An NS3/4A protease inhibitor; has in vitro activity against major HCV genotypes (Kis = 0.1, 0.1, 0.08, 0.15, and 0.9 nM for genotypes 1a, 1b, 2a, 2b, and 3a, respectively); has in vitro activity against common HCV resistance genotypes (Kis = 0.07, 0.14, and 0.30 for genotypes 1b R155K, D165V, and D168Y, respectively); inhibits the NS3/4A protease in an in vitro replicon system (EC50s = 2 and 8 nM for genotypes 1a and 2a, respectively)