Treatments for flaviviridae virus infection

A method for treating an infection by a virus which is a member of the Flaviviridae family of viruses, in a mammalian host, comprising administering to said host a therapeutically effective amount of a compound represented by structural formula IV

• or a pharmaceutically acceptable salt thereof or a pharmaceutical composition thereof which composition comprises a pharmaceutically acceptable carrier;
• wherein R3 and R4 are independently —OH or a pharmaceutically acceptable leaving group, wherein R5 is —OH, a straight or branched chain C9 to C24 alkylphosphate or a straight or branched chain C9 to C24 alkenylphosphate group or a pharmaceutically acceptable leaving group and wherein R1 and R2 are independently C1 to C10 alkyl or wherein R1 and R2 taken together with N form a C3 to C7 ring represented by the following structural formula:
• wherein n and m are independently 0, 1, 2 or 3 and Q is CH2, NR, O, S, SO or SO2;
• and R is independently H, C1 to C6 alkyl or C1 to C6 acyl or wherein R1 and R2, taken together with the N, are represented by the structural formula:
• and wherein said pharmaceutically acceptable leaving groups groups are capable of being converted to —OH, -phosphate, —F or —CH3 when the compound of structural formula IV is administered in vivo and are independently represented by structural formula
• wherein Y═H, CH3, CH3CH2—, CH3CH2CH2—, Me2CH—, Me2CH2CH2—, CH3CH2CH(Me)—, PhCH2—, HOOCCH2CH2—, HSCH2—, HOOCCH2—, MeSCH2CH2—, HOCH2—,
• H2N(CH2)4—, or CH3CH(OH)—, or a pharmaceutically acceptable salt thereof, or Y, taken together with the alpha-carbon and N, form
• or wherein the pharmaceutically acceptable leaving groups are capable of being converted to —OH, -phosphate, —F or —CH3 when the compound of structural formula IV is administered in vivo and are independently represented by a structural formula selected from the group consisting of:
• in association with one or more further chemotherapeutic agents.