Structure-based optimization and derivatization of 2-substituted quinolone-based non-nucleoside HCV NS5B inhibitors with submicromolar cellular replicon potency.

HCV NS5B polymerase is an attractive and validated target for anti-HCV therapy. Starting from our previously identified 2-aryl quinolones as novel non-nucleoside NS5B polymerase inhibitors, structure-based optimization furnished 2-alkyl-N-benzyl quinolones with improved antiviral potency by employing privileged fragment hybridization strategy. The N-(4-chlorobenzyl)-2-(methoxymethyl)quinolone derivative 5f proved to be the best compound of this series, exhibiting a selective sub-micromolar antiviral effect (EC50=0.4μM, SI=10.8) in Huh7.5.1 cells carrying a HCV genotype 2a. Considering the undesirable pharmacokinetic property of the highly substituted quinolones, a novel chemotype of 1,6-naphthyridine-4,5-diones were evolved via scaffold hopping, affording brand new structure HCV inhibitors with compound 6h (EC50 (gt2a)=2.5μM, SI=7.2) as a promising hit. Molecular modeling studies suggest that both of 2-alkyl quinolones and 1,6-naphthyridine-4,5-diones function as HCV NS5B thumb pocket II inhibitors.