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.