Study of Lumacaftor in Combination With Ivacaftor in Subjects 6 Through 11 Years of Age With Cystic Fibrosis, Homozygous for the F508del-CFTR Mutation

Inclusion Criteria:

- Confirmed diagnosis of CF defined as:

- with 2 CF-causing mutations

- chronic sinopulmonary disease or gastrointestinal/nutritional abnormalities

- Subjects who weigh > 15 kg without shoes at Screening Visit

- Subjects who are homozygous for the F508del-CFTR mutation

- Subjects with percent predicted Forced Expiratory Volume in 1 second (FEV1) of 70% to
105% (inclusive) (Part A) or ≥40% (Part B) at the screening visit where the predicted
values are adjusted for age, sex, and height using the Wang equation

- Subjects with stable CF disease and who are willing to remain on stable CF medication
regimen

- Able to swallow tablets

Exclusion Criteria:

- History of any illness or condition that might confound the results of the study or
pose an additional risk in administering study drug to the subject

- Acute respiratory infection, pulmonary exacerbation, or changes in therapy for
pulmonary disease within 28 days before Day 1 of the study

- Abnormal liver function as defined in the protocol at Screening

- Abnormal renal function as defined in the protocol at Screening

- History of solid organ or hematological transplantation

- Ongoing participation in another therapeutic clinical study or prior participation in
an investigational drug study within 30 days prior to Screening

- Evidence of lens opacity or cataract at the Screening

- Colonization with organisms associated with a more rapid decline in pulmonary status
at Screening (Part A only)

- A standard 12-lead ECG demonstrating QtcF >450 msec at Screening