N-[5-[(4-Ethyl-1-piperazinyl-2,2,3,3,5,5,6,6-d8)methyl]-2-pyridinyl]-5-fluoro-4-[4-fluoro-2-methyl-1-(1-methylethyl)-1H-benzimidazol-6-yl]-2-pyrimidinamine,N-(5-((4-Ethylpiperazin-1-yl-2,2,3,3,5,5,6,6-d8)methyl)pyridin-2-yl)-5-fluoro-4-(4-fluoro-1-isopropyl-2-methyl-1H-benzo[d]imidazol-6-yl)pyrimidin-2-amine,Abemaciclib Stable Isotopes