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

Sionna CEO exercises options and sells 25,000 shares

Sionna Therapeutics, Inc. President & CEO Michael Cloonan reported an option exercise and share sale on August 20, 2025.

Filing Impact
(Very High)
Filing Sentiment
(Negative)
Form Type
4

Rhea-AI Filing Summary

Sionna Therapeutics, Inc. President & CEO Michael Cloonan reported an option exercise and share sale on August 20, 2025. He exercised Non-Qualified Stock Options into 25,000 common shares at $6.11 per share, then sold 25,000 common shares at a reported price of $22.75 per share. After these transactions he directly holds 547,343 common shares. Footnotes describe a Rule 10b5-1 trading plan adopted on May 21, 2025 and note that a reported sale price reflects a weighted average of multiple trades between $21.07 and $23.99.

Positive

  • None.

Negative

  • None.

Insights

TL;DR: CEO exercised options at $6.11 and sold the same number of shares under a 10b5-1 plan; net ownership declined modestly.

These paired transactions—an exercise of 25,000 option shares and a contemporaneous sale of 25,000 common shares—are executed under an established 10b5-1 plan, which indicates pre-arranged trading rather than opportunistic insider timing. The exercise price of $6.11 is materially lower than the weighted average sale price of $22.75, generating a cash difference before taxes and fees. Reported beneficial ownership after the sale is 547,343 common shares with 228,142 shares underlying outstanding options. For investors, this filing documents insider liquidity but not a change in strategic control; the magnitude (25,000 shares) should be assessed relative to total outstanding shares for materiality.

TL;DR: Transactions followed a documented 10b5-1 plan; filing includes standard disclosures and vesting schedule for options.

The Form 4 discloses that the trading activity was implemented under a 10b5-1 plan adopted on 05/21/2025, which provides the reporting person with an affirmative defense under Rule 10b5-1(c). The filing also supplies vesting terms for the exercised option (forty-eight equal monthly installments beginning 02/02/2022) and provides a weighted-average sale price range for the disposed shares. Signature via attorney-in-fact and the explanatory note about providing per-price sale details comply with common disclosure practices. No other governance concerns or departures are stated in the document.

Insider Cloonan Michael
Role President & CEO
Sold 25,000 shs ($569K)
Approx. gross sale proceeds $569K
Approx. exercise cost $153K
Approx. pre-tax spread $416K
Type Security Shares Price Value
Exercise Non-Qualified Stock Option (right to buy) 25,000 $0.00 $0.00
Exercise Common Stock 25,000 $6.11 $153K
Sale Common Stock 25,000 $22.75 $569K
Holdings After Transaction: Non-Qualified Stock Option (right to buy) — 228,142 contracts (Direct); Common Stock — 547,343 shares (Direct)
Footnotes (3)
  1. F1. This transaction was automatically executed pursuant to a Rule 10b5-1 trading plan adopted on May 21, 2025.
  2. F2. The price reported in Column 4 is a weighted average price. The shares were sold in multiple transactions at prices ranging from $21.0700 to $23.99, 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. F3. 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.
Options Exercised 25,000 shares Non-Qualified Stock Options exercised into common stock on August 20, 2025
Exercise Price $6.1100 per share Exercise price for options converted into 25,000 common shares
Shares Sold 25,000 shares Common stock sale reported on August 20, 2025
Sale Price (Weighted Average) $22.7500 per share Weighted-average sale price; trades ranged from $21.0700 to $23.99
Price Range of Sales $21.0700–$23.99 per share Footnotes describe multiple sale transactions within this range
Post-Transaction Holdings 547,343 shares Direct common stock holdings after reported transactions
Option Expiration 2032-03-01 Expiration date of exercised Non-Qualified Stock Option
Non-Qualified Stock Option financial
"Security title listed as Non-Qualified Stock Option (right to buy)"
A non-qualified stock option (NSO) is a contract that lets an employee or service provider buy company shares at a fixed price for a set period, like a voucher to purchase stock later at today’s price. It matters to investors because exercising NSOs creates ordinary income for the holder and can increase share count, affecting a company’s earnings and ownership mix; think of it as a future sale that can dilute existing shareholders and has immediate tax consequences for the recipient.
Rule 10b5-1 trading plan regulatory
"This transaction was automatically executed pursuant to a Rule 10b5-1 trading plan"
A Rule 10b5-1 trading plan is a pre-arranged schedule that allows company insiders to buy or sell stock at specific times, even if they have inside information. It helps prevent accusations of unfair trading by making these transactions look planned and transparent, rather than sneaky or illegal.
weighted average price financial
"The price reported in Column 4 is a weighted average price"
Weighted average price is the average price of a security where each trade or component is counted according to its size, so bigger trades pull the average more than smaller ones. Think of it like calculating the average cost of a grocery haul where items you bought more of have greater influence on the final per-item cost. Investors use it to understand the true average price paid or received, judge execution quality, and compare trading performance against market movement.
vest in forty-eight equal monthly installments financial
"The shares underlying this option vest in forty-eight equal monthly installments"

FAQ

What insider transactions did SION's CEO report on August 20, 2025?
On August 20, 2025, CEO Michael Cloonan exercised options into 25,000 Sionna shares at $6.11 per share and sold 25,000 common shares at a reported $22.75 per share in open-market or private transactions, according to the Form 4.

How many SION shares does CEO Michael Cloonan own after this Form 4?
Following the reported option exercise and share sale, Michael Cloonan directly holds 547,343 Sionna common shares. This figure reflects his post-transaction ownership position as disclosed, providing investors a snapshot of his ongoing equity stake in the company.

At what prices did Michael Cloonan sell SION shares?
The Form 4 reports a sale of 25,000 Sionna shares at a price of $22.75 per share. Footnotes explain that this is a weighted average, with individual trades executed between $21.0700 and $23.99 per share during the sale transactions.

Was any SION insider trading done under a Rule 10b5-1 plan?
Footnote disclosure states that a transaction was automatically executed under a Rule 10b5-1 trading plan adopted on May 21, 2025. Such plans are pre-arranged and can reduce the informational significance of trade timing for investors.

What stock options did Michael Cloonan exercise for SION shares?
Michael Cloonan exercised Non-Qualified Stock Options to acquire 25,000 Sionna common shares at an exercise price of $6.11 per share. The underlying option is scheduled to expire on March 1, 2032, with vesting over forty-eight equal monthly installments.

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

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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)
08/20/2025
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 08/20/2025 M(1) 25,000 A $6.11 572,343 D
Common Stock 08/20/2025 S(1) 25,000 D $22.75(2) 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 08/20/2025 M(1) 25,000 (3) 03/01/2032 Common Stock 25,000 $0.0 228,142 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 $21.0700 to $23.99, 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 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 08/21/2025
** 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.

Source: View Original Filing on SEC EDGAR