title: LC-MS/MS determination of a farnesyl transferase inhibitor in human plasma and urine.
abstract: To support clinical pharmacokinetic studies in cancer patients, sensitive and specific methods for measuring 4-[1-(4-cyanobenzyl)-5-imidazolylmethyl]-1-(3-chlorophenyl) piperazinone (I), a farnesyl transferase inhibitor (FTI), in human plasma and urine were developed and validated. The methods are based on high-performance liquid chromatography (HPLC) with atmospheric pressure chemical ionization (APCI) and tandem mass spectrometric (MS/MS) detection in the positive ion mode using a heated nebulizer interface. Drug and internal standard were isolated from plasma or basified urine using automated solid-phase extraction on cyano cartridges. The organic extracts were dried, reconstituted in aqueous acetonitrile and injected into the system. Chromatographic separation of I and internal standard (IS) was achieved using a BDS Hypersil C8 analytical column, with a mobile phase consisting of acetonitrile:methanol:water (50:4:46) and trifluoroacetic acid (0.05%) at a flow rate of 0.6 ml/min. MS/MS detection was performed on a PE-Sciex API 300 tandem mass spectrometer operated in selected reaction monitoring mode. The parent-->product ions monitored were m/z 406-->195 for analyte I and m/z 448-->195 for the internal standard. Unusual in this method is that quantitation is accomplished using a secondary product ion, m/z 195, of drug I and IS. The assays were validated over the concentration range of 0.5-1000 ng/ml (1.2 nM to 2.5 microM, respectively) in plasma, and 2.5-500 ng/ml (6.2 nM to 1.23 microM) in urine. Accuracy was within +/-10% of nominal concentration at all levels in urine, and all but the lowest standard in plasma (+/-14% at 0.5 ng/ml). Intraday precision (expressed as coefficients of variation, CVs) for standard replicates and interday precision for quality control (QC) samples were less than 8% at all concentrations in both matrices. Detailed descriptions of the extraction procedure and analytical methodology used in the assay of I in plasma and urine are presented. This procedure may have utility in the quantitation of other imidazole-based FTIs with cyanobenzyl substructures.
authors.affiliation: Department of Drug Metabolism, Merck Research Laboratories, WP75A-303, 19486, West Point, PA, USA.
authors.forename: M E
authors.initials: ME
authors.lastname: DePuy
authors.forename: D G
authors.initials: DG
authors.lastname: Musson
authors.forename: S
authors.initials: S
authors.lastname: Yu
authors.forename: A L
authors.initials: AL
authors.lastname: Fisher
mesh_terms: D019883:Alkyl and Aryl Transferases / Q000037:antagonists & inhibitors*; D004791:Enzyme Inhibitors / Q000097:blood* / Q000737:chemistry / Q000652:urine*; D051231:Farnesyltranstransferase; D006801:Humans; D013058:Mass Spectrometry / Q000379:methods
chemical_list: D004791:Enzyme Inhibitors; D019883:Alkyl and Aryl Transferases; D051231:Farnesyltranstransferase