RT Journal Article
SR Electronic
T1 Multifaceted Approach to Determine the Antagonist Molecular Mechanism and Interaction of Ibodutant ([1-(2-Phenyl-1<em>R</em>-{[1-(tetrahydropyran-4-ylmethyl)-piperidin-4-ylmethyl]-carbamoyl}-ethylcarbamoyl)-cyclopentyl]-amide) at the Human Tachykinin NK<sub>2</sub> Receptor
JF Journal of Pharmacology and Experimental Therapeutics
JO J Pharmacol Exp Ther
FD American Society for Pharmacology and Experimental Therapeutics
SP 486
OP 495
DO 10.1124/jpet.108.150201
VO 329
IS 2
A1 Stefania Meini
A1 Francesca Bellucci
A1 Claudio Catalani
A1 Paola Cucchi
A1 Alessandro Giolitti
A1 Paolo Santicioli
A1 Sandro Giuliani
YR 2009
UL http://jpet.aspetjournals.org/content/329/2/486.abstract
AB Ibodutant (MEN15596, [1-(2-phenyl-1R-{[1-(tetrahydropyran-4-ylmethyl)-piperidin-4-ylmethyl]-carbamoyl}-ethylcarbamoyl)-cyclopentyl]-amide) is a tachykinin NK2 receptor (NK2R) antagonist currently under phase II clinical trials for irritable bowel syndrome. This study focuses on the ibodutant pharmacodynamic profile at the human NK2R and compares it with two other antagonists, nepadutant (MEN11420, (cyclo-{[Asn(β-d-GlcNAc)-Asp-Trp-Phe-Dpr-Leu]cyclo(2β-5β)}) and saredutant [SR48968, (S)-N-methyl-N[4-(4-acetylamino-4-phenylpiperidino)-2-(3,4-dichlorophenyl)butyl]benzamide]. In functional experiments (phosphatidylinositol accumulation) in Chinese hamster ovary cells expressing the human NK2R, ibodutant potency measured toward concentration-response curves to neurokinin AaspKB was 10.6, and its antagonism mechanism was surmountable and competitive. In the same assay, antagonism equilibration and reversibility experiments of receptor blockade indicated that ibodutant quickly attains equilibrium and that reverts from receptor compartment in a slower manner. Kinetic properties of ibodutant were assessed through competitive binding kinetics experiments performed at [3H]nepadutant and [3H]saredutant binding sites. Determined Kon and Koff values indicated a fast association and slow dissociation rate of ibodutant at the different antagonist binding sites. Last, by radioligand binding experiments at some mutated human tachykinin NK2Rs, the amino acidic determinants crucial for the high affinity of ibodutant were identified at the transmembrane (TM) level: Cys167 in TM4; Ile202 and Tyr206 in TM5; Phe270, Tyr266, and Trp263 in TM6; and Tyr289 in TM7. These results indicated an extended antagonist binding pocket in the TM portion of the receptor, which is conceived crucial for TM3 and 6 arrangement and leads to G protein-coupled receptor activation. By combining this information and molecular modeling, the docking mode of ibodutant-human NK2R complex is proposed. The American Society for Pharmacology and Experimental Therapeutics