Pritelivir (AIC316, BAY 57-1293) was discovered as a highly potent drug against herpes simplex viruses with a novel mode of action, i.e. inhibition of the viral helicase–primase. A side by side comparison of the oral form against Valtrex™ in patients with genital herpes, showed superiority in phase II testing for Pritelivir. A number of different solid forms have been generated for additional, e.g. systemic, or topical applications.