5,5-fused arylene or heteroarylene hepatitis c virus inhibitors

Disclosed is samatasvir (also known as methyl (S)-2-((S)-2-(5-(4-(3-(2-(1-[(2S)-2-(methoxycarbonylamino)-3-methylbutanoyl]-pyrrolidin-2-yl)-1H-benzo[d]imidazol-5-yl)thieno[3,2-b]thiophen-6-yl)phenyl)-1H-imidazol-2-yl)pyrrolidin-1-yl)-2-oxo-1-(1R)-phenylethylcarbamate / [(S)-1-((S)-2-{ 6-[6-(4-{ (S)-2-[1-((R)-2-methoxycarbonylamino-2-phenylacetyl)-pyrrolidin-2-yl]-3H-imidazol-4-yl)-phenyl)-thieno[3,2-b]thiophen-3-yl]-1H-benzoimidazol-2-yl} -pyrrolidine-1-carbonyl)-2-methyl-propyl] -carbamic acid methyl ester / Methyl N-((1R)-2-((2S)-2-(5-(4-(6-(2-((2S)-1-((2S)-2-((methoxycarbonyl)amino)-3-methylbutanoyl)pyrrolidin-2-yl)-3H-benzimidazol-5-yl)thieno(3,2-b)thiophen-3-yl)phenyl)-1H-imidazol-2-yl)pyrrolidin-1-yl)-2-oxo-1-phenylethyl)carbamate) or a pharmaceutically acceptable salt thereof. Further disclosed is a pharmaceutical composition which comprises samatasvir, or a pharmaceutically acceptable salt thereof, one or more pharmaceutically acceptable carriers, and optionally a second antiviral agent selected from an interferon, ribavirin, amantadine, an interleukin, a NS3 protease inhibitor, a cysteine protease inhibitor, a phenathrenequinone, a thiazolidine, a benzanilide, a helicase inhibitor, a polymerase inhibitor, a nucleotide analogue, a liotoxin, acerulenin, an antisense phosphorothioate oligodeoxynucleotide, an inhibitor of IRES-dependent translation, or a ribozyme, for treating or preventing an HCV infection in a subject.