A Randomized, Placebo- and Active-Controlled, Double-Blind, 4-way Crossover Design, Thorough ECG Study of VX-770 in Healthy Adult Subjects

The drug VX-770 to be given is a new, investigational compound that may
eventually be used for the treatment of cystic fibrosis.

Cystic Fibrosis is a genetic disorder known to be an inherited disease of the
secretory glands, including the glands that produce mucus and sweat. The gene
known as CFTR is responsible for aiding in the regulation of salt and water
absorption and secretion in various tissues. This function is defective in
people with Cystic Fibrosis and supports the theory that by restoring or
improving CFTR function that the symptoms of Cystic Fibrosis would be reduced.
VX-770 may be effective in the restoration of CFTR and it is therefore possible
that it could reduce the symptoms experienced by sufferers of Cystic Fibrosis.

Part A:
To evaluate the safety and tolerability of increasing doses of VX-770 up to 450
mg (q12h) in healthy male subjects.

Part B:
To determine if therapeutic or supratherapeutic systemic exposure to multiple
doses of VX 770 prolongs the mean Fridericia-corrected QT (QTcF) interval by
more than 5 msec (based on an upper bound of 1 sided 95% confidence interval of
10 msec) in healthy male and female subjects, as compared with placebo dosing
and baseline.

Part A will be a double-blind, randomized, placebo-controlled, single-center
dose-escalation study investigating oral VX 770 in increasing doses up to 450
mg q12h in healthy male subjects. The safety and tolerability of this dose
will be used to confirm the supratherapeutic dose of VX 770 to be used in Part
B.

Part B will be a double-blind, randomized, placebo-, and active-controlled,
single-center, 4 period crossover study of the effect of VX 770 on QT/QTc
intervals in healthy male and female subjects.

Part A
An oral dose of 250 mg VX-770 or placebo twice daily on Day 1, an oral dose of
300 mg VX-770 or placebo twice daily on Day 2, an oral dose of 350 mg VX-770 or
placebo twice daily on Day 3, an oral dose of 400 mg VX-770 or placebo twice
daily on Day 4 and an oral dose of 450 mg VX-770 or placebo twice daily on Days
5-9

Part B
Therapeutic dose: an oral dose of 150 mg VX-770 twice daily on Days 1-4 and an
oral dose of 150 mg VX-770 on Day 5
Supratherapeutic dose: an oral dose of 450 mg VX-770 twice daily on Days 1-4
and an oral dose of 450 mg VX-770 on Day 5
Placebo control: an oral dose of placebo twice daily on Days 1-4 and an oral
dose of placebo on Day 5
Positive control: an oral dose of placebo twice daily on Days 1-4 and an oral
dose of 400 mg moxifloxacin on Day 5

Procedures:
Pain, light bleeding, heamatoma and possibly an infection.