SION-638

SION-638 is a novel, orally administered small molecule developed by Sionna Therapeutics for the treatment of cystic fibrosis (CF). It is the first clinical-stage modulator specifically designed to target and stabilize the first nucleotide-binding domain (NBD1) of the cystic fibrosis transmembrane conductance regulator (CFTR) protein. The F508del mutation in CFTR, which is present in most people with CF, causes NBD1 to become unstable and leads to rapid degradation of the protein before it reaches the cell surface. By binding with high affinity to both wild-type and F508del-mutated NBD1, SION-638 increases protein stability and promotes proper folding and trafficking of CFTR to the cell membrane. Preclinical studies have shown that SION-638 can restore chloride channel function—especially when used in combination with existing approved modulators such as elexacaftor, tezacaftor, and ivacaftor (components of Trikafta)—achieving or exceeding wild-type levels of activity. Phase 1 trials have demonstrated safety, tolerability, target engagement, and pharmacokinetics in healthy volunteers[4][5][6][7][9][10].