TY - JOUR T1 - Pharmacological Properties of (2<em>R</em>)-<em>N</em>-[1-(6-Aminopyridin-2-ylmethyl)piperidin-4-yl]-2-[(1<em>R</em>)-3,3-difluorocyclopentyl]-2- hydroxy-2-phenylacetamide: A Novel Muscarinic Antagonist with M<sub>2</sub>-Sparing Antagonistic Activity JF - Journal of Pharmacology and Experimental Therapeutics JO - J Pharmacol Exp Ther SP - 790 LP - 797 VL - 297 IS - 2 AU - Hiroyasu Hirose AU - Ikuo Aoki AU - Toshifumi Kimura AU - Toru Fujikawa AU - Tomoshige Numazawa AU - Kaori Sasaki AU - Akio Sato AU - Takuro Hasegawa AU - Masaru Nishikibe AU - Morihiro Mitsuya AU - Norikazu Ohtake AU - Toshiaki Mase AU - Kazuhito Noguchi Y1 - 2001/05/01 UR - http://jpet.aspetjournals.org/content/297/2/790.abstract N2 - We evaluated the pharmacological profiles of (2R)-N-[1-(6- aminopyridin-2-ylmethyl)piperidin-4-yl]-2-[(1R)-3,3-difluorocyclopentyl]-2-hydroxy-2-phenylacetamide(compound A), which is a novel muscarinic receptor antagonist with M2-sparing antagonistic activity. Compound A inhibited [3H]NMS binding to cloned human muscarinic m1, m2, m3, m4, and m5 receptors expressed in Chinese hamster ovary cells with K i values (nM) of 1.5, 540, 2.8, 15, and 7.7, respectively. In isolated rat tissues, compound A inhibited carbachol-induced responses with 540-fold selectivity for trachea (K B = 1.2 nM) over atria (K B = 650 nM). In in vivo rat assays, compound A inhibited acetylcholine-induced bronchoconstriction and bradycardia with intravenous ED50 values of 0.022 mg/kg and ≥10 mg/kg, respectively. Furthermore, in dogs, compound A (0.1–1 mg/kg p.o.) dose dependently shifted the methacholine concentration-respiratory resistance curves. In mice, compound A (10 mg/kg i.v.) did not inhibit oxotremorine-induced tremor. The brain/plasma ratio (K p) of compound A (3 mg/kg i.v.) was 0.13 in rats; this K p was less than that of scopolamine (1.7) and darifenacin (0.24). The inhibition of compound A (3 mg/kg i.v.) on ex vivo binding in rat cerebral cortex was almost similar to that of NMS. These findings demonstrate that compound A has high selectivity for M3receptors over M2 receptors, displays a potent, oral M3 antagonistic activity without inhibition of central muscarinic receptors because of low brain penetration. It is well known that central muscarinic antagonists may have diverse CNS effects, and M2 receptors regulate cardiac pacing and act as autoreceptors in the lung and bladder. Thus, compound A may have fewer cardiac or CNS side effects than nonselective compounds. The American Society for Pharmacology and Experimental Therapeutics ER -