A Study to Evaluate the Efficacy and Safety of VX-661 in Combination With Ivacaftor in Subjects Aged 12 Years and Older With Cystic Fibrosis, Heterozygous for the F508del-CFTR Mutation

Study to evaluate the efficacy of VX-661 in combination with ivacaftor (IVA, VX-770) through Week 12 in participants with cystic fibrosis (CF) who are heterozygous for the F508del mutation on the CF transmembrane conductance regulator (CFTR) gene and with a second CFTR mutation that is not likely to respond to VX-661 and/or IVA therapy (F508del/not responsive \[NR\]).