Discovery of 4-benzoylpiperidine and 3-(piperidin-4-yl)benzo[d]isoxazole derivatives as potential and selective GlyT1 inhibitors

Regulation of glycine transporter 1 (GlyT1) activity is a currently investigated strategy in drug discovery for schizophrenia. This study developed a series of new 4-benzoylpiperidine derivatives as GlyT1 inhibitors by bioisosteric replacement and mimicking of the pyridine ring of RG1678. Among the 4-benzoylpiperidine derivatives, 23q showed an IC₅₀ of 30 nM. Preliminary optimization of the blood-brain barrier penetration led to the discovery of 3-(piperidin-4-yl)benzo[d]isoxazole derivatives. Both series showed good selectivity over GlyT2, D₁, D₂, D₃, 5-HT_1A and 5-HT_2A receptors. Moreover, behavioral testing showed 23q (40 mg kg^-1, intragastric) can inhibit the hyperlocomotion induced by acute treatment of phencyclidine, and improve the impaired negative and cognitive symptoms in chronic phencyclidine-induced C57BL/6J mice. An interesting finding showed that 3-(piperidin-4-yl)benzo[d]isoxazole was a privileged scaffold of atypical antipsychotic agents but exhibited high selectivity and potency as a GlyT1 inhibitor.