The synthesis and biologicalevaluation of new potent opioid receptor-like 1 antagonists are presented. A structure–activity relationship (SAR) study of arylpyrazole lead compound 1 obtained from library screening identified compound 31, (1S,3R)-N-[1-(3-chloropyridin-2-yl)-5-(5-fluoro-6-methylpyridin-3-yl)-4-methyl-1H-pyrazol-3-yl]methyl}-3-fluorocyclopentanamine, which exhibits high intrinsic potency
Structure-activity relationship studies directed toward improving the metabolic stability of compound 1 resulted in the identification of 3-[5-(3,5-difluorophenyl)-3-([(1S,3R)-3-fluorocyclopentyl]amino}methyl)-4-methyl-1H-pyrazol-1-yl]propanenitrile 39 (MK-1925) as a selective, orally available and brain-penetrable opioid receptor-like 1 (ORL1) antagonist. The compound also showed in vivo efficacy after oral dosing. Therefore, compound 39 was selected to undergo further studies as a clinical candidate. (C) 2009 Elsevier Ltd. All rights reserved.