To identify structurally novel corticotropin-releasing factor 1 (CRF1) receptor antagonists, a series of bicyclic core analogs pyrrolo [1, 2-b] pyridazines and pyrrolo [2, 1-f] triazin-4 (3H)- ones, which were designed based on a monocyclic core antagonist, was synthesized and evaluated. Among the compounds tested, 2-difluoromethoxy-4-methylpyridin-5-yl analog 27 was found to show efficacy in a dose-dependent manner in an elevated plus maze test in ...