Ivacaftor: the first therapy acting on the primary cause of cystic fibrosis.
Cystic fibrosis (CF) is a life-shortening disorder that affects over 30,000 people in the U.S. and 70,000 worldwide. CF is caused by mutations in the CFTR gene, which codes for the cystic fibrosis transmembrane conductance regulator (CFTR) protein. CFTR is a chloride and bicarbonate channel and regulates several ion transporters at the epithelial cell membrane, controlling hydration or ionic composition of epithelial secretions. Management of CF is currently supportive, but recent advances in drug development have focused on therapies that assist mutant CFTR function. In the current review, we summarize the development and clinical experience with VX-770 (ivacaftor), a small molecule that increases CFTR chloride conductance in vitro and in vivo, including wild-type and G551D CFTR. The G551D CFTR mutation is the third most common CF disease-causing mutation, in which the CFTR protein localizes to the epithelial cell membrane but has defective gating. With restoration of adequate CFTR function through pharmacotherapy, it is possible that the clinical course of patients with CF could be markedly improved, including longevity, quality of life and treatment burden.