February 7, 2006

Vertex Pharmaceuticals has completed dosing with VX-950 in a Phase II, 28-day clinical study in hepatitis C virus (HCV) infected patients. In addition, the company announced that it has completed three-month animal toxicology studies that will support clinical studies of VX-950 of up to three months duration. Initiation of additional Phase II clinical studies in the U.S. in patients with HCV is planned following required FDA review of these latest non- clinical and clinical results.

The 28-day Phase II study enrolled 12 treatment-naive patients with genotype 1 HCV. Patients received VX-950 in a tablet formulation at a dose of 750 mg every eight hours for 28 days in combination with standard doses of pegylated interferon alfa-2a (IFN) and ribavirin (RBV). At the end of 28 days, patients completed dosing with VX-950 and per study protocol were required to continue treatment with peg-IFN and RBV. The study was not designed to evaluate sustained viral responses in patients receiving VX-950.