title: Comparative studies on the cytochrome p450-associated metabolism and interaction potential of selegiline between human liver-derived in vitro systems.
abstract: Selegiline was used as a model compound in a project aimed at comparing, evaluating, and integrating different in vitro approaches for the prediction of cytochrome p450 (p450)-catalyzed hepatic drug metabolism in humans (EUROCYP). Metabolic predictions were generated using homology modeling, cDNA-expressed p450 enzymes, human liver microsomes, primary cultured human hepatocytes, and precision-cut human liver slices. All of the in vitro systems correctly indicated the formation of two dealkylated metabolites, desmethylselegiline and methamphetamine. The metabolic instability of selegiline was demonstrated by all of the in vitro systems studied. Estimates of clearance varied from 16 l/h to 223 l/h. With the exception of one approach, all systems underpredicted the in vivo clearance in humans (236 l/h). Despite this, all approaches successfully classified selegiline as a high clearance compound. Homology modeling suggested the participation of CYP2B6 in the demethylation of selegiline and of CYP2D6 in the depropargylation of the drug. Studies with recombinant expressed enzymes and with human hepatic microsomal fraction supported the involvement of CYP2B6 but not of CYP2D6. These techniques also suggested the involvement of CYP1A2, CYP2C8, and CYP2C19 in the biotransformation of selegiline. In vitro, CYP2B6 was the most active form of p450 involved in selegiline metabolism. Metabolism by several enzymes operating in parallel implies a low interaction potential for the drug. None of the techniques alone was able to predict all aspects of the metabolic and kinetic behavior of selegiline in vivo. However, when used as an integrated package, all significant characteristics were predictable.
authors.affiliation: Orion Pharma Preclinical and Clinical R&D, Turku, Finland. jarmo.salonen@orionpharma.com
authors.forename: Jarmo S
authors.initials: JS
authors.lastname: Salonen
authors.forename: Leena
authors.initials: L
authors.lastname: Nyman
authors.forename: Alan R
authors.initials: AR
authors.lastname: Boobis
authors.forename: Robert J
authors.initials: RJ
authors.lastname: Edwards
authors.forename: Patricia
authors.initials: P
authors.lastname: Watts
authors.forename: Brian G
authors.initials: BG
authors.lastname: Lake
authors.forename: Roger J
authors.initials: RJ
authors.lastname: Price
authors.forename: Anthony B
authors.initials: AB
authors.lastname: Renwick
authors.forename: Maria-Jose
authors.initials: MJ
authors.lastname: Gómez-Lechón
authors.forename: José V
authors.initials: JV
authors.lastname: Castell
authors.forename: Magnus
authors.initials: M
authors.lastname: Ingelman-Sundberg
authors.forename: Mats
authors.initials: M
authors.lastname: Hidestrand
authors.forename: Andre
authors.initials: A
authors.lastname: Guillouzo
authors.forename: Laurent
authors.initials: L
authors.lastname: Corcos
authors.forename: Peter S
authors.initials: PS
authors.lastname: Goldfarb
authors.forename: David F V
authors.initials: DF
authors.lastname: Lewis
authors.forename: Päivi
authors.initials: P
authors.lastname: Taavitsainen
authors.forename: Olavi
authors.initials: O
authors.lastname: Pelkonen
mesh_terms: D002478:Cells, Cultured; D003577:Cytochrome P-450 Enzyme System / Q000378:metabolism*; D004347:Drug Interactions; D004791:Enzyme Inhibitors / Q000737:chemistry / Q000378:metabolism / Q000494:pharmacology*; D022781:Hepatocytes / Q000378:metabolism; D006801:Humans; D066298:In Vitro Techniques; D007527:Isoenzymes / Q000378:metabolism; D008862:Microsomes, Liver / Q000378:metabolism*; D008958:Models, Molecular; D011994:Recombinant Proteins / Q000378:metabolism; D012642:Selegiline / Q000737:chemistry / Q000378:metabolism / Q000494:pharmacology*
chemical_list: D004791:Enzyme Inhibitors; D007527:Isoenzymes; D011994:Recombinant Proteins; D012642:Selegiline; D003577:Cytochrome P-450 Enzyme System