Abstract
Rapid determination of in vitro metabolic stability and metabolite profiling of new chemical entities using microsomes or other liver preparations is one of the most important steps in drug discovery. In this paper, we report the use of liquid chromatography-hybrid triple quadrupole/linear ion trap mass spectrometry for the simultaneous analysis of metabolic stability, metabolite profiling, and the kinetics of metabolite formation of praziquantel and three structural analogs. Multiple reaction monitoring (MRM) scans were used to quantify the disappearance of parent compounds and the formation of metabolites. MRM-information dependent acquisition-enhanced product ion (MRM-IDA-EPI) scans were used for the identification of the metabolites formed. Metabolic stability of these anthelmintics were studied in human liver microsomes (HLM) using MRM as a survey scan, which resulted in the identification of a higher number of metabolites compared to neutral loss (NL), precursor ion (PI), and enhanced mass spectrometry (EMS) scans. MRM-IDA-EPI scans resulted in the generation of similar calibration curves to MRM-only quantitative analysis. Therefore, the quantitative capabilities of the method was not affected by the additional qualitative information obtained during the same run. The formation of major metabolites was also simultaneously monitored, which could be used to understand the kinetics and mechanism of metabolite formation. Finally, our data demonstrate that the three analogs had higher metabolic stability than the anthelmintic prototype (praziquantel).