4,5-Dihydropyridazin-3-one derivatives as histamine H3 receptor inverse agonists

H3R structure–activity relationships for a new class of 4,5-dihydropyridazin-3-one H3R antagonists/inverse agonists are disclosed. Modification of the 4,5-dihydropyridazinone moiety to block in vivo metabolism identified 4,4-dimethyl-6-{4-[3-((R)-2-methyl-pyrrolidin-1-yl)-propoxy]-phenyl}-4,5-dihydro-2H-pyridazin-3-one 22 as a lead candidate demonstrating potent in vivo functional H3R antagonism in the rat dipsogenia model and robust wake promoting activity in the rat EEG/EMG model.