Synthesis and biological evaluation of new multi-target 3-(1H-indol-3-yl)pyrrolidine-2,5-dione derivatives with potential antidepressant effect

Development of heterocyclic-based frameworks as potential scaffold of 5-HT1A receptor agonist and future perspectives: A review

As a subtype of the 5-hydroxytryptamine (5-HT) receptor, 5-HT1A receptors are involved in the pathological process of psychiatric disorders and is an important target for antidepressants. The research groups focus on these area have tried to design novel compounds to alleviate depression by targeting 5-HT1A receptor. The heterocyclic structures is an important scaffold to enhance the antidepressant activity of ligands, including piperazine, piperidine, benzothiazole, and pyrrolidone. The current review highlights the function and significance of nitrogen-based heterocyclics 5-HT1AR represented by piperazine, piperidine, benzothiazole, and pyrrolidone in the development of antidepressant.

Advances in drug design and therapeutic potential of selective or multitarget 5-HT1A receptor ligands

5-HT1A receptor (5-HT1A-R) is a serotoninergic G-protein coupled receptor subtype which contributes to several physiological processes in both central nervous system and periphery. Despite being the first 5-HT-R identified, cloned and studied, it still represents a very attractive target in drug discovery and continues to be the focus of a myriad of drug discovery campaigns due to its involvement in numerous neuropsychiatric disorders. The structure-activity relationship studies (SAR) performed over the last years have been devoted to three main goals: (i) design and synthesis of 5-HT1A-R selective/preferential ligands; (ii) identification of 5-HT1A-R biased agonists, differentiating pre- versus post-synaptic agonism and signaling cellular mechanisms; (iii) development of multitarget compounds endowed with well-defined poly-pharmacological profiles targeting 5-HT1A-R along with other serotonin receptors, serotonin transporter (SERT), D2-like receptors and/or enzymes, such as acetylcholinesterase and phosphodiesterase, as a promising strategy for the management of complex psychiatric and neurodegenerative disorders. In this review, medicinal chemistry aspects of ligands acting as selective/preferential or multitarget 5-HT1A-R agonists and antagonists belonging to different chemotypes and developed in the last 7 years (2017-2023) have been discussed. The development of chemical and pharmacological 5-HT1A-R tools for molecular imaging have also been described. Finally, the pharmacological interest of 5-HT1A-R and the therapeutic potential of ligands targeting this receptor have been considered.

The 5-HT7 receptor system as a treatment target for mood and anxiety disorders: A systematic review

BACKGROUND

Preclinical animal and preliminary human studies indicate that 5-HT7 antagonists have the potential as a new treatment approach for mood and anxiety disorders. In this systematic review, we aimed to review the relationship between the 5-HT7 receptor system and mood and anxiety disorders, and to explore the pharmacology and therapeutic potential of medications that target the 5-HT7 receptor for their treatment.

METHODS

Medline, Cochrane Library, EMBASE, PsycINFO databases, the National Institute of Health website Clinicaltrials.gov, controlled-trials.com, and relevant grey literature were used to search for original research articles, and reference lists of included articles were then hand searched.

RESULTS

Sixty-four studies were included in the review: 52 animal studies and 12 human studies. Studies used a variety of preclinical paradigms and questionnaires to assess change in mood, and few studies examined sleep or cognition. Forty-four out of 47 (44/47) preclinical 5-HT7 modulation studies identified potential antidepressant effects and 20/23 studies identified potential anxiolytic effects. In clinical studies, 5/7 identified potential antidepressant effects in major depressive disorder, 1/2 identified potential anxiolytic effects in generalized anxiety disorder, and 3/3 identified potential antidepressant effects in bipolar disorders.

CONCLUSION

While there is some evidence that the 5-HT7 receptor system may be a potential target for treating mood and anxiety disorders, many agents included in the review also bind to other receptors. Further research is needed using drugs that bind specifically to 5-HT7 receptors to examine treatment proof of concept further.

Synthesis and biological evaluation of novel 3-(5-substituted-1H-indol-3-yl)pyrrolidine-2,5-dione derivatives with a dual affinity for serotonin 5-HT1A receptor and SERT

The serotonin 1A (5-HT1A) receptors and serotonin transporter (SERT) are important biological targets in the treatment of diseases of the central nervous system, especially for depression. In this study, new 3-(1H-indol-3-yl)pyrrolidine-2,5-dione derivatives linked with the 3-(1,2,3,6-tetrahydropyridin-4-yl)-1H-indole moiety were synthesised and evaluated for their affinity for 5-HT1A receptor and serotonin reuptake inhibition. Selected compounds were then tested for their affinity for D2, 5-HT2A, 5-HT6 and 5-HT7 receptors, and also in in vitro metabolic stability assays in human microsomes. Finally, in vivo assays allowed us to evaluate the agonist-antagonist properties of pre- and postsynaptic 5-HT1A receptors. 3-(1-(4-(3-(5-methoxy-1H-indol-3-yl)-2,5-dioxopyrrolidin-1-yl)butyl)-1,2,3,6-tetrahydropyridin-4-yl)-1H-indole-5-carbonitrile (4f) emerged as the most promising compound from the series, due to its favourable receptor binding profile (Ki(5-HT1A) = 10.0 nM; Ki(SERT) = 2.8 nM), good microsomal stability and 5-HT1A receptor agonistic activity.

Base-promoted synthesis of dihydrochromeno[4,3-d]pyrrolo[3,4-b]pyridines from 4-chloro-3-substituted coumarins and α-aminomaleimides

This paper describes the base-mediated cascade reactions of 4-chloro-3-substituted coumarins with α-aminomaleimides, allowing the efficient synthesis of dihydrochromeno[4,3-d]pyrrolo[3,4-b]pyridines with interesting chemoselectivity. These transformations include the domino-style formation of C-C/C-N bonds through a base-mediated nucleophilic substitution, Michael addition, N-cyclization, and elimination. The presented synthetic strategy has several advantages: it is simple, uses readily available starting materials and an environmentally friendly solvent, has a highly chemoselective route, and allows the purification of products via washing with EtOH (96%), a technique called GAP (Group-Assisted-Purification) chemistry.

Designing multi-target drugs for the treatment of major depressive disorder

INTRODUCTION

Major depressive disorders (MDD) pose major health burdens globally. Currently available medications have their limitations due to serious adverse effects, long latency periods as well as resistance. Considering the highly complicated pathological nature of this disorder, it has been suggested that multitarget drugs or multi-target-directed ligands (MTDLs) may provide long-term therapeutic solutions for the treatment of MDD.

AREAS COVERED

In the current review, recent lead design and lead modification strategies have been covered. Important investigations reported in the last ten years (2013-2022) for the pre-clinical development of MTDLs (through synthetic medicinal chemistry and biological evaluation) for the treatment of MDD were discussed as case studies to focus on the recent design strategies. The discussions are categorized based on the pharmacological targets. On the basis of these important case studies, the challenges involved in different design strategies were discussed in detail.

EXPERT OPINION

Even though large variations were observed in the selection of pharmacological targets, some potential biological targets (NMDA, melatonin receptors) are required to be explored extensively for the design of MTDLs. Similarly, apart from structure activity relationship (SAR), in silico techniques such as multitasking cheminformatic modelling, molecular dynamics simulation and virtual screening should be exploited to a greater extent.

The treatment of depression - searching for new ideas

Depression is a severe mental health problem that affects people regardless of social status or education, is associated with changes in mood and behavior, and can result in a suicide attempt. Therapy of depressive disorders is based mainly on drugs discovered in the 1960s and early 1970s. Selective serotonin reuptake inhibitors (SSRIs) and serotonin-norepinephrine reuptake inhibitors (SNRIs) are frontline pharmacological strategies for the medical treatment of depression. In addition, approved by FDA in 2019, esketamine [as nasal spray; N-methyl-D-aspartate (NMDA) receptors antagonist with additional effects on α-Amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) receptors, hyperpolarization-activated cyclic nucleotide-gated (HCN) channels, L-type voltage-dependent calcium channel (L-VDCC), opioid receptors, and monoaminergic receptors] is an essential compound in suicide and drug-resistant depression. However, the treatment of depression is burdened with severe side effects, and in many cases, it is ineffective. An equally important issue is the choice of antidepressant therapy in people with comorbid somatic diseases, for example, due to possible interactions with the patient's other drugs. Therefore, there is a great need for new antidepressants with different mechanisms of action and the need to refine the search for new substances. The purpose of this review was to discuss new research directions and new trends that dominate laboratories worldwide. We have reviewed the literature to present new points on the pharmacological target of substances with antidepressant activity. In addition, we propose a new perspective on depressive therapies.

Design Strategies, Chemistry and Therapeutic Insights of Multi-target Directed Ligands as Antidepressant Agents

Depression is one of the major disorders of the central nervous system worldwide and causes disability and functional impairment. According to the World Health Organization, around 265 million people worldwide are affected by depression. Currently marketed antidepressant drugs take weeks or even months to show anticipated clinical efficacy but remain ineffective in treating suicidal thoughts and cognitive impairment. Due to the multifactorial complexity of the disease, single-target drugs do not always produce satisfactory results and lack the desired level of therapeutic efficacy. Recent literature reports have revealed improved therapeutic potential of multi-target directed ligands due to their synergistic potency and better safety. Medicinal chemists have gone to great extents to design multitarget ligands by generating structural hybrids of different key pharmacophores with improved binding affinities and potency towards different receptors or enzymes. This article has compiled the design strategies of recently published multi-target directed ligands as antidepressant agents. Their biological evaluation, structural-activity relationships, mechanistic and in silico studies have also been described. This article will prove to be highly useful for the researchers to design and develop multi-target ligands as antidepressants with high potency and therapeutic efficacy.

Synthesis and Structural Study of Amidrazone Derived Pyrrole-2,5-Dione Derivatives: Potential Anti-Inflammatory Agents

1H-pyrrole-2,5-dione derivatives are known for their wide range of pharmacological properties, including anti-inflammatory and antimicrobial activities. This study aimed to synthesize new 3,4-dimethyl-1H-pyrrole-2,5-dione derivatives 2a–2f in the reaction of N³-substituted amidrazones with 2,3-dimethylmaleic anhydride and evaluate their structural and biological properties. Compounds 2a–2f were studied by the ¹H-¹³C NMR two-dimensional techniques (HMQC, HMBC) and single-crystal X-ray diffraction (derivatives 2a and 2d). The anti-inflammatory activity of compounds 2a–2f was examined by both an anti-proliferative study and a production study on the inhibition of pro-inflammatory cytokines (IL-6 and TNF-α) in anti-CD3 antibody- or lipopolysaccharide-stimulated human peripheral blood mononuclear cell (PBMC) cultures. The antibacterial activity of compounds 2a–2f against Staphylococcus aureus, Enterococcus faecalis, Micrococcus luteus, Esherichia coli, Pseudomonas aeruginosa, Yersinia enterocolitica, Mycobacterium smegmatis and Nocardia corralina strains was determined using the broth microdilution method. Structural studies of 2a–2f revealed the presence of distinct Z and E stereoisomers in the solid state and the solution. All compounds significantly inhibited the proliferation of PBMCs in anti-CD3-stimulated cultures. The strongest effect was observed for derivatives 2a–2d. The strongest inhibition of pro-inflammatory cytokine production was observed for the most promising anti-inflammatory compound 2a.

A new paradigm shift in antidepressant therapy? From dual-action to multitarget-directed ligands

Major Depressive Disorder is a chronic, recurring, and potentially fatal disease affecting up to 20% of the global population. Since the monoamine hypothesis was proposed more than 60 years ago, only a few relevant advances have been achieved, with very little disease course changing, from a pharmacological perspective. Moreover, since negative efficacy studies with novel molecules are frequent, many pharmaceutical companies have put new studies on hold. Fortunately, relevant clinical studies are currently being performed, and extensive striving is being developed by universities, research centers, and other public and private institutions. Depression is no longer considered a simple disease but a multifactorial one. New research fields are emerging in what could be a paradigm shift: the multitarget approach beyond monoamines. In this review, we summarize the present and the past of antidepressant drug discovery, with the aim to shed some light on the current state of the art in clinical and preclinical advances to face this increasingly devastating disease.

Identification of New Compounds with Anticonvulsant and Antinociceptive Properties in a Group of 3-substituted (2,5-dioxo-pyrrolidin-1-yl)(phenyl)-Acetamides

We report herein a series of water-soluble analogues of previously described anticonvulsants and their detailed in vivo and in vitro characterization. The majority of these compounds demonstrated broad-spectrum anticonvulsant properties in animal seizure models, including the maximal electroshock (MES) test, the pentylenetetrazole-induced seizure model (scPTZ), and the psychomotor 6 Hz (32 mA) seizure model in mice. Compound 14 showed the most robust anticonvulsant activity (ED₅₀ MES = 49.6 mg/kg, ED₅₀ 6 Hz (32 mA) = 31.3 mg/kg, ED₅₀scPTZ = 67.4 mg/kg). Notably, it was also effective in the 6 Hz (44 mA) model of drug-resistant epilepsy (ED₅₀ = 63.2 mg/kg). Apart from favorable anticonvulsant properties, compound 14 revealed a high efficacy against pain responses in the formalin-induced tonic pain, the capsaicin-induced neurogenic pain, as well as in the oxaliplatin-induced neuropathic pain in mice. Moreover, compound 14 showed distinct anti-inflammatory activity in the model of carrageenan-induced aseptic inflammation. The mechanism of action of compound 14 is likely complex and may result from the inhibition of peripheral and central sodium and calcium currents, as well as the TRPV1 receptor antagonism as observed in the in vitro studies. This lead compound also revealed beneficial in vitro ADME-Tox properties and an in vivo pharmacokinetic profile, making it a potential candidate for future preclinical development. Interestingly, the in vitro studies also showed a favorable induction effect of compound 14 on the viability of neuroblastoma SH-SY5Y cells.

Quantum mechanical, virtual screening, molecular docking, molecular dynamics, ADME and antimicrobial activity studies of some new indole-hydrazone derivatives as potent agents against E. faecalis

In this study, a new series of indole-5-carbaldehyde hydrazone derivative compounds were designed, synthesized, and their antimicrobial activities were determined by the microdilution method, and the in vitro cytotoxic effects on Beas-2b cell lines were investigated by MTT assay. When the activity results were examined, 5i12 showed promising activity against E. faecalis with MIC: 2 µg/mL compared to ampicillin, gentamicin, and vancomycin, although the antimicrobial activities of the indole derivatives were generally weaker than those of the standard drugs. Compounds showed no cytotoxic activity on the A549, MCF-7, and Beas-2b cell lines. Molecular docking studies were performed on 15 different proteins to understand the mechanism of 5i12's good antimicrobial action against E. faecalis, and it was concluded that the compounds interacted with FabH, not enough other protein structures. Molecular dynamics simulations were performed to investigate the protein-ligand stability of the most active compound against E. faecalis. The RMSD value of 5i12 varied between 0.02 and 0.16 nm during the MD simulation. The apoprotein peaked at 0.55 nm at the beginning of the simulation and stabilized below 0.5 nm. The theoretical ADME profiles of all compounds were calculated and found to comply with Lipinski and other limiting rules. In addition, some theoretical quantum parameters (HOMO-LUMO) of compounds, and both MEP analysis and geometric optimization analysis for 5i12 were calculated using the 6-311 G (d,p) base set and DFT/B3LYP theory, and the results were visualized. Communicated by Ramaswamy H. Sarma.

Curated Database and Preliminary AutoML QSAR Model for 5-HT1A Receptor

Introduction of a new drug to the market is a challenging and resource-consuming process. Predictive models developed with the use of artificial intelligence could be the solution to the growing need for an efficient tool which brings practical and knowledge benefits, but requires a large amount of high-quality data. The aim of our project was to develop quantitative structure–activity relationship (QSAR) model predicting serotonergic activity toward the 5-HT1A receptor on the basis of a created database. The dataset was obtained using ZINC and ChEMBL databases. It contained 9440 unique compounds, yielding the largest available database of 5-HT1A ligands with specified pKi value to date. Furthermore, the predictive model was developed using automated machine learning (AutoML) methods. According to the 10-fold cross-validation (10-CV) testing procedure, the root-mean-squared error (RMSE) was 0.5437, and the coefficient of determination (R²) was 0.74. Moreover, the Shapley Additive Explanations method (SHAP) was applied to assess a more in-depth understanding of the influence of variables on the model’s predictions. According to to the problem definition, the developed model can efficiently predict the affinity value for new molecules toward the 5-HT1A receptor on the basis of their structure encoded in the form of molecular descriptors. Usage of this model in screening processes can significantly improve the process of discovery of new drugs in the field of mental diseases and anticancer therapy.

Switchable regioselective hydroalkylation of 2-arylindoles with maleimides

A condition-based switchable regioselective hydroalkylation of 2-arylindoles with maleimides has been developed. The reaction in the presence of a Ru(ii)-catalyst resulted in hydroalkylation at the ortho-position of the C2-aryl ring via C-H activation whereas the reaction in the absence of the catalyst in TFE resulted in C3-hydroalkylation. Various functional groups both on the indole ring and on the 2-phenyl ring were tolerated and a wide range of hydroalkylated products were obtained in moderate to high (37-88%) yields.

Research progress in biological activities of succinimide derivatives

Succinimides are well recognized heterocyclic compounds in drug discovery which produce diverse therapeutically related applications in pharmacological practices. Researches in medicinal chemistry field have isolated and synthesized succinimide derivatives with multiple medicinal properties including anticonvulsant, anti-inflammatory, antitumor and antimicrobial agents, 5-HT receptor ligands and enzyme inhibitors. Simultaneously, SAR (Structure-Activity Relationship) analysis has been gradually possessed, along with a great deal of derivatives have been derived for potential targets. In this article, we comprehensively summarize the biological activities and SAR for succinimide derivatives, along with the featuring bioactive molecules reported in patents, wishing to provide an overall retrospect and prospect on the succinimide analogues.

Recent advances in multitarget-directed ligands targeting G-protein-coupled receptors

Mounting evidence indicates that single-target drugs might be inadequate to achieve satisfactory therapeutic effects on complex diseases. Recently, increasing attention has been paid to developing drugs that can manipulate multiple targets to generate beneficial effects through potential synergy. G-protein-coupled receptors (GPCRs) become desirable targets for developing multitarget-directed ligands (MTDLs) because of their crucial roles in the pathophysiology of various human diseases and the accessibility of druggable sites at the cell surface. Herein, we review the most recent advances in the development of GPCR-targeted MTDLs in treating complex diseases, and discuss their potential therapeutic strategies to reveal current trends and shed insights into the utility of GPCR-targeted MTDLs for future drug design and development.

Influence of solvent mixture on nucleophilicity parameters: the case of pyrrolidine in methanol-acetonitrile

The course of organic chemical reactions is efficiently modelled through the concepts of “electrophiles” and “nucleophiles” (meaning electron-seeking and nucleus-seeking reactive species). On the one hand, an advanced approach of the correlation of the nucleophilicity parameters N and electrophilicity E has been delivered from the linear free energy relationship log k (20 °C) = s(N + E). On the other hand, the general influence of the solvent mixtures, which are very often employed in preparative synthetic chemistry, has been poorly explored theoretically and experimentally, to date. Herein, we combined experimental and theoretical studies of the solvent influence on pyrrolidine nucleophilicity. We determined the nucleophilicity parameters N and s of pyrrolidine at 20 °C in CH₃OH/CH₃CN mixtures containing 0, 20, 40, 60, 80 and 100% CH₃CN by kinetic investigations of their nucleophilic substitution reactions to a series of 2-methoxy-3-X-5-nitrothiophenes 1a–e (X = NO₂, CN, COCH₃, CO₂CH₃, CONH₂). Depending on the resulting solvation medium, the N parameters range from 15.72 to 18.32 on the empirical nucleophilicity scale of Mayr. The nucleophilicity parameters N first evolve linearly with the content of acetonitrile up to 60% CH₃CN by volume, but is non linear for higher amounts. We designed a general computation protocol to investigate the solvent effect at the atomistic scale. The nucleophilicity in solvent mixtures was evaluated by combining classical molecular dynamic (MD) simulations of solvated pyrrolidine and a few density functional theory (DFT) calculations of Parr nucleophilicity. The pyrrolidine theoretical nucleophilicity 1/ω obtained in various CH₃OH/CH₃CN mixtures are in excellent agreement with Mayr's nucleophilicity (N) parameters measured. Analyses of the molecular dynamic trajectories reveal that the decrease of the nucleophilicity in methanol rich mixtures arises predominantly from the solvation of the pyrrolidine by methanol molecules through strong hydrogen bonds. Last, we proposed a simple model to predict and accurately reproduce the experimentally obtained nucleophilicity values.

Combined experiments and modelling rationalize the large influence of solvent composition on pyrrolidine nucleophilicity.