4-[5,6-Dihydro-2-[3-methyl-1-(1-methylethyl)-1H-1,2,4-triazol-5-yl]imidazo[1,2-d][1,4]benzoxazepin-9-yl]-α,α-dimethyl-1H-pyrazole-1-acetamide-d7 is the labeled analogue of 4-[5,6-Dihydro-2-[3-methyl-1-(1-methylethyl)-1H-1,2,4-triazol-5-yl]imidazo[1,2-d][1,4]benzoxazepin-9-yl]-α,α-dimethyl-1H-pyrazole-1-acetamide (D446475), a newly discovered A β-Sparing phosphoinositide 3-kinase inhibitor with high unbound exposure and robust in vivo antitumor activity.