A Study to Evaluate Safety and Pharmacokinetics of VX-659 in Healthy Subjects and in Adults With Cystic Fibrosis

Inclusion Criteria: Healthy Volunteers: PARTS A, B, and C * Males and Females of non-childbearing potential. * Between the ages of 18 and 60 years inclusive * Healthy, as defined per protocol. * Body mass index (BMI) of 18.0 to 32.0 kg/m2 inclusive * Body weight \>50 kg CF Patients: PART D * Body weight ≥35 kg. * Males and Females of non-childbearing potential. * Sweat chloride value ≥ 60 mmol/L at screening. * Heterozygous for F508del and a minimal function CFTR mutation * Forced expiratory volume in 1 second (FEV1) ≥40% and ≤90% of predicted at screening Exclusion Criteria: Healthy Volunteers: PARTS A, B, and C * History of any illness or any clinical condition that in the opinion of the investigator might confound the results of the study or pose additional risk to the subject. * Any condition possibly affecting drug absorption. * History of febrile illness within 14 days before the first study drug dose. * Glucose-6-phosphate dehydrogenase (G6PD) deficiency assessed at Screening. CF Patients: PART D * History of any comorbidity that, in the opinion of the investigator, might confound the results of the study or pose an additional risk to the subject. * History of cirrhosis with portal hypertension. * Risk factors for Torsade de Pointes. * G6PD deficiency assessed at Screening. * Abnormal Laboratory Values. * Lung infection with organisms associated with a more rapid decline in pulmonary status * History of solid organ or hematological transplantation.