Hypidone (developmental code name YL-0919) is an investigational serotonergic antidepressant which is under development for the treatment of major depressive disorder. It acts as a serotonin reuptake inhibitor, 5-HT<sub>1A</sub> receptor partial agonist, and 5-HT<sub>6</sub> receptor full agonist. It is used as the hydrochloride salt. As of January 2021, hypidone is in phase 2 clinical trials for major depressive disorder.