Sionna Therapeutics SEC Filings

Sionna Therapeutics, Inc. (SION) Form 144 notice reports a proposed sale of 10,239 common shares through Merrill Lynch on NASDAQ with an aggregate market value of $302,255.28 and an approximate sale date of 09/30/2025. The shares were acquired in a private placement from the issuer on 03/04/2024 for cash. The filing also discloses related secondary sales on 09/29/2025: Atlas Venture Fund XI, LP sold 54,637 shares for $1,644,065.58 and Atlas Venture Opportunity Fund II, L.P. sold 11,468 shares for $345,080.15. The filer certifies no undisclosed material adverse information.

Sionna Therapeutics notice reports a proposed sale under Rule 144 of 2,149 common shares through Merrill Lynch (San Francisco) with an approximate aggregate market value of $63,438.48 and an intended sale date of 09/30/2025 on NASDAQ. The filing shows the shares were acquired on 03/04/2024 in a private placement from the issuer, paid in cash. The filing also discloses related sales in the prior three months: 11,468 shares (gross proceeds $345,080.15) by Atlas Venture Opportunity Fund II, L.P. and 54,637 shares (gross proceeds $1,644,065.58) by Atlas Venture Fund XI, LP on 09/29/2025.

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.

Sionna Therapeutics filed a Form 144 reporting a proposed sale of common stock. The notice shows 54,637 shares to be sold through Merrill Lynch on NASDAQ, with an aggregate market value of $1,581,194.78 and approximately 44,139,823 shares outstanding. The shares were acquired in a private placement from the issuer on 03/04/2024 and paid in cash on that date. The filing states there were no securities sold by the reporting person in the past three months. The notice includes the standard representation that the seller is not aware of any undisclosed material adverse information.

Sionna Therapeutics (SION) submitted a Form 144 notice indicating a proposed sale of 11,468 common shares through Merrill Lynch in San Francisco. The filing lists an aggregate market value of $331,883.92 and shows 44,139,823 shares outstanding for the issuer. The shares were originally acquired by private placement from the issuer on 03/04/2024 and were paid in cash on that date. The filing states the approximate sale date as 09/29/2025 and names NASDAQ as the exchange. No securities were reported sold in the past three months.

Sionna Therapeutics (SION) insider sale notice: This Form 144 reports a proposed sale of 25,000 common shares by an insider through Morgan Stanley Smith Barney, valued at $687,500, with the sale target date of 09/26/2025 on NASDAQ. The securities were acquired on 09/26/2025 by exercise of stock options and paid in cash. The filing shows 44,139,823 shares outstanding, so the proposed sale equals approximately 0.0566% of outstanding shares. The filer also disclosed three 10b5-1 sales by Michael Cloonan in August 2025 totaling 50,000 shares for aggregate gross proceeds of $1,193,154.98. The notice includes the standard insider representation about absence of undisclosed material information and a 10b5-1 plan reference but does not provide plan adoption dates or signature details.

Jennifer Fitzpatrick, Chief Legal Officer of Sionna Therapeutics, reported transactions on 09/04/2025 under a Rule 10b5-1 plan. She exercised a non-qualified stock option to purchase 10,250 shares at an exercise price of $6.11 per share and immediately sold 10,250 common shares at a weighted-average price of $23.12, with individual sale prices ranging from $21.80 to $24.52. Following these transactions, she reports 0 shares beneficially owned. The option vests 25% on June 3, 2025, with the remainder vesting monthly over 36 months.

Sionna Therapeutics, Inc. (SION) filing a Form 144 notifies a proposed sale of 10,250 common shares via Morgan Stanley Smith Barney on NASDAQ with an aggregate market value of $251,637.50. The shares were acquired and paid for on 09/04/2025 through exercise of stock options from the issuer. The filing lists 44,139,823 shares outstanding and reports no other sales by the seller in the past three months. The filer certifies no undisclosed material adverse information.

Elena Ridloff, CFO & Head of Corporate Development of Sionna Therapeutics (SION), reported planned sales under a Rule 10b5-1 trading plan adopted May 20, 2025. The Form 4 shows sales executed on 08/29/2025 (748 shares) and 09/02/2025 (8,836 shares) at weighted-average prices of $25.18 and $25.08 respectively, for a total of 9,584 shares sold. After the 08/29 sale Ridloff held 47,368 shares; after the 09/02 sale she held 38,532 shares. The filings state the trades were automatic under the 10b5-1 plan and note the sales occurred in multiple transactions at prices within the disclosed ranges. The reporting person authorized Jennifer Fitzpatrick as attorney-in-fact to sign the Form.