The purpose of this study is to assess the pharmacokinetics and safety of VX-809 and VX-770 alone and in combination in healthy subjects.

This is a Phase 1, randomized, double-blind, placebo-controlled, multiple-dose study of orally administered VX-809 and VX-770 in healthy subjects. This study will evaluate safety and tolerability of VX-809 and VX-770 alone and in combination.

Subjects will be randomized to receive study drug or placebo during three 14-day treatment periods separated by 14-day washout periods. In Treatment Period 1, subjects randomized to study drug will receive VX-809 every 24 hours. In Treatment Period 2, subjects randomized to study drug will receive VX-770 every 12 hours. In Treatment Period 3, subjects will receive VX-809 every 24 hours and VX-770 every 12 hours. Subjects randomized to placebo will receive placebo during all treatment periods.

Enrollment is planned at 1 clinical site (Lenexa, Kansas). Up to 72 subjects will be enrolled. The study will be separated into 3 dose escalation cohorts. Cohort 1 and Cohort 2 will enroll 24 subjects. Cohort 3 is optional and may be conducted after a review of safety and pharmacokinetic data by Vertex.

Inclusion Criteria:

• Male or female subject between 18 and 55 years of age, inclusive
• Body mass index (BMI) between 18.5 and 30.0 kg/m2, inclusive
• Subjects of child bearing potential and who are sexually active must meet the contraception requirements
• Female subject must have a negative serum pregnancy test at screening and Day -1

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 to the subject
• Participated in a clinical study involving administration of either an investigational or a marketed drug within 30 days or 5 terminal half-lives (whichever is longer) before the Screening visit
• Subject who has received VX-770 or VX-809 in a previous clinical study