Identification and Characterization of In Vitro Metabolites of Ibrutinib by Rat Liver Microsomes Using Ultra-Performance Liquid Chromatography Coupled with Tandem Mass Spectrometry

Drug metabolism is very important in determining the safety and efficacy of the drug. We worked towards this direction and designed a new strategy to study the in vitro metabolites of Food and Drug Administration approved anticancer drug, ibrutinib which is known to inhibit the Bruton's tyrosine kinase. The metabolites were formed by incubating the drug, ibrutinib with rat liver microsomes, at 37 degrees for 24 h. The newly formed metabolites were identified and characterized with the help of ultra-high performance liquid chromatography which is interlinked with tandem quadrupole time-of-flight mass spectrometry. We then elucidated the structures of our new metabolites based on liquid chromatography with tandem mass spectrometry data which included accurate masses, the fragmentation of ions and chromatographic retention times. This study described the detailed in vitro metabolite profiling of ibrutinib which will be further helpful to predict the in vivo metabolism of ibrutinib in the human body. Enzyme kinetic parameters (K-m and V-max) for both the metabolites were also established using different substrate concentrations. This newly developed biotransformation method will further help in determining the elimination mechanism of ibrutinib which in turn will assist in predicting the effectiveness and toxicity of the drug.