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

Rhea-AI Filing Summary

Sionna Therapeutics (SION) President & CEO (also a Director) reported option exercises and open‑market sales on 10/21/2025 under a pre‑established Rule 10b5‑1 trading plan adopted on May 21, 2025.

The executive exercised non‑qualified stock options at $6.11 per share and sold the resulting shares at weighted average prices of $34.44, $35.63, $36.60, and $37.31 (each comprising multiple trades within stated ranges). Following these transactions, the reporting person directly owned 547,343 shares. The options exercised were from grants expiring on March 1, 2032, with vesting in forty‑eight equal monthly installments following February 2, 2022.

Insights

Corporate governance analyst

Routine Form 4 showing 10b5-1 plan sales after option exercises.

The CEO executed multiple M-to-S pairs: exercising options at $6.11 and selling shares at weighted average prices up to $37.31. The filing cites a Rule 10b5-1 trading plan adopted on May 21, 2025, indicating pre-arranged instructions.

These are insider transactions at the individual level and do not reflect capital inflows or outflows for Sionna Therapeutics. The filing states direct common stock ownership of 547,343 shares after the trades. Option grants referenced expire on 03/01/2032 and vest in monthly installments following 02/02/2022.

Actual market impact, if any, depends on trade size relative to daily liquidity; the excerpt provides prices and dates but not volumes beyond the listed line items.

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)
10/21/2025

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	10/21/2025		M(1)		13,324	A	$6.11	560,667	D
Common Stock	10/21/2025		S(1)		13,324	D	$34.44(2)	547,343	D
Common Stock	10/21/2025		M(1)		30,049	A	$6.11	577,392	D
Common Stock	10/21/2025		S(1)		30,049	D	$35.63(3)	547,343	D
Common Stock	10/21/2025		M(1)		22,895	A	$6.11	570,238	D
Common Stock	10/21/2025		S(1)		22,895	D	$36.6(4)	547,343	D
Common Stock	10/21/2025		M(1)		33,532	A	$6.11	580,875	D
Common Stock	10/21/2025		S(1)		33,532	D	$37.31(5)	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	10/21/2025		M(1)			13,324	(6)	03/01/2032	Common Stock	13,324	$0.0	139,618	D
Non-Qualified Stock Option (right to buy)	$6.11	10/21/2025		M(1)			30,049	(6)	03/01/2032	Common Stock	30,049	$0.0	109,569	D
Non-Qualified Stock Option (right to buy)	$6.11	10/21/2025		M(1)			22,895	(6)	03/01/2032	Common Stock	22,895	$0.0	86,674	D
Non-Qualified Stock Option (right to buy)	$6.11	10/21/2025		M(1)			33,532	(6)	03/01/2032	Common Stock	33,532	$0.0	53,142	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 $34.00 to $34.95, 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 $35.00 to $35.99, 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 price reported in Column 4 is a weighted average price. The shares were sold in multiple transactions at prices ranging from $36.00 to $36.99, 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.

5. The price reported in Column 4 is a weighted average price. The shares were sold in multiple transactions at prices ranging from $37.00 to $37.80, 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.

6. 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	10/22/2025
	** 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 did SION’s CEO report on the Form 4 dated 10/21/2025?

Option exercises at $6.11 followed by open‑market sales at weighted average prices of $34.44, $35.63, $36.60, and $37.31.

Was the SION insider trading under a Rule 10b5-1 plan?

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

How many SION shares did the reporting person own after the transactions?

The filing shows 547,343 shares of common stock directly owned after the reported transactions.

What were the sale price ranges noted in the Form 4 footnotes for SION?

Weighted average sales included ranges of $34.00–$34.95, $35.00–$35.99, $36.00–$36.99, and $37.00–$37.80.

What was the exercise price and option term referenced for SION options?

Non‑qualified options were exercised at $6.11 per share and have an expiration date of 03/01/2032.

How do the SION options vest according to the filing?

They vest in 48 equal monthly installments following February 2, 2022, subject to continued service.