Tiviciclovir (A188) is a nucleoside analog used in the synthesis of antiviral drugs. This acyclic guanosine analog has a potential for the treatment of hepatitis B virus. However, as with penciclovir and the related compounds acyclovir and ganciclovir, the intestinal absorption of Tiviciclovir is limited. One approach to overcome this is through synthesis of the 6-deoxy prodrug version of AM188, i.e. AM365, which has improved intestinal absorption. Following absorption, the 6-deoxyguanosine analog AM365 is converted to the corresponding anti-virally active guanosine analog, AM188, probably by the liver molybdenum hydroxylases, aldehyde oxidase and xanthine oxidase. Renal tubular secretion of AM188 involves organic anion and cation transport systems.