Isothiazoles as active-site inhibitors of HCVNS5B polymerase

Isothiazole analogs were discovered as a novel class of active-site inhibitors of HCV NS5B polyrnerase. The best compound has an IC50 of 200 nM and EC50 of 100 nM, which is a significant improvement over the starting inhibitor (1). The X-ray complex structure of I with HCV NS5B was obtained at a resolution of 2.2 angstrom, revealing that the inhibitor is covalently linked with Cys 366 of the 'primer-grip'. Furthermore, it makes considerable contacts with the C-terminus, P-loop, and more importantly, to the active-site of the enzyme. The uniqueness of this binding mode offers a new insight for the rational design of novel inhibitors for HCV NS5B polymerase. (c) 2006 Elsevier Ltd. All rights reserved.