Lorcaserin is a selective agonist of the 5-HT2C receptor. In extensive in vitro evaluations,
lorcaserin exerted no activity at a panel of other receptors, transporters or ion channels when
tested at concentrations of 1 or 10 µM. These in vitro concentrations are well above the 230
nM (~45 ng/mL) steady state plasma concentrations observed at the recommended clinical
dose of 10 mg BID. Lorcaserin activates the 5-HT2A and 5-HT2B receptors in vitro with
potencies approximately 1/15th and 1/90th the potency at the 5-HT2C receptor. Its major
pharmacological effect is therefore predicted to be decreased food intake, with consequent
weight loss. The EC50 of lorcaserin at the 5-HT2C receptor in in vitro functional assays is ~9
nM.