Metabolite profiling of remibrutinib in rat and human liver microsomes using liquid chromatography combined with benchtop orbitrap high‐resolution mass spectrometry

Abstract Remibrutinib is a potent and highly selective covalent Bruton's tyrosine kinase inhibitor that is undergoing clinical development for the treatment of autoimmune diseases. The present study was undertaken to investigate the in vitro metabolism of remibrutinib and to propose its biotransformation pathways. The metabolites were generated by incubating remibrutinib (2 μ m ) with human and rat liver microsomes at 37°C for 30 min. Ultra‐high‐performance liquid chromatography combined with benchtop orbitrap high‐resolution mass spectrometry was used to identify and characterize the metabolites of remibrutinib. Compound Discoverer software was employed to process the acquired data. In rat liver microsomes, a total of 18 metabolites have been identified and characterized among which three (M8, M12 and M13) were identified as the most abundant metabolites. In human liver microsomes, a total of 16 metabolites have been identified, and M8 and M12 were identified as the predominant metabolites. All the metabolites were nicotinamide adenine dinucleotide phosphate dependent. The major metabolic changes were found to be oxygenation, dealkylation, demethylation, epoxidation and hydrolysis. The present study comprehensively reports the in vitro metabolism of remibrutinib mentioning 20 metabolites. These findings will help investigation of remibrutinib disposition and safety evaluation.