Synthesis of 1-(d-glucopyranosyl)-1,2,3-triazoles and their evaluation as glycogen phosphorylase inhibitors

Synthesis of C,N-Glycosides via Brønsted Acid-Catalyzed Azidation of exo-Glycals

The reaction of exo-glycals with azidotrimethylsilane in the presence of a Brønsted acid leads to the generation of the corresponding C,N-glycosyl azides. The majority of these glycosylation reactions proceed at room temperature with short reaction times. In addition, the targeted products were obtained in high yields with exclusive diastereoselectivity to the α-anomer in pyranose-based derivatives. Carbohydrate units based on mannose, galactose, arabinose, and ribose were also shown to proceed in high yields.

Design, synthesis, anticancer evaluation and molecular docking studies of 1,2,3-triazole incorporated 1,3,4-oxadiazole-Triazine derivatives

A new library of 1,2,3-triazole-incorporated 1,3,4-oxadiazole-triazine derivatives (9a-j) was designed, synthesized, and tested in vitro for anticancer activity against PC3 and DU-145 (prostate cancer), A549 (lung cancer), and MCF-7 (breast cancer) cancer cell lines using the MTT assay with etoposide as the control drug. The compounds exhibited remarkable anticancer activity, with IC50 values ranging from 0.16 ± 0.083 μM to 11.8 ± 7.46 μM, whereas the positive control ranged from 1.97 0.45 μM to 3.08 0.135 μM. Compound 9 d with a 4-pyridyl moiety shown exceptional anticancer activity against PC3, A549, MCF-7, and DU-145 cell lines, with IC50 values of 0.17 ± 0.063 μM, 0.19 ± 0.075 μM, 0.51 ± 0.083 μM, and 0.16 ± 0.083 μM, respectively.

Quantum Computational Investigation of (E)-1-(4-methoxyphenyl)-5-methyl-N′-(3-phenoxybenzylidene)-1H-1,2,3-triazole-4-carbohydrazide

The title compound was synthesized and structurally characterized. Theoretical IR, NMR (with the GIAO technique), UV, and nonlinear optical properties (NLO) in four different solvents were calculated for the compound. The calculated HOMO–LUMO energies using time-dependent (TD) DFT revealed that charge transfer occurs within the molecule, and probable transitions in the four solvents were identified. The in silico absorption, distribution, metabolism, and excretion (ADME) analysis was performed in order to determine some physicochemical, lipophilicity, water solubility, pharmacokinetics, drug-likeness, and medicinal properties of the molecule. Finally, molecular docking calculation was performed, and the results were evaluated in detail.

Chemoenzymatic and Protecting-Group-Free Synthesis of 1,4-Substituted 1,2,3-Triazole-α-d-glucosides with Potent Inhibitory Activity toward Lysosomal α-Glucosidase

α-Glucosyl triazoles have rarely been tested as α-glucosidase inhibitors, partly due to inefficient synthesis of their precursor α-d-glucosylazide (αGA1). Glycosynthase enzymes, made by nucleophile mutations of retaining β-glucosidases, produce αGA1 in chemical rescue experiments. Thermoanaerobacterium xylanolyticus glucosyl hydrolase 116 β-glucosidase (TxGH116) E441G nucleophile mutant catalyzed synthesis of αGA1 from sodium azide and pNP-β-d-glucoside (pNPGlc) or cellobiose in aqueous medium at 45 °C. The pNPGlc and azide reaction product was purified by Sephadex LH-20 column chromatography to yield 280 mg of pure αGA1 (68% yield). αGA1 was successfully conjugated with alkynes attached to different functional groups, including aryl, ether, amine, amide, ester, alcohol, and flavone via copper-catalyzed azide-alkyne cycloaddition (CuAAC) click chemistry reactions. These reactions afforded the 1,4-substituted 1,2,3-triazole-α-d-glucoside derivatives AGT2-14 without protection and deprotection. Several of these glucosyl triazoles exhibited strong inhibition of human lysosomal α-glucosidase, with IC50 values for AGT4 and AGT14 more than 60-fold lower than that of the commercial α-glucosidase inhibitor acarbose.

Cu(I)-Catalyzed Click Chemistry in Glycoscience and Their Diverse Applications

Copper(I)-catalyzed 1,3-dipolar cycloaddition between organic azides and terminal alkynes, commonly known as CuAAC or click chemistry, has been identified as one of the most successful, versatile, reliable, and modular strategies for the rapid and regioselective construction of 1,4-disubstituted 1,2,3-triazoles as diversely functionalized molecules. Carbohydrates, an integral part of living cells, have several fascinating features, including their structural diversity, biocompatibility, bioavailability, hydrophilicity, and superior ADME properties with minimal toxicity, which support increased demand to explore them as versatile scaffolds for easy access to diverse glycohybrids and well-defined glycoconjugates for complete chemical, biochemical, and pharmacological investigations. This review highlights the successful development of CuAAC or click chemistry in emerging areas of glycoscience, including the synthesis of triazole appended carbohydrate-containing molecular architectures (mainly glycohybrids, glycoconjugates, glycopolymers, glycopeptides, glycoproteins, glycolipids, glycoclusters, and glycodendrimers through regioselective triazole forming modular and bio-orthogonal coupling protocols). It discusses the widespread applications of these glycoproducts as enzyme inhibitors in drug discovery and development, sensing, gelation, chelation, glycosylation, and catalysis. This review also covers the impact of click chemistry and provides future perspectives on its role in various emerging disciplines of science and technology.

Dual-Target Compounds against Type 2 Diabetes Mellitus: Proof of Concept for Sodium Dependent Glucose Transporter (SGLT) and Glycogen Phosphorylase (GP) Inhibitors

A current trend in the quest for new therapies for complex, multifactorial diseases, such as diabetes mellitus (DM), is to find dual or even multi-target inhibitors. In DM, the sodium dependent glucose cotransporter 2 (SGLT2) in the kidneys and the glycogen phosphorylase (GP) in the liver are validated targets. Several (β-D-glucopyranosylaryl)methyl (het)arene type compounds, called gliflozins, are marketed drugs that target SGLT2. For GP, low nanomolar glucose analogue inhibitors exist. The purpose of this study was to identify dual acting compounds which inhibit both SGLTs and GP. To this end, we have extended the structure-activity relationships of SGLT2 and GP inhibitors to scarcely known (C-β-D-glucopyranosylhetaryl)methyl arene type compounds and studied several (C-β-D-glucopyranosylhetaryl)arene type GP inhibitors against SGLT. New compounds, such as 5-arylmethyl-3-(β-D-glucopyranosyl)-1,2,4-oxadiazoles, 5-arylmethyl-2-(β-D-glucopyranosyl)-1,3,4-oxadiazoles, 4-arylmethyl-2-(β-D-glucopyranosyl)pyrimidines and 4(5)-benzyl-2-(β-D-glucopyranosyl)imidazole were prepared by adapting our previous synthetic methods. None of the studied compounds exhibited cytotoxicity and all of them were assayed for their SGLT1 and 2 inhibitory potentials in a SGLT-overexpressing TSA201 cell system. GP inhibition was also determined by known methods. Several newly synthesized (C-β-D-glucopyranosylhetaryl)methyl arene derivatives had low micromolar SGLT2 inhibitory activity; however, none of these compounds inhibited GP. On the other hand, several (C-β-D-glucopyranosylhetaryl)arene type GP inhibitor compounds with low micromolar efficacy against SGLT2 were identified. The best dual inhibitor, 2-(β-D-glucopyranosyl)-4(5)-(2-naphthyl)-imidazole, had a K_i of 31 nM for GP and IC₅₀ of 3.5 μM for SGLT2. This first example of an SGLT-GP dual inhibitor can prospectively be developed into even more efficient dual-target compounds with potential applications in future antidiabetic therapy.

Influence of the cis/trans configuration on the supramolecular aggregation of aryltriazoles

The ability of trans- and cis-1,2-glucopyranosyl and cyclohexyl ditriazoles, synthesized by CuAAC "click" chemistry, to form gels was studied, their physical properties determined, and the self-aggregation behavior investigated by SEM, X-ray, and EDC studies. The results revealed that self-assembly was driven mainly by π-π stacking interactions, in addition to hydrogen bonding, with the aromatic rings adopting a high degree of parallelism, as seen in crystal packings and ECD data. Furthermore, π-bromine interactions between the bromine atom of the aryl substituents and the triazole units might also contribute to an overall stabilization of the supramolecular aggregation of bis(4-bromophenyl)triazoles. The trans or cis spatial disposition of the triazole rings is highly important for gelation, with the cis configuration having higher propensity.

The architecture of hydrogen and sulfur σ-hole interactions explain differences in the inhibitory potency of C-β-d-glucopyranosyl thiazoles, imidazoles and an N-β-d glucopyranosyl tetrazole for human liver glycogen phosphorylase and offer new insights to structure-based design

C-Glucopyranosyl imidazoles, thiazoles, and an N-glucopyranosyl tetrazole were assessed in vitro and ex vivo for their inhibitory efficiency against isoforms of glycogen phosphorylase (GP; a validated pharmacological target for the development of anti-hyperglycaemic agents). Imidazoles proved to be more potent inhibitors than the corresponding thiazoles or the tetrazole. The most potent derivative has a 2-naphthyl substituent, a K_i value of 3.2 µM for hepatic glycogen phosphorylase, displaying also 60% inhibition of GP activity in HepG2 cells, compared to control vehicle treated cells, at 100 μM. X-Ray crystallography studies of the protein - inhibitor complexes revealed the importance of the architecture of inhibitor associated hydrogen bonds or sulfur σ-hole bond interactions to Asn284 OD1, offering new insights to structure-based design efforts. Moreover, while the 2-glucopyranosyl-tetrazole seems to bind differently from the corresponding 1,2,3-triazole compound, the two inhibitors are equipotent.

New syntheses towards C-glycosyl type glycomimetics

Glycomimetics are compounds that resemble carbohydrate molecules in their chemical structure and/or biological effect. A large variety of compounds can be designed and synthesized to get glycomimetics, however, C-glycosyl derivatives represent one of the most frequently studied subgroup. In the present survey syntheses of a range of five- and six membered C-glycopyranosyl heterocycles, anhydro-aldimine type compounds, exo-glycals, C-glycosyl styrenes, carbon-sulfur bonded oligosaccharide mimics are described. Some of the C-glycopyranosyl azoles, namely 1,2,4-triazoles and imidazoles belong to the most efficient glucose analog inhibitors of glycogen phosphorylase known to date. Biological studies revealed the therapeutical potential of such inhibitors. Other synthetic derivatives offer versatile possibilities to get further glycomimetics.

Gram scale production of 1-azido-β-d-glucose via enzyme catalysis for the synthesis of 1,2,3-triazole-glucosides

The production of analytical amounts of azido sugars is used as a means of verifying catalytic acid/base mutations of retaining glycosidase, but application of this process to preparative synthesis has not been reported. The catalytic acid/base mutant of Thermoanaerobacterium xylanolyticus GH116 β-glucosidase, TxGH116D593A, catalyzed the gram scale production of 1-azido-β-d-glucose (1) from p-nitropheyl-β-d-glucopyranoside (pNPGlc) and azide via a transglucosylation reaction. Overnight reaction of the enzyme with pNPGlc and NaN₃ in aqueous MES buffer (pH 5.5) at 55 °C produced 1 (3.27 g), which was isolated as a white foamy solid in 96% yield. This 1 was successfully utilized for the synthesis of fifteen 1,2,3-triazole-β-d-glucosyl derivatives (2–16) containing a variety of functional groups, via click chemistry.

The retaining β-glucosidase acid/base mutant TxGH116D593A catalyzed the production of 1-azido-β-d-glucose for synthesis of 15 1,2,3-triazole β-glucosyl derivatives.

Synthesis of New C- and N-β-d-Glucopyranosyl Derivatives of Imidazole, 1,2,3-Triazole and Tetrazole, and Their Evaluation as Inhibitors of Glycogen Phosphorylase

The aim of the present study was to broaden the structure-activity relationships of C- and N-β-d-glucopyranosyl azole type inhibitors of glycogen phosphorylase. 1-Aryl-4-β-d-gluco-pyranosyl-1,2,3-triazoles were prepared by copper catalyzed azide-alkyne cycloadditions between O-perbenzylated or O-peracetylated β-d-glucopyranosyl ethynes and aryl azides. 1-β-d-Gluco-pyranosyl-4-phenyl imidazole was obtained in a glycosylation of 4(5)-phenylimidazole with O-peracetylated α-d-glucopyranosyl bromide. C-β-d-Glucopyranosyl-N-substituted-tetrazoles were synthesized by alkylation/arylation of O-perbenzoylated 5-β-d-glucopyranosyl-tetrazole or from a 2,6-anhydroheptose tosylhydrazone and arenediazonium salts. 5-Substituted tetrazoles were glycosylated by O-peracetylated α-d-glucopyranosyl bromide to give N-β-d-glucopyranosyl-C-substituted-tetrazoles. Standard deprotections gave test compounds which were assayed against rabbit muscle glycogen phosphorylase b. Most of the compounds proved inactive, the best inhibitor was 2-β-d-glucopyranosyl-5-phenyltetrazole (IC₅₀ 600 μM). These studies extended the structure-activity relationships of β-d-glucopyranosyl azole type inhibitors and revealed the extreme sensitivity of such type of inhibitors towards the structure of the azole moiety.

Nanomolar Inhibitors of Glycogen Phosphorylase Based on β-d-Glucosaminyl Heterocycles: A Combined Synthetic, Enzyme Kinetic, and Protein Crystallography Study

Aryl substituted 1-(β-d-glucosaminyl)-1,2,3-triazoles as well as C-β-d-glucosaminyl 1,2,4-triazoles and imidazoles were synthesized and tested as inhibitors against muscle and liver isoforms of glycogen phosphorylase (GP). While the N-β-d-glucosaminyl 1,2,3-triazoles showed weak or no inhibition, the C-β-d-glucosaminyl derivatives had potent activity, and the best inhibitor was the 2-(β-d-glucosaminyl)-4(5)-(2-naphthyl)-imidazole with a K_i value of 143 nM against human liver GPa. An X-ray crystallography study of the rabbit muscle GPb inhibitor complexes revealed structural features of the strong binding and offered an explanation for the differences in inhibitory potency between glucosyl and glucosaminyl derivatives and also for the differences between imidazole and 1,2,4-triazole analogues.

The 1,2,3-triazole ring as a bioisostere in medicinal chemistry

1,2,3-Triazole is a well-known scaffold that has a widespread occurrence in different compounds characterized by several bioactivities, such as antimicrobial, antiviral, and antitumor effects. Moreover, the structural features of 1,2,3-triazole enable it to mimic different functional groups, justifying its wide use as a bioisostere for the synthesis of new active molecules. Here, we provide an overview of the 1,2,3-triazole ring as a bioisostere for the design of drug analogs, highlighting relevant recent examples.

Rational design of reversible inhibitors for trehalose 6-phosphate phosphatases

In some organisms, environmental stress triggers trehalose biosynthesis that is catalyzed collectively by trehalose 6-phosphate synthase, and trehalose 6-phosphate phosphatase (T6PP). T6PP catalyzes the hydrolysis of trehalose 6-phosphate (T6P) to trehalose and inorganic phosphate and is a promising target for the development of antibacterial, antifungal and antihelminthic therapeutics. Herein, we report the design, synthesis and evaluation of a library of aryl d-glucopyranoside 6-sulfates to serve as prototypes for small molecule T6PP inhibitors. Steady-state kinetic techniques were used to measure inhibition constants (K_i) of a panel of structurally diverse T6PP orthologs derived from the pathogens Brugia malayi, Ascaris suum, Mycobacterium tuberculosis, Shigella boydii and Salmonella typhimurium. The binding affinities of the most active inhibitor of these T6PP orthologs, 4-n-octylphenyl α-d-glucopyranoside 6-sulfate (9a), were found to be in the low micromolar range. The K_i of 9a with the B. malayi T6PP ortholog is 5.3 ± 0.6 μM, 70-fold smaller than the substrate Michaelis constant. The binding specificity of 9a was demonstrated using several representative sugar phosphate phosphatases from the HAD enzyme superfamily, the T6PP protein fold family of origin. Lastly, correlations drawn between T6PP active site structure, inhibitor structure and inhibitor binding affinity suggest that the aryl d-glucopyranoside 6-sulfate prototypes will find future applications as a platform for development of tailored second-generation T6PP inhibitors.

Green synthesis and anticancer potential of chalcone linked-1,2,3-triazoles

A series of chalcone linked-1,2,3-triazoles was synthesized via cellulose supported copper nanoparticle catalyzed click reaction in water. The structures of all the compounds were analyzed by IR, NMR and Mass spectral techniques. All the synthesized products were subjected to 3-(4,5-dimethylthiazole-2-yl)-2,5-diphenyltetrazolium bromide (MTT) cytotoxicity assay against a panel of four human cancer cell lines (MCF-7, MIA-Pa-Ca-2, A549, HepG2) to check their anticancer potential. Compound 6h was found to be most active against all the tested cancer cell lines with IC₅₀ values in the range of 4-11 μM and showed better or comparable activity to the reference drug against all the tested cell lines. Cell cycle analysis revealed that compound 6h induces apoptosis and G2/S arrest in MIA-Pa-Ca-2 cells. Compound 6h triggers mitochondrial potential loss in pancreatic cancer MIA-Pa-Ca-2 cells. Further, Compound 6h also triggers caspase-3 and PARP-1 cleavage, which increases in dose dependent manner.

Glycogen phosphorylase inhibitors: a patent review (2013 - 2015)

INTRODUCTION

Control of glycemia is crucial in the treatment of type 2 diabetes complications. Glycogen phosphorylase (GP) releases glucose from the liver into the blood stream. Design of potent GP inhibitors is a therapeutic strategy in the context of type 2 diabetes.

AREAS COVERED

Glucose-based inhibitors have found potential applications since they now reach low nanomolar Ki values. Another set of patents disclose cholic acid/7-aza-indole conjugates for targeted drug delivery to the liver. A series of benzazepinones have also been reported as potent GP inhibitors. In vitro data are reported for GP inhibition but the in vivo biological data at the cellular or animal levels are often missing, even though the literature reported for these molecules is also discussed.

EXPERT OPINION

A structural analogy between glucose-based GP inhibitors and C-glucosides targeting sodium glucose co-transporter 2 (SGLT2) is intriguing. Cholic acid/7-aza-indole conjugates are promising in vivo drug delivery systems to the liver. Benzazepinones were very recently described and no associated literature is available, making it very difficult to comment at present. While industry has slowed down on GP inhibitors design, academic groups are pursuing investigations and have provided potential drug candidates which will resuscitate the interest for GP, including its potential for targeting cancer.

Antimicrobial and cytotoxic activities of 1,2,3-triazole-sucrose derivatives

A library of 1-(1',2,3,3',4,4',6-hepta-O-acetyl-6'-deoxy-sucros-6'-yl)-1,2,3-triazoles have been investigated for their antibacterial, antifungal and cytotoxic activities. Most of the target compounds showed good inhibitory activity against a variety of clinically and food contaminant important microbial pathogens. In particular, 1-(1',2,3,3',4,4',6-hepta-O-acetyl-6'-deoxy-sucros-6'-yl)-4-(4-pentylphenyl)-1,2,3-triazole (5) was highly active against all the tested bacteria with minimal inhibitory concentrations (MICs) ranging between 1.1 and 4.4 µM and bactericidal concentrations (MBCs) from 2.2 and 8.4 µM. The compound 1-(1',2,3,3',4,4',6-hepta-O-acetyl-6'-deoxy-sucros-6'-yl)-4-(4-bromophenyl)-1,2,3-triazole (3) showed antifungal activity with MICs from 0.6 to 4.8 µM and minimal fungicidal concentrations (MFCs) ranging between 1.2 and 8.9 µM. Furthermore, some of the compounds possessed moderate cytotoxicity against human breast, lung, cervical and hepatocellular carcinoma cell lines, without showing toxicity for non-tumor liver cells. The above mentioned derivatives represent promising leads for the development of new generation of sugar-triazole antifungal agents.

3-Glucosylated 5-amino-1,2,4-oxadiazoles: synthesis and evaluation as glycogen phosphorylase inhibitors

Glycogen phosporylase (GP) is a promising target for the control of glycaemia. The design of inhibitors binding at the catalytic site has been accomplished through various families of glucose-based derivatives such as oxadiazoles. Further elaboration of the oxadiazole aromatic aglycon moiety is now reported with 3-glucosyl-5-amino-1,2,4-oxadiazoles synthesized by condensation of a C-glucosyl amidoxime with N,N’-dialkylcarbodiimides or Vilsmeier salts. The 5-amino group introduced on the oxadiazole scaffold was expected to provide better inhibition of GP through potential additional interactions with the enzyme’s catalytic site; however, no inhibition was observed at 625 µM.

'Click chemistry' synthesis of 1-(α-D-mannopyranosyl)-1,2,3-triazoles for inhibition of α-mannosidases

Three new triazole conjugates derived from d-mannose were synthesized and assayed in in vitro assays to investigate their ability to inhibit α-mannosidase enzymes from the glycoside hydrolase (GH) families 38 and 47. The triazole conjugates were more selective for a GH47 α-mannosidase (Aspergillus saitoi α1,2-mannosidase), showing inhibition at the micromolar level (IC50 values of 50-250 μM), and less potent towards GH38 mannosidases (IC50 values in the range of 0.5-6 mM towards jack bean α-mannosidase or Drosophila melanogaster lysosomal and Golgi α-mannosidases). The highest selectivity ratio [IC50(GH38)/IC50(GH47)] of 100 was exhibited by the phenyltriazole conjugate. To understand structure-activity properties of synthesized compounds, 3-D complexes of inhibitors with α-mannosidases were built using molecular docking calculations.

Anti-bacterial glycosyl triazoles - Identification of an N-acetylglucosamine derivative with bacteriostatic activity against Bacillus

N-acetylglucosaminidases (GlcNAcases) play an important role in the remodeling and recycling of bacterial peptidoglycan. Inhibitors of bacterial GlcNAcases can serve as antibacterial agents and provide an opportunity for the development of new antibiotics. We report the synthesis of triazole derivatives of N-acetylglucosamine using a copper promoted azide-alkyne coupling reaction between 1-azido-N-acetylglucosamine and a small library of terminal alkynes prepared via the Ugi reaction. These compounds were evaluated for their ability to inhibit the growth of bacteria. Two compounds that show bacteriostatic activity against Bacillus were identified, with MIC values of approximately 60 μM in both cases. Bacillus subtilis cultured in the presence of sub-MIC amounts of the glycosyl triazole inhibitors exhibit an elongated phenotype characteristic of impaired cell division. This represents the first report of inhibitors of bacterial cell wall GlcNAcases that demonstrate inhibition of cell growth in whole cell assays.

Design, synthesis and bioactivity of novel glycosylthiadiazole derivatives

A series of novel glycosylthiadiazole derivatives, namely 2-phenylamino-5-glycosyl-1,3,4-thiadiazoles, were designed and synthesized by condensation between sugar aldehydes A/B and substituted thiosemicarbazide C followed by oxidative cyclization by treating with manganese dioxide. The original fungicidal activities results showed that some title compounds exhibited excellent fungicidal activities against Sclerotinia sclerotiorum (Lib.) de Bary and Pyricularia oryzae Cav, especially compounds F-5 and G-8 which displayed better fungicidal activities than the commercial fungicide chlorothalonil. At the same time, the preliminary studies based on the Elson-Morgan method indicated that many compounds exhibited some inhibitory activity toward glucosamine-6-phosphate synthase (GlmS). The structure-activity relationships (SAR) are discussed in terms of the effects of the substituents on both the benzene and the sugar ring.

C-Glucopyranosyl-1,2,4-triazoles As New Potent Inhibitors of Glycogen Phosphorylase

Glycogen phosphorylase inhibitors are considered as potential antidiabetic agents. 3-(β-d-Glucopyranosyl)-5-substituted-1,2,4-triazoles were prepared by acylation of O-perbenzoylated N (1)-tosyl-C-β-d-glucopyranosyl formamidrazone and subsequent removal of the protecting groups. The best inhibitor was 3-(β-d-glucopyranosyl)-5-(2-naphthyl)-1,2,4-triazole (K i = 0.41 μM against rabbit muscle glycogen phosphorylase b).

Glycogen phosphorylase inhibitors: a patent review (2008 - 2012)

INTRODUCTION

Glycogen phosphorylase (GP) is the enzyme responsible for the synthesis of glucose-1-phosphate, the source of energy for muscles and the rest of the body. The binding of different ligands in catalytic or allosteric sites assures activation and deactivation of the enzyme. A description of the regulation mechanism and the implications in glycogen metabolism are given.

AREAS COVERED

Deregulation of GP has been observed in diseases such as diabetes mellitus or cancers. Therefore, it appears as an attractive therapeutic target for the treatment of such pathologies. Numbers of inhibitors have been published in academic literature or patented in the last two decades. This review presents the main patent claims published between 2008 and 2012.

EXPERT OPINION

Good inhibitors with interesting IC50 and in vivo results are presented. However, such therapeutic strategy raises questions and some answers are proposed to bring new insights in the field.