Pharmacokinetics and metabolism of ulixertinib in rat by liquid chromatography combined with electrospray ionization tandem mass spectrometry

The purpose of this study was to develop and validate a simple and sensitive liquid chromatography tandem mass spectrometry method for the determination of ulixertinib in rat plasma. The plasma samples were precipitated with acetonitrile and then separated on a C-18 column with water containing 0.1% formic acid and acetonitrile as mobile phase at a flow rate of 0.3 mL/min. Analytes were monitored on a TSQ Vantage triple quadrupole tandem mass spectrometer operated in positive electrospray ionization mode. Selected reaction monitoring transitions were m/z 433.1 -> 262.1 for ulixertinib and m/z 450.1 -> 260.1 for internal standard. The assay achieved good linearity over the concentration range of 0.1-1000 ng/mL with correlation coefficient > 0.9991. The validated assay has been successfully applied to pharmacokinetic study of ulixertinib in rat after oral and intravenous administration. The results revealed that ulixertinib showed high exposure in rat plasma, low clearance, moderate oral bioavailability (45.13%), and dose-independent pharmacokinetic profiles over the oral dose range of 1-15 mg/kg. In addition, six metabolites from rat plasma and hepatocytes were detected and structurally identified by ultra-high performance liquid chromatography combined with high-resolution mass spectrometry. The metabolic pathways of ulixertinib referred to hydroxylation and dealkylation and glucuronidation.