The FEV1 is the volume of air forcibly exhaled in one second and is measured using forced expiratory air spirometry. Change in ppFEV1 at Week 48 was defined as the average between the change from baseline at Week 40 and that at Week 48. Baseline for ppFEV1 was defined as an average of ppFEV1 at Screening (Weeks -4 to -1) and Baseline (Day 1) visits.

A TEAE was any untoward medical occurrence in a participant who received study drug without regard to possibility of causal relationship that occurred or worsened in the period extending from the first dose of study drug to 6 weeks after the last dose of study drug. A serious adverse event (SAE) was an adverse event (AE) resulting in any of the following outcomes or deemed significant for any other reason: death; initial or prolonged inpatient hospitalization; life-threatening experience (immediate risk of dying); persistent or significant disability/incapacity; congenital anomaly. AEs included both SAEs and non-serious AEs. AE severity was graded as follows: Grade 1: mild; Grade 2: moderate; Grade 3: severe; Grade 4: life-threatening; Grade 5: fatal. A TEAE was considered related if in the opinion of the Investigator it was possibly or probably caused by the study drug. A summary of other non-serious AEs and all SAEs, regardless of causality is located in the Adverse Events module.

A TELA is any abnormal laboratory value that started or worsened after administration of study drug. Abnormal values were defined as values outside normal range. Values considered abnormal included -Hepatic: Serum total bilirubin ≥1.5\*upper limit of normal (ULN); serum gamma glutamyl transferase \>2.5\*ULN; serum alanine aminotransferase increase of \>150 units/liter (U/L) without increased creatine kinase; -Adrenal: plasma adrenocorticotropic hormone \>ULN (normal cortisol); -Renal: serum cystatin C \>1.33 milligrams (mg)/L; serum creatinine \>ULN-1.5\*ULN for age; serum blood urea nitrogen ≥1.5\*ULN; urine protein:creatinine \>0.40 mg/deciliter (dL):mg/dL; urine protein:osmolality \>0.30 mg/L:milliosmoles/kilogram; urine blood 2+; - Serum Electrolytes: serum sodium \>150 millimoles (mmol)/L, \<130 mmol/L; serum potassium \>5.5, \<3.0 mmol/L; serum magnesium \>1.23 mmol/L, \<0.5 mmol/L; total serum calcium \>2.9 mmol/L, \<2.0 mmol/L; serum phosphorous \<0.8 mmol/L; serum biocarbonate- \<16 mmol/L.

Spirometry was used to assess pulmonary function by measuring the percentage of predicted function, which was determined on the basis of the height value obtained at the same study visit, for FEV1 (the amount of air that can be exhaled in 1 second). Spirometry was assessed by using current guidelines of the American Thoracic Society (ATS) and European Respiratory Society (ERS). Baseline was the average of percent-predicted FEV1 at screening and randomization.

Spirometry was used to assess pulmonary function by measuring the percentage of predicted function, which was determined on the basis of the height value obtained at the same study visit, for FEV1 (the amount of air that can be exhaled in 1 second). Spirometry was assessed by using current guidelines of the American Thoracic Society (ATS) and European Respiratory Society (ERS). The percentage of change in percent-predicted of FEV1 was calculated as follows: (\[percent-predicted FEV1-Baseline percent-predicted FEV1\]/Baseline percent-predicted FEV1)\*100. Baseline was the average of percent-predicted FEV1 at screening and randomization. A negative change from Baseline indicates that percent-predicted of FEV1 decreased.

Nasal transepithelial potential difference (TEPD) was assessed in each participant using standardized techniques. Warmed solutions of Ringer's solution, amiloride, chloride-free gluconate, isoproterenol, and adenosine triphosphate (ATP) were perfused for ≥3-minute sequentially through a nasal catheter while a voltage tracing was recorded. Total chloride transport was computed for each nostril. The total chloride transport values were calculated by subtracting the voltages at the end of a perfusion from the voltage at the end of an earlier perfusion (isoproterenol - amiloride). The average of the values for each nostril was computed. If the assessment was available in only 1 nostril, this value was used as if it were the average of both nostrils. Baseline data for Cycle 1 and Cycle 2 and change from Baseline data at Day 14 of Cycles 1 and 2 are presented.

Nasal TEPD was assessed in each participant using standardized techniques. Warmed solutions of Ringer's solution, amiloride, chloride-free gluconate, isoproterenol, and ATP were perfused for ≥3-minute sequentially through a nasal catheter while a voltage tracing was recorded. Total chloride transport was computed for each nostril. The total chloride transport values were calculated by subtracting the voltages at the end of a perfusion from the voltage at the end of an earlier perfusion (isoproterenol - amiloride). The average of the values for each nostril was computed. If the assessment was available in only 1 nostril, this value was used as if it were the average of both nostrils. Response to study treatment defined as an increase in total chloride transport as indicated by a change of at least -5 mV in nasal TEPD.

Nasal TEPD was assessed in each participant using standardized techniques. Warmed solutions of Ringer's solution, amiloride, chloride-free gluconate, isoproterenol, and ATP were perfused for ≥3-minute sequentially through a nasal catheter while a voltage tracing was recorded. Total chloride transport was computed for each nostril. The total chloride transport values were calculated by subtracting the voltages at the end of a perfusion from the voltage at the end of an earlier perfusion (isoproterenol - amiloride). The average of the values for each nostril was computed. If the assessment was available in only 1 nostril, this value was used as if it were the average of both nostrils. Normalization of chloride transport (normal range \[NR\]) was defined as nasal TEPD that was at least as electrically negative as -5 mV. Normalization in chloride transport can also be referred to as hyperpolarization.