Novel 7H-pyrrolo[2,3-d]pyrimidine derivatives as potent and orally active STAT6 inhibitors

Targeting Mast Cells in Allergic Disease: Current Therapies and Drug Repurposing

The incidence of allergic disease has grown tremendously in the past three generations. While current treatments are effective for some, there is considerable unmet need. Mast cells are critical effectors of allergic inflammation. Their secreted mediators and the receptors for these mediators have long been the target of allergy therapy. Recent drugs have moved a step earlier in mast cell activation, blocking IgE, IL-4, and IL-13 interactions with their receptors. In this review, we summarize the latest therapies targeting mast cells as well as new drugs in clinical trials. In addition, we offer support for repurposing FDA-approved drugs to target mast cells in new ways. With a multitude of highly selective drugs available for cancer, autoimmunity, and metabolic disorders, drug repurposing offers optimism for the future of allergy therapy.

The roles of post-translational modifications and coactivators of STAT6 signaling in tumor growth and progression

Signal transducers and activators of transcription 6 (STAT6) are highly expressed in various tumors and associated with tumorigenesis, immunosuppression, proliferation, metastasis and poor prognosis in human cancers. In response to IL-4/13, STAT6 is phosphorylated, dimerizes and triggers transcriptional regulation after recruitment of coactivators to transcriptosome, such as CBP/p300, SRC-1, PARP-14 and PSF. Post-translational modifications, including phosphorylation, ubiquitination, ADP-ribosylation and acetylation, have been explored for molecular mechanisms of STAT6 in tumor development and management. STAT6 has been developed as a specific biomarker for distinguishing and diagnosing tumor phenotypes, although it is observed to be frequently mutated in metastatic tumors. In this article, we focus mainly on the structural characteristics of STAT6 and its role in tumor growth and progression.

The fungal metabolite cyclonerodiol inhibits IL-4/IL-13 induced Stat6-signaling through blocking the association of Stat6 with p38, ERK1/2 and p300

The IL-4/IL-13/Stat6 pathway is the key driver of asthma pathophysiology. Therefore the development of inhibitors that specifically modulate IL-13/IL-4 or the downstream signaling molecules like Stat6 may be useful as a therapeutic strategy for the treatment of asthma and multiple allergic diseases. We have previously identified the fungal 2,6-cyclofarnesane cyclonerodiol as an inhibitor of IL-4 induced Stat6-dependent signaling in the alveolar epithelial cell line A549 using a transcriptional reporter. In this study we investigated the underlying mode of action of cyclonerodiol on the IL-4/IL-13/Stat6 pathway. Cyclonerodiol failed to interfere with activation, nuclear transport or binding of Stat6 to the corresponding consensus sequence on the DNA. Our results showed that cyclonerodiol blocked serine phosphorylation of Stat6 by affecting its association with p38 and Erk1/2. Cyclonerodiol also prevented the recruitment of the transcriptional coactivator p300 and Stat6 acetylation. These findings suggest that cyclonerodiol affects IL-4/IL-13 induced expression of asthma related marker genes by blocking transcriptional activation.

Synthesis of Pyrrolo[1,2-a]pyrimidine Enantiomers via Domino Ring-Closure followed by Retro Diels-Alder Protocol

From 2-aminonorbornene hydroxamic acids, a simple and efficient method for the preparation of pyrrolo[1,2-a]pyrimidine enantiomers is reported. The synthesis is based on domino ring-closure followed by microwave-induced retro Diels-Alder (RDA) protocols, where the chirality of the desired products is transferred from norbornene derivatives. The stereochemistry of the synthesized compounds was proven by X-ray crystallography. The absolute configuration of the product is determined by the configuration of the starting amino hydroxamic acid.

Synthesis of Non-Glutamate-Type Pyrrolo[2,3-d]Pyrimidines via Direct Aminocarbonylation of Aryl Halides Using Solid Co2(CO)8 as a CO Source and Their Antibacterial Activity

The synthesis of pyrrolo[2,3-d]pyrimidine derivatives by direct aminocarbonylation was demonstrated using solid Co2(CO)8 as a CO source in an autoclave at elevated temperature by reacting an aryl halide scaffold with a variety of amines. Using this method, 12 non-glutamate-type pyrrolo[2,3-d]pyrimidine analogues were prepared. Some compounds exhibited antibacterial activity against both Gram-positive and Gram-negative bacteria.

Molecularly targeted therapies for asthma: Current development, challenges and potential clinical translation

Extensive research into the therapeutics of asthma has yielded numerous effective interventions over the past few decades. However, adverse effects and ineffectiveness of most of these medications especially in the management of steroid resistant severe asthma necessitate the development of better medications. Numerous drug targets with inherent airway smooth muscle tone modulatory role have been identified for asthma therapy. This article reviews the latest understanding of underlying molecular aetiology of asthma towards design and development of better antiasthma drugs. New drug candidates with their putative targets that have shown promising results in the preclinical and/or clinical trials are summarised. Examples of these interventions include restoration of Th1/Th2 balance by the use of newly developed immunomodulators such as toll-like receptor-9 activators (CYT003-QbG10 and QAX-935). Clinical trials revealed the safety and effectiveness of chemoattractant receptor-homologous molecule expressed on Th2 cells (CRTH2) antagonists such as OC0000459, BI-671800 and ARRY-502 in the restoration of Th1/Th2 balance. Regulation of cytokine activity by the use of newly developed biologics such as benralizumab, reslizumab, mepolizumab, lebrikizumab, tralokinumab, dupilumab and brodalumab are at the stage of clinical development. Transcription factors are potential targets for asthma therapy, for example SB010, a GATA-3 DNAzyme is at its early stage of clinical trial. Other candidates such as inhibitors of Rho kinases (Fasudil and Y-27632), phosphodiesterase inhibitors (GSK256066, CHF 6001, roflumilast, RPL 554) and proteinase of activated receptor-2 (ENMD-1068) are also discussed. Preclinical results of blockade of calcium sensing receptor by the use of calcilytics such as calcitriol abrogates cardinal signs of asthma. Nevertheless, successful translation of promising preclinical data into clinically viable interventions remains a major challenge to the development of novel anti-asthmatics.

Targeting the JAK-STAT pathway in the treatment of 'Th2-high' severe asthma

Severe asthma is a heterogeneous disease characterized by reversible airway obstruction, chronic inflammation and airway remodeling. Phenotyping and/or endotyping can lead to a more personalized treatment strategy, improving the efficacy of novel drugs. Atopic asthma is associated with high levels of Th2 cells, implicated in a number of inflammatory responses. Differentiation of these cells from naive T cells occurs primarily via the JAK-STAT signaling pathway. Targeting this pathway through inhibition of activating cytokines (IL-4 and IL-13) and their receptors, the JAKs or the STATs, has been shown to have a therapeutic effect on asthma pathology. There are a number of novel drugs currently in development, which target various pathway components; these include both biologics and small molecules at various stages of development.

Targeting the Src Homology 2 (SH2) Domain of Signal Transducer and Activator of Transcription 6 (STAT6) with Cell-Permeable, Phosphatase-Stable Phosphopeptide Mimics Potently Inhibits Tyr641 Phosphorylation and Transcriptional Activity

Signal transducer and activator of transcription 6 (STAT6) transmits signals from cytokines IL-4 and IL-13 and is activated in allergic airway disease. We are developing phosphopeptide mimetics targeting the SH2 domain of STAT6 to block recruitment to phosphotyrosine residues on IL-4 or IL-13 receptors and subsequent Tyr641 phosphorylation to inhibit the expression of genes contributing to asthma. Structure-affinity relationship studies showed that phosphopeptides based on Tyr631 from IL-4Rα bind with weak affinity to STAT6, whereas replacing the pY+3 residue with simple aryl and alkyl amides resulted in affinities in the mid to low nM range. A set of phosphatase-stable, cell-permeable prodrug analogues inhibited cytokine-stimulated STAT6 phosphorylation in both Beas-2B human airway cells and primary mouse T-lymphocytes at concentrations as low as 100 nM. IL-13-stimulated expression of CCL26 (eotaxin-3) was inhibited in a dose-dependent manner, demonstrating that targeting the SH2 domain blocks both phosphorylation and transcriptional activity of STAT6.

Wheezing and itching: The requirement for STAT proteins in allergic inflammation

The development of allergic inflammation requires the orchestration of gene expression from the inflamed tissue and from the infiltrating immune cells. Since many of the cytokines that promote allergic inflammation signal through hematopoietin family receptors, the Signal Transducer and Activator of Transcription (STAT) family have obligate roles in pro-allergic cytokine-induced gene regulation in multiple cell types. In this review, we summarize work defining the contribution of each of the STAT family members to the development of allergic inflammation, using data from mouse models of allergic inflammation, studies on patient samples and correlations with single nucleotide polymorphisms in STAT genes.

Association of the STAT-6 rs324011 (C2892T) variant but not rs324015 (G2964A), with atopic asthma in a Saudi Arabian population

BACKGROUND

The signal transducer and activator of transcription 6 (STAT6) transduces signals in response to IL-4 and IL-13 cytokine stimulations, resulting in many cell-specific responses. Some common STAT6 SNPs were associated with asthma predisposition and/or IgE levels, although discrepancies have also been reported.

OBJECTIVE

To determine whether STAT6 rs324011 and rs324015 polymorphisms are associated with atopic asthma in Saudi Arabian patients.

METHODS

A total of 536 Saudi individuals aged 11-70years old (230 atopic asthmatics, 306 healthy subjects) were recruited. DNA was purified from peripheral blood and genotyping for rs324011 and rs324015 polymorphisms was performed by PCR amplification, followed by cycle sequencing of the purified PCR fragments using BigDye chain terminator and capillary electrophoresis.

RESULTS

By the contrast of alleles tests, no significant differences between asthma and healthy groups were detected for both variants (rs324011: X(2)=0.25, Pearson's P-value=0.617; rs324015: X(2)=0.068, Pearson's P=0.814).When testing for genotypes, rs324011 homozygous T/T genotype was significantly associated with asthma, when the Recessive model is considered (T/T vs. C/C+C/T) (adjusted, OR=2.49, 95% CI=1.18-5.25, Pearson's P=0.014(∗), Yates' P=0.022(∗)). In contrast, rs324015 variant was not significantly associated with asthma.

CONCLUSIONS

Rs324011 homozygous T/T genotype was significantly associated with asthma risk whereas rs324015 genotypes were not in the Saudi population.

Therapeutic modulators of STAT signalling for human diseases

The signal transducer and activator of transcription (STAT) proteins have important roles in biological processes. The abnormal activation of STAT signalling pathways is also implicated in many human diseases, including cancer, autoimmune diseases, rheumatoid arthritis, asthma and diabetes. Over a decade has passed since the first inhibitor of a STAT protein was reported and efforts to discover modulators of STAT signalling as therapeutics continue. This Review discusses the outcomes of the ongoing drug discovery research endeavours against STAT proteins, provides perspectives on new directions for accelerating the discovery of drug candidates, and highlights the noteworthy candidate therapeutics that have progressed to clinical trials.

An IL-4/IL-13 dual antagonist reduces lung inflammation, airway hyperresponsiveness, and IgE production in mice

IL-4 and IL-13 comprise promising targets for therapeutic interventions in asthma and other Th2-associated diseases, but agents targeting either IL-4 or IL-13 alone have shown limited efficacy in human clinical studies. Because these cytokines may involve redundant function, dual targeting holds promise for achieving greater efficacy. We describe a bifunctional therapeutic targeting IL-4 and IL-13, developed by a combination of specific binding domains. IL-4-targeted and IL-13-targeted single chain variable fragments were joined in an optimal configuration, using appropriate linker regions on a novel protein scaffold. The bifunctional IL-4/IL-13 antagonist displayed high affinity for both cytokines. It was a potent and efficient neutralizer of both murine IL-4 and murine IL-13 bioactivity in cytokine-responsive Ba/F3 cells, and exhibited a half-life of approximately 4.7 days in mice. In a murine model of ovalbumin-induced ear swelling, the bifunctional molecule blocked both the IL-4/IL-13-dependent early-phase response and the IL-4-dependent late-phase response. In the ovalbumin-induced lung inflammation model, the bifunctional IL-4/IL-13 antagonist reduced the IL-4-dependent rise in serum IgE titers, and reduced IL-13-dependent airway hyperresponsiveness, lung inflammation, mucin gene expression, and serum chitinase responses. Taken together, these findings demonstrate the effective dual blockade of IL-4 and IL-13 with a single agent, which resulted in the modulation of a more extensive range of endpoints than could be achieved by targeting either cytokine alone.

Identifying and testing potential new anti-asthma agents

INTRODUCTION

Inhaled corticosteroids alone or with long-acting beta-2 agonists (LABA) are the basic treatment for stable asthma. While the majority of patients are controllable, some patients retain chronic severe disease and develop permanent alterations in airway function. For patients such as these it is important to better understand the mechanisms of asthma so that alternative approaches can be developed.

AREA COVERED

Based on data from in vitro cell culture, animal models and clinical trials, this review discusses potential agents targeting either key effector cells, mediators and their receptors in asthma pathogenesis or their signaling cascade molecules.

EXPERT OPINION

As targeting single Th2 cytokines and their receptors has been shown to have limited clinical benefit, it is important to identify and test potential new therapeutic agents. Recent studies suggest that blockade of IgE synthesis, its interaction with its receptors and downstream signaling, identification of molecular targets in innate immune and airways structural cells, and fresh anti-neutrophil strategies should be prominent among these. Further studies are required to clarify the relationship between airways remodeling and asthma severity so that appropriate patients may be targeted.