Rescue of CF airway epithelial cell function in vitro by a CFTR potentiator, VX-770

TLDR

Cystic fibrosis is a fatal genetic disease caused by mutations in the CFTR gene, which encodes a PKA‑activated epithelial anion channel essential for salt and fluid transport, and currently no approved therapies target CFTR. Here we describe the in vitro pharmacology of VX‑770, an orally bioavailable CFTR potentiator in clinical development for the treatment of CF. VX‑770 potentiates CFTR by increasing channel open probability. In vitro, VX‑770 increased CFTR open probability in F508del and G551D mutants, boosted chloride secretion in human CF bronchial epithelia to about 50 % of normal, reduced excessive sodium absorption, enhanced ciliary beating, and thereby demonstrated that restoring CFTR function rescues airway epithelial function.

Abstract

Cystic fibrosis (CF) is a fatal genetic disease caused by mutations in the gene encoding the CF transmembrane conductance regulator (CFTR), a protein kinase A (PKA)-activated epithelial anion channel involved in salt and fluid transport in multiple organs, including the lung. Most CF mutations either reduce the number of CFTR channels at the cell surface (e.g., synthesis or processing mutations) or impair channel function (e.g., gating or conductance mutations) or both. There are currently no approved therapies that target CFTR. Here we describe the in vitro pharmacology of VX-770, an orally bioavailable CFTR potentiator in clinical development for the treatment of CF. In recombinant cells VX-770 increased CFTR channel open probability (P(o)) in both the F508del processing mutation and the G551D gating mutation. VX-770 also increased Cl(-) secretion in cultured human CF bronchial epithelia (HBE) carrying the G551D gating mutation on one allele and the F508del processing mutation on the other allele by approximately 10-fold, to approximately 50% of that observed in HBE isolated from individuals without CF. Furthermore, VX-770 reduced excessive Na(+) and fluid absorption to prevent dehydration of the apical surface and increased cilia beating in these epithelial cultures. These results support the hypothesis that pharmacological agents that restore or increase CFTR function can rescue epithelial cell function in human CF airway.