Wolfram Gaida

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.

Ambroxol, a Nav1.8-preferring Na(+) channel blocker, effectively suppresses pain symptoms in animal models of chronic, neuropathic and inflammatory pain.

Neuropathic pain affects many patients, and treatment today is far from being perfect. Nav1.8 Na(+) channels, which are expressed by small fibre sensory neurons, are promising targets for novel analgesics. Na(+) channel blockers used today, however, show only limited selectivity for this channel subtype, and can cause dose-limiting side effects. Recently, the secretolytic ambroxol was found to preferentially inhibit Nav1.8 channels. We used this compound as a tool to investigate whether a Nav1.8-preferring blocker can suppress symptoms of chronic, neuropathic and inflammatory pain in animal models. The drug was tested in the formalin paw model, two models of mononeuropathy, and a model of monoarthritis in rats. Ambroxols effects were compared with those of gabapentin. Ambroxol at a dose of 1g/kg had to be administered to rats to achieve the plasma levels that are reached in clinical use (for the treatment of infant and acute respiratory distress syndrome). Ambroxol (1g/kg) was only weakly effective in models for acute pain, but effectively reduced pain symptoms in all other models; in some cases it completely reversed pain behaviour. In most cases the effects were more pronounced than those of gabapentin (at 100mg/kg). These data show that a Nav1.8-preferring Na(+) channel blocker can effectively suppress pain symptoms in a variety of models for chronic, neuropathic and inflammatory pain at plasma levels, which can be achieved in the clinic.

Pharmacodynamic profile of the M1 agonist talsaclidine in animals and man

In functional pharmacological assays, talsaclidine has been described as a functionally preferential M1 agonist with full intrinsic activity, and less pronounced effects at M2- and M3 receptors. In accordance with this, cholinomimetic central activation measured in rabbits by EEG recordings occurred at a 10 fold lower dose than that inducing predominantly M3-mediated side effects. This pharmacological profile is also reflected in the clinical situation: Both in healthy volunteers and in Alzheimer patients--unlike after unspecific receptor stimulation through cholinesterase inhibitors--the mainly M3-mediated gastrointestinal effects (like nausea and vomiting) were not dose-limiting. Rather, sweating and hypersalivation, mediated through muscarinic receptors, occurred dose-dependently and were finally dose-limiting. In contrast to talsaclidine, sabcomeline had a less pronounced functional M1 selectivity in pharmacological assays. This was also shown in anaesthetized guinea pigs where sabcomeline alone induced bronchoconstriction, and in the rabbit EEG where central activation and cholinergic side effects occurred in the same dose range. Neither drug, however, showed convincing improvement of cognitive functions in patients with mild-to-moderate Alzheimers disease. This asks for a reassessment of the muscarinic hypothesis for the treatment of this disease.

Structure activity studies of mast cell activation and hypotension induced by neuropeptide Y (NPY), centrally truncated and C‐terminal NPY analogues

1 Neuropeptide‐induced histamine release is thought to occur via receptor‐independent mechanisms, with net charge and lipophilicity being important factors. 2 In this study, the histamine releasing ability of neuropeptide Y (NPY), two C‐terminal segments of NPY and 13 centrally truncated NPY analogues was examined. These results were compared with the ability of the peptides to bind to the Y2 receptor in the rabbit kidney membrane model and with their hypotensive actions in the anaesthetized‐rat model. 3 All analogues tested, with the exception of [Glu4,25,33,35]‐NPY(1–4)‐Ahx‐(25–36) and [Asp4,25,33,35]NPY(1–4)‐Ahx‐(25–36) which were devoid of histamine releasing activity, evoked a dose‐dependent histamine release but there were marked differences between the peptides. The native peptide was the least active. 4 Histamine release was not linked to the ability of the peptides to displace NPY from Y2 receptors. There was a statistical correlation between the hypotensive effects expressed as ED10 values (μmol kg−1, which induced a blood pressure decrease of 10 mmHg) and the EC25 for histamine release (r = 0.62, P = 0.04), although histamine release may not be the sole determinant of the alterations in blood pressure. 5 There was a strong negative correlation between EC25 for histamine release and net positive charge (r = −0.93, P = 5.7 × 10−7), i.e. increasing the net positive charge caused greater histamine release. However, there was a 12 fold difference in activity amongst the most positively charged analogues (+ 5). Helicity did not correlate with histamine releasing ability. 6 In the development of NPY‐related drugs the avoidance of compounds with net positive charge is recommended.

CYCLOPEPTIDE ANALOGS FOR CHARACTERIZATION OF THE NEUROPEPTIDE Y Y2-RECEPTOR

A discontinuous 17-amino acid peptide analog of neuropeptide Y (NPY), NPY 1-4-Ahx-25-36 containing 6-aminohexanoic acid instead of the residues 5 to 24, was found to bind preferentially to Y2 subtypes of NPY receptors. In order to further characterize the binding site, three different types of cyclic analogs were synthesized. Firstly lactamisation between residues 2 and 30 led to the most selective Y2-agonist, secondly lactamisation between the N-terminus and residue 31 reduced binding significantly. Thirdly, any cyclization including the C-terminus led to an inactive compound. Circular dichroism revealed different conformations for the three analogs with reduced alpha-helical content in comparison to the linear ana-log. The different conformation of the peptides has been confirmed by molecular dynamics simulations. A model for peptide-receptor interaction is suggested.

Novel Y2-selective, reduced-size agonists of neuropeptide Y

Abstract The prerequisite for Y2-mediated biological activity was elaborated by synthesizing analogs of neuropeptide Y (NPY) 1-4-Ahx-25-36. The finding, that a pronounced hydrophobic segment is required in the C-terminal segment for signal transduction led to the development of a Y2-selective agonist, which contains cyclohexylalanine at position 30 and/or 31.

314 IN VIVO CHARACTERIZATION OF SELECTIVE TRPV1 ANTAGONIST BCTC IN DIFFERENT ANIMAL MODELS OF ACUTE AND CHRONIC PAIN

in thalamus, basal ganglia, insula, secondary somatosensory cortex (SII) and anterior cingulate cortex (ACC), and in the right cerebellum. The group map from the rotations of the non-painful shoulder demonstrated activity only in contralateral SII and insula. Conclusions: We have shown that movement induced allodynia is measurable using fMRI. Movement induced allodynia in the diseased shoulder activated the pain matrix while the identical range of movement in the normal shoulder did not. Patients are currently being assessed post surgically to determine whether objective fMRI related brain activity changes concur with subjective rating changes.