1. The metabolites of fimasartan (FMS), a new angiotensin II receptor antagonist, were characterized in human liver microsomes (HLM) and human subjects. 2. We developed a method for a simultaneous quantitative and qualitative analysis using predictive multiple reaction monitoring information-dependent acquisition-enhanced product ion scanning. To characterize metabolic reactions, FMS metabolites were analyzed using quadrupole-time of flight mass spectrometer in full-scan mode. 3. The structures of metabolites were confirmed by comparison of chromatographic retention times and mass spectra with those of authentic metabolite standards. 4. In the cofactor-dependent microsomal metabolism study, the half-lives of FMS were 56.7, 247.9 and 53.3 min in the presence of NADPH, UDPGA and NADPH + UDPGA, respectively. 5. The main metabolic routes in HLM were S-oxidation, oxidative desulfuration, n-butyl hydroxylation and N-glucuronidation. 6. In humans orally administered with 120 mg FMS daily for 7 days, the prominent metabolites were FMS S-oxide and FMS N-glucuronide in the 0-8-h pooled plasma sample of each subject. 7. This study characterizes, for the first time, the metabolites of FMS in humans to provide information for its safe use in clinical medicine.
Keywords: Fimasartan; metabolic stability; metabolite identification; qualitative and quantitative analysis.