(R)-Posenacaftor ((R)-PTI-801) sodium, the R enantiomer of Posenacaftor, is a cystic fibrosis transmembrane regulator (CFTR) protein modulator. It corrects the folding and trafficking of the CFTR protein, and is utilized in the research of cystic fibrosis (CF)[1].

Cystic fibrosis (CF) is an autosomal recessive disorder, caused by mutations of the cystic fibrosis transmembrane conductance regulator (CFTR)[1].CFTR is a cAMP-regulated chloride channel that is primarily located at the apical membrane of epithelial cells. Mutations in the CFTR gene lead to the production of a defective and misfolded CFTR protein, and impairs the flow of ions in and out of cells[1].Posenacaftor is a CFTR corrector, correctors are designed to fix and restore the function of the defective CFTR protein. The corrected CFTR then moves to the cell surface, where it functions as a chloride channel and helps maintain the right balance of fluid in the airways[2].