Structure-activity relationships of a series of substituted benzamides: Potent D-2/5-HT2 antagonists and 5-HT1a agonists as neuroleptic agents

A series of substituted (4-(4-(1,2-benzisothiazol-3-yl)-1-piperazinyl)butyl)benzamide derivatives was prepared and evaluated as potential atypical antipsychotic agents. The target compounds were readily prepared from their benzoyl chloride, benzoic acid, or isatoic anhydride precursors, and they were evaluated in vitro for their ability to bind to dopamine D-2, serotonin 5-HT2, and serotonin 5-HT1a, receptors. To assess the potential antipsychotic activity of these compounds, we investigated their ability to inhibit the apomorphine-induced climbing response in mice. Selected compounds were evaluated further to determine their side-effect potentials. Structure-activity relationships of both mono- and polysubstituted benzamides are discussed herein. While several analogues had potent in vitro and in vivo activities indicative of potential atypical antipsychotic activity, anthranilamide 77 (1192U90) demonstrated a superior pharmacological profile. As a result of this investigation, 1192U90 (2-amino-N-(4-(4-(1,2-benzisothiazol-3-yl)-1-piperazinyl)butyl) benzamide hydrochloride) was selected for further evaluation and is currently in phase I clinical trials as a potential atypical antipsychotic agent.