Atrium CSO has 11K shares withheld for taxes

Atrium Therapeutics’ chief scientific officer had shares withheld to cover taxes on RSU vesting, with a reported remaining direct stake of 41,441 shares.

Rhea-AI Filing Summary

Atrium Therapeutics, Inc. (RNA) reported that Chief Scientific Officer Younis Husam had 11,216 shares of common stock withheld on September 18, 2026 to satisfy tax withholding obligations tied to vesting restricted stock units. Following this tax-withholding disposition, he directly holds 41,441 shares of Atrium common stock.

Insider Trade Summary

Tax Withholding: 11,216 shares

Tax Withholding 1 txn

Insider Younis Husam

Role Chief Scientific Officer

Type	Security	Shares	Price	Value
Tax Withholding	Common Stock F1	11,216	$8.95	$100K

Holdings After Transaction: Common Stock — 41,441 shares (Direct)

Footnotes (1)

1. F1. Represents shares withheld by the Issuer to satisfy tax withholding obligations in connection with the vesting of restricted stock units.

Key Figures

Shares withheld for taxes: 11,216 shares Per-share value for withholding: $8.95 per share Shares held after transaction: 41,441 shares +1 more

4 metrics

Shares withheld for taxes 11,216 shares Shares of common stock withheld on September 18, 2026 to satisfy tax withholding obligations on RSU vesting

Per-share value for withholding $8.95 per share Value used for the tax-withholding disposition of 11,216 shares

Shares held after transaction 41,441 shares Direct holdings of Atrium Therapeutics common stock by Younis Husam following the transaction

Transactions for tax liability 1 transaction, 11,216 shares Form 4 summarizes one exercise-price-or-tax-liability-related transaction during the reported period

Key Terms

restricted stock units, tax withholding obligations, payment of tax liability by delivering or withholding securities

3 terms

restricted stock units financial

"in connection with the vesting of restricted stock units"

Restricted stock units are a type of company reward where employees are promised shares of stock, but they only fully own these shares after meeting certain conditions, like staying with the company for a set time. They matter because they can become valuable assets and are often used to motivate employees to help the company succeed.

tax withholding obligations financial

"shares withheld by the Issuer to satisfy tax withholding obligations"

payment of tax liability by delivering or withholding securities financial

"Payment of tax liability by delivering or withholding securities"

FAQ

AI-generated questions and answers. How Rhea-AI works. Not financial advice.

What insider transaction did Atrium Therapeutics (RNA) report for Younis Husam?

Atrium Therapeutics reported that Chief Scientific Officer Younis Husam had 11,216 shares of common stock withheld on September 18, 2026, as a payment of tax liability related to vesting restricted stock units, rather than an open-market sale.

At what price were the Atrium Therapeutics (RNA) shares withheld for taxes?

The shares were withheld at a value of $8.95 per share in connection with satisfying tax withholding obligations upon the vesting of restricted stock units, according to the Form 4 disclosure.

How many Atrium Therapeutics (RNA) shares does Younis Husam hold after this transaction?

After the tax-withholding disposition, Chief Scientific Officer Younis Husam directly holds 41,441 shares of Atrium Therapeutics common stock, as reported in the filing.

Was the Atrium Therapeutics (RNA) Form 4 transaction an open-market sale?

No. The Form 4 describes the transaction as a payment of tax liability by delivering or withholding securities in connection with vesting restricted stock units, not as an open-market sale or purchase.

Was the Atrium Therapeutics (RNA) Form 4 trade under a Rule 10b5-1 plan?

The filing’s Rule 10b5-1 checkbox is not affirmed, and no footnote states that the transaction was made under a Rule 10b5-1 trading plan.

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

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Available on EDGAR 09/22/2026 - 04:25 PM Accepted by SEC EDGAR 09/22/2026 - 04:24 PM Learn about SEC filing dates

SEC Form 4

FORM 4

UNITED STATES SECURITIES AND EXCHANGE COMMISSION
Washington, D.C. 20549

STATEMENT OF CHANGES IN BENEFICIAL OWNERSHIP

Filed pursuant to Section 16(a) of the Securities Exchange Act of 1934
or Section 30(h) of the Investment Company Act of 1940

OMB APPROVAL

OMB Number:			3235-0287
Estimated average burden
hours per response:			0.5

Check this box if no longer subject to Section 16. Form 4 or Form 5 obligations may continue. See Instruction 1(b).

Check this box to indicate that a transaction was made pursuant to a contract, instruction or written plan for the purchase or sale of equity securities of the issuer that is intended to satisfy the affirmative defense conditions of Rule 10b5-1(c). See Instruction 10.

1. Name and Address of Reporting Person^*

Younis Husam

(Last) (First) (Middle)

C/O ATRIUM THERAPEUTICS, INC.

10578 SCIENCE CENTER DRIVE, SUITE 125

(Street)

SAN DIEGO CALIFORNIA 92121

(City) (State) (Zip)

UNITED STATES

(Country)

2. Issuer Name and Ticker or Trading Symbol
Atrium Therapeutics, Inc. [ RNA ]

5. Relationship of Reporting Person(s) to Issuer
(Check all applicable)

	Director		10% Owner
X	Officer (give title below)		Other (specify below)
	Chief Scientific Officer

2a. Foreign Trading Symbol

3. Date of Earliest Transaction (Month/Day/Year)
09/18/2026

6. Individual or Joint/Group Filing (Check Applicable Line)

X	Form filed by One Reporting Person
	Form filed by More than One Reporting Person

4. If Amendment, Date of Original Filed (Month/Day/Year)

Table I - Non-Derivative Securities Acquired, Disposed of, or Beneficially Owned
1. Title of Security (Instr. 3)	2. Transaction Date (Month/Day/Year)	2A. Deemed Execution Date, if any (Month/Day/Year)	3. Transaction Code (Instr. 8)		4. Securities Acquired (A) or Disposed Of (D) (Instr. 3, 4 and 5)			5. Amount of Securities Beneficially Owned Following Reported Transaction(s) (Instr. 3 and 4)	6. Ownership Form: Direct (D) or Indirect (I) (Instr. 4)	7. Nature of Indirect Beneficial Ownership (Instr. 4)
			Code	V	Amount	(A) or (D)	Price
Common Stock	09/18/2026		F(1)		11,216	D	$8.95	41,441	D

Table II - Derivative Securities Acquired, Disposed of, or Beneficially Owned (e.g., puts, calls, warrants, options, convertible securities)
1. Title of Derivative Security (Instr. 3)	2. Conversion or Exercise Price of Derivative Security	3. Transaction Date (Month/Day/Year)	3A. Deemed Execution Date, if any (Month/Day/Year)	4. Transaction Code (Instr. 8)		5. Number of Derivative Securities Acquired (A) or Disposed of (D) (Instr. 3, 4 and 5)		6. Date Exercisable and Expiration Date (Month/Day/Year)		7. Title and Amount of Securities Underlying Derivative Security (Instr. 3 and 4)		8. Price of Derivative Security (Instr. 5)	9. Number of derivative Securities Beneficially Owned Following Reported Transaction(s) (Instr. 4)	10. Ownership Form: Direct (D) or Indirect (I) (Instr. 4)	11. Nature of Indirect Beneficial Ownership (Instr. 4)
				Code	V	(A)	(D)	Date Exercisable	Expiration Date	Title	Amount or Number of Shares

Explanation of Responses:

1. Represents shares withheld by the Issuer to satisfy tax withholding obligations in connection with the vesting of restricted stock units.

	/s/ Brendan Winslow, Attorney-in-Fact	09/22/2026
	** Signature of Reporting Person	Date
Reminder: Report on a separate line for each class of securities beneficially owned directly or indirectly.
* If the form is filed by more than one reporting person, see Instruction 4 (b)(v).
** Intentional misstatements or omissions of facts constitute Federal Criminal Violations See 18 U.S.C. 1001 and 15 U.S.C. 78ff(a).
Note: File three copies of this Form, one of which must be manually signed. If space is insufficient, see Instruction 6 for procedure.
Persons who respond to the collection of information contained in this form are not required to respond unless the form displays a currently valid OMB Number.
* Form 4: SEC 1474 (03-26)