T. Rowe Price Associates (RNA) discloses 8.6% Atrium Therapeutics ownership in 13G/A

Rhea-AI Filing Summary

T. Rowe Price Associates, Inc. filed an amended Schedule 13G reporting beneficial ownership of 1,472,984 shares of Atrium Therapeutics Inc. common stock, representing 8.6% of the class. It reports sole voting power over 1,472,772 shares and sole dispositive power over 1,472,984 shares, with no shared voting or dispositive power.

The filer states that this report should not be construed as an admission that it is the beneficial owner of these securities, and such beneficial ownership is expressly denied.

Key Figures

Shares beneficially owned: 1,472,984 shares Percent of class: 8.6% Sole voting power: 1,472,772 shares +1 more

4 metrics

Shares beneficially owned 1,472,984 shares Amount beneficially owned by T. Rowe Price Associates, Inc.

Percent of class 8.6% Percentage of Atrium Therapeutics common stock reported owned

Sole voting power 1,472,772 shares Shares over which T. Rowe Price has sole power to vote

Sole dispositive power 1,472,984 shares Shares over which T. Rowe Price has sole power to dispose

Key Terms

beneficially owned, sole power to vote or to direct the vote, sole power to dispose or to direct the disposition of, Schedule 13G

4 terms

beneficially owned financial

"Amount beneficially owned: 1472984"

Beneficially owned describes securities or assets where a person has the economic rights and control—such as the right to receive dividends and to direct voting—even if legal title is held in another name. Think of it like having the keys and using a car that’s registered to someone else: you get the benefits and make decisions. Investors care because beneficial ownership reveals who truly controls value and voting power, affecting corporate decisions and takeover dynamics.

sole power to vote or to direct the vote financial

"Number of shares as to which the person has | (i) Sole power to vote or to direct the vote"

sole power to dispose or to direct the disposition of financial

"(iii) Sole power to dispose or to direct the disposition of: 1472984"

Schedule 13G regulatory

"T. Rowe Price Associates, Inc. filed an amended Schedule 13G"

A Schedule 13G is a formal document that investors file with the government when they acquire a large ownership stake in a company, usually for investment purposes rather than control. It helps keep the public informed about who owns significant parts of a company's shares, which can influence how the company is managed and how investors make decisions. Filing this schedule is important for transparency and understanding the ownership landscape of publicly traded companies.

FAQ

What ownership stake in Atrium Therapeutics (RNA) does T. Rowe Price report in this Schedule 13G/A?

T. Rowe Price Associates, Inc. reports beneficial ownership of 1,472,984 shares of Atrium Therapeutics Inc. common stock, representing 8.6% of the outstanding class as disclosed in the amended Schedule 13G.

How much voting power does T. Rowe Price have in Atrium Therapeutics (RNA)?

T. Rowe Price Associates, Inc. reports sole voting power over 1,472,772 shares of Atrium Therapeutics common stock and no shared voting power, indicating all reported voting authority is held on a sole basis.

What dispositive power over Atrium Therapeutics (RNA) shares does T. Rowe Price disclose?

The filer discloses sole dispositive power over 1,472,984 shares of Atrium Therapeutics common stock and no shared dispositive power, meaning decisions to sell or otherwise dispose are reported as held solely.

Does T. Rowe Price admit beneficial ownership of Atrium Therapeutics (RNA) shares in this filing?

No. T. Rowe Price Associates, Inc. states that this filing shall not be construed as an admission of beneficial ownership of the reported securities and that such beneficial ownership is expressly denied.

What class of securities in Atrium Therapeutics (RNA) is covered by this Schedule 13G/A?

The filing covers Atrium Therapeutics Inc. common stock, identified with CUSIP 04965N104, and details T. Rowe Price Associates, Inc.’s reported ownership and related voting and dispositive powers over this class.

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Available on EDGAR 08/14/2026 - 10:39 AM Accepted by SEC EDGAR 08/14/2026 - 10:38 AM Learn about SEC filing dates

SECURITIES AND EXCHANGE COMMISSION
Washington, D.C. 20549

SCHEDULE 13G

UNDER THE SECURITIES EXCHANGE ACT OF 1934

(Amendment No. 1)

ATRIUM THERAPEUTICS INC

(Name of Issuer)

COMMON STOCK

(Title of Class of Securities)

04965N104

(CUSIP Number)

06/30/2026

(Date of Event Which Requires Filing of this Statement)

Check the appropriate box to designate the rule pursuant to which this Schedule is filed:

Rule 13d-1(b)

Rule 13d-1(c)

Rule 13d-1(d)

schemaVersion:

SCHEDULE 13G

CUSIP Number(s): 04965N104

1

Names of Reporting Persons

T. Rowe Price Associates, Inc.

2

Check the appropriate box if a member of a Group (see instructions)

(a)
(b)

3

Sec Use Only

4

Citizenship or Place of Organization

MARYLAND

Number of Shares Beneficially Owned by Each Reporting Person With:

5	Sole Voting Power 1,472,772.00
6	Shared Voting Power 0.00
7	Sole Dispositive Power 1,472,984.00
8	Shared Dispositive Power 0.00

9

Aggregate Amount Beneficially Owned by Each Reporting Person

1,472,984.00

10

Check box if the aggregate amount in row (9) excludes certain shares (See Instructions)

11

Percent of class represented by amount in row (9)

8.6 %

12

Type of Reporting Person (See Instructions)

IA

SCHEDULE 13G

Item 1.
(a)	Name of issuer: ATRIUM THERAPEUTICS INC
(b)	Address of issuer's principal executive offices: 3020 CALLAN ROAD, SAN DIEGO, CA, 92121
Item 2.
(a)	Name of person filing: T. Rowe Price Associates, Inc.
(b)	Address or principal business office or, if none, residence: 1307 Point Street, Baltimore, MD 21231
(c)	Citizenship: Maryland
(d)	Title of class of securities: COMMON STOCK
(e)	CUSIP No.: 04965N104
Item 3.	If this statement is filed pursuant to §§ 240.13d-1(b) or 240.13d-2(b) or (c), check whether the person filing is a:
(a)	Broker or dealer registered under section 15 of the Act (15 U.S.C. 78o);
(b)	Bank as defined in section 3(a)(6) of the Act (15 U.S.C. 78c);
(c)	Insurance company as defined in section 3(a)(19) of the Act (15 U.S.C. 78c);
(d)	Investment company registered under section 8 of the Investment Company Act of 1940 (15 U.S.C. 80a-8);
(e)	An investment adviser in accordance with § 240.13d-1(b)(1)(ii)(E);
(f)	An employee benefit plan or endowment fund in accordance with § 240.13d-1(b)(1)(ii)(F);
(g)	A parent holding company or control person in accordance with § 240.13d-1(b)(1)(ii)(G);
(h)	A savings associations as defined in Section 3(b) of the Federal Deposit Insurance Act (12 U.S.C. 1813);
(i)	A church plan that is excluded from the definition of an investment company under section 3(c)(14) of the Investment Company Act of 1940 (15 U.S.C. 80a-3);
(j)	A non-U.S. institution in accordance with § 240.13d-1(b)(1)(ii)(J). If filing as a non-U.S. institution in accordance with § 240.13d-1(b)(1)(ii)(J), please specify the type of institution:
(k)	Group, in accordance with Rule 240.13d-1(b)(1)(ii)(K).
Item 4.	Ownership
(a)	Amount beneficially owned: 1472984
(b)	Percent of class: 8.6 %
(c)	Number of shares as to which the person has:
	(i) Sole power to vote or to direct the vote: 1472772
	(ii) Shared power to vote or to direct the vote: 0
	(iii) Sole power to dispose or to direct the disposition of: 1472984
	(iv) Shared power to dispose or to direct the disposition of: 0
Item 5.	Ownership of 5 Percent or Less of a Class.
	Not Applicable
Item 6.	Ownership of more than 5 Percent on Behalf of Another Person.
	Not Applicable
Item 7.	Identification and Classification of the Subsidiary Which Acquired the Security Being Reported on by the Parent Holding Company or Control Person.
	Not Applicable
Item 8.	Identification and Classification of Members of the Group.
	Not Applicable
Item 9.	Notice of Dissolution of Group.
	Not Applicable

Item 10.

Certifications:

By signing below I certify that, to the best of my knowledge and belief, the securities referred to above were acquired and are held in the ordinary course of business and were not acquired and are not held for the purpose of or with the effect of changing or influencing the control of the issuer of the securities and were not acquired and are not held in connection with or as a participant in any transaction having that purpose or effect, other than activities solely in connection with a nomination under § 240.14a-11. T. Rowe Price Associates, Inc. hereby declares and affirms that the filing of Schedule 13G shall not be construed as an admission that Price Associates is the beneficial owner of the securities referred to, which beneficial ownership is expressly denied.

SIGNATURE

After reasonable inquiry and to the best of my knowledge and belief, I certify that the information set forth in this statement is true, complete and correct.

T. Rowe Price Associates, Inc.

Signature:	Ellen York
Name/Title:	Vice President
Date:	08/14/2026