<prompt> Mechanism of action of Acyclov ir isInhibitor of viral DNA polymeraseInhibitor of viral thymidine kinaseInhibitor of viral reverse transcriptaseInhibitor of HSV polymerase  <response>: D Inhibitor of HSV polymerase Mechanism of action: Acyclovir differs from previous nucleoside analogues in containing only a partial nucleoside structure: the sugar ring is replaced with an open-chain structure. It is selectively converted into acyclo-guanosine monophosphate acyclo-GMP by viral thymidine kinase, which is far more effective 3000 times in phosphorylation than cellular thymidine kinase.ANTIVIRAL AGENTS ACTIVE AGA HERPESVIRUSESAgentDescription AcyclovirInhibits HSV polymerase FamciclovirProdrug of penciclovir a guanosine analogue ValacyclovirProdrug of acyclovir; better absorption GanciclovirMore potent polymerase inhibitor; more toxic than acyclovir ValganciclovirProdrug of ganciclovir; better absorption CidofovirNucleotide analogue of cytosine FoscarnetPhosphonoformic acid; inhibits viral DNA polymerase 