Lorcaserin acts as an agonist at the 5HT2C-receptor. Lead investigator of the Blossom study, Dr Lee Kaplan (Massachusetts General Hospital, Boston, USA) explained that serotonin is known to be important in inducing weight loss; previous drugs have raised endogenous serotonin levels. More has been discovered about various different serotonin receptors, and it is now thought that the 5HT2B receptor is responsible for the cardiac valvular effects of these serotonergic drugs, while the 5HT2C receptor is responsible for weight loss. So by stimulating the 5HT2C receptor alone, it should be possible to induce weight loss without the valvular side ef