title: Activation of the antiviral prodrug oseltamivir is impaired by two newly identified carboxylesterase 1 variants.
abstract: Oseltamivir phosphate is an ethyl ester prodrug widely used in the treatment and prevention of both Influenzavirus A and B infections. The conversion of oseltamivir to its active metabolite oseltamivir carboxylate is dependent on ester hydrolysis mediated by carboxylesterase 1 (CES1). We recently identified two functional CES1 variants p.Gly143Glu and p.Asp260fs in a research subject who displayed significant impairment in his ability to metabolize the selective CES1 substrate, methylphenidate. In vitro functional studies demonstrated that the presence of either of the two mutations can result in severe reductions in the catalytic efficiency of CES1 toward methylphenidate, which is required for hydrolysis and pharmacological deactivation. The aim of the present study was to investigate the function of these mutations on activating (hydrolyzing) oseltamivir to oseltamivir carboxylate using the cell lines expressing wild type (WT) and each mutant CES1. In vitro incubation studies demonstrated that the S9 fractions prepared from the cells transfected with WT CES1 and human liver tissues rapidly convert oseltamivir to oseltamivir carboxylate. However, the catalytic activity of the mutant hydrolases was dramatically hindered. The V(max) value of p.Gly143Glu was approximately 25% of that of WT enzyme, whereas the catalytic activity of p.Asp260fs was negligible. These results suggest that the therapeutic efficacy of oseltamivir could be compromised in treated patients expressing either functional CES1 mutation. Furthermore, the potential for increased adverse effects or toxicity as a result of exposure to high concentrations of the nonhydrolyzed prodrug should be considered.
authors.affiliation: Department of Pharmaceutical and Biomedical Sciences, Laboratory of Drug Disposition and Pharmacogenetics, Charles P. Darby Children's Research Institute, Room 405B, Medical University of South Carolina, Charleston, SC 29425, USA. zhuh@musc.edu
authors.forename: Hao-Jie
authors.initials: HJ
authors.lastname: Zhu
authors.forename: John S
authors.initials: JS
authors.lastname: Markowitz
mesh_terms: D000483:Alleles; D019943:Amino Acid Substitution; D000998:Antiviral Agents / Q000378:metabolism* / Q000494:pharmacology; D002265:Carboxylic Ester Hydrolases / Q000235:genetics / Q000378:metabolism*; D002460:Cell Line; D006801:Humans; D006868:Hydrolysis; D009154:Mutation; D009975:Orthomyxoviridae / Q000187:drug effects; D053139:Oseltamivir / Q000037:antagonists & inhibitors / Q000378:metabolism* / Q000494:pharmacology; D010975:Platelet Aggregation Inhibitors; D011355:Prodrugs / Q000378:metabolism*
chemical_list: D000998:Antiviral Agents; D010975:Platelet Aggregation Inhibitors; D011355:Prodrugs; D053139:Oseltamivir; D002265:Carboxylic Ester Hydrolases; C474609:CES1 protein, human