	67,639	0.40%	$910K	-42,297 (-38.5%)
50	MANUFACTURERS LIFE INSURANCE COMPANY, THE	62,853	0.37%	$845K	+474 (+0.8%)
51	ADAR1 Capital Management, LLC	57,688	0.34%	$776K	—
52	FRANKLIN RESOURCES INC	56,699	0.33%	$763K	NEW
53	JACOBS LEVY EQUITY MANAGEMENT, INC	53,992	0.32%	$726K	NEW
54	ODDO BHF ASSET MANAGEMENT SAS	45,090	0.26%	$606K	—
55	CAXTON ASSOCIATES LLP	44,230	0.26%	$595K	—
56	ALETHEA CAPITAL MANAGEMENT, LLC	43,758	0.26%	$589K	—
57	CANADA PENSION PLAN INVESTMENT BOARD	41,970	0.25%	$564K	—
58	MORGAN STANLEY	41,942	0.25%	$564K	-123,094 (-74.6%)
59	Saba Capital Management, L.P.	39,640	0.23%	$533K	—
60	Bank of New York Mellon Corp	39,252	0.23%	$528K	-4,445 (-10.2%)
61	Y-Intercept (Hong Kong) Ltd	35,103	0.21%	$472K	NEW
62	KENNEDY CAPITAL MANAGEMENT LLC	34,979	0.20%	$470K	+1,002 (+2.9%)
63	FMR LLC	33,532	0.20%	$451K	+4,240 (+14.5%)
64	Moran Wealth Management, LLC	33,320	0.19%	$448K	NEW
65	BOUSSARD & GAVAUDAN GESTION SAS	32,845	0.19%	$447K	NEW
66	LMR Partners LLP	32,500	0.19%	$437K	—
67	LOS ANGELES CAPITAL MANAGEMENT LLC	31,477	0.18%	$423K	NEW
68	Nuveen, LLC	31,071	0.18%	$418K	+5,764 (+22.8%)
69	Jump Financial, LLC	31,017	0.18%	$417K	NEW
70	Quantinno Capital Management LP	27,418	0.16%	$369K	+14,964 (+120.2%)
71	Twin Securities, Inc.	26,517	0.16%	$357K	-23,396 (-46.9%)
72	Odyssean, LLC	21,233	0.12%	$286K	NEW
73	Brevan Howard Capital Management LP	20,834	0.12%	$280K	-10,810 (-34.2%)
74	Fractal Investments LLC	20,000	0.12%	$269K	—
75	UBS Group AG	19,572	0.11%	$263K	-30,242 (-60.7%)
76	HEALTHCARE OF ONTARIO PENSION PLAN TRUST FUND	18,590	0.11%	$250K	-2,000 (-9.7%)
77	Vestcor Inc	17,499	0.10%	$235K	—
78	WELLS FARGO & COMPANY/MN	17,451	0.10%	$235K	+6,035 (+52.9%)
79	ALLIANCEBERNSTEIN L.P.	17,110	0.10%	$229K	+4,140 (+31.9%)
80	RHUMBLINE ADVISERS	16,579	0.10%	$223K	+1,626 (+10.9%)
81	BLUEFIN CAPITAL MANAGEMENT, LLC	16,011	0.09%	$215K	NEW
82	RENAISSANCE TECHNOLOGIES LLC	14,971	0.09%	$201K	NEW
83	DEUTSCHE BANK AG\	14,967	0.09%	$201K	+4,948 (+49.4%)
84	Invesco Ltd.	14,174	0.08%	$191K	+3,981 (+39.1%)
85	Jupiter Topco LLC	13,833	0.08%	$186K	NEW
86	AlphaCentric Advisors LLC	13,478	0.08%	$181K	+192 (+1.4%)
87	AXQ CAPITAL, LP	11,377	0.07%	$153K	NEW
88	KESTRA PRIVATE WEALTH SERVICES, LLC	10,370	0.06%	$139K	NEW
89	MetLife Investment Management, LLC	10,283	0.06%	$138K	+1,438 (+16.3%)
90	Corsicana & Co.	9,820	0.06%	$132K	NEW
91	JPMORGAN CHASE & CO	9,388	0.05%	$128K	-2,650 (-22.0%)
92	BNP PARIBAS FINANCIAL MARKETS	7,901	0.05%	$106K	-366 (-4.4%)
93	CITIGROUP INC	6,685	0.04%	$90K	+6,047 (+947.8%)
94	MIRAE ASSET GLOBAL ETFS HOLDINGS Ltd.	6,602	0.04%	$89K	-2,886 (-30.4%)
95	Vanguard Global Advisers, LLC	5,585	0.03%	$75K	—
96	Russell Investments Group, Ltd.	4,475	0.03%	$60K	+636 (+16.6%)
97	Skandinaviska Enskilda Banken AB (publ)	4,400	0.03%	$59K	NEW
98	Walleye Trading LLC	3,978	0.02%	$54K	+350 (+9.6%)
99	Quantbot Technologies LP	3,614	0.02%	$49K	NEW
100	Erste Asset Management GmbH	3,600	0.02%	$49K	—
101	GROUP ONE TRADING LLC	3,575	0.02%	$48K	-107 (-2.9%)
102	Police & Firemen's Retirement System of New Jersey	3,175	0.02%	$43K	—
103	Arax Advisory Partners	3,128	0.02%	$42K	NEW
104	NEW YORK STATE COMMON RETIREMENT FUND	2,749	0.02%	$37K	—
105	BARCLAYS PLC	2,699	0.02%	$36K	+604 (+28.8%)
106	STRS OHIO	2,600	0.02%	$35K	—
107	Tower Research Capital LLC (TRC)	1,716	0.01%	$23K	-1,044 (-37.8%)
108	Legal & General Group Plc	1,422	0.01%	$19K	-4,235 (-74.9%)
109	Ameritas Investment Partners, Inc.	950	0.01%	$13K	—
110	Steward Partners Investment Advisory, LLC	635	0.00%	$9K	—
111	UBS AM, a distinct business unit of UBS ASSET MANAGEMENT AMERICAS LLC	612	0.00%	$8K	—
112	ROYAL BANK OF CANADA	600	0.00%	$8K	-35,098 (-98.3%)
113	PNC Financial Services Group, Inc.	594	0.00%	$8K	-349 (-37.0%)
114	Keating Financial Advisory Services, Inc.	531	0.00%	$7K	+528 (+17600.0%)
115	PenderFund Capital Management Ltd.	490	0.00%	$7K	—
116	Covestor Ltd	466	0.00%	$6K	+453 (+3484.6%)
117	Essential Partners LLC	288	0.00%	$4K	NEW
118	Eurizon Capital SGR S.p.A.	287	0.00%	$4K	—
119	Allworth Financial LP	281	0.00%	$4K	+227 (+420.4%)
120	Versant Capital Management, Inc	265	0.00%	$4K	NEW
121	FNY Investment Advisers, LLC	260	0.00%	$3K	NEW
122	EverSource Wealth Advisors, LLC	230	0.00%	$3K	+226 (+5650.0%)
123	True Wealth Design, LLC	213	0.00%	$3K	+212 (+21200.0%)
124	GAMMA Investing LLC	195	0.00%	$3K	-140 (-41.8%)
125	CALIFORNIA STATE TEACHERS RETIREMENT SYSTEM	171	0.00%	$2K	NEW
126	ROTHSCHILD INVESTMENT LLC	162	0.00%	$2K	+143 (+752.6%)
127	AdvisorNet Financial, Inc	139	0.00%	$2K	—
128	Sterling Capital Management LLC	125	0.00%	$2K	+25 (+25.0%)
129	Farther Finance Advisors, LLC	120	0.00%	$2K	NEW
130	LONGFELLOW INVESTMENT MANAGEMENT CO LLC	107	0.00%	$1K	—
131	NISA INVESTMENT ADVISORS, LLC	77	0.00%	$1K	-307 (-79.9%)
132	Private Wealth Management Group, LLC	75	0.00%	$1K	NEW
133	TD PRIVATE CLIENT WEALTH LLC	74	0.00%	$995	NEW
134	Basecamp Wealth Advisors LLC	56	0.00%	$753	-293 (-84.0%)
135	Fortitude Family Office, LLC	50	0.00%	$673	NEW
136	Zurcher Kantonalbank (Zurich Cantonalbank)	49	0.00%	$659	—
137	Avion Wealth	43	0.00%	$0	NEW
138	Wealth Enhancement Trust Services, Inc.	40	0.00%	$538	NEW
139	Bogart Wealth, LLC	39	0.00%	$525	NEW
140	Rockefeller Capital Management L.P.	39	0.00%	$525	-103 (-72.5%)
141	JONES FINANCIAL COMPANIES LLLP	29	0.00%	$383	—
142	Smartleaf Asset Management LLC	25	0.00%	$341	—
143	Global Retirement Partners, LLC	21	0.00%	$282	NEW
144	DANSKE BANK A/S	21	0.00%	$282	—
145	US BANCORP \DE\	13	0.00%	$175	-284 (-95.6%)
146	Clearstead Advisors, LLC	11	0.00%	$149	NEW
147	Pinnacle Wealth Planning Services, Inc.	10	0.00%	$135	-24 (-70.6%)
148	SJS Investment Consulting Inc.	9	0.00%	$122	NEW
149	JPL Wealth Management, LLC	6	0.00%	$81	NEW
150	OSAIC HOLDINGS, INC.	5	0.00%	$67	-53 (-91.4%)
151	Centerpoint Advisors, LLC	5	0.00%	$0	—
152	Torren Management, LLC	4	0.00%	$54	—
153	Parallel Advisors, LLC	2	0.00%	$27	-74 (-97.4%)
154	Truvestments Capital LLC	1	0.00%	$13	—

Exited since 2026-03-31 (48 filers; largest 25 shown)

RA CAPITAL MANAGEMENT, L.P.	−864,102
Pentwater Capital Management LP	−602,649
O'Connor Alternative Investments LLC	−578,011
FARALLON CAPITAL MANAGEMENT LLC	−349,360
Bellevue Group AG	−263,096
AQR Arbitrage LLC	−179,713
JANUS HENDERSON GROUP PLC	−139,973
NEUBERGER BERMAN GROUP LLC	−69,294
Quarry LP	−66,651
Westchester Capital Management, LLC	−55,236
HIGHBRIDGE CAPITAL MANAGEMENT LLC	−40,986
FIFTH LANE CAPITAL, LP	−35,999
MARSHALL WACE, LLP	−33,691
Woodline Partners LP	−28,845
Cannon Global Investment Management, LLC	−25,087
Point72 Asset Management, L.P.	−22,708
Fortress Investment Group LLC	−22,033
Grantham, Mayo, Van Otterloo & Co. LLC	−15,444
Susquehanna Portfolio Strategies, LLC	−13,110
Public Sector Pension Investment Board	−12,882
AlphaGrep UK Ltd	−11,870
SUSQUEHANNA INTERNATIONAL GROUP, LLP	−11,343
Magnetar Financial LLC	−10,512
Centiva Capital, LP	−5,895
DIADEMA PARTNERS LP	−2,512

Large holders from 13D/13G (latest per reporting person, last 2 years)

Filed when a holder crosses 5% or changes materially, so often more current than the quarter-end 13F. Percentages are the filer's own, against the share count they used.

Reporting person	Form	Filed	Event	Shares	% of class
John Petry	SCHEDULE 13G	2026-08-14	2026-06-30	1,500,000	8.8%
Peter Kolchinsky	SCHEDULE 13G/A	2026-08-14	2026-06-30	0	0%
RA Capital Healthcare Fund, L.P.	SCHEDULE 13G/A	2026-08-14	2026-06-30	0	0%
RA Capital Management, L.P.	SCHEDULE 13G/A	2026-08-14	2026-06-30	0	0%
Rajeev Shah	SCHEDULE 13G/A	2026-08-14	2026-06-30	0	0%
Sessa Capital IM, L.P.	SCHEDULE 13G	2026-08-14	2026-06-30	1,500,000	8.8%
T. Rowe Price Associates, Inc.	SCHEDULE 13G/A	2026-08-14	2026-06-30	1,472,984	8.6%
BlackRock, Inc.	SCHEDULE 13G/A	2026-07-27	2026-06-30	1,135,757	6.6%

Source: SEC Form 13F-HR information tables for the quarter ending 2026-06-30 (filed within 45 days of quarter end; amendments applied; values normalised to dollars), the share count from the company's latest 10-K/10-Q XBRL cover page, and Schedule 13D/13G filings. Each row is a legal 13F filer as filed — related entities (e.g. Vanguard's advisers) are not merged. Retail brokerage accounts are not reported on 13F, so the remainder is mostly retail and insiders.