A piperazine and quinolone derivative that is used primarily as an antipsychotic agent. It is a partial agonist of SEROTONIN RECEPTOR, 5-HT1A and DOPAMINE D2 RECEPTORS, where it also functions as a post-synaptic antagonist, and an antagonist of SEROTONIN RECEPTOR, 5-HT2A. It is used for the treatment of SCHIZOPHRENIA and BIPOLAR DISORDER, and as an adjunct therapy for the treatment of depression.