title: High-throughput cytochrome P450 (CYP) inhibition screening via cassette probe-dosing strategy: III. Validation of a direct injection/on-line guard cartridge extraction-tandem mass spectrometry method for CYP2C19 inhibition evaluation.
abstract: A new direct injection/on-line guard cartridge extraction-tandem mass spectrometry (DI/GCE-MS-MS) method has been validated for high-throughput evaluation of cytochrome P450 (CYP) 2C19 inhibition potential using human hepatic microsomes and 96-well microtiter plates. Microsomal incubations were quenched with formic acid, centrifuged, and the resulting supernatants were injected for DI/GCE-MS-MS analysis. Due to the use of a C(18) guard cartridge (4x2.0 mm I.D.), this method exhibits several advantages such as little sample preparation, rapid on-line extraction, short analysis time (2.5 min), and minimal source contamination and performance deterioration. The DI/GCE-MS-MS method demonstrates an inter-day accuracy ranged from 0.3 to 2.4% with precision ranging from 2.0 to 3.0% for the quantification of 4-hydroxymephenytoin, a marker metabolite of S-mephenytoin mediated by CYP2C19, in microsomal incubations. The CYP2C19 inhibition assay has been validated using tranylcypromine as a known inhibitor of the isoform. The IC(50) value (43.5 microM) measured by the new method is in agreement with a reported literature value (approximately 30 microM).
authors.affiliation: Department of Metabolic Chemistry, Covance Laboratories Inc., 3301 Kinsman Boulevard, Madison, WI 53704, USA. haizhi.bu@cavance.com
authors.forename: H Z
authors.initials: HZ
authors.lastname: Bu
authors.forename: K
authors.initials: K
authors.lastname: Knuth
authors.forename: L
authors.initials: L
authors.lastname: Magis
authors.forename: P
authors.initials: P
authors.lastname: Teitelbaum
mesh_terms: D001189:Aryl Hydrocarbon Hydroxylases; D002138:Calibration; D065731:Cytochrome P-450 CYP2C19; D065607:Cytochrome P-450 Enzyme Inhibitors; D013058:Mass Spectrometry; D006899:Mixed Function Oxygenases / Q000037:antagonists & inhibitors*
chemical_list: D065607:Cytochrome P-450 Enzyme Inhibitors; D006899:Mixed Function Oxygenases; D001189:Aryl Hydrocarbon Hydroxylases; C045793:CYP2C19 protein, human; D065731:Cytochrome P-450 CYP2C19