[Form 4] Sionna Therapeutics, Inc. Insider Trading Activity

Rhea-AI Filing Summary

Sionna Therapeutics director and CEO Michael Cloonan reported option exercises and sales executed under a Rule 10b5-1 plan. On 08/26/2025 and 08/27/2025 he exercised options with a $6.11 exercise price covering 17,574 and 7,426 shares respectively. Those exercises increased exercisable option counts and were followed by sales of the same share amounts at weighted-average prices of $24.96 and $25.0086, reducing his direct holdings to 547,343 shares. The Form 4 notes the 10b5-1 plan was adopted May 21, 2025, and the underlying options vest monthly through March 1, 2032.

Positive

• Use of a documented Rule 10b5-1 trading plan (adopted May 21, 2025) provides procedural compliance and pre-clearance for sales
• Realized value from option exercises at a $6.11 strike while selling at ~ $25 per share
• Substantial retained ownership: reporting person still owns 547,343 shares after transactions
• Clear vesting schedule disclosed for options (monthly through March 1, 2032) aiding transparency

Negative

• Significant open-market sales (25,000 total shares sold across two days) reduced the reporting person's direct holdings
• Weighted-average sale prices disclosed only as ranges with commitment to provide per-trade details on request, limiting immediate granularity

Insights

Financial Analyst

TL;DR: Routine insider option exercises and plan-based sales; liquidity event but not a clear signal of material corporate change.

The filing documents option exercises at a $6.11 strike and contemporaneous open-market sales executed under a 10b5-1 plan at ~25.00 per share, crystallizing intrinsic value while retaining a large ownership stake (547,343 shares). This is a common executive liquidity action that increases realized compensation without indicating operational changes. No debt, revenue or guidance data are included to alter valuation models.

Corporate Governance Expert

TL;DR: Transactions follow a pre-established 10b5-1 plan and include standard vesting disclosures; governance practices appear compliant.

The report explicitly states the 10b5-1 plan adoption date and provides weighted-average sale price ranges and vesting schedule for options vesting monthly through 2032. The inclusion of an attorney-in-fact signature and clear disclosure of direct ownership supports regulatory compliance and transparency for insiders' trading activity.

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).

X

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^*

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)
08/26/2025

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	08/26/2025		M(1)		17,574	A	$6.11	564,917	D
Common Stock	08/26/2025		S(1)		17,574	D	$24.96(2)	547,343	D
Common Stock	08/27/2025		M(1)		7,426	A	$6.11	554,769	D
Common Stock	08/27/2025		S(1)		7,426	D	$25.0086(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	08/26/2025		M(1)			17,574	(4)	03/01/2032	Common Stock	17,574	$0.0	210,568	D
Non-Qualified Stock Option (right to buy)	$6.11	08/27/2025		M(1)			7,426	(4)	03/01/2032	Common Stock	7,426	$0.0	203,142	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 $24.75 to $25.49, inclusive. The Reporting Person undertakes to provide to the Issuer, any security holder 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 $24.80 to $25.32, inclusive. The Reporting Person undertakes to provide to the Issuer, any security holder 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	08/28/2025
	** 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.

FAQ

What insider transactions did Michael Cloonan report for SION?

He reported exercising options at a $6.11 strike for 17,574 shares (08/26/2025) and 7,426 shares (08/27/2025) and selling those shares under a 10b5-1 plan.

At what prices were the SION shares sold in the Form 4?

Sales were executed at weighted-average prices of $24.96 (range $24.75–$25.49) and $25.0086 (range $24.80–$25.32).

Did the filing indicate the trades were pre-planned?

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

How many SION shares does the reporting person own after these transactions?

The Form 4 reports 547,343 shares beneficially owned following the reported transactions.

What is the vesting schedule for the reported options?

The underlying options vest in 48 equal monthly installments following February 2, 2022, with an expiration noted as 03/01/2032.