Simultaneous LC-MS-MS Determination of HM30181A, [2-(2-{4-[2-(6,7-Dimethoxy-3,4-dihydro-1H-isoquinolin-2-yl)-ethyl]-phenyl}-2H-tetrazol-5-yl)-4,5-dimethoxyphenyl]amide, as a new P-Glycoprotein Inhibitor and Its Two Metabolites, M1 and M2, in Human Plasma: Application to a Pharmacokinetic Study

A simultaneous simple, rapid, and sensitive LC-MS-MS method was developed and validated for the determination of HM30181A, [2-(2-{4-[2-(6,7-dimethoxy-3,4-dihydro-1H-isoquinolin-2-yl)-ethyl]-phenyl}-2H-tetrazol-5-yl]-4,5-dimethoxy-phenyl]amide, as a P-glycoprotein inhibitor and its two metabolites, M1 and M2, in human plasma using docetaxel as an internal standard (IS). The analytes were extracted from 200 μL of biological sample by liquid-liquid extraction using 1 mL of methyl-t-butyl ether. Chromatographic separation was carried on a Luna C8 column at 30 °C with mobile phase consisting of distilled water with 0.1% formic acid and acetonitrile (75:25, v/v) at a flow rate of 0.7 mL min⁻¹ for human plasma samples. The method was linear over concentration ranges of 0.5-50, 0.1-10, and 0.1-10 ng mL⁻¹ for HM30181A, M1, and M2, respectively, in human plasma. The values of coefficient variation for the assay precision were