Sionna Therapeutics is a clinical-stage biopharmaceutical company focused entirely on cystic fibrosis (CF), a fatal genetic disease affecting roughly 106,000 patients globally. CF is caused by mutations in the CFTR gene, with the most common mutation — F508del, present in ~90% of patients — destabilizing a specific region of the CFTR protein called NBD1, which prevents the protein from folding and reaching the cell surface properly. Sionna's core thesis is that directly stabilizing NBD1 with small molecule drugs can restore CFTR function more completely than existing approved therapies, which do not target NBD1. Sionna has two lead clinical programs: SION-719, an NBD1 stabilizer in Phase 2a as an add-on to Vertex's Trikafta (the current standard of care), and SION-451, an NBD1 stabilizer in Phase 1 being evaluated in a dual combination with Sionna's own complementary modulators. Both programs posted positive Phase 1 data in June 2025, with topline Phase 2 data expected mid-2026. Sionna also holds licensed complementary modulators from AbbVie and Sanofi, designed to work synergistically with its NBD1 stabilizers. Sionna's two development pathways are: adding SION-719 to Trikafta for patients sub-optimally controlled on the current standard of care, and building a fully proprietary two-drug combination around SION-451 that would not rely on Vertex's products. Sionna has no approved products and no revenue, and plans to commercialize through a focused specialty sales force targeting CF treatment centers if products reach approval.