A Safety and Efficacy Study of the Combination of VX-222 and Telaprevir in Treatment-Naïve Subjects With Genotype 1 Chronic Hepatitis C Virus Infection

The purpose of this study is to assess the safety and efficacy of combination treatment with
VX-222 and telaprevir administered for 12 weeks with and without peginterferon-alfa-2a
and/or ribavirin. The subjects enrolled in this study are chronically infected with
hepatitis C virus (HCV) genotype 1 and will not have previously received treatment for their
HCV infection.

This study will include an Investigational Phase and Extension Phase. These phases will
contain a Treatment Period and a Follow-up Period. All subjects will be enrolled in the
Investigational Phase of this study. Subjects who fail treatment during the Investigational
Phase will have the option to enter the Extension Phase at which point they will be eligible
to receive peginterferon alfa-2a and ribavirin for a total of 48 weeks.

Based on an evaluation of on-treatment safety, pharmacokinetic and antiviral data from
patients in each arm of the trial, Vertex may elect to enroll up to two additional treatment
arms (Treatment Arm E and Treatment Arm F) that will evaluate telaprevir/VX-222-based
combination therapy. The components of the treatment regimens of these arms will be
selected based on clinical data that emerges from the four initially-studied regimens. If
enacted, up to 25 patients are expected to enroll in each additional treatment arm.

If Treatment Arm E or Treatment Arm F is discontinued subjects meeting certain criteria will
have the option to enter a telaprevir-containing Rollover Phase. Subjects who do not meet
the eligibility criteria to enter the Rollover Phase may elect to enter the Extension Phase.