Henri Doods

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 μg 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.

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.

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‐(diphenylacetyl)‐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 μg BIBO 3304 administered into the paraventricular nucleus inhibited the feeding response induced by 1 μg 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, Pro34]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.

BIIE0246: A selective and high affinity neuropeptide Y Y2 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.

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.

Blockade and reversal of spinal morphine tolerance by peptide and non‐peptide calcitonin gene‐related peptide receptor antagonists

This study examined the effects of the peptide CGRP receptor antagonist CGRP8‐37 and the newly‐developed non‐peptide CGRP receptor antagonist BIBN4096BS for their potential to both inhibit the development and reverse tolerance to the antinociceptive action of morphine. Repeated administration of intrathecal morphine (15 μg), once daily, produced a progressive decline of antinociceptive effect and an increase in the ED50 value in the tailflick and paw pressure tests. Co‐administration of CGRP8‐37 (4 μg) or BIBN4096BS (0.05, 0.1 μg) with morphine (15 μg) prevented the decline of antinociceptive effect and increase in ED50 value in the tailflick test. Intrathecal administration of the CGRP receptor antagonists did not alter the baseline responses in either tests. Acute CGRP8‐37 also did not potentiate the acute actions of spinal morphine. In animals rendered tolerant to intrathecal morphine, subsequent administration of CGRP8‐37 (4 μg) with morphine (15 μg) partially restored the antinociceptive effect and ED50 value of acute morphine, reflecting the reversal of tolerance. Animals tolerant to intrathecal morphine expressed increased CGRP and substance P‐like immunostaining in the dorsal horn of the spinal cord. The increase in CGRP, but not substance P‐like immunostaining, was blocked by a co‐treatment with CGRP8‐37 (4 μg). In animals already tolerant to morphine, the increase in CGRP but not substance P‐like immunostaining was partially reversed by CGRP8‐37 (4 μg). These data suggest that activation of spinal CGRP receptors contributes to both the development and expression of spinal opioid tolerance. CGRP receptor antagonists may represent a useful therapeutic approach for preventing as well as reversing opioid tolerance.

Effect of a selective neuropeptide Y Y2 receptor antagonist, BIIE0246 on neuropeptide Y release

We have examined the selective 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]cyclopentyl]acetyl ]-N-[2-[1 ,2-dihydro-3,5(4H)-dioxo-1,2-diphenyl-3-H-1,2, 4-triazol-4-yl]ethyl]-argininamid (BIIE0246) on neuropeptide release from rat hypothalamic slices in vitro. BIIE0246 prevented neuropeptide Y-(13-36)-induced reduction in basal and K(+)-stimulated neuropeptide Y release. Addition of BIIE0246 alone enhanced K(+)-stimulated neuropeptide release, without affecting basal release. These data are consistent with anatomical and functional studies suggesting a pre-synaptic role for neuropeptide Y Y(2) receptors in regulating rat hypothalamic neuropeptide Y release in the rat.

BIIE0246, a potent and highly selective non-peptide neuropeptide Y Y2 receptor antagonist

BIIE0246, a newly synthesized non‐peptide neuropeptide Y (NPY) Y2 receptor antagonist, was able to compete with high affinity (8 to 15 nM) for specific [125I]PYY3–36 binding sites in HEK293 cells transfected with the rat Y2 receptor cDNA, and in rat brain and human frontal cortex membrane homogenates. Interestingly, in rat brain homogenates while NPY, C2‐NPY and PYY3–36 inhibited all specific [125I]PYY3–36 labelling, BIIE0246 failed to compete for all specific binding suggesting that [125I]PYY3–36 recognized, in addition to the Y2 subtype, another population of specific NPY binding sites, most likely the Y5 receptor. Quantitative receptor autoradiographic data confirmed the presence of [125I]PYY3–36/BIIE0246‐sensitive (Y2) and‐insensitive (Y5) binding sites in the rat brain as well as in the marmoset monkey and human hippocampal formation. In the rat vas deferens and dog saphenous vein (two prototypical Y2 bioassays), BIIE0246 induced parallel shifts to the right of NPY concentration‐response curves with pA2 values of 8.1 and 8.6, respectively. In the rat colon (a Y2/Y4 bioassay), BIIE0246 (1 μM) completely blocked the contraction induced by PYY3–36, but not that of [Leu31,Pro34]NPY (a Y1, Y4 and Y5 agonist) and hPP (a Y4 and Y5 agonist). Additionally, BIIE0246 failed to alter the contractile effects of NPY in prototypical Y1 in vitro bioassays. Taken together, these results demonstrate that BIIE0246 is a highly potent, high affinity antagonist selective for the Y2 receptor subtype. It should prove most useful to establish further the functional role of the Y2 receptor in the organism.

Inhibitory effect of BIBN4096BS on cephalic vasodilatation induced by CGRP or transcranial electrical stimulation in the rat.

Calcitonin gene‐related peptide (CGRP) is believed to play a pivotal role in the pathogenesis of migraine via activation of CGRP receptors in the trigeminovascular system. The CGRP receptor antagonist, BIBN4096BS, has proven efficacy in the acute treatment of migraine attacks and represents a new therapeutic principle. We used an improved closed cranial window model to measure changes of the middle meningeal artery (MMA) and cortical pial artery/arteriole diameter (PA) and changes in local cortical cerebral blood flow (LCBFFlux) in anaesthetised artificially ventilated rats. The ability of BIBN4096BS (i.v.) to prevent the vasodilatatory actions of rat‐αCGRP, βCGRP and endogenously released CGRP following transcranial electrical stimulation (TES) was investigated. BIBN4096BS was per se without vasoactive effect on any of the measured variables and significantly inhibited the hypotension induced by both types of CGRP (P<0.001). The αCGRP induced MMA dilatation was reduced from 97.4±14 to 2.1±1.3% (P<0.001) and the βCGRP induced dilatation was fully blocked by BIBN4096BS. ID50 was 5.4±1.6 μg kg−1 for αCGRP and 16.3±1.6 μg kg−1 for βCGRP. Transcranial electrical stimulation induced a 119.1±6.9% increase in MMA diameter. BIBN4096BS (333 μg kg−1) attenuated this increase (19.8±2.1%) (P<0.001). Systemic CGRP and TES induced an increase in PA diameter that was not significantly inhibited by BIBN4096BS. The CGRP induced increase in LCBFFlux was similar not prevented by the antagonist. We suggest that systemic BIBN4096BS exerts its inhibitory action mainly on large dural blood vessels (MMA).

Regulation of neuropeptide Y release by neuropeptide Y receptor ligands and calcium channel antagonists in hypothalamic slices.

Abstract : Neuropeptide Y (NPY) is an important regulator of energy balance in mammals through its orexigenic, antithermogenic, and insulin secretagogue actions. We investigated the regulation of endogenous NPY release from rat hypothalamic slices by NPY receptor ligands and calcium channel antagonists. High‐potassium stimulation (60 mM) of the slices produced a calcium‐dependent threefold increase in NPY release above basal release. The Y2 receptor agonists NPY(13‐36) and N‐acetyl[Leu28, Leu31]NPY(24‐36), the Y4 agonist rat pancreatic polypeptide (rPP), and the Y4/Y5 agonist human pancreatic polypeptide (hPP) significantly reduced both basal and stimulated NPY release. NPY(13‐36)‐induced reduction of NPY release could be partially prevented in the presence of the weak Y2 antagonist T4‐[NPY(33‐36)]4, whereas the hPP‐ and rPP‐induced inhibition of release was not affected by the Y5 antagonist CGP71683A or the Y1 antagonist BIBP3226. The selective Y1, Y2, and Y5 antagonists had no effect on either basal or potassium‐stimulated release when administered alone. The calcium channel inhibitors ω‐conotoxin GVIA (N‐type), ω‐agatoxin TK (P/Q‐type), and ω‐conotoxin MVIIC (Q‐type) all significantly inhibited potassium‐stimulated NPY release, without any effect on basal release, whereas nifedipine had no effect on either basal or stimulated release. Addition of both ω‐conotoxin GVIA and ω‐agatoxin TK together completely inhibited the potassium‐stimulated release. In conclusion, we have demonstrated that NPY release from hypothalamic slices is calcium‐dependent, involving N‐, P‐, and Q‐type calcium channels. NPY release is also inhibited by Y2 agonists and rPP/hPP, suggesting that Y2 and Y4 receptors may act as autoreceptors on NPY‐containing nerve terminals.