Discovery of Novel Nucleotide Prodrugs with Improved Potency Against HCV Variants Carrying NS5B S282T Mutation

Resistant HCV variants carrying NS5B S282T mutation confer reduced sensitivity to sofosbuvir, the sole marketed NS5B polymerase inhibitor. On the basis of the finding that 2′-α-F-2′-β-<i>C</i>-methylcytidine 5′-triphosphate (<b>8</b>) was more potent than sofosbuvir’s active metabolite on inhibition of both wild-type and S282T mutant polymerase, a dual-prodrug approach has been established. Twenty-nine phosphoramidates with <i>N</i>⁴-modified cytosine were designed, synthesized, and evaluated for anti-HCV activity. The results showed that compounds <b>4c</b>–<b>4e</b> and <b>4m</b> (EC₅₀ = 0.19–0.25 μM) exhibited comparable potency to that of sofosbuvir (EC₅₀ = 0.15 μM) on inhibition of wild-type replicons. Notably, <b>4c</b> (EC₅₀ = 0.366 μM) was 1.5-fold more potent than sofosbuvir (EC₅₀ = 0.589 μM) on inhibition of S282T mutant replicons. In vitro metabolic studies disclosed the possible metabolic pathways of <b>4c</b>. The toxicity study results indicated a good safety profile of <b>4c</b>. Together, <b>4c</b>–<b>4e</b> and <b>4m</b> hold promise for drug development for the treatment of HCV infection, especially the resistant variants with NS5B S282T mutation