Discovery of DS34942424: An orally potent analgesic without mu opioid receptor agonist activity

[Display omitted] We identified (5′S)-10′-fluoro-6′-methyl-5′,6′-dihydro-3′H-spiro[cyclopropane-1,4′-[2,6]diaza[2,5]methano[2,6]benzodiazonin]-7′(1′H)-one, 22b (DS34942424) with a unique and original bicyclic skeleton. 22b showed an orally potent analgesic in the acetic acid-induced writhing test and formalin test in ddY mice without sedation. Moreover, 22b did not exhibit mu opioid receptor agonist activity.