SION Form 4: Michael Cloonan Executes Options, Sells Shares Under 10b5-1 Plan

Rhea-AI Filing Summary

Michael Cloonan, President & CEO and Director of Sionna Therapeutics, Inc. (SION), reported option exercises and concurrent sales executed under a Rule 10b5-1 trading plan adopted May 21, 2025. On 09/26/2025 he exercised 17,207 non-qualified stock options at an exercise price of $6.11 and sold 17,207 shares at a weighted average price of $28.8456, bringing beneficial ownership to 564,550 then 547,343 after the sale. On 09/29/2025 he exercised 7,793 options at $6.11 and sold 7,793 shares at a weighted average price of $29.6999, leaving total beneficial ownership at 547,343. The options vest monthly in 48 equal installments following February 2, 2022, and carry an expiration/other date listed as 03/01/2032. The Form 4 was signed by an attorney-in-fact on 09/30/2025.

Insights

Corporate Governance Expert

TL;DR: Insider exercised options and sold shares under a pre-established 10b5-1 plan; disclosure appears complete and standard.

The filing shows the CEO and director executed option exercises and parallel sales using a Rule 10b5-1 plan adopted May 21, 2025, which typically limits claims of opportunistic trading. The Form 4 discloses weighted average sale prices and undertakes to provide detailed per-trade pricing on request, which supports transparency. Vesting terms are disclosed as 48 monthly installments following February 2, 2022, and the options reference a 03/01/2032 date. From a governance perspective, the filing meets Section 16 disclosure requirements and was executed via an attorney-in-fact, indicating administrative handling consistent with routine insider reporting.

Securities Analyst

TL;DR: CEO sold a total of 25,000 shares through plan-based transactions; transactions and prices are disclosed but no operational financial data provided.

The report documents exercises of 17,207 and 7,793 options and corresponding sales at weighted average prices of $28.8456 and $29.6999, respectively. Beneficial ownership after the transactions is reported as 547,343 shares. While insider selling can be noted by investors, these sales were executed under a pre-existing 10b5-1 plan and the filing contains specific prices and quantities rather than vague statements, which aids analytical transparency. The document contains no revenue, earnings, or other operational metrics, so impact assessment is limited to ownership and transaction disclosure.

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

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

1. Name and Address of Reporting Person^*

Cloonan Michael

(Last) (First) (Middle)

C/O SIONNA THERAPEUTICS, INC.

21 HICKORY DRIVE, SUITE 500

(Street)

WALTHAM MA 02451

(City) (State) (Zip)

2. Issuer Name and Ticker or Trading Symbol
Sionna Therapeutics, Inc. [ SION ]

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

X	Director		10% Owner
X	Officer (give title below)		Other (specify below)
	President & CEO

3. Date of Earliest Transaction (Month/Day/Year)
09/26/2025

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

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

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

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	09/26/2025		M(1)		17,207	A	$6.11	564,550	D
Common Stock	09/26/2025		S(1)		17,207	D	$28.8456(2)	547,343	D
Common Stock	09/29/2025		M(1)		7,793	A	$6.11	555,136	D
Common Stock	09/29/2025		S(1)		7,793	D	$29.6999(3)	547,343	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
Non-Qualified Stock Option (right to buy)	$6.11	09/26/2025		M(1)			17,207	(4)	03/01/2032	Common Stock	17,207	$0.0	185,935	D
Non-Qualified Stock Option (right to buy)	$6.11	09/29/2025		M(1)			7,793	(4)	03/01/2032	Common Stock	7,793	$0.0	178,142	D

Explanation of Responses:

1. This transaction was automatically executed pursuant to a Rule 10b5-1 trading plan adopted on May 21, 2025.

2. The price reported in Column 4 is a weighted average price. The shares were sold in multiple transactions at prices ranging from $28.75 to $28.95, inclusive. The Reporting Person undertakes to provide to the Issuer, any securityholder of the Issuer or the staff of the Securities and Exchange Commission, upon request, full information regarding the number of shares sold at each separate price at which the transactions were effected.

3. The price reported in Column 4 is a weighted average price. The shares were sold in multiple transactions at prices ranging from $28.83 to $29.95, inclusive. The Reporting Person undertakes to provide to the Issuer, any securityholder of the Issuer or the staff of the Securities and Exchange Commission, upon request, full information regarding the number of shares sold at each separate price at which the transactions were effected.

4. The shares underlying this option vest in forty-eight equal monthly installments following February 2, 2022, subject to the Reporting Person's continued service on each such vesting date.

	Jennifer Fitzpatrick, Attorney-in-Fact	09/30/2025
	** Signature of Reporting Person	Date
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FAQ

What did SION CEO Michael Cloonan report on Form 4?

The report discloses that Michael Cloonan exercised 17,207 options on 09/26/2025 and 7,793 options on 09/29/2025, and sold the corresponding shares under a 10b5-1 trading plan at weighted average prices of $28.8456 and $29.6999.

How many SION shares does Michael Cloonan beneficially own after these transactions?

Following the reported transactions, the Form 4 shows total beneficial ownership of 547,343 shares.

Were these trades part of a trading plan?

Yes. The filing states the transactions were automatically executed pursuant to a Rule 10b5-1 trading plan adopted on May 21, 2025.

What were the option exercise terms disclosed?

The non-qualified stock options were exercisable at $6.11. The options vest in 48 equal monthly installments following February 2, 2022, and reference 03/01/2032 in the filing.

Who signed the Form 4?

The Form 4 was signed by Jennifer Fitzpatrick, Attorney-in-Fact on 09/30/2025.