In vitro activity: Amenamevir a novel class of antiviral agent other than nucleoside compounds, such as aciclovir, valaciclovir and famciclovir. ASP2151 inhibited the in vitro replication of HSV-1 with a mean 50% effective concentration (EC(50)) of 14 ng/ml.

Kinase Assay: Amenamevir (formerly known as ASP2151) is a HSV (herpes simplex virus) helicase-primase inhibitor with potent antiviral activity against HSVs with EC50 of 14 ng/mL.

Cell Assay: The antiviral activities of Amenamevir (ASP2151) and ACV against HSVs are tested using a plaque reduction assay. Briefly, HEF cells are seeded into multi well plates and incubated until they form a monolayer. After the medium is removed, the cells are infected with HSV-1 or HSV-2, and the plates are further incubated for 1 h at 37°C. The cells are washed twice with maintenance medium and then treated with the test compound (including Amenamevir) until clear plaques appear. The cells are then fixed with 10% formalin in phosphate-buffered saline, stained with a 0.02% crystal violet solution, and the number of plaques is determined under a light microscope. The EC50, which represents the concentration of test compound needed to reduce the plaque number by 50%, is calculated using nonlinear regression analysis with a sigmoid-maximum effect (Emax) model.