Design, synthesis and biological evaluation of 5-benzylidene-2-iminothiazolidin-4-ones as selective GSK-3β inhibitors

Design, synthesis, and biological evaluation of tetrahydropyrimidine analogue as GSK-3β/Aβ aggregation inhibitor and anti-Alzheimer's agent

The complex nature of Alzheimer's disease (AD) etiopathology is among the principal hurdles to developing effective anti-Alzheimer agents. Tau pathology and Amyloid-β (Aβ) accumulation are hallmarks and validated therapeutic strategies of AD. GSK-3β is a serine/threonine kinase involved in tau phosphorylation. Its excessive activity also contributes to the production of Aβ plaques, making GSK-3β an attractive AD target. Taking this into account, In this article, we outline the design, synthesis, and biological validation of a focused library of 1,2,3,4-tetrahydropyrimidine based derivatives as inhibitors of GSK-3β, tau phosphorylation, and Aβ accumulation. The inhibitory activity of forty nine synthetic compounds was tested against GSK-3β and other AD-relevant kinases. The kinetic experiments revealed the mode of GSK-3β inhibition by the most potent compound 44. The in- vitro drug metabolism and pharmacokinetic studies were thereafter performed. The anti-aggregation activity of the most potent GSK-3β inhibitor was tested using AD transgenic Caenorhabditis elegans (C. elegans) strain CL2006 for quantification of Aβ plaques and BR5706 C. elegans strain for tau pathology evaluation. We then evaluated the blood-brain barrier permeability and got promising results. Therefore, we present compound 44 as a potential ATP-competitive GSK-3β inhibitor with good metabolism and pharmacokinetic profile, anti-aggregation properties for amyloid beta protein, and reduction in tau-phosphorylation levels. We recommend more investigation into compound 44-based small molecules as possible targets for AD disease-modifying treatments.

Discovery of novel and highly potential inhibitors of glycogen synthase kinase 3-beta (GSK-3β) through structure-based pharmacophore modeling, virtual computational screening, docking and in silico ADMET analysis

The protein Glycogen Synthase Kinase 3-Beta (GSK-3β), is a promising therapeutic target for treating various diseases such as neurodegenerative disorders, diabetes, inflammation and cancer. This study aims to investigate the potential of compounds targeting inflammation or carbohydrate metabolism to selectively inhibit GSK3β by binding to its ATP site. To achieve this goal, we filtered a database of 49367 molecules involved in carbohydrate metabolism or targeting inflammation using various computational analyses, including pharmacophore modeling, molecular docking, dynamic simulation, prime MM-GBSA calculation, and in silico ADME studies. We generated a pharmacophore model (hypo S: AADDHRR) using two different crystallographic complexes of GSK3β and evaluated the model's performance in identifying hits using various parameters, including EF, GH, ROC, AUC and BEDROC. Subsequently, we performed various dockings (HTVS, SP, XP and IFD) for the retrieved hits and found that, 5 out of the top 10 ranked compounds had the scaffold of pyrazolidine 3,5-dione, which has never been reported to inhibit kinases. We also conducted ADMET studies to and concluded that compound N6 exhibited the best pharmacokinetic profile passing the blood-brain barrier, possessing high lipophilicity and a high coefficient of skin permeability in the intestines, along with good bioavailability and low toxicity risk assessment. Dynamic simulation were also performed indicating that compounds N6 derived from pyrazolidine 3,5-dione demonstrated better binding potential for GSK3β during the simulation period. Therefore, we propose that compounds derived from pyrazolidine-3,5-dione, which modulate the activity of lysosomal alpha-glucosidase could serve as a novel scaffold for the selective inhibition of GSK-3β.Communicated by Ramaswamy H. Sarma.

Impact of GSK-3β and CK-1δ on Wnt signaling pathway in alzheimer disease: A dual target approach

Alzheimer's disease (AD) is an enigmatic neurological illness that offers few treatment options. Recent exploration has highlighted the crucial connection of the Wnt signaling pathway in AD pathogenesis, shedding light on potential therapeutic targets. The present study focuses on the dual targeting of glycogen synthase kinase-3β (GSK-3β) and casein kinase-1δ (CK-1δ) within the framework of the Wnt signaling pathway as a possible technique for AD intervention. GSK-3β and CK-1δ are multifunctional kinases known for their roles in tau hyperphosphorylation, amyloid processing, and synaptic dysfunction, all of which are major hallmarks of Alzheimer's disease. They are intricately linked to Wnt signaling, which plays a pivotal part in sustaining neuronal function and synaptic plasticity. Dysregulation of the Wnt pathway in AD contributes to cognitive decline and neurodegeneration. This review delves into the molecular mechanisms by which GSK-3β and CK-1δ impact the Wnt signaling pathway, elucidating their roles in AD pathogenesis. We discuss the potential of small-molecule inhibitors along with their SAR studies along with the multi-targetd approach targeting GSK-3β and CK-1δ to modulate Wnt signaling and mitigate AD-related pathology. In summary, the dual targeting of GSK-3β and CK-1δ within the framework of the Wnt signaling pathway presents an innovative and promising avenue for future AD therapies, offering new hope for patients and caregivers in the quest to combat this challenging condition.

Discovery of novel quinolin-2-one derivatives as potential GSK-3β inhibitors for treatment of Alzheimer's disease: Pharmacophore-based design, preliminary SAR, in vitro and in vivo biological evaluation

Recently, glycogen synthase kinase-3β (GSK-3β) has been considered as a critical factor implicated in Alzheimer's disease (AD). In a previous work, a 3D pharmacophore model for GSK-3β inhibitors was created and the results suggested that derivative ZINC67773573, VIII, may provide a promising lead for developing novel GSK-3β inhibitors for the AD's treatment. Consequently, in this work, novel series of quinolin-2-one derivatives were synthesized and assessed for their GSK-3β inhibitory properties. In vitro screening identified three compounds: 7c, 7e and 7f as promising GSK-3β inhibitors. Compounds 7c, 7e and 7f were found to exhibit superior inhibitory effect on GSK-3β with IC50 value ranges between 4.68 ± 0.59 to 8.27 ± 0.60 nM compared to that of staurosporine (IC50 = 6.12 ± 0.74 nM). Considerably, compounds 7c, 7e and 7f effectively lowered tau hyperphosphorylated aggregates and proving their safety towards the SH-SY5Y and THLE2 normal cell lines. The most promising compound 7c alleviated cognitive impairments in the scopolamine-induced model in mice. Compound 7c's activity profile, while not highly selective, may provide a starting point and valuable insights into the design of multi-target inhibitors. According to the ADME prediction results, compounds 7c, 7e and 7f followed Lipinski's rule of five and could almost permeate through the BBB. Molecular docking simulations showed that these compounds are well accommodated in the ATP binding site interacting by its quinoline-2-one ring through hydrogen bonding with the key amino acids Asp133 and Val135 at the hinge region. The findings of this study suggested that these new compounds may have potential as anti-AD drugs targeting GSK-3β.

Synthesis and biological evaluation of thieno[3,2-c]pyrazol-3-amine derivatives as potent glycogen synthase kinase 3β inhibitors for Alzheimer's disease

Glycogen synthase kinase 3β (GSK-3β) is a potential target for anti-Alzheimer's disease (AD) drug development. In this study, a series of novel thieno[3,2-c]pyrazol-3-amine derivatives was synthesized and evaluated as potential GSK-3β inhibitors by structure-based drug design. The thieno[3,2-c]pyrazol-3-amine derivative 54 with a 4-methylpyrazole moiety which interacted with Arg141 by π-cation interaction was identified as a potent GSK-3β inhibitor with an IC50 of 3.4 nM and an acceptable kinase selectivity profile. In the rat primary cortical neurons, compound 54 showed neuroprotective effects on Aβ-induced neurotoxicity. Western blot analysis indicated that 54 inhibited GSK-3β by up-regulating the expression of phosphorylated GSK-3β at Ser9 and down-regulating the expression of phosphorylated GSK-3β at Tyr216. Meanwhile, 54 decreased tau phosphorylation at Ser396 in a dose-dependent way. In astrocytes and microglia cells, 54 inhibited the expression of inducible nitric oxide synthase (iNOS), indicating that 54 showed an anti-neuroinflammatory effect. In the AlCl3-induced zebrafish AD model, 54 significantly ameliorated the AlCl3-induced dyskinesia, demonstrating its anti-AD activity in vivo.

DNA-Compatible Synthesis of Thiazolidione Derivatives via Three-Component Annulation and Knoevenagel Condensation

Thiazolidione, conferring drug-like properties, is an important heterocycle that widely exists in medicinally relevant molecules. In this work, by efficiently assembling various DNA-tagged primary amines, abundant aryl isothiocyanates, and ethyl bromoacetate, we present a DNA-compatible three-component annulation to generate a 2-iminothiazolidin-4-one scaffold, which was further decorated via Knoevenagel condensation by employing (hetero)aryl and alkyl aldehydes. These thiazolidione derivatives should find broad use in focused DNA-encoded library construction.

GSK-3β Allosteric Inhibition: A Dead End or a New Pharmacological Frontier?

Most kinase inhibitors are designed to bind to highly homologous ATP-binding sites, which leads to promiscuity and possible off-target effects. Allostery is an alternative approach to pursuing selectivity. However, allostery is difficult to exploit due to the wide variety of underlying mechanisms and the potential involvement of long-range conformational effects that are difficult to pinpoint. GSK-3β is involved in several pathologies. This critical target has an ATP-binding site that is highly homologous with the orthosteric sites of other kinases. Unsurprisingly, there is also great similarity between the ATP-binding sites of GSK-3β and its isomer, which is not redundant and thus would benefit from selective inhibition. Allostery would also allow for a moderate and tunable inhibition, which is ideal for GSK-3β, because this target is involved in multiple pathways, some of which must be preserved. However, despite considerable research efforts, only one allosteric GSK-3β inhibitor has reached the clinic. Moreover, unlike other kinases, there are no X-ray structures of GSK-3β in complex with allosteric inhibitors in the PDB data bank. This review aims to summarize the state of the art in allosteric GSK-3β inhibitor investigations, highlighting the aspects that make this target challenging for an allosteric approach.

Synthesis of 2-iminothiazolidin-4-ones via copper-catalyzed [2 + 1 + 2] tandem annulation

In this paper, an efficient synthesis of 2-iminothiazolidin-4-ones through a copper-catalyzed tandem annulation reaction of alkyl amines, isothiocyanates and diazo acetates is presented. Notable advantages of this [2 + 1 + 2] cyclization methodology include readily accessible starting materials, simple operation, mild reaction conditions, high yields, step-economy and diverse functional group tolerance. In addition, the reaction is applicable to the gram scale synthesis and the preparation of bioactive molecules.

Design, Synthesis, Kinetic Analysis and Pharmacophore-Directed Discovery of 3-Ethylaniline Hybrid Imino-Thiazolidinone as Potential Inhibitor of Carbonic Anhydrase II: An Emerging Biological Target for Treatment of Cancer

Carbonic anhydrases (CA), having Zn2+ metal atoms, are responsible for the catalysis of CO2 and water to bicarbonate and protons. Any abnormality in the functioning of these enzymes may lead to morbidities such as glaucoma and different types of cancers including brain, renal and pancreatic carcinomas. To cope with the lack of presence of a promising therapeutic agent against these cancers, searching for an efficient and suitable carbonic anhydrase inhibitor is crucial. In the current study, ten novel 3-ethylaniline hybrid imino-thiazolidinones were synthesized and characterized by FTIR, NMR (1H, 13C), and mass spectrometry. Synthesis was carried out by diethyl but-2-ynedioate cyclization and different acyl thiourea substitutions of 3-ethyl amine. The CA (II) enzyme inhibition profile for all synthesized derivatives was determined. It was observed that compound 6e demonstrated highest inhibition of CA-II with an IC50 value of 1.545 ± 0.016 µM. In order to explore the pharmacophoric properties and develop structure activity relationship, in silico screening was performed. In silico investigations included density functional theory (DFT) studies, pharmacophore-guided model development, molecular docking, molecular dynamic (MD) simulations, and prediction of drug likeness scores. DFT investigations provided insight into the electronic characteristics of compounds, while molecular docking determined the binding orientation of derivatives within the CA-II active site. Compounds 6a, 6e, and 6g had a reactive profile and generated stable protein-ligand interactions with respective docking scores of -6.12, -6.99, and -6.76 kcal/mol. MD simulations were used to evaluate the stability of the top-ranked complex. In addition, pharmacophore-guided modeling demonstrated that compound 6e produced the best pharmacophore model (HHAAARR) compared to standard brinzolamide. In vitro and in silico investigations anticipated that compound 6e would be an inhibitor of carbonic anhydrase II with high efficacy. Compound 6e may serve as a potential lead for future synthesis that can be investigated at the molecular level, and additional in vivo studies are strongly encouraged.

Discovery of Azaindolin-2-One as a Dual Inhibitor of GSK3β and Tau Aggregation with Potential Neuroprotective Activity

The inhibition of glycogen synthase kinase 3β (GSK3β) activity through pharmacological intervention represents a promising approach for treating challenging neurodegenerative disorders like Alzheimer’s disease. Similarly, abnormal tau aggregate accumulation in neurons is a hallmark of various neurodegenerative diseases. We introduced new dual GSK3β/tau aggregation inhibitors due to the excellent clinical outcome of multitarget drugs. Compound (E)-2f stands out among the synthesized inhibitors as a promising GSK3β inhibitor (IC₅₀ 1.7 µM) with a pronounced tau anti-aggregation effect in a cell-based model of tauopathy. Concurrently, (E)-2f was demonstrated to be non-toxic to normal cells, making it a promising neuroprotective lead compound that needs further investigation.

Sukkari dates seed improves type-2 diabetes mellitus-induced memory impairment by reducing blood glucose levels and enhancing brain cholinergic transmission: In vivo and molecular modeling studies

Cognitive decline is one of the serious complications associated with diabetes mellitus (T2DM) of type-2. In this reported work, the effect of aqueous sukkari dates seed extract (ASSE) was evaluated in T2DM-induced rats. T2DM was induced using intraperitoneal injection of nicotinamide and streptozocin (STZ) administration. The diabetic rats were then treated orally with 200 mg/kg and 400 mg/kg of dates seed extract for 30 days and results were compared with metformin-treated groups. The memory functions were assessed using three maze models. Glucose and insulin levels in the blood and acetylcholine, acetylcholinesterase brain homogenates were estimated. The results showed a significant reduction in transfer latency (TL) (p < 0.001) during the elevated plus maze (EPM) test. The novel object recognition (NOR) test revealed a longer exploration time (p > 0.05) with novel objects and a higher discrimination index (p > 0.05). The Y-maze test also showed a significant increase in the number of entries to the novel arm (p > 0.05) and the total number of entries in the trial (p > 0.01) as well as in test (p > 0.05) sessions. Reduction in blood glucose (p > 0.05) and improvement in blood insulin (p > 0.05) levels were also noted. Improvement in ACh levels (p > 0.001) with 400 mg/kg of ASSE and reduction in AChE (p > 0.001) with both doses of ASSE were also observed in the brain homogenates. The results of ASSE were found comparable with the metformin-treated rats. The estimation of phytochemical constituents displayed a significant presence of phenolic content. Further, molecular modeling studies showed ellagic acid, catechin, and epicatechin as the potential molecule interacting with GSK-3β, α-amylase, and AChE and may be responsible for observed bioactivity. In conclusion, ASSE has the ability to alleviate T2DM-related cognitive impairments.

Glycogen Synthase Kinase-3 Inhibitors: Preclinical and Clinical Focus on CNS-A Decade Onward

The protein kinase, GSK-3, participates in diverse biological processes and is now recognized a promising drug discovery target in treating multiple pathological conditions. Over the last decade, a range of newly developed GSK-3 inhibitors of diverse chemotypes and inhibition modes has been developed. Even more conspicuous is the dramatic increase in the indications that were tested from mood and behavior disorders, autism and cognitive disabilities, to neurodegeneration, brain injury and pain. Indeed, clinical and pre-clinical studies were largely expanded uncovering new mechanisms and novel insights into the contribution of GSK-3 to neurodegeneration and central nerve system (CNS)-related disorders. In this review we summarize new developments in the field and describe the use of GSK-3 inhibitors in the variety of CNS disorders. This remarkable volume of information being generated undoubtedly reflects the great interest, as well as the intense hope, in developing potent and safe GSK-3 inhibitors in clinical practice.

Discovery of thiazolidin-4-one analogue as selective GSK-3β inhibitor through structure based virtual screening

GSK-3β directly phosphorylate tubulin binding site of tau protein, indicating its importance in tau aggregation and, therefore, in Alzheimer's disease pathology. New GSK-3β inhibitors were identified using a structure-based screening, ADMET analysis. These studies revealed that ZINC09036109, ZINC72371723, ZINC72371725, and ZINC01373165 approached optimal ADMET properties along with good MM-GBSA dG binding. Protein kinase assays of these compounds against eight disease-relevant kinases were performed. During disease-relevant kinase profiling, ZINC09036109 ((E)-2-((3,4-dimethylphenyl)imino)-5-(3-methoxy-4-(naphthalen-2-ylmethoxy)benzyl)thiazolidin-4-one) emerged as a selective GSK-3β inhibitor with more than 10-fold selectivity over other disease-relevant kinases. Molecular dynamics study of ZINC09036109 molecule revealed interactions with Ile62, Phe67, Val135, Leu188, Asp200 amino acid residues of the binding site of GSK-3β, which were highly comparable to the co-crystallized molecule and hence validating comparative better activity of this compound compared to overall screened molecules.

Glycogen Synthase Kinase 3β: A New Gold Rush in Anti-Alzheimer's Disease Multitarget Drug Discovery?

Alzheimer’s disease (AD), like other multifactorial diseases, is the result of a systemic breakdown of different physiological networks. As result, several lines of evidence suggest that it could be more efficiently tackled by molecules directed toward different dysregulated biochemical targets or pathways. In this context, the selection of targets to which the new molecules will be directed is crucial. For years, the design of such multitarget-directed ligands (MTDLs) has been based on the selection of main targets involved in the “cholinergic” and the “β-amyloid” hypothesis. Recently, there have been some reports on MTDLs targeting the glycogen synthase kinase 3β (GSK-3β) enzyme, due to its appealing properties. Indeed, this enzyme is involved in tau hyperphosphorylation, controls a multitude of CNS-specific signaling pathways, and establishes strict connections with several factors implicated in AD pathogenesis. In the present Miniperspective, we will discuss the reasons behind the development of GSK-3β-directed MTDLs and highlight some of the recent efforts to obtain these new classes of MTDLs as potential disease-modifying agents.

Design, synthesis, and anticancer activity of novel 4-thiazolidinone-phenylaminopyrimidine hybrids

4-Thiazolidinones and phenylaminopyrimidines are known as anticancer agents. Imatinib is the pioneer phenylaminopyrimidine derivative kinase inhibitor, which is used for the treatment of chronic myeloid leukemia. With a hybrid approach, a novel series of 5-benzylidene-2-arylimino-4-thiazolidinone derivatives containing phenylaminopyrimidine core were designed, synthesized, and tested for their anticancer activity on K562 (chronic myeloid leukemia), PC3 (prostat cancer), and SHSY-5Y (neuroblastoma) cells. Since superior anticancer activity was observed on K562 cells, further biological studies of selected compounds (8, 15, and 34) were performed on K562 cells. For the synthesis of designed compounds, thiourea compounds were converted to 2-imino-1,3-thiazolidin-4-ones with α-chloroacetic acid in the presence of sodium acetate. 5-Benzylidene-2-imino-1,3-thiazolidin-4-one derivatives were obtained by Knoevenagel condensation of 2-imino-1,3-thiazolidin-4-ones with related aldehydes. Compounds 8, 15, and 34 were evaluated for cell viability, apoptosis studies, cell cycle experiments, and DNA damage assays. IC₅₀ values of compounds 8, 15, and 34 were found as 5.26 ± 1.03, 3.52 ± 0.91, and 8.16 ± 1.27 μM, respectively, in K562 cells. Preferably, these compounds showed less toxicity towards L929 cells compared to imatinib. Furthermore, compounds 8 and 15 significantly induced early and late apoptosis in a time-dependent manner. Compounds 15 and 34 induced cell cycle arrest at G0/G1 phase and compound 8 caused cell cycle arrest at G2/M phase. Based on DNA damage assay, compounds 8 and 15 were found to be more genotoxic than imatinib towards K562 cells. To put more molecular insight, possible Abl inhibition mechanisms of most active compounds were predicted by molecular docking studies. In conclusion, a novel series of 5-benzylidene-2-arylimino-4-thiazolidinone derivatives and their promising anticancer activities were reported herein.

Rational Design of Multitarget-Directed Ligands: Strategies and Emerging Paradigms

Due to the complexity of multifactorial diseases, single-target drugs do not always exhibit satisfactory efficacy. Recently, increasing evidence indicates that simultaneous modulation of multiple targets may improve both therapeutic safety and efficacy, compared with single-target drugs. However, few multitarget drugs are on market or in clinical trials, despite the best efforts of medicinal chemists. This article discusses the systematic establishment of target combination, lead generation, and optimization of multitarget-directed ligands (MTDLs). Moreover, we analyze some MTDLs research cases for several complex diseases in recent years and the physicochemical properties of 117 clinical multitarget drugs, with the aim to reveal the trends and insights of the potential use of MTDLs.

Discovery of novel glycogen synthase kinase-3α inhibitors: Structure-based virtual screening, preliminary SAR and biological evaluation for treatment of acute myeloid leukemia

Glycogen synthase kinase 3α (GSK-3α) plays a constitutive role in various physiological processes and has been proved to be a therapeutic target for acute myeloid leukemia (AML). In this paper, by means of computer-aided drug design, we discovered a novel chemical series of GSK-3α inhibitors with an IC₅₀ value of 0.033-2.804 μM. The preliminary structure-activity relationship was concluded and, notably, the most potent and isoform-selective compound G28_14 was identified with IC₅₀ values of 33 nM and 218 nM against GSK-3α and -3β, respectively, exhibiting a nearly ten-fold isoform-selectivity. Further cell viability assays and colony formation assays revealed that G28_14 suppressed cell survival by impairing cell proliferation by up to 90% in two AML cell lines. Moreover, surface marker expression analysis demonstrated that G28_14 induced terminal differentiation with a high level of CD11b, CD11c, and CD14. Western immunoblotting showed that G28_14 isoform-selectively inhibited the phosphorylation of GSK-3α in-cell without activating Wnt/β-catenin signaling. In addition, to elucidate its structure-activity relationship, the binding mode of this chemical series was proposed using molecular docking and molecular dynamics simulations. Taken together, this chemical series is worth developing as differentiation therapies for the treatment of AML.

Structure-activity relationship (SAR) studies of synthetic glycogen synthase kinase-3β inhibitors: A critical review

Glycogen Synthase Kinase-3 (GSK-3) is a constitutively dynamic, omnipresent serine/threonine protein kinase regularly called as a "multitasking kinase" due to its pliable function in diverse signaling pathways. It exists in two isoforms i.e., GSK-3α and GSK-3β. Inhibition of GSK-3 may be useful in curing various diseases such as Alzheimer's disease, type II diabetes, mood disorders, cancers, chronic inflammatory agents, stroke, bipolar disorders and so on, but the approach poses significant challenges. Lithium was the first GSK-3β inhibitor to be used for therapeutic outcome and has been effectively used for many years. In recent years, a large number of structurally diverse potent GSK-3β inhibitors are reported. The present review focuses on the recent developments in the area of medicinal chemistry to explore the diverse chemical structures of potent GSK-3β inhibitors and also describes its structure-activity relationships (SAR) and molecular binding interactions of favorable applicability in various diseases.

Umpolung cyclization reaction of N-cinnamoylthioureas in the presence of DBU

A novel regioselective cyclization reaction of N-cinnamoylthioureas leading to six- or five-membered heterocyclic compounds was developed. N-Cinnamoylthioureas in the presence of trifluoroacetic acid (TFA) underwent the well-established intramolecular cycloaddition reaction to give 2-imino-2,3,5,6-tetrahydro-4H-1,3-thiazin-4-ones in good yields. On the other hand, the reaction with 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU) proceeded in an unprecedented "umpolung" cyclization fashion to afford five-membered 2-imino-1,3-thiazolidin-4-ones and/or 2-thioxoimidazolidine-4-ones. The reaction was considered to occur via a cycloadduct of DBU with the cinnamoyl moiety followed by intramolecular attack of the thiourea group.

Glycogen synthase kinase-3 and its inhibitors: Potential target for various therapeutic conditions

Glycogen Synthase Kinase-3 (GSK-3) is a serine/threonine kinase which is ubiquitously expressed and is regarded as a regulator for various cellular events and signalling pathways. It exists in two isoforms, GSK-3α and GSK-3β and can phosphorylate a wide range of substrates. Aberrancy in the GSK-3 activity can lead to various diseases like Alzheimer's, diabetes, cancer, neurodegeneration etc., rendering it an attractive target to develop potent and specific inhibitors. The present review focuses on the recent developments in the area of GSK-3 inhibitors and also enlightens its therapeutic applicability in various disease conditions.

Oxazolo[4,5-b]pyridine-Based Piperazinamides as GSK-3β Inhibitors with Potential for Attenuating Inflammation and Suppression of Pro-Inflammatory Mediators

Recent studies reveal that glycogen synthase kinase-3β (GSK-3β) acts as a pro-inflammatory enzyme, and by inhibiting this kinase, inflammation can be controlled. In this regard, a series of 17 piperazine-linked oxazolo[4,5-b]pyridine-based derivatives was synthesized and evaluated for in vitro GSK-3β inhibitory and in vivo anti-inflammatory activity. The compounds 7d, 7e, 7g, and 7c displayed the best GSK-3β inhibitory activity among all the synthesized compounds, with corresponding IC₅₀ values of 0.34, 0.39, 0.47, and 0.53 µM. Among the compounds 7d, 7e, 7g, and 7c examined for in vivo anti-inflammatory activity in the rat paw edema model, compound 7d exhibited maximum inhibition, reducing the paw volume by 62.79 and 65.91% at 3 and 5 h post-carrageenan administration, respectively, in comparison to indomethacin (76.74% at 3 h and 79.54% at 5 h after carrageenan administration). Furthermore, these compounds (7d, 7e, 7g, and 7c) were also found to substantially inhibit pro-inflammatory mediators, i.e., TNF-α, IL-1β, and IL-6, ex vivo in comparison to indomethacin and did not pose any gastric ulceration risk, indicating the potential of this oxazolopyridine scaffold for the development of GSK-3β inhibitors and their application as anti-inflammatory agents.

(Z)-2-(3-Chlorobenzylidene)-3,4-dihydro-N-(2-methoxyethyl)-3-oxo-2H-benzo[b][1,4]oxazine-6-carboxamide as GSK-3β inhibitor: Identification by virtual screening and its validation in enzyme- and cell-based assay

Glycogen synthase kinase 3β (GSK-3β) is a widely investigated molecular target for numerous diseases including Alzheimer's disease, cancer, and diabetes mellitus. The present study was aimed to discover new scaffolds for GSK-3β inhibition, through protein structure-guided virtual screening approach. With the availability of large number of GSK-3β crystal structures with varying degree of RMSD in protein backbone and RMSF in side chain geometry, herein appropriate crystal structures were selected based on the characteristic ROC curve and percentage enrichment of actives. The validated docking protocol was employed to screen a library of 50,000 small molecules using molecular docking and binding affinity calculations. Based on the GLIDE docking score, Prime MMGB/SA binding affinity, and interaction pattern analysis, the top 50 ligands were selected for GSK-3β inhibition. (Z)-2-(3-chlorobenzylidene)-3,4-dihydro-N-(2-methoxyethyl)-3-oxo-2H-benzo[b][1,4]oxazine-6-carboxamide (F389-0663, 7) was identified as a potent inhibitor of GSK-3β with an IC₅₀ value of 1.6 μm. Further, GSK-3β inhibition activity was then investigated in cell-based assay. The treatment of neuroblastoma N2a cells with 12.5 μm of F389-0663 resulted in the significant increase in GSK-3β Ser9 levels, which is indicative of the GSK-3β inhibitory activity of a compound. The molecular dynamic simulations were carried out to understand the interactions of F389-0663 with GSK-3β protein.