Pharmacological Properties of ABT-239 [4-(2-{2-[(2 R)-2-Methylpyrrolidinyl]ethyl}-benzofuran-5-yl)benzonitrile]: I. Potent and Selective Histamine H3 Receptor Antagonist with Drug-Like Properties

• Published in: The Journal of pharmacology and experimental therapeutics 2005-04, Vol.313 (1), p.165-175
• Main Authors: Esbenshade, Timothy A., Fox, Gerard B., Krueger, Kathleen M., Miller, Thomas R., Kang, Chae Hee, Denny, Lynne I., Witte, David G., Yao, Betty B., Pan, Liping, Wetter, Jill, Marsh, Kennan, Bennani, Youssef L., Cowart, Marlon D., Sullivan, James P., Hancock, Arthur A.
• Format: Article
• Language: English
• Subjects: Adenylyl Cyclases - metabolism; Animals; Benzofurans - pharmacokinetics; Benzofurans - pharmacology; Calcium - metabolism; Cell Membrane - drug effects; Cell Membrane - metabolism; Cerebral Cortex - drug effects; Cerebral Cortex - metabolism; Cloning, Molecular; Guanosine 5'-O-(3-Thiotriphosphate) - metabolism; Guinea Pigs; Histamine Antagonists - pharmacokinetics; Histamine Antagonists - pharmacology; Histamine Release - drug effects; Ileum - drug effects; In Vitro Techniques; Male; Muscle Contraction - drug effects; Muscle, Smooth - drug effects; Neurotransmitter Agents - metabolism; Pyrrolidines - pharmacokinetics; Pyrrolidines - pharmacology; Radioligand Assay; Rats; Rats, Sprague-Dawley; Receptors, Histamine H3 - drug effects
• ISSN: 0022-3565; 1521-0103
• DOI: 10.1124/jpet.104.078303

Histamine H3 receptor antagonists are being developed to treat a variety of neurological and cognitive disorders that may be ameliorated by enhancement of central neurotransmitter release. Here, we present the in vitro pharmacological and in vivo pharmacokinetic profiles for the nonimidazole, benzofuran ligand ABT-239 [4-(2-{2-[(2 R)-2-methylpyrrolidinyl]ethyl}-benzofuran-5-yl)benzonitrile] and compare it with several previously described imidazole and nonimidazole H3 receptor antagonists. ABT-239 binds to recombinant human and rat H3 receptors with high affinity, with p Ki values of 9.4 and 8.9, respectively, and is over 1000-fold selective versus human H1, H2, and H4 histamine receptors. ABT-239 is a potent H3 receptor antagonist at recombinant human and rat receptors, reversing agonist-induced changes in cAMP formation (p Kb = 7.9 and 7.6, respectively), guanosine 5′-O-(3-[35S]thio) triphosphate ([35S]GTPγS) binding (p Kb = 9.0 and 8.3, respectively), and calcium mobilization (human p Kb = 7.9). ABT-239 also competitively reversed histamine-mediated inhibition of [3H]histamine release from rat brain cortical synaptosomes (p Kb = 7.7) and agonist-induced inhibition of contractile responses in electric field stimulated guinea pig ileal segments (p A2 = 8.7). Additionally, ABT-239 is a potent inverse agonist, inhibiting constitutive [35S]GTPγS binding at both rat and human H3 receptors with respective pEC50 values of 8.9 and 8.2. ABT-239 demonstrates good pharmacokinetic characteristics in rat, dog, and monkey with t1/2 values ranging from 4 to 29 h, corresponding with clearance values and metabolic turnover in liver microsomes from these species, and good oral bioavailability ranging from 52 to 89%. Thus, ABT-239 is a selective, nonimidazole H3 receptor antagonist/inverse agonist with similar high potency in both human and rat and favorable drug-like properties.