Novel potent 5-HT(1F) receptor agonists: structure-activity studies of a series of substituted N-[3-(1-methyl-4-piperidinyl)-1H-pyrrolo[3,2-b]pyridin-5-yl]amides

Positron Emission Tomography (PET) Imaging Tracers for Serotonin Receptors

Serotonin (5-hydroxytryptamine, 5-HT) and 5-HT receptors (5-HTRs) have crucial roles in various neuropsychiatric disorders and neurodegenerative diseases, making them attractive diagnostic and therapeutic targets. Positron emission tomography (PET) is a noninvasive nuclear molecular imaging technique and is an essential tool in clinical diagnosis and drug discovery. In this context, numerous PET ligands have been developed for "visualizing" 5-HTRs in the brain and translated into human use to study disease mechanisms and/or support drug development. Herein, we present a comprehensive repertoire of 5-HTR PET ligands by focusing on their chemotypes and performance in PET imaging studies. Furthermore, this Perspective summarizes recent 5-HTR-focused drug discovery, including biased agonists and allosteric modulators, which would stimulate the development of more potent and subtype-selective 5-HTR PET ligands and thus further our understanding of 5-HTR biology.

Discovery and Biosynthesis of Antimicrobial Phenethylamine Alkaloids from the Marine Flavobacterium Tenacibaculum discolor sv11

The bacterial genus Tenacibaculum has been associated with various ecological roles in marine environments. Members of this genus can act, for example, as pathogens, predators, or episymbionts. However, natural products produced by these bacteria are still unknown. In the present work, we investigated a Tenacibaculum strain for the production of antimicrobial metabolites. Six new phenethylamine (PEA)-containing alkaloids, discolins A and B (1 and 2), dispyridine (3), dispyrrolopyridine A and B (4 and 5), and dispyrrole (6), were isolated from media produced by the predatory bacterium Tenacibaculum discolor sv11. Chemical structures were elucidated by analysis of spectroscopic data. Alkaloids 4 and 5 exhibited strong activity against Gram-positive Bacillus subtilis DSM10, Mycobacterium smegmatis ATCC607, Listeria monocytogenes DSM20600, and Staphylococcus aureus ATCC25923, with minimum inhibitory concentration (MIC) values ranging from 0.5 to 4 μg/mL, and moderate activity against Candida albicans FH2173 and Aspergillus flavus ATCC9170. Compound 6 displayed moderate antibacterial activities against Gram-positive bacteria. Dispyrrolopyridine A (4) was active against efflux pump deficient Escherichia coli ATCC25922 ΔtolC, with an MIC value of 8 μg/mL, as well as against Caenorhabditis elegans N2 with an MIC value of 32 μg/mL. Other compounds were inactive against these microorganisms. The biosynthetic route toward discolins A and B (1 and 2) was investigated using in vivo and in vitro experiments. It comprises an enzymatic decarboxylation of phenylalanine to PEA catalyzed by DisA, followed by a nonenzymatic condensation to form the central imidazolium ring. This spontaneous formation of the imidazolium core was verified by means of a synthetic one-pot reaction using the respective building blocks. Six additional strains belonging to three Tenacibaculum species were able to produce discolins, and several DisA analogues were identified in various marine flavobacterial genera, suggesting the widespread presence of PEA-derived compounds in marine ecosystems.

Design, synthesis and biological evaluation of pyridinylmethylenepiperidine derivatives as potent 5-HT1F receptor agonists for migraine therapy

Migraine is a common neurovascular disease which has been classified as the sixth most disabling disorder. Current migraine therapy was triptans, however, riptans can cause contraction of blood vessels. Therefore, novel drugs without cardiovascular effects emerged, such as CGRP and selective 5-HT1F receptor agonists. In this work, a series of pyridinylmethylenepiperidine derivatives were designed, synthesized and evaluated for their 5-HT1F receptor agonist activity. The results in vitro showed that compound C1-C6 displayed potent agonist activities compared with positive drug lasmiditan. Pharmacokinetic properties in rat indicated that 2,4,6-trifluoro-N-(6-(fluoro(1-methylpiperidin-4-ylidene)methyl)pyridin-2-yl)benzamide (C5) possessed high AUC and good bioavailability. In two rodent models of migraine, C5 significantly inhibited dural plasma protein extravasation and c-fos expression in the trigeminal nucleus caudalis. Moreover, C5 showed no effect on vasoconstriction. Through these studies, we identified C5 as a potent 5-HT1F receptor agonist for migraine therapy.

International Union of Basic and Clinical Pharmacology. CX. Classification of Receptors for 5-hydroxytryptamine; Pharmacology and Function

5-HT receptors expressed throughout the human body are targets for established therapeutics and various drugs in development. Their diversity of structure and function reflects the important role 5-HT receptors play in physiologic and pathophysiological processes. The present review offers a framework for the official receptor nomenclature and a detailed understanding of each of the 14 5-HT receptor subtypes, their roles in the systems of the body, and, where appropriate, the (potential) utility of therapeutics targeting these receptors. SIGNIFICANCE STATEMENT: This review provides a comprehensive account of the classification and function of 5-hydroxytryptamine receptors, including how they are targeted for therapeutic benefit.

9-Benzoyl 9-deazaguanines as potent xanthine oxidase inhibitors

A novel potent xanthine oxidase inhibitor, 3-nitrobenzoyl 9-deazaguanine (LSPN451), was selected from a series of 10 synthetic derivatives. The enzymatic assays were carried out using an on-flow bidimensional liquid chromatography (2D LC) system, which allowed the screening¸ the measurement of the kinetic inhibition constant and the characterization of the inhibition mode. This compound showed a non-competitive inhibition mechanism with more affinity for the enzyme-substrate complex than for the free enzyme, and inhibition constant of 55.1±9.80 nM, about thirty times more potent than allopurinol. Further details of synthesis and enzymatic studies are presented herein.

2-Acylaminopyridin-4-ylimidazoles as p38 MAP kinase inhibitors: Design, synthesis, and biological and metabolic evaluations

Targeting cytokines has become an important focus in the treatment of many inflammatory disorders. p38 MAP kinase (MAPK) is the key enzyme in regulating the biosynthesis and release of pro-inflammatory cytokines such as IL-1beta and TNFalpha. Inhibition of p38 MAPK results in decreased expression of these cytokines. Tri- and tetrasubstituted pyridinylimidazoles are potent inhibitors of p38 MAPK. Substitution on the pyridinyl moiety allows the design of inhibitors that show increased selectivity and activity by targeting the enzyme's hydrophobic region II. The objective of this study was to synthesize novel 1,2,4,5-tetrasubstituted imidazole derivates and to characterize them not only for their ability to inhibit p38 MAPK and modulate cytokine release in human whole blood, but also to evaluate their metabolic stability. Biological data and metabolic studies demonstrate that the introduction of a 2-acylamino function at C2 of the pyridine results in highly efficient and metabolically stable inhibitors relative to C2-alkylamino derivatives. A series of novel candidates was investigated for metabolic stability in human liver microsomes and in human whole blood. Additionally, metabolic S-oxidation was investigated, and possible metabolites were synthesized.

Clinical pharmacology of the serotonin receptor agonist, zolmitriptan

Migraine is a common, often disabling, neurovascular disease that has been shown to be associated with abnormal serotonergic activity. Drugs that modulate serotonin receptors are commonly used in the acute treatment of a migraine attack. Zolmitriptan, a 5-hydroxytryptophan(1B/1D) receptor agonist, is once such drug that is used in acute migraine therapy. Zolmitriptan is FDA approved for the treatment of acute migraine attacks and there is recent literature demonstrating its efficacy in the acute treatment of cluster attacks. It is rapidly absorbed and is detectable in the plasma within 2 - 5 min for the nasal spray formulation and within 15 min for the oral formulations. Zolmitriptan reaches peak plasma levels in 2 - 4 h and significant plasma levels are maintained for up to 6 h and lower levels for over 15 h. As zolmitriptan's metabolism is predominantly hepatic, patients with severe hepatic impairment should not receive zolmitriptan. However, only 25% of zolmitriptan is bound to plasma proteins and thus it is unlikely for drug interactions involving the displacement of highly protein-bound drugs. Zolmitriptan is generally very well tolerated and less than half of patients in clinical trials have reported adverse events, most of which are mild and transient, although rare serious cardiovascular events have been reported with all triptans. When patients are appropriately selected, zolmitriptan is both a safe and effective acute care migraine treatment. In this review the biological role of serotonin and its receptors is covered, followed by an in-depth review of the pharmacodynamics, pharmacokinetics and efficacy of zolmitriptan. Finally, the clinical application of zolmitriptan's use in patients is dicussed.

Synthesis of 4-Arylpiperidines from 1-Benzyl-4-piperidone: Application of the Shapiro Reaction and Alkenylsilane Cross-Coupling

[reaction: see text] 1-Benzyl-3,4-unsaturated-4-piperidinyl benzyldimethylsilane has been prepared and observed to readily undergo palladium-catalyzed cross-coupling reactions with a variety of aryl iodides and aryl bromides to generate 3,4-unsaturated 4-arylpiperidines, often at ambient temperature.

Design, synthesis and evaluation of bicyclic benzamides as novel 5-HT1F receptor agonists

Several fused bicyclic systems have been investigated to serve as the core structure of potent and selective 5-HT1F receptor agonists. Replacement of the indole nucleus in 2 with indazole and 'inverted' indazole provided more potent and selective 5-HT1F receptor ligands. Indoline and 1,2-benzisoxazole systems also provided potent 5-HT1F receptor agonists, and the 5-HT1A receptor selectivity of the indoline- and 1,2-benzisoxazole-based 5-HT1F receptor agonists could be improved with modification of the benzoyl moiety of the benzamides. Through these studies, we found that the inherent geometries of the templates, not the nature of hybridization of the linking atom, were important for the 5-HT1F receptor recognition.

Functions of 5-HT2A receptor and its antagonists in the cardiovascular system

The serotonin (5-hydroxytryptamine, 5-HT) receptors have conventionally been divided into seven subfamilies, most of which have several subtypes. Among them, 5-HT(2A) receptor is associated with the contraction of vascular smooth muscle, platelet aggregation and thrombus formation and coronary artery spasms. Accordingly, selective 5-HT(2A) antagonists may have potential in the treatment of cardiovascular diseases. Sarpogrelate, a selective 5-HT(2A) antagonist, has been introduced clinically as a therapeutic agent for the treatment of ischemic diseases associated with thrombosis. Molecular modeling studies also suggest that sarpogrelate is a 5-HT(2A) selective antagonist and is likely to have pharmacological effects beneficial in the treatment of cardiovascular diseases. This review describes the above findings as well as the signaling linkages of the 5-HT(2A) receptors and the mode of agonist binding to 5-HT(2A) receptor using data derived from molecular modeling and site-directed mutagenesis.