Our research team has been pursuing inhibition of the Hepatitis C virus by targeting several non-structural viral enzymes. 5 We have also initiated a broad screening program towards identifying novel leads that have antiviral potency in a HCV subgenomic replicon assay. 6 One such lead was a substituted naphthyridine derivative (1), shown in Table 1. We were pleased with the genotype 1b replicon potency of (EC 50 18 nM) as a starting point and hoped to improve upon the ...