Identification of the metabolites of tofacitinib in liver microsomes by liquid chromatography combined with high resolution mass spectrometry.

Tofacitinib is an orally available Janus kinase inhibitor. The aim of this study was to investigate the metabolism of tofacitinib in mouse, rat, monkey, and human liver microsomes fortified with β-nicotinamide adenine dinucleotide phosphate tetrasodium salt and uridine diphosphate glucuronic acid. The biotransformation was executed at a temperature of 37°C for 60 min, and the samples were analyzed by ultra-high performance liquid chromatography combined with high-resolution mass spectrometry (UHPLC-HRMS) operated in positive electrospray ionization mode.