Atlas Venture Fund XI, LP's Sale of Sionna Therapeutics, Inc. Common Stock

Atlas Venture Fund XI, LP has filed a Form 144 with the SEC, indicating its intention to sell 50,520 shares of Sionna Therapeutics, Inc. common stock. The shares were acquired through a private placement on March 4, 2024. The filing also details recent sales of Sionna Therapeutics, Inc. common stock by Atlas Venture Fund XI, LP and Atlas Venture Opportunity Fund II, L.P. over the past three months, totaling significant amounts. The sales were executed through Merrill Lynch, with the most recent sale occurring on October 16, 2025. The aggregate market value of the shares to be sold is approximately $1,653,014.40. This filing is important for investors tracking insider transactions and the liquidity of Sionna Therapeutics, Inc. stock.