Atlas Venture Opportunity Fund II, L.P. Plans to Sell Sionna Therapeutics Common Stock

Atlas Venture Opportunity Fund II, L.P. has filed a Form 144 with the SEC indicating its intention to sell 9,712 shares of Sionna Therapeutics, Inc. common stock. The shares were acquired through a private placement on March 4, 2024. The notice, signed by Ommer Chohan, was filed on October 20, 2025, with a plan adoption date of February 25, 2025. The filing also details recent sales of Sionna Therapeutics common stock by Atlas Venture Opportunity Fund II, L.P. and Atlas Venture Fund XI, LP over the past three months, totaling significant amounts. The aggregate market value of the shares to be sold is approximately $310,104.16. The shares are listed on NASDAQ, and Merrill Lynch is the broker involved in the transactions.