Remibrutinib, a novel BTK inhibitor, demonstrates promising efficacy and safety in chronic spontaneous urticaria

Paeoniflorin as a potential agent for urticaria treatment: Suppressing mast cell degranulation through HMGB1/TLR4/NF-κB signaling inhibition

INTRODUCTION

Paeoniflorin (PF) has strong immunomodulatory effects and has been widely used in the treatment of many diseases, but its mechanism of action in urticaria is not clear. The aim of this experiment was to investigate the role and mechanism of paeoniflorin in improving mast cell degranulation in urticaria.

METHODS

The mouse model of urticaria was replicated by ovalbumin+ aluminum hydroxide method, and the mast cell degranulation model was induced by anti-DNP IgE+ Dinitrophenyl- Bovine Serum Albumin (DNP-BSA), and the mice and cells were intervened by different doses of PF. The histopathological changes of the dorsal skin were observed using hematoxylin-eosin (HE) staining, the infiltration of mast cells was observed by Toluidine blue staining, the expression of mast cell tryptase (MCT) was examined by Immunohistochemical staining, the cell viability was detected by CCK8 assay, and Rhod-2/AM flow cytometry assay to determine calcium ion content, enzyme-linked immunosorbent assay (ELISA) detected mast cell degranulation-associated factors, and Western blot analyzed HMGB1/TLR4/NF-κB signaling factors.

RESULTS

PF reduced the number of scratches in mice, ameliorated histopathological damage in dorsal skin, decreased mast cell degranulation rate, reduced the levels of Ca2 +, MCT, β-HEX, HIS, MCP-1, TNF-α, and IL-13, and inhibited the expression of HMGB1, TLR4, MyD88, NF-κB p65 (Nucleus), and p-IκBα. Moreover, Rec-HMGB1 reversed the effect of PF.

CONCLUSION

PF mitigates urticarial mast cell degranulation through the inhibition of the HMGB1/TLR4/NF-κB signaling pathway, suggesting its potential as a therapeutic agent for the treatment of urticaria.

Bruton's tyrosine kinase - A new target for immune mediated inflammatory diseases?

Bruton's tyrosine kinase (BTK) is a cytoplasmic protein that plays a key role in signalling pathways downstream of diverse surface receptors in B-cells and myeloid cells. These include the B-cell receptor itself, Fc receptors including FcεRI, toll-like receptors and chemokine receptors. Congenital deficiency of BTK causes X-linked agammaglobulinaemia because of B-cell developmental block, and BTK inhibitors (BTKi) are approved for the treatment of certain B-cell malignancies. They have also been studied in a variety of autoimmune and inflammatory diseases. In rheumatic conditions, results have been disappointing in rheumatoid arthritis (RA) and systemic lupus erythematosus but with some evidence for efficacy in Sjogren's syndrome. Data are more positive in multiple sclerosis, as well as in the cutaneous disease chronic spontaneous urticaria and possibly pemphigus vulgaris. BTKi may also find a role in severe allergic disease such as food allergy. First generation BTKi had a safety profile that included cardiotoxicity, hypertension, haemorrhage and rash. Second generation inhibitors have a more acceptable safety profile although dose-limiting toxicity is still observed in some conditions, including RA. Pharmacokinetic factors aside, the variable efficacy in different diseases is not fully explained but is likely to reflect disease dependence on different pathways in B-cells and myeloid cells and their relative sensitivity to BTKi.

Type 2 Inflammation and Its Role in Dermatologic Diseases

Atopic dermatitis, prurigo nodularis, and chronic spontaneous urticaria are immune-mediated, inflammatory skin conditions characterized by intense itch and disease-specific skin lesions. Despite their different clinical presentations, the three diseases are unified by an aberrant type 2 immune response involving type 2 cytokines, immune cells, and sensory nerves that may underlie their shared clinical manifestations of inflammation and pruritus. The chronic nature of these conditions is associated with significant impairment in patients' quality of life and psychological disorders, such as anxiety and depression. This article reviews type 2 inflammation and its role in atopic dermatitis, prurigo nodularis, and chronic spontaneous urticaria, focusing on the pathophysiologic drivers of type 2 inflammation in each dermatologic condition. Understanding the shared immune mechanisms that underlie these seemingly distinct skin diseases and other concomitant inflammatory conditions is critical for applying therapeutic interventions targeting the type 2 immune pathway.

Next generation Bruton's tyrosine kinase inhibitors - characterization of in vitro potency and selectivity

Bruton's tyrosine kinase (BTK) mediates B cell receptor and Fc receptor signaling and is a key regulator of autoimmunity and allergy. A series of novel BTK inhibitors (BTKi) are currently in development for non-oncologic indications with covalent-irreversible (remibrutinib, evobrutinib, tolebrutinib, orelabrutinib), covalent-reversible (rilzabrutinib), and non-covalent reversible (fenebrutinib) binding modes. This study characterizes their in vitro potency and selectivity profiles under the same conditions to minimize assay differences across the different binding modes. Covalent BTKi showed human in vitro blood BTK binding in a time- and concentration-dependent manner with remibrutinib being the most potent and fastest in onset of action. Cellular BTK pathway inhibition was determined in human blood B cells and basophils, and for covalent BTKi correlated well with BTK binding. In contrast to the covalent-irreversible remibrutinib, the non-covalent reversible fenebrutinib showed rapid loss of cellular BTK inhibition after washout. Kinase selectivity was assessed in a binding screen across the human kinome, followed by quantification of binding affinities for a selection of kinases. BTKi ranked in their selectivity as follows (most selective to least): remibrutinib, fenebrutinib, evobrutinib, orelabrutinib, rilzabrutinib and tolebrutinib. These data suggest that next generation BTKi show important differences in their in vitro target binding and selectivity when compared under the same conditions.

Randomization-Based Inference for MCP-Mod

Dose selection is critical in pharmaceutical drug development, as it directly impacts therapeutic efficacy and patient's safety of a drug. The Generalized Multiple Comparison Procedures and Modeling approach is commonly used in Phase II trials for testing and estimation of dose-response relationships. However, its effectiveness in small sample sizes, particularly with binary endpoints, is hindered by issues like complete separation in logistic regression, leading to non existence of estimates. Motivated by an actual clinical trial using the MCP-Mod approach, this paper introduces penalized maximum likelihood estimation (MLE) and randomization-based inference techniques to address these challenges. Randomization-based inference allows for exact finite sample inference, while population-based inference for MCP-Mod typically relies on asymptotic approximations. Simulation studies demonstrate that randomization-based tests can enhance statistical power in small to medium-sized samples while maintaining control over type-I error rates, even in the presence of time trends. Our results show that residual-based randomization tests using penalized MLEs not only improve computational efficiency but also outperform standard randomization-based methods, making them an adequate choice for dose-finding analyses within the MCP-Mod framework. Additionally, we apply these methods to pharmacometric settings, demonstrating their effectiveness in such scenarios. The results in this paper underscore the potential of randomization-based inference for the analysis of dose-finding trials, particularly in small sample contexts.

The emerging role of Bruton's tyrosine kinase inhibition in urticaria management

INTRODUCTION

Bruton's tyrosine kinase (BTK) is a cytoplasmic signaling protein expressed across a variety of immune cells, terminally differentiated plasma cells, and natural killer cells. Due to the signal potential and targetable nature of BTK, the use of BTK inhibitors (BTKis) has been proposed for the management of several diseases. Currently, the use of BTKis is under investigations for several dermatological conditions such as pemphigus, systemic lupus erythematosus, hidradenitis suppurativa, atopic dermatitis, and chronic spontaneous urticaria (CSU).

AREAS COVERED

The aim of this review is to delve into the use of BTKis in the management of CSU, in order to explore the potential of therapeutic inhibition of BTK in patients with CSU. A thorough analysis of the existing medical literature was conducted across the PubMed, Ovid, Scopus, Embase, and Cochrane Library databases up to 17 August 2024.

EXPERT OPINION

BTK use may represent a breakthrough in the management of CSU. Indeed, their use is characterized by oral administration and a favorable mechanism of action that acts on a significant pathogenic pathway rather than a single molecule. However, long-term studies are needed to further investigate safety data, although data from registered trials appear to be reassuring.

Sleep Disturbance and Chronic Urticaria: A Narrative Review of Its Relationship, Treatment and Evolving Literature

Background and Aims

Chronic Spontaneous Urticaria is characterized by the sudden onset of itchy wheals and angioedema and is primarily driven by mast cells. It can have a significant impact on the Quality of Life (QoL) of an individual. While the role of mast cells in urticaria is extensively described, the link between sleep disorders and inflammatory skin conditions such as urticaria is still being explored. The review aims to provide an overview of the current knowledge about chronic urticaria, elaborating on the impact of poor sleep quality on QoL of patients with urticaria, with a focus on their emotional well-being.

Methods

The review explores potential mechanisms linking chronic urticaria and sleep disturbances, such as persistent itching and discomfort, the release of inflammatory mediators, systemic inflammation, psychological factors, and effects of medication.

Results

The review finds that sleep disturbances have a significant impact on chronic urticaria. It identifies several potential mechanisms linking the two conditions, including persistent symptoms, inflammatory processes, psychological factors, and medication effects. Treatment approaches include a combination of pharmacological and nonpharmacological interventions.

Conclusion

The article emphasizes the significance of recognizing the impact of sleep disturbances on chronic urticaria. It lays the groundwork for future research to expand our understanding of this association, ultimately leading to improved management strategies and improved QoL for affected individuals.

Biological and target synthetic treatments for chronic spontaneous urticaria: A systematic review and network meta-analysis

BACKGROUND

Most biological and synthetic target-specific drugs for antihistamine-refractory chronic spontaneous urticaria (CSU) have not been compared head-to-head. This systematic review and network meta-analysis evaluated their relative efficacy and safety.

METHODS

Searches were conducted on PubMed, Embase, Web of Science and Cochrane library databases to March 25, 2024 for randomized trials. A random-effects model was used to calculate the network estimates reported as mean differences (MD) and odds ratios (OR) with corresponding 95% CIs. Main outcomes included the weekly urticaria activity score (UAS7), adverse events (AEs) and serious adverse events (SAEs).

RESULTS

23 randomized clinical trials with 6933 participants that compared 26 different interventions or dosages and placebos were included. Omalizumab 300 mg [MD -10.07, 95% CI (-11.35; -8.82)] continues to demonstrate superior efficacy compared with placebo. Remibrutinib, at doses of 35 mg once daily [MD -7.80, 95% CI (-12.76; -2.51)], 25 mg twice daily [MD -7.69, 95% CI (-9.85; -5.76)], and 10 mg twice daily [MD -7.61, 95% CI (-12.59; -2.47)], had the best overall performance for efficacy and safety. Dupilumab, fenebrutinib, and rilzabrutinib also showed greater efficacy than placebo. The results were similar for the proportion of patients who achieved UAS7 ≤ 6 or UAS7 = 0. No significant differences were found among all treatment comparisons for AEs and SAEs.

CONCLUSION

The findings of this study indicate that the biological agent omalizumab 300 mg and the oral small molecule remibrutinib at doses of 35 mg, 25 mg, or 10 mg are recommended for patients with antihistamine-refractory CSU.

TRIAL REGISTRATION

PROSPERO: CRD42024516289.

Rilzabrutinib in Antihistamine-Refractory Chronic Spontaneous Urticaria: The RILECSU Phase 2 Randomized Clinical Trial

Importance

Chronic spontaneous urticaria (CSU) is a skin disease driven mainly by the activation of cutaneous mast cells through various mechanisms. Bruton tyrosine kinase (BTK), expressed in B cells and mast cells, plays a critical role in multiple immune-mediated disease processes.

Objective

To determine the efficacy and risk profile of rilzabrutinib (SAR444671), an oral, reversible, covalent, next-generation BTK inhibitor, in treating patients with CSU.

Design, Setting, and Participants

The Rilzabrutinib Efficacy and Safety in CSU (RILECSU) randomized clinical trial was a 52-week phase 2 study comprising a 12-week, double-blind, placebo-controlled, dose-ranging period, followed by a 40-week open-label extension. The trial was conducted from November 24, 2021, through April 23, 2024. Fifty-one centers enrolled and randomized participants across 12 countries in Asia, Europe, North America, and South America. The trial participants included adults aged 18 to 80 years with moderate to severe CSU (weekly Urticaria Activity Score [UAS7] of 16 or more; weekly Itch Severity Score [ISS7] of 8 or more) not adequately controlled with H1-antihistamine treatment.

Interventions

Patients were randomized 1:1:1:1 to rilzabrutinib, 400 mg, once every evening (400 mg/d), twice per day (800 mg/d), 3 times per day (1200 mg/d), or matching placebo.

Main Outcomes

The primary end point was change from baseline at week 12 in ISS7 (for US and US reference countries) or UAS7 (for non-US reference countries).

Results

A total of 160 omalizumab-naive and omalizumab-incomplete responders were randomized (mean [SD] age, 44.1 [13.4] years; 112 [70.0%] female). The primary analysis population included only the 143 omalizumab-naive patients. Significant reductions at week 12 were observed with rilzabrutinib, 1200 mg/d, vs placebo from baseline in ISS7 (least squares [LS] mean, -9.21 vs -5.77; difference, -3.44 [95% CI, -6.25 to -0.62]; P = .02) and UAS7 (LS mean, -16.89 vs -10.14; difference, -6.75 [95% CI, -12.23 to -1.26]; P = .02). In addition, improvements in weekly Hives Severity Score (HSS7) and weekly Angioedema Activity Score (AAS7) were observed. Improvements in ISS7, UAS7, HSS7, and AAS7 were observed as early as week 1. CSU-related biomarkers, including soluble Mas-related G protein-coupled receptor X2, immunoglobulin (Ig)-G antithyroid peroxidase, IgG anti-Fc-ε receptor 1, and interleukin-31, were reduced compared to placebo at week 12. Rilzabrutinib demonstrated a favorable risk-benefit profile; adverse events occurring at a higher frequency with rilzabrutinib vs placebo included diarrhea, nausea, and headache.

Conclusions and Relevance

The results of the RILECSU randomized clinical trial demonstrated efficacy and rapid onset of action of rilzabrutinib, 1200 mg/d, over 12 weeks, in addition to an acceptable adverse event profile. Together, these data support the use of rilzabrutinib in treating patients with moderate to severe CSU refractory to H1-antihistamines. Further research is needed to determine long-term efficacy and potential harms.

Trial Registration

ClinicalTrials.gov Identifier: NCT05107115.

Endotypes of chronic spontaneous urticaria and angioedema

The current understanding of chronic spontaneous urticaria (CSU) suggests that a complex network of inflammatory pathways is involved in its pathogenesis. Recent development highlighted autoimmunity as one of the key pathogenic mechanisms of CSU. Two endotypes, type I autoallergic (associated with IgE antibodies against autoantigens) and type IIb autoimmune (mediated by IgG autoantibodies against IgE or its high-affinity receptor [FcεRI]), have been characterized. A subpopulation of the patients has an overlap of the 2 endotypes. About 10% of patients with CSU present with only angioedema. Patients with isolated mast cell-mediated angioedema have distinct clinical and demographic features and should be distinguished from bradykinin-mediated angioedema. Multiple potential biomarkers such as total IgE level and IgG anti-thyroid peroxidase have been identified and, together with the corresponding endotypes, have been linked to disease severity, duration, and response to treatments. Currently, the use of these biomarkers is limited in clinical settings given the few options of therapy. However, with the advent of novel treatments, endotyping CSU might help with tailoring treatment approaches.

Update on mast cell biology

Mast cells (MCs) are heterogeneous tissue-resident effector cells that are thought to play central roles in allergic inflammatory disease, yet the degree of heterogeneity and nature of these roles has remained elusive. In recent years, advances in tissue culture systems, preclinical mouse models, and the continued spread of single-cell RNA sequencing have greatly advanced our understanding of MC phenotypes in health and disease. These approaches have identified novel interactions of MC subsets with immune cells, neurons, and tissue structural cells, changing our understanding of how MCs both drive and help resolve tissue inflammation, reshape tissue microenvironments, and influence host behavior. This review addresses key studies from 2022 to 2024 that have advanced our understanding of MC biology in mice and humans.

Disease-modifying strategies: Targeting protein kinases in multiple sclerosis and other autoimmune disorders

A wide variety of immunomodulatory therapies are already available for the treatment of multiple sclerosis (MS). Through fundamental insights from basic research with a gain of knowledge in the pathological processes underlying MS, the exploration of additional medical compounds within clinical trials has been ignited. Emerging novel medications with innovative mechanisms of action are being introduced. Those mechanisms of action include a broad therapeutic spectrum of substances targeting various protein kinases, some of which could also be used for the treatment of other autoimmune-mediated diseases. The advancement of new compounds could therefore enable a more personalized approach in treating MS, taking into consideration patients' co-existing autoimmune-mediated diseases. In this review, we discuss potential compounds targeting protein kinases, currently under investigation in clinical trials for various autoimmune diseases that could become viable treatment options for MS and comorbid autoimmune conditions in the future.

Pharmacology and safety of TAS5315, a Bruton tyrosine kinase inhibitor, in healthy volunteers: First-in-human, randomized, ascending-dose studies

AIM

TAS5315 is a Bruton tyrosine kinase (Btk) inhibitor in development for autoimmune and allergic diseases, including rheumatoid arthritis (RA) and chronic spontaneous urticaria (CSU). Two clinical studies evaluated the pharmacology and safety of single and multiple oral doses of TAS5315.

METHODS

Two phase 1 studies (single ascending-dose [SAD] and multiple ascending-dose [MAD]) assessed the pharmacokinetics (including effect of food), pharmacodynamics (Btk occupancy, inhibition of basophil activation) and safety of TAS5315 (up to 8 mg/day) in healthy males.

RESULTS

TAS5315 showed linear pharmacokinetics over a 0.01-8 mg dose range; maximum plasma concentration and area under the plasma concentration-time curve were reduced by ~40% by food. TAS5315 had dose dependent effects on Btk and basophil activation. In the SAD study, doses ≥2 mg resulted in mean Btk occupancy of almost 100% at 2 and 6 h, and >80% at 24 h, post-administration. TAS5315 1-8 mg/day inhibited basophil activation (mean change from baseline -55% to -89%). TAS5315 was generally tolerable. Although it dose-dependently reduced platelet aggregation (over 2-8 mg in both studies) and prolonged bleeding time (1-8 mg in the MAD study), no relationship between these effects and clinical symptoms was observed. All adverse drug reactions were mild and resolved without treatment; no noteworthy safety concerns were observed in either study.

CONCLUSION

These data indicate TAS5315 has potential as a novel therapeutic for immunological diseases associated with aberrant Btk signalling, including RA and CSU. Further evaluation of TAS5315 is warranted.

Remibrutinib in Chronic Spontaneous Urticaria

BACKGROUND

Chronic spontaneous urticaria is an idiopathic syndrome defined by recurring itch, hives, or angioedema (or a combination of these symptoms) for more than 6 weeks. Remibrutinib, an oral, highly selective Bruton's tyrosine kinase inhibitor, showed efficacy and favorable safety in phase 2b trials. Data from phase 3 trials are needed.

METHODS

In the identical, multicenter, double-blind, randomized, placebo-controlled REMIX-1 and REMIX-2 trials, we evaluated the efficacy and safety of remibrutinib in patients with symptomatic chronic spontaneous urticaria after treatment with second-generation H1-antihistamines. Patients were randomly assigned in a 2:1 ratio to receive oral remibrutinib at a dose of 25 mg twice daily or placebo. The primary end point was the change from baseline to week 12 in the urticaria activity score during a 7-day period (UAS7), which comprises severity scores for itch and hives during 1 week (scores range from 0 to 42, with higher scores indicating greater severity). Key secondary end points included adverse events and a UAS7 of 6 or lower at weeks 2 and 12 and a UAS7 of 0 at week 12.

RESULTS

A total of 470 patients in REMIX-1 and 455 in REMIX-2 were randomly assigned to receive either remibrutinib (313 and 300 patients, respectively) or placebo (157 and 155 patients, respectively). The remibrutinib group had a significantly greater decrease in the UAS7 at week 12 than the placebo group (least-squares mean [±SE] change, -20.0±0.7 vs. -13.8±1.0 [P<0.001] in REMIX-1 and -19.4±0.7 vs. -11.7±0.9 [P<0.001] in REMIX-2), which appeared to be sustained through week 24. At week 12, significantly more patients in the remibrutinib group than in the placebo group had a UAS7 of 6 or lower (REMIX-1, 49.8% vs. 24.8% [P<0.001]; REMIX-2, 46.8% vs. 19.6% [P<0.001]) and a UAS7 of 0 (REMIX-1, 31.1% vs. 10.5% [P<0.001]; REMIX-2, 27.9% vs. 6.5% [P<0.001]). The percentages of patients with any adverse event and with serious adverse events were similar in the remibrutinib group and the placebo group, although a higher percentage of patients in the remibrutinib group than in the placebo group had petechiae (3.8% vs. 0.3% in the combined groups).

CONCLUSIONS

Treatment with oral remibrutinib resulted in a significant improvement in a composite measure of itching and hives at week 12. (Funded by Novartis Pharmaceuticals; REMIX-1 and REMIX-2 ClinicalTrials.gov numbers, NCT05030311 and NCT05032157, respectively.).

Mast Cells at the Crossroads of Hypersensitivity Reactions and Neurogenic Inflammation

Although mast cells have long been known, they are not yet fully understood. They are traditionally recognized for their role in allergic reactions through the IgE/FcεRI axis, but different groups of surface receptors have since been characterized, which appear to be involved in the manifestation of peculiar clinical features. In particular, MRGPRX2 has emerged as a crucial receptor involved in degranulating human skin mast cells. Because of mast cells' close proximity to peripheral nerve endings, it may play a key role in neuroimmune interactions. This paper provides an overview of mast cell contributions to hypersensitivity and so-called "pseudoallergic" reactions, as well as an update on neuroinflammatory implications in the main models of airway and skin allergic diseases. In particular, the main cellular characteristics and the most relevant surface receptors involved in MC pathophysiology have been reappraised in light of recent advancements in MC research. Molecular and clinical aspects related to MC degranulation induced by IgE or MRGPRX2 have been analyzed and compared, along with their possible repercussions and limitations on future therapeutic perspectives.

Sequelae of B-Cell Depleting Therapy: An Immunologist's Perspective

B-cell depleting therapy (BCDT) has revolutionised the treatment of B-cell malignancies and autoimmune diseases by targeting specific B-cell surface antigens, receptors, ligands, and signalling pathways. This narrative review explores the mechanisms, applications, and complications of BCDT, focusing on the therapeutic advancements since the introduction of rituximab in 1997. Various monoclonal antibodies and kinase inhibitors are examined for their roles in depleting B cells through antibody-dependent and independent mechanisms. The off-target effects, such as hypogammaglobulinemia, infections, and cytokine release syndrome, are discussed, emphasising the need for immunologists to identify and help manage these complications. The increasing prevalence of BCDT has necessitated the involvement of clinical immunologists in addressing treatment-associated immunological abnormalities, including persistent hypogammaglobulinemia and neutropenia. We highlight the importance of considering underlying inborn errors of immunity (IEI) in patients presenting with these complications. Furthermore, we discuss the impact of BCDT on other immune cell populations and the challenges in predicting and managing long-term immunological sequelae. The potential for novel BCDT agents targeting the BAFF/APRIL-TACI/BCMA axis and B-cell receptor signalling pathways to treat autoimmune disorders is also explored, underscoring the rapidly evolving landscape of B-cell targeted therapies.

Urticaria

Urticaria (hives) is a common disorder that may be associated with angioedema (swelling that occurs beneath the skin). It is generally classified as acute or chronic, and chronic urticaria is further classified as spontaneous or inducible Second-generation, non-sedating histamine type 1 (H1)-receptor antihistamines represent the mainstay of therapy for both acute and chronic urticaria. Second-line treatment for uncontrolled chronic urticaria includes omalizumab (a monoclonal anti-immunoglobulin E [IgE] antibody). In this article, we review the causes, diagnosis and management of urticaria (with or without angioedema).

Exploring mechanisms of skin aging: insights for clinical treatment

The skin is the largest organ in the human body and is made up of various cells and structures. Over time, the skin will age, which is not only influenced by internal factors, but also by external environmental factors, especially ultraviolet radiation. Aging causes immune system weakening in the elderly, which makes them more susceptible to dermatosis, such as type 2 inflammatory mediated pruritus. The immune response in this condition is marked by senescent cells consistently releasing low amounts of pro-inflammatory cytokines through a senescence-associated secretory phenotype (SASP). This continuous inflammation may accelerate immune system aging and establish a connection between immune aging and type 2 inflammatory skin diseases. In addition, two chronic pigmentation disorders, vitiligo and chloasma, are also associated with skin aging. Aged cells escape the immune system and accumulate in tissues, forming a microenvironment that promotes cancer. At the same time, "photoaging" caused by excessive exposure to ultraviolet radiation is also an important cause of skin cancer. This manuscript describes the possible links between skin aging and type 2 inflammation, chronic pigmentation disorders, and skin cancer and suggests some treatment options.

Therapies for Chronic Spontaneous Urticaria: Present and Future Developments

Chronic spontaneous urticaria (CSU) is a complex dermatological condition characterized by recurrent wheals and/or angioedema lasting for more than six weeks, significantly impairing patients' quality of life. According to European guidelines, the first step in treatment involves second-generation H1-antihistamines (sgAHs), which block peripheral H1 receptors to alleviate symptoms. In cases with inadequate responses, the dose of antihistamines can be increased by up to fourfold. If symptoms persist despite this adjustment, the next step involves the use of omalizumab, a monoclonal anti-IgE antibody, which has shown efficacy in the majority of cases. However, a subset of patients remains refractory, necessitating alternative treatments such as immunosuppressive agents like cyclosporine or azathioprine. To address these unmet needs, several new therapeutic targets are being explored. Among them, significant attention is being given to drugs that block Bruton's tyrosine kinase (BTK), such as remibrutinib, which reduces mast cell activation. Therapies like dupilumab, which target the interleukin-4 (IL-4) and IL-13 pathways, are also under investigation. Additionally, molecules targeting the Mas-related G protein-coupled receptor X2 (MRGPRX2), and those inhibiting the tyrosine kinase receptor Kit, such as barzolvolimab, show promise in clinical studies. These emerging treatments offer new options for patients with difficult-to-treat CSU and have the potential to modify the natural course of the disease by targeting key immune pathways, helping to achieve longer-term remission. Further research is essential to better elucidate the pathophysiology of CSU and optimize treatment protocols to achieve long-term benefits in managing this condition. Altogether, the future of CSU treatments that target pathogenetic mechanisms seems promising.

Chronic Spontaneous Urticaria: A Review

Importance

Chronic spontaneous urticaria affects approximately 1% of the general population worldwide, including approximately 3 million people in the US, impairs patients' quality of life, and is associated with multiple comorbidities.

Observations

Chronic spontaneous urticaria affects patients of any age but is most common in females aged 30 to 50 years. Diagnosis is based on clinical presentation, ie, spontaneously recurring wheals, angioedema, or both. Chronic spontaneous urticaria persists for more than 1 year in most patients (1 or repeated episodes) and may present with comorbidities including chronic inducible urticaria (>10%), autoimmune thyroiditis (approximately 20%), metabolic syndrome (6%-20%), and anxiety (10%-31%) and depression (7%-29%). Known autoimmune endotypes (subtypes of urticaria defined by distinct pathogenesis) of chronic spontaneous urticaria are mediated by mast cell-activating IgE and/or IgG autoantibodies (>50%). Approximately 40% of patients with chronic spontaneous urticaria have a Dermatology Life Quality Index of more than 10, corresponding to a very large or extremely large negative effect on quality of life. Second-generation H1 antihistamines are first-line treatment; partial or complete response, defined as a reduction in urticaria symptoms of greater than 50%, is observed in approximately 40% of patients. The 2022 international urticaria guideline recommends the monoclonal anti-IgE antibody omalizumab as second-line treatment for antihistamine-refractory chronic spontaneous urticaria. However, at least 30% of patients have an insufficient response to omalizumab, especially those with IgG-mediated autoimmune urticaria. Cyclosporine, used off-label, can improve symptoms in approximately 54% to 73% of patients, especially those with autoimmune chronic spontaneous urticaria and nonresponse to omalizumab, but has adverse effects such as kidney dysfunction and hypertension.

Conclusions and Relevance

Chronic spontaneous urticaria is an inflammatory skin disease associated with medical and psychiatric comorbidities and impaired quality of life. Second-generation H1 antihistamines are first-line treatment, omalizumab is second-line treatment, and cyclosporine is third-line treatment for chronic spontaneous urticaria.

Quality of life measurement in urticaria: Position statement of the European Academy of Dermatology and Venereology Task Forces on Quality of Life and Patient-Oriented Outcomes and Urticaria and Angioedema

The European Academy of Dermatology and Venereology (EADV) Task Forces on quality of life (QoL) and patient-oriented outcomes and on urticaria and angioedema recommendations for the assessment of Health-related (HR) QoL in all patients with urticaria in research and practice are as follows: to use the DLQI for adults and the CDLQI for children as dermatology-specific and the CU-Q2oL as a disease-specific HRQoL instruments in urticaria; to use generic instruments to provide comparison of data on urticaria with non-dermatologic diseases, or to compare with healthy volunteers or the general population; to select validated HRQoL instruments with appropriate age limits; to present exact numeric data for HRQoL results; correct title of any HRQoL instrument should be used, along with its correct abbreviation and the reference to its original publication, where possible. The EADV TFs discourage the use of non-validated HRQoL instruments and modified HRQoL instruments that have not undergone standard validation.

Safety, pharmacokinetics, and pharmacodynamics of sofnobrutinib, a novel non-covalent BTK inhibitor, in healthy subjects: First-in-human phase I study

Bruton's tyrosine kinase (BTK) is a potential therapeutic target for allergic and autoimmune diseases. This first-in-human phase I study evaluated safety, pharmacokinetic, and pharmacodynamic profiles of sofnobrutinib (formerly AS-0871), a highly selective, orally available, non-covalent BTK inhibitor, in healthy adult subjects. Single ascending doses (SAD; 5-900 mg) and multiple ascending doses (MAD; 50-300 mg twice daily [b.i.d.] for 14 days [morning dose only on Day 14]) of sofnobrutinib were tested. In the entire study, all adverse events (AEs) were mild or moderate, and no apparent dose-proportional trend in severity or frequency was observed. No serious treatment-emergent AEs, cardiac arrythmias, or bleeding-related AEs were reported. In the SAD part, sofnobrutinib exhibited approximately dose-dependent systemic exposures up to 900 mg with rapid absorption (median time to maximum concentration of 2.50-4.00 h) and gradual decline (mean half-lives of 3.7-9.0 h). In the MAD part, sofnobrutinib showed low accumulation after multiple dosing (mean accumulation ratios of ≤1.54) and reached a steady state on ≤Day 7. Single dosing of sofnobrutinib rapidly and dose-dependently suppressed basophil and B-cell activations in ex vivo whole blood assays. Multiple dosing of sofnobrutinib achieved 50.8%-79.4%, 67.6%-93.6%, and 90.1%-98.0% inhibition of basophil activation during the dosing interval of 50, 150, and 300 mg b.i.d., respectively. Based on pharmacokinetic-pharmacodynamic analysis, half-maximal inhibitory concentration (IC50) of sofnobrutinib for basophil activation was 54.06 and 57.01 ng/mL in the SAD and MAD parts, respectively. Similarly, IC50 for B-cell activation was 187.21 ng/mL. These data support further investigation of sofnobrutinib in allergic and autoimmune diseases.

Chronic Spontaneous Urticaria: Current and Emerging Biologic Agents

Antihistamine refractory chronic spontaneous urticaria (CSU) has a prevalence of up to 50%. Anti-immunoglobulin E (IgE) therapies have revolutionized management of CSU, yet refractory cases persist, suggesting a role for biologic agents that impact alternative routes of mast cell stimulation independent of cross-linking at FcεR1. This review addresses anti-IgE and Th2-targeted therapies in the management of CSU. In addition, we explore novel treatments targeting alternative pathways of mast cell activation including MAS-related G protein-coupled receptor-X2 and sialic acid-binding immunoglobulin-like lectin-6, inhibiting intracellular signaling via Bruton's tyrosine kinase, and disrupting KIT activation by SCF.

Mast cell signaling and its role in urticaria

Chronic urticaria is a mast cell (MC)-driven disease characterized by the development of itching wheals and/or angioedema. In the last decades, outstanding progress has been made in defining the mechanisms involved in MC activation, and novel activating and inhibitory receptors expressed in MC surface were identified and characterized. Besides an IgE-mediated activation through high-affinity IgE receptor cross-linking, other activating receptors, including Mas-related G-protein-coupled receptor-X2, C5a receptor, and protease-activated receptors 1 and 2 are responsible for MC activation. This would partly explain the reason some subgroups of chronic spontaneous urticaria (CSU), the most frequent form of urticaria in the general population, do not respond to IgE target therapies, requiring other therapeutic approaches for improving the management of the disease. In this review, we shed some light on the current knowledge of the immunologic and nonimmunologic mechanisms regulating MC activation in CSU, considering the complex inflammatory scenario underlying CSU pathogenesis, and novel potential MC-targeted therapies, including surface receptors and cytoplasmic signaling proteins.

The future of targeted therapy in chronic spontaneous urticaria

Chronic urticaria can be divided into 2 subsets: chronic spontaneous urticaria (CSU) with skin lesions occurring without a specific trigger and chronic inducible urticaria, which has an identified specific stimulus. The annual prevalence of chronic urticaria is 0.5% to 2.3% globally. The CSU is a self-limited disorder in most cases, with an average duration of 2 to 5 years, but symptoms persist beyond 5 years in up to 30% of patients. The first line of treatment is a daily nonsedating, second-generation H1-antihistamine. The CSU guidelines recommend using oral nonsedating antihistamines up to 4 fold in patients with CSU unresponsive to standard doses as the next step in treatment. A meta-analysis found that the rate of response in patients with CSU who responded to updosing was 63.2%. Therefore, approximately 40% of patients continue to have persistent hives and itching requiring treatment with the biologic omalizumab, based on evidence from randomized controlled trials. Although omalizumab has been shown to markedly relieve symptoms of CSU, omalizumab is not effective in all patients and has not been shown to induce long-term disease remission. Thus, there is an unmet need for more effective treatments that can lead to cure or long-term remission. In this review, we will provide an overview of new treatment targets and biologics that are under investigation for the treatment of CSU.

Anaphylaxis in Practice: A Guide to the 2023 Practice Parameter Update

This review summarizes new research developments and clinical practice recommendations for the diagnosis and management of anaphylaxis presented in the Joint Task Force on Practice Parameters 2023 Anaphylaxis practice parameter Update. It is intended to serve as a high-level summary of the 2023 practice parameter, which makes clinically impactful recommendations based on evidence that has emerged since the 2015 practice parameter. We invite clinicians to explore the full 2023 practice parameter to understand the research methods and underlying evidence that have informed the recommendations summarized here. There are new and evolving diagnostic criteria for anaphylaxis, rules for defining elevated tryptase levels, and recognition of signs and symptoms particular to infants and toddlers. The administration of epinephrine should not be used as a surrogate to diagnose anaphylaxis. Risk factors for anaphylaxis should be assessed on a case-by-case basis. Patient counseling and shared decision-making are essential to support patients' treatment decisions and capacity to manage the risk of anaphylaxis at home and in other community settings. Activation of emergency medical services after home epinephrine administration may not be required in all cases, and patients should be engaged in shared decision-making to determine when home management may be appropriate.

The Effect of Placebo on Pruritus in Patients with Chronic Urticaria: A Systematic Review and Meta-Analysis of Randomized Placebo-Controlled Trials

BACKGROUND

The anti-pruritic effect of placebo in patients with chronic urticaria has gained increasing attention in clinical research. However, the extent of placebo effect and its influencing factors in the treatment of chronic urticaria are not well understood.

OBJECTIVE

The objective of this systematic review and meta-analysis was to investigate the effect of placebo on pruritus in patients with chronic urticaria and to explore relevant influencing factors.

METHODS

PubMed, Embase, Web of Science, Cochrane Library, and PsycINFO were searched from inception to 10 July, 2024. Primary outcome included pruritus scores. The secondary outcomes focused on global symptoms and quality of life. Subgroup analyses and meta-regression analyses were conducted based on drug types, sample size, participants' age, and other variables. The Grading of Recommendations Assessment, Development, and Evaluation (GRADE) system and a trial sequential analysis were employed to establish the reliability of evidence.

RESULTS

A total of 65 eligible publications (including 67 randomized controlled trials) involving 10,704 patients with chronic urticaria were included. The pruritus scores decreased following placebo treatment (moderate evidence). In addition, favorable results were observed in global symptoms (moderate evidence) and quality of life (low evidence) after placebo treatment. Subgroup analyses indicated that the type of active medication in intervention groups was an influencing factor of placebo effect of pruritus. Meta-regression analyses demonstrated that the anti-pruritic effect of placebo was inversely correlated with sample size and positively correlated with participants' age. A trial sequential analysis provided further support for the anti-pruritic effect of placebo.

CONCLUSIONS

A substantial improvement of pruritus after placebo treatment was observed in patients with chronic urticaria. The anti-pruritic effect of placebo varied with sample size, participants' age, and type of active medication used. Future research should further investigate the effect size of placebo and clarify the potential mechanism.

PROSPERO REGISTRATION

The protocol was registered in the International Prospective Register of Systematic Reviews (PROSPERO) as CRD42023482608.

The potential of Bruton's tyrosine kinase (BTK) inhibitors in the pharmacotherapeutic management of immune and dermatological disease

INTRODUCTION

The review article explores the evolving role of Bruton's tyrosine kinase (BTK) inhibitors in immune-mediated dermatological conditions, addressing significant gaps in current treatment approaches.

AREAS COVERED

The review comprehensively discusses the mechanisms of action of BTK inhibitors, including irreversible and reversible inhibitors. Clinical applications of BTK inhibitors in dermatological diseases such as pemphigus, chronic spontaneous urticaria (CSU), hidradenitis suppurativa (HS), systemic lupus erythematosus (SLE), and atopic dermatitis are explored, highlighting recent advancements and ongoing clinical trials. Potential advantages of BTK inhibitors over existing therapies and challenges in translating preclinical findings to clinical outcomes are discussed.

EXPERT OPINION/COMMENTARY

BTK inhibitors represent a promising therapeutic avenue for immune-mediated dermatological conditions, offering oral administration, targeted pathway inhibition, and a favorable safety profile compared to biologic therapies. Ongoing research and clinical trials hold the potential to address unmet needs and reshape the therapeutic landscape in dermatology.

Chronic Inducible Urticaria

Chronic inducible urticaria (CIndU) is characterized by the appearance of hives (urticaria) and/or angioedema in response to specific triggers or stimuli. For accurate diagnosis, anamnesis-driven specific, and if available, standardized trigger testings, as well as patient reported outcomes, should be applied. The currently recommended treatment algorithm is the same as for chronic spontaneous urticaria but is largely off-label for CIndU. New, and possibly more disease-specific, treatment options are needed for CIndU patients, who are often severely impacted by their disease. Several clinical trials are currently ongoing.

New insights into chronic inducible urticaria

PURPOSE OF REVIEW

Chronic inducible urticaria (CIndU) is a group of long-persisting and challenging to manage diseases, characterized by recurrent wheals and angioedema induced by definite triggers. In this review, we address recent findings on CIndU pathogenesis, diagnosis as well as its treatment, and we discuss novel potential targets that may lead to the development of more effective therapies for CIndU patients.

RECENT ADVANCES

Meaningful advances in the understanding of its pathogenesis have been reported in the last decades. Novel CIndU-specific patient-reported outcome measures enable a closer and better evaluation of patients. CIndU is a hard-to-treat disease that highly impairs quality of life (QoL) of affected patients. Provocation tests allow to diagnose CIndU subtypes. The only licensed and recommended treatment for CIndU are second generation non-sedating H1-antihistamines, which lack efficacy in many cases. Omalizumab off-label use has been assessed in all types of CIndU with overall good outcomes. Promising emerging therapies currently assessed in chronic spontaneous urticaria are paving the path for novel treatments for CIndU.

Emerging Therapeutics in Chronic Urticaria

Chronic urticaria (CU) is a common and long-lasting mast cell-mediated skin disease associated with psychiatric and autoimmune comorbidities, high economic costs, and considerable impact on quality of life. Available therapies show limited efficacy in many CU patients, which may be related to distinct underlying pathophysiology. Targeted and disease-modifying treatments with higher and broader efficacy are needed and are under development for CU. These novel drugs, small molecules, and monoclonal antibodies target mast cells and their receptors, signaling pathways, or mediators and other immune cells. In this article, the authors focus on the most promising emerging therapeutics in advanced development and discuss their potential place in future management of CU.

Chronic urticaria: unmet needs, emerging drugs, and new perspectives on personalised treatment

Chronic urticaria is a common and debilitating mast cell-driven skin disease presenting with itchy wheals, angio-oedema, or both. Chronic urticaria is classified as spontaneous (without definite triggers) and inducible (with definite and subtype-specific triggers; eg, cold or pressure). Current management guidelines recommend step-up administration of second-generation H1-antihistamines to four-fold the approved dose, followed by omalizumab and ciclosporin. However, in many patients, chronic urticaria does not respond to this linear approach due to heterogeneous underlying mechanisms. A personalised endotype-based approach is emerging based on the identification of autoantibodies and other drivers of urticaria pathogenesis. Over the past decade, clinical trials have presented promising options for targeted treatment of chronic urticaria with the potential for disease modification, including Bruton's tyrosine kinase inhibitors, anti-cytokine therapies, and mast cell depletion. This Therapeutics article focuses on the evidence for these novel drugs and their role in addressing an unmet need for personalised management of patients with chronic urticaria.

Benralizumab does not elicit therapeutic effect in patients with chronic spontaneous urticaria: results from the phase IIb multinational randomized double-blind placebo-controlled ARROYO trial

BACKGROUND

Chronic spontaneous urticaria (CSU) is a relatively common skin disease associated with hives and angio-oedema. Eosinophils play a role in CSU pathogenesis. Benralizumab, an anti-interleukin-5 receptor-α monoclonal antibody, has been shown to induce nearly complete depletion of eosinophils.

OBJECTIVES

To determine the clinical efficacy and safety of benralizumab in patients with CSU who were symptomatic despite H1 antihistamine treatment.

METHODS

The 24-week, randomized, double-blind, placebo-controlled, phase IIb portion of the ARROYO trial enrolled adult patients with CSU who were currently on H1 antihistamine treatment. Patients were randomized to one of five treatment groups according to benralizumab dose and regimen for a 24-week treatment period. The primary endpoint was change from baseline in Itch Severity Score (ISS)7 at week 12. The key secondary endpoint was change from baseline in Urticaria Activity Score (UAS)7 at week 12. Additional secondary endpoints included other metrics to assess CSU at week 24, blood eosinophil levels, and pharmacokinetics and immunogenicity assessments. Exploratory subgroup analyses were conducted to explore responses according to demographics, clinical features and biomarkers. Safety was assessed in all treatment groups.

RESULTS

Of 155 patients, 59 were randomized to benralizumab 30 mg, 56 to benralizumab 60 mg and 40 to placebo. Baseline and disease characteristics were consistent with what was expected for patients with CSU. There were no significant differences in change from baseline in ISS7 score at week 12 between benralizumab and placebo [benralizumab 30 mg vs. placebo, least-squares mean difference -1.01, 95% confidence interval (CI) -3.28 to 1.26; benralizumab 60 mg vs. placebo, least-squares mean difference -1.79, 95% CI -4.09 to 0.50] nor in change from baseline in UAS7 score at week 12 between benralizumab and placebo (benralizumab 30 mg vs. placebo, P = 0.407; benralizumab 60 mg vs. placebo, P = 0.082). Depletion of blood eosinophil levels was observed at week 24 in patients treated with benralizumab. All other secondary endpoints and exploratory/subgroup analyses indicated no significant differences between benralizumab and placebo. Safety results were consistent with the known profile of benralizumab.

CONCLUSIONS

Although benralizumab resulted in near-complete depletion of blood eosinophils, there was no clinical benefit over placebo.

Bruton's tyrosine kinase inhibition for the treatment of allergic disorders

IgE signaling through its high-affinity receptor FcεRI is central to the pathogenesis of numerous allergic disorders. Oral inhibitors of Bruton's tyrosine kinase (BTKis), which are currently Food and Drug Administration-approved for treating B cell malignancies, broadly inhibit the FcεRI pathway in human mast cells and basophils, and therefore may be effective allergen-independent therapies for a variety of allergic diseases. The application of these drugs to the allergy space was previously limited by the low kinase selectivity and subsequent toxicities of early-generation compounds. Fortunately, next-generation, highly selective BTKis in clinical development appear to have more favorable risk-benefit profiles, and their likelihood of being Food and Drug Administration-approved for an allergy indication is increasing. Recent clinical trials have indicated the remarkable and rapid efficacy of the second-generation BTKi acalabrutinib in preventing clinical reactivity to peanut ingestion in adults with peanut allergy. In addition, next-generation BTKis including remibrutinib effectively reduce disease activity in patients with antihistamine-refractory chronic spontaneous urticaria. Finally, several BTKis are currently under investigation in early clinical trials for atopic dermatitis and asthma. In this review, we summarize recent data supporting the use of these drugs as novel therapies in food allergy, anaphylaxis, urticaria, and other allergic disorders. We also discuss safety data derived from trials using both short-term and chronic dosing of BTKis.

Importance of IgE-Induced Unique Plasma Leakage in the Skin for Urticaria-Like Symptoms in an Anaphylaxis-Dependent Spotted Distribution of Immune Complex in Skin (ASDIS) Mouse Model

INTRODUCTION

Allergic diseases, such as anaphylaxis and urticaria, pose significant health concerns. The quest for improved prognostic outcomes in these diseases necessitates the exploration of novel therapeutic avenues. To address this need, we have developed a novel mouse model of anaphylaxis, denoted as anaphylaxis-dependent spotted distribution of immune complex in skin (ASDIS). ASDIS manifests as distinct dotted symptoms in the skin, detectable through in vivo imaging, resembling urticarial symptoms. In this study, we investigated the potential underlying mechanisms giving rise to these dotted symptoms, exploring the role of vascular permeability and characterizing the ASDIS model as a new urticaria model.

METHODS

We employed haired and hairless HR mice (BALB/c background) and hairless HR-1 mice (a commercially available hairless strain with an unidentified genetic background). ASDIS was induced by the simultaneous intravenous injection of anti-ovalbumin IgE and fluorescein isothiocyanate (FITC)-ovalbumin, along with Evans blue - a recognized vascular permeability indicator. Anaphylaxis and scratching behavior were monitored through rectal temperature decrease and optical observation, respectively. Histamine, platelet-activating factor, and compound 48/80 were injected with or without FITC-ovalbumin for comparative analysis. The effects of an α1 adrenergic receptor agonist applied to the skin were also examined.

RESULTS

In hairless mice, the simultaneous injection of histamine, compound 48/80, or IgE with FITC-ovalbumin induced comparable rectal temperature decreases and vascular permeability. However, only the combination of FITC-ovalbumin and IgE triggered ASDIS, specifically the dotted urticaria-like symptom. Evans blue visualization and optical observation of dotted swelling confirmed that the vascular permeability mediated the phenomenon. Hairless mice exhibited a more pronounced temperature decrease than their haired counterparts when exposed to histamine, platelet-activating factor, compound 48/80, and IgE with FITC-ovalbumin. The application of an α1 adrenergic receptor agonist to the skin attenuated the topical urticaria-like symptom.

CONCLUSION

Our experiments revealed four findings. The first is that ASDIS mirrors urticaria-like symptoms resulting from increased vascular permeability, akin to human urticaria. The second finding is that the development of dotted symptoms involves an IgE-induced, yet unidentified, mechanism not triggered by histamine or compound 48/80 alone. The third finding highlights the heightened susceptibility of hairless mice to ASDIS induction. The fourth finding demonstrates that the inhibition of ASDIS by the topical application of an α1 adrenergic receptor agonist hints at a potential anti-urticarial application for this vasoconstrictor. Further elucidation of these unidentified IgE-dependent mechanisms and the specific generation of dotted symptoms by IgE-immune complexes could provide novel insights into allergic response processes and therapeutic interventions for these conditions.

A Practical Approach to Diagnosing and Managing Chronic Spontaneous Urticaria

Chronic spontaneous urticaria (CSU) is an unpredictable inflammatory skin condition characterized by the spontaneous onset of itchy wheals, angioedema, or both, which occurs for longer than 6 weeks overall. Despite the relatively straightforward diagnostic algorithm for CSU, relying primarily on a detailed medical history and only limited laboratory tests, patients often wait years to be diagnosed, with many cycling through different healthcare practitioners before a diagnosis is made. Even then, current treatment options for CSU are limited, with approximately half of patients resistant to standard-of-care second-generation antihistamines at standard or higher doses. As such, there is an unmet need for improved, streamlined management for patients with CSU. Here, we review the evidence-based diagnostic algorithm for CSU, consider the required steps of the diagnostic workup, and provide practical, real-world advice on the management of CSU to improve the timely diagnosis and care of patients with this debilitating disease.

Mast cells: a novel therapeutic avenue for cardiovascular diseases?

Mast cells are tissue-resident immune cells strategically located in different compartments of the normal human heart (the myocardium, pericardium, aortic valve, and close to nerves) as well as in atherosclerotic plaques. Cardiac mast cells produce a broad spectrum of vasoactive and proinflammatory mediators, which have potential roles in inflammation, angiogenesis, lymphangiogenesis, tissue remodelling, and fibrosis. Mast cells release preformed mediators (e.g. histamine, tryptase, and chymase) and de novo synthesized mediators (e.g. cysteinyl leukotriene C4 and prostaglandin D2), as well as cytokines and chemokines, which can activate different resident immune cells (e.g. macrophages) and structural cells (e.g. fibroblasts and endothelial cells) in the human heart and aorta. The transcriptional profiles of various mast cell populations highlight their potential heterogeneity and distinct gene and proteome expression. Mast cell plasticity and heterogeneity enable these cells the potential for performing different, even opposite, functions in response to changing tissue contexts. Human cardiac mast cells display significant differences compared with mast cells isolated from other organs. These characteristics make cardiac mast cells intriguing, given their dichotomous potential roles of inducing or protecting against cardiovascular diseases. Identification of cardiac mast cell subpopulations represents a prerequisite for understanding their potential multifaceted roles in health and disease. Several new drugs specifically targeting human mast cell activation are under development or in clinical trials. Mast cells and/or their subpopulations can potentially represent novel therapeutic targets for cardiovascular disorders.

Discovery and Preclinical Characterization of BIIB129, a Covalent, Selective, and Brain-Penetrant BTK Inhibitor for the Treatment of Multiple Sclerosis

Multiple sclerosis (MS) is a chronic disease with an underlying pathology characterized by inflammation-driven neuronal loss, axonal injury, and demyelination. Bruton's tyrosine kinase (BTK), a nonreceptor tyrosine kinase and member of the TEC family of kinases, is involved in the regulation, migration, and functional activation of B cells and myeloid cells in the periphery and the central nervous system (CNS), cell types which are deemed central to the pathology contributing to disease progression in MS patients. Herein, we describe the discovery of BIIB129 (25), a structurally distinct and brain-penetrant targeted covalent inhibitor (TCI) of BTK with an unprecedented binding mode responsible for its high kinome selectivity. BIIB129 (25) demonstrated efficacy in disease-relevant preclinical in vivo models of B cell proliferation in the CNS, exhibits a favorable safety profile suitable for clinical development as an immunomodulating therapy for MS, and has a low projected total human daily dose.

Targeting histamine receptor 4 in cholinergic urticaria with izuforant (LEO 152020): results from a phase IIa randomized double-blind placebo-controlled multicentre crossover trial

BACKGROUND

Cholinergic urticaria (CholU) is a common subtype of chronic inducible urticaria, where signs and symptoms (e.g. pruritic wheals and angioedema) are triggered by sweating due to physical exercise, passive warming and by other sweat-inducing situations. While guidelines recommend treatment with second-generation H1 antihistamines, approximately 90% of patients report uncontrolled disease. Targeting the histamine 4 receptor (H4R) has shown promise in preclinical/clinical studies of allergic/inflammatory diseases. Izuforant (LEO 152020) is a selective oral H4R antagonist with expected dual antipruritic and anti-inflammatory effects.

OBJECTIVES

To assess the effects of izuforant in adults with CholU, a common type of chronic urticaria driven by histamine and characterized by high skin levels of H4R expression.

METHODS

This was a phase IIa randomized double-blind placebo-controlled multicentre crossover trial where patients with CholU with an inadequate response to ≥ 1 standard dose of H1 antihistamine received izuforant 100 mg twice daily or placebo (EUCTR2020-004961-38-DE; NCT04853992). The primary endpoint was change from baseline in Urticaria Activity Score. Exploratory endpoints included CholU activity score over 7 days, urticaria control test, Physician Global Assessment, patient global assessment of severity (PGA-S), provocation tests, Dermatology Life Quality Index and CholU quality of life (CholU-QoL). Pharmacokinetic and pharmacodynamic parameters, and serum biomarkers were assessed, as well as safety and tolerability.

RESULTS

Nineteen patients were randomized and included in the full analysis set; 18 completed treatment [mean (SD) age 29.5 (9.8) years; mean (SD) CholU duration 8.0 (6.3) years]. The primary and most of prespecified exploratory endpoints were not met; there were significant improvements in PGA-S for izuforant vs. placebo (P = 0.02), and nonsignificant improvements for other endpoints in quality of life and histamine skin prick test. All adverse events (AEs) experienced with izuforant were considered mild. The most frequently reported (> 1 patient) were nausea (three patients) and upper abdominal pain (two patients), occurring more frequently with izuforant vs. placebo (one patient each). There were no treatment-related serious AEs and no patient receiving izuforant discontinued the study. Treatment with izuforant did not cause downregulation of H4R.

CONCLUSIONS

This is the first study to explore the role of H4R as a therapeutic target in urticaria. Targeting H4R with izuforant was well tolerated but did not demonstrate significant improvements vs. placebo in the primary endpoint and all but one prespecified exploratory endpoint in CholU.

The effect of Bruton's tyrosine kinase (BTK) inhibitor in the eosinophilic asthma model of mouse

Bruton's Tyrosine kinase (BTK) plays a pivotal role as the key mediator in B cell signaling. Recent research has revealed that it is also expressed in cells critical to asthma development, such as T cells, and eosinophils. This study aims to investigate the potential of BTK inhibitor in eosinophilic asthma mouse model. BALB/c mice were sensitized with ovalbumin (OVA) via intraperitoneal injections and followed by OVA nebulizations. The mice were treated with 250 µg/ml or 500 µg/ml of ibrutinib before the second intraperitoneal injection and the first nebulization. Two days after the last OVA challenge, airway hyperresponsiveness (AHR) was assessed with methacholine, and differential cell count in bronchoalveolar lavage fluid (BALF) was performed. The cytokines were measured in BALF, and serum OVA-specific IgE and IgG antibody levels were evaluated by ELISA. The inhibitory effect of ibrutinib was also evaluated in splenic mononuclear cells, mast cells, eosinophils, and T cells in vitro. Treatment with ibrutinib significantly attenuated AHR and airway inflammation, compared to the OVA-induced positive control. The treatment also reduced IL-4, IL-5, IL-13 and IFN-γ cytokine levels and suppressed OVA-specific IgE and IgG production compared to the OVA-induced positive control. Additionally, ibrutinib decreased beta-hexosaminidase release from mast cells, type 2 cytokine productions from mononuclear cells and T cells, and eosinophilic activation markers in vitro. The results of this study suggest that ibrutinib treatment could exert anti-allergic effects by inactivating B cells and other BTK-expressing cells. Further studies are needed to investigate the potential therapeutic effect of ibrutinib on allergic diseases.

BTK signaling-a crucial link in the pathophysiology of chronic spontaneous urticaria

Chronic spontaneous urticaria (CSU) is an inflammatory skin disorder that manifests with itchy wheals, angioedema, or both for more than 6 weeks. Mast cells and basophils are the key pathogenic drivers of CSU; their activation results in histamine and cytokine release with subsequent dermal inflammation. Two overlapping mechanisms of mast cell and basophil activation have been proposed in CSU: type I autoimmunity, also called autoallergy, which is mediated via IgE against various autoallergens, and type IIb autoimmunity, which is mediated predominantly via IgG directed against the IgE receptor FcεRI or FcεRI-bound IgE. Both mechanisms involve cross-linking of FcεRI and activation of downstream signaling pathways, and they may co-occur in the same patient. In addition, B-cell receptor signaling has been postulated to play a key role in CSU by generating autoreactive B cells and autoantibody production. A cornerstone of FcεRI and B-cell receptor signaling is Bruton tyrosine kinase (BTK), making BTK inhibition a clear therapeutic target in CSU. The potential application of early-generation BTK inhibitors, including ibrutinib, in allergic and autoimmune diseases is limited owing to their unfavorable benefit-risk profile. However, novel BTK inhibitors with improved selectivity and safety profiles have been developed and are under clinical investigation in autoimmune diseases, including CSU. In phase 2 trials, the BTK inhibitors remibrutinib and fenebrutinib have demonstrated rapid and sustained improvements in CSU disease activity. With phase 3 studies of remibrutinib ongoing, it is hoped that BTK inhibitors will present an effective, well-tolerated option for patients with antihistamine-refractory CSU, a phenotype that presents a considerable clinical challenge.

PTGS2: A potential immune regulator and therapeutic target for chronic spontaneous urticaria

AIMS

Chronic spontaneous urticaria (CSU) is a common and debilitating skin disease that is difficult to control with existing treatments, and the pathogenesis of CSU has not been fully revealed. The aim of this study was to explore the underlying mechanisms of CSU and identify potential treatments.

MATERIALS AND METHODS

Microarray datasets of CSU were obtained from Gene Expression Omnibus database. Differentially expressed genes between skin lesions of CSU and normal controls (LNS-DEGs) were identified, and the enrichment analyses of LNS-DEGs were performed. Hub genes of LNS-DEGs were selected by protein-protein interaction analysis. The co-expression and transcriptional regulatory networks of hub genes were conducted using GeneMANIA and TRRUST database, respectively. CIBERSORT was utilized for immune cell infiltration analysis. Experimental validation was performed by β-hexosaminidase release examination and passive cutaneous anaphylaxis (PCA) mouse model.

KEY FINDINGS

A total of 247 LNS-DEGs were identified, which were enriched in cell migration, cell chemotaxis, and inflammatory pathways such as TNF and interleukin (IL) -17 signaling pathway. Among LNS-DEGs, seven upregulated (PTGS2, CCL2, IL1B, CXCL1, IL6, VCAM1, ICAM1) and one downregulated hub gene (PECAM1) were selected. Immune infiltration analysis identified eight different immune cells, such as activated/resting mast cells and neutrophils. Furthermore, PTGS2, encoding cyclooxygenase 2 (COX2), was selected for further validation. COX2 inhibitor, celecoxib, significantly inhibited mast cell degranulation, and reduced vascular permeability and inflammatory cytokine expression in PCA mouse model.

SIGNIFICANCE

PTGS2 may be a potential regulator of immunity and inflammation in CSU. Targeting PTGS2 is a new perspective for CSU treatment.

A review of Bruton's tyrosine kinase inhibitors in multiple sclerosis

Bruton's tyrosine kinase (BTK) inhibitors are an emerging class of therapeutics in multiple sclerosis (MS). BTK is expressed in B-cells and myeloid cells, key progenitors of which include dendritic cells, microglia and macrophages, integral effectors of MS pathogenesis, along with mast cells, establishing the relevance of BTK inhibitors to diverse autoimmune conditions. First-generation BTK inhibitors are currently utilized in the treatment of B-cell malignancies and show efficacy in B-cell modulation. B-cell depleting therapies have shown success as disease-modifying treatments (DMTs) in MS, highlighting the potential of BTK inhibitors for this indication; however, first-generation BTK inhibitors exhibit a challenging safety profile that is unsuitable for chronic use, as required for MS DMTs. A second generation of highly selective BTK inhibitors has shown efficacy in modulating MS-relevant mechanisms of pathogenesis in preclinical as well as clinical studies. Six of these BTK inhibitors are undergoing clinical development for MS, three of which are also under investigation for chronic spontaneous urticaria (CSU), rheumatoid arthritis (RA) and systemic lupus erythematosus (SLE). Phase II trials of selected BTK inhibitors for MS showed reductions in new gadolinium-enhancing lesions on magnetic resonance imaging scans; however, the safety profile is yet to be ascertained in chronic use. Understanding of the safety profile is developing by combining safety insights from the ongoing phase II and III trials of second-generation BTK inhibitors for MS, CSU, RA and SLE. This narrative review investigates the potential of BTK inhibitors as an MS DMT, the improved selectivity of second-generation inhibitors, comparative safety insights established thus far through clinical development programmes and proposed implications in female reproductive health and in long-term administration.

Current and emerging drugs for the treatment of pruritus: an update of the literature

INTRODUCTION

Pruritus, particularly in its chronic form, often imposes significant suffering and reductions in patients' quality of life. The pathophysiology of itch is varied depending on disease context, creating opportunities for unique drug development and multimodal therapy.

AREAS COVERED

The purpose of this article is to provide an update of the literature regarding current and emerging therapeutics in itch. We review the multitudes of drug targets available and corresponding drugs that have shown efficacy in clinical trials, with a particular emphasis on phase 2 and 3 trials and beyond. Broadly, these targets include therapies directed against type 2 inflammation (i.e. Th2 cytokines, JAK/STAT, lipid mediators, T-cell mediators, and other enzymes and receptors) and neural receptors and targets (i.e. PARs, TRP channels, opioid receptors, MRGPRs, GABA receptors, and cannabinoid receptors).

EXPERT OPINION

Therapeutics for itch are emerging at a remarkable pace, and we are entering an era with more and more specialized therapies. Increasingly, these treatments are able to relieve itch beyond their effect on inflammation by directly targeting the neurosensory system.

Efficacy and safety of remibrutinib, a selective potent oral BTK inhibitor, in Sjögren's syndrome: results from a randomised, double-blind, placebo-controlled phase 2 trial

OBJECTIVES

To evaluate the safety and efficacy of remibrutinib in patients with moderate-to-severe Sjögren's syndrome (SjS) in a phase 2 randomised, double-blind trial (NCT04035668; LOUiSSE (LOU064 in Sjögren's Syndrome) study).

METHODS

Eligible patients fulfilling 2016 American College of Rheumatology/European League Against Rheumatism (EULAR) criteria for SjS, positive for anti-Ro/Sjögren's syndrome-related antigen A antibodies, with moderate-to-severe disease activity (EULAR Sjögren's Syndrome Disease Activity Index (ESSDAI) (based on weighted score) ≥ 5, EULAR Sjögren's Syndrome Patient Reported Index (ESSPRI) ≥ 5) received remibrutinib (100 mg) either one or two times a day, or placebo for the 24-week study treatment period. The primary endpoint was change from baseline in ESSDAI at week 24. Key secondary endpoints included change from baseline in ESSDAI over time, change from baseline in ESSPRI over time and safety of remibrutinib in SjS. Key exploratory endpoints included changes to the salivary flow rate, soluble biomarkers, blood transcriptomic and serum proteomic profiles.

RESULTS

Remibrutinib significantly improved ESSDAI score in patients with SjS over 24 weeks compared with placebo (ΔESSDAI -2.86, p=0.003). No treatment effect was observed in ESSPRI score (ΔESSPRI 0.17, p=0.663). There was a trend towards improvement of unstimulated salivary flow with remibrutinib compared with placebo over 24 weeks. Remibrutinib had a favourable safety profile in patients with SjS over 24 weeks. Remibrutinib induced significant changes in gene expression in blood, and serum protein abundance compared with placebo.

CONCLUSIONS

These data show preliminary efficacy and favourable safety of remibrutinib in a phase 2 trial for SjS.

Mast Cell-Targeting Therapies in Mast Cell Activation Syndromes

PURPOSE OF REVIEW

Provide an overview of the expanding landscape of mast cell (MC)-targeting treatments in mast cell activation syndromes (MCAS).

RECENT FINDINGS

Tyrosine-kinase inhibitors (TKIs) targeting wild-type and mutated KIT can efficiently induce MC depletion. Avapritinib and midostaurin can also temper IgE-mediated degranulation. Avapritinib has been recently approved by the FDA for the treatment of indolent systemic mastocytosis (ISM). Targeting activation pathways and inhibitory receptors is a promising therapeutic frontier. Recently, the anti Siglec-8 antibody lirentelimab showed promising results in ISM. MCAS is a heterogeneous disorder demanding a personalized therapeutic approach and, especially when presenting as anaphylaxis, has not been formally captured as outcome in prospective clinical trials with TKI. Long-term safety of TKI needs to be addressed. New drugs under investigation in diseases in which non-neoplastic MCs play a pivotal role can provide important inputs to identify new efficient and safe treatments for MCAS.