We studied the in vitro metabolism of the anti-thyroid-cancer drug vandetanib in a rat animal model and demonstrated that N-desmethylvandetanib and vandetanib N-oxide are formed by NADPH- or NADH-mediated reactions catalyzed by rat hepatic microsomes and pure biotransformation enzymes. In addition to the structural characterization of vandetanib metabolites, individual rat enzymes [cytochrome P450 (CYP) and flavin-containing monooxygenase (FMO)] capable of oxidizing vandetanib were identified. Generation of N-desmethylvandetanib, but not that of vandetanib N-oxide, was attenuated by CYP3A and 2C inhibitors while inhibition of FMO decreased formation of vandetanib N-oxide. These results indicate that liver microsomal CYP2C/3A and FMO1 are major enzymes participating in the formation of N-desmethylvandetanib and vandetanib N-oxide, respectively. Rat recombinant CYP2C11 > >3A1 > 3A2 > 1A1 > 1A2 > 2D1 > 2D2 were effective in catalyzing the formation of N-desmethylvandetanib. Results of the present study explain differences between the CYP- and FMO-catalyzed vandetanib oxidation in rat and human liver reported previously and the enzymatic mechanisms underlying this phenomenon.

• Klíčová slova
• Anti-thyroid-cancer drug, Cytochromes P450, Flavin-containing monoxygenases, Metabolism, Tyrosine kinase inhibitor, Vandetanib,
• MeSH
• chinazoliny metabolismus   MeSH
• jaterní mikrozomy MeSH
• krysa rodu Rattus MeSH
• lidé MeSH
• oxidace-redukce MeSH
• oxygenasy metabolismus   MeSH
• piperidiny metabolismus   MeSH
• protinádorové látky metabolismus   MeSH
• systém (enzymů) cytochromů P-450 metabolismus   MeSH
• zvířata MeSH
• Check Tag
• krysa rodu Rattus MeSH
• lidé MeSH
• zvířata MeSH
• Publikační typ
• časopisecké články MeSH
• Názvy látek
• chinazoliny MeSH
• dimethylaniline monooxygenase (N-oxide forming) MeSH Prohlížeč
• oxygenasy MeSH
• piperidiny MeSH
• protinádorové látky MeSH
• systém (enzymů) cytochromů P-450 MeSH
• vandetanib MeSH Prohlížeč

The metabolism of vandetanib, a tyrosine kinase inhibitor used for treatment of symptomatic/progressive medullary thyroid cancer, was studied using human hepatic microsomes, recombinant cytochromes P450 (CYPs) and flavin-containing monooxygenases (FMOs). The role of CYPs and FMOs in the microsomal metabolism of vandetanib to N-desmethylvandetanib and vandetanib-N-oxide was investigated by examining the effects of CYP/FMO inhibitors and by correlating CYP-/FMO-catalytic activities in each microsomal sample with the amounts of N-desmethylvandetanib/vandetanib-N-oxide formed by these samples. CYP3A4/FMO-activities significantly correlated with the formation of N-desmethylvandetanib/ vandetanib-N-oxide. Based on these studies, most of the vandetanib metabolism was attributed to N-desmethylvandetanib/vandetanib-N-oxide to CYP3A4/FMO3. Recombinant CYP3A4 was most efficient to form N-desmethylvandetanib, while FMO1/FMO3 generated N-oxide. Cytochrome b5 stimulated the CYP3A4-catalyzed formation of N-desmethylvandetanib, which is of great importance because CYP3A4 is not only most efficient in generating N-desmethylvandetanib, but also most significant due to its high expression in human liver. Molecular modeling indicated that binding of more than one molecule of vandetanib into the CYP3A4-active center can be responsible for the high efficiency of CYP3A4 N-demethylating vandetanib. Indeed, the CYP3A4-mediated reaction exhibits kinetics of positive cooperativity and this corresponded to the in silico model, where two vandetanib molecules were found in CYP3A4-active center.

• Klíčová slova
• cytochromes P450, flavin-containing monoxygenases, metabolism, tyrosine kinase inhibitor, vandetanib,
• MeSH
• chinazoliny chemie   farmakologie   MeSH
• cytochrom P-450 CYP3A chemie   metabolismus   MeSH
• enzymy chemie   metabolismus   MeSH
• inhibitory proteinkinas chemie   farmakologie   MeSH
• jaterní mikrozomy metabolismus   MeSH
• králíci MeSH
• krysa rodu Rattus MeSH
• lidé MeSH
• molekulární konformace MeSH
• molekulární modely MeSH
• molekulární struktura MeSH
• myši MeSH
• oxidace-redukce * MeSH
• piperidiny chemie   farmakologie   MeSH
• protinádorové látky chemie   farmakologie   MeSH
• rekombinantní proteiny MeSH
• vztah mezi dávkou a účinkem léčiva MeSH
• zvířata MeSH
• Check Tag
• králíci MeSH
• krysa rodu Rattus MeSH
• lidé MeSH
• myši MeSH
• zvířata MeSH
• Publikační typ
• časopisecké články MeSH
• Názvy látek
• chinazoliny MeSH
• cytochrom P-450 CYP3A MeSH
• enzymy MeSH
• inhibitory proteinkinas MeSH
• piperidiny MeSH
• protinádorové látky MeSH
• rekombinantní proteiny MeSH
• vandetanib MeSH Prohlížeč