Semi-quantitative models for identifying potent and selective transthyretin amyloidogenesis inhibitors

Rate-limiting dissociation of the tetrameric protein transthyretin (TTR), followed by monomer misfolding and misassembly, appears to cause degenerative diseases in humans known as the transthyretin amyloidoses, based on human genetic, biochemical and pharmacologic evidence. Small molecules that bind to the generally unoccupied thyroxine binding pockets in the native TTR tetramer kinetically stabilize the tetramer, slowing subunit dissociation proportional to the extent that the molecules stabilize the native state over the dissociative transition state—thereby inhibiting amyloidogenesis. Herein, we use previously reported structure-activity relationship data to develop two semi-quantitative algorithms for identifying the structures of potent and selective transthyretin kinetic stabilizers/amyloidogenesis inhibitors. The viability of these prediction algorithms, in particular the more robust in silico docking model, is perhaps best validated by the clinical success of tafamidis, the first-in-class drug approved in Europe, Japan, South America, and elsewhere for treating transthyretin aggregation-associated familial amyloid polyneuropathy. Tafamidis is also being evaluated in a fully-enrolled placebo-controlled clinical trial for its efficacy against TTR cardiomyopathy. These prediction algorithms will be useful for identifying second generation TTR kinetic stabilizers, should these be needed to ameliorate the central nervous system or ophthalmologic pathology caused by TTR aggregation in organs not accessed by oral tafamidis administration.     

Monoaryl derivatives as transthyretin fibril formation inhibitors: Design,synthesis, biological evaluation and structural analysis

Transthyretin (TTR) is a ß-sheet-rich homotetrameric protein that transports thyroxine (T4) and retinol both in plasma and in cerebrospinal fluid. TTR also interacts with amyloid-β, playing a protective role in Alzheimer’s disease. Dissociation of the native transthyretin (TTR) tetramer is widely accepted as the critical step in TTR amyloids fibrillogenesis, and is responsible for extracellular deposition of amyloid fibrils. Small molecules, able to bind in T4 binding sites and stabilize the TTR tetramer, are interesting tools to treat and prevent systemic ATTR amyloidosis. We report here the synthesis, in vitro evaluation and three-dimensional crystallographic analyses of new monoaryl-derivatives in complex with TTR. Of the derivatives reported here, the best inhibitor of TTR fibrillogenesis, 1d, exhibits an activity similar to diflunisal.     

Design,synthesis and biological evaluation of imidazole and oxazole fragments as HIV-1 integrase-LEDGF/p75 disruptors and inhibitors of microbial pathogens

We describe here the synthesis of libraries of novel 1-subtituted-5-aryl-1H-imidazole, 5-aryl-4-tosyl-4,5-dihydro-1,3-oxazole and 5-aryl-1,3-oxazole fragments via microwave (MW)-assisted cycloaddition of para-toluenesulfonylmethyl isocyanide (TosMIC) to imines and aldehydes. The compounds obtained were biologically evaluated in an AlphaScreen HIV-1 IN-LEDGF/p75 inhibition assay with six imidazole-based compounds (16c, 16f, 17c, 17f, 20a and 20d) displaying more than 50% inhibition at 10 µM, with IC₅₀ values ranging from 7.0 to 30.4 µM. Additionally the hypothesis model developed predicts all active scaffolds except 20d to occupy similar areas as the N-heterocyclic (A) moiety and two aromatic rings (B and C) of previously identified inhibitor 5. These results indicate that the identified compounds represent a viable starting point for their use as templates in the design of next generation inhibitors targeting the HIV-1 IN and LEDGF/p75 protein-protein interaction. In addition, the in vitro antimicrobial properties of these fragments were tested by minimum inhibitory concentration (MIC) assays showing that compound 16f exhibited a MIC value of 15.6 μg/ml against S. aureus, while 17f displayed a similar MIC value against B. cereus, suggesting that these compounds could be further developed to specifically target those microbial pathogens.     

Design,synthesis and fungicidal activity evaluation of novel pyrimidinamine derivatives containing phenyl-thiazole/oxazole moiety

Diflumetorim is a member of pyrimidinamine fungicides that possess excellent antifungal activities. Nevertheless, as reported that the activity of diflumetorim to corn rust (Puccinia sorghi) was not ideal (EC₅₀ = 53.26 mg/L). Herein, a series of novel pyrimidinamine derivatives containing phenyl-thiazole/oxazole moiety were designed based on our previous study and the structural characteristics of diflumetorim, synthesized and bioassayed to discover novel fungicides with excellent antifungal activities. Among these compounds, T18 gave the optimal fungicidal activity, which respectively offers control effects with EC₅₀ values of 0.93 mg/L against P. sorghi and 1.24 mg/L against E. graminis, significantly superior to commercial fungicides diflumetorim, tebuconazole, and flusilazole. Cell cytotoxicity results suggested that compound T18 has lower toxicities than diflumetorim. Furthermore, DFT calculation indicated that the phenyl-thiazole/oxazole moiety plays an unarguable role in the improvement of activity, which will contribute to designing and developing more potent compounds in the future.     

Design, synthesis, and evaluation of aza inhibitors of chorismate mutase

A series of aza inhibitors (4-9) of chorismate mutase (E.C. 5.4.99.5) was designed, prepared, and evaluated against the enzyme by monitoring the direct inhibition of the chorismate, 1, to prephenate, 2, conversion. None of these aza inhibitors displayed tighter binding to the enzyme than the native substrate chorismate or greater inhibitory action than the previously reported ether analogue, 3. Furthermore, no time-dependent loss of enzyme activity was observed in the presence of the two potentially reactive aza inhibitors (7 and 9). These results in conjunction with inhibition data from a broader series of chorismate mutase inhibitors allowed a novel proposal for the mechanistic role of chorismate mutase to be developed. This proposed mechanism was computationally verified and correlated with crystallographic studies of various chorismate mutases.     

Design,synthesis, and evaluation of quinazoline T cell proliferation inhibitors

We report here on a class of quinazoline molecules that inhibit T cell proliferation. The most potent compound N-p-tolyl-2-(3,4,5-trimethoxyphenyl)quinazolin-4-amine (S101) and its close analogs were found to inhibit the proliferation of T cells from human peripheral blood mononuclear cells (PBMC) and Jurkat cells, with IC₅₀ in the sub-micromolar range. The inhibitor induced G2 cell cycle arrest but did not inhibit IL-2 secretion. The anti-proliferative effect correlated with inhibition of the tyrosine phosphorylation of SLP-76, a molecular element in the signaling pathway of the T cell receptor (TCR). The inhibitor restrained proliferation of lymphocytes with much higher potency than non-hematopoietic cells. This new class of specific T cell proliferation inhibitors may serve as lead molecules for the development of agents aimed at diseases in which T cell signaling plays a role and agents to induce tolerance to grafted tissues or organs.     

Design, synthesis and evaluation of potent thymidylate synthase X inhibitors

Three synthesized series of compounds based on a thiazolidine core allowed identification of potent inhibitors of thymidylate synthase X. The evaluation of the catalytic activity of the enzyme in the presence of these molecules revealed two distinct classes of compounds that inhibit ThyX with submicromolar concentrations, which could lead, after optimization, to effective inhibitors with potential biomedical interest.     

Design,synthesis and evaluation of new thiazole-piperazines as acetylcholinesterase inhibitors

In this study, some new 2-(4-substituted piperazine-1-yl)-N-[4-(2-methylthiazol-4-yl)phenyl]acetamide derivatives were synthesized. The synthesized compounds were screened for their anticholinesterase activity on acetylcholinesterase (AChE) and butyrylcholinesterase (BChE) enzymes by in vitro Ellman’s method. The structural elucidation of the compounds was performed by using IR, ¹H-NMR, ¹³C-NMR and FAB⁺-MS spectral data and elemental analyses results. Biological assays revealed that at 0.1 µM concentration, the most active compounds against AChE were 5n, 5o and 5p that indicated 96.44, 99.83 and 89.70% inhibition rates, respectively. Besides, IC₅₀ value of the compound 5o was determined as 0.011 µM, whereas IC₅₀ value of standard drug donepezil was 0.054 µM. The synthesized compounds did not show any notable inhibitory activity against BChE.     

Design, synthesis and bioactivity evaluation of tribactam beta lactamase inhibitors

Known carbapenem compounds with inhibitory effect towards beta-lactamase enzymes are formed from bicyclical beta lactam structural scaffolds. On the basis of results from theoretical computational methods and molecular modelling we have designed and developed a synthetic route towards novel, biologically active tricyclic derivatives of carbapenems.     

Design,synthesis and evaluation of phenethylaminoheterocycles as Kv1.5 inhibitors

Phenethylaminoheterocycles have been prepared and assayed for inhibition of the K_v1.5 potassium ion channel as a potential approach to the treatment of atrial fibrillation. A diverse set of heterocycles were identified as potent K_v1.5 inhibitors and were advanced to pharmacodynamic evaluation based on selectivity and pharmacokinetic profile. Heterocycle optimization and template modification lead to the identification of compound 24 which demonstrated increased atrial effective refractory period in the rabbit pharmacodynamic model with mild effects on blood pressure and heart rate.     

Design,synthesis, and biological evaluation of novel ubiquitin-activating enzyme inhibitors

Ubiquitin-activating enzyme (E1), which catalyzes the activation of ubiquitin in the initial step of the ubiquitination cascade, is a potential therapeutic target in multiple myeloma and breast cancer treatment. However, only a few E1 inhibitors have been reported to date. Moreover, there has been little medicinal chemistry research on the three-dimensional structure of E1. Therefore, in the present study, we attempted to identify novel E1 inhibitors using structure-based drug design. Following the rational design, synthesis, and in vitro biological evaluation of several such compounds, we identified a reversible E1 inhibitor (4b). Compound 4b increased p53 levels in MCF-7 breast cancer cells and inhibited their growth. These findings suggest that reversible E1 inhibitors are potential anticancer agents.     

Design, synthesis, and evaluation of octahydropyranopyrrole-based inhibitors of mammalian ribonucleotide reductase

Inhibitors of mammalian ribonucleotide reductase possessing a novel octahydropyranopyrrole scaffold based on a cyclic heptapeptide inhibitor have been designed, synthesized, and evaluated. Structure-function studies reveal that the bicyclic scaffold is indeed necessary to maintain inhibitory activity.     

Design, synthesis, and evaluation of bisubstrate analog inhibitors of cholera toxin

Bisubstrate analog inhibitors in which a nicotinamide mimic is attached to a series of structurally diversified guanidines (arginine mimics) were synthesized and evaluated for inhibition of cholera toxin. The mechanism-based bisubstrate inhibitors were up to 1400-fold more potent than the natural substrate NAD+ and 400-fold more potent than the artificial substrate diethylamino (benzylidine-amino)guanidine (DEABAG) in an assay toward an intrinsically active mutant of wild-type cholera toxin.     

Synthesis and evaluation of anthranilic acid-based transthyretin amyloid fibril inhibitors

Eight small molecules were synthesized to evaluate the structure activity relationships (SAR) of N-substituted anthranilic acids. The molecules were synthesized by benzylation or arylation of methyl anthranilate. A light scattering-based amyloid fibril formation assay was used to evaluate potential inhibitors of transthyretin (TTR) amyloid fibril formation in vitro. The m-carboxyphenylated and o-trifluoromethylphenylated anthranilic acids are potent inhibitors that will be subjected to further SAR and structural analysis.     

Design, synthesis, and evaluation of potential inhibitors of nitric oxide synthase

Selective inhibitors of neuronal nitric oxide synthase (nNOS) were shown to protect brain and may be useful in the treatment of neurodegenerative diseases. In this context, our purpose has been to design and synthesize a new family of derivatives of thiadiazoles as possible inhibitors of nNOS. To achieve it a supervised artificial neural network model has been developed for the prediction of inhibition of Nitric Oxide Synthase using a dataset of 119 nNOS inhibitors. The definition of the molecules was achieved from a not-supervised neural network using a home made program named CODES. Also, thiadiazole-based heterocycles, previously predicted, were prepared as conformationally restricted analogues of a selective nNOS inhibitor, S-ethyl N-phenylisothiourea.     

Design,synthesis and cholinesterase inhibitory properties of new oxazole benzylamine derivatives

Abstract

The enzymes acetylcholinesterase (AChE) and butyrylcholinesterase (BChE) are primary targets in attenuating the symptoms of neurodegenerative diseases. Their inhibition results in elevated concentrations of the neurotransmitter acetylcholine which supports communication among nerve cells. It was previously shown for trans-4/5-arylethenyloxazole compounds to have moderate AChE and BChE inhibitory properties. A preliminary docking study showed that elongating oxazole molecules and adding a new NH group could make them more prone to bind to the active site of both enzymes. Therefore, new trans-amino-4-/5-arylethenyl-oxazoles were designed and synthesised by the Buchwald-Hartwig amination of a previously synthesised trans-chloro-arylethenyloxazole derivative. Additionally, naphthoxazole benzylamine photoproducts were obtained by efficient photochemical electrocyclization reaction. Novel compounds were tested as inhibitors of both AChE and BChE. All of the compounds exhibited binding preference for BChE over AChE, especially for trans-amino-4-/5-arylethenyl-oxazole derivatives which inhibited BChE potently (IC₅₀ in µM range) and AChE poorly (IC₅₀?100?µM). Therefore, due to the selectivity of all of the tested compounds for binding to BChE, these compounds could be applied for further development of cholinesterase selective inhibitors.

• HIGHLIGHTS

• Series of oxazole benzylamines were designed and synthesised

• The tested compounds showed binding selectivity for BChE

• Naphthoxazoles were more potent AChE inhibitors

     

Design, synthesis and evaluation of non-urea inhibitors of soluble epoxide hydrolase

Inhibition of soluble epoxide hydrolase (sEH) has been proposed as a new pharmaceutical approach for treating hypertension and vascular inflammation. The most potent sEH inhibitors reported in literature to date are urea derivatives. However, these compounds have limited pharmacokinetic profiles. We investigated non-urea amide derivatives as sEH inhibitors and identified a potent human sEH inhibitor 14-34 having potency comparable to urea-based inhibitors.     

Design, synthesis, and biological evaluation of new phosphodiesterase type 4 inhibitors

The design, synthesis, and biological evaluation of new phosphodiesterase type 4 inhibitors, which possess new templates instead of a cyclohexane ring, are described. The mode of interaction with the enzyme is discussed based on the structure-activity relationship (SAR) data obtained for the synthesized inhibitors. Furthermore, the roles of three pharmacophores, a catechol moiety, a nitrile moiety, and acidic moieties, are discussed using in silico docking studies. More detailed biological evaluations of selected compounds are also presented.     

Design, synthesis, and evaluation of alpha-ketoheterocycles as class C beta-lactamase inhibitors

A series of specific alpha-ketoheterocycles (benzoxazole, thiazole, imidazole, tetrazole, and thiazole-4-carboxylate) has been synthesized in order to assess their potential as beta-lactamase inhibitors. The syntheses were achieved either by construction of the heterocycle (benzoxazole) from an appropriate alpha-hydroxyimidate, followed by oxidation of the alcohol, or by direct reaction of methyl phenaceturate with a lithiated heterocycle. The properties of these compounds in aqueous solution are described and their inhibitory activity against beta-lactamases assessed. They did inhibit the class C beta-lactamase of Enterobacter cloacae P99 but not the TEM beta-lactamase. The most effective inhibitor of the former enzyme (K(i)=0.11 mM) was 5-(phenylacetylglycyl) tetrazole, probably because it is an anion at neutral pH. Interpretation of the results was aided by computational models of the tetrahedral adducts. Most of the compounds also inhibited alpha-chymotrypsin but not porcine pancreatic elastase.     

Design,synthesis, and biological evaluation of novel coxsackievirus B3 inhibitors

The synthesis and SAR study of a novel class of coxsackievirus B3 (CVB3) inhibitors are reported. These compounds could be considered as the 6-chloropurines substituted at position 9 with variously substituted bicyclic scaffolds (bicyclo[2.2.1]heptane/ene—norbornane or norbornene). The synthesis and biological evaluation of 31 target compounds are described. Several of the analogues inhibited CVB3 in the low micromolar range (0.66–2 μM). Minimal or no cytotoxicity was observed.