The purpose of this study is to examine the drug-drug interaction effects of ciprofloxacin, itraconazole, and rifampin on the pharmacokinetics of lumacaftor in combination with ivacaftor as well as to evaluate the potential effects of lumacaftor in combination with ivacaftor on lung function.

Inclusion Criteria:

• Male and female subjects must be between the ages of 18 and 55 years, inclusive
• Body mass index (BMI) of 18 to 31 kg/m2, inclusive, and a total body weight >50 kg.

Exclusion Criteria:

• History of any illness that, in the opinion of the investigator, might confound the results of the study or pose an additional risk in administering study drug(s) to the subject. This may include, but is not limited to, a history of relevant drug or food allergies; history of cardiovascular or central nervous system disease; history or presence of clinically significant pathology; or history of mental disease.
• History of febrile illness within 5 days before the first dose.
• History of Gilbert's syndrome
• Abnormal renal function as defined at screening
• Blood donation of approximately 1 pint (500 mL) within 56 days before study drug administration
• Treatment with an investigational drug within 30 days or 5 half-lives (or as determined by the local requirements, whichever is longer) preceding the first dose of study drug
• Known hypersensitivity or prior adverse reaction to ciprofloxacin, or any member of the quinolone class of antimicrobial agents (Cohort 1 only); itraconazole, or to any of the other azoles (Cohort 2 only); rifampin, or to any of the rifamycins (Cohort 3 only)