β-D-2'-α-F-2'-β-C-Methyl-6-O-substituted 3',5'-cyclic phosphate nucleotide prodrugs as inhibitors of hepatitis C virus replication: a structure-activity relationship study.

The 3',5'-cyclic phosphate prodrug 9-[β-d-2'-deoxy-2'-α-fluoro-2'-β-C-methylribofuranosyl]-2-amino-6-ethoxypurine, PSI-352938 1, has demonstrated promising anti-HCV efficacy in vitro and in human clinical trials. A structure-activity relationship study of the nucleoside 3',5'-cyclic phosphate series of β-d-2'-deoxy-2'-α-fluoro-2'-β-C-methylribofuranosyl nucleoside prodrugs was undertaken and the anti-HCV activity and in vitro safety profile were assessed. Cycloalkyl 3',5'-cyclic phosphate prodrugs were shown to be significantly more potent as inhibitors of HCV replication than branched and straight chain alkyl 3',5'-cyclic phosphate prodrugs.