Safety Study of Ivacaftor in Subjects With Cystic Fibrosis

• Number of Subjects With Adverse Events (Combined Part 1 and Part 2) [ Time Frame: Baseline to Follow-up ]
  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.
  
  
• Number of Adverse Events (Combined Part 1 and Part 2) [ Time Frame: Baseline to Follow-up ]
  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.
  
  

• Change From Baseline in Nasal Potential Difference (Combined Part 1 and Part 2) [ Time Frame: 14 days and 28 days ]
  The transepithelial nasal potential difference (NPD) is a direct measure of transepithelial ion transport. NPD under conditions of zero chloride concentration perfusion solution in the presence of isoproterenol was of primary interest.
  
  
• Change From Baseline in Percent Predicted Forced Expiratory Volume in 1 Second [FEV1] (Combined Part 1 and Part 2) [ Time Frame: 14 days and 28 days ]

  Spirometry is a standardized assessment to evaluate lung function that is the most widely used endpoint in cystic fibrosis studies.

  Relative change reflects the percent change from the baseline values [100% * (X-Y)/Y], where X and Y are post-baseline and baseline values, respectively.

  
  
• Change From Baseline in the Cystic Fibrosis Questionnaire-Revised (CFQ-R) Score (Part 2 Only)(Respiratory Domain Score) [ Time Frame: 14 days and 28 days ]
  The CFQ-R is a health-related quality of life measure for subjects with cystic fibrosis. Each domain is scored from 0 (worst) to 100 (best). A difference of at least 4 points in the respiratory domain score of the CFQ-R is considered a minimal clinically important difference (MCID).
  
  
• Change From Baseline in Maximum Sweat Chloride Concentration (Combined Part 1 and Part 2) [ Time Frame: 14 days and 28 days ]
  The sweat chloride (quantitative pilocarpine iontophoresis) test is a standard diagnostic tool for cystic fibrosis (CF), serving as an indicator of cystic fibrosis transmembrane conductance regulator (CFTR) activity.
  
  

This was a double-blind, placebo-controlled, cross-over, multiple dose study of up to 28 days of dosing, in subjects with cystic fibrosis (CF) who have a G551D-CTFR gene mutation. Enrollment of 39 subjects occurred at 15 centers in the US, Canada, and Germany.

The study was conducted in 2 parts:

• Part 1 consisted of Group A and Group B. Subjects in Group A (10 subjects) were randomized to receive 25 mg of ivacaftor every 12 hours [q12h] (4 subjects), 75 mg of ivacaftor q12h (4 subjects), or placebo (2 subjects) for 14 days. Following a 7- to 28-day washout period, subjects who received active study drug crossed over to the alternate dose strength of ivacaftor for an additional 14 days. Placebo subjects continued to receive placebo for an additional 14 days. Subjects in Group B (10 subjects) were randomized to receive 75 mg of ivacaftor q12h (4 subjects), 150 mg of ivacaftor q12h (4 subjects), or placebo (2 subjects) for 14 days. Following a 7- to 28-day washout period, the subjects who received active study drug crossed over to the alternate dose strength of ivacaftor for an additional 14 days. Placebo subjects continued to receive placebo for an additional 14 days.
• Part 2 consisted of Group C; these subjects did not participate in Part 1. Subjects were randomized to receive 150 mg of ivacaftor q12h (7 subjects), 250 mg of ivacaftor q12h (7 subjects), or placebo (4 subjects) for a total of 28 days. Ivacaftor doses studied in Part 2 were selected following an interim pharmacokinetic/pharmacodynamic (PK/PD) and statistical analyses of data from Part 1. The 2 doses selected for Part 2 were anticipated to enable better definition of the optimal therapeutic dose.