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ACS Med Chem Lett. 2014 Mar 28;5(6):700-5. doi: 10.1021/ml5000993. eCollection 2014.

Discovery of Novel Imidazo[4,5-b]pyridines as Potent and Selective Inhibitors of Phosphodiesterase 10A (PDE10A).

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  • 1Department of Medicinal Chemistry, Department of Molecular Structure, Department of Pharmacokinetics and Drug Metabolism, and Department of Neuroscience, Amgen, Inc. , One Amgen Center Drive, Thousand Oaks, California 93012-1799, United States.
  • 2Department of Molecular Structure and Characterization, Department of Neuroscience, and Department of Pharmacokinetics and Drug Metabolism, Amgen, Inc. , 1120 Veterans Boulevard, South San Francisco, California 94080, United States.


We report the discovery of novel imidazo[4,5-b]pyridines as potent and selective inhibitors of PDE10A. The investigation began with our recently disclosed ketobenzimidazole 1, which exhibited single digit nanomolar PDE10A activity but poor oral bioavailability. To improve oral bioavailability, we turned to novel scaffold imidazo[4,5-b]pyridine 2, which not only retained nanomolar PDE10A activity but was also devoid of the morpholine metabolic liability. Structure-activity relationship studies were conducted systematically to examine how various regions of the molecule impacted potency. X-ray cocrystal structures of compounds 7 and 24 in human PDE10A helped to elucidate the key bonding interactions. Five of the most potent and structurally diverse imidazo[4,5-b]pyridines (4, 7, 12b, 24a, and 24b) with PDE10A IC50 values ranging from 0.8 to 6.7 nM were advanced into receptor occupancy studies. Four of them (4, 12b, 24a, and 24b) achieved 55-74% RO at 10 mg/kg po.


Phosphodiesterase 10A; bioavailability; receptor occupancy; schizophrenia

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