In vivo and in vitro SAR of tetracyclic MAPKAP-K2 (MK2) inhibitors. Part II

Spirocyclopropane- and spiroazetidine-substituted tetracycles 13D–E and 16A are described as orally active MK2 inhibitors. The spiroazetidine derivatives are potent MK2 inhibitors with IC₅₀ <3 nM and inhibit the release of TNFα (IC₅₀<0.3 μM) from hPBMCs and hsp27 phosphorylation in anisomycin stimulated THP-1 cells. The spirocyclopropane analogues are less potent against MK2 (IC₅₀ = 0.05–0.23 μM), less potent in cells (IC₅₀ <1.1 μM), but show good oral absorption. Compound 13E (100 mg/kg po; bid) showed oral activity in rAIA and mCIA, with significant reduction of swelling and histological score.     

2,4-Diaminopyrimidine MK2 inhibitors. Part II: Structure-based inhibitor optimization

We describe structure-based optimization of a series of novel 2,4-diaminopyrimidine MK2 inhibitors. Co-crystal structures (see accompanying Letter) demonstrated a unique inhibitor binding mode. Resulting inhibitors had IC₅₀ values as low as 19 nM and moderate selectivity against a kinase panel. Compounds 15, 31a, and 31b inhibit TNFα production in peripheral human monocytes.     

Part 1: Structure–Activity Relationship (SAR) investigations of fused pyrazoles as potent,selective and orally available inhibitors of p38α mitogen-activated protein kinase

A novel class of fused pyrazole-derived inhibitors of p38α mitogen-activated protein kinase (MAPK) is disclosed. These inhibitors were evaluated for their ability to inhibit the p38α enzyme, the secretion of TNFα in a LPS-challenged THP1 cell line and TNFα-induced production of IL-8 in 50% human whole blood. This series was optimized through a SAR investigation to provide inhibitors with IC₅₀ values in the low single-digit nanomolar range in whole blood. Further investigation of their pharmacokinetic profiles led to the identification of two potent and orally bioavailable p38 inhibitors 10m and 10q. Inhibitor 10m was found to be efficacious in vivo in the inhibition of TNFα production in LPS-stimulated Lewis rats with an ED₅₀ of 0.1 mg/kg while 10q was found to have an ED₅₀ of 0.05–0.07 mg/kg.     

Tetrahydropyridine derivatives with inhibitory activity on the production of proinflammatory cytokines: Part 1

We investigated proinflammatory cytokine TNFα production inhibitors in order to develop novel anti-inflammatory agents. According to the results, we found that 17, a pyrrole derivative possessing a tetrahydropyridine group at the β-position, showed potent inhibitory activity in vitro (inhibition of lipopolysaccharide (LPS) induced TNFα production in human whole blood, IC₅₀ = 1.86 μM) and in vivo (inhibition of LPS induced TNFα production in mice, ID₅₀ = 5.98 mg/kg).     

Novel 1-(2-aminopyrazin-3-yl)methyl-2-thioureas as potent inhibitors of mitogen-activated protein kinase-activated protein kinase 2 (MK-2)

Novel 1-(2-aminopyrazin-3-yl)methyl-2-thioureas are described as inhibitors of mitogen-activated protein kinase-activated protein kinase 2 (MK-2). These compounds demonstrate potent in vitro activity against the enzyme with IC₅₀ values as low as 15 nM, and suppress expression of TNFα in THP-1 cells and in vivo in an acute inflammation model in mice. The synthesis, structure–activity relationship (SAR), and biological evaluation of these compounds are discussed.     

Tetrahydropyridine derivatives with inhibitory activity on the production of proinflammatory cytokines: Part 2

We previously reported a novel pyrrole derivative 1 which possesses a tetrahydropyridine group at the β-position with a proinflammatory cytokine TNFα production inhibitor. Herein, we report the synthesis and biological activity of N- and α-position substituted tetrahydropyridine derivatives. In this series, we found that compound 3o showed good inhibitory activity in vitro (inhibition of lipopolysaccharide (LPS)-induced TNFα production in human whole blood, IC₅₀ = 0.44 μM) and compound 3i demonstrated potent inhibitory activity in vivo (inhibition of LPS-induced TNFα production in mice, ID₅₀ = 1.42 mg/kg).     

Anti-allergic principles of Rhinacanthus nasutus leaves

Three naphthoquinone derivatives, rhinacanthin-C (1), -D (2) and -N (3) were isolated from the extract of Rhinacanthus nasutus Kurz leaves and were tested for anti-allergic effect. The result indicated that all three compounds possessed very potent anti-allergic activity against antigen-induced β-hexosaminidase release as a marker of degranulation in RBL-2H3 cells with IC₅₀ values of 6.9, 8.9 and 6.4 μM, respectively. In addition, the effects of rhinacanthin-C, -D and -N on antigen-induced release of TNF-α and IL-4 were also examined. It was found that rhinacanthin-C showed the most potent on antigen-induced TNF-α release with an IC₅₀ value of 0.7 μM, followed by rhinacanthin-D (IC₅₀=3.8 μM) and rhinacanthin-N (IC₅₀=10.3 μM), whereas those for IL-4 were rhinacanthin-D (IC₅₀=5.4 μM), rhinacanthin-C (IC₅₀=7.0 μM) and rhinacanthin-N (IC₅₀=12.0 μM), respectively. The mechanisms in the late phase reaction of rhinacanthin-C, -D and -N were found to inhibit TNF-α and IL-4 gene expression in antigen-induced TNF-α and IL-4 releases on from RBL-2H3 cells as dose-dependent manners.The structure-activity trends of rhinacanthin-C,-D and-N on the inhibition of TNF-α release are as follow; substitution with octadienoic acid (rhinacanthin-C) conferred much higher activity than that of benzodioxo carboxylic acid ester (rhinacanthin-D) as well as naphthalene carboxylic acid ester (rhinacanthin-N). For the inhibition of IL-4 release, the substitution with octadienoic acid (rhinacanthin-C) and benzodioxo carboxylic acid ester (rhinacanthin-D) possessed the effect two-fold higher than that of naphthalene carboxylic acid ester (rhinacanthin-N).As regards active constituents for anti-allergic activity of R. nasutus, rhinacanthin-C, -D and -N are responsible for anti-allergic effect of this plant on both the early phase and late phase reactions. The finding may support the traditional use of R. nasutus leaves for treatment of allergy and allergy-related diseases.     

Part 2: Structure–activity relationship (SAR) investigations of fused pyrazoles as potent,selective and orally available inhibitors of p38α mitogen-activated protein kinase

A novel class of pyrazolopyridazine p38α mitogen-activated protein kinase (MAPK) inhibitors is disclosed. A structure activity relationship (SAR) investigation was conducted driven by the ability of these compounds to inhibit the p38α enzyme, the secretion of TNFα in a LPS-challenged THP1 cell line and TNFα-induced production of IL-8 in the presence of 50% human whole blood (hWB). This study resulted in the discovery of several inhibitors with IC₅₀ values in the single-digit nanomolar range in hWB. Further investigation of the pharmacokinetic profiles of these lead compounds led to the identification of three potent and orally bioavailable p38α inhibitors 2h, 2m, and 13h. Inhibitor 2m was found to be highly selective for p38α/β over a panel of 402 other kinases in Ambit screening, and was highly efficacious in vivo in the inhibition of TNFα production in LPS-stimulated Lewis rats with an ED₅₀ of ca. 0.08 mg/kg.     

Effects of the new adiponectin paralogous protein CTRP-3 and of LPS on cytokine release from monocytes of patients with type 2 diabetes mellitus

Aims/Hypothesis: It was the aim to investigate the hypothesis that the new C1q/TNF-family member CTRP-3 (C1q/TNF-related protein-3) acts anti-inflammatory in human monocytes from healthy controls and patients with type 2 diabetes mellitus (T2D). Methods: Monocytes were isolated from 20 healthy controls and 30 patients with T2D. IL-6 and TNF concentrations were measured by ELISA. CTRP-3 was expressed in insect cells and used for stimulation experiments. Results: Basal IL-6 and TNF were not different in control and in T2D monocytes. LPS-stimulation (1 μg/ml) significantly (p < 0.001) increased IL-6 and TNF in the supernatants of control and in T2D monocytes to a similar extent. CTRP-3 (1 μg/ml) significantly (p = 0.03) inhibited LPS-induced IL-6 in control monocytes but not in T2D monocytes. TNF upon co-stimulation with LPS and CTRP-3 was significantly (p = 0.012) lower in control than in T2D monocytes. LPS-induced TNF concentration was significantly and positively correlated with serum total cholesterol and LDL cholesterol in T2D patients. Conclusions: CTRP-3 inhibits LPS-induced IL-6 and TNF release. This anti-inflammatory effect is lost in T2D. Serum cholesterol concentration affects the pro-inflammatory potential of LPS to induce TNF release from T2D monocytes in the presence or absence of CTRP-3. CTRP-3 might partly account for the pro-inflammatory state in T2D.     

Ethyl 2-(benzylidene)-7-methyl-3-oxo-2,3-dihydro-5H-thiazolo[3,2-a]pyrimidine-6-carboxylate analogues as a new scaffold for protein kinase casein kinase 2 inhibitor

Protein kinase casein kinase 2 (PKCK2) is a constitutively active, growth factor-independent serine/threonine kinase, and changes in PKCK2 expression or its activity are reported in many cancer cells. To develop a novel PKCK2 inhibitor(s), we first performed cell-based phenotypic screening using 4000 chemicals purchased from ChemDiv chemical libraries (2000: randomly selected; 2000: kinase-biased) and performed in vitro kinase assay-based screening using hits found from the first screening. We identified compound 24 (C24)[(Z)-ethyl 5-(4-chlorophenyl)-2-(3,4-dihydroxybenzylidene)-7-methyl-3-oxo-3,5-dihydro-2H-thiazolo[3,2-a] pyrimidine-6-carboxylate] as a novel inhibitor of PKCK2 that is more potent and selective than 4,5,6,7-tetrabromobenzotriazole (TBB). In particular, compound 24 [half maximal inhibitory concentration (IC₅₀) = 0.56 μM] inhibited PKCK2 2.2-fold more efficiently than did TBB (IC₅₀ = 1.24 μM), which is quite specific toward PKCK2 with respect to ATP binding, in a panel of 31 human protein kinases. The K_i values of compound 24 and TBB for PKCK2 were 0.78 μM and 2.70 μM, respectively. Treatment of cells with compound 24 inhibited endogenous PKCK2 activity and showed anti-proliferative and pro-apoptotic effects against stomach and hepatocellular cancer cell lines more efficiently than did TBB. As expected, compound 24 also enabled tumor necrosis factor-related apoptosis inducing ligand (TRAIL)-resistant cancer cells to be sensitive toward TRAIL. In comparing the molecular docking of compound 24 bound to PKCK2α versus previously reported complexes of PKCK2 with other inhibitors, our findings suggest a new scaffold for specific PKCK2α inhibitors. Thus, compound 24 appears to be a selective, cell-permeable, potent, and novel PKCK2 inhibitor worthy of further characterization.     

Design and synthesis of 2-amino-6-(1H,3H-benzo[de]isochromen-6-yl)-1,3,5-triazines as novel Hsp90 inhibitors

A novel series of 2-amino-1,3,5-triazines bearing a tricyclic moiety as heat shock protein 90 (Hsp90) inhibitors is described. Molecular design was performed using X-ray cocrystal structures of the lead compound CH5015765 and natural Hsp90 inhibitor geldanamycin with Hsp90. We optimized affinity to Hsp90, in vitro cell growth inhibitory activity, water solubility, and liver microsomal stability of inhibitors and identified CH5138303. This compound showed high binding affinity for N-terminal Hsp90α (K_d = 0.52 nM) and strong in vitro cell growth inhibition against human cancer cell lines (HCT116 IC₅₀ = 0.098 μM, NCI-N87 IC₅₀ = 0.066 μM) and also displayed high oral bioavailability in mice (F = 44.0%) and potent antitumor efficacy in a human NCI-N87 gastric cancer xenograft model (tumor growth inhibition = 136%).     

Esculentin-2CHa: A host-defense peptide with differential cytotoxicity against bacteria,erythrocytes and tumor cells

The host-defense peptide, esculentin-2CHa (GFSSIFRGVA¹⁰KFASKGLGK D²⁰LAKLGVDLVA³⁰ CKISKQC) shows potent (MIC ≤ 6 μM) growth inhibitory activity against clinical isolates of multidrug-resistant strains of Staphylococcus aureus, Acinetobacter baumannii, and Stenotrophomonas maltophilia and differential cytotoxic activity against human erythrocytes (LC₅₀ = 150 μM) and human non-small cell lung adenocarcinoma A549 cells (LC₅₀ = 10 μM). Esculentin-2CHa significantly (P < 0.01) stimulates the release of the anti-inflammatory cytokine IL-10 by mouse lymphoid cells and elevates its production after stimulation with concanavalin A and significantly (P < 0.05) stimulates TNF-α production by peritoneal macrophages. Effects on IL-6 and IL-1β production were not significant. Removal of the hydrophobic N-terminal hexapeptide (GFSSIF) from esculentin-2CHa results in abolition of growth inhibitory activity against S. aureus and cytotoxic activity against erythrocytes and A549 cells as well as a marked (≥16-fold) reduction in potency against A. baumannii and S. maltophilia. The primary structure of esculentin-2 has been poorly conserved between frog species but evolutionary pressure has acted to maintain the hydrophobic character of this N-terminal hexapeptide sequence. Removal of the cyclic C-terminal domain (CKISKQC) and replacement of the Cys³¹ and Cys³⁷ residues by serine resulted in appreciable decreases in cytotoxicity against all microorganisms and against mammalian cells. The more cationic [D20K, D27K] analog showed a modest increase in potency against all microorganisms (up to 4-fold) but a marked increase in cytotoxicity against erythrocytes (LC₅₀ = 11 μM) and A549 cells (LC₅₀ = 3 μM).     

Novel alkynyl substituted 3,4-dihydropyrimidin-2(1H)-one derivatives as potential inhibitors of chorismate mutase

A series of novel alkynyl substituted 3,4-dihydropyrimidin-2(1H)-one (DHPM) derivatives were designed, synthesized and evaluated in vitro as potential inhibitors of chorismate mutase (CM). All these compounds were prepared via a multi-component reaction (MCR) involving sequential I₂-mediated Biginelli reaction followed by Cu-free Sonogashira coupling. Some of them showed promising inhibitory activities when tested at 30 μM. One compound showed dose dependent inhibition of CM with IC₅₀ value of 14.76 ± 0.54 μM indicating o-alkynylphenyl substituted DHPM as a new scaffold for the discovery of promising inhibitors of CM.     

Benzothiophene inhibitors of MK2. Part 2: Improvements in kinase selectivity and cell potency

Optimization of kinase selectivity for a set of benzothiophene MK2 inhibitors provided analogs with potencies of less than 500 nM in a cell based assay. The selectivity of the inhibitors can be rationalized by examination of X-ray crystal structures of inhibitors bound to MK2.     

A FRET-based assay for the discovery of West Nile Virus NS2B-NS3 protease inhibitors

The West Nile Virus (WNV) has been a worldwide epidemic since the early 1990s. Currently there are no therapeutic treatments for WNV infections. One particular avenue of treatment is inhibition of the NS2B-NS3 protease, an enzyme that is crucial for WNV replication. In our effort to increase the number of NS2B-NS3 protease inhibitors, we report a novel FRET-based high throughput assay for the discovery of WNV NS2B-NS3 protease inhibitors. For this assay, a FRET-based peptide substrate was synthesized and kinetically characterized with the NS2B-NS3 protease. The new substrate exhibits a K_m of 3.35 ± 0.31 μM, a k_cat of 0.0717 ± 0.0016 s^?1 and a k_cat/K_m of 21,400 ± 2000 M^?1 s^?1.     

A semi-synthetic derivative of artemisinin,artesunate inhibits prostaglandin E2 production in LPS/IFNγ-activated BV2 microglia

Artesunate is a semi-synthetic derivative of artemisinin used to treat malaria, and has been shown to possess anti-inflammatory activity. In this study, we have investigated the effect of artesunate on PGE₂ production/COX-2 protein expression in LPS + IFNγ-activated BV2 microglia. To further understand the mechanism of action of this compound, we investigated its interference with NF-κB and p38 MAPK signalling pathways. PGE₂ production was determined using EIA, while protein expressions of inflammatory targets like COX-2, mPGES-1, IκB, p38 and MAPKAPK2 were evaluated using western blot. An NF-κB-bearing luciferase reporter gene assay was used to test the effect of artesunate on NF-κB-mediated pro-inflammatory gene expression in HEK293 cells stimulated with TNFα (1 ng/ml). Artesunate (2 and 4 μM), significantly (p <0.01) suppressed PGE₂ production in LPS + IFNγ-activated BV2 microglia. This effect was found to be mediated via reduction in COX-2 and mPGES-1 proteins. Artesunate also produced significant inhibition of TNFα and IL-6 production in activated BV2 microglia. Further investigations showed that artesunate (0.5–4 μM) significantly (p <0.001) reduced NF-κB-driven luciferase expression, and inhibited IκB phosphorylation and degradation, through inhibition of IKK. Artesunate inhibited phosphorylation of p38 MAPK and its substrate MAPKAPK2 following stimulation of microglia with LPS + IFNγ. Taken together, we have shown that artesunate prevents neuroinflammation in BV2 microglia by interfering with NF-κB and p38 MAPK signalling.     

Effect of 1,25 dihydroxyvitamin D3 on intracellular IFN-γ and TNF-α positive T cell subsets in pulmonary tuberculosis

We studied the immunomodulatory effect of 1,25(OH)₂D₃ on single cell expression of IFN-γ and TNF-α cytokines in T cell subsets of pulmonary tuberculosis (PTB) patients (n = 22) and normal healthy subjects (n = 22). Peripheral blood mononuclear cells (PBMCs) were cultured with live Mycobacterium tuberculosis (MTB) with or without 1,25(OH)₂D₃ (10^?7 M) for 48 h. T cell subsets positive for IFN-γ and TNF-α were enumerated by flow cytometry and the culture supernatants were assayed for both the cytokines using ELISA. In both NHS and PTB patients, a significantly reduced percentage of IFN-γ and TNF-α expressing CD3+, CD3+CD4+ and CD3+CD8+ T cells were observed in cultures stimulated with live MTB and treated with 1,25(OH)₂D₃ compared to cultures without 1,25(OH)₂D₃ (NHS; CD3+ IFN-γ+: p < 0.0001; CD3+TNF-α +: p = 0.0292 and PTB; CD3+ IFN-γ+: p = 0.0292; CD3+ TNF-α +: p = 0.0028). The levels of IFN-γ and TNF-α in the culture supernatants of 1,25(OH)₂D₃ treated cultures were also found to be significantly decreased in both groups (NHS; IFN-γ: p = 0.0001; TNF-α: p < 0.0001) and (PTB; IFN-γ: p < 0.0001; TNF-α: p < 0.0001). A positive correlation was observed between IFN-γ and TNF-α expressing CD3+CD8+ T cells in MTB stimulated cultures treated with or without 1,25(OH)₂D₃ in NHS (p = 0.0001; p = 0.001, respectively) and PTB patients (p = 0.002; p = 0.005, respectively). The present study revealed the suppressive effect of 1,25(OH)₂D₃ on single cell expression of IFN-γ and TNF-α by CD3+CD4+ and CD3+CD8+ T cells in pulmonary tuberculosis. This suppressive effect of 1,25(OH)₂D₃ on proinflammatory and Th1 cytokine positive cells might have a role in reducing inflammation at the site of infection.