Roll-Over Study of Ivacaftor in Cystic Fibrosis Pediatric Subjects With a CF Transmembrane Conductance Regulator Gene (CFTR) Gating Mutation

Inclusion Criteria (Ivacaftor Arm):

1. Completed the last study visit of the treatment period of the previous study
(NCT01705145)

2. Hematology, serum chemistry, and vital signs results on Day 1 with no clinically
significant abnormalities that would interfere with the study assessments, as judged
by the investigator

3. As judged by the investigator, parent or legal guardian must be able to understand
protocol requirements, restrictions, and instructions and the parent or legal
guardian should be able to ensure that the subject assents to participation in the
study to the degree the subject can assent, and that the subject will comply with and
is likely to complete the study as planned

Inclusion Criteria (Observational Arm):

1. Subjects who completed their assigned study drug treatment in the previous study
(NCT01705145) and elected not to enroll in the ivacaftor arm and subjects who prematurely
discontinued treatment in the previous study and received at least 1 dose of study drug
treatment in the previous study will be eligible for enrollment in the observational arm.

Exclusion Criteria (Ivacaftor Arm):

1. Subjects who prematurely discontinued from the previous study

2. History of any illness or condition 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

3. Subjects with a history of study treatment intolerance as observed in their previous
study that, in the opinion of the investigator, might pose an additional risk in
administering study drug to the subject

4. Subjects receiving commercially-available ivacaftor treatment

5. Subject was unable to complete an adequate slit-lamp examination at the last
ophthalmologic examination in the previous study

Exclusion Criteria: (Observational Arm)

1. Subjects receiving ivacaftor treatment will not be eligible for enrollment in the
observational arm.