2′-disubstituted substituted nucleoside derivatives of formula (I) and pharmaceutically acceptable salts thereof are disclosed: (1), wherein A is N3 or NH2 and X, Y, R1, R2, R3, R4, R5 and R18 are as defined herein. Compositions comprising at least one 2′-disubstituted nucleoside derivative, and methods of using the 2′-disubstituted nucleoside derivatives for treating or preventing HCV infection in a patient are disclosed.