Lung clearance index (LCI) is a measure of ventilation inhomogeneity that is derived from a multiple breath washout test using Nitrogen (N2). LCI2.5 represents the number of lung turnovers required to reduce the end tidal inert gas concentration to 1/40th of its starting value.

Full Analysis Set (FAS) included all randomized participants who received any amount of study drug. Here, number of participants analyzed signifies participants who were evaluable for this outcome measure.

Sweat samples were collected using an approved collection device. Baseline was defined as the average of the measurements at screening and on Day 1 pre-dose. Change from Baseline in sweat chloride at Day 15 and Week 4 was calculated. The average of the 2 values (Change at Day 15 and Week 4) was reported.

FAS. Here, number of participants analyzed signifies participants who were evaluable for this outcome measure.

BMI was defined as weight in kg divided by height in square meter (m^2).

FAS. Here, number of participants analyzed signifies participants who were evaluable for this outcome measure.

The CFQ-R is a validated participant-reported outcome measuring health-related quality of life for participants with cystic fibrosis. Respiratory domain assessed respiratory symptoms (for example, coughing, congestion, wheezing), score range: 0-100; higher scores indicating fewer symptoms and better health-related quality of life.

FAS. Here, number of participants analyzed signifies participants who were evaluable for this outcome measure.

LCI is a measure of ventilation inhomogeneity that is derived from a multiple breath washout test using Nitrogen (N2). LCI5.0 represents the number of lung turnovers required to reduce the end tidal inert gas concentration to 1/20th of its starting value.

FAS. Here, number of participants analyzed signifies participants who were evaluable for this outcome measure.

Sweat samples were collected using an approved collection device.

FAS. Here, number of participants analyzed signifies participants who were evaluable for this outcome measure.

FEV1 is the volume of air that can forcibly be blown out in one second, after full inspiration. Wang standards were used to calculate ppFEV1 (for age, gender, race, and height).

FAS. Here, number of participants analyzed signifies participants who were evaluable for this outcome measure.

FEV1 is the volume of air that can forcibly be blown out in one second, after full inspiration. Wang standards were used to calculate ppFEV1 (for age, gender, race, and height).

FAS. Here, number of participants analyzed signifies participants who were evaluable for this outcome measure.

BMI was defined as weight in kg divided by height in m^2. z-score is a statistical measure to evaluate how a single data point compares to a standard. It describes whether a mean was above or below the standard. BMI, adjusted for age and sex, was analyzed as BMI-for-age z-score (BMI z-score). The BMI-for-age z-scores were calculated using National Center for Health Statistics growth charts.

FAS. Here, number of participants analyzed signifies participants who were evaluable for this outcome measure.

FAS. Here, number of participants analyzed signifies participants who were evaluable for this outcome measure.

Z-score is a statistical measure to evaluate how a single data point compares to a standard. It describes whether a mean was above or below the standard. Weight, adjusted for age and sex, was analyzed as weight-for-age z-score (weight z-score). The weight-for-age z-scores were calculated using National Center for Health Statistics growth charts.

FAS. Here, number of participants analyzed signifies participants who were evaluable for this outcome measure.

FAS. Here, number of participants analyzed signifies participants who were evaluable for this outcome measure.

Z-score is a statistical measure to evaluate how a single data point compares to a standard. It describes whether a mean was above or below the standard. Height, adjusted for age and sex, was analyzed as height-for-age z-score (height z-score). The height-for-age z-scores were calculated using National Center for Health Statistics growth charts.

FAS. Here, number of participants analyzed signifies participants who were evaluable for this outcome measure.

The TSQM is a 14-item self-administered questionnaire which measures participants' experiences with their medication on four dimensions: effectiveness, side effects, convenience and global satisfaction. For each dimension, responses are added and transformed to a scale from 0 to 100, where higher scores indicate greater satisfaction.

FAS. Here, 'Number of participants analyzed' = those participants who were evaluable for this endpoint and 'Number Analyzed' = those participants who were evaluable at the specified time points for each arm, respectively.

Pulmonary exacerbation was defined as the treatment with new or changed antibiotic therapy (intravenous, inhaled, or oral) for greater than or equal to 4 sinopulmonary signs/symptoms. The number of events were reported.

FAS.

Pulmonary exacerbation was defined as the treatment with new or changed antibiotic therapy (intravenous, inhaled, or oral) for greater than or equal to 4 sinopulmonary signs/symptoms.

FAS.

Time-to-first pulmonary exacerbation was analyzed using the Kaplan-Meier estimates. Pulmonary exacerbation was defined as the treatment with new or changed antibiotic therapy (intravenous, inhaled, or oral) for greater than or equal to 4 sinopulmonary signs/symptoms.

FAS.

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. Any AE that increased in severity or newly developed at or after initial dosing of study drug to Week 28 was considered treatment-emergent.

Safety Set included all participants who were exposed to any amount of study drug.

Ctrough,ave is average of individual pre-dose observed concentrations across Week 4 and 24. C3-6h,ave is average of individual 3 to 6 hours post-dose observed concentrations across Day 1, 15 and Week 4. This outcome was not planned to be assessed in Placebo arm.

Pharmacokinetic (PK) set included all randomized participants who received any amount of study drug and had a PK assessment. Here, 'Number of participants analyzed' = those participants who were evaluable for this endpoint and 'Number Analyzed' = those participants who were evaluable at the specified time points for each arm, respectively.