Quantitative Analysis of the Active Metabolite of VX‐150 Using UPLC–MS/MS: A Preclinical Pharmacokinetic Study in Rats

VX‐150 is an orally prodrug that rapidly convert into the active metabolite (VX‐150M), which is a highly selective NaV1.8 blocker. In this study, in vitro permeability, protein binding, metabolic stability, and in vivo pharmacokinetics in rats of VX‐150M were characterized. A simple and sensitive liquid chromatography tandem mass spectrometric method was developed and validated for the determination of VX‐150M in rat plasma. The analyte was extracted from plasma sample by protein precipitation and separated on a Waters ACQUITY BEH C18 column (1.7 μm, 2.1 × 50 mm) using 0.1% formic acid in water and acetonitrile as mobile phase. The MS detection was performed in positive multiple reactions monitoring (MRM) mode. The assay was validated over the range of 1–2000 ng/mL with correlation coefficient ( r ) > 0.995. The validation parameters including specificity, carry‐over effect, accuracy and precision, matrix effect, recovery, and stability were all within the acceptable limits. The method was successively applied to investigate the pharmacokinetics of VX‐150M in rats. After intravenous administration (1 mg/kg), VX‐150M was eliminated from plasma with terminal half‐life of 1.33 h and low clearance of 8.91 mL/min/kg. After oral administration at doses of 5, 10, 20 mg/kg, VX‐150M reached the peak concentration at 0.19–0.36 h. System exposure increased linearly with increasing dose and oral bioavailability ranged from 26.67% to 36.11%. In vitro study suggested that VX‐150M had a moderate permeability (6.1 × 10 −6 cm/s) in Caco‐2 cells, high binding to plasma protein (96.2%–97.5%), and low turn‐over in human liver microsomes. These findings were meaningful for understanding the in vitro‐to‐in vivo correlation and supporting its continued development.