BIM 23042

Ki: 49 ±14 nM for neuromedin B-induced endpoint in huNMBR cells

Neuromedin B, a mammalian peptide of the bombesinlike peptide family sharing amino acid homology with its amphibian counterpart ranatensin, elicits a diverse array of biological responses in central and peripheral tissues. BIM 23042 [D-Nal-Cys-Tyr- D-Trp-Lys-Val-Cys-Nal-NH2] is a selective neuromedin B antagonist.

In vitro: BIM 23042 has a l00-fold greater affinity for BB1 receptors than BB2 receptors. The submaximal mobilisation observed with neuromedin B (1 nM) was abolished by BIM 23042 but restored with a subsequently higher concentration of neuromedin B (1 μM). BIM 23042 competitively inhibited neuromedin B-induced endpoint in huNMBR cells with a Ki of 49 ±14 nM [1].

In vivo: In cat upper GI tract, SSocta, at concentrations of 10 mM, did not influence the smooth muscle tone but shifted NMB concentration response to the right yielding (Ki=1.7±0.8 mM). Ssocta inhibited both NMB- and GRP-induced contractions on the esophagus. the NMB-receptor antagonist SSocta had no effect on circular fundic muscle indicating the absence of this receptor subtype on fundus. [2].

Clinical trial: Up to now, BIM 23042 is still in the preclinical development stage.

References:
[1] Ryan RR, Taylor JE, Daniel JL, Cowan A.  Pharmacological profiles of two bombesin analogues in cells transfected with human neuromedin B receptors. Eur J Pharmacol. 1996 Jun 13;306(1-3):307-14.
[2] Milusheva EA, Kortezova NI, Mizhorkova ZN, Papasova M, Coy DH, Bálint A, Vizi ES, Varga G.  Role of different bombesin receptor subtypes mediating contractile activity in cat upper gastrointestinal tract. Peptides. 1998;19(3):549-56.

Pharmacological profiles of two bombesin analogues in cells transfected with human neuromedin B receptors.[Pubmed:8813645]

Eur J Pharmacol. 1996 Jun 13;306(1-3):307-14.

We examined the effect of two des-Met-bombesin analogues, [(CH3)2CHCO-His-Trp-Ala-Val-D-Ala-His-Leu-NHCH3] (ICI 216140) and [D-Phe6,des-Met14]bombesin(6-14) ethylamide (DPDM-bombesin ethylamide), on neuromedin B-induced Ca2+ and [3H]arachidonate release in BALB 3T3 cells transfected with human neuromedin B receptors. ICI 216140 and DPDM-bombesin ethylamide both stimulated Ca2+ mobilisation in a concentration-dependent manner but were less potent and efficacious than neuromedin B. BIM 23042 [D-Nal-Cys-Tyr-D-Trp-Lys-Val-Cys-Nal-NH2], a selective neuromedin B antagonist and [D-Arg1,D-Phe5,D-Trp7,9,Leu11]substance P, a broad-spectrum peptide receptor antagonist inhibited neuromedin B-, ICI 216140 and DPDM-bombesin ethylamide-induced Ca2+ release. Pretreatment of cells with either des-Met-bombesin analogue attenuated neuromedin B-induced Ca2+ elevations, suggesting similar agonist-sensitive Ca2+ pools. The pharmacological profiles revealed from the [3H]arachidonate assay were similar, although ICI 216140 was less potent and efficacious than DPDM-bombesin ethylamide. The data suggest that ICI 216140 and DPDM-bombesin ethylamide behave as agonists at the neuromedin B receptor, perhaps as a consequence of neuromedin B receptor overexpression.

Role of different bombesin receptor subtypes mediating contractile activity in cat upper gastrointestinal tract.[Pubmed:9533644]

Peptides. 1998;19(3):549-56.

Mammalian bombesin-like peptides, gastrin-releasing peptide (GRP) and neuromedin B (NMB) are known to increase the motility of different segments in the gut. The present study was carried out to identify the bombesin receptor subtypes mediating the contractions induced by exogenous bombesin-like peptides in muscle strips isolated from cat esophagus, fundus, and duodenum. Both GRP-10 and NMB evoked concentration-dependent contractions in circular strips of esophagus and fundus and in longitudinal strips of the duodenum. These contractions were tetrodotoxin- and atropine-resistant. The potency of NMB in esophageal strips was 33 times higher than that of GRP-10. The NMB-preferring receptor antagonists D-Nal-Cys-Tyr-D-Trp-Lys-Val-Cys-Nal-NH2 (SSocta) and D-Nal-cyclo[Cys-Tyr-D-Trp-Orn-Val-Cys]-Nal-NH2 (BIM-23127) shifted the NMB and GRP concentration-response curves to the right, while the GRP-preferring receptor antagonist [D-Phe6]Bombesin(6-13)-methyl-ester (BME) did not affect the response to the peptides. Isolated muscle strips from the cat fundus and duodenum showed a higher sensitivity to GRP-10 than to NMB. In both segments, BME shifted the GRP-10 and NMB concentration-response curves to the right, while SSocta had no effect. The antagonism of BME was competitive on duodenal but not competitive on fundic muscle. We conclude that the direct myogenic action of GRP-10 and NMB in the esophagus is mediated mainly via NMB-preferring receptors, while GRP-preferring receptors are responsible for the contractile responses to bombesin-like peptides in feline fundus and duodenum. Our data suggest that the GRP receptor population located on fundic muscle might be nonhomogeneous.

Discovery of a novel class of neuromedin B receptor antagonists, substituted somatostatin analogues.[Pubmed:7901752]

Mol Pharmacol. 1993 Oct;44(4):841-50.

Bombesin-related peptides have widespread activities in the central nervous system and peripheral tissues. Recent studies show two subtypes of receptors; a gastrin-releasing peptide (GRP) receptor subtype and a neuromedin B (NMB) receptor subtype exist. In contrast to the GRP receptor, no antagonists exist for the NMB receptor. In the present study we report that certain somatostatin (SS) octapeptide analogues function as selective NMB receptor antagonists. The most potent analogue, D-Nal-Cys-Tyr-D-Trp-Lys-Val-Cys-Nal-NH2, inhibited binding of 125I-[D-Tyr degree]NMB to NMB receptor-transfected 3T3 cells and C6 cells. This analogue had 100-fold lower affinity for GRP receptors. Structure-function studies were performed by synthesizing 18 structurally related SS octapeptide analogues; each of these analogues, but not native SS-14 or SS-28, also inhibited binding to NMB receptors. The stereochemistry at positions 1, 2, 7, and 8, the hydrophobicity and ring size of the substitution in positions 1, 3, and 4, and the basicity of the group in position 5 were all important in determining NMB receptor affinity. No SS octapeptide analogue increased [3H]inositol phosphates in NMB receptor-transfected cells; however, each analogue inhibited NMB-stimulated increases. The most potent analogue, D-Nal-Cys-Tyr-D-Trp-Lys-Val-Cys-Nal-NH2, caused a parallel rightward shift of the NMB dose-response curve, the Schild plot slope was not significantly different from unity, and the affinity was 230 nM. SS octapeptide analogues also interacted with SS receptors and mu-opioid receptors; however, there was no correlation between the affinities of the analogues for these receptors and their affinities for NMB receptors, demonstrating that these activities can be separated. The results demonstrate for the first time a class of antagonists with > 100-fold selectivity for NMB versus GRP receptors. Because the structural requirements for determining NMB, SS, and mu-opioid receptor activity differ, it is likely that highly selective, specific, high affinity NMB receptor antagonists can now be developed that will be useful in defining the role of NMB in various physiological processes.