D-Amino Acid Oxidase Inhibitor is a cell-permeable thienopyrrole compound that potently inhibits cellular activity of transfected D-amino acid oxidase (DAO/DAAO/DAMOX/OXDA) in CHO cells (IC50 against human and rat DAO = 145 and 114 nM, respectively). Exhibits no activity towards D-aspartate oxidase (DDO; IC50 >5 M), P450 enzymes CYP3A4/2D6/3C9 (IC50 >10 M), and a panel of over 150 other enzymes, receptors, and ion channels. Although treatment of Compound 8 (200 mg/kg, i.p.) is shown to effectively inhibit DAO activity in rat brain and kidney (by 96% and 80%, respectively), the resulting D-serine concentration increase in the periphery and central nervous system appears to be far from sufficient to produce adequate antipsychotic and cognitive enhancing effects.