This study investigated the effects of ivacaftor in participants with cystic fibrosis (CF) \>=12 years of age with a forced expiratory volume in 1 second (FEV1) \>=40 percent (%) predicted. This study was conducted in 2 parts.
* Part A of this study was a randomized, double-blind, placebo-controlled, parallel-group evaluation of participants with CF who were aged 12 years or older and were homozygous for the F508del-CFTR mutation.
* Part B of this study was an open-label extension of Part A, enrolling participants who completed Part A and met pre-specified endpoint criteria, and explored the safety and efficacy of ivacaftor over long-term treatment in participants with CF aged 12 years or older who were homozygous for the F508del-CFTR mutation.
