Absolute change in percent predicted in 1 second FEV1 from baseline through week 24

LCI2.5 represents the number of lung turnovers required to reduce the end tidal inert gas concentration to 1/40th of its starting value.

FEV1 is the volume of air that can forcibly be blown out in one second, after full inspiration.

AE: any untoward medical occurrence in a participant during the study; the event does not necessarily have a causal relationship with the treatment. This includes any newly occurring event or previous condition that has increased in severity or frequency after the informed consent form is signed. AE includes serious as well as Non-serious AEs. SAE (subset of AE): medical event or condition, which falls into any of the following categories, regardless of its relationship to the study drug: death, life threatening adverse experience, Inpatient hospitalization/prolongation of hospitalization, persistent/significant disability or incapacity, congenital anomaly/birth defect, important medical event. AEs with start date or increased severity on or after the first dose of study drug through the end of study participation was considered treatment-emergent.

AE: any untoward medical occurrence in a participants during the study; the event does not necessarily have a causal relationship with the treatment. This includes any newly occurring event or previous condition that has increased in severity or frequency after informed consent form is signed. AE includes serious as well as non-serious AEs. SAE (subset of AE): medical event or condition, which falls into any of the following categories, regardless of its relationship to the study drug: death, life threatening adverse experience, In-patient hospitalization/prolongation of hospitalization, persistent/significant disability or incapacity, congenital anomaly/birth defect, important medical event. TEAEs were defined as adverse events with start date or increased severity on and after the first dose of study drug through Week 108.

AE: any adverse change from participant's baseline (pre-treatment) condition, including any adverse experience, abnormal recording/clinical laboratory assessment which occurs during course of study, whether it is considered related to study drug or not. SAE: medical event or condition, which falls into any of following categories, regardless of its relationship to the study drug: death, life threatening adverse experience, in-patient hospitalization/prolonged hospitalization, persistent/significant disability/incapacity, congenital anomaly/birth defect, important medical event. Related AEs includes all AEs for which the causality was either related to study drug or possibly related to study drug. Data was reported as per the dose received and for overall participants.

AE: any adverse change from participant's baseline (pre-treatment) condition, including any adverse experience, abnormal recording/clinical laboratory assessment which occurs during course of study, whether it is considered related to study drug or not. AE includes both serious and non-serious AE. SAE: medical event or condition, which falls into any of following categories, regardless of its relationship to the study drug: death, life threatening adverse experience, in-patient hospitalization/prolonged hospitalization, persistent/significant disability/incapacity, congenital anomaly/birth defect, important medical event. Related AEs includes all AEs for which the causality was either related to study drug or possibly related to study drug. Data was reported as per the dose received.

Plasma concentration was reported for ivacaftor and its metabolites (hydroxymethyl ivacaftor \[M1\] and ivacaftor carboxylate \[M6\]) up to 24 hours post-dose on Day 4 (Hour 0 \[pre-dose\] on Day 1 and Day 4; 2, 3, 6, 24 hours post-dose on Day 4). Data was planned to be reported for overall participants in the period.

FEV1 is the volume of air that can forcibly be blown out in one second, after full inspiration. Hankinson and Wang standards were used to calculate percent predicted FEV1 (for age, gender, and height). The Hankinson standard was used for male subjects 18 years and older and female subjects 16 years and older. The Wang standard was used for male subjects aged 6 to 17 years and for female subjects aged 6 to 15 years.

FEV1 is the volume of air that can forcibly be blown out in one second, after full inspiration. Hankinson and Wang standards were used to calculate percent predicted FEV1 (for age, gender, and height). The Hankinson standard was used for male subjects 18 years and older and female subjects 16 years and older. The Wang standard was used for male subjects aged 6 to 17 years and for female subjects aged 6 to 15 years. Baseline was defined as the most recent non-missing measurement collected before initial administration of study drug during study Part 1.

FEV1 is the volume of air that can forcibly be blown out in one second, after full inspiration. Hankinson and Wang standards were used to calculate percent predicted FEV1 (for age, gender, and height). The Hankinson standard was used for male subjects 18 years and older and female subjects 16 years and older. The Wang standard was used for male subjects aged 6 to 17 years and for female subjects aged 6 to 15 years. Absolute change in percent predicted FEV1 over 24 weeks of ivacaftor treatment (from Week 12 \[Part 1: Treatment Period 2\] through Week 36 \[Part 2\]) was reported for subjects who received ivacaftor in Part 1: Treatment Period 2, as per planned analysis. Baseline was defined as the most recent non-missing measurement collected before initial administration of study drug during Part 1: Treatment Period 2.

Adverse Event: any untoward medical occurrence in a participant during the study, including any unfavorable and unintended sign, symptom, or disease whether or not it was considered to be study drug related. This included any newly occurring event or previous condition that increased in severity or frequency after obtaining informed consent and assent (where applicable). SAE: medical event or condition, which resulted in any of following, regardless of its relationship to the study drug: death, life threatening adverse experience, in-patient hospitalization/prolonged hospitalization, persistent/significant disability/incapacity, congenital anomaly/birth defect, important medical event. Non-Serious AEs included all AEs except SAEs.

Spirometry (as measured by FEV1) is a standardized assessment to evaluate lung function that is the most widely used endpoint in cystic fibrosis studies.

FEV1 is the volume of air that can forcibly be blown out in one second, after full inspiration. Hankinson and Wang standards were used to calculate percent predicted FEV1 (for age, gender, and height). The Hankinson standard was used for male participants 18 years and older and female participants 16 years and older. The Wang standard was used for male participants aged 12 to 17 years and for female participants aged 12 to 15 years. Data was to be reported for each cycle (Cycle 1 and Cycle 2) and as per drug treatment, for overall participants and as per genotype (residual function mutation and mRNA splice site mutation).

Lung clearance index (LCI) is a measure of ventilation inhomogeneity that is derived from a multiple-breath washout test. The LCI was calculated as the number of lung volume turnovers (cumulative expired volume divided by the functional residual capacity \[FRC\]) required to reduce end-tidal SF6 concentration to 1/40th of the starting value.

Adverse event data were collected up to the follow-up visit (5 to 9 days after last dose of study drug). Serious adverse events that were ongoing at the follow-up visit were followed until the event resolved, returned to baseline, or was determined to be a stable or chronic condition.

Adverse event data were collected up to the follow-up visit (5 to 9 days after last dose of study drug). Serious adverse events that were ongoing at the follow-up visit were followed until the event resolved, returned to baseline, or was determined to be a stable or chronic condition.

PK Parameters - maximum observed plasma concentrations (Cmax) and area under the concentration versus time curve (AUC),

PK parameters - maximum observed plasma concentrations (Cmax) and area under the concentration versus time curve (AUC),