Structural features underlying the selectivity of the kinase inhibitors NBC and dNBC: role of a nitro group that discriminates between CK2 and DYRK1A

2-(Phenylamino)-7,8-dihydroquinazolin-5(6H)-one, a promising scaffold for MAO-B inhibitors with potential GSK3β targeting

Neurodegenerative disorders, such as Parkinson's disease and Alzheimer's disease, constitute pathological conditions of great relevance on health span and quality of life. The identification of novel therapeutic options, able to modulate the processes involved in the insurgence and progression of neurodegenerative disorders, represents an intriguing challenge of current research. Herein, a library of 36-membered 2-(phenylamino)-7,8-dihydroquinazolinone derivatives was synthesized and biologically evaluated as human MAO inhibitors. Some compounds able to inhibit MAO-B potently and selectively (Ki in the nanomolar range) were identified, and robust structure-activity relationships were drawn, supported by computational studies. Further biological assays revealed a safe profile for all derivatives and, for compounds selected as the best MAO-B inhibitors (4, 5, 13, 14) the following properties also emerged: (i) the ability to inhibit MAO-B activity in whole cells, with an effectiveness comparable or slight lower with respect to the reference safinamide; (ii) physicochemical parameters suggesting drug-likeness properties; (iii) the ability to inhibit, albeit weakly, GSK3β kinase (for compound 4). Within the whole series, compound 4 stood out as a promising lead for future optimization campaigns aimed to obtain useful drugs for the treatment of Alzheimer's and Parkinson's diseases.

Strategies of Targeting CK2 in Drug Discovery: Challenges, Opportunities, and Emerging Prospects

CK2 (casein kinase 2) is a serine/threonine protein kinase that is ubiquitous in eukaryotic cells and plays important roles in a variety of cellular functions, including cell growth, apoptosis, circadian rhythms, DNA damage repair, transcription, and translation. CK2 is involved in cancer pathogenesis and the occurrence of many diseases. Therefore, targeting CK2 is a promising therapeutic strategy. Although many CK2-specific small-molecule inhibitors have been developed, only CX-4945 has progressed to clinical trials. In recent years, novel CK2 inhibitors have gradually become a research hotspot, which is expected to overcome the limitations of traditional inhibitors. Herein, we summarize the structure, biological functions, and disease relevance of CK2 and emphatically analyze the structure-activity relationship (SAR) and binding modes of small-molecule CK2 inhibitors. We also discuss the latest progress of novel strategies, providing insights into new drugs targeting CK2 for clinical practice.

Novel and Potential Small Molecule Scaffolds as DYRK1A Inhibitors by Integrated Molecular Docking-Based Virtual Screening and Dynamics Simulation Study

The dual-specificity tyrosine phosphorylation-regulated kinase 1A (DYRK1A) is a novel, promising and emerging biological target for therapeutic intervention in neurodegenerative diseases, especially in Alzheimer's disease (AD). The molMall database, comprising rare, diverse and unique compounds, was explored for molecular docking-based virtual screening against the DYRK1A protein, in order to find out potential inhibitors. Ligands exhibiting hydrogen bond interactions with key amino acid residues such as Ile165, Lys188 (catalytic), Glu239 (gk+1), Leu241 (gk+3), Ser242, Asn244, and Asp307, of the target protein, were considered potential ligands. Hydrogen bond interactions with Leu241 (gk+3) were considered key determinants for the selection. High scoring structures were also docked by Glide XP docking in the active sites of twelve DYRK1A related protein kinases, viz. DYRK1B, DYRK2, CDK5/p25, CK1, CLK1, CLK3, GSK3β, MAPK2, MAPK10, PIM1, PKA, and PKCα, in order to find selective DYRK1A inhibitors. MM/GBSA binding free energies of selected ligand-protein complexes were also calculated in order to remove false positive hits. Physicochemical and pharmacokinetic properties of the selected six hit ligands were also computed and related with the proposed limits for orally active CNS drugs. The computational toxicity webserver ProTox-II was used to predict the toxicity profile of selected six hits (molmall IDs 9539, 11352, 15938, 19037, 21830 and 21878). The selected six docked ligand-protein systems were exposed to 100 ns molecular dynamics (MD) simulations to validate their mechanism of interactions and stability in the ATP pocket of human DYRK1A kinase. All six ligands were found to be stable in the ATP binding pocket of DYRK1A kinase.

Molecules against Covid-19: An in silico approach for drug development

A large number of deaths have been caused by the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) worldwide, turning it into a serious and momentous threat to public health. This study tends to contribute to the development of effective treatment strategies through a computational approach, investigating the mechanisms in relation to the binding and subsequent inhibition of SARS-CoV-2 ribonucleic acid (RNA)-dependent RNA polymerase (RdRp). Molecular docking was performed to screen six naturally occurring molecules with antineoplastic properties (Ellipticine, Ecteinascidin, Homoharringtonine, Dolastatin 10, Halichondrin, and Plicamycin). Absorption, distribution, metabolism, and excretion (ADME) investigation was also conducted to analyze the drug-like properties of these compounds. The docked results have clearly shown binding of ligands to the SARS-CoV-2 RdRp protein. Interestingly, all ligands were found to obey Lipinski’s rule of five. These results provide a basis for repurposing and using molecules, derived from plants and animals, as a potential treatment for the coronavirus disease 2019 (COVID-19) infection as they could be effective therapeutics for the same.

Small Molecule Inhibitors of DYRK1A Identified by Computational and Experimental Approaches

Dual-specificity tyrosine phosphorylation-regulated kinase 1A (DYRK1A) is a protein kinase with diverse functions in cell regulation. Abnormal expression and activity of DYRK1A contribute to numerous human malignancies, Down syndrome, and Alzheimer's disease. Notably, DYRK1A has been proposed as a potential therapeutic target for the treatment of diabetes because of its key role in pancreatic β-cell proliferation. Consequently, DYRK1A is an attractive drug target for a variety of diseases. Here, we report the identification of several DYRK1A inhibitors using our in-house topological water network-based approach. All inhibitors were further verified by in vitro assay.

A Dual Inhibitor of DYRK1A and GSK3β for β-Cell Proliferation: Aminopyrazine Derivative GNF4877

Loss of β-cell mass and function can lead to insufficient insulin levels and ultimately to hyperglycemia and diabetes mellitus. The mainstream treatment approach involves regulation of insulin levels; however, approaches intended to increase β-cell mass are less developed. Promoting β-cell proliferation with low-molecular-weight inhibitors of dual-specificity tyrosine-regulated kinase 1A (DYRK1A) offers the potential to treat diabetes with oral therapies by restoring β-cell mass, insulin content and glycemic control. GNF4877, a potent dual inhibitor of DYRK1A and glycogen synthase kinase 3β (GSK3β) was previously reported to induce primary human β-cell proliferation in vitro and in vivo. Herein, we describe the lead optimization that lead to the identification of GNF4877 from an aminopyrazine hit identified in a phenotypic high-throughput screening campaign measuring β-cell proliferation.

Structure-Activity Relationships and Biological Evaluation of 7-Substituted Harmine Analogs for Human β-Cell Proliferation

Recently, we have shown that harmine induces β-cell proliferation both in vitro and in vivo, mediated via the DYRK1A-NFAT pathway. We explore structure-activity relationships of the 7-position of harmine for both DYRK1A kinase inhibition and β-cell proliferation based on our related previous structure-activity relationship studies of harmine in the context of diabetes and β-cell specific targeting strategies. 33 harmine analogs of the 7-position substituent were synthesized and evaluated for biological activity. Two novel inhibitors were identified which showed DYRK1A inhibition and human β-cell proliferation capability. The DYRK1A inhibitor, compound 1-2b, induced β-cell proliferation half that of harmine at three times higher concentration. From these studies we can draw the inference that 7-position modification is limited for further harmine optimization focused on β-cell proliferation and cell-specific targeting approach for diabetes therapeutics.

Synthesis and Biological Validation of a Harmine-Based, Central Nervous System (CNS)-Avoidant, Selective, Human β-Cell Regenerative Dual-Specificity Tyrosine Phosphorylation-Regulated Kinase A (DYRK1A) Inhibitor

Recently, our group identified that harmine is able to induce β-cell proliferation both in vitro and in vivo, mediated via the DYRK1A-NFAT pathway. Since, harmine suffers from a lack of selectivity, both against other kinases and CNS off-targets, we therefore sought to expand structure-activity relationships for harmine's DYRK1A activity, to enhance selectivity for off-targets while retaining human β-cell proliferation activity. We carried out optimization of the 9-N-position of harmine to synthesize 29 harmine-based analogs. Several novel inhibitors showed excellent DYRK1A inhibition and human β-cell proliferation capability. An optimized DYRK1A inhibitor, 2-2c, was identified as a novel, efficacious in vivo lead candidate. 2-2c also demonstrates improved selectivity for kinases and CNS off-targets, as well as in vivo efficacy for β-cell proliferation and regeneration at lower doses than harmine. Collectively, these findings demonstrate that 2-2c is a much improved in vivo lead candidate as compared to harmine for the treatment of diabetes.

Selective DYRK1A Inhibitor for the Treatment of Type 1 Diabetes: Discovery of 6-Azaindole Derivative GNF2133

Autoimmune deficiency and destruction in either β-cell mass or function can cause insufficient insulin levels and, as a result, hyperglycemia and diabetes. Thus, promoting β-cell proliferation could be one approach toward diabetes intervention. In this report we describe the discovery of a potent and selective DYRK1A inhibitor GNF2133, which was identified through optimization of a 6-azaindole screening hit. In vitro, GNF2133 is able to proliferate both rodent and human β-cells. In vivo, GNF2133 demonstrated significant dose-dependent glucose disposal capacity and insulin secretion in response to glucose-potentiated arginine-induced insulin secretion (GPAIS) challenge in rat insulin promoter and diphtheria toxin A (RIP-DTA) mice. The work described here provides new avenues to disease altering therapeutic interventions in the treatment of type 1 diabetes (T1D).

Dual-Specificity Tyrosine Phosphorylation-Regulated Kinase 1A (DYRK1A) Inhibitors as Potential Therapeutics

Dual-specificity tyrosine phosphorylation-regulated kinase 1A (DYRK1A) is a member of an evolutionarily conserved family of protein kinases that belongs to the CMGC group of kinases. DYRK1A, encoded by a gene located in the human chromosome 21q22.2 region, has attracted attention due to its association with both neuropathological phenotypes and cancer susceptibility in patients with Down syndrome (DS). Inhibition of DYRK1A attenuates cognitive dysfunctions in animal models for both DS and Alzheimer's disease (AD). Furthermore, DYRK1A has been studied as a potential cancer therapeutic target because of its role in the regulation of cell cycle progression by affecting both tumor suppressors and oncogenes. Consequently, selective synthetic inhibitors have been developed to determine the role of DYRK1A in various human diseases. Our perspective includes a comprehensive review of potent and selective DYRK1A inhibitors and their forthcoming therapeutic applications.

DYRK1A kinase inhibition with emphasis on neurodegeneration: A comprehensive evolution story-cum-perspective

Alzheimer, the fourth leading cause of death embodies a key responsible event including formation of β-amyloid protein clustering to amyloid plaque on blood vessels. The origin of above events is Amyloid precursor protein (APP) which is an integral membrane protein known for its function in synapses formation. Modern research had proposed that the over expression of DYRK1A (Dual specificity tyrosine phosphorylation regulated kinase1A, a family of protein kinases, positioned within the Down's syndrome critical region (DSCR) on human chromosome 21causes phosphorylation of APP protein resulting in its cleavage to Aβ 40, 42 and tau proteins (regulated by beta and gamma secretase) which plays critical role in early onset of Alzheimer's disease (AD) detected in Down's syndrome (DS), leading to permanent functional and structural deformities which results ultimately into neuro-degeneration and neuronal death. Therefore, DYRK1A emerges as a potential target for prevention of neuro-degeneration and hence Alzheimer. Presently, the treatment methods for Down's syndrome, as well as Alzheimer's disease are extremely biased and represent a major deficiency for therapeutic necessities. We hereby, focus our review on the current status of the research and contributions in the development of DYRK1A inhibitors.

Development of Kinase-Selective, Harmine-Based DYRK1A Inhibitors that Induce Pancreatic Human β-Cell Proliferation

DYRK1A has been implicated as an important drug target in various therapeutic areas, including neurological disorders and oncology. DYRK1A has more recently been shown to be involved in pathways regulating human β-cell proliferation, thus making it a potential therapeutic target for both Type 1 and Type 2 diabetes. Our group, using a high-throughput phenotypic screen, identified harmine that is able to induce β-cell proliferation both in vitro and in vivo. Since harmine has suboptimal kinase selectivity, we sought to expand structure-activity relationships for harmine's DYRK1A activity, to enhance selectivity, while retaining human β-cell proliferation capability. We carried out the optimization of the 1-position of harmine and synthesized 15 harmine analogues. Six compounds showed excellent DYRK1A inhibition with IC50 in the range of 49.5-264 nM. Two compounds, 2-2 and 2-8, exhibited excellent human β-cell proliferation at doses of 3-30 μM, and compound 2-2 showed improved kinase selectivity as compared to harmine.

Novel selective thiadiazine DYRK1A inhibitor lead scaffold with human pancreatic β-cell proliferation activity

The Dual-Specificity Tyrosine Phosphorylation-Regulated Kinase 1A (DYRK1A) is an enzyme that has been implicated as an important drug target in various therapeutic areas, including neurological disorders (Down syndrome, Alzheimer's disease), oncology, and diabetes (pancreatic β-cell expansion). Current small molecule DYRK1A inhibitors are ATP-competitive inhibitors that bind to the kinase in an active conformation. As a result, these inhibitors are promiscuous, resulting in pharmacological side effects that limit their therapeutic applications. None are in clinical trials at this time. In order to identify a new DYRK1A inhibitor scaffold, we constructed a homology model of DYRK1A in an inactive, DFG-out conformation. Virtual screening of 2.2 million lead-like compounds from the ZINC database, followed by in vitro testing of selected 68 compounds revealed 8 hits representing 5 different chemical classes. We chose to focus on one of the hits from the computational screen, thiadiazine 1 which was found to inhibit DYRK1A with IC50 of 9.41 μM (Kd = 7.3 μM). Optimization of the hit compound 1, using structure-activity relationship (SAR) analysis and in vitro testing led to the identification of potent thiadiazine analogs with significantly improved binding as compared to the initial hit (Kd = 71-185 nM). Compound 3-5 induced human β-cell proliferation at 5 μM while showing selectivity for DYRK1A over DYRK1B and DYRK2 at 10 μM. This newly developed DYRK1A inhibitor scaffold with unique kinase selectivity profiles has potential to be further optimized as novel therapeutics for diabetes.

Multi-step virtual screening to develop selective DYRK1A inhibitors

Developing selective inhibitors for a particular kinase remains a major challenge in kinase-targeted drug discovery. Here we performed a multi-step virtual screening for dual-specificity tyrosine-phosphorylation-regulated kinase 1A (DYRK1A) inhibitors by focusing on the selectivity for DYRK1A over cyclin-dependent kinase 5 (CDK5). To examine the key factors contributing to the selectivity, we constructed logistic regression models to discriminate between actives and inactives for DYRK1A and CDK5, respectively, using residue-based binding free energies. The residue-based parameters were calculated by molecular mechanics-generalized Born surface area (MM-GBSA) decomposition methods for kinase-ligand complexes modeled by computer ligand docking. Based on the findings from the logistic regression models, we built a three-dimensional (3D) pharmacophore model and chose filter criteria for the multi-step virtual screening. The virtual hit compounds obtained from the screening were assessed for their inhibitory activities against DYRK1A and CDK5 by in vitro assay. Our screening identified two novel selective DYRK1A inhibitors with IC50 values of several μM for DYRK1A and >100μM for CDK5, which can be further optimized to develop more potent selective DYRK1A inhibitors.

DYRK1A inhibition as potential treatment for Alzheimer's disease

In total, 47,500,000 people worldwide are affected by dementia and this number is estimated to double by 2030 and triple within 2050 resulting in a huge burden on public health. Alzheimer's disease (AD), a progressive neurodegenerative disorder, is the most common cause of dementia, accounting for 60-70% of all the cases. The cause of AD is still poorly understood but several brain abnormalities (e.g., loss of neuronal connections and neuronal death) have been identified in affected patients. In addition to the accumulation of β-amyloid plaques in the brain tissue, aberrant phosphorylation of tau proteins has proved to increase neuronal death. DYRK1A phosphorylates tau on 11 different Ser/Thr residues, resulting in the formation of aggregates called 'neurofibrillary tangles' which, together with amyloid plaques, could be responsible for dementia, neuronal degeneration and cell death. Small molecule inhibition of DYRK1A could thus represent an interesting approach toward the treatment of Alzheimer's and other neurodegenerative diseases. Herein we review the current progress in the identification and development of DYRK1A inhibitors.

Casein kinases as potential therapeutic targets

INTRODUCTION

The conventional term 'casein kinase' (CK) denotes three classes of kinases - CK1, CK2 and Golgi-CK (G-CK)/Fam20C (family with sequence similarity 20, member C) - sharing the ability to phoshorylate casein in vitro, but otherwise unrelated to each other. All CKs have been reported to be implicated in human diseases, and reviews individually dealing with the druggability of CK1 and CK2 are available. Our aim is to provide a comparative analysis of the three classes of CKs as therapeutic targets.

AREAS COVERED

CK2 is the CK for which implication in neoplasia is best documented, with the survival of cancer cells often relying on its overexpression. An ample variety of cell-permeable CK2 inhibitors have been developed, with a couple of these now in clinical trials. Isoform-specific CK1 inhibitors that are expected to play a beneficial role in oncology and neurodegeneration have been also developed. In contrast, the pathogenic potential of G-CK/Fam20C is caused by its loss of function. Activators of Fam20C, notably sphingolipids and their analogs, may prove beneficial in this respect.

EXPERT OPINION

Optimization of CK2 and CK1 inhibitors will prove useful to develop new therapeutic strategies for treating cancer and neurodegenerative disorders, while the design of potent activators of G-CK/Fam20C will provide a new tool in the fields of bio-mineralization and hypophosphatemic diseases.

The Selectivity of CK2 Inhibitor Quinalizarin: A Reevaluation

Many polyphenolic compounds have been reported to inhibit protein kinases, with special reference to CK2, a pleiotropic serine/threonine kinase, implicated in neoplasia, neurodegenerative disease, and viral infections. In general however these compounds are not endowed with stringent selectivity. Among them quinalizarin (1,2,5,8-tetrahydroxyanthraquinone) turned out to be particularly potent (Ki = 0.058 μM) and quite selective as judged by profiling it on a small panel of 70 protein kinases. Here, by profiling quinalizarin on a larger panel of 140 kinases we reach the conclusion that quinalizarin is one of the most selective inhibitors of CK2, superior to the first-in-class CK2 inhibitor, CX-4945, now in clinical trials for the treatment of cancer. Moreover here we show that quinalizarin is able to discriminate between the isolated CK2 catalytic subunit (CK2α) and CK2 holoenzyme (CK2α2 β2), consistent with in silico and in vitro analyses.

Design, validation and efficacy of bisubstrate inhibitors specifically affecting ecto-CK2 kinase activity

By derivatizing the purely competitive CK2 inhibitor N1-(4,5,6,7-tetrabromo-1H-benzimidazol-2-yl)-propane-1,3-diamine (K137) at its 3-amino position with a peptidic fragment composed of three or four glutamic or aspartic acid residues, a new family of bisubstrate inhibitors has been generated whose ability to simultaneously interact with both the ATP and the phosphoacceptor substrate-binding sites has been probed by running mixed competition kinetics and by mutational mapping of the kinase residues implicated in substrate recognition. The most effective bisubstrate inhibitor, K137-E4, interacts with three functional regions of the kinase: the hydrophobic pocket close to the ATP-binding site, the basic residues of the p+1 loop that recognizes the acidic determinant at position n+1 and the basic residues of α-helixC that recognize the acidic determinant at position n+3. Compared with the parent inhibitor (K137), K137-E4 is severalfold more potent (IC50 25 compared with 130 nM) and more selective, failing to inhibit any other kinase as drastically as CK2 out of 140 enzymes, whereas 35 kinases are inhibited more potently than CK2 by K137. K137-E4 is unable to penetrate the cell and to inhibit endogenous CK2, its pro-apoptotic efficacy being negligible compared with cell-permeant inhibitors; however, it readily inhibits ecto-CK2 on the outer cell surface, reducing the phosphorylation of several external phosphoproteins. Inhibition of ecto-CK2 by K137-E4 is accompanied by a slower migration of cancer cells as judged by wound healing assays. On the basis of the cellular responses to K137-E4, we conclude that ecto-CK2 is implicated in cell motility, whereas its contribution to the pro-survival role of CK2 is negligible.

Hologram QSAR models of a series of 6-arylquinazolin-4-amine inhibitors of a new Alzheimer's disease target: dual specificity tyrosine-phosphorylation-regulated kinase-1A enzyme

Dual specificity tyrosine-phosphorylation-regulated kinase-1A (DYRK1A) is an enzyme directly involved in Alzheimer's disease, since its increased expression leads to β-amyloidosis, Tau protein aggregation, and subsequent formation of neurofibrillary tangles. Hologram quantitative structure-activity relationship (HQSAR, 2D fragment-based) models were developed for a series of 6-arylquinazolin-4-amine inhibitors (36 training, 10 test) of DYRK1A. The best HQSAR model (q2 = 0.757; SEcv = 0.493; R2 = 0.937; SE = 0.251; R2pred = 0.659) presents high goodness-of-fit (R2 > 0.9), as well as high internal (q2 > 0.7) and external (R2pred > 0.5) predictive power. The fragments that increase and decrease the biological activity values were addressed using the colored atomic contribution maps provided by the method. The HQSAR contribution map of the best model is an important tool to understand the activity profiles of new derivatives and may provide information for further design of novel DYRK1A inhibitors.

Cell-permeable dual inhibitors of protein kinases CK2 and PIM-1: structural features and pharmacological potential

It has been proposed that dual inhibitors of protein kinases CK2 and PIM-1 are tools particularly valuable to induce apoptosis of cancer cells, a property, however, implying cell permeability, which is lacking in the case of selective CK2/PIM-1 inhibitors developed so far. To fill this gap, we have derivatized the scaffold of the promiscuous CK2 inhibitor TBI with a deoxyribose moiety, generating TDB, a selective, cell-permeable inhibitor of CK2 and PIM-1. Here, we shed light on the structural features underlying the potency and narrow selectivity of TDB by exploiting a number of TDB analogs and by solving the 3D structure of the TDB/CK2 complex at 1.25 Å resolution, one of the highest reported so far for this kinase. We also show that the cytotoxic efficacy of TDB is almost entirely due to apoptosis, is accompanied by parallel inhibition of cellular CK2 and PIM-1, and is superior to both those observed combining individual inhibitors of CK2 and PIM-1 and by treating cells with the CK2 inhibitor CX4945. These data, in conjunction with the observations that cancer cells are more susceptible than non-cancer cells to TDB and that such a sensitivity is maintained in a multi-drug resistance background, highlight the pharmacological potential of this compound.

Synthesis and properties of a selective inhibitor of homeodomain-interacting protein kinase 2 (HIPK2)

Homeodomain-interacting protein kinase 2 (HIPK2) is a Ser/Thr kinase controlling cell proliferation and survival, whose investigation has been hampered by the lack of specific inhibitors able to dissect its cellular functions. SB203580, a p38 MAP kinase inhibitor, has been used as a tool to inhibit HIPK2 in cells, but here we show that its efficacy as HIPK2 inhibitor is negligible (IC₅₀>40 µM). In contrast by altering the scaffold of the promiscuous CK2 inhibitor TBI a new class of HIPK2 inhibitors has been generated. One of these, TBID, displays toward HIPK2 unprecedented efficacy (IC₅₀ = 0.33 µM) and selectivity (Gini coefficient 0.592 out of a panel of 76 kinases). The two other members of the HIPK family, HIPK1 and HIPK3, are also inhibited by TBID albeit less efficiently than HIPK2. The mode of action of TBID is competitive with respect to ATP, consistent with modelling. We also provide evidence that TBID is cell permeable by showing that HIPK2 activity is reduced in cells treated with TBID, although with an IC₅₀ two orders of magnitude higher (about 50 µM) than in vitro.

Exploiting the repertoire of CK2 inhibitors to target DYRK and PIM kinases

Advantage has been taken of the relative promiscuity of commonly used inhibitors of protein kinase CK2 to develop compounds that can be exploited for the selective inhibition of druggable kinases other than CK2 itself. Here we summarize data obtained by altering the scaffold of CK2 inhibitors to give rise to novel selective inhibitors of DYRK1A and to a powerful cell permeable dual inhibitor of PIM1 and CK2. In the former case one of the new compounds, C624 (naphto [1,2-b]benzofuran-5,9-diol) displays a potency comparable to that of the first-in-class DYRK1A inhibitor, harmine, lacking however the drawback of drastically inhibiting monoamine oxidase-A (MAO-A) as harmine does. On the other hand the promiscuous CK2 inhibitor 4,5,6,7-tetrabromo-1H-benzimidazole (TBI,TBBz) has been derivatized with a sugar moiety to generate a 1-(β-D-2'-deoxyribofuranosyl)-4,5,6,7-tetrabromo-1H-benzimidazole (TDB) compound which inhibits PIM1 and CK2 with comparably high efficacy (IC50 values<100nM) and remarkable selectivity. TDB, unlike other dual PIM1/CK2 inhibitors described in the literature is readily cell permeable and displays a cytotoxic effect on cancer cells consistent with concomitant inhibition of both its onco-kinase targets. This article is part of a Special Issue entitled: Inhibitors of Protein Kinases (2012).

Recent advances in the design, synthesis, and biological evaluation of selective DYRK1A inhibitors: a new avenue for a disease modifying treatment of Alzheimer's?

With 24.3 million people affected in 2005 and an estimated rise to 42.3 million in 2020, dementia is currently a leading unmet medical need and costly burden on public health. Seventy percent of these cases have been attributed to Alzheimer's disease (AD), a neurodegenerative pathology whose most evident symptom is a progressive decline in cognitive functions. Dual specificity tyrosine phosphorylation regulated kinase-1A (DYRK1A) is important in neuronal development and plays a variety of functional roles within the adult central nervous system. The DYRK1A gene is located within the Down syndrome critical region (DSCR) on human chromosome 21 and current research suggests that overexpression of DYRK1A may be a significant factor leading to cognitive deficits in people with Alzheimer's disease (AD) and Down syndrome (DS). Currently, treatment options for cognitive deficiencies associated with Down syndrome, as well as Alzheimer's disease, are extremely limited and represent a major unmet therapeutic need. Small molecule inhibition of DYRK1A activity in the brain may provide an avenue for pharmaceutical intervention of mental impairment associated with AD and other neurodegenerative diseases. We herein review the current state of the art in the development of DYRK1A inhibitors.