Potent and selective σ1 receptor antagonist (Ki = 0.86 nM) that displays > 55-fold selectivity over σ2 receptors and > 6000-fold selectivity over D1, D2, 5-HT1A, 5-HT2 and PCP receptors. Exhibits reversible binding (Kd = 1.2 nM) and displays antipsychotic activity in vivo. Orally active.