title: In vitro characterization of the human biotransformation pathways of aplidine, a novel marine anti-cancer drug.
abstract: Aplidine is a potent marine anti-cancer drug and is currently being investigated in phase II clinical trials. However, the enzymes involved in the biotransformation of aplidine and thus its pharmacokinetics are not known yet. To assess the biotransformation pathways of aplidine and their potential implications for human pharmacology and toxicology, the in vitro metabolism of aplidine was characterized using incubations with human plasma, liver preparations, cytochrome P450 (CYP) and uridine diphosphoglucuronosyl transferase (UGT) supersomes in combination with HPLC analysis and cytotoxicity assays with cell lines. Aplidine was metabolised by carboxyl esterases in human plasma. Using CYP supersomes and liver microsomes, it was shown that aplidine was metabolised mainly by CYP3A4 and also by CYP2A6, 2E1 and 4A11. Four metabolites were observed after incubation with human liver microsomes, one formed by CYP2A6 (C-demethylation) and three by CYP3A4 (hydroxylation and/or C-dealkylation). No conjugation was observed in human liver S9 fraction. However, the aplidine metabolites formed by CYP were further conjugated by the phase II enzymes UGT, GST and SULT. In accordance with the findings in microsomes and CYP supersomes, a significant effect of specific CYP2A6, 2E1, 3A4 and 4A11 inhibitors on the cytotoxicity of aplidine in Hep G2 and IGROV-1 cells could be observed. These results provide evidence that CYP3A4 has a major role in metabolising aplidine in vitro with additional involvement of CYP2A6, 2E1, and 4A11. Further, the metabolites formed by CYPs can be conjugated by UGT, SULT and GST. These findings could help interpret the in vivo pharmacokinetics of aplidine.
authors.affiliation: Department of Pharmaceutical Sciences, Section of Biomedical Analysis, Division of Drug Toxicology, Utrecht University, Utrecht, The Netherlands.
authors.forename: Esther F A
authors.initials: EF
authors.lastname: Brandon
authors.forename: Rolf W
authors.initials: RW
authors.lastname: Sparidans
authors.forename: Ronald D
authors.initials: RD
authors.lastname: van Ooijen
authors.forename: Irma
authors.initials: I
authors.lastname: Meijerman
authors.forename: Luis Lopez
authors.initials: LL
authors.lastname: Lazaro
authors.forename: Ignacio
authors.initials: I
authors.lastname: Manzanares
authors.forename: Jos H
authors.initials: JH
authors.lastname: Beijnen
authors.forename: Jan H M
authors.initials: JH
authors.lastname: Schellens
mesh_terms: D000970:Antineoplastic Agents / Q000737:chemistry / Q000378:metabolism* / Q000493:pharmacokinetics; D001189:Aryl Hydrocarbon Hydroxylases / Q000378:metabolism; D045744:Cell Line, Tumor; D002470:Cell Survival / Q000187:drug effects; D002851:Chromatography, High Pressure Liquid / Q000379:methods; D065637:Cytochrome P-450 CYP2A6; D051544:Cytochrome P-450 CYP3A; D003577:Cytochrome P-450 Enzyme System / Q000378:metabolism; D003600:Cytosol / Q000201:enzymology; D047630:Depsipeptides / Q000737:chemistry / Q000378:metabolism* / Q000493:pharmacokinetics; D005260:Female; D014453:Glucuronosyltransferase / Q000378:metabolism; D006207:Half-Life; D006801:Humans; D008099:Liver / Q000187:drug effects / Q000201:enzymology / Q000378:metabolism; D008297:Male; D050217:Metabolic Detoxication, Phase II; D008862:Microsomes, Liver / Q000187:drug effects / Q000201:enzymology / Q000378:metabolism; D006899:Mixed Function Oxygenases; D015394:Molecular Structure; D009596:Nitrophenols / Q000494:pharmacology; D010456:Peptides, Cyclic; D010664:Phenylmethylsulfonyl Fluoride / Q000494:pharmacology; D013056:Spectrophotometry, Ultraviolet / Q000379:methods; D013347:Subcellular Fractions / Q000201:enzymology
chemical_list: D000970:Antineoplastic Agents; D047630:Depsipeptides; D009596:Nitrophenols; D010456:Peptides, Cyclic; D010664:Phenylmethylsulfonyl Fluoride; C002887:bis(4-nitrophenyl)phosphate; D003577:Cytochrome P-450 Enzyme System; D006899:Mixed Function Oxygenases; D001189:Aryl Hydrocarbon Hydroxylases; C585710:CYP2A6 protein, human; D065637:Cytochrome P-450 CYP2A6; D051544:Cytochrome P-450 CYP3A; C510163:CYP3A4 protein, human; D014453:Glucuronosyltransferase; C098980:plitidepsin