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The pre-clinical characterization of novel aryloxypyridine amides that are histamine H(3) receptor antagonists is described. These compounds are high affinity histamine H(3) ligands that penetrate the CNS and occupy the histamine H(3) receptor in rat brain. Several compounds were extensively profiled pre-clinically leading to the identification of two compounds suitable for nomination as development candidates.

A series of small molecules consisting of a heterocyclic core flanked by two basic functionalities were synthesized and screened for in vitro affinity at the human histamine H 3 receptor (hH 3 R). Nine of the twenty-eight compounds tested were found to possess a hH 3 R K i of less than 5 nM and consisted of a diverse range of central hetero-aromatic linkers (pyridine, pyrazine, oxazole, isoxazole, thiazole, furan, thiophene, and pyrrole). One member of this series, (4-isopropyl-piperazin-1-yl)-(6-piperidin-1-ylmethyl-pyridin-3-yl)-methanone ( 37 ), was found to be a high affinity, selective antagonist that crosses the blood-brain barrier and occupies H 3 receptors after oral administration in the rat.

The synthesis and biological activity of a new series of 2-aryloxymethylmorpholine histamine H 3 antagonists is described. The new compounds are high affinity histamine H 3 ligands that penetrate the CNS and occupy the histamine H 3 receptor in rat brain.