Rational design of novel diaryl ether-linked benzimidazole derivatives as potent and selective BACE1 inhibitors.

Due to the large size and high flexibility of the catalytic active site of BACE1 enzyme, the development of nonpeptide inhibitors with optimal pharmacological properties is still highly demanding. In this work, we have discovered 2-aminobenzimidazole-containg ether scaffolds having potent and selective inhibitory potentials against BACE1 enzyme. We have synthesized novel 29 compounds and optimization of aryl linker region resulted in highly potent BACE1 inhibitory activities with EC50 values of 0.05-2.71 µM. The aryloxy-phenyl analogs 20j showed the EC50 value as low as 0.07 µM in the enzyme assay, whereas, the benzyloxyphenyl dervative 24b was comparatively less effective in the enzyme assay. But interestingly the latter was more effective in the cell assay (EC50 value 1.2 µM). While comparing synthesized derivatives in the cell assay using PC12-APPSW cell, compound 27f appeared as the most potent BACE1 inhibitor having EC50 value 0.7 µM. This scaffold also showed high selectivity over BACE2 enzyme and cathepsin D. Furthermore, the research findings were bolstered through the incorporation of molecular docking, molecular dynamics, and DFT studies. We firmly believe that these discoveries will pave the way for the development of a novel class of small-molecule selective BACE1 inhibitors.

Novel potent blockers for TWIK-1/TREK-1 heterodimers as potential antidepressants.

TREK-1 (TWIK-related potassium channel-1) is a subunit of the two-pore domain potassium (K2p) channel and is widely expressed in the brain. TREK-1 knockout mice were shown to have antidepressant-like effects, providing evidence for the channel's potential as a therapeutic target. However, currently there is no good pharmacological inhibitor specifically targeting TREK-1 containing K2p channels that also displays similar antidepressant-like effects. Here, we sought to find selective and potent inhibitors for TREK-1 related dimers both in vitro and in vivo. We synthesized and evaluated 2-hydroxy-3-phenoxypropyl piperidine derivatives yielding a library from which many TREK-1 targeting candidates emerged. Among these, hydroxyl-phenyl- (2a), piperidino- (2g), and pyrrolidino- (2h) piperidinyl substituted compounds showed high potencies to TREK-1 homodimers with significant antidepressant-like effects in forced swim test and tail suspension test. Interestingly, these compounds were found to have high potencies to TWIK-1/TREK-1 heterodimers. Contrastingly, difluoropiperidinyl-4-fluorophenoxy (3e) and 4-hydroxyphenyl-piperidinyl-4-fluorophenoxy (3j) compounds had high potencies to TREK-1 homodimer but lower potency to TWIK-1/TREK-1 heterodimers without significant antidepressant-like effects. We observed positive correlation between inhibition potency to TWIK-1/TREK-1 and immobility time, and no correlation between inhibition potency to TREK-1 homodimer and immobility time. This was consistent with molecular docking simulations of selected compounds to TREK-1 homodimeric and TWIK-1/TREK-1 heterodimeric models. Existing antidepressant fluoxetine was also found to potently inhibit TWIK-1/TREK-1 heterodimers. Our study reveals novel potent TWIK-1/TREK-1 inhibitors 2a, 2g, and 2h as potential antidepressants and suggest that the TWIK-1/TREK-1 heterodimer could be a potential novel molecular therapeutic target for antidepressants.

A novel IRAK4/PIM1 inhibitor ameliorates rheumatoid arthritis and lymphoid malignancy by blocking the TLR/MYD88-mediated NF-κB pathway.

Interleukin-1 receptor-associated kinase 4 (IRAK4) is a pivotal enzyme in the Toll-like receptor (TLR)/MYD88 dependent signaling pathway, which is highly activated in rheumatoid arthritis tissues and activated B cell-like diffuse large B-cell lymphoma (ABC-DLBCL). Inflammatory responses followed by IRAK4 activation promote B-cell proliferation and aggressiveness of lymphoma. Moreover, proviral integration site for Moloney murine leukemia virus 1 (PIM1) functions as an anti-apoptotic kinase in propagation of ABC-DLBCL with ibrutinib resistance. We developed a dual IRAK4/PIM1 inhibitor KIC-0101 that potently suppresses the NF-κB pathway and proinflammatory cytokine induction in vitro and in vivo. In rheumatoid arthritis mouse models, treatment with KIC-0101 significantly ameliorated cartilage damage and inflammation. KIC-0101 inhibited the nuclear translocation of NF-κB and activation of JAK/STAT pathway in ABC-DLBCLs. In addition, KIC-0101 exhibited an anti-tumor effect on ibrutinib-resistant cells by synergistic dual suppression of TLR/MYD88-mediated NF-κB pathway and PIM1 kinase. Our results suggest that KIC-0101 is a promising drug candidate for autoimmune diseases and ibrutinib-resistant B-cell lymphomas.

Derivatives of 3, 4, 5-Trimethoxycinnamic Acid Ameliorate Stress-Induced Anxiety in Mice and Rats.

Stress is an overwhelming problem associated with neuronal damage leading to anxiety and depression. The compound 3, 4, 5-trimethoxycinnamic acid (TMCA) has shown anti-stress effects; however, its derivatives remained unknown for their anxiolytic properties. Here, therefore, we investigated derivatives of TMCA (dTMCA) for their anxiolytic effects using immobilization and electric shock-induced stress in rats. Derivatives of TMCA ameliorated anxiety in mice and rats revealed by extended period of time spent in the open arms of elevated plus maze. Stress-mediated repression of tyrosine hydroxylase (TH) protein expression in the amygdala regions of rat brain and dopamine levels in the PC12 cells was restored by two selected derivatives (TMCA#5 and TMCA#9). Unlike TH expression, stress-induced protein expression of phospho-extracellular signal-regulated kinase (pERK) was unaffected by both derivatives in rats. Given the preferential inhibitory activity of dTMCA on dopamine and serotonin receptors, serotonergic road map of cellular signaling could be their target for anxiolytic effects. Thus, dTMCA would be promising agents to prevent neuronal damage associated with rampant stressful conditions.

Discovery of GSK3ß Inhibitors through In Silico Prediction-and-Experiment Cycling Strategy, and Biological Evaluation.

Direct inhibitors of glycogen synthase kinase 3ß (GSK3ß) have been investigated and reported for the past 20 years. In the search for novel scaffold inhibitors, 3000 compounds were selected through structure-based virtual screening (SBVS), and then high-throughput enzyme screening was performed. Among the active hit compounds, pyrazolo [1,5-a]pyrimidin-7-amine derivatives showed strong inhibitory potencies on the GSK3ß enzyme and markedly activated Wnt signaling. The result of the molecular dynamics (MD) simulation, enhanced by the upper-wall restraint, was used as an advanced structural query for the SBVS. In this study, strong inhibitors designed to inhibit the GSK3ß enzyme were discovered through SBVS. Our study provides structural insights into the binding mode of the inhibitors for further lead optimization.

Evaluation of anti-depressant effects of phthalazinone-based triple-acting small molecules against 5-HT2A, 5-HT2C, and the serotonin transporter.

Development of highly effective, safe, and fast-acting anti-depressants is urgently required for the treatment of major depressive disorder. It has been suggested that targeting 5-HT2A and 5-HT2C in addition to inhibition of serotonin reuptake may be beneficial in generating anti-depressant agents with better pharmacology and less adverse effects. We have developed phthalazinone-based compounds that potently bind to 5-HT2A, 5-HT2C, and the serotonin transporter. The representative compounds 11j and 11l displayed strong binding affinities against these targets, and showed favorable toxicity profiles as determined by hERG binding and CYP inhibition assays. Furthermore, these compounds presented promising anti-depressant effects comparable to fluoxetine and also synergistic effects with fluoxetine in forced swimming test, which implicates these compounds can be developed to help the treatment of major depressive disorder.

Discovery of thienopyrrolotriazine derivatives to protect mitochondrial function against Aß-induced neurotoxicity.

Recovery of mitochondrial dysfunction has gained increasing attention as an alternative therapeutic strategy for Alzheimer's disease (AD). Recent studies suggested that the 18 kDa mitochondrial translocator protein (TSPO) has the potential to serve as a drug target for the treatment of AD. In this study, we generated a structure-based pharmacophore model and virtually screened a commercial library, identifying SVH07 as a virtual hit, which contained a tricyclic core structure, thieno[2',3':4,5]pyrrolo[1,2-d][1,2,4]triazine group. A series of SVH07 analogues were synthesized and their effects on the mitochondrial membrane potential and ATP production were determined by using neuronal cells under Aß-induced toxicity. Among these analogues, compound 26 significantly recovered mitochondrial membrane depolarization and ATP production. In vitro binding assays indicated that SVH07 and 26 showed high affinities to TSPO with the IC50 values in a nanomolar range. We believe that compound 26 is a promising lead compound for the development of TSPO-targeted mitochondrial functional modulators with therapeutic potential in AD.

KRICT-9 inhibits neuroinflammation, amyloidogenesis and memory loss in Alzheimer's disease models.

Alzheimer's disease (AD) is one of the most common forms of dementia and is characterized by neuroinflammation and amyloidogenesis. Here we investigated the effects of KRICT-9 on neuroinflammation and amyloidogenesis in in vitro and in vivo AD models. We found that KRICT-9 decreased lipopolysaccharide (LPS)-induced inflammation in microglial BV-2 cells and astrocytes while reducing nitric oxide generation and expression of inflammatory marker proteins (iNOS and COX-2) as well as APP, BACE1, C99, Iba-1, and GFAP. KRICT-9 also inhibited ß-secretase. Pull-down assays and docking model analyses indicated that KRICT-9 binds to the DNA binding domain of signal transducer and activator of transcription 3 (STAT3). KRICT-9 also decreased ß-secretase activity and Aß levels in tissues from LPS-induced mice brains, and it reversed memory impairment in mice. These experiments demonstrated that KRICT-9 protects against LPS-induced neuroinflammation and amyloidogenesis by inhibiting STAT3 activity. This suggests KRICT-9 or KRICT-9-inspired reagents could be used as therapeutic agents to treat AD.

Design, synthesis, biological evaluation and molecular modelling of 2-(2-aryloxyphenyl)-1,4-dihydroisoquinolin-3(2H)-ones: A novel class of TSPO ligands modulating amyloid-ß-induced mPTP opening.

Translocator protein (TSPO) is involved in modulating mitochondrial permeability transition pore (mPTP) opening/closure leading to either apoptotic cell death via opening of mPTP or cell protection mediated by mPTP blocking and hence intercepting mPTP induced apoptosis. Herein, 2-(2-aryloxyphenyl)-1,4-dihydroisoquinolin-3(2H)-one derivatives have been designed and synthesized as new modulators for amyloid-ß-induced mPTP opening. Among all, compound 7c remarkably enhanced mPTP opening while compound 7e showed the highest mPTP blocking activity. Molecular modelling study revealed different binding modes which might underlie the observed opposing biological activities. Both compounds bound to the translocator protein 18kDa (TSPO) in low micromolar range and elicited good profiles on CYP2D6 and CYP1A2. Taken as a whole, this report presents compound 7e as a hit TSPO ligand for treatment of neurodegenerative diseases and compound 7c as a hit TSPO ligand for promoting cell death of cells over-expressing TSPO.

Suppression of NFAT5-mediated Inflammation and Chronic Arthritis by Novel κB-binding Inhibitors.

Nuclear factor of activated T cells 5 (NFAT5) has been implicated in the pathogenesis of various human diseases, including cancer and arthritis. However, therapeutic agents inhibiting NFAT5 activity are currently unavailable. To discover NFAT5 inhibitors, a library of >40,000 chemicals was screened for the suppression of nitric oxide, a direct target regulated by NFAT5 activity, through high-throughput screening. We validated the anti-NFAT5 activity of 198 primary hit compounds using an NFAT5-dependent reporter assay and identified the novel NFAT5 suppressor KRN2, 13-(2-fluoro)-benzylberberine, and its derivative KRN5. KRN2 inhibited NFAT5 upregulation in macrophages stimulated with lipopolysaccharide and repressed the formation of NF-κB p65-DNA complexes in the NFAT5 promoter region. Interestingly, KRN2 selectively suppressed the expression of pro-inflammatory genes, including Nos2 and Il6, without hampering high-salt-induced NFAT5 and its target gene expressions. Moreover, KRN2 and KRN5, the latter of which exhibits high oral bioavailability and metabolic stability, ameliorated experimentally induced arthritis in mice without serious adverse effects, decreasing pro-inflammatory cytokine production. Particularly, orally administered KRN5 was stronger in suppressing arthritis than methotrexate, a commonly used anti-rheumatic drug, displaying better potency and safety than its original compound, berberine. Therefore, KRN2 and KRN5 can be potential therapeutic agents in the treatment of chronic arthritis.

Synthesis of (3S,4S)-4-aminopyrrolidine-3-ol derivatives and biological evaluation for their BACE1 inhibitory activities.

Synthesis, SAR study and BACE1 inhibitory activity of (3S,4S)-4-aminopyrrolidine-3-ol derivatives (2) were described. The compound 7c exhibited more inhibition activity than 11a (IC50: 0.05µM vs 0.12µM, respectively), but the latter was more effective in cell-based assay (IC50: 1.7µM vs 40% inhibition by 7c @ 10µM) due to the relatively higher cell permeability. Most of the compounds showed high selectivity over BACE2 and cathepsin D. This work will provide useful information for further structural modifications to develop potent BACE1 inhibitors in cell.

Discovery of potent and selective cytotoxic activity of new quinazoline-ureas against TMZ-resistant glioblastoma multiforme (GBM).

Herein, we report new quinazoline-urea based compounds with potent cytotoxic activities against TMZ-resistant glioblastoma multiforme (GBM) cells. Low micromolar IC50 values were exhibited over a panel of three primary GBM patient-derived cell cultures belonging to proneural (GBM-1), mesenchymal (GBM-2), and classical (GBM-3) subtypes. Eight compounds showed excellent selectivity indices for GBM cells comparing to a normal astrocyte cell line. In JC-1 assay, analogues 11, 12, 20, 22, and 24 exerted promising rates of mPTP opening induction towards proneural GBM subtype. Compounds 11, 20, and 24 bound to the translocator protein 18 kDa (TSPO) in submicromolar range using [(3)H] PK-11195 binding affinity assay. A homology model was built and docked models of 11, 12, 20, 22 and 24 were generated for describing their plausible binding modes in TSPO. In 3D clonogenic assay, compound 20 manifested potent tumoricidal effects on TMZ-resistant GBM cells even at submicromolar concentrations. In addition, CYP450 and hERG assays presented a safe toxicity profile of 20. Taken as a whole, this report presents compound 20 as a potent, selective and safe GBM cytotoxic agent which constitutes a promising direction against TMZ-resistant GBM.

Neuregulin 1 Controls Glutamate Uptake by Up-regulating Excitatory Amino Acid Carrier 1 (EAAC1).

Neuregulin 1 (NRG1) is a trophic factor that is thought to have important roles in the regulating brain circuitry. Recent studies suggest that NRG1 regulates synaptic transmission, although the precise mechanisms remain unknown. Here we report that NRG1 influences glutamate uptake by increasing the protein level of excitatory amino acid carrier (EAAC1). Our data indicate that NRG1 induced the up-regulation of EAAC1 in primary cortical neurons with an increase in glutamate uptake. These in vitro results were corroborated in the prefrontal cortex (PFC) of mice given NRG1. The stimulatory effect of NRG1 was blocked by inhibition of the NRG1 receptor ErbB4. The suppressed expression of ErbB4 by siRNA led to a decrease in the expression of EAAC1. In addition, the ablation of ErbB4 in parvalbumin (PV)-positive neurons in PV-ErbB4(-/-) mice suppressed EAAC1 expression. Taken together, our results show that NRG1 signaling through ErbB4 modulates EAAC1. These findings link proposed effectors in schizophrenia: NRG1/ErbB4 signaling perturbation, EAAC1 deficit, and neurotransmission dysfunction.

Synthesis and biological evaluation of 4-nitroindole derivatives as 5-HT2A receptor antagonists.

A novel series of 4-nitroindole sulfonamides containing a methyleneamino-N,N-dimethylformamidine were prepared. The binding of these compounds to 5-HT2A and 5-HT2C was evaluated, and most of the compounds showed IC50 values of less than 1µM, and exhibited high selectivity for the 5-HT2C receptor. However, little selectivity was observed in the functional assay for 5-HT6 receptors. The computational modeling studies further validated the biological results and also demonstrated a reasonable correlation between the activity of compounds and the mode of superimposition with specified pharmacophoric features.

Discovery of 4-(phenyl)thio-1H-pyrazole derivatives as agonists of GPR109A, a high affinity niacin receptor.

Even though nicotinic acid (niacin) appears to have beneficial effects on human lipid profiles, niacin-induced cutaneous vasodilatation called flushing limits its remedy to patient. GPR109A is activated by niacin and mediates the anti-lipolytic effects. Based on the hypothesis that ß-arrestin signaling mediates niacin-induced flushing, but not its anti-lipolytic effect, we tried to find GPR109A agonists which selectively elicit Gi-protein-biased signaling devoid of ß-arrestin internalization using a ß-lactamase assay. We identified a 4-(phenyl)thio-1H-pyrazole as a novel scaffold for GPR109A agonist in a high throughput screen, which has no carboxylic acid moiety known to be important for binding. While 1-nicotinoyl derivatives (5a-g, 6a-e) induced ß-arrestin recruitment, 1-(pyrazin-2-oyl) derivatives were found to play as G-protein-biased agonists without GPR109A receptor internalization. The activity of compound 5a (EC50 = 45 nM) was similar to niacin (EC50 = 52 nM) and MK-6892 (EC50 = 74 nM) on calcium mobilization assay, but its activity at 10 µM on ß-arrestin recruitment were around two and five times weaker than niacin and MK-6892, respectively. The development of G-protein biased GPR109A ligands over ß-arrestin pathway is attainable and might be important in differentiation of pharmacological efficacy.

Novel N-biphenyl-2-ylmethyl 2-methoxyphenylpiperazinylalkanamides as 5-HT7R antagonists for the treatment of depression.

5-HT7 receptor (5-HT7R) is a promising target for the treatment of depression and neuropathic pain. 5-HT7R antagonists exhibited antidepressant effects, while the agonists produced strong anti-hyperalgesic effects. In our efforts to discover selective 5-HT7R antagonists or agonists, N-biphenylylmethyl 2-methoxyphenylpiperazinylalkanamides 1 were designed, synthesized, and biologically evaluated against 5-HT7R. Among the synthesized compounds, N-2'-chlorobiphenylylmethyl 2-methoxyphenylpiperazinylpentanamide 1-8 showed the best binding affinity with a Ki value of 8.69nM and it was verified as a novel antagonist according to functional assays. The compound 1-8 was very selective over 5-HT1DR, 5-HT2AR, 5-HT3R, 5-HT5AR and 5-HT6R and moderately selective over 5-HT1AR, 5-HT1BR and 5-HT2CR. The novel 5-HT7R antagonist 1-8 exhibited an antidepressant effect at a dose of 25mg/kg in the forced swimming test in mice and showed a U-shaped dose-response curve which typically appears in 5-HT7R antagonists such as SB-269970 and lurasidone.

Biological evaluation of tanshindiols as EZH2 histone methyltransferase inhibitors.

EZH2 is the core subunit of Polycomb repressive complex 2 catalyzing the methylation of histone H3 lysine-27 and closely involved in tumorigenesis. To discover small molecule inhibitors for EZH2 methyltransferase activity, we performed an inhibitor screen with catalytically active EZH2 protein complex and identified tanshindiols as EZH2 inhibitors. Tanshindiol B and C potently inhibited the methyltransferase activity in in vitro enzymatic assay with IC50 values of 0.52µM and 0.55µM, respectively. Tanshindiol C exhibited growth inhibition of several cancer cells including Pfeiffer cell line, a diffuse large B cell lymphoma harboring EZH2 A677G activating mutation. Tanshindiol treatment in Pfeiffer cells significantly decreased the tri-methylated form of histone H3 lysine-27, a substrate of EZH2, as revealed by Western blot analysis and histone methylation ELISA. Based on enzyme kinetics and docking studies, we propose that tanshindiol-mediated inhibition of EZH2 activity is competitive for the substrate S-adenosylmethionine. Taken together, our findings strongly suggest that tanshindiols possess a unique anti-cancer activity whose mechanism involves the inhibition of EZH2 activity and would provide chemically valuable information for designing a new class of potent EZH2 inhibitors.

Inhibition of c-Kit signaling by diosmetin isolated from Chrysanthemum morifolium.

The interaction of stem cell factor (SCF) with its cognate receptor c-Kit is closely associated with the survival and maturation of melanocytes. To investigate novel depigmentation agents, we screened 2,000 plant extracts for c-Kit inhibitors to identify active small molecules by using time-resolved fluorescence enzyme assays. For the active extracts identified as inhibitors of c-Kit enzyme, we evaluated the effects of the active extracts and isolated flavonoids on c-Kit phosphorylation in MO7e/melanocytes. Anti-melanogenic activity was also examined in melanocytes and melanoderm model. The flavonoids such as diosmetin, apigenin, acacetin and luteolin isolated from Chrysanthemum morifolium were found to be active in inhibiting c-Kit both at enzyme and cellular levels. In addition, these flavonoids attenuated SCF-induced proliferation of human primary melanocytes without toxicity and suppressed ultraviolet (UV) B irradiation-mediated melanin synthesis significantly. Among the active flavonoids, diosmetin was found to inhibit SCF-induced melanogenesis in a human melanoderm model. These results strongly suggest that C. morifolium extract and diosmetin have potential to suppress SCF-/UVB-induced melanogenesis, and could be developed as anti-pigmentation agents.

Indatraline inhibits Rho- and calcium-mediated glioblastoma cell motility and angiogenesis.

Glioblastoma multiforme (GBM) is the most common and lethal primary brain tumor of the central nervous system (CNS). As an attempt to identify drugs for GBM therapeutics, phenotypic assays were used to screen 1000 chemicals from a clinical compound library. GBM subtypes exhibited different capabilities to induce angiogenesis when cultured on Matrigel; proneural cells migrated and formed a tube-like structure without endothelial cells. Among the compounds screened, indatraline, a nonselective monoamine transporter inhibitor, suppressed these morphological changes; it dose dependently inhibited cell spreading, migration, and in vitro/in vivo tube formation. In addition to intracellular calcium concentration, indatraline increased the level of Rho GTPase and its activity. Moreover, indatraline downregulated angiogenesis-related genes such as IGFBP2, PTN, VEGFA, PDGFRA, and VEGFR as well as nestin, a stem cell marker. These findings collectively suggest that the activation of Rho GTPase and the suppression of angiogenesis-related factors mediate the antiangiogenic activity of indatraline in proneural GBM culture.

Novel pyrimidoazepine analogs as serotonin 5-HT(2A) and 5-HT(2C) receptor ligands for the treatment of obesity.

Obesity is one of the most serious public health problems worldwide in the 21st century. Current therapeutic treatment for obesity is mostly focused on preventive measures involving dietary control and physical exercises in combination with anti-obesity medications. However, most of these anti-obesity medications have little or no effect on weight loss, and some cases have demonstrated fatal side effects. Due to the urgent need for highly potent and selective anti-obesity agents, the serotonin receptors (5-HTR) have been the focus of much interest as a novel therapeutic target. In this report, we have developed pyrimidoazepine analogs targeting the 5-HT2A and 5-HT2C receptors and evaluated their biological activity in vitro and in vivo as novel anti-obesity agents. We were able to identify 6p as the most potent 5-HT2A and 5-HT2C ligand in vitro (IC50 = 3 nM and 2.3 nM, respectively), and this compound also demonstrated the greatest potency in vivo. In an acute obesity model, mice treated with 6p showed significant decrease in body weight gain and food intake over approximately 77-94% compared to a control group. In a chronic obesity model, mice treated with 6p also showed a marked decrease in food intake and body weight gain.