Bis-aryl urea derivatives as potent and selective LIM kinase (Limk) inhibitors

Practical Three-Component Regioselective Synthesis of Drug-Like 3-Aryl(or heteroaryl)-5,6-dihydrobenzo[h]cinnolines as Potential Non-Covalent Multi-Targeting Inhibitors To Combat Neurodegenerative Diseases

Neurodegenerative diseases (NDs) are one of the prominent health challenges facing contemporary society, and many efforts have been made to overcome and (or) control it. In this research paper, we described a practical one-pot two-step three-component reaction between 3,4-dihydronaphthalen-1(2H)-one (1), aryl(or heteroaryl)glyoxal monohydrates (2a-h), and hydrazine monohydrate (NH2NH2•H2O) for the regioselective preparation of some 3-aryl(or heteroaryl)-5,6-dihydrobenzo[h]cinnoline derivatives (3a-h). After synthesis and characterization of the mentioned cinnolines (3a-h), the in silico multi-targeting inhibitory properties of these heterocyclic scaffolds have been investigated upon various Homo sapiens-type enzymes, including hMAO-A, hMAO-B, hAChE, hBChE, hBACE-1, hBACE-2, hNQO-1, hNQO-2, hnNOS, hiNOS, hPARP-1, hPARP-2, hLRRK-2(G2019S), hGSK-3β, hp38α MAPK, hJNK-3, hOGA, hNMDA receptor, hnSMase-2, hIDO-1, hCOMT, hLIMK-1, hLIMK-2, hRIPK-1, hUCH-L1, hPARK-7, and hDHODH, which have confirmed their functions and roles in the neurodegenerative diseases (NDs), based on molecular docking studies, and the obtained results were compared with a wide range of approved drugs and well-known (with IC50, EC50, etc.) compounds. In addition, in silico ADMET prediction analysis was performed to examine the prospective drug properties of the synthesized heterocyclic compounds (3a-h). The obtained results from the molecular docking studies and ADMET-related data demonstrated that these series of 3-aryl(or heteroaryl)-5,6-dihydrobenzo[h]cinnolines (3a-h), especially hit ones, can really be turned into the potent core of new drugs for the treatment of neurodegenerative diseases (NDs), and/or due to the having some reactionable locations, they are able to have further organic reactions (such as cross-coupling reactions), and expansion of these compounds (for example, with using other types of aryl(or heteroaryl)glyoxal monohydrates) makes a new avenue for designing novel and efficient drugs for this purpose.

Inhibition of airway smooth muscle contraction and proliferation by LIM kinase inhibitor, LIMKi3

PURPOSE

Current medical treatment for asthma aims to inhibit airway smooth muscle (ASM) contraction and proliferation, however, the efficacy of available treatment options is unsatisfactory. Therefore, we explored the effect of LIM domain kinase (LIMK) inhibitor - LIMKi3, on ASM to improve the understanding of ASM contraction and proliferation mechanisms, and to investigate new therapeutic targets.

MATERIALS AND METHODS

Asthma model was induced in rats by intraperitoneal injection of ovalbumin. Using phospho-specific antibodies, we examined LIMK, phosphorylated LIMK, cofilin and phosphorylated cofilin. ASM contraction was studied in organ bath experiments. ASM cells proliferation was studied with cell counting kit-8 (CCK-8) and 5-ethynyl-2'-deoxyuridine (EdU) assays.

RESULTS

Immunofluorescence indicated that LIMKs are expressed in ASM tissues. Western blot revealed that LIMK1 and phospho-cofilin were significantly elevated in asthma ASM tissues. The LIMK inhibitor, LIMKi3 (1 ​μM) could reduce cofilin phosphorylation and therefore inhibit contraction of ASM tissues, and induce actin filament breakdown as well as cell proliferation reduction in cultured human ASM cells.

CONCLUSIONS

ASM contraction and proliferation in asthma may underlie the effects of LIMKs. Small molecule LIMK inhibitor, LIMKi3, might be a potential therapeutic strategy for asthma.

LIM Kinases, LIMK1 and LIMK2, Are Crucial Node Actors of the Cell Fate: Molecular to Pathological Features

LIM kinase 1 (LIMK1) and LIM kinase 2 (LIMK2) are serine/threonine and tyrosine kinases and the only two members of the LIM kinase family. They play a crucial role in the regulation of cytoskeleton dynamics by controlling actin filaments and microtubule turnover, especially through the phosphorylation of cofilin, an actin depolymerising factor. Thus, they are involved in many biological processes, such as cell cycle, cell migration, and neuronal differentiation. Consequently, they are also part of numerous pathological mechanisms, especially in cancer, where their involvement has been reported for a few years and has led to the development of a wide range of inhibitors. LIMK1 and LIMK2 are known to be part of the Rho family GTPase signal transduction pathways, but many more partners have been discovered over the decades, and both LIMKs are suspected to be part of an extended and various range of regulation pathways. In this review, we propose to consider the different molecular mechanisms involving LIM kinases and their associated signalling pathways, and to offer a better understanding of their variety of actions within the physiology and physiopathology of the cell.

Comparative Analysis of Small-Molecule LIMK1/2 Inhibitors: Chemical Synthesis, Biochemistry, and Cellular Activity

LIM domain kinases 1 and 2 (LIMK1 and LIMK2) regulate actin dynamics and subsequently key cellular functions such as proliferation and migration. LIMK1 and LIMK2 phosphorylate and inactivate cofilin leading to increased actin polymerization. As a result, LIMK inhibitors are emerging as a promising treatment strategy for certain cancers and neurological disorders. High-quality chemical probes are required if the role of these kinases in health and disease is to be understood. To that end, we report the results of a comparative assessment of 17 reported LIMK1/2 inhibitors in a variety of in vitro enzymatic and cellular assays. Our evaluation has identified three compounds (TH-257, LIJTF500025, and LIMKi3) as potent and selective inhibitors suitable for use as in vitro and in vivo pharmacological tools for the study of LIMK function in cell biology.

Development and Characterization of Type I, Type II, and Type III LIM-Kinase Chemical Probes

LIMKs are important regulators of actin and microtubule dynamics, and they play essential roles in many cellular processes. Deregulation of LIMKs has been linked to the development of diverse diseases, including cancers and cognitive disabilities, but well-characterized inhibitors known as chemical probes are still lacking. Here, we report the characterization of three highly selective LIMK1/2 inhibitors covering all canonical binding modes (type I/II/III) and the structure-based design of the type II/III inhibitors. Characterization of these chemical probes revealed a low nanomolar affinity for LIMK1/2, and all inhibitors 1 (LIMKi3; type I), 48 (TH470; type II), and 15 (TH257; type III) showed excellent selectivity in a comprehensive scanMAX kinase selectivity panel. Phosphoproteomics revealed remarkable differences between type I and type II inhibitors compared with the allosteric inhibitor 15. In phenotypic assays such as neurite outgrowth models of fragile X-chromosome, 15 showed promising activity, suggesting the potential application of allosteric LIMK inhibitors treating this orphan disease.

Multitargeting the Action of 5-HT6 Serotonin Receptor Ligands by Additional Modulation of Kinases in the Search for a New Therapy for Alzheimer's Disease: Can It Work from a Molecular Point of View?

In view of the unsatisfactory treatment of cognitive disorders, in particular Alzheimer’s disease (AD), the aim of this review was to perform a computer-aided analysis of the state of the art that will help in the search for innovative polypharmacology-based therapeutic approaches to fight against AD. Apart from 20-year unrenewed cholinesterase- or NMDA-based AD therapy, the hope of effectively treating Alzheimer’s disease has been placed on serotonin 5-HT₆ receptor (5-HT₆R), due to its proven, both for agonists and antagonists, beneficial procognitive effects in animal models; however, research into this treatment has so far not been successfully translated to human patients. Recent lines of evidence strongly emphasize the role of kinases, in particular microtubule affinity-regulating kinase 4 (MARK4), Rho-associated coiled-coil-containing protein kinase I/II (ROCKI/II) and cyclin-dependent kinase 5 (CDK5) in the etiology of AD, pointing to the therapeutic potential of their inhibitors not only against the symptoms, but also the causes of this disease. Thus, finding a drug that acts simultaneously on both 5-HT₆R and one of those kinases will provide a potential breakthrough in AD treatment. The pharmacophore- and docking-based comprehensive literature analysis performed herein serves to answer the question of whether the design of these kind of dual agents is possible, and the conclusions turned out to be highly promising.

LIM Kinases, Promising but Reluctant Therapeutic Targets: Chemistry and Preclinical Validation In Vivo

LIM Kinases are important actors in the regulation of cytoskeleton dynamics by controlling microtubule and actin filament turnover. The signaling pathways involving LIM kinases for actin filament remodeling are well established. They are downstream effectors of small G proteins of the Rho-GTPases family and have become promising targets for the treatment of several major diseases because of their position at the lower end of these signaling cascades. Cofilin, which depolymerizes actin filaments, is the best-known substrate of these enzymes. The phosphorylation of cofilin to its inactive form by LIM kinases avoids actin filament depolymerization. The balance between phosphorylated and non-phosphorylated cofilin is thought to play an important role in tumor cell invasion and metastasis. Since 2006, many small molecules have been developed for LIMK inhibition, and in this review article, we will discuss the structure–activity relationships of the few inhibitor families that have been tested in vivo on different pathological models.

The Nature of Diamino Linker and Halogen Bonding Define Selectivity of Pyrrolopyrimidine-Based LIMK1 Inhibitors

The LIM-domain kinase (LIMK) family consists of two isoforms, LIMK1 and LIMK2, which are highly homologous, making selective inhibitor development challenging. LIMK regulates dynamics of the actin cytoskeleton, thereby impacting many cellular functions including cell morphology and motility. Here, we designed and synthesised analogues of a known pyrrolopyrimidine LIMK inhibitor with moderate selectivity for LIMK1 over LIMK2 to gain insights into which features contribute to both activity and selectivity. We incorporated a different stereochemistry around a cyclohexyl central moiety to achieve better selectivity for different LIMK isoforms. Inhibitory activity was assessed by kinase assays, and biological effects in cells were determined using an in vitro wound closure assay. Interestingly, a slight change in stereochemistry alters LIMK isoform selectivity. Finally, a docking study was performed to predict how the new compounds interact with the target.

Inhibition of LIM kinase reduces contraction and proliferation in bladder smooth muscle

Overactive bladder (OAB) is the most bothersome symptom in lower urinary tract symptoms (LUTS). Current pharmacologic treatment aims to inhibit detrusor contraction; however, shows unsatisfied efficacy and high discontinuation rate. LIM kinases (LIMKs) promote smooth muscle contraction in the prostate; however, their function in the bladder smooth muscle remains unclear. Here, we studied effects of the LIMK inhibitors on bladder smooth muscle contraction and proliferation both in vitro and in vivo experiments. Bladder expressions of LIMKs are elevated in OAB rat detrusor tissues. Two LIMK inhibitors, SR7826 and LIMKi3, inhibit contraction of human detrusor strip, and cause actin filament breakdown, as well as cell proliferation reduction in cultured human bladder smooth muscle cells (HBSMCs), paralleled by reduced cofilin phosphorylation. Silencing of LIMK1 and LIMK2 in HBSMCs resulted in breakdown of actin filaments and decreased cell proliferation. Treatment with SR7826 or LIMKi3 decreased micturition frequency and bladder detrusor hypertrophy in rats with bladder outlet obstruction. Our study suggests that LIMKs may promote contraction and proliferation in the bladder smooth muscle, which could be inhibited by small molecule LIMK inhibitors. LIMK inhibitors could be a potential therapeutic strategy for OAB- related LUTS.

Graph convolutional network approach to investigate potential selective Limk1 inhibitors

Since the Limk1 is a promising drug target and few inhibitors with good Limk1/ROCK2 selectivity have been reported, discovering potential and selective Limk1 inhibitors with novel scaffolds is becoming an urgent need to develop new treatments for the related diseases. Here, we utilized molecular docking to screen potential compounds of Limk1 from Traditional Chinese Medicine (TCM) database. Meanwhile, we performed a three-dimensional graph convolutional network (3DGCN), based on 3D molecular graph, to predict the inhibitory activity of Limk1 and ROCK2. Compared with the baseline models (RF, GCN and Weave), the 3DGCN achieved higher accuracy and the averaged RMSE values on test sets for Limk1 and ROCK2 were 0.721 and 0.852 respectively. In 3DGCN, above 80% of the test-set molecules from both two datasets were predicted within absolute error of 1.0 and the feature visualization suggested that it could automatically learn relevant structure features including 3D molecular information from a specific task for prediction. Furthermore, molecular dynamics (MD) simulations within 100 ns were employed to verify the stability of ligand-protein complexes and reveal the binding modes of the potential selective lead compounds of Limk1. Finally, integrating docking results, the predicted values by the 3DGCN and the MD analysis, we found that 7549 and 2007_15649 might be the potential and selective inhibitors for Limk1 receptor.

Semaphorin3F Drives Dendritic Spine Pruning Through Rho-GTPase Signaling

Dendritic spines of cortical pyramidal neurons are initially overproduced then remodeled substantially in the adolescent brain to achieve appropriate excitatory balance in mature circuits. Here we investigated the molecular mechanism of developmental spine pruning by Semaphorin 3F (Sema3F) and its holoreceptor complex, which consists of immunoglobulin-class adhesion molecule NrCAM, Neuropilin-2 (Npn2), and PlexinA3 (PlexA3) signaling subunits. Structure-function studies of the NrCAM-Npn2 interface showed that NrCAM stabilizes binding between Npn2 and PlexA3 necessary for Sema3F-induced spine pruning. Using a mouse neuronal culture system, we identified a dual signaling pathway for Sema3F-induced pruning, which involves activation of Tiam1-Rac1-PAK1-3 -LIMK1/2-Cofilin1 and RhoA-ROCK1/2-Myosin II in dendritic spines. Inhibitors of actin remodeling impaired spine collapse in the cortical neurons. Elucidation of these pathways expands our understanding of critical events that sculpt neuronal networks and may provide insight into how interruptions to these pathways could lead to spine dysgenesis in diseases such as autism, bipolar disorder, and schizophrenia.

A novel bis-aryl urea compound inhibits tumor proliferation via cathepsin D-associated apoptosis

Supplemental Digital Content is available in the text.

Derivatives of bis-aryl urea have been widely investigated for their various biological activities, such as antiviral, anti-inflammatory and antiproliferative. We evaluated a new chemical entity consisting of bis-aryl urea moiety, N69B, for its anticancer activities and explored their underlying molecular mechanism. The compound inhibited proliferation of multiple types of murine and human cancer cells in vitro, and reduced tumor growth in mouse 4T1 breast tumor model in vivo. Protein microarray analysis revealed and western blot confirmed that the compound significantly increased protein levels of cathepsins, especially cathepsin D, a lysosomal aspartyl protease known to have various pathophysiological functions. Further studies showed that the compound induced tumor cell apoptosis through the Bid/Bax/Cytochrome C/caspase 9/caspase 3 pathway, in which cathepsin D appeared to be a main mediator. Unlike kinase inhibition commonly seen with many other anticancer bis-aryl urea derivatives, this unique mechanism of N69B may suggest potential of the compound as a novel anticancer drug.

Small-Molecule Kinase Inhibitors for the Treatment of Nononcologic Diseases

Great successes have been achieved in developing small-molecule kinase inhibitors as anticancer therapeutic agents. However, kinase deregulation plays essential roles not only in cancer but also in almost all major disease areas. Accumulating evidence has revealed that kinases are promising drug targets for different diseases, including cancer, autoimmune diseases, inflammatory diseases, cardiovascular diseases, central nervous system disorders, viral infections, and malaria. Indeed, the first small-molecule kinase inhibitor for treatment of a nononcologic disease was approved in 2011 by the U.S. FDA. To date, 10 such inhibitors have been approved, and more are in clinical trials for applications other than cancer. This Perspective discusses a number of kinases and their small-molecule inhibitors for the treatment of diseases in nononcologic therapeutic fields. The opportunities and challenges in developing such inhibitors are also highlighted.

Relationships Between HIV-Mediated Chemokine Coreceptor Signaling, Cofilin Hyperactivation, Viral Tropism Switch and HIV-Mediated CD4 Depletion

HIV infection causes CD4 depletion and immune deficiency. The virus infects CD4 T cells through binding to CD4 and one of the chemokine coreceptors, CXCR4 (X4) or CCR5 (R5). It has also been known that HIV tropism switch, from R5 to X4, is associated with rapid CD4 depletion, suggesting a key role of viral factors in driving CD4 depletion. However, the virological driver for HIV-mediated CD4 depletion has not been fully elucidated. We hypothesized that HIV-mediated chemokine coreceptor signaling, particularly chronic signaling through CXCR4, plays a major role in CD4 dysfunction and depletion; we also hypothesized that there is an R5X4 signaling (R5X4sig) viral subspecies, evolving from the natural replication course of R5-utilizing viruses, that is responsible for CD4 T cell depletion in R5 virus infection. To gain traction for our hypothesis, in this review, we discuss a recent finding from Cui and co-authors who described the rapid tropism switch and high pathogenicity of an HIV-1 R5 virus, CRF01_AE. We speculate that CRF01_AE may be the hypothetical R5X4sig viral species that is rapidly evolving towards the X4 phenotype. We also attempt to discuss the intricate relationships between HIV-mediated chemokine coreceptor signaling, viral tropism switch and HIV-mediated CD4 depletion, in hopes of providing a deeper understanding of HIV pathogenesis in blood CD4 T cells.

Diarylureas as Antitumor Agents

The diarylurea is a scaffold of great importance in medicinal chemistry as it is present in numerous heterocyclic compounds with antithrombotic, antimalarial, antibacterial, and anti-inflammatory properties. Some diarylureas, serine-threonine kinase or tyrosine kinase inhibitors, were recently reported in literature. The first to come into the market as an anticancer agent was sorafenib, followed by some others. In this review, we survey progress over the past 10 years in the development of new diarylureas as anticancer agents.

Identification of Novel Rho-Kinase-II Inhibitors with Vasodilatory Activity

Small GTPase protein Rho-kinase (ROCK) plays an important role in the pathogenesis of hypertension. Inhibition of ROCK II brings about the biochemical changes leading to vascular smooth muscles relaxation, finally resulting into potent antihypertensive activity. In the quest for potent ROCK-II inhibitors, a ligand-based pharmacophore containing four essential chemical features, namely two hydrogen bond acceptor (HBA), one hydrogen bond donor (HBD), and one hydrophobe (HY), was developed and rigorously validated. The pharmacophore was used for virtual screening, and hits retrieved from the National Cancer Institute (NCI) database were sorted on the basis of fit value, estimate value, and Lipinski's violation. Potential feature interaction of hits was also observed during docking studies with the amino acids present in the active site of Rho-kinase. Based on the above screening, three hits (NSC 2488, NSC 2888, and NSC 4231) were chosen and subjected to in vitro Rho-kinase enzyme-based assay, followed by ex vivo rat aortic vasodilatory assay. All three compounds showed good biological activity as predicted by the model and confirmed by the docking studies.

A New Quantitative Cell-Based Assay Reveals Unexpected Microtubule Stabilizing Activity of Certain Kinase Inhibitors, Clinically Approved or in the Process of Approval

Agents able to modify microtubule dynamics are important anticancer drugs. The absence of microtubules resulting from drug-induced depolymerization is easy to detect. However the detection of a stabilized microtubule network needs specific assays since there is not a significant visual difference between normal and stabilized microtubule networks. Here, we describe a quantitative cell-based assay, suitable for automation, which allows the detection of stabilized microtubules without the need of microscopic examination. The rationale of this assay is based on the drug-induced resistance of the microtubule network to the depolymerizing agent combretastatin A4 and the subsequent detection of the residual microtubules by immunoluminescence. Using this assay to screen a kinase inhibitor library allowed the selection of seven known kinase inhibitors: selonsertib, masatinib, intedanib, PF0477736, SNS-314 mesylate, MPI0479605, and ponatinib. The yet undescribed ability of these inhibitors to stabilize cellular microtubules was confirmed using additional markers of stable microtubules and time-lapse video-microscopy to track individual microtubules in living cells. None of the compounds interacted, however, directly with tubulin. By employing other inhibitors of the same kinases, which have structurally unrelated scaffolds, we determined if the microtubule stabilizing effect was due to the inhibition of the targeted kinase, or to an off-target effect. Many of these inhibitors are clinically approved or currently assayed in phase 2 or phase 3 clinical trials. Their microtubule-stabilizing effect may account for their therapeutic effect as well as for some of their adverse side effects. These results indicate also a possible repurposing of some of these drugs.

Suppression of LIM Kinase 1 and LIM Kinase 2 Limits Glioblastoma Invasion

The aggressive brain tumor glioblastoma (GBM) is characterized by rapid cellular infiltration of brain tissue, raising the possibility that disease progression could potentially be slowed by disrupting the machinery of cell migration. The LIM kinase isoforms LIMK1 and LIMK2 (LIMK1/2) play important roles in cell polarization, migration, and invasion and are markedly upregulated in GBM and many other infiltrative cancers. Yet, it remains unclear whether LIMK suppression could serve as a viable basis for combating GBM infiltration. In this study, we investigated effects of LIMK1/2 suppression on GBM invasion by combining GBM culture models, engineered invasion paradigms, and mouse xenograft models. While knockdown of either LIMK1 or LIMK2 only minimally influenced invasion in culture, simultaneous knockdown of both isoforms strongly reduced the invasive motility of continuous culture models and human GBM tumor-initiating cells (TIC) in both Boyden chamber and 3D hyaluronic acid spheroid invasion assays. Furthermore, LIMK1/2 functionally regulated cell invasiveness, in part, by disrupting polarized cell motility under confinement and cell chemotaxis. In an orthotopic xenograft model, TICs stably transduced with LIMK1/2 shRNA were implanted intracranially in immunocompromised mice. Tumors derived from LIMK1/2 knockdown TICs were substantially smaller and showed delayed growth kinetics and more distinct margins than tumors derived from control TICs. Overall, LIMK1/2 suppression increased mean survival time by 30%. These findings indicate that LIMK1/2 strongly regulate GBM invasive motility and tumor progression and support further exploration of LIMK1/2 as druggable targets. SIGNIFICANCE: Targeting the actin-binding proteins LIMK1 and LIMK2 significantly diminishes glioblastoma invasion and spread, suggesting the potential value of these proteins as therapeutic targets.

Urea Derivatives in Modern Drug Discovery and Medicinal Chemistry

The urea functionality is inherent to numerous bioactive compounds, including a variety of clinically approved therapies. Urea containing compounds are increasingly used in medicinal chemistry and drug design in order to establish key drug-target interactions and fine-tune crucial drug-like properties. In this perspective, we highlight physicochemical and conformational properties of urea derivatives. We provide outlines of traditional reagents and chemical procedures for the preparation of ureas. Also, we discuss newly developed methodologies mainly aimed at overcoming safety issues associated with traditional synthesis. Finally, we provide a broad overview of urea-based medicinally relevant compounds, ranging from approved drugs to recent medicinal chemistry developments.

Pharmacologic inhibition of LIMK1 provides dendritic spine resilience against β-amyloid

Alzheimer's disease (AD) therapies predominantly focus on β-amyloid (Aβ), but Aβ effects may be maximal before clinical symptoms appear. Downstream of Aβ, dendritic spine loss correlates most strongly with cognitive decline in AD. Rho-associated kinases (ROCK1 and ROCK2) regulate the actin cytoskeleton, and ROCK1 and ROCK2 protein abundances are increased in early AD. Here, we found that the increased abundance of ROCK1 in cultured primary rat hippocampal neurons reduced dendritic spine length through a myosin-based pathway, whereas the increased abundance of ROCK2 induced spine loss through the serine and threonine kinase LIMK1. Aβ42 oligomers can activate ROCKs. Here, using static imaging studies combined with multielectrode array analyses, we found that the ROCK2-LIMK1 pathway mediated Aβ42-induced spine degeneration and neuronal hyperexcitability. Live-cell microscopy revealed that pharmacologic inhibition of LIMK1 rendered dendritic spines resilient to Aβ42 oligomers. Treatment of hAPP mice with a LIMK1 inhibitor rescued Aβ-induced hippocampal spine loss and morphologic aberrations. Our data suggest that therapeutically targeting LIMK1 may provide dendritic spine resilience to Aβ and therefore may benefit cognitively normal patients that are at high risk for developing dementia.

Current advances of tubulin inhibitors as dual acting small molecules for cancer therapy

Microtubule (MT)-targeting agents are highly successful drugs as chemotherapeutic agents, and this is attributed to their ability to target MT dynamics and interfere with critical cellular functions, including, mitosis, cell signaling, intracellular trafficking, and angiogenesis. Because MT dynamics vary in the different stages of the cell cycle, these drugs tend to be the most effective against mitotic cells. While this class of drug has proven to be effective against many cancer types, significant hurdles still exist and include overcoming aspects such as dose limited toxicities and the development of resistance. Newer generations of developed drugs attack these problems and alternative approaches such as the development of dual tubulin and kinase inhibitors are being investigated. This approach offers the potential to show increased efficacy and lower toxicities. This review covers different categories of MT-targeting agents, recent advances in dual inhibitors, and current challenges for this drug target.

A novel approach to white-light emission using a single fluorescent urea derivative and fluoride

First observation of white fluorescence using a single fluorescent urea derivative and fluoride.

Recent advances in the rational design and development of LIM kinase inhibitors are not enough to enter clinical trials

LIM kinases are involved in various pathophysiological processes that depend on actin organization. Alteration of microtubule dynamics by LIMK dysregulation is in fact related to tumor progression and metastasis, viral infection, and ocular diseases, such as glaucoma. As a consequence, many efforts have been done in recent years to rationally design small molecules able to inhibit LIMK activity selectively, without affecting other kinases. As a result, compounds optimized in terms of binding affinity and pharmacokinetic parameters have been discovered, that however failed to access clinical trials. In this review, a comprehensive survey of recent LIMK inhibitors is reported, together with SAR considerations and optimization processes.

Inhibition of human prostate smooth muscle contraction by the LIM kinase inhibitors, SR7826 and LIMKi3

BACKGROUND AND PURPOSE

In men with benign prostatic hyperplasia, increased smooth muscle tone in the prostate may lead to bladder outlet obstruction and subsequent lower urinary tract symptoms. Consequently, medical treatment aims to inhibit prostate smooth muscle contraction. However, the efficacy of the treatment options available is limited, and improved understanding of mechanisms of prostate smooth muscle contraction and identification of new targets for medical intervention are mandatory. Several studies suggest that LIM kinases (LIMKs) promote smooth muscle contraction; however, this has not yet been examined. Here, we studied effects of the LIMK inhibitors on prostate smooth muscle contraction.

EXPERIMENTAL APPROACH

Human prostate tissues were obtained from radical prostatectomy. Phosphorylation of cofilin, a LIMK substrate, was examined using a phospho-specific antibody. Smooth muscle contractions were studied in organ bath experiments.

KEY RESULTS

Real-time PCR, Western blot and immunofluorescence suggested LIMKs are expressed in smooth muscle cells of prostate tissues. Two different LIMK inhibitors, SR7826 (1 μM) and LIMKi3 (1 μM), inhibited contractions of prostate strips, which were induced by electrical field stimulation, α₁ -adrenoceptor agonists phenylephrine and methoxamine and the TXA₂ analogue, U46619. LIMK inhibition in prostate tissues and cultured stromal cells (WPMY-1) was confirmed by cofilin phosphorylation, which was reduced by SR7826 and LIMKi3. In WPMY-1 cells, SR7826 and LIMKi3 caused breakdown of actin filaments and reduced viability.

CONCLUSIONS AND IMPLICATIONS

Smooth muscle tone in the hyperplastic human prostate may underlie the effects of LIMKs, which promote contraction. Contraction of prostate strips can be inhibited by small molecule LIMK inhibitors.

LIM kinases: cofilin and beyond

LIM kinases are common downstream effectors of several signalization pathways and function as a signaling node that controls cytoskeleton dynamics through the phosphorylation of the cofilin family proteins. These last 10 years, several reports indicate that the functions of LIM kinases are more extended than initially described and, specifically, that LIM kinases also control microtubule dynamics, independently of their regulation of actin microfilament. In this review we analyze the data supporting these conclusions and the possible mechanisms that could be involved in the control of microtubules by LIM kinases. The demonstration that LIM kinases also control microtubule dynamics has pointed to new therapeutic opportunities. Consistently, several new LIM kinase inhibitors have been recently developed. We provide a comprehensive comparison of these inhibitors, of their chemical structure, their specificity, their cellular effects as well as their effects in animal models of various diseases including cancer.

Discovery of Novel Small-Molecule Inhibitors of LIM Domain Kinase for Inhibiting HIV-1

A dynamic actin cytoskeleton is necessary for viral entry, intracellular migration, and virion release. For HIV-1 infection, during entry, the virus triggers early actin activity by hijacking chemokine coreceptor signaling, which activates a host dependency factor, cofilin, and its kinase, the LIM domain kinase (LIMK). Although knockdown of human LIM domain kinase 1 (LIMK1) with short hairpin RNA (shRNA) inhibits HIV infection, no specific small-molecule inhibitor of LIMK has been available. Here, we describe the design and discovery of novel classes of small-molecule inhibitors of LIMK for inhibiting HIV infection. We identified R10015 as a lead compound that blocks LIMK activity by binding to the ATP-binding pocket. R10015 specifically blocks viral DNA synthesis, nuclear migration, and virion release. In addition, R10015 inhibits multiple viruses, including Zaire ebolavirus (EBOV), Rift Valley fever virus (RVFV), Venezuelan equine encephalitis virus (VEEV), and herpes simplex virus 1 (HSV-1), suggesting that LIMK inhibitors could be developed as a new class of broad-spectrum antiviral drugs.

IMPORTANCE The actin cytoskeleton is a structure that gives the cell shape and the ability to migrate. Viruses frequently rely on actin dynamics for entry and intracellular migration. In cells, actin dynamics are regulated by kinases, such as the LIM domain kinase (LIMK), which regulates actin activity through phosphorylation of cofilin, an actin-depolymerizing factor. Recent studies have found that LIMK/cofilin are targeted by viruses such as HIV-1 for propelling viral intracellular migration. Although inhibiting LIMK1 expression blocks HIV-1 infection, no highly specific LIMK inhibitor is available. This study describes the design, medicinal synthesis, and discovery of small-molecule LIMK inhibitors for blocking HIV-1 and several other viruses and emphasizes the feasibility of developing LIMK inhibitors as broad-spectrum antiviral drugs.

The Necessary Nitrogen Atom: A Versatile High-Impact Design Element for Multiparameter Optimization

There is a continued desire in biomedical research to reduce the number and duration of design cycles required to optimize lead compounds into high-quality chemical probes or safe and efficacious drug candidates. The insightful application of impactful molecular design elements is one approach toward achieving this goal. The replacement of a CH group with a N atom in aromatic and heteroaromatic ring systems can have many important effects on molecular and physicochemical properties and intra- and intermolecular interactions that can translate to improved pharmacological profiles. In this Perspective, the "necessary nitrogen atom" is shown to be a versatile high-impact design element for multiparameter optimization, wherein ≥10-, 100-, or 1000-fold improvement in a variety of key pharmacological parameters can be realized.

MiR-138-5p targeting LIMK1 suppresses breast cancer cell proliferation and motility

Breast cancer is the most frequently diagnosed female cancer.

Attenuation of Mycobacterium species through direct and macrophage mediated pathway by unsymmetrical diaryl urea

Tuberculosis is a major threat for mankind and the emergence of resistance strain of Mycobacterium tuberculosis (Mtb) against first line antibiotics makes it lethal for human civilization. In this study, we have synthesized different diaryl urea derivatives targeting the inhibition of mycolic acid biosynthesis. Among the 39 synthesized molecules, compounds 46, 57, 58 and 86 showed MIC values ≤ 10 μg/ml against H37Rv and mc²6030 strains. The best molecule with a methyl at ortho position of the first aromatic ring and prenyl group at the meta position of the second aromatic ring showed the MIC value of 5.2 μg/ml and 1 μg/ml against H37Rv and mc²6030 respectively, with mammalian cytotoxicity of 163.4 μg/ml. The effective compounds showed selective inhibitory effect on mycolic acid (epoxy mycolate) biosynthesis in ¹⁴C-radiolabelled assay. At the same time these molecules also executed their potent immunomodulatory activity by up-regulation of IFN-γ and IL-12 and down-regulation of IL-10.

Tetrahydro-pyrimido-indoles as selective LIMK inhibitors: synthesis, selectivity profiling and structure–activity studies

Extensive structure–activity studies on three different modification sites resulted in a series of LIM kinase inhibitors, containing a novel tricyclic hinge-binding motif based on the pyrrolopyrimidine scaffold.

LIM kinase inhibitors disrupt mitotic microtubule organization and impair tumor cell proliferation

The actin and microtubule cytoskeletons are critically important for cancer cell proliferation, and drugs that target microtubules are widely-used cancer therapies. However, their utility is compromised by toxicities due to dose and exposure. To overcome these issues, we characterized how inhibition of the actin and microtubule cytoskeleton regulatory LIM kinases could be used in drug combinations to increase efficacy. A previously-described LIMK inhibitor (LIMKi) induced dose-dependent microtubule alterations that resulted in significant mitotic defects, and increased the cytotoxic potency of microtubule polymerization inhibitors. By combining LIMKi with 366 compounds from the GSK Published Kinase Inhibitor Set, effective combinations were identified with kinase inhibitors including EGFR, p38 and Raf. These findings encouraged a drug discovery effort that led to development of CRT0105446 and CRT0105950, which potently block LIMK1 and LIMK2 activity in vitro, and inhibit cofilin phosphorylation and increase αTubulin acetylation in cells. CRT0105446 and CRT0105950 were screened against 656 cancer cell lines, and rhabdomyosarcoma, neuroblastoma and kidney cancer cells were identified as significantly sensitive to both LIMK inhibitors. These large-scale screens have identified effective LIMK inhibitor drug combinations and sensitive cancer types. In addition, the LIMK inhibitory compounds CRT0105446 and CRT0105950 will enable further development of LIMK-targeted cancer therapy.

Discovery, Development, and SAR of Aminothiazoles as LIMK Inhibitors with Cellular Anti-Invasive Properties

As part of a program to develop a small molecule inhibitor of LIMK, a series of aminothiazole inhibitors were discovered by high throughput screening. Scaffold hopping and subsequent SAR directed development led to a series of low nanomolar inhibitors of LIMK1 and LIMK2 that also inhibited the direct biomarker p-cofilin in cells and inhibited the invasion of MDA MB-231-luc cells in a matrigel inverse invasion assay.