Development of nociceptin receptor (NOP) agonists and antagonists.

The nociceptin opioid (NOP) receptor is the most recently discovered member of the family of the opioid receptors; its endogenous agonist is the peptide nociceptin. Due to the subsequent elucidation of its physiological role in both central and peripheral nervous system and in some non-neural tissues, there is a rapidly growing interest in the pharmacological application of substances active on this receptor. Despite the current clinical use of a morphinane-based NOP/MOP mixed ligand (buprenorphine) as an analgesic and in the treatment of drug addictions, so far just a few clinical trials have been made with selective NOP ligands. However, the perspective of their utilization is rapidly growing. Agonists can find applications in the treatment of neuropathic pain, anxiety, cough, drug addition, urinary incontinence, anorexia, congestive heart failure, hypertension; and antagonists for pain, depression, Parkinson's disease, obesity, and as memory enhancers. Besides peptide ligands, which are still subjected to many pharmacological investigations, many different chemical classes of NOP ligands have been discovered: piperidines, nortropanes, spiropiperidines, 4-amino-quinolines and quinazolines, and others. The new advances in establishing structure-activity relationships, also with the help of modeling studies, can permit the development of more active and selective molecules.

High resolution NMR conformational studies of new bivalent NOP receptor antagonists in model membrane systems.

The interaction of new bivalent NOP receptor antagonists with dodecyl phosphatidylcholine micelles and DMPC/cholesterol liposomes was investigated in solution by high resolution NMR. The ligands are structurally related to the NOP antagonist JTC-801 plus a propanediamine or heptanediamine spacer between the pharmacophoric units. Ligand internuclear distances were derived from 2D NOESY data and applied to molecular modelling calculations as conformational restraints. NMR experiments on micelles evidenced that the ligands closely approached the micelles but gave no hints on the preferential conformations of the interacting ligands. Results from NMR experiments in the presence of liposomes clearly indicated that both ligands strongly interacted with the bilayer assuming a preferential folded conformation with the quinoline arms superimposing on each other. The finding suggested that these strongly lipophilic pharmacophores could localize in the native receptorial membrane in the form of a depot, gaining access to the recognition site via the lipid bilayer.

Small Molecules with Anti-Prion Activity.

Prion pathologies are fatal neurodegenerative diseases caused by the misfolding of the physiological Prion Protein (PrPC) into a ß-structure-rich isoform called PrPSc. To date, there is no available cure for prion diseases and just a few clinical trials have been carried out. The initial approach in the search of anti-prion agents had PrPSc as a target, but the existence of different prion strains arising from alternative conformations of PrPSc, limited the efficacy of the ligands to a straindependent ability. That has shifted research to PrPC ligands, which either act as chaperones, by stabilizing the native conformation, or inhibit its interaction with PrPSc. The role of transition-metal mediated oxidation processes in prion misfolding has also been investigated. Another promising approach is the indirect action via other cellular targets, like membrane domains or the Protein- Folding Activity of Ribosomes (PFAR). Also, new prion-specific high throughput screening techniques have been developed. However, so far no substance has been found to be able to extend satisfactorily survival time in animal models of prion diseases. This review describes the main features of the Structure-Activity Relationship (SAR) of the various chemical classes of anti-prion agents.

Synthesis and pharmacological evaluation of 1,2-dihydrospiro[isoquinoline-4(3H),4'-piperidin]-3-ones as nociceptin receptor agonists.

Some synthesized 1,2-dihydrospiro[isoquinoline-4(3 H),4'-piperidin]-3-ones were evaluated as ligands for nociceptin receptor (NOP receptor). Their affinity was established by binding studies, and efficacy was investigated by GTP binding experiments. Selectivity toward DOP, KOP, and MOP receptors was assessed, and structural requirements affecting affinity and selectivity were remarked. Most notably, compound 6d displayed nanomolar NOP receptor affinity and showed more than 800-fold selectivity. The new structures exerted full or partial agonistic activity.

Nociceptin /Orphanin FQ Peptide (NOP) Receptor Modulators: An Update in Structure-Activity Relationships.

Nociceptin /Orphanin FQ Peptide" receptor (NOPr) is a G-protein-coupled receptor with the nociceptin/orphanin FQ peptide (N/OFQ) as endogenous agonist. It is expressed in the nervous system as well as in some non-neural tissues. Its activation has pronociceptive effect at the supraspinal level, whereas at the spinal level it produces nociceptive effects at low doses and antinociceptive effects at higher doses. NOPr is also involved in mood and blood pressure regulation, immunoregulation, airway constriction, feeding, urination, bowel motility, learning and memory. Selective NOPr agonists have been tested clinically as anxiolytics and antitussives, and the antagonists as analgesics, antidepressants and in the treatment of alcohol addiction. Two NOPr radioligands have also been tested in humans as neuroimaging agents. Furthermore, the partial agonist peptide SER100 and N/OFQ have been used in clinical trials, respectively for congestive heart failure and overactive bladder. The evidence of interactions between NOP and µ-opioid receptor (MOPr) receptors has been exploited in the use of mixed NOPr/MOPr modulators as analgesics and in the treatment of drug addiction. These drugs are devoid of typical opioid liabilities. In this review, we outline the latest advances in the structure-activity relationships (SAR) of NOPr agonists and antagonists, with emphasis on affinity, activity, selectivity and pharmacokinetic features.

Screening of preservatives by HPLC-PDA-ESI/MS: A focus on both allowed and recently forbidden compounds in the new EU cosmetics regulation.

Commission regulation (EU) No 358/2014 amending the new regulation (EC) No 1223/2009 on cosmetics has prohibited the use of isopropyl-, isobutyl-, phenyl-, benzyl- and pentylparaben. Furthermore, Commission regulation (EU) No 1004/2014 has lowered the maximum permitted concentration of butyl- and propylparaben in cosmetics and it has also banned them in leave-on products designed for application on the nappy area of children under three years of age. A HPLC-PDA-ESI/MS method has been developed herein for the detection of seventeen preservatives, both the most utilised and the recently forbidden by the new EU regulations. The separation of these compounds, including benzoic acid and its derivatives in a 1.10 - 3.04 log Pow range, has been performed with a gradient elution on a Symmetry(®) C18 column (250×4.6mm i.d., particle size 5µm) with water and acetonitrile (0.1% formic acid) as mobile phase. Quantification has been carried out by HPLC-PDA. The method has been validated and successfully applied to the analysis of a large number of cosmetics with different functions like rinse-off and leave-on, or composition like skin, hair, face and oral products.

A new synthetic approach of N-(4-amino-2-methylquinolin-6-yl)-2-(4-ethylphenoxymethyl)benzamide (JTC-801) and its analogues and their pharmacological evaluation as nociceptin receptor (NOP) antagonists.

A series of 4-amino-2-methylquinoline and 4-aminoquinazoline derivatives, including the reference NOP antagonist JTC-801, were synthesized by an alternative pathway and their in vitro pharmacological properties were investigated. 3-Substitution of the quinoline ring resulted very critical for affinity. So 3-methyl derivative 4j showed a similar potency compared with the reference 4h while bulky lipophilic or electron withdrawing groups in the same position strongly decreased affinity. Structural and conformational requirements for affinity were outlined by NOE NMR and computational methods and suggestions for a pharmacophore model design were provided.

Synthesis and cholinesterase activity of phenylcarbamates related to Rivastigmine, a therapeutic agent for Alzheimer's disease.

In order to develop new cholinesterase agents effective against Alzheimer's disease (AD) we synthesized some phenylcarbamates structurally related to Rivastigmine and evaluated their in vitro and in vivo biological activity. Among the compounds which displayed the most significant in vitro activity, 1-[1-(3-dimethylcarbamoyloxyphenyl)ethyl]piperidine (31b), in addition to a simple and cheaper synthesis, showed lower toxicity and very similar therapeutic index in comparison with Rivastigmine.

Characterization of Sildenafil analogs by MS/MS and NMR: a guidance for detection and structure elucidation of phosphodiesterase-5 inhibitors.

Novel synthetic analogs of Sildenafil are constantly detected as adulterants in counterfeit drugs and dietary supplements. Their intake constitutes a serious health hazard as side effects are unknown. In this paper an investigation is carried out on NMR and MS/MS spectra of Sildenafil, Thiosildenafil, Acetildenafil and thirteen of their analogs: a list of key signals is reported and discussed with the intent to provide a tool that can help in detecting adulteration and in elucidating the structure of novel analogs. In this view extensive spectral data were reported, discussed and summarized in tables. A discussion on mass fragmentation and NMR chemical shifts is also provided to rationalize assignation. Moreover, a comprehensive information on the route of synthesis is provided for the benefit of those medicines control laboratories that need to synthesize analogs reference standards in-house.

Synthesis and pharmacological evaluation of bivalent antagonists of the nociceptin opioid receptor.

Bivalent ligands constituted by two identical pharmacophores structurally related to the Nociceptin Opioid Receptor (NOPr) antagonist JTC-801 were synthesized and their binding affinities for NOPr were evaluated. The novel ligands are formed by two modified JTC-801 units linked by di-iminic and di-aminic spacers with length ranging from three to ten methylene units. Moreover, the synthesis and the pharmacological characterization were extended to the corresponding univalent ligands. The latter compounds consisted in a single modified JTC-801 unit and an alkyl or alkylamino or alkylimino tail. The purpose of this study is to feature the location and surroundings of the allosteric binding site(s) of pharmacophores containing the 4-aminoquinoline structure. Most important, the bivalent ligands were exploited to reveal the eventual occurrence of a supramolecular receptorial architecture of the NOPr. All the bivalent derivatives 4 and 5 proved to be active in the nanomolar range with no outstanding dependence on the chain length. They showed potencies from three to ten times higher than the corresponding monomers. Consequently, results clearly indicated a positive role of the second pharmacophore in the ligand-protein interaction. The pharmacological profile of the monomers 7 and 8 clarified the contribution of the linker chain to NOP receptor affinity and suggested the presence of a lipophilic acidic site neighbouring the binding site of the JTC-like ligands. Selectivity of saturated compounds 5, 7, and 8 was tested by binding experiments on δ, κ and µ opioid receptors. Results indicated a general loss of selectivity as compared to JTC-801. In the [(35)S]GTPγS binding assay, all the compounds revealed antagonistic properties at the NOP Receptor. In conclusion the present study set the basis for a systematic investigation on the structural modifications that can be introduced into novel ligands for NOPr and helped to feature the surrounds of the allosteric site of NOPr.

Synthesis of new 4-heteroaryl-2-phenylquinolines and their pharmacological activity as NK-2/NK-3 receptor ligands.

Substituted 4-heteroaryl-2-phenylquinolines were synthesized and tested on NK-2 and NK-3 receptors in order to get a better insight in the structure-activity relationship. On the whole, these molecules, which can be regarded as bioisosters of the NK-3 antagonist SB 218795, displayed a lower activity than the template. Ring electronic distribution and H-bond donor and acceptor positions played some role in selectivity, 2-imidazolyl substituted 2a showing affinity mainly towards NK-3 while 3-pyrazolyl substituted 4 displayed a preferential interaction with NK-2 receptor. Structural characterization of the synthesized compounds was achieved by NMR and mass techniques. Bidimensional 1H-NOESY experiments were a helpful tool for the assignment of the isomeric structures of compounds 9 and llb-c.

Metabolic alterations in cultured mouse fibroblasts induced by an inhibitor of the tyrosine kinase receptor Fibroblast Growth Factor Receptor 1.

Proton nuclear magnetic resonance (NMR) spectroscopy was used to identify and quantify the metabolites present in cultured mouse fibroblast cells 3T6 in their native state and after treatment with PD166866, an inhibitor of the fibroblast growth factor receptor. Cell extracts were prepared according to the Bligh-Dyer protocol which prevents artifacts deriving from the chemical demolition of macromolecules. Also the growth medium was subjected to the same extraction procedure. The NMR approach made possible the identification and quantification of about 40 different metabolites at nanomoles/mg of protein level: the biological relevance of the variation of some metabolite levels is discussed. Our experimental procedure offers a prospective method for the evaluation of variations of the metabolic profile deriving from different biochemical treatments of these cells.

Synthesis and evaluation as NOP ligands of some spiro[piperidine-4,2'(1'H)-quinazolin]-4'(3'H)-ones and spiro[piperidine-4,5'(6'H)-[1,2,4]triazolo[1,5-c]quinazolines].

Some spiro[piperidine-4,2'(1'H)-quinazolin]-4'(3'H)-ones 3 and spiro[piperidine-4,5'(6'H)-[1,2,4]triazolo[1,5-c]quinazolines] 4 were synthesized and evaluated as ligands of the nociceptin receptor. The examined compounds showed partial agonistic activity, except compounds 3, 4n that proved to be pure antagonists.

Synthesis of 1-methyl-5-(pyrazol-3- and -5-yl- and 1, 2, 4-triazol-3- and 5-yl)-1, 2, 3, 6-tetrahydropyridine derivatives and their evaluation as muscarinic receptor ligands.

A series of 1-methyl-5-(pyrazol-3- and -5-yl- and 1, 2, 4-triazol-3- and 5-yl)-1, 2, 3, 6-tetrahydropyridine derivatives structurally related to arecoline were synthesized and evaluated on M(1), M(2), and M(3) muscarinic receptors using [(3)H] pirenzepine and [(3)H] NMS as ligands. The binding affinity depended on the position and size of the substituents. The most interesting compounds were further evaluated in functional studies on isolated organs and in vivo for cholinergic side effects. Compounds 5 l and 6 i good M(1) and M(3) antagonistic properties in vitro and were devoid of cholinergic side effects in vivo.