Lirentelimab for severe and chronic forms of allergic conjunctivitis

Updates in immunomodulator therapy in ocular surface inflammatory diseases

PURPOSE OF REVIEW

Ocular surface inflammatory disorders (OSIDs), including allergic conjunctivitis, ocular graft-versus-host disease (oGVHD), and cicatrizing conjunctivitis, present significant clinical challenges due to complex immune modulation. Traditional therapies like corticosteroids have limitations, prompting the need for alternative treatments. This review explores novel, steroid-sparing immunomodulatory options.

RECENT FINDINGS

In recent years, immunomodulatory therapies have evolved from corticosteroids and broad-spectrum T-cell inhibitors such as cyclosporine and tacrolimus to more selective pathway-targeting agents like JAK inhibitors (e.g., ruxolitinib). Biologic agents, including dupilumab and upadacitinib, have demonstrated efficacy in severe allergic conjunctivitis. In oGVHD, JAK inhibitors and combination therapies are emerging as promising strategies. For cicatrizing conjunctivitis, rituximab and IVIg have shown encouraging outcomes. Additionally, novel therapeutic targets such as chemokine receptor blockers (e.g., CCL20 locked dimer), T regulatory cell (Treg) modulation, and transcriptional modification via micro-RNA are shaping the future of ocular surface disease management.

SUMMARY

The future of immunomodulatory therapy for ocular surface diseases lies in refining current treatment approaches and advancing targeted biologic agents that modulate specific immune pathways, offering improved efficacy and safety for patients with these sight-threatening conditions.

Enhanced Siglec-8 and HLA-DR and reduced CRTH2 surface expression highlight a distinct phenotypic signature of circulating eosinophils in atopic dermatitis

Atopic dermatitis and other type 2 immune response diseases are often linked to elevated eosinophil levels in the blood. Although the role of eosinophils in atopic dermatitis pathophysiology is suspected, it remains unclear. The development of new treatments targeting the type 2 response, particularly cytokines involved in eosinophil activation and chemotaxis, makes it necessary to identify potential eosinophil profiles in atopic dermatitis that may respond to these treatments. A prospective study was conducted comparing blood eosinophil phenotypes in patients with moderate to severe atopic dermatitis (n = 19) without recent systemic treatment to healthy individuals (n = 19). The primary outcome was the membranous phenotypic signature of eosinophils, assessed by flow cytometry. Most patients with atopic dermatitis (84%) had early onset in childhood, a severe disease (mean SCORing Atopic Dermatitis of 57.5), and elevated blood eosinophil counts (310 per µL in atopic dermatitis vs 120 in healthy individuals, P < 0.0001). Patients with atopic dermatitis exhibited lower CRTH2 on eosinophils but higher levels of human leukocyte antigen-DR isotype and Siglec-8 compared to healthy individuals. Other surface proteins showed no significant differences. Clustering analysis confirmed increased Siglec-8 in patients with atopic dermatitis. Additionally, patients with atopic dermatitis had higher serum levels of type 2 immune response markers such as eotaxin-2, IL-5, IL-3, and TARC. Circulating eosinophils in patients with atopic dermatitis show a distinct phenotypic profile, suggesting a role in atopic dermatitis pathophysiology and potential involvement in differential treatment responses.

Monoclonal antibodies in phase II and III trials for moderate to severe atopic dermatitis

INTRODUCTION

Atopic dermatitis (AD) is a prevalent chronic inflammatory skin disease that significantly affects quality of life and mental health, especially in children. Traditional treatments include chemotherapeutics, topical corticosteroids, and immunomodulatory agents, but recent advances have introduced novel monoclonal antibody therapies. Through this comprehensive review paper, we aim to discuss these therapeutic options and their role in treating atopic dermatitis.

AREAS COVERED

A comprehensive search of the NIH Clinical Trials database was conducted from September 2023 to January 2024, focusing on phase 2 and 3 trials for AD treatments. Trials were filtered using keywords such as 'atopic dermatitis,' 'monoclonal antibody,' and 'phase 2/3.' Out of 25 trials analyzed, 11 were in phase 2 and 14 in phase 3. Only U.S.-based trials comparing novel therapies to placebo were included. In addition to the clinical trial database, we utilized the companies' websites and relevant abstracts to gather the latest results.

EXPERT OPINION

Currently investigated monoclonal antibodies have the ability to transform management by targeting specific mediators implicated in the inflammatory pathway of AD. The results of Phase II and III trials for monoclonal antibodies demonstrated strong therapeutic potential with significant reductions in EASI scores and represent a promising new targeted treatment option.

Optimizing Siglec-8-Directed Immunotherapy for Eosinophilic and Mast Cell Disorders

Background/Objective: Current treatments for eosinophilic and mast cell disorders are often ineffective. One promising target to improve outcomes is sialic acid-binding immunoglobulin-like lectin-8 (Siglec-8). As limitations, there are few Siglec-8 monoclonal antibodies (mAbs) available to date, and Siglec-8-directed treatments have so far primarily focused on unconjugated mAbs, which may be inadequate, especially against mast cells. Methods: Here, we used transgenic mice to raise a diverse panel of fully human mAbs that either recognize the V-set domain, membrane-distal C2-set domain, or membrane-proximal C2-set domain of full-length Siglec-8 as a basis for novel therapeutics. Results: All mAbs were efficiently internalized into Siglec-8-expressing cells, suggesting their potential to deliver cytotoxic payloads. Tool T cell-engaging bispecific antibodies (BiAbs) and chimeric antigen receptor (CAR)-modified natural killer (NK) cells using single-chain variable fragments from Siglec-8 mAbs showed highly potent cytolytic activity against Siglec-8-positive cells even in cases of very low target antigen abundance, whereas they elicited no cytolytic activity against Siglec-8-negative target cells. Siglec-8V-set-directed T cell-engaging BiAbs and Siglec-8V-set-directed CAR-modified NK cells induced substantially greater cytotoxicity against cells expressing an artificial smaller Siglec-8 variant containing only the V-set domain than cells expressing full-length Siglec-8, consistent with the notion that targeting membrane-proximal epitopes enhances effector functions of Siglec-8 antibody-based therapeutics. Indeed, unconjugated Siglec-8C2-set mAbs, Siglec-8C2-set-directed T cell-engaging BiAbs, and Siglec-8C2-set-directed CAR-modified NK cells showed high antigen-specific cytolytic activity against Siglec-8-positive human cell lines and primary patient eosinophils. Conclusions: Together, these data demonstrate Siglec-8-directed immunotherapies can be highly potent, supporting their further development for eosinophilic and mast cell disorders.

Novel therapeutic receptor agonists and antagonists in allergic conjunctivitis

PURPOSE OF REVIEW

Allergic conjunctivitis is characterized by the development of pathophysiological changes to the ocular surface, which occurs when pro-allergic and pro-inflammatory mediators interact with their cognate receptors expressed on immune and nonimmune cells. Traditional treatments with antihistamines and corticosteroids provide relief, but there is a need for more efficacious and tolerable long-term therapy with a better safety profile. This article aims to provide an overview of the mode of action and clinical application of agonist therapies targeting glucocorticoid, melanocortin, and toll-like receptors, as well as antagonist therapies targeting cytokine, chemokine, integrin, and histamine receptors.

RECENT FINDINGS

There has been considerable advancement in immunology and pharmacology, as well as a greater understanding of the cellular and molecular mechanisms of allergic conjunctivitis. Recent research advancing therapy for allergic conjunctivitis has focused on developing synthetic molecules and biologics that can interfere with the process of the allergic immune reaction.

SUMMARY

This review discusses novel therapeutic receptors being explored agonistically or antagonistically to develop alternative treatment options for allergic conjunctivitis. These novel approaches hold promise for improving the management of allergic eye diseases, offering patients hope for more effective and safer treatment options in the future.

Eosinophilic esophagitis and inhalant antigens: Pointing out the roles of allergic rhinitis, immunotherapy and biologic treatment

Eosinophilic esophagitis (EoE) and allergic rhinitis (AR) usually represent the latest manifestations of the atopic march, sharing a common type 2 inflammation response. A relevant prevalence of AR in EoE cohorts has been widely confirmed. An increasing literature assessed the involvement of aeroantigens in EoE pathogenesis, focusing foremost on the seasonality of new diagnoses, symptoms, and response to therapy. Unfortunately, no diriment direction has been achieved, probably due to the retrospective design of the studies so far available, which chose surrogate markers of EoE activity (mostly the date of new diagnosis) which may be affected by geographical, logistic and personal factors, probably not dependent by the disease itself. EoE exacerbations reported in the context of the pollen levels (preferably pollen counts) may represent a more reliable marker. AR might promote the onset and the re-exacerbation of EoE through mechanisms that are both local (ie, massive exposure to airborne antigens mediated by post-nasal drip) and systemic (type 2 inflammation). Furthermore, AR may facilitate EoE onset by predisposing to pollen food allergic syndrome (PFAS), and EoE patients with PFAS reported higher rate of AR, thus suggesting a bond among these 3 conditions whose causative relationship have still to be ascertained. In addition, because of its shifting activity from Th2 to Th1 inflammation, several case reports focused on the effect of allergen immunotherapy (AIT) employed to treat AR in EoE patients. Also in this instance, no certainties could be guaranteed, although sublingual immunotherapy (SLIT) is more frequently reported to exacerbate EoE, while SCIT is mostly described as a remission adjuvant. The real life experience reported from our allergy service appears to confirm such hypothesis. Finally, a watchful eye should be reserved to monoclonal antibodies as a potential future option for concomitant EoE and AR. In light of all this, an attentive evaluation of allergic history of EoE patients should be relevant. Future perspectives should be addressed on prospective studies targeted to shed light on causative relations among airborne antigens, AR and EoE, and to viable comprehensive treatments.

Unraveling the complexity - Insights and interventions of refractory vernal keratoconjunctivitis

Vernal keratoconjunctivitis (VKC) is a chronic severe ocular allergic inflammation mostly observed in children and young adults. The ocular manifestations are the expression of multifactorial immune mechanisms that generally have a good prognosis, however long-term inflammation may remarkably reduce the visual function due to complications and poor therapeutic responses. Lack of responsiveness to a drug or treatment is relatively common in VKC and it is not only due to corneal involvement, which is considered the main sign of severity. The concept of refractory may be relative to multiple factors including the clinical condition, systemic co-morbidities, previous or concomitant drugs or regiments, compliance, patient's psychological condition or expectations, type of exposome and environmental conditions, doctor's experience and expectations, or timing of clinical evaluation. In this narrative review, the authors propose a definition of refractory VKC based on revised literature and clinical experience and consider potential new treatments for refractory patients and surgical management in case of complications.

Approach to the patient with eosinophilia in the era of tyrosine kinase inhibitors and biologicals

PURPOSE OF REVIEW

In this review, we aim to explore the optimal approach to patients presenting with eosinophilia, considering recent advances in diagnostic and therapeutic strategies. Specifically, we focus on the integration of novel therapies into clinical practice to improve patient outcomes.

RECENT FINDINGS

Advanced insights into the clinical and genetic features of eosinophilic disorders have prompted revisions in diagnostic criteria by the World Health Organization classification (WHO-HAEM5) and the International Consensus Classification (ICC). These changes reflect a growing understanding of disease pathogenesis and the development of targeted treatment options. The therapeutic landscape now encompasses a range of established and novel therapies. For reactive conditions, drugs targeting the eosinophilopoiesis, such as those aimed at interleukin-5 or its receptor, have demonstrated significant potential in decreasing blood eosinophil levels and minimizing disease flare-ups and relapse. These therapies have the potential to mitigate the side effects commonly associated with prolonged use of oral corticosteroids or immunosuppressants. Myeloid and lymphoid neoplasms with eosinophilia and tyrosine kinase (TK) gene fusions are managed by various TK inhibitors with variable efficacy. Diagnosis and treatment rely on a multidisciplinary approach. By incorporating novel treatment options into clinical practice, physicians across different disciplines involved in the management of eosinophilic disorders can offer more personalized and effective care to patients. However, challenges remain in accurately diagnosing and risk-stratifying patients, as well as in navigating the complexities of treatment selection.

Development of a Temperature and pH Dual-Sensitive In-Situ Gel for Treating Allergic Conjunctivitis

The purpose of this study was to improve the efficacy of olopatadine hydrochloride (OT) in treating allergic conjunctivitis (AC). To achieve this goal, we developed an eye formulation without antimicrobial agents using a temperature-pH dual-sensitive in situ gel technology combined with heat sterilization. Various types of carbomers were evaluated and their optimal doses determined. The prescription containing poloxamer 407 (P407) and poloxamer 188 (P188) was optimized using central composite design for response surface methodology (CCD-RSM). The final optimized dual-sensitive in situ gel (TP-gel) consisted of 0.1% olopatadine hydrochloride, 18.80% P407, 0.40% P188, 0.30% Pemulen™TR-1(TR-1), 4.0% mannitol, and 0.08% Tri(hydroxymethyl)aminomethane(Tris).Sterilization was performed at a temperature of 121℃ for a duration of 20 min. Experimental results showed that TP-gel had good safety profile and remained on the ocular surface for approximately (65.83 ± 8.79) minutes, which is four times longer than eye drops. The expression levels of IL-13, IL-17, and OVA-IgE in mouse ocular tissues with allergic conjunctivitis treated with TP-gel were significantly reduced. This suggests that TP-gel has the potential to be an effective treatment method for allergic conjunctivitis.

Mast cells and the gut-liver Axis: Implications for liver disease progression and therapy

The role of mast cells, traditionally recognized for their involvement in immediate hypersensitivity reactions, has garnered significant attention in liver diseases. Studies have indicated a notable increase in mast cell counts following hepatic injury, underscoring their potential contribution to liver disorder pathogenesis. Predominantly situated in connective tissue that envelops the hepatic veins, bile ducts, and arteries, mast cells are central to both initiating and perpetuating liver disorders. Additionally, they are crucial for maintaining gastrointestinal barrier function. The gut-liver axis emphasizes the complex, two-way communication between the gut microbiome and the liver. Past research has implicated gut microbiota and their metabolites in the progression of hepatic disorders. This review sheds light on how mast cells are activated in various liver conditions such as alcoholic liver disease (ALD), non-alcoholic fatty liver disease (NAFLD), viral hepatitis, hepatic fibrogenesis, and hepatocellular carcinoma. It also briefly explores the connection between the gut microbiome and mast cell activation in these hepatic conditions.

Vectorized Human Antibody-Mediated Anti-Eosinophil Gene Therapy

Chronic hypereosinophilia, defined as persistent elevated blood levels of eosinophils ≥1,500/μL, is associated with tissue infiltration of eosinophils and consequent organ damage by eosinophil release of toxic mediators. The current therapies for chronic hypereosinophilia have limited success, require repetitive administration, and are associated with a variety of adverse effects. As a novel approach to treat chronic hypereosinophilia, we hypothesized that adeno-associated virus (AAV)-mediated delivery of an anti-human eosinophil antibody would provide one-time therapy that would mediate persistent suppression of blood eosinophil levels. To assess this hypothesis, we first generated a human monoclonal antibody (mAb) directed against Siglec8, a sialic-acid binding immunoglobulin-like lectin, expressed at high levels on the cell surface of human eosinophils. Transgenic mice with a human immunoglobulin repertoire were immunized with human Siglec8 protein or DNA encoding human Siglec8. Based on target binding assessments, the 08C07 mAb was chosen for further study. The human variable regions of 08C07 were joined to the human Ig constant region, creating H08C07 (hAntiEos), a fully human anti-human eosinophil mAb. Using the gene sequence of hAntiEos, we created AAVrh.10hAntiEos, an AAVrh.10-based vector expressing the heavy and light chains of H08C07. Intravenous administration of AAVrh.10hAntiEos (1011 genome copies or gc) to C57Bl/6 mice resulted in persistent elevated serum levels of hAntiEos. In vivo gene therapy generated hAntiEos bound to recombinant human Siglec8 protein in a dose-dependent manner and to human eosinophils, mediated apoptosis of human eosinophils, and antibody-dependent cellular cytotoxicity activity against human eosinophils. Consistent with these data, administration of AAVrh.10hAntiEos to human CD34+ transplanted NSG-SGM3 immunodeficient mice suppressed levels of human eosinophils in vivo. AAVrh.10hAntiEos holds the potential to offer therapeutic benefit to patients with chronic hypereosinophilia.

Mast cell silencing: A novel therapeutic approach for urticaria and other mast cell-mediated diseases

Chronic urticaria (CU) is a mast cell (MC)-dependent disease with limited therapeutic options. Current management strategies are directed at inhibiting IgE-mediated activation of MCs and antagonizing effects of released mediators. Due to the complexity and heterogeneity of CU and other MC diseases and mechanisms of MC activation-including multiple activating receptors and ligands, diverse signaling pathways, and a menagerie of mediators-strategies of MC depletion or MC silencing (i.e., inhibition of MC activation via binding of inhibitory receptors) have been developed to overcome limitations of singularly targeted agents. MC silencers, such as agonist monoclonal antibodies that engage inhibitory receptors (e.g., sialic acid-binding immunoglobulin-like lectin8 -[Siglec-8] [lirentelimab/AK002], Siglec-6 [AK006], and CD200R [LY3454738]), have reached preclinical and clinical stages of development. In this review, we (1) describe the role of MCs in the pathogenesis of CU, highlighting similarities with other MC diseases in disease mechanisms and response to treatment; (2) explore current therapeutic strategies, categorized by nonspecific immunosuppression, targeted inhibition of MC activation or mediators, and targeted modulation of MC activity; and (3) introduce the concept of MC silencing as an emerging strategy that could selectively block activation of MCs without eliciting or exacerbating on- or off-target, immunosuppressive adverse effects.

Safety and efficacy of lirentelimab in patients with refractory indolent systemic mastocytosis: a first-in-human clinical trial

BACKGROUND

Indolent systemic mastocytosis (ISM) is characterized by excessive mast cell (MC) accumulation and MC-driven signs and symptoms. Currently used therapies are not approved and have limited efficacy. Lirentelimab (AK002) is a monoclonal antibody against sialic acid-binding immunoglobulin-like lectin (Siglec)-8 that inhibits MC activation.

OBJECTIVES

To determine the safety, tolerability and efficacy of lirentelimab in reducing the symptoms of ISM.

METHODS

At a specialty centre for mastocytosis in Germany, we conducted a phase I first-in-human single-ascending and multidose clinical trial of lirentelimab in patients with ISM. Eligible adults had World Health Organization-confirmed ISM and an unsatisfactory response to available treatment. In part A, patients received a single dose of lirentelimab 0.0003, 0.001, 0.003, 0.01 or 0.03 mg kg-1; in part B, patients received one lirentelimab dose of 0.3 mg kg-1 or 1.0 mg kg-1; and in part C, patients received either 1.0 mg kg-1 lirentelimab every 4 weeks for 6 months or ascending doses of lirentelimab (one dose of 1 mg kg-1 followed by five doses of 3-10 mg kg-1 every 4 weeks). The primary endpoint was safety/tolerability. Secondary endpoints included changes from baseline in Mastocytosis Symptom Questionnaire (MSQ), Mastocytosis Activity Score (MAS) and Mastocytosis Quality of Life Questionnaire (MC-QoL) scores at 2 weeks after the final dose.

RESULTS

In 25 patients with ISM (13 in parts A + B and 12 in part C; median age 51 years, 76% female, median 4.6 years from diagnosis), the most common treatment-related adverse events (AEs) were feeling hot (76%) and experiencing a headache (48%). No serious AEs occurred. Median MSQ and MAS symptom severity scores in part C improved (vs. baseline) across all symptoms [MSQ: skin (38-56%), gastrointestinal (49-60%), neurological (47-59%), musculoskeletal (26-27%); MAS: skin (53-59%), gastrointestinal (72-85%), neurological (20-57%), musculoskeletal (25%)]. Median MC-QoL scores improved across all domains: symptoms (39%), social life/functioning (42%), emotions (57%) and skin (44%).

CONCLUSIONS

Lirentelimab was generally well tolerated and improved symptoms and quality of life in patients with ISM. The therapeutic potential of lirentelimab should be considered for ISM.

Siglecs as potential targets of therapy in human mast cell- and/or eosinophil-associated diseases

Siglecs (sialic acid-binding immunoglobulin-like lectins) are a family of vertebrate glycan-binding cell-surface proteins. The majority mediate cellular inhibitory activity once engaged by specific ligands or ligand-mimicking molecules. As a result, Siglec engagement is now of interest as a strategy to therapeutically dampen unwanted cellular responses. When considering allergic inflammation, human eosinophils and mast cells express overlapping but distinct patterns of Siglecs. For example, Siglec-6 is selectively and prominently expressed on mast cells while Siglec-8 is highly specific for both eosinophils and mast cells. This review will focus on a subset of Siglecs and their various endogenous or synthetic sialoside ligands that regulate eosinophil and mast cell function and survival. It will also summarize how certain Siglecs have become the focus of novel therapies for allergic and other eosinophil- and mast cell-related diseases.

Vernal Keratoconjunctivitis: A Systematic Review

Vernal keratoconjunctivitis (VKC) is a chronic, bilateral corneal and conjunctival problem which typically presents in young individuals. VKC is characterized by itching, photophobia, white mucous discharge, lacrimation, foreign body sensation, and pain due to corneal involvement of shield ulcers. Vernal keratoconjunctivitis is categorized within ocular diseases. The diagnosis is clinical, as no sure biomarkers pathognomonic of the disease have yet been identified. The VKC therapy relies on different types of drugs, from antihistamines and topical steroids to cyclosporine or tacrolimus eye drops. In extremely rare cases, there is also the need for surgical treatment for the debridement of ulcers, as well as for advanced glaucoma and cataracts, caused by excessive prolonged use of steroid eye drops. We performed a systematic review of the literature, according to PRISMA guideline recommendations. We searched the PubMed database from January 2016 to June 2023. Search terms were Vernal, Vernal keratoconjunctivitis, and VKC. We initially identified 211 articles. After the screening process, 168 studies were eligible according to our criteria and were included in the review. In this study, we performed a systematic literature review to provide a comprehensive overview of currently available diagnostic methods, management of VKC, and its treatments.

Jak out of the box: Targeting Bruton's tyrosine kinase, sialic acid-binding immunoglobulin-like lectin-8, and Janus kinase 1 in food allergy

There has been rapid growth in the field of immunoglobulin E-mediated food allergy therapeutics, with 1 US Food and Drug Administration-approved therapy in 2020 and several others in various stages of investigation. Oral immunotherapy is the approach with the longest track record of study and provides desensitization for most individuals undertaking the therapy. However, the therapy must be maintained for continued clinical protection, and adverse effects of the therapy are frequent. There is a need to improve allergen immunotherapy safety and durability and to provide a treatment that can target multiple food allergies. In this review, we discuss novel adjunct therapies that may improve safety, such as omalizumab, Bruton's tyrosine kinase inhibitors, and agonists of sialic acid-binding immunoglobulin-like lectin-8, which suppress hypersensitivity responses. We also discuss approaches that may improve magnitude or durability of the treatment response, such as dupilumab and Janus kinase 1 inhibitors.

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.

GlycoCAP: A Cell-Free, Bacterial Glycosylation Platform for Building Clickable Azido-Sialoglycoproteins

Glycan-binding receptors known as lectins represent a class of potential therapeutic targets. Yet, the therapeutic potential of targeting lectins remains largely untapped due in part to limitations in tools for building glycan-based drugs. One group of desirable structures is proteins with noncanonical glycans. Cell-free protein synthesis systems have matured as a promising approach for making glycoproteins that may overcome current limitations and enable new glycoprotein medicines. Yet, this approach has not been applied to the construction of proteins with noncanonical glycans. To address this limitation, we develop a cell-free glycoprotein synthesis platform for building noncanonical glycans and, specifically, clickable azido-sialoglycoproteins (called GlycoCAP). The GlycoCAP platform uses an Escherichia coli-based cell-free protein synthesis system for the site-specific installation of noncanonical glycans onto proteins with a high degree of homogeneity and efficiency. As a model, we construct four noncanonical glycans onto a dust mite allergen (Der p 2): α2,3 C5-azido-sialyllactose, α2,3 C9-azido-sialyllactose, α2,6 C5-azido-sialyllactose, and α2,6 C9-azido-sialyllactose. Through a series of optimizations, we achieve more than 60% sialylation efficiency with a noncanonical azido-sialic acid. We then show that the azide click handle can be conjugated with a model fluorophore using both strain-promoted and copper-catalyzed click chemistry. We anticipate that GlycoCAP will facilitate the development and discovery of glycan-based drugs by granting access to a wider variety of possible noncanonical glycan structures and also provide an approach for functionalizing glycoproteins by click chemistry conjugation.

Siglecs in allergy and asthma

The term "allergic diseases" encompasses several common, IgE-mediated conditions that range from being annoying to those that are life-threatening. Available treatments include active avoidance of the instigating allergen and the use of a variety of oral, inhaled, intranasal, intraocular and injected agents. While most individuals with allergies do well with existing therapies, there are still unmet therapeutic needs. Siglecs (sialic acid-binding, immunoglobulin-like lectins) are a family of single-pass transmembrane I-type lectins found on various subsets of cells, especially those of the immune system. All Siglecs have extracellular domains recognizing sialoside ligands, and most contain cytoplasmic domains with inhibitory signaling activity. This review focuses on Siglecs that likely play a role in regulating allergic and asthmatic responses, and how specific Siglecs, expressed on cells such as eosinophils and mast cells, are being targeted for therapeutic benefit.

Subsets of Eosinophils in Asthma, a Challenge for Precise Treatment

The existence of eosinophils was documented histopathologically in the first half of the 19th century. However, the term “eosinophils” was first used by Paul Ehrlich in 1878. Since their discovery and description, their existence has been associated with asthma, allergies, and antihelminthic immunity. Eosinophils may also be responsible for various possible tissue pathologies in many eosinophil-associated diseases. Since the beginning of the 21st century, the understanding of the nature of this cell population has undergone a fundamental reassessment, and in 2010, J. J. Lee proposed the concept of “LIAR” (Local Immunity And/or Remodeling/Repair), underlining the extensive immunoregulatory functions of eosinophils in the context of health and disease. It soon became apparent that mature eosinophils (in line with previous morphological studies) are not structurally, functionally, or immunologically homogeneous cell populations. On the contrary, these cells form subtypes characterized by their further development, immunophenotype, sensitivity to growth factors, localization, role and fate in tissues, and contribution to the pathogenesis of various diseases, including asthma. The eosinophil subsets were recently characterized as resident (rEos) and inflammatory (iEos) eosinophils. During the last 20 years, the biological therapy of eosinophil diseases, including asthma, has been significantly revolutionized. Treatment management has been improved through the enhancement of treatment effectiveness and a decrease in the adverse events associated with the formerly ultimately used systemic corticosteroids. However, as we observed from real-life data, the global treatment efficacy is still far from optimal. A fundamental condition, “sine qua non”, for correct treatment management is a thorough evaluation of the inflammatory phenotype of the disease. We believe that a better understanding of eosinophils would lead to more precise diagnostics and classification of asthma subtypes, which could further improve treatment outcomes. The currently validated asthma biomarkers (eosinophil count, production of NO in exhaled breath, and IgE synthesis) are insufficient to unveil super-responders among all severe asthma patients and thus give only a blurred picture of the adepts for treatment. We propose an emerging approach consisting of a more precise characterization of pathogenic eosinophils in terms of the definition of their functional status or subset affiliation by flow cytometry. We believe that the effort to find new eosinophil-associated biomarkers and their rational use in treatment algorithms may ameliorate the response rate to biological therapy in patients with severe asthma.

Discovery of an agonistic Siglec-6 antibody that inhibits and reduces human mast cells

Mast cells (MC) are key drivers of allergic and inflammatory diseases. Sialic acid-binding immunoglobulin-like lectin (Siglec)-6 is an immunoregulatory receptor found on MCs. While it is recognized that engaging Siglecs with antibodies mediates inhibition across immune cells, the mechanisms that govern this agonism are not understood. Here we generated Siglec-6 mAb clones (AK01 to AK18) to better understand Siglec-6-mediated agonism. Siglec-6 mAbs displayed epitope-dependent receptor internalization and inhibitory activity. We identified a Siglec-6 mAb (AK04) that required Fc-mediated interaction for receptor internalization and induced inhibition and antibody-dependent cellular phagocytosis against MCs. AK04-mediated MC inhibition required Siglec-6 immunoreceptor tyrosine-based inhibitory motif (ITIM) and ITIM-like domains and was associated with receptor cluster formation containing inhibitory phosphatases. Treatment of humanized mice with AK04 inhibited systemic anaphylaxis with a single dose and reduced MCs with chronic dosing. Our findings suggest Siglec-6 activity is epitope dependent and highlight an agonistic Siglec-6 mAb as a potential therapeutic approach in allergic disease.

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.