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

Rhea-AI Filing Summary

Sionna Therapeutics (SION) — insider transaction update: The President & CEO, who also serves as a director, reported option exercises and corresponding open‑market sales under a Rule 10b5‑1 trading plan adopted on May 21, 2025.

On 10/15/2025, 14,775 shares were acquired via option exercise at $6.11 and sold the same day at a weighted average price of $31.1108. On 10/16/2025, 10,225 shares were acquired via option exercise at $6.11 and sold at a weighted average price of $31.4612, and an additional 200 shares were exercised at $6.11 and sold at $34. Following these transactions, common stock beneficially owned directly was 547,343 shares. Derivative holdings show 152,942 non‑qualified stock options beneficially owned following the reported transactions.

Insights

Corporate governance analyst

Routine Form 4 discloses planned option exercises and sales.

The filing lists the CEO’s exercises of non‑qualified stock options at $6.11 and same‑day sales at weighted average prices of $31.1108, $31.4612, and $34, executed under a Rule 10b5‑1 plan adopted on May 21, 2025. This plan mechanism allows pre‑scheduled trades.

The report updates holdings to 547,343 shares of common stock directly owned and 152,942 options remaining. As a routine insider transaction disclosure without stated corporate cash flows or strategic changes, the investment thesis impact is limited based on the provided excerpt.

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
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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).

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)
10/15/2025

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	10/15/2025		M(1)		14,775	A	$6.11	562,118	D
Common Stock	10/15/2025		S(1)		14,775	D	$31.1108(2)	547,343	D
Common Stock	10/16/2025		M(1)		10,225	A	$6.11	557,568	D
Common Stock	10/16/2025		S(1)		10,225	D	$31.4612(3)	547,343	D
Common Stock	10/16/2025		M(1)		200	A	$6.11	547,543	D
Common Stock	10/16/2025		S(1)		200	D	$34	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	10/15/2025		M(1)			14,775	(4)	03/01/2032	Common Stock	14,775	$0.0	163,367	D
Non-Qualified Stock Option (right to buy)	$6.11	10/16/2025		M(1)			10,225	(4)	03/01/2032	Common Stock	10,225	$0.0	153,142	D
Non-Qualified Stock Option (right to buy)	$6.11	10/16/2025		M(1)			200	(4)	03/01/2032	Common Stock	200	$0.0	152,942	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 $31.00 to $31.28, 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 $31.07 to $31.74, 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	10/17/2025
	** 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.
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FAQ

What did Sionna Therapeutics (SION) disclose in this Form 4?

The President & CEO reported option exercises at $6.11 and same‑day sales at weighted average prices of $31.1108, $31.4612, and $34.

Were the trades made under a Rule 10b5-1 plan for SION?

Yes. The filing states transactions were executed under a Rule 10b5‑1 plan adopted on May 21, 2025.

How many shares were involved on each day?

On 10/15/2025, 14,775 shares; on 10/16/2025, 10,225 shares plus an additional 200 shares.

What are the executive’s holdings after these transactions?

Direct common stock beneficially owned was 547,343 shares. Options beneficially owned were 152,942 non‑qualified stock options.

What option terms are disclosed for SION?

Options have an exercise price of $6.11 and an expiration date of 03/01/2032; vesting occurs in forty‑eight equal monthly installments following February 2, 2022.

How were the sale prices determined?

The filing notes weighted average prices, with underlying trades in ranges of $31.00–$31.28 and $31.07–$31.74 on the respective dates.