Pyrrolidino-tetrahydroisoquinolines bearing pendant heterocycles as potent dual H3 antagonist and serotonin transporter inhibitors

Molecular Modelling of Potential Candidates for the Treatment of Depression

A lot of research initiatives in the last decades have been focused on the search of new strategies to treat depression. However, despite the availability of various antidepressants, current treatment is still far from ideal. Unwanted side effects, modest response rates and the slow onset of action are the main shortcomings. As a strategy to improve symptomatic relief and response rates, the dual modulation of the serotonin transporter and the histamine H₃ receptor by a single chemical entity has been proposed in the literature. Accordingly, this work aims to elucidate key structural features responsible for the dual inhibitory activity of the hexahydro-pyrrolo-isoquinoline derivatives. For this purpose, two approaches were employed, four-dimensional quantitative structure-activity relationship (4D-QSAR) and molecular docking. The 4D-QSAR models for both receptors allowed the identification of the pharmacophore groups critical for the modelled biological activity, whereas the binding mode of this class of compounds to the human serotonin transporter was assessed by molecular docking. The findings can be applicable to design new antidepressants.

Multi-target therapeutics for neuropsychiatric and neurodegenerative disorders

Historically, neuropsychiatric and neurodegenerative disease treatments focused on the 'magic bullet' concept; however multi-targeted strategies are increasingly attractive gauging from the escalating research in this area. Because these diseases are typically co-morbid, multi-targeted drugs capable of interacting with multiple targets will expand treatment to the co-morbid disease condition. Despite their theoretical efficacy, there are significant impediments to clinical success (e.g., difficulty titrating individual aspects of the drug and inconclusive pathophysiological mechanisms). The new and revised diagnostic frameworks along with studies detailing the endophenotypic characteristics of the diseases promise to provide the foundation for the circumvention of these impediments. This review serves to evaluate the various marketed and nonmarketed multi-targeted drugs with particular emphasis on their design strategy.

Multiple Targeting Approaches on Histamine H3 Receptor Antagonists

With the very recent market approval of pitolisant (Wakix®), the interest in clinical applications of novel multifunctional histamine H₃ receptor antagonists has clearly increased. Since histamine H₃ receptor antagonists in clinical development have been tested for a variety of different indications, the combination of pharmacological properties in one molecule for improved pharmacological effects and reduced unwanted side-effects is rationally based on the increasing knowledge on the complex neurotransmitter regulations. The polypharmacological approaches on histamine H₃ receptor antagonists on different G-protein coupled receptors, transporters, enzymes as well as on NO-signaling mechanism are described, supported with some lead structures.

Carbazole incorporated ratiometric chemosensor for Zn2+

An electron donating carbazole incorporated thiazole (3) based Zn(2+) selective intrinsic chemosensor has been synthesized and investigated. It was found that electron donating substituents such as methyl and carbazole on chemosensor (1) produce remarkable red shift in emission upon complexation with Zn(2+). The sensor shows a selective fluorescence response with Zn(2+) over biologically relevant cations (Ca(2+), Mg(2+), Na(+), and K(+)) and biologically non-relevant cations (Cd(2+), In(3+) and Ga(3+)) in an aqueous ethanol system. It also produce an enhancement in the quantum yield and a longer emission wavelength shift on Zn(2+) binding with the potential of a ratiometric assay.

Utilization of the 1,2,3,5-thiatriazolidin-3-one 1,1-dioxide scaffold in the design of potential inhibitors of human neutrophil proteinase 3

The S' subsites of human neutrophil proteinase 3 (Pr 3) were probed by constructing diverse libraries of compounds based on the 1,2,3,5-thiatriazolidin-3-one 1,1-dioxide using combinational and click chemistry methods. The multiple points of diversity embodied in the heterocyclic scaffold render it well-suited to the exploration of the S' subsites of Pr 3. Molecular modeling studies suggest that further exploration of the S' subsites of Pr 3 using the aforementioned heterocyclic scaffold may lead to the identification of highly selective, reversible competitive inhibitors of Pr 3.

Dual- and triple-acting agents for treating core and co-morbid symptoms of major depression: novel concepts, new drugs

The past decade of efforts to find improved treatment for major depression has been dominated by genome-driven programs of rational drug discovery directed toward highly selective ligands for nonmonoaminergic agents. Selective drugs may prove beneficial for specific symptoms, for certain patient subpopulations, or both. However, network analyses of the brain and its dysfunction suggest that agents with multiple and complementary modes of action are more likely to show broad-based efficacy against core and comorbid symptoms of depression. Strategies for improved multitarget exploitation of monoaminergic mechanisms include triple inhibitors of dopamine, serotonin (5-HT) and noradrenaline reuptake, and drugs interfering with feedback actions of monoamines at inhibitory 5-HT(1A), 5-HT(1B) and possibly 5-HT(5A) and 5-HT(7) receptors. Specific subsets of postsynaptic 5-HT receptors mediating antidepressant actions are under study (e.g., 5-HT(4) and 5-HT(6)). Association of a clinically characterized antidepressant mechanism with a nonmonoaminergic component of activity is an attractive strategy. For example, agomelatine (a melatonin agonist/5-HT(2C) antagonist) has clinically proven activity in major depression. Dual neurokinin(1) antagonists/5-HT reuptake inhibitors (SRIs) and melanocortin(4) antagonists/SRIs should display advantages over their selective counterparts, and histamine H(3) antagonists/SRIs, GABA(B) antagonists/SRIs, glutamatergic/SRIs, and cholinergic agents/SRIs may counter the compromised cognitive function of depression. Finally, drugs that suppress 5-HT reuptake and blunt hypothalamo-pituitary-adrenocorticotrophic axis overdrive, or that act at intracellular proteins such as GSK-3beta, may abrogate the negative effects of chronic stress on mood and neuronal integrity. This review discusses the discovery and development of dual- and triple-acting antidepressants, focusing on novel concepts and new drugs disclosed over the last 2 to 3 years.

Dual serotonin transporter inhibitor/histamine H3 antagonists: development of rigidified H3 pharmacophores

A series of tetrahydroisoquinolines acting as dual serotonin transporter inhibitor/histamine H(3) antagonists is described. The introduction of polar aromatic spacers as part of the histamine H(3) pharmacophore was explored. A convergent synthesis of the final products allowing late stage introduction of the aromatic side chain was developed. In vitro and in vivo data are discussed.