JTK-853, a novel non-nucleoside hepatitis C virus polymerase inhibitor, demonstrates a high genetic barrier to resistance in vitro.

JTK-853 is a novel, non-nucleoside, palm site-binding hepatitis C virus (HCV) polymerase inhibitor that has demonstrated antiviral activity in HCV-infected patients during 3 days of treatment. To estimate the genetic barrier of JTK-853 to resistance in vitro, colony formation assays were conducted using HCV replicon cells (genotypes 1a and 1b). The colony formation assays revealed that the numbers of resistant colonies for JTK-853 were much lower than those for other direct-acting antivirals, including palm site- or thumb pocket-binding non-nucleoside HCV polymerase inhibitors (NNIs), an NS5A inhibitor (NS5Ai), and a protease inhibitor (PI). Furthermore, the numbers of resistant colonies for JTK-853 in combination with the NS5Ai or PI were lower than those for other combinations of NS5Ai + NNI, and NS5Ai + PI. Our findings demonstrate that JTK-853 has a high genetic barrier to resistance, and suggest that its combination therapies will be potent in suppressing the emergence of drug resistance in HCV-infected patients.