MEN16132, a novel potent and selective nonpeptide antagonist for the human bradykinin B2 receptor.: In vitro pharmacology and molecular characterization

The pharmacological characterization of the novel nonpeptide antagonist for the 132 receptor, namely MEN16132 (4-('S)-Amino-5-(4- 4-[2,4-dichloro-3-(2.4-dimethyl-8-quinolyloxymethyl)phenylsulfonamidol-tetrahydro-2H-4-pyranylearbonyl piperazino)-5-oxopentyl](trimethyl)ammonium chloride hydrochloride) is presented. The affinity of MEN 16132 for the bradykinin B, receptor has been investigated by means of competition studies at [3 H]bradykinin binding to membranes prepared from Chinese Hamster Ovary (CHO) cells expressing the human bradykinin B-2 receptor (pK(i) 10.5), human lung fibroblasts (pK(i) 10.5).. guinea pig airways (pK(i) 10.0), guinea pig ileum longitudinal smooth muscle (pK(i) 10.2), or guinea pig cultured colonic myocytes (pK(i) 10.3). In all assays MEN16132 was as potent as the peptide antagonist Icatibant, and from 3- to 100-fold more potent than the reference nonpeptide antagonists FR173657 or LF16-0687. The selectivity for the bradykinin B, receptor was checked at the human bradykinin 131 receptor (pK(i) < 5), and at a panel of 26 different receptors and channels. The antagonist potency was measured in functional assays, i.e., in blocking the bradykinin induced inositolphosphates (IP) accumulation at the human (CHO: pK(B) 10.3) and guinea pig (colonic myocytes: pKB 10.3) B, receptor, or in antagonizing the bradykinin induced contractile responses in human (detrusor smooth muscle: pK(B) 9.9) and guinea pig (ileum longitudinal smooth muscle: pK(B) 10.1) tissues. In both functional assay types MEN16132 exerted a different antagonist pattern, i.e., surmountable at the human and insurmountable at the guinea pig bradykinin B, receptors. Moreover, the receptor determinants important for the high affinity interaction of MEN 16132 with the human bradykinin B, receptor were investigated by means of radioligand binding studies performed at 24 point-mutated receptors. The results obtained revealed that residues in transmembrane segment 2 (W86A), 3 (I110A), 6 (W256A), and 7 (Y295A, Y295F but not much Y295W), were crucial for the high affinity of MEN16132. In conclusion, MEN16132 is a new, potent, and selective nonpeptide bradykinin B, receptor antagonist. (c) 2005 Elsevier B.V. All rights reserved.