Characterisation of calcitonin gene-related peptide receptors in rat atrium and vas deferens: evidence for a [Cys(Et)(2, 7)]hCGRP-preferring receptor

The present study was performed in order to characterise calcitonin gene-related peptide (CGRP) receptor subtypes in rat left atrium and vas deferens by using [R-(R*, S*)]-N-[2-[[5-amino-1-[[4-(4-pyridinyl)-1-piperazinyl]carbonyl]pentyl ]amino]-1-[(3,5-dibromo-4-hydroxyphenyl)methyl]-2-oxoethyl]-4-(1, 4-dihydro-2-oxo-3(2H)-quinazolinyl)-,1-Piperidinecarboxamide (BIBN4096BS), a novel CGRP receptor antagonist. When CGRP was used as an agonist, BIBN4096BS exhibited an almost 10-fold higher affinity for CGRP receptors in rat left atrium compared to those in the vas deferens, indicating that CGRP acts through different CGRP receptor subtypes in these two tissues. In addition, BIBN4096BS was almost 10-fold more potent in antagonizing [Cys(Et)(2,7)]hCGRPalpha and human adrenomedullin-induced responses than CGRP-induced responses in rat vas deferens. This might indicate receptor heterogeneity in rat vas deferens. Accordingly, the present work provides first experimental evidence that the rat vas deferens contains two CGRP-like receptor subtypes. Namely, the CGRP(2) receptor and a "novel" receptor that possesses low efficacy for CGRP and that is selectively stimulated by [Cys(Et)(2,7)]hCGRP or adrenomedullin and which can be blocked with high affinity by BIBN4096BS.

Pharmacological profile of BIBN4096BS, the first selective small molecule CGRP antagonist

Calcitonin gene-related peptide (CGRP) is one of the most potent endogenous vasodilators known. This peptide is increased during migraine attacks and has been implicated in the pathogenesis of migraine headache. Here we report on the first small molecule selective CGRP antagonist: BIBN4096BS. In vitro, this compound is extremely potent at primate CGRP receptors exhibiting an affinity (Ki) for human CGRP receptors of 14.4 +/- 6.3 (n = 4) pM. In an in vivo model, BIBN4096BS in doses between 1 and 30 micrograms kg-1 (i.v.) inhibited the effects of CGRP, released by stimulation of the trigeminal ganglion, on facial blood flow in marmoset monkeys. It is concluded that BIBN4096BS is a potent and selective CGRP antagonist.

BIIE0246: a selective and high affinity neuropeptide Y Y(2) receptor antagonist

The in vitro biological characterisation of the first potent and selective non-peptide neuropeptide Y Y(2) receptor antagonist, (S)-N(2)-[[1-[2-[4-[(R,S)-5,11-dihydro-6(6h)-oxodibenz[b, e]azepin-11-yl]-1-piperazinyl]-2-oxoethyl] cylopentyl] acetyl]-N-[2-[1,2-dihydro-3,5(4H)-dioxo-1,2-diphenyl-3H-1,2, 4-triazol-4-yl]ethyl]-argininamid (BIIE0246) is reported. BIIE0246 displaced [125I]neuropeptide Y with high affinity (IC(50)=3.3 nM) from the human neuropeptide Y Y(2) receptor and proved to be highly selective. BIIE0246 displayed antagonistic properties and thus represents the first selective non-peptide neuropeptide Y Y(2) receptor antagonist.

Subtype selectivity of the novel nonpeptide neuropeptide Y Y1 receptor antagonist BIBO 3304 and its effect on feeding in rodents

1. The novel Y1-selective argininamide derivative BIBO 3304 ((R)-N-[[4-(aminocarbonylaminomethyl)-phenyl]methyl]-N2-(diphen ylacetyl)-argininamide trifluoroacetate) has been synthesized and was examined for its subtype selectivity, its in vitro antagonistic properties and its food intake inhibitory properties. 2. BIBO 3304 displayed subnanomolar affinity for both the human and the rat Y1 receptor (IC50 values 0.38+/-0.06 nM and 0.72+/-0.42 nM, respectively). The inactive enantiomer of BIBO 3304 (BIBO 3457) had low affinity for both the human and rat Y1 receptor subtype (IC50> 1000 nM). BIBO 3304 showed low affinity for the human Y2 receptor, human and rat Y4 receptor as well as for the human and rat Y5 receptor (IC50 values > 1000 nM). 3. 30 microg BIBO 3304 administered into the paraventricular nucleus inhibited the feeding response induced by 1 microg NPY as well as the hyperphagia induced by a 24 h fast implying a role for Y1 receptors in NPY mediated feeding. The inactive enantiomer had no effect. 4. BIBO 3304 inhibits neither the galanin nor the noradrenaline induced orexigenic response. but it blocked feeding behaviour elicited by both [Leu31, Pro24]NPY and NPY (3 36) suggesting an interplay between different NPY receptor subtypes in feeding behavior. 5. The present study reveals that BIBO 3304 is a subtype selective nonpeptide antagonist with subnanomolar affinity for the Y1 receptor subtype that significantly inhibits food intake induced by application of NPY or by fasting.

BIBP 3226, the first selective neuropeptide Y1 receptor antagonist: a review of its pharmacological properties

Based on the assumption that the pharmacophoric groups interacting with the Y1 receptor are located in the C-terminal part of neuropeptide Y, low molecular weight compounds with high affinity and selectivity for the Y1 receptor were designed and synthesized. The prototype BIBP 3226 possesses affinity for the Y1 receptor in the nanomolar range. In addition, this compound is selective displaying rather low affinity for Y2, Y3, Y4 and a set of 60 other receptors. Both biochemical and pharmacological studies showed that BIBP 3226 behaves as a competitive antagonist. Using BIBP 3226 it was possible to investigate the role of NPY and/or Y1 receptors in blood pressure regulation. The interesting observation was that antagonism to Y1 receptors had no major influence on the basal blood pressure but attenuated stress induced hypertension. This strongly supports the hypothesis that NPY is mainly released during stress involving intense sympathetic nervous system activation. Moreover, BIBP 3226 can be used to characterize NPY receptor subtypes. For instance, we were able to show that presynaptic NPY receptors mediating catecholamine release do not solely belong to the Y2 subtype, but that presynaptic Y1 receptors also exist. In conclusion, BIBP 3226 has been shown to be an important tool for the elucidation of the physiological role of Y1 receptors in the cardiovascular system.

Neuropeptide Y and the nonpeptide antagonist BIBP 3226 share an overlapping binding site at the human Y1 receptor

Neuropeptide Y (NPY) is a 36-amino acid peptide that exhibits actions on the cardiovascular system and the central nervous system. NPY can regulate blood pressure, psychomotor function, anxiety, food intake, and endocrine secretions. BIBP 3226, the first potent and selective nonpeptide antagonist at the NPY Y1 receptor, was designed by mimicking the carboxyl-terminal structure of NPY. We investigated the interaction of NPY and BIBP 3226 with the human Y1 receptor at the molecular level. Alanine mutants at positions Y100, D104, W288, and H298 of the human Y1 receptor showed no or significantly reduced binding for NPY but were not affected in their ability to bind BIBP 3226. Receptors with alanine mutations at positions W163, F173, Q219, N283, F286, and D287 showed reduced binding for both NPY and BIBP 3226. Mutations at other positions were tested (H105, S170, L174, V178, D200, D205, S206, H207, S210, T212, T280, T284, N289, H290, and Q291) and did not affect the binding of NPY or BIBP 3226. The human Y1 receptor mutant Y211A showed no affinity for BIBP 3226 but retained wild-type affinity for NPY. Based on these experimental results, a detailed model for the interaction of BIBP 3226 with the human Y1 receptor was developed using a Y1 receptor model and a three-dimensional model of BIBP 3226. The experimental results, supported by modeling studies, clearly suggest that the native ligand (NPY) and the antagonist (BIBP 3226) share an overlapping binding site.

Subtype selectivity and antagonistic profile of the nonpeptide Y1 receptor antagonist BIBP 3226

In the present study, the subtype specificity and species selectivity of the nonpeptide BIBP 3226, as well as its in vitro antagonism of neuropeptide Y (NPY)-mediated second messengers have been investigated. Radiolabeled NPY is potently displaced by BIBP 3226 [(R)-N2-(diphenylacetyl)-N-[(4-hydroxyphenylmethyl]-D- arginine amide] on human Y1 receptor expressing Chinese hamster ovary-K1 cells (Ki = 0.47 +/- 0.07 nM). SK-N-MC human neuroblastoma cells (Ki = 5.1 +/- 0.5 nM) and the rat parietal cortex membranes (Ki = 6.8 +/- 0.7 nM). The interaction of BIBP 3226 with the Y1 receptor is stereoselective, because the (S)-enantiomer of the (R)-configured BIBP 3226 displays almost no affinity (Ki > 10,000 nM). In contrast, concentrations up to 10 microM BIBP 3226 do not displace [125I]NPY from the human Y2 receptor (neuroblastoma cell line SMS-KAN), the rabbit Y2 receptor (kidney) and the rat Y2 receptor (hippocampus). Functional antagonism could be shown for the human Y1 receptor: 0.1 microM BIBP 3226 antagonizes the NPY induced Ca++ mobilization (pKb = 7.5 +/- 0.17) as well as the NPY-mediated inhibition of cyclic AMP synthesis (pKb = 8.2 +/- 0.24) in SK-N-MC cells. In contrast, none of the formerly described putative antagonists PYX-2, [D-Trp32]NPY and benextramine could be characterized as high affinity Y1 receptor antagonists. The 18 amino acid NPY analog EXBP 68 Ile-Glu-Pro-Orn-Tyr-Arg-Leu-Arg-Tyr-NH2, cyclic (2,4'), (2',4')-diamide] displayed Y1-selective affinity with in vitro antagonistic properties (Ki = 0.33 +/- 0.04 nM and pKb = 8.4 +/- 0.07) in SK-N-MC cells. Therefore, BIBP 3226 is the first potent and subtype-selective nonpeptide Y1 receptor antagonist.

Pharmacological characterization of the selective nonpeptide neuropeptide Y Y1 receptor antagonist BIBP 3226

The present study was undertaken to investigate the in vitro and in vivo pharmacological profile of the novel, nonpeptide neuropeptide Y (NPY) Y1-selective antagonist, BIBP 3226 [(R)-N2-(diphenylacetyl)-N-[(4-hydroxyphenyl)methyl]-D-arginine-am ide], and a recently described peptidic structure [Ile-Glu-Pro-Orn-Tyr-Arg-Leu-Arg-Tyr-NH2, cyclic (2,4'), (2',4)-diamide]. BIBP 3226 antagonized the NPY Y1 receptor-mediated decrease in the twitch response in the rabbit vas deferens preparation with a pKb value of 6.98 +/- 0.06 (n = 16). It showed no affinity (EC50 > 1 microM) for NPY Y2 receptors in the rat vas deferens. NPY-induced increases in perfusion pressure in the isolated perfused rat kidney and rabbit ear preparations were antagonized with IC50 values of 26.8 +/- 4.5 (n = 4) and 214 +/- 30 nM (n = 4), respectively. The NPY-mediated potentiation of the noradrenaline elicited increase in perfusion pressure in the rat mesenteric bed was antagonized with an IC50 value of 976 (542-1760) nM. The NPY-induced increase in blood pressure in the pithed rat was inhibited by BIBP 3226 dose-dependently (ED50 = 0.11 +/- 0.03 mg/kg i.v.), whereas no effect of BIBP 3226 (1 mg/kg i.v.) was observed for the noradrenaline-, angiotensin-, endothelin- or vasopressin-induced pressor response. The data presented demonstrate that BIBP 3226 is a competitive and NPY Y1-selective antagonist. The peptidic compound proved to possess high potency for NPY Y1 receptors, but showed both agonistic as well as antagonistic properties.(ABSTRACT TRUNCATED AT 250 WORDS)

Labeling of neuropeptide Y receptors in SK-N-MC cells using the novel, nonpeptide Y1 receptor-selective antagonist [3H]BIBP3226

The binding of tritium-labelled BIBP3226, N2-(diphenylacetyl)-N-[(4-hydroxy-phenyl)methyl]-D-arginine amide, to human neuroblastoma SK-N-MC cells was investigated. [3H]BIBP3226 reversibly binds to neuropeptide Y receptors of the Y1 subtype expressed in SK-N-MC cells with a KD of 2.1 +/- 0.3 nM (mean +/- S.E.M., n = 3) and a Bmax of 58,400 +/- 1100 sites/cell. Non-specific binding did not exceed 30% of the total radioactivity bound at KD. In competition experiments [3H]BIBP3226 is concentration-dependently displaced by neuropeptide Y and its peptide analogues with an affinity pattern neuropeptide Y = [Leu31, Pro34]neuropeptide Y >> neuropeptide Y-(18-36). This rank order of potencies is consistent with the interaction of [3H]BIBP3226 with neuropeptide Y receptors of the Y1 subtype. Therefore, [3H]BIBP3226 can be used as selective ligand to study neuropeptide Y Y1 receptors.

The first highly potent and selective non-peptide neuropeptide Y Y1 receptor antagonist: BIBP3226

The design and subsequent in vitro and in vivo biological characterisation of the first potent and selective non-peptide neuropeptide Y Y1 receptor antagonist, BIBP3226 ((R)-N2-(diphenylacetyl)-N-[(4-hydroxyphenyl)methyl]-argininami de) is reported. BIBP3226 displaced 125I-labelled neuropeptide Y with high affinity (Ki = 7 nM) from the human neuropeptide Y Y1 receptor and proved to be highly selective. BIBP3226 displayed potent antagonistic properties both in in vitro and in vivo models and thus represents the first selective non-peptide neuropeptide Y Y1 receptor antagonist.

Characterization of BIBN 99: a lipophilic and selective muscarinic M2 receptor antagonist

The present study was designed to characterize the receptor selectivity profile of the novel muscarinic M2 receptor antagonist BIBN 99 (5,11-dihydro-8-chloro-11-[[4-[3-[(2,2-dimethyl-1- oxopentyl)ethylamino]propyl]-1-piperidinyl]acetyl]-6H- pyrido[2,3-b][1,4]benzodiazepin-6-one). In radioligand binding studies BIBN 99 showed high affinity for m2/M2 sites (pKi = 7.52/7.57), intermediate affinity for m4 sites (pKi = 6.76) and low affinity for m1/M1 (pKi = 5.97/6.17), m3/M3 (pKi = 6.11/6.04) and m5 sites (pKi = 5.84). Functional studies in vitro showed BIBN 99 to be a competitive antagonist and to have an 11- to 25-fold higher affinity for M2 receptors than for putative M1 receptors in the rabbit vas deferens or M3 receptors in guinea-pig trachea. In vivo studies revealed that BIBN 99 is able to cross the blood-brain barrier, and although showing an approximately 3-fold higher affinity for M2 binding sites BIBN 99 appeared to be 7- to 18-fold less potent than AF-DX 116 in inhibiting muscarinic agonist or vagally induced bradycardia in rats and guinea-pigs. The results show that BIBN 99 is the first lipophilic muscarinic M2 receptor antagonist to have remarkable M2 versus M1 selectivity (30-fold). In addition, BIBN 99 possesses central nervous system activity and only minor peripheral cardiac effects.

Specific bradycardic agents. 1. Chemistry, pharmacology, and structure-activity relationships of substituted benzazepinones, a-new class of compounds exerting antiischemic properties

Structural modification of the calcium-antagonist verapamil (1) by replacement of the lipophilic alpha-isopropylacetonitrile moiety by various heterocyclic ring systems has led to a new class of cardiovascular compounds which are characterized by a specific bradycardic activity. These agents reduce heart rate without binding to classical calcium channels or beta-adrenoceptors, interacting instead specifically with structures at the sino atrial node. Therefore they have also been termed sinus node inhibitors. The prototype falipamil (2) has been submitted to further optimization mainly by manipulation of the phthalmidine moiety. This has resulted in a second generation of specific bradycardic agents with increased potency and selectively and prolonged duration of action represented by the benzazepinone-derivative UL-FS 49 (4). Structure-activity relationships within this novel class of compounds have revealed a marked dependence of activity on the substitution pattern of the aromatic rings, the nature of the central nitrogen atom, and the length of the connecting alkyl chains. The crucial role of the benzazepinone ring for bradycardic activity can be best explained by its special impact on the overall molecular conformation.

[Anti-ulcer agent pirenzepine (LS 519)--a tricyclic compound with particular physico-chemical properties (author's transl)]

Compound 5,11-dihydro-11-[(4-methyl-1-piperazinyl)acetyl]-6H-pyrido[2,3-b][1,4]benzodiazepin-6-one dihydrochloride (pirenzepine, L-S 519) represents a new type of drug in ulcer therapy. It has been selected for broad clinical investigations because of its outstanding pharmacological profile. Pirenzepine is devoid of any central activity despite certain structural similarities in relation to psychotropic tricyclic compounds. The extraordinary pharmacokinetic and pharmacodynamic behaviour of this compound can be easily derived from its inherent physicochemical properties: The inability to pass the blood-brain barrier as well as its inability to activate the unspecific and specific psychotropic receptors is due to thermodynamic factors.