Study of Ivacaftor in Cystic Fibrosis Subjects Aged 12 Years and Older With the G551D Mutation

This was a phase 3 study in subjects with cystic fibrosis (CF) age 12 years and older who have a G551D-CFTR mutation and percent predicted forced expiratory volumn in 1 second (FEV1) between 40% and 90%. Based on in vitro studies and pharmacologic, pharmacokinetic (PK), and safety profiles, ivacaftor was selected for clinical development as a possible treatment for patients with CF. Patients with the G551D mutation were the targeted population for this study because ivacaftor is a potentiator of the gating function of the CFTR protein, and the most prevalent mutation with a gating defect in CF is the G551D mutation. This study was designed to further evaluate the efficacy of ivacaftor in subjects with CF who have a G551D-CFTR gene mutation and to evaluate safety in this population over a longer period than previously studied.