BMS-791325 is a hepatitis C virus (HCV) inhibitor binding to the thumb domain of the NS5B RNA-dependent RNA polymerase. BMS-791325 is well characterized in genotype 1 (GT1) and exhibits good inhibitory activity (50% effective concentration [EC 50 ], <10 nM) against hybrid replicons containing patient NS5B sequences from GT3a, -4a, and -5a while potency against GT2 is significantly reduced (J. A. Lemm et al., Antimicrob. Agents Chemother. 58:3485-3495, 2014, doi:http://dx.doi.org/10.1128/AAC.02495-13). BMS-791325 potency against GT6a hybrid replicons is more variable, with two of three hybrid clones having EC 50 s similar to that for GT1 while a third patient clone was ϳ10 times less susceptible to BMS-791325. To characterize the resistance profile of BMS-791325 beyond GT1, curing studies were performed across GT1a and -3a to -6a and demonstrated that GT1a has the highest resistance barrier versus BMS-791325 while GT6a has the lowest. Selection of GT3 to -6 NS5B chimeric replicon cells at different concentrations of BMS-791325 revealed substitutions in the thumb domain of NS5B at residues 494 and 495 that conferred different levels of resistance to BMS-791325 but remained susceptible to NS5A or NS3 protease inhibitors. In addition, we demonstrate that the reduced potency of BMS-791325 against one GT6a patient is due to an A494 polymorphism present in ϳ21% of sequences in the European HCV database. The results from this report suggest that BMS-791325 is a candidate for combination treatment of HCV GT3 to -6 chronic infections, and the resistance profiles identified will provide useful information for future clinical development.

The development of a series of novel 7-azabenzofurans exhibiting pan-genotype inhibition of HCV NS5B polymerase binding to the primer grip site is presented. Many challenges, including poor oral bioavailability, high clearance, bioactivation, high human serum shift, and metabolic stability were encountered and overcome through SAR studies. This work culminated in the selection of BMS-986139 () as a preclinical candidate.

Iterative structure-activity analyses in a class of highly functionalized furo[2,3-]pyridines led to the identification of the second generation pan-genotypic hepatitis C virus NS5B polymerase primer grip inhibitor BMT-052 (), a potential clinical candidate. The key challenge of poor metabolic stability was overcome by strategic incorporation of deuterium at potential metabolic soft spots. The preclinical profile and status of BMT-052 () is described.