Antiviral Mechanisms of N-Phenyl Benzamides on Coxsackie Virus A9

Enteroviruses are one of the most abundant groups of viruses infecting humans, and yetthere are no approved antivirals against them. To find effective antiviral compounds against enterovirusB group viruses, an in-house chemical library was screened. The most effective compoundsagainst Coxsackieviruses B3 (CVB3) and A9 (CVA9) were CL212 and CL213, two N-phenyl benzamides.Both compounds were more effective against CVA9 and CL213 gave a better EC50 value of1 μM with high a specificity index of 140. Both drugs were most effective when incubated directlywith viruses suggesting that they mainly bound to the virions. A real-time uncoating assay showedthat the compounds stabilized the virions and radioactive sucrose gradient as well as TEM confirmedthat the viruses stayed intact. A docking assay, taking into account larger areas around the2-and 3-fold axes of CVA9 and CVB3, suggested that the hydrophobic pocket gives the strongestbinding to CVA9 but revealed another binding site around the 3-fold axis which could contributeto the binding of the compounds. Together, our data support a direct antiviral mechanism againstthe virus capsid and suggest that the compounds bind to the hydrophobic pocket and 3-fold axisarea resulting in the stabilization of the virion.