Study to Evaluate Safety and Efficacy of VX-661 in Combination With Ivacaftor in Subjects With Cystic Fibrosis, Homozygous for the F508del-CFTR Mutation With an Open-Label Expansion

Inclusion Criteria:

- Homozygous for the F508del CFTR mutation

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

- 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
participant

- Pregnant and nursing females: Females of childbearing potential must have a negative
pregnancy test at screening and Day 1 of the PC Phase and Day -7 or Day 1 of the OLE
Phase (whichever was applicable)

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

- The participant or a close relative of the participant is the investigator or sub
investigator, research assistant, pharmacist, study coordinator, or other staff
directly involved with the conduct of the study.