Abstract
BACKGROUND: YM758 monophosphate is a novel If channel inhibitor that has an inhibitory action for If current and shows a strong and specific activity, selectively lowering the heart rate and decreasing oxygen consumption by heart muscle. OBJECTIVES: The objectives of the current study were to investigate the in vivo metabolic profiles of YM758 in mice, rats, rabbits, dogs, and monkeys and to elucidate the structures of YM758 metabolites. METHODS: Biological samples were analyzed by liquid chromatography hyphenated with a radiometric detection system and liquid chromatography coupled with a mass spectrometer to clarify their metabolic patterns. To elucidate their structures, metabolites were isolated and analyzed by mass spectrometry and nuclear magnetic resonance spectroscopy. RESULTS: Our results from in vivo metabolic profiling in humans and animals indicated there is no significant species difference in the metabolism of YM758, and the metabolic pathways of YM758 are considered to be oxidation, hydration, and demethylation followed by sulfate or glucuronide conjugation.