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