Potent helicase-primase inhibitor (HPI) effective against herpes simplex virus (HSV) infections with IC50 value of 20 nM for inhibition of the replication of both HSV-1 and HSV-2 in Vero cells, and ED50 value of 0.5 mg/kg for both HSV-1 and HSV-2 in the murine lethal challenge model of disseminated herpes. BAY 57-1293 in vivo was found to be superior compared to all compounds currently used to treat HSV infections, and is active also against acyclovir-resistant mutant strains which carry mutations in the tk or DNA pol genes.