Methods and compositions for treating hepatitis C virus

A method for the treatment of a hepatitis C virus infection in a host, comprising administering an anti-virally effective amount of a β-D nucleoside compound of formula:

• or a pharmaceutically acceptable salt or ester thereof, wherein:
• Base is a triazolopyridine, imidazolopyridine, or pyrazolopyrimidine;
• R1 is independently H;
• phosphate;
• stabilized phosphate prodrug;
• acyl;
• alkyl;
• sulfonate ester;
• benzyl, wherein the phenyl group is optionally substituted with one or more substituents selected from the group consisting of hydroxyl, amino, alkylamino, arylamino, alkoxy, aryloxy, nitro, cyano, sulfonic acid, sulfate, phosphonic acid, phosphate, and phosphonate;
• a lipid;
• an amino acid;
• a carbohydrate;
• a peptide;
• cholesterol;
• or a pharmaceutically acceptable leaving group which when administered in vivo provides a compound wherein R1 is independently H or phosphate;
• R6 is alkyl, lower alkyl, alkynyl, —C(O)O(alkyl), —C(O)O(lower alkyl), —O(acyl), —O(lower acyl), —O(alkyl), —O(lower alkyl), —O(alkenyl), chloro, bromo, fluoro, iodo, NO2, NH2, —NH(lower alkyl), —NH(acyl), —N(lower alkyl)2, or —N(acyl)2;
• R7 and R9 are independently OR1, hydroxy, alkyl, lower alkyl, azido, cyano, alkenyl, alkynyl, Br-vinyl, —C(O)O(alkyl), —C(O)O(lower alkyl), —O(acyl), —O(lower acyl), —O(alkyl), —O(lower alkyl), —O(alkenyl), chlorine, bromine, iodine, NO2, NH2, —NH(lower alkyl), —NH(acyl), —N(lower alkyl)2, or —N(acyl)2;
• R10 is H, alkyl, lower alkyl, chlorine, bromine or iodine;
• and
• X is O, S, SO2 or CH2.