Study 110 is a Phase 3, multicenter study in subjects aged 6 years and older with cystic fibrosis (CF) who are homozygous for the F508del-CF transmembrane conductance regulator (CFTR) mutation and who participated in Study 109 (NCT02514473) or Study 011B (NCT01897233). Study 110 is designed to evaluate the safety and efficacy of long term treatment of lumacaftor in combination with ivacaftor.