A Phase 3 Study of Tezacaftor (VX-661) in Combination With Ivacaftor (VX-770) in Subjects Aged 12 Years and Older With Cystic Fibrosis (CF), Who Have One F508del-CFTR Mutation and a Second Mutation That Has Been Demonstrated to be Clinically Responsive to Ivacaftor

Inclusion Criteria:

- Heterozygous for F508del-CFTR mutation and a second CFTR allele with a gating defect
that is clinically demonstrated to be ivacaftor responsive

- FEV1 ≥40% and ≤90% of predicted normal for age, sex, and height during screening

- Stable CF disease as judged by the investigator.

Exclusion Criteria:

- History of any comorbidity that, in the opinion of the investigator, might confound
the results of the study or pose an additional risk in administering study drug to the
subject.

- Pregnant and nursing females (females of childbearing potential must have a negative
pregnancy test at Screening and Week -4 Visits).

- Sexually active subjects of reproductive potential who are not willing to follow the
contraception requirements