Pritelivir mesylate hydrate (BAY 57-1293 mesylate hydrate), an inhibitor of the viral helicase-primase complex , exhibits antiviral activity in vitro and in animal models of herpes simplex virus ( HSV ) infection . Pritelivir mesylate hydrate is active against herpes simplex virus types 1 and 2 ( HSV-1 and HSV-2 ) with the IC 50 of 0.02 μM against HSV1-2 In Vivo Pritelivir is the first in a class of antiviral agents that inhibit HSV replication by targeting the viral helicase–primase enzyme complex. Pritelivir (0.03-45 mg/kg) significantly increases survival. Pritelivir (0.3-30 mg/kg) reduces mortality against HSV-1, E-377. Pritelivir has potent and resistance-breaking antiviral efficacy with potential for the treatment of potentially life-threatening HSV type 1 and 2 infections, including herpes simplex encephalitis. Combination therapies of Pritelivir at 0.1 or 0.3 mg/kg/dose with Acyclovir (10 mg/kg/dose) are protective when compared to the vehicle treated group against HSV-2, strain MS. MCE has not independently confirmed the accuracy of these methods. They are for reference only. Animal Model: Female BALB/c miceDosage: 0.03 to 45 mg/kg Administration: Administered orally, twice daily at approximately 12 h intervals, for 7 days Result: Survival was significantly increased to 80-100% as compared to the vehicle treatment. Even the lowest dose of 0.3 mg/kg was effective in increasing survival to 53%. Form:Solid IC50& Target:HSV-1 0.02 μM (IC 50 ) HSV-2 0.02 μM (IC 50 )