From Antarctica to cancer research: a novel human DNA topoisomerase 1B inhibitor from Antarctic sponge Dendrilla antarctica

Nature has been always a great source of possible lead compounds to develop new drugs against several diseases. Here we report the identification of a natural compound, membranoid G, derived from the Antarctic sponge Dendrilla antarctica displaying an in vitro inhibitory activity against human DNA topoisomerase 1B. The experiments indicate that membranoid G, when pre-incubated with the enzyme, strongly and irreversibly inhibits the relaxation of supercoiled DNA. This compound completely inhibits the cleavage step of the enzyme catalytic mechanism by preventing protein binding to the DNA. Membranoid G displays also a cytotoxic effect on tumour cell lines, suggesting its use as a possible lead compound to develop new anticancer drugs.     

Identification of an imidazopyridine scaffold to generate potent and selective TYK2 inhibitors that demonstrate activity in an in vivo psoriasis model

Herein we report identification of an imidazopyridine class of potent and selective TYK2 inhibitors, exemplified by prototype 6, through constraint of the rotatable amide bond connecting the pyridine and aryl rings of compound 1. Further optimization led to generation of compound 30 that potently inhibits the TYK2 enzyme and the IL-23 pathway in cells, exhibits selectivity against cellular JAK2 activity, and has good pharmacokinetic properties. In mice, compound 30 demonstrated dose-dependent reduction of IL-17 production in a PK/PD model as well as in an imiquimod-induced psoriasis model. In this efficacy model, the IL-17 decrease was accompanied by a reduction of ear thickness indicating the potential of TYK2 inhibition as a therapeutic approach for psoriasis patients.     

Anti-inflammatory property of the urinary metabolites of nobiletin in mouse

Nobiletin, a major component of polymethoxyflavones in citrus fruits, has a broad spectrum of health beneficial properties including anti-inflammatory and anti-carcinogenic activities. The metabolite identification of nobiletin in mouse urine has concluded that it undergoes mono-demethylation (3'- and 4'-demethylnobiletin) and di-demethylation (3',4'-didemethylnobiletin) metabolic pathway. Biological screening of nobiletin and its metabolites has revealed that the metabolites possess more potent anti-inflammatory activity than their parent compound. Therefore, this letter reports the identification of nobiletin metabolites and their anti-inflammatory activity against LPS-induced NO production and iNOS, COX-2 protein expression in RAW264.7 macrophage.     

Discovery of GSK837149A, an inhibitor of human fatty acid synthase targeting the beta-ketoacyl reductase reaction

GSK837149A has been identified as a selective inhibitor of human fatty acid synthase (FAS). The compound was first isolated as a minor impurity in a sample found to be active against the enzyme in a high-throughput screening campaign. The structure of this compound was confirmed by NMR and MS studies, and evaluation of the newly synthesized molecule confirmed its activity against FAS. The compound and other analogs synthesized, all being symmetrical structures containing a bisulfonamide urea, act by inhibiting the beta-ketoacyl reductase activity of the enzyme. GSK837149A inhibits FAS in a reversible mode, with a K(i) value of approximately 30 nm, and it possibly binds to the enzyme-ketoacyl-ACP complex. Although initial results suggest that cell penetration for these compounds is impaired, they still can be regarded as useful tools with which to probe and explore the beta-ketoacyl reductase active site in FAS, helping in the design of new inhibitors.     

Discovery of oral and inhaled PDE4 inhibitors

The optimization of oxazole-based PDE4 inhibitor 1 has led to the identification of both oral (compound 16) and inhaled (compound 34) PDE4 inhibitors. Selectivity against PDE10/PDE11, off target screening, and in vivo activity in the rat are discussed.     

Going to the well no more: lawn format assays for ultra-high-throughput screening

Screening in a 'well-less' or lawn format provides a means to screen large compound collections against many targets in a fast, versatile and cost effective manner. The development of generic lawn format assays to screen various gene families against large compound collections should facilitate the identification of hits and tools to use in drug discovery and chemogenomic endeavours. Lawn format holds particular promise for screening GPCRs and selected enzyme families with potential use in other gene families.     

Discovery of a new class of catalytic topoisomerase II inhibitors targeting the ATP-binding site by structure based design. Part I

Topoisomerase II is a validated target in oncology. Among the different ways of blocking the function of this enzyme, inhibiting its ATPase activity has been relatively less investigated. In an effort to identify topoisomerase II inhibitors of a novel type, exerting their action by this mechanism, we have designed a purine inhibitor scaffold targeting the ATP-binding site of the enzyme. Searching the Novartis compound collection for molecules containing this purine motif has allowed the identification of two micromolar hits providing access to a new class of catalytic topoisomerase II inhibitors.     

Synthesis and SAR of novel imidazoquinoxaline-based Lck inhibitors: improvement of cell potency

A series of anilino(imidazoquinoxaline) analogues bearing solubilizing side chains at the 6- and 7-positions of the fused phenyl ring has been prepared and evaluated for inhibition against Lck enzyme and of T-cell proliferation. Significant improvement of the cellular activity was achieved over the initial lead, compound 2.     

Design, synthesis, and biological evaluation of novel tricyclic HIV-1 integrase inhibitors by modification of its pyridine ring

This communication details both the syntheses and biological evaluation of a novel class of HIV-1 integrase inhibitors. When the quinoline moiety is replaced with the quinoxoline moiety, the antiviral activity is significantly compromised. Similarly, introduction of imidazole to replace the pyridine ring is deleterious to the potency of the compound against the enzyme. Substitution at the 3-position of the pyridine has been investigated. The presence of the pyridine ring in the tricyclic core is preferred for antiviral activity against HIV integrase.     

Acylcyclohexanedione derivatives as potential in vivo sequential inhibitors of 4-hydroxyphenylpyruvate dioxygenase and GA(20) 3beta-hydroxylase

Acylcyclohexanedione derivatives have been designed, synthesized, and evaluated for in vitro inhibition activity against the enzyme 4-hydroxyphenylpyruvate dioxygenase (4-HPPD). The biological data demonstrated that 7 is a potent inhibitor of 4-HPPD with an IC(50) value of 40 nM. After metabolism, compound 7 has the potential to become a potent inhibitor of a second enzyme, GA(20) 3beta-hydroxylase.     

Exploring DNA topoisomerase I ligand space in search of novel anticancer agents

DNA topoisomerase I (Top1) is over-expressed in tumour cells and is an important target in cancer chemotherapy. It relaxes DNA torsional strain generated during DNA processing by introducing transient single-strand breaks and allowing the broken strand to rotate around the intermediate Top1-DNA covalent complex. This complex can be trapped by a group of anticancer agents interacting with the DNA bases and the enzyme at the cleavage site, preventing further topoisomerase activity. Here we have identified novel Top1 inhibitors as potential anticancer agents by using a combination of structure- and ligand-based molecular modelling methods. Pharmacophore models have been developed based on the molecular characteristics of derivatives of the alkaloid camptothecin (CPT), which represent potent antitumour agents and the main group of Top1 inhibitors. The models generated were used for in silico screening of the National Cancer Institute (NCI, USA) compound database, leading to the identification of a set of structurally diverse molecules. The strategy is validated by the observation that amongst these molecules are several known Top1 inhibitors and agents cytotoxic against human tumour cell lines. The potential of the untested hits to inhibit Top1 activity was further evaluated by docking into the binding site of a Top1-DNA complex, resulting in a selection of 10 compounds for biological testing. Limited by the compound availability, 7 compounds have been tested in vitro for their Top1 inhibitory activity, 5 of which display mild to moderate Top1 inhibition. A further compound, found by similarity search to the active compounds, also shows mild activity. Although the tested compounds display only low in vitro antitumour activity, our approach has been successful in the identification of structurally novel Top1 inhibitors worthy of further investigation as potential anticancer agents.     

Novel inhibitors of HIV protease: design, synthesis and biological evaluation of picomolar inhibitors containing cyclic P1/P2 scaffolds

A novel series of HIV protease inhibitors containing cyclic P1/P2 scaffolds has been synthesized and evaluated for biological activity. The trans 3,5-dibenzyl-2-oxo pyrrolidinone ring system resulted in a 50 pM enzyme inhibitor against HIV protease in vitro when combined with an indanolamine derived P'-backbone. This compound also shows comparable activity to currently marketed drugs in the MT-4 cell-based antiviral assay.     

8-Methoxy-naphtho[2,3-b]thiophen-4,9-quinone,a non-competitive inhibitor of trypanothione reductase

The enzyme trypanothione reductase is a recognised drug target in trypanosomatids and has been used in the search of new compounds with potential activity against diseases such as leishmaniasis, Chagas disease and African trypanosomiasis. 8-Methoxy-naphtho [2,3-b] thiophen-4,9-quinone was selected in a screening of natural and synthetic compounds using an in vitro assay with the recombinant enzyme from Trypanosoma cruzi. Its mode of inhibition fits a non-competitive model with respect to the substrate (trypanothione) and to the co-factor (NADPH), with Ki-values of 5 and 3.6 M, respectively. When tested against human glutathione reductase, this compound did not display any significant inhibition at 100 M, indicating a good selectivity against the parasite enzyme.     

A novel yeast cell-based screen identifies flavone as a tankyrase inhibitor

The telomere-associated protein tankyrase 1 is a poly(ADP-ribose) polymerase and is considered to be a promising target for cancer therapy, especially for BRCA-associated cancers. However, an efficient assay system for inhibitor screening has not been established, mainly due to the difficulty of efficient preparation of the enzyme and its substrate. Here, we report a cell-based assay system for detecting inhibitory activity against tankyrase 1. We found that overexpression of the human tankyrase 1 gene causes a growth defect in the fission yeast Schizosaccharomyces pombe. Chemicals that restore the growth defect phenotype can be identified as potential tankyrase 1 inhibitors. We performed a high-throughput screen using this system, and identified flavone as a compound that restores the growth of yeast cells overexpressing tankyrase 1. Indeed, flavone inhibited poly(ADP-ribosyl)ation of proteins caused by overexpression of tankyrase 1 in yeast cells. This system allows rapid identification of inhibitory activity against tankyrase 1 and is amenable to high-throughput screening using robotics.     

Acetylenic TACE inhibitors. Part 2: SAR of six-membered cyclic sulfonamide hydroxamates

The SAR of a series of potent sulfonamide hydroxamate TACE inhibitors bearing a butynyloxy P1' group was explored. In particular, compound 5k has excellent in vitro potency against TACE enzyme and in cells, and oral activity in an in vivo model of TNF-alpha production and a collagen-induced arthritis model.     

Synthesis and biological evaluation of new 2-alkylaminoethyl-1,1-bisphosphonic acids against Trypanosoma cruzi and Toxoplasma gondii targeting farnesyl diphosphate synthase

The effect of long-chain 2-alkylaminoethyl-1,1-bisphosphonates against proliferation of the clinically more relevant form of Trypanosoma cruzi, the etiologic agent of American trypanosomiasis (Chagas' disease), and against tachyzoites of Toxoplasma gondii was investigated. Particularly, compound 26 proved to be an extremely potent inhibitor against the intracellular form of T. cruzi, exhibiting IC(50) values at the nanomolar range. This cellular activity was associated with a strong inhibition of the enzymatic activity of T. cruzi farnesyl diphosphate synthase (TcFPPS), which constitutes a valid target for Chagas' disease chemotherapy. Compound 26 was an effective agent against T. cruzi (amastigotes) exhibiting an IC(50) value of 0.67 μM, while this compound showed an IC(50) value of 0.81 μM against the target enzyme TcFPPS. This drug was less effective against the enzymatic activity of T. cruzi solanesyl diphosphate synthase TcSPPS showing an IC(50) value of 3.2 μM. Interestingly, compound 26 was also very effective against T. gondii (tachyzoites) exhibiting IC(50) values of 6.23 μM. This cellular activity was also related to the inhibition of the enzymatic activity towards the target enzyme TgFPPS (IC(50)=0.093 μM) As bisphosphonate-containing compounds are FDA-approved drugs for the treatment of bone resorption disorders, their potential low toxicity makes them good candidates to control different tropical diseases.     

Antimicrobial activity and effects of resveratrol on human pathogenic bacteria

Resveratrol (3,4′,5-trihydroxistilbene) is a phytoalexin commonly found in food and drinks, which is thought to possess antimicrobial activity. These effects together with its well known antioxidant properties are beneficial for the prevention of some diseases, e.g. cancer. In this study we have verified that resveratrol has antibacterial activity against all tested Gram-positive bacteria using both the disk diffusion and broth microdilution methods. Time kill assays of this compound against Gram-positive bacteria showed that its effects on the growth of bacterial cells were due to bacteriostatic action. The addition of resveratrol has allowed the identification of changes in cell morphology and DNA contents, which have been assessed through microscopic analysis and flow cytometry; this suggests that the cell cycle is affected by resveratrol. This study indicates that this compound may have potential as a natural antibacterial agent for both food preservation and medicinal use.     

Synthesis and evaluation of indenopyrazoles as cyclin-dependent kinase inhibitors. Part 4: Heterocycles at C3

New indeno[1,2-c]pyrazol-4-one cyclin dependent kinase inhibitors have been disclosed. The most promising compounds are nanomolar enzyme inhibitors with excellent activity against tumor cells. The most advanced compound retains cell culture activity even in the presence of human serum proteins. The most advanced compound did not kill the normal fibroblast line AG1523.     

A novel series of enoyl reductase inhibitors targeting the ESKAPE pathogens, Staphylococcus aureus and Acinetobacter baumannii

S. aureus and A. baumannii are among the ESKAPE pathogens that are increasingly difficult to treat due to the rise in the number of drug resistant strains. Novel therapeutics targeting these pathogens are much needed. The bacterial enoyl reductase (FabI) is as potentially significant drug target for developing pathogen-specific antibiotics due to the presence of alternate FabI isoforms in many other bacterial species. We report the identification and development of a novel N-carboxy pyrrolidine scaffold targeting FabI in S. aureus and A. baumannii, two pathogens for which FabI essentiality has been established. This scaffold is unrelated to other known antibiotic families, and FabI is not targeted by any currently approved antibiotic. Our data shows that this scaffold displays promising enzyme inhibitory activity against FabI from both S. aureus and A. baumannii, as well as encouraging antibacterial activity in S. aureus. Compounds also display excellent synergy when combined with colistin and tested against A. baumannii. In this combination the MIC of colistin is reduced by 10-fold. Our first generation compound displays promising enzyme inhibition, targets FabI in S. aureus with a favorable selectivity index (ratio of cytotoxicity to MIC), and has excellent synergy with colistin against A. baumannii, including a multidrug resistant strain.     

Discovery of novel 1H-imidazol-2-yl-pyrimidine-4,6-diamines as potential antimalarials

A novel family of 1H-imidazol-2-yl-pyrimidine-4,6-diamines has been identified with potent activity against the erythrocyte-stage of Plasmodium falciparum (Pf), the most common causative agent of malaria. A systematic SAR study resulted in the identification of compound 40 which exhibits good potency against both wild-type and drug resistant parasites and exhibits good in vivo pharmacokinetic properties.