Sessa Capital discloses 8.8% Atrium Therapeutics (RNA) ownership through managed funds

Rhea-AI Filing Summary

Sessa Capital IM, L.P. and John Petry report beneficial ownership of common stock of Atrium Therapeutics, Inc. They report beneficial ownership of 1,500,000 shares of common stock, representing 8.8% of the class, based on 17,105,643 shares outstanding as of May 5, 2026 as reported by the company. Voting and dispositive power over these shares is described as shared, with no sole voting or dispositive power reported. The shares are held by certain Sessa funds for which Sessa Capital IM, L.P. acts as investment manager, and Sessa Capital (Master), L.P. is identified as having the right to receive dividends or sale proceeds from more than 5% of the company’s common stock.

Key Figures

Shares beneficially owned: 1,500,000 shares Percent of class: 8.8% Shares outstanding baseline: 17,105,643 shares +1 more

4 metrics

Shares beneficially owned 1,500,000 shares Common stock of Atrium Therapeutics reported as beneficially owned by the reporting persons

Percent of class 8.8% Portion of Atrium Therapeutics common stock beneficially owned by the reporting persons

Shares outstanding baseline 17,105,643 shares Atrium Therapeutics common stock outstanding as of May 5, 2026

Ownership threshold exceeded 5% of class Sessa Capital (Master), L.P. has rights to dividends or proceeds from more than 5% of the class

Key Terms

beneficial owner, shared voting power, shared dispositive power, percent of class, +1 more

5 terms

beneficial owner regulatory

"The filing of this statement should not be construed as an admission that any Reporting Person is, for purposes of Section 13 of the Act, the beneficial owner"

A beneficial owner is the person who ultimately owns or controls a financial asset or property, even if their name isn't directly on official documents. Think of it like someone who secretly holds the keys to a safe deposit box—others may appear to have access, but the true owner is the one who benefits from what's inside. Identifying beneficial owners helps ensure transparency and prevent illegal activities like money laundering or fraud.

shared voting power financial

"Shared Voting Power 1,500,000.00"

Shared voting power occurs when two or more parties jointly have the right to vote or decide how a block of company shares is cast, like co-owners who must agree before moving a piece of furniture. Investors care because who controls voting rights affects board elections, major corporate decisions and takeover outcomes, and shared control can alter regulatory disclosures and the practical influence any holder has over a company’s direction and value.

shared dispositive power financial

"Shared Dispositive Power 1,500,000.00"

percent of class financial

"Percent of class: 8.8%"

Percent of class is the portion of a specific category of securities—such as a company’s common shares, preferred shares, or a bond series—that takes part in or approves a corporate action (vote, consent, tender, etc.). Investors watch this number because it reveals how much support or opposition exists within that particular shareholder group; like counting how many members of a club back a proposal, it can determine whether a plan passes or how influence is distributed.

Investment Company Act of 1940 regulatory

"A listing of the shareholders of an investment company registered under the Investment Company Act of 1940"

A U.S. federal law that sets the rulebook for pooled investment vehicles such as mutual funds, exchange-traded funds and similar money managers, requiring them to register with regulators, disclose holdings and fees, limit conflicts of interest, and follow governance standards. It matters to investors because these protections and transparency rules act like a referee and scoreboard, helping people compare funds, trust that managers follow fair practices, and spot hidden costs or risks.

FAQ

How much of Atrium Therapeutics, Inc. (RNA) does Sessa Capital IM, L.P. beneficially own?

Sessa Capital IM, L.P. reports beneficial ownership of 1,500,000 shares of Atrium Therapeutics common stock, representing 8.8% of the outstanding class, based on 17,105,643 shares outstanding as of May 5, 2026.

Who are the reporting persons in this Atrium Therapeutics (RNA) Schedule 13G?

The reporting persons are Sessa Capital IM, L.P. and John Petry. Sessa Capital IM, L.P. serves as investment manager to certain funds holding Atrium shares, and John Petry is the sole member and manager of Sessa Capital IM GP, LLC, the general partner of Sessa IM.

What voting power does Sessa Capital report over Atrium Therapeutics (RNA) shares?

The reporting persons disclose 0 shares with sole voting power and 1,500,000 shares with shared voting power. They also report 0 shares with sole dispositive power and 1,500,000 shares with shared dispositive power over Atrium common stock.

What percentage of Atrium Therapeutics (RNA) is used to calculate Sessa Capital’s 8.8% stake?

The 8.8% beneficial ownership is calculated using 17,105,643 shares of Atrium Therapeutics common stock outstanding as of May 5, 2026, as reported in the company’s Form 10-Q for the quarter ended March 31, 2026.

Which Sessa fund has rights to dividends or sale proceeds from Atrium Therapeutics (RNA) shares?

The filing states that Sessa Capital (Master), L.P., a Sessa fund, has the right to receive or direct the receipt of dividends or sale proceeds from more than 5% of Atrium Therapeutics’ common stock.

What is the relationship of John Petry to Sessa Capital IM, L.P. in the Atrium (RNA) filing?

John Petry is described as the sole member and manager of Sessa Capital IM GP, LLC, which is the general partner of Sessa Capital IM, L.P. He is a United States citizen and signs both as an individual and in this managerial capacity.

AI-generated analysis. How Rhea-AI works. Not financial advice.

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Available on EDGAR 08/14/2026 - 04:18 PM Accepted by SEC EDGAR 08/14/2026 - 04:07 PM Learn about SEC filing dates

SECURITIES AND EXCHANGE COMMISSION
Washington, D.C. 20549

SCHEDULE 13G

UNDER THE SECURITIES EXCHANGE ACT OF 1934

Atrium Therapeutics, Inc.

(Name of Issuer)

Common Stock, par value $0.001 per share

(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

Sessa Capital IM, L.P.

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

DELAWARE

Number of Shares Beneficially Owned by Each Reporting Person With:

5	Sole Voting Power 0.00
6	Shared Voting Power 1,500,000.00
7	Sole Dispositive Power 0.00
8	Shared Dispositive Power 1,500,000.00

9

Aggregate Amount Beneficially Owned by Each Reporting Person

1,500,000.00

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)

8.8 %

12

Type of Reporting Person (See Instructions)

IA, PN

SCHEDULE 13G

CUSIP Number(s): 04965N104

1

Names of Reporting Persons

John Petry

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

UNITED STATES

Number of Shares Beneficially Owned by Each Reporting Person With:

5	Sole Voting Power 0.00
6	Shared Voting Power 1,500,000.00
7	Sole Dispositive Power 0.00
8	Shared Dispositive Power 1,500,000.00

9

Aggregate Amount Beneficially Owned by Each Reporting Person

1,500,000.00

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)

8.8 %

12

Type of Reporting Person (See Instructions)

HC, IN

SCHEDULE 13G

Item 1.
(a)	Name of issuer: Atrium Therapeutics, Inc.
(b)	Address of issuer's principal executive offices: 10578 Science Center Drive, Suite 125, San Diego, CA, 92121.
Item 2.
(a)	Name of person filing: This statement is filed by: (i) Sessa Capital IM, L.P. ("Sessa IM"), which serves as the investment manager to certain investment funds and accounts (the "Sessa Funds"), with respect to shares of common stock, par value $0.001 per share ("Common Stock"), of Atrium Therapeutics, Inc., a Delaware corporation (the "Company"), held by the Sessa Funds; and (ii) John Petry, who serves as the sole member and manager of Sessa Capital IM GP, LLC ("Sessa IM GP"), the general partner of Sessa IM, with respect to the shares of Common Stock held by the Sessa Funds. The filing of this statement should not be construed as an admission that any Reporting Person is, for purposes of Section 13 of the Act, the beneficial owner of the securities reported herein.
(b)	Address or principal business office or, if none, residence: The address of the business office of each of the Reporting Persons and Sessa IM GP is 888 Seventh Avenue, 30th Floor, New York, NY 10019.
(c)	Citizenship: Sessa IM is a Delaware limited partnership. Sessa IM GP is a Delaware limited liability company. Mr. Petry is a United States citizen.
(d)	Title of class of securities: Common Stock, par value $0.001 per share
(e)	CUSIP Number(s): 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: The information required by Item 4(a) is set forth in Row 9 of the cover page for each of the Reporting Persons and is incorporated herein by reference. The percentage set forth in this Schedule 13G is calculated based upon an aggregate of 17,105,643 shares of Common Stock outstanding as of May 5, 2026, as reported in the Company's Quarterly Report on Form 10-Q for the quarterly period ended March 31, 2026, filed with the Securities and Exchange Commission on May 14, 2026.
(b)	Percent of class: 8.8%
(c)	Number of shares as to which the person has:
	(i) Sole power to vote or to direct the vote: The information required by Item 4(c)(i) is set forth in Row 5 of the cover page for each of the Reporting Persons and is incorporated herein by reference.
	(ii) Shared power to vote or to direct the vote: The information required by Item 4(c)(ii) is set forth in Row 6 of the cover page for each of the Reporting Persons and is incorporated herein by reference.
	(iii) Sole power to dispose or to direct the disposition of: The information required by Item 4(c)(iii) is set forth in Row 7 of the cover page for each of the Reporting Persons and is incorporated herein by reference.
	(iv) Shared power to dispose or to direct the disposition of: The information required by Item 4(c)(iv) is set forth in Row 8 of the cover page for each of the Reporting Persons and is incorporated herein by reference.
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.
	If any other person is known to have the right to receive or the power to direct the receipt of dividends from, or the proceeds from the sale of, such securities, a statement to that effect should be included in response to this item and, if such interest relates to more than 5 percent of the class, such person should be identified. A listing of the shareholders of an investment company registered under the Investment Company Act of 1940 or the beneficiaries of employee benefit plan, pension fund or endowment fund is not required. See Item 2(a). Sessa Capital (Master), L.P., a Sessa Fund, has the right to receive or the power to direct the receipt of dividends from, or the proceeds from the sale of, more than 5% of the Common Stock of the Company.
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.

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.

Sessa Capital IM, L.P.

Signature:	/s/ John Petry
Name/Title:	John Petry, Sole Member and Manager of Sessa Capital IM GP, LLC, its General Partner
Date:	08/14/2026

John Petry

Signature:	/s/ John Petry
Name/Title:	John Petry, Individually
Date:	08/14/2026

Exhibit Information

Exhibit 99.1: Joint Filing Agreement