PNU-183792, a 4-oxo-dihydroquinoline, is an orally active HSV polymerases inhibitor. PNU-183792 shows a broad-spectrum antiviral activity, with IC50 values of 0.69 μM, 0.37 μM and 0.58 μM for human cytomegalovirus (HCM), varicella zoster virus and HSV polymerases, respectively. PNU-183792 is inactive against human α, γ and δ polymerases. PNU-183792 also inhibits simian varicella virus (SVV), murine cytomegalovirus (MCMV) and rat cytomegalovirus (RCMV) [1].