JTE-852, a novel spleen tyrosine kinase inhibitor, blocks mediator secretion from mast cells with immunoglobulin E crosslinking

Research Advances in Mast Cell Biology and Their Translation Into Novel Therapies for Anaphylaxis

Anaphylaxis is an acute, potentially life-threatening systemic allergic reaction for which there are no known reliable preventative therapies. Its primary cell mediator, the mast cell, has several pathophysiologic roles and functions in IgE-mediated reactions that continue to be poorly understood. Recent advances in the understanding of allergic mechanisms have identified novel targets for inhibiting mast cell function and activation. The prevention of anaphylaxis is within reach with new drugs that could modulate immune tolerance, mast cell proliferation and differentiation, and IgE regulation and production. Several US Food and Drug Administration-approved drugs for chronic urticaria, mastocytosis, and cancer are also being repurposed to prevent anaphylaxis. New therapeutics have not only shown promise in potential efficacy for preventing IgE-mediated reactions, but in some cases, they are able to inform us about mast cell mechanisms in vivo. This review summarizes the most recent advances in the treatment of anaphylaxis that have arisen from new pharmacologic tools and our current understanding of mast cell biology.

Selected recent advances in understanding the role of human mast cells in health and disease

Mast cells are highly granular tissue-resident cells and key drivers of inflammation, particularly in allergies as well as in other inflammatory diseases. Most mast cell research was initially conducted in rodents but has increasingly shifted to the human system, with the advancement of research technologies and methodologies. Today we can analyze primary human cells including rare subpopulations, we can produce and maintain mast cells isolated from human tissues, and there are several human mast cell lines. These tools have substantially facilitated our understanding of their role and function in different organs in both health and disease. We can now define more clearly where human mast cells originate from, how they develop, which mediators they store, produce de novo, and release, how they are activated and by which receptors, and which neighbouring cells they interact with and by which mechanisms. Considerable progress has also been made regarding the potential contribution of mast cells to disease, which, in turn, has led to the development of novel approaches for preventing key pathogenic effects of mast cells, heralding the era of mast cell-targeted therapeutics. In this review, we present and discuss a selection of some of the most significant advancements and remaining gaps in our understanding of human mast cells during the last 25 years, with a focus on clinical relevance.

Targeting the FcεRI Pathway as a Potential Strategy to Prevent Food-Induced Anaphylaxis

Despite attempts to halt it, the prevalence of food allergy is increasing, and there is an unmet need for strategies to prevent morbidity and mortality from food-induced allergic reactions. There are no known medications that can prevent anaphylaxis, but several novel therapies show promise for the prevention of food-induced anaphylaxis through targeting of the high-affinity IgE receptor (FcϵRI) pathway. This pathway includes multiple candidate targets, including tyrosine kinases and the receptor itself. Small molecule inhibitors of essential kinases have rapid onset of action and transient efficacy, which may be beneficial for short-term use for immunotherapy buildup or desensitizations. Short courses of FDA-approved inhibitors of Bruton’s tyrosine kinase can eliminate IgE-mediated basophil activation and reduce food skin test size in allergic adults, and prevent IgE-mediated anaphylaxis in humanized mice. In contrast, biologics may provide longer-lasting protection, albeit with slower onset. Omalizumab is an anti-IgE antibody that sequesters IgE, thereby reducing FcϵRI expression on mast cells and basophils. As a monotherapy, it can increase the clinical threshold dose of food allergen, and when used as an adjunct for food immunotherapy, it decreases severe reactions during buildup phase. Finally, lirentelimab, an anti-Siglec-8 antibody currently in clinical trials, can prevent IgE-mediated anaphylaxis in mice through mast cell inhibition. This review discusses these and other emerging therapies as potential strategies for preventing food-induced anaphylaxis. In contrast to other food allergy treatments which largely focus on individual allergens, blockade of the FcϵRI pathway has the advantage of preventing clinical reactivity from any food.

Tetrandrine attenuates the bone erosion in collagen-induced arthritis rats by inhibiting osteoclastogenesis via spleen tyrosine kinase

Tetrandrine, a bisbenzylisoquinoline alkaloid, was previously demonstrated to attenuate inflammation and cartilage destruction in the ankles of mice with collagen-induced arthritis (CIA). Here, we explored the underlying mechanism by which tetrandrine prevented arthritis-induced bone erosion by focusing on the differentiation and function of osteoclasts. We found that daily administration of tetrandrine (30 mg/kg) markedly reduced the bone damage and decreased the number of osteoclasts in CIA rats. In vitro, tetrandrine inhibited receptor activator of NF-κB ligand (RANKL)-induced osteoclastogenesis at the early stage and reduced the expressions of osteoclast-related marker genes. In bone marrow-derived macrophages and RAW264.7 cells, tetrandrine inhibited RANKL-induced translocation of NF-κB-p65 and nuclear factor of activated T cell 1 (NFATc1) through suppressing spleen tyrosine kinase (Syk)-Bruton's tyrosine kinase-PLCγ2-Ca²⁺ signaling. Of interest, tetrandrine did not affect the phosphorylation of immunoreceptor tyrosine-based activation motifs, the conventional upstream of Syk, but it inhibited the activity of Syk by enhancing its ubiquitination and degradation. The anti-osteoclastogenesis effect of tetrandrine nearly disappeared when it was used in combination with the Syk inhibitor piceatannol or in constitutively activated Syk-overexpressing cells. Taken together, tetrandrine attenuated CIA-induced bone destruction by inhibiting osteoclastogenesis through hindering the translocation of NF-κB-p65 and NFATc1 via reducing the activation of Syk.-Jia, Y., Miao, Y., Yue, M., Shu, M., Wei, Z., Dai, Y. Tetrandrine attenuates the bone erosion in collagen-induced arthritis rats by inhibiting osteoclastogenesis via spleen tyrosine kinase.

JTE-852, a novel spleen tyrosine kinase inhibitor, blocks antigen-induced allergic reactions in rats

Conventional clinical treatments for allergy management remain suboptimal; new, orally available medications that improve a wide range of allergic signs have been desired. We previously demonstrated that JTE-852, a novel spleen tyrosine kinase inhibitor, potently and simultaneously suppresses secretion of granule contents, arachidonate metabolites, and cytokines from mast cells stimulated by immunoglobulin E-crosslinking. In the present study, we investigated the effects of JTE-852 in four rat models (sneezing, rhinorrhea, airway constriction, and airway inflammation) as representatives of allergy models. Rats were sensitized and challenged with antigen. Allergic reactions developed after challenge were detected. JTE-852 and current anti-allergic drugs (ketotifen, pranlukast, and prednisolone) were administered orally before challenge. JTE-852 showed significant blocking effects on antigen-induced allergic reactions in all models, indicating that JTE-852 in oral dosage form would improve a wide range of allergic signs. The current anti-allergic drugs, on the other hand, failed to display significant suppression in several models. Because JTE-852 suppresses the secretion of all three groups of allergic mediators from mast cells, it would be capable of targeting signs that current drugs cannot sufficiently relieve. We anticipate JTE-852 to be a promising new anti-allergic drug that is potentially more effective than conventional drugs.

JTE-852, a novel spleen tyrosine kinase inhibitor, blocks immunoglobulin G-mediated cellular responses and autoimmune reactions in vivo

AIMS

Immune and inflammatory responses mediated by immunoglobulin (Ig) G are largely responsible for the pathogenesis of autoimmune diseases. Spleen tyrosine kinase (Syk) plays a pivotal role in the IgG-mediated responses; therefore, Syk has emerged as a new therapeutic target for the treatment of autoimmune diseases. In this study, we investigated the inhibitory actions of JTE-852, a novel Syk inhibitor, on IgG-mediated cellular responses and autoimmune reactions in vivo.

MAIN METHODS

We examined mediator secretion from human monocytes. We also conducted rat models of reversed cutaneous anaphylaxis (RCA) and reversed passive Arthus (RPA), which are classified as type II and type III hypersensitivities, respectively. In a rat collagen-induced arthritis (CIA) model, JTE-852 or methotrexate was administered preventively (before the onset of arthritis) or therapeutically (after the onset of arthritis).

KEY FINDINGS

JTE-852 blocked secretion of reactive oxygen species and tumor necrosis factor-α from monocytes stimulated by IgG crosslinking. In the RCA and RPA models, JTE-852 also suppressed edema and dye leakage, respectively. In the CIA model, JTE-852 showed both preventive and therapeutic effects against joint swelling and bone erosion; on the other hand, methotrexate did not show the therapeutic effect.

SIGNIFICANCE

JTE-852 attenuates IgG-mediated responses and signs in animal model of autoimmune diseases. JTE-852 is thus a promising candidate for a novel, orally available drug for the treatment of autoimmune diseases.

New and emerging targeted systemic therapies: a new era for atopic dermatitis

PURPOSE

This is a review of emerging targeted, systemic therapies for atopic dermatitis (AD). The information presented aims to provide dermatologists with updated therapeutic options, stimulate academic interest, and spark future research.

MATERIAL AND METHODS

Extensive search of ClinicalTrials.gov, the National Eczema Association, and PubMed was performed for clinical trials examining the effect of emerging targeted, systemic therapies in patients with AD. Results were included if they demonstrated efficacy in reversing AD symptoms. Studies that did not demonstrate clinical benefit were excluded.

RESULTS

A number of emerging systemic agents targeting specific mediators involved in the pathogenesis of AD were found. These targets include IL-4, IL-13, IgE, B-cells, IL-5, IL-31, JAK-STAT, SYK, IL-6, PDE-4, IL-12, IL-17, IL-23, IL-22, H4R, NKR1, κOR, TSLP, PPAR-γ, and DGLA. Treatment of AD patients with these therapies has, in many cases, led to statistically significant improvements in clinical severity scores and patient-reported outcomes.

CONCLUSIONS

While multiple agents have demonstrated efficacy, only dupilumab is currently approved for adults with AD. Large-scale, randomized, placebo-controlled, double-blind trials, especially in children, are needed. As we enter the dawn of targeted therapy for AD, a comprehensive clinical trial registry is needed to facilitate data pooling and comparison among international registries.