A Phase 2 Study to Evaluate Effects of VX-661/Ivacaftor on Lung and Extrapulmonary Systems in Subjects With Cystic Fibrosis, Homozygous for the F508del-CFTR Mutation

Inclusion Criteria:

- Male and female participants, homozygous for the F508del CFTR mutation

- Confirmed diagnosis of CF by sweat chloride testing

- Forced Expiratory Volume in 1 Second (FEV1) ≥40% and ≤90% of predicted normal for age,
sex, and height at Screening Visit

- 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.

- An acute upper or lower respiratory infection, pulmonary exacerbation, or changes in
therapy for pulmonary disease within 28 days before Day 1

- History or evidence of clinically significant findings on ophthalmologic examination
during the Screening Period.

- History of solid organ or hematological transplantation

- Pregnant or nursing females

- Participants who have had radiation exposure within 1 year before the first
mucociliary clearance (MCC) procedure that would cause them to exceed federal
regulations by participating in this study

- In the opinion of the investigator, unable to adequately perform inhalation maneuvers
during the MCC procedures