3,4-Dihydro-7-(3’carboxy)propoxy-2(1H)-(quinolinone-2,2,3,3,6,8-d6) is deuterium labeled 3,4-Dihydro-7-(3’carboxy)propoxy-2(1H)-quinolinone (D448725), which is a metabolite of Aripiprazole (A771000) and a selective dopamine D2-receptor antagonist with dopamine autoreceptor agonist activity.