A Phase 1, Randomized, 3-way Crossover, Open-label Study to Assess the Drug-drug Interaction Between VX-787 and Tamiflu®, Followed by a Double-blind, Randomized, Placebo-controlled Study to Collect Safety, Tolerability and Pharmacokinetics of VX-787, in Healthy Subjects

This study consists of 2 parts. Part 1 is an open-label (a medical research study in which participants and researchers are told which treatments the participants are receiving), randomized (treatment group assigned by chance), 3-way crossover (a method used to switch participants from one treatment group to another in a clinical trial) study to estimate drug-drug interaction between VX-787 and oseltamivir. It consists of 3 phases: a Screening phase, a Treatment phase and a Follow-up phase. Treatment phase will include 3 treatment sessions, each of the participant will receive Treatment A (VX-787, 600 milligram \[mg\] 2 times a day on Day 1 to 4, followed by a single dose of VX 787, 600 mg on Day 5); Treatment B (Oseltamivir, 75 mg 2 times a day on Day 1 to 4, followed by a single dose of oseltamivir 75 mg on Day 5) and Treatment C (VX-787, 600 mg 2 times a day + oseltamivir, 75 mg 2 times a day on Day 1 to 4, followed by a single dose of VX-787, 600 mg + a single dose of oseltamivir, 75 mg on Day 5). Each treatment session will be separated by a wash-out period of 5 days. The order each participant will receive treatments A, B and C will be decided at randomization. Part 2 is double-blind (a medical research study in which neither the researchers nor the participants know what treatment the subjects is receiving), randomized, placebo-controlled. It consists of 3 phases: a Screening phase, a Treatment phase and a Follow-up phase. In Treatment phase participants will be randomly assigned VX-787, 600 mg or placebo 2 times a day, on Day 1 to 9, followed by a single dose of VX-787 600 mg or placebo in the morning on Day 10. Pharmacokinetic parameters will be assessed primarily. Participants' safety will be monitored throughout the study.