Aminopyridines Antineoplastic Agents Article Benzimidazoles Chromatography, High Pressure Liquid Humans Molecular Structure abemaciclib aminopyridine derivative analytic method antineoplastic agent benzimidazole derivative bioanalysis chemical structure clinical sample analysis combination drugs controlled study drug isolation drug metabolite drug stability drug structure first in human study fit-for-purpose hemolysis high performance liquid chromatography human in vitro study in vivo study incurred sample reanalysis limit of quantitation