Mifepristone-13C,d3 is the 13C- and deuterium labeled Mifepristone. Mifepristone (RU486) is a progesterone receptor (PR) and glucocorticoid receptor (GR) antagonist with IC50s of 0.2 nM and 2.6 nM in in vitro assay[1]. Mifepristone-13C,d3 is a click chem