Bicyclic benzofuran and indole-based salicylic acids as protein tyrosine phosphatase inhibitors

Study on SHP2 Conformational Transition and Structural Characterization of Its High-Potency Allosteric Inhibitors by Molecular Dynamics Simulations Combined with Machine Learning

The src-homology 2 domain-containing phosphatase 2 (SHP2) is a human cytoplasmic protein tyrosine phosphatase that plays a crucial role in cellular signal transduction. Aberrant activation and mutations of SHP2 are associated with tumor growth and immune suppression, thus making it a potential target for cancer therapy. Initially, researchers sought to develop inhibitors targeting SHP2's catalytic site (protein tyrosine phosphatase domain, PTP). Due to limitations such as conservativeness and poor membrane permeability, SHP2 was once considered a challenging drug target. Nevertheless, with the in-depth investigations into the conformational switch mechanism from SHP2's inactive to active state and the emergence of various SHP2 allosteric inhibitors, new hope has been brought to this target. In this study, we investigated the interaction models of various allosteric inhibitors with SHP2 using molecular dynamics simulations. Meanwhile, we explored the free energy landscape of SHP2 activation using enhanced sampling technique (meta-dynamics simulations), which provides insights into its conformational changes and activation mechanism. Furthermore, to biophysically interpret high-dimensional simulation trajectories, we employed interpretable machine learning methods, specifically extreme gradient boosting (XGBoost) with Shapley additive explanations (SHAP), to comprehensively analyze the simulation data. This approach allowed us to identify and highlight key structural features driving SHP2 conformational dynamics and regulating the activity of the allosteric inhibitor. These studies not only enhance our understanding of SHP2's conformational switch mechanism but also offer crucial insights for designing potent allosteric SHP2 inhibitors and addressing drug resistance issues.

Discovery of benzofuran-2-carboxylic acid derivatives as lymphoid tyrosine phosphatase (LYP) inhibitors for cancer immunotherapy

Lymphoid-tyrosine phosphatase (LYP) is mainly expressed in the immune system and plays an important role in the T-cell receptor (TCR) signaling pathway and tumor immunity. Herein, we identify benzofuran-2-carboxylic acid as a potent pTyr mimic and design a new series of new LYP inhibitors. The most active compound, D34 and D14, reversibly inhibits LYP (Ki = 0.93 μM and 1.34 μM) and possess a certain degree of selectivity toward other phosphatases. Meanwhile, D34 and D14 regulate the TCR signaling by specifically inhibiting LYP. In particular, D34 and D14 significantly suppress tumor growth in an MC38 syngeneic mouse model by boosting antitumor immunity, including activation of T-cell and inhibition of M2 macrophage polarization. Moreover, treatment of D34 or D14 upregulate PD-1/PD-L1 expression, which can be leveraged with PD-1/PD-L1 inhibition to augment immunotherapy. In summary, our study demonstrates the feasibility of targeting LYP for cancer immunotherapy and provides new lead compounds for further drug development.

Bacterial Protein Tyrosine Phosphatases as Possible Targets for Antimicrobial Therapies in Response to Antibiotic Resistance

The review is focused on the bacterial protein tyrosine phosphatases (PTPs) utilized by bacteria as virulence factors necessary for pathogenicity. The inhibition of bacterial PTPs could contribute to the arrest of the bacterial infection process. This mechanism could be utilized in the design of antimicrobial therapy as adjuvants to antibiotics. The review summaries knowledge on pathogenic bacterial protein tyrosine phosphatases (PTPs) involved in infection process, such as: PTPA and PTPB from Staphylococcus aureus and Mycobacterium tuberculosis; SptP from Salmonella typhimurium; YopH from Yersinia sp. and TbpA from Pseudomonas aeruginosa. The review focuses also on the potential inhibitory compounds of bacterial virulence factors and inhibitory mechanisms such as the reversible oxidation of tyrosine phosphatases.

Stitching Ynones with Nitromethanes: Domino Synthesis of Functionally Enriched Benzofurans and Benzothiophenes

A convenient one-pot benzannulation of regioisomeric 2- or 3-substituted furan and thiophene ynones with a range of nitromethanes has been discovered to directly access densely and diversely functionalized benzofurans and benzothiophenes. In this protocol, the nitro group in nitromethanes functions as recursive carbanion activator to setup tandem Michael addition-6π-electrocyclization, and its eventual sacrificial elimination facilitates aromatization and overall benzannulation. This benzannulation was also explored with furan/thiophene based o-halo ynones wherein a Michael addition-S_NAr process operates and nitromethanes leave their imprint to deliver nitro substituted benzo-furans and -thiophenes.

Synthesis and biological evaluation of geniposide derivatives as potent and selective PTPlB inhibitors

Herein a series of Geniposide derivatives were designed, synthesized and evaluated as protein tyrosine phosphatase 1B (PTPlB) inhibitors. Most of these compounds exhibited potent in vitro PTP1B inhibitory activities, the representative 7a and 17f were found to be the most potent inhibitors against the enzyme with IC₅₀ values of 0.35 and 0.41 μM, respectively. More importantly, they showcased 4 to10-fold selectivity over SHP2 and 3-fold over TCPTP. Further biological activity studies revealed that compounds 7a, 17b and 17f could effectively enhance insulin-stimulated glucose uptake with no significant cytotoxicity. Subsequent molecular docking and structural activity relationship analyses demonstrated that the glucose scaffold, benzylated glycosyl groups, and arylethenesulfonic acid ester significantly impact on the activity and selectivity.

Benzofuran-selenadiazole hybrids as novel α-glucosidase and cyclooxygenase-2 inhibitors with antioxidant and cytotoxic properties

Series of 2-arylbenzofuran-1,2,3-selenodiazole hybrids were prepared via multiple reactions and then evaluated in vitro through enzymatic assay for inhibitory effect against α-glucosidase and cyclooxygenase-2 (COX-2) activities including antioxidant activity. The presence of 1,2,3-selenodiazole moiety resulted in increased inhibitory effect for compounds 4a-f against α-glucosidase and COX-2 activities, and increased free radical scavenging activity. 6-Acetoxy-2-phenyl-5-(1,2,3-selenadiazol-4-yl)benzofuran (4a) and its 2-(4-methoxyphenyl) substituted derivative (4f) were, in turn, screened for antiproliferation against the breast MCF-7 cancer cell line and for cytotoxicity on the human embryonic kidney derived Hek293-T cells. A cell-based antioxidant activity assay involving lipopolysaccharide induced reactive oxygen species production in these cells was performed. Molecular docking has also been performed on these two compounds to predict protein-ligand interactions against α-glucosidase and COX-2.

Spiroindolone Analogues as Potential Hypoglycemic with Dual Inhibitory Activity on α-Amylase and α-Glucosidase

Inhibition of α-amylase and α-glucosidase by specified synthetic compounds during the digestion of starch helps control post-prandial hyperglycemia and could represent a potential therapy for type II diabetes mellitus. A new series of spiroheterocyclic compounds bearing oxindole/benzofuran/pyrrolidine/thiazolidine motifs were synthesized via a 1,3-dipolar cyclo-addition reaction approach. The specific compounds were obtained by reactions of chalcones having a benzo[b]furan scaffold (compounds 2a-f), with a substituted isatin (compounds 3a-c) and heterocyclic amino acids (compounds 4a,b). The target spiroindolone analogues 5a-r were evaluated for their potential inhibitory activities against the enzymes α-amylase and α-glucosidase. Preliminary results indicated that some of the target compounds exhibit promising α-amylase and α-glucosidase inhibitory activity. Among the tested spiroindolone analogues, the cycloadduct 5r was found to be the most active (IC50 = 22.61 ± 0.54 μM and 14.05 ± 1.03 μM) as α-amylase and α-glucosidase inhibitors, with selectivity indexes of 0.62 and 1.60, respectively. Docking studies were carried out to confirm the binding interaction between the enzyme active site and the spiroindolone analogues.

PTP1b Inhibition, A Promising Approach for the Treatment of Diabetes Type II

BACKGROUND

Diabetes Mellitus (DM), is a metabolic disorder characterized by high blood glucose levels. The main types of diabetes mellitus are Diabetes mellitus type I, Diabetes mellitus type II, gestational diabetes and Diabetes of other etiology. Diabetes type II, the Non Insulin Dependent Type (NIDDM) is the most common type, characterized by the impairment in activation of the intracellular mechanism leading to the insertion and usage of glucose after interaction of insulin with its receptor, known as insulin resistance. Although, a number of drugs have been developed for the treatment of diabetes type II, their ability to reduce blood glucose levels is limited, while several side effects are also observed. Furthermore, none of the market drugs targets the enhancement of the action of the intracellular part of insulin receptor or recuperation of the glucose transport mechanism in GLUT4 dependent cells. The Protein Tyrosine Phosphatase (PTP1b) is the main enzyme involved in insulin receptor desensitization and has become a drug target for the treatment of Diabetes type II. Several PTP1b inhibitors have already been found, interacting with the binding site of the enzyme, surrounding the catalytic amino acid Cys215 and the neighboring area or with the allosteric site of the enzyme, placed at a distance of 20 Å from the active site, around Phe280. However, the research continues for finding more potent inhibitors with increased cell permeability and specificity.

OBJECTIVE

The aim of this review is to show the attempts made in developing of Protein Tyrosine Phosphatase (PTP1b) inhibitors with high potency, selectivity and bioavailability and to sum up the indications for favorable structural characteristics of effective PTP1b inhibitors.

METHODS

The methods used include a literature survey and the use of Protein Structure Databanks such as PuBMed Structure and RCSB and the tools they provide.

CONCLUSION

The research for finding PTP1b inhibitors started with the design of molecules mimicking the Tyrosine substrate of the enzyme. The study revealed that an aromatic ring connected to a polar group, which preferably enables hydrogen bond formation, is the minimum requirement for small inhibitors binding to the active site surrounding Cys215. Molecules bearing two hydrogen bond donor/acceptor (Hb d/a) groups at a distance of 8.5-11.5 Å may form more stable complexes, interacting simultaneously with a secondary area A2. Longer molecules with two Hb d/a groups at a distance of 17 Å or 19 Å may enable additional interactions with secondary sites (B and C) that confer stability as well as specificity. An aromatic ring linked to polar or Hb d/a moieties is also required for allosteric inhibitors. A lower distance between Hb d/a moieties, around 7.5 Å may favor allosteric interaction. Permanent inhibition of the enzyme by oxidation of the catalytic Cys215 has also been referred. Moreover, covalent modification of Cys121, placed near but not inside the catalytic pocket has been associated with permanent inhibition of the enzyme.

Docking Assisted Prediction and Biological Evaluation of Sideritis L. Components with PTP1b Inhibitory Action and Probable Anti-Diabetic Properties

Background:

The main characteristic of Diabetes type II is the impaired activation of intracellular mechanisms triggered by the action of insulin. PTP1b is a Protein Tyrosine Phosphatase that dephosphorylates insulin receptor causing its desensitization. Since inhibition of PTP1b may prolong insulin receptor activity, PTP1b has become a drug target for the treatment of Diabetes II. Although a number of inhibitors have been synthesized during the last decades, the research still continues for the development of more effective and selective compounds. Moreover, several constituents of plants and edible algae with PTP1b inhibitory action have been found, adding this extra activity at the pallet of properties of the specific natural products.

Objective:

Sideritis L. (Lamiaceae) is a herbal plant growing around the Mediterranean sea which is included in the Mediterranean diet for centuries. The present study is the continuation of a previous work where the antioxidant and anti-inflammatory activities of the components of Sideritis L. were evaluated and aimed to investigate the potential of some sideritis’s components to act as PTP1b inhibitors, thus exhibiting the beneficial effect in the treatment of diabetes II.

Methods:

Docking analysis was done to predict PTP1b inhibitory action. Human recombinant PTP1b enzyme was used for the evaluation of the PTP1b inhibitory action, while inhibition of the human LAR and human T-cell PTP was tested for the estimation of the selectivity of the compounds.

Conclusion:

Docking analysis effectively predicted inhibition and mode of inhibitory action. According to the experimental results, four of the components exhibited PTP1b inhibitory action. The most active ones were acetoside, which acted as a competitive inhibitor, with an IC50 of 4 µM and lavandufolioside, which acted as an uncompetitive inhibitor, with an IC50 of 9.3 µM. All four compounds exhibited increased selectivity against PTP1b.

Benzofuran derivatives and their anti-tubercular, anti-bacterial activities

Benzofuran is a fundamental structural unit in a variety of biologically active natural products, and its derivatives display various biological properties. Some benzofuran derivatives possess unique anti-tubercular and anti-bacterial action mechanism, and exhibit excellent in vitro and in vivo activities against both drug-sensitive and drug-resistant pathogens. Moreover, several benzofuran derivatives have already used in clinics for the treatment of various diseases. Thus, benzofuran is a useful pharmacophore to develop new anti-tubercular and anti-bacterial drugs. This review covers the recent advances of benzofuran derivatives as potential anti-tubercular and anti-bacterial agents, and the structure-activity relationship is also discussed to pave the way for the further rational development of this kind of derivatives.

Benzofuran hydrazones as potential scaffold in the development of multifunctional drugs: Synthesis and evaluation of antioxidant, photoprotective and antiproliferative activity

New benzofuranhydrazones 3-12 were easily prepared and assayed for their radical-scavenging ability. Hydrazones 3-12 showed different extent antioxidant activity in DPPH, FRAP and ORAC assays. Good antioxidant activity is related to the number and position of hydroxyl groups on the arylidene moiety. High antioxidant activity is showed by the 2-hydroxy-4-(diethylamino)benzylidene derivative 11. Furthermore, hydrazones 3-12 showed photoprotective capacities with satisfactory in vitro SPF as compared to the commercial PBSA sunscreen filter. The antiproliferative effects of the hydrazones 3-12 was tested on erythroleukemia K562 and Colo-38 melanoma human cells. All the compounds showed growth inhibition in the micromolar to sub micromolar concentration range. If taken together these results points to benzofuran hydrazones as potential multifunctional molecules especially in the treatment of neoplastic diseases being the good antioxidant properties of 5, 7 and 11 correlated to their high antiproliferative activity.

Synthesis and in vitro study of benzofuran hydrazone derivatives as novel alpha-amylase inhibitor

The α-amylase acts as attractive target to treat type-2 diabetes mellitus. Therefore in discovering a small molecule as α-amylase inhibitor, we have synthesized benzofuran carbohydrazide analogs (1-25), characterized through different spectroscopic techniques such as 1HNMR and EI-MS. All screened analog shows good α-amylase inhibitory potentials with IC50 value ranging between 1.078±0.19 and 2.926±0.05µM when compared with acarbose having IC50=0.62±0.22µM. Only nine analogs among the series such as analogs 3, 5, 7, 8, 10, 12, 21, 23 and 24 exhibit good inhibitory potential with IC50 values 1.644±0.128, 1.078±0.19, 1.245±0.25, 1.843±0.19, 1.350±0.24, 1.629±0.015, 1.353±0.232, 1.359±0.119 and 1.488±0.07µM when compare with standard drug acarbose. All other analogs showed good to moderate α-amylase inhibitory potentials. The SAR study was conducted on the basis of substituent difference at the phenyl ring. The binding interaction between analogs and active site of enzyme was confirmed by docking studies.

A review on antioxidant potential of bioactive heterocycle benzofuran: Natural and synthetic derivatives

The majority of heterocycle compounds and typically common heterocycle fragments present in most pharmaceuticals currently marketed, alongside with their intrinsic versatility and unique physicochemical properties, have poised them as true cornerstones of medicinal chemistry. In this context, oxygen heterocycles exhibit diverse biological and pharmacological activities due in part to the similarities with many natural and synthetic molecules with known biological activity. Among oxygen containing heterocycles, benzofuran (synthetic and natural isolated) and its derivatives have attracted medicinal chemists and pharmacologists due to their pronounced biological activities and their potential applications as pharmacological agents such as antioxidant, antitumor, antiplatelet, antimalarial, antiinflammatory, antidepressant and anticonvulsant properties. There are also an amazing number of approved benzofuran-containing drugs in the market as well as compounds currently going through different clinical phases or registration statuses. Due to the wide range of biological activities of benzofurans, their structure activity relationships have generated interest among medicinal chemists, and this has culminated in the discovery of several lead molecules in numerous disease conditions. Recently, this scaffold has emerged as a pharmacophore of choice for designing antioxidant drug development as their derivatives have shown excellent results through different mechanism of action. This review focused on the recent development of benzofuran derivatives as antioxidant agents (including natural products) and their antioxidant activities; summarize the structure property, hoping to inspire new and even more creative approaches. Also, this study systematically provides a comprehensive report on current developments in benzofuran-based compounds as antioxidant agents and is also helpful for the researchers working on a substitution pattern around the nucleus, with an aim to help medicinal chemists to develop structure activity relationships (SAR) on these derivatives as antioxidant drugs.

Protein Tyrosine Phosphatases in Hypothalamic Insulin and Leptin Signaling

The hypothalamus is critical to the coordination of energy balance and glucose homeostasis. It responds to peripheral factors, such as insulin and leptin, that convey to the brain the degree of adiposity and the metabolic status of the organism. The development of leptin and insulin resistance in hypothalamic neurons appears to have a key role in the exacerbation of diet-induced obesity. In rodents, this has been attributed partly to the increased expression of the tyrosine phosphatases Protein Tyrosine Phosphatase 1B (PTP1B) and T cell protein tyrosine phosphatase (TCPTP), which attenuate leptin and insulin signaling. Deficiencies in PTP1B and TCPTP in the brain, or specific neurons, promote insulin and leptin signaling and prevent diet-induced obesity, type 2 diabetes mellitus (T2DM), and fatty liver disease. Although targeting phosphatases and hypothalamic circuits remains challenging, recent advances indicate that such hurdles might be overcome. Here, we focus on the roles of PTP1B and TCPTP in insulin and leptin signaling and explore their potential as therapeutic targets.

Mycobacterial Protein Tyrosine Phosphatases A and B Inhibitors Augment the Bactericidal Activity of the Standard Anti-tuberculosis Regimen

Novel drugs are required to shorten the duration of treatment for tuberculosis (TB) and to combat the emergence of drug resistance. One approach has been to identify and target Mycobacterium tuberculosis (Mtb) virulence factors, which promote the establishment of TB infection and pathogenesis. Mtb produces a number of virulence factors, including two protein tyrosine phosphatases (PTPs), mPTPA and mPTPB, to evade the antimicrobial functions of host macrophages. To assess the therapeutic potential of targeting the virulent Mtb PTPs, we developed highly potent and selective inhibitors of mPTPA (L335-M34) and mPTPB (L01-Z08) with drug-like properties. We tested the bactericidal activity of L335-M34 and L01-Z08 alone or together in combination with the standard antitubercular regimen of isoniazid-rifampicin-pyrazinamide (HRZ) in the guinea pig model of chronic TB infection, which faithfully recapitulates some of the key histological features of human TB lesions. Following a single dose of L335-M34 50mg/kg and L01-Z08 20 mg/kg, plasma levels were maintained at levels 10-fold greater than the biochemical IC₅₀ for 12-24 hours. Although neither PTP inhibitor alone significantly enhanced the antibacterial activity of HRZ, dual inhibition of mPTPA and mPTPB in combination with HRZ showed modest synergy, even after 2 weeks of treatment. After 6 weeks of treatment, the degree of lung inflammation correlated with the bactericidal activity of each drug regimen. This study highlights the potential utility of targeting Mtb virulence factors, and specifically the Mtb PTPs, as a strategy for enhancing the activity of standard anti-TB treatment.

Efficient Syntheses of 1,2,3-Triazoloamide Derivatives Using Solid- and Solution-Phase Synthetic Approaches

Efficient synthetic routes for the preparation of secondary and tertiary 1,2,3-triazoloamide derivatives were developed. A secondary α-1,2,3-triazoloamide library was constructed and expanded by a previously developed solid-phase synthetic route and a tertiary 1,2,3-triazoloamide library was constructed by a parallel solution-phase synthetic route. The synthetic routes rely on amide formation with secondary amines and chloro-acid chlorides; S_N2 reaction with sodium azide; and the selective [3 + 2] Hüisgen cycloaddition with appropriate terminal alkynes. The target secondary and tertiary 1,2,3-triazoloamide derivatives were obtained with three-diversity points in excellent overall yields and purities using the reported solid- and solution-phase synthetic routes, respectively.

Magnolia officinalis Extract Contains Potent Inhibitors against PTP1B and Attenuates Hyperglycemia in db/db Mice

Protein tyrosine phosphatase 1B (PTP1B) is an established therapeutic target for type 2 diabetes mellitus (T2DM) and obesity. The aim of this study was to investigate the inhibitory activity of Magnolia officinalis extract (ME) on PTP1B and its anti-T2DM effects. Inhibition assays and inhibition kinetics of ME were performed in vitro. 3T3-L1 adipocytes and C2C12 myotubes were stimulated with ME to explore its bioavailability in cell level. The in vivo studies were performed on db/db mice to probe its anti-T2DM effects. In the present study, ME inhibited PTP1B in a reversible competitive manner and displayed good selectivity against PTPs in vitro. Furthermore, ME enhanced tyrosine phosphorylation levels of cellular proteins, especially the insulin-induced tyrosine phosphorylations of insulin receptor β-subunit (IRβ) and ERK1/2 in a dose-dependent manner in stimulated 3T3-L1 adipocytes and C2C12 myotubes. Meanwhile, ME enhanced insulin-stimulated GLUT4 translocation. More importantly, there was a significant decrease in fasting plasma glucose level of db/db diabetic mice treated orally with 0.5 g/kg ME for 4 weeks. These findings indicated that improvement of insulin sensitivity and hypoglycemic effects of ME may be attributed to the inhibition of PTP1B. Thereby, we pioneered the inhibitory potential of ME targeted on PTP1B as anti-T2DM drug discovery.

Diversity-Oriented Synthesis for Novel, Selective and Drug-like Inhibitors for a Phosphatase from Mycobacterium Tuberculosis

Mycobacterium protein tyrosine phosphatase B (mPTPB) is a potential drug target of Tuberculosis (TB). Small molecule inhibitors of mPTPB could be a treatment to overcome emerging TB drug resistance. Using a Diversity-Oriented Synthesis (DOS) strategy, we successfully developed a salicylic acid based and drug-like mPTPB inhibitor with an IC50 of 2 μM and >20-fold specificity over many human PTPs, making it an excellent lead molecule for anti-TB drug discovery. In addition, DOS generated bicyclic salicylic acids are also promising starting points for acquiring inhibitors targeting other PTPs.

Protein tyrosine phosphatases as potential therapeutic targets

Protein tyrosine phosphorylation is a key regulatory process in virtually all aspects of cellular functions. Dysregulation of protein tyrosine phosphorylation is a major cause of human diseases, such as cancers, diabetes, autoimmune disorders, and neurological diseases. Indeed, protein tyrosine phosphorylation-mediated signaling events offer ample therapeutic targets, and drug discovery efforts to date have brought over two dozen kinase inhibitors to the clinic. Accordingly, protein tyrosine phosphatases (PTPs) are considered next-generation drug targets. For instance, PTP1B is a well-known targets of type 2 diabetes and obesity, and recent studies indicate that it is also a promising target for breast cancer. SHP2 is a bona-fide oncoprotein, mutations of which cause juvenile myelomonocytic leukemia, acute myeloid leukemia, and solid tumors. In addition, LYP is strongly associated with type 1 diabetes and many other autoimmune diseases. This review summarizes recent findings on several highly recognized PTP family drug targets, including PTP1B, Src homology phosphotyrosyl phosphatase 2(SHP2), lymphoid-specific tyrosine phosphatase (LYP), CD45, Fas associated phosphatase-1 (FAP-1), striatal enriched tyrosine phosphatases (STEP), mitogen-activated protein kinase/dual-specificity phosphatase 1 (MKP-1), phosphatases of regenerating liver-1 (PRL), low molecular weight PTPs (LMWPTP), and CDC25. Given that there are over 100 family members, we hope this review will serve as a road map for innovative drug discovery targeting PTPs.

Bidentate inhibitors of protein tyrosine phosphatases

SIGNIFICANCE

Protein tyrosine phosphatases (PTPs) are important enzymes that are involved in the regulation of cellular signaling. Evidence accumulated over the years has indicated that PTPs present exciting opportunities for drug discovery against diseases such as diabetes, cancer, autoimmune diseases, and tuberculosis. However, the highly conserved and partially positive charge of the catalytic sites of PTPs is a major challenge in the development of potent and highly selective PTP inhibitors.

RECENT ADVANCES

Here, we examine the strategy of developing bidentate inhibitors for selective inhibition of PTPs. Bidentate inhibitors are small-molecular-weight compounds with the ability to bind to both the active site and a non-conserved secondary phosphate binding site. This secondary phosphate binding site was initially discovered in protein tyrosine phosphatase 1B (PTP1B), and, hence, most of the bidentate inhibitors reported in this review are PTP1B inhibitors.

CRITICAL ISSUES

Although bidentate inhibition is a good strategy for developing potent and selective inhibitors, the cell membrane permeability and pharmacokinetic properties of the inhibitors are also important for successful drug development. In this review, we will also summarize the various efforts made toward the development of phosphotyrosine (pTyr) mimetics for increasing cellular permeability.

FUTURE DIRECTIONS

Even though the secondary phosphate binding site was initially found in PTP1B, structural data have shown that a secondary binding site can also be found in other PTPs, albeit with varying degrees of accessibility. Along with improvements in pTyr mimetics, we believe that the future will see an increase in the number of orally bioavailable bidentate inhibitors against the various classes of PTPs.

A potent and selective small-molecule inhibitor for the lymphoid-specific tyrosine phosphatase (LYP), a target associated with autoimmune diseases

Lymphoid-specific tyrosine phosphatase (LYP), a member of the protein tyrosine phosphatase (PTP) family of signaling enzymes, is associated with a broad spectrum of autoimmune diseases. Herein we describe our structure-based lead optimization efforts within a 6-hydroxy-benzofuran-5-carboxylic acid series culminating in the identification of compound 8b, a potent and selective inhibitor of LYP with a K(i) value of 110 nM and more than 9-fold selectivity over a large panel of PTPs. The structure of LYP in complex with 8b was obtained by X-ray crystallography, providing detailed information about the molecular recognition of small-molecule ligands binding LYP. Importantly, compound 8b possesses highly efficacious cellular activity in both T- and mast cells and is capable of blocking anaphylaxis in mice. Discovery of 8b establishes a starting point for the development of clinically useful LYP inhibitors for treating a wide range of autoimmune disorders.

Organocatalytic multicomponent reaction for the acquisition of a selective inhibitor of mPTPB, a virulence factor of tuberculosis

Mycobacterium protein tyrosine phosphatase B (mPTPB) is essential for the survival and persistence of Mycobacterium in the host. Thus small molecule inhibitors of mPTPB are potential anti-TB agents. We developed an efficient organocatalytic multicomponent reaction (MCR) between pyrrole, formaldehyde and aniline, affording a potent and selective mPTPB inhibitor with an IC(50) value of 1.5 μM and >50-fold specificity. Our studies provide a successful example of using organocatalysis as a discovery tool for the acquisition of PTP inhibitors.

Identification of a potent salicylic acid-based inhibitor of tyrosine phosphatase PTP1B

A screen of a library of diverse small-molecules against a subset of phosphatases identified 7b and 7c, which potently inhibit TC-PTP, PTPσ and PTP1B with no inhibition of PTP-LAR, PRL2 A/S, MKPX or papain.

Novel Agents and Emerging Strategies for Targeting the B-Cell Receptor Pathway in CLL

Chronic lymphocytic leukemia (CLL) is a disease of malignant CD5+ B lymphocytes that are characterized by frequent expression of autoreactive B-cell receptors (BCRs) and marked dependence on microenvironmental signals for proliferation and survival. Among the latter, signals propagated through the BCR are believed to play a key role in leukemia initiation, maintenance and evolution. Drugs that can disrupt these signals have recently emerged as potential therapeutic agents in CLL and several of them are currently being evaluated in clinical trials. Particularly promising clinical responses have been obtained with inhibitors of the kinases SYK, BTK, and PI3Kδ, which function by blocking BCR signal transduction. In addition, recent studies focusing on the phosphatase PTPN22, which is involved in the pathogenesis of multiple autoimmune diseases and is markedly overexpressed in CLL cells, suggest that it may be possible in the future to develop strategies that will selectively reprogram BCR survival signals into signals that induce leukemic cell death. This review focuses on the biological basis behind these strategies and highlights some of the most promising BCR-targeting agents in ongoing preclinical and clinical studies.

Small molecule tools for functional interrogation of protein tyrosine phosphatases

The importance of protein tyrosine phosphatases (PTPs) in the regulation of cellular signalling is well established. Malfunction of PTP activity is also known to be associated with cancer, metabolic syndromes and autoimmune disorders, as well as neurodegenerative and infectious diseases. However, a detailed understanding of the roles played by the PTPs in normal physiology and in pathogenic conditions has been hampered by the absence of PTP-specific small molecule agents. In addition, the therapeutic benefits of modulating this target class are underexplored as a result of a lack of suitable chemical probes. Potent and specific PTP inhibitors could significantly facilitate functional analysis of the PTPs in complex cellular signal transduction pathways and may constitute valuable therapeutics in the treatment of several human diseases. We highlight the current challenges to and opportunities for developing PTP-specific small molecule agents. We also review available selective small molecule inhibitors developed for a number of PTPs, including PTP1B, TC-PTP, SHP2, lymphoid-specific tyrosine phosphatase, haematopoietic protein tyrosine phosphatase, CD45, PTPβ, PTPγ, PTPRO, Vaccinia H1-related phosphatase, mitogen-activated protein kinase phosphatase-1, mitogen-activated protein kinase phosphatase-3, Cdc25, YopH, mPTPA and mPTPB.

Design, synthesis, and evaluation of 2-(arylsulfonyl)oxiranes as cell-permeable covalent inhibitors of protein tyrosine phosphatases

A structure-based design approach has been applied to develop 2-(arylsulfonyl)oxiranes as potential covalent inhibitors of protein tyrosine phosphatases. A detailed kinetic analysis of inactivation by these covalent inhibitors reveals that this class of compounds inhibits a panel of protein tyrosine phosphatases in a time- and dose-dependent manner, consistent with the covalent modification of the enzyme active site. An inactivation experiment in the presence of sodium arsenate, a known competitive inhibitor of protein tyrosine phosphatase, indicated that these inhibitors were active site bound. This finding is consistent with the mass spectrometric analysis of the covalently modified protein tyrosine phosphatase enzyme. Additional experiments indicated that these compounds remained inert toward other classes of arylphosphate-hydrolyzing enzymes, and alkaline and acid phosphatases. Cell-based experiments with human A549 lung cancer cell lines indicated that 2-(phenylsulfonyl)oxirane (1) caused an increase in intracellular pTyr levels in a dose-dependent manner thereby suggesting its cell-permeable nature. Taken together, the newly identified 2-(arylsulfonyl)oxiranyl moiety could serve as a novel chemotype for the development of activity-based probes and therapeutic agents against protein tyrosine phosphatase superfamily of enzymes.