Perospirone (SM-9018 free base) is an orally active antagonist of 5-HT_2A receptor (K_i=0.6 nM) and dopamine D₂ receptor (K_i=1.4 nM), and also a partial agonist of 5-HT_1A receptor (K_i=2.9 nM). Perospirone is an atypical antipsychotic drug and has the potential for schizophrenic disease^[1][2]. In Vitro: Perospirone (SM-9018 free base) possesses moderate affinities for α₁, 5-HT₁, and D₁ receptors (K_i=17, 18 and 41 nM, respectively) ^[1]. In Vivo: Perospirone (SM-9018 free base; 1.0-10.0 mg/kg/day; orally; for 14 consecutive days) significantly attenuates PCP-induced cognitive deficits in mice in a dose-dependent manner^[2].