Broad-spectrum antiviral activity of PNU-183792, a 4-oxo-dihydroquinoline, against human and animal herpesviruses

We identified a novel class of 4-oxo-dihydroquinolines represented by PNU-183792 which specifically inhibit herpesvirus polymerases. PNU-183792 was highly active against human cytomegalovirus (HCMV, IC 50 value 0.69 μM), varicella zoster virus (VZV, IC 50 value 0.37 μM) and herpes simplex virus (HSV, IC 50 value 0.58 μM) polymerases but was inactive (IC 50 value >40 μM) against human alpha (α), gamma (γ), or delta (δ) polymerases. In vitro antiviral activity against HCMV was determined using cytopathic effect, plaque reduction and virus yield reduction assays (IC 50 ranging from 0.3 to 2.4 μM). PNU-183792 antiviral activity against both VZV (IC 50 value 0.1 μM) and HSV (IC 50 ranging from 3 to 5 μM) was analyzed using plaque reduction assays. PNU-183792 was also active (IC 50 ranging 0.1–0.7 μM) in cell culture assays against simian varicella virus (SVV), murine cytomegalovirus (MCMV) and rat cytomegalovirus (RCMV). Cell culture activity was compared with the appropriate licensed drugs ganciclovir (GCV), cidofovir (CDV) and acyclovir (ACV). PNU-183792 was also active against both GCV-resistant and CDV-resistant HCMV and against ACV-resistant HSV. Toxicity assays using four different species of proliferating mammalian cells indicated PNU-183792 was not cytotoxic at relevant drug concentrations (CC 50 value >100 μM). PNU-183792 was inactive against unrelated DNA and RNA viruses indicating specificity for herpesviruses. In animals, PNU-183792 was orally bioavailable and was efficacious in a model of lethal MCMV infection.