IDX375

IDX375 is a discontinued small molecule nonnucleoside inhibitor (NNI) of the hepatitis C virus (HCV) NS5B RNA-dependent RNA polymerase (RdRp). Developed initially by Idenix Pharmaceuticals and subsequently by Merck, it belongs to the benzophosphadiazine chemical class, designed using bioisosterism between sulfonamide and phosphonamide. IDX375 acts as an allosteric inhibitor, specifically binding to the palm region of the NS5B polymerase to disrupt viral replication. It demonstrated potency against HCV genotypes 1a and 1b and exhibited a long elimination half-life of approximately 60-63 hours in early clinical studies.