hypidone hypidone 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-ht1a receptor partial agonist, and 5-ht6 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. hypidoneclinical dataother namesyl-0919; yl0919identifiers iupac name 1-pyridin-2-one cas number1339339-18-2 1339058-04-6 (hcl)pubchem cid54673543chemspider68055492chemical and physical dataformulac18h22n2o2molar mass298.386 g·mol−13d model (jsmol)interactive image smiles c1cn(ccc1(cn2c=cc=cc2=o)o)cc3=cc=cc=c3 inchi inchi=1s/c18h22n2o2/c21-17-8-4-5-11-20(17)15-18(22)9-12-19(13-10-18)14-16-6-2-1-3-7-16/h1-8,11,22h,9-10,12-15h2key:bgmvorououvvrv-uhfffaoysa-n