In vitro activity: Lorcaserin exhibits higher affinity for human 5-HT2C than to 5-HT 5-HT2A (7.5-fold selective, Ki=112 nM) and 5-HT2B (11.6-fold selective, Ki=174 nM). Lorcaserin possesses agonist activity at all three human 5-HT2 receptors. Lorcaserin is 18-fold more potent at human 5-HT2C (EC50= 9 nM) than at human 5-HT2A (EC50= 168 nM), and it is 104-fold more potent at human 5-HT2C than human 5-HT2B (EC50= 943 nM). Lorcaserin shows full agonist activity at the human 5-HT2C and 5-HT2B receptors and partial agonist activity at the human 5-HT2A receptor (100%, 100% and 75% of the maximal response elicited by serotonin, respectively). Lorcaserin does not compete for binding of ligands to serotonin, dopamine, and norepinephrine transporters. Lorcaserin does not stimulate norepinephrine, dopamine, or serotonin release from rat synaptosomes at submicromolar concentrations. Lorcaserin weakly inhibits norepinephrine (EC50= 2500 nM), serotonin (EC50= 1400 nM), and dopamine (EC50= 12,000 nM) uptake.