title: High-throughput cytochrome P450 inhibition assays using laser diode thermal desorption-atmospheric pressure chemical ionization-tandem mass spectrometry.
abstract: This paper describes the development of a high-throughput method for the analysis of cytochrome P450 (CYP) inhibition assay incubation samples using laser diode thermal desorption interfaced with atmospheric pressure chemical ionization mass spectrometry (LDTD-APCI-MS). Data for the CYP isoforms 3A4, 2D6, 2C9, and 1A2 from competitive inhibition assays are shown. The potential for inhibition of the CYP isoforms was measured by monitoring the level of the metabolites 6beta-hydroxytestosterone (3A4), dextrorphan (2D6), 4'-hydroxydiclofenac (2C9), and acetaminophen (1A2) formed in the presence of drug candidates using an eight-point titration. The analytical method involves plating of the inhibition samples on specially designed 96-well plates with stainless steel bottoms, followed by direct analysis using the LDTD source. Validation of the LDTD-MS method was performed by testing for interferences, reproducibility, dynamic range, ion suppression, and the ability of the source to produce comparable results to previously validated LC-MS methods. IC50 values for each CYP isoform using 33 different test compounds showed excellent agreement between LDTD-APCI-MS and LC-MS methods and literature values where available. Assay analysis time using the LDTD-APCI source is reduced to less than 30 min for a single 96-well plate compared to greater than 10 h using the LC-MS method. The LDTD-APCI-MS and LC-MS methods and results are compared and limitations and future potential for LDTD-APCI-MS are discussed.
authors.affiliation: Merck Frosst Centre for Therapeutic Research, 16711 Trans Canada Highway, Kirkland, QC, Canada H9H 3L1.
authors.forename: Jin
authors.initials: J
authors.lastname: Wu
authors.forename: Christopher S
authors.initials: CS
authors.lastname: Hughes
authors.forename: Pierre
authors.initials: P
authors.lastname: Picard
authors.forename: Sylvain
authors.initials: S
authors.lastname: Letarte
authors.forename: Mireille
authors.initials: M
authors.lastname: Gaudreault
authors.forename: Jean-François
authors.initials: JF
authors.lastname: Lévesque
authors.forename: Deborah A
authors.initials: DA
authors.lastname: Nicoll-Griffith
authors.forename: Kevin P
authors.initials: KP
authors.lastname: Bateman
mesh_terms: D000082:Acetaminophen / Q000032:analysis / Q000378:metabolism; D001274:Atmospheric Pressure; D001667:Binding, Competitive; D001681:Biological Assay / Q000379:methods*; D002853:Chromatography, Liquid / Q000379:methods; D065607:Cytochrome P-450 Enzyme Inhibitors; D003577:Cytochrome P-450 Enzyme System / Q000032:analysis* / Q000378:metabolism; D003917:Dextrorphan / Q000032:analysis / Q000378:metabolism; D004008:Diclofenac / Q000031:analogs & derivatives / Q000032:analysis / Q000378:metabolism; D004791:Enzyme Inhibitors / Q000494:pharmacology*; D006915:Hydroxytestosterones / Q000032:analysis / Q000378:metabolism; D007834:Lasers; D020033:Protein Isoforms / Q000032:analysis / Q000037:antagonists & inhibitors / Q000378:metabolism; D015203:Reproducibility of Results; D019032:Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization / Q000379:methods*; D013997:Time Factors
chemical_list: D065607:Cytochrome P-450 Enzyme Inhibitors; D004791:Enzyme Inhibitors; D006915:Hydroxytestosterones; D020033:Protein Isoforms; D003917:Dextrorphan; D004008:Diclofenac; D000082:Acetaminophen; C025591:6 beta-hydroxytestosterone; D003577:Cytochrome P-450 Enzyme System; C108036:4'-hydroxydiclofenac