Page - (000222) - in Biomedical Chemistry: Current Trends and Developments

Figure 3.1.6: Bioconversion of valacyclovir and valganciclovir to their parent drugs by valacyclovirase and to their corresponding triphosphates, firstly by thymidine kinase and secondly by cellular kinases. The successful results obtained for valacyclovir and valganciclovir, amino acid ester prodrugs of acyclovir and ganciclovir, respectively, has prompted the investigations of amino acids as promoieties for other agents. This success has been attributed to their enhanced intestinal transport via oligopeptide transporters. The work of Han prove that amino acid ester prodrugs significantly improve the cellular uptake of the parent drugs via peptide transport mechanism, though there is no peptide bond in their structures (Han, 1998). The fact that some cancer epithelial cells are rich in this type of transporter suggests their use for