A multicenter, open-label, uncontrolled, single-arm phase 2 study of tirabrutinib, an oral Bruton's tyrosine kinase inhibitor, in pemphigus

Bruton Tyrosine Kinase Inhibition: an Effective Strategy to Manage Waldenström Macroglobulinemia

PURPOSE OF REVIEW

The treatment of Waldenström macroglobulinemia (WM) has evolved over the past decade. With the seminal discoveries of MYD88 and CXCR warts, hypogammaglobulinemia, infections, and myelokathexis (WHIM) mutations in WM cells, our understanding of the disease biology and treatment has improved. The development of a new class of agents, Bruton tyrosine kinase inhibitors (BTKi), has substantially impacted the treatment paradigm of WM. Herein, we review the current and emerging BTKi and the evidence for their use in WM.

RECENT FINDINGS

Clinical trials have established the role of covalent BTKi in the treatment of WM. Their efficacy is compromised among patients who harbor CXCR4WHIM mutation or MYD88WT genotype. The development of BTKC481 mutation-mediated resistance to covalent BTKi may lead to disease refractoriness. Novel, non-covalent, next-generation BTKi are emerging, and preliminary results of the early phase clinical trials show promising activity in WM, even among patients refractory to a covalent BTKi. Covalent BTK inhibitors have demonstrated meaningful outcomes in treatment-naïve (TN) and relapsed refractory (R/R) WM, particularly among those harboring the MYD88L265P mutation. The next-generation BTKi demonstrate improved selectivity, resulting in a more favorable toxicity profile. In WM, BTKi are administered until progression or the development of intolerable toxicity. Consequently, the potential for acquired resistance, the emergence of cumulative toxicities, and treatment-related financial burden are critical challenges associated with the continuous therapy approach. By circumventing BTK C481 mutations that alter the binding site to covalent BTKi, the non-covalent BTKi serve as alternative agents in the event of acquired resistance. Head-to-head comparative trials with the conventional chemoimmunotherapies are lacking. The findings of the RAINBOW trial (NCT046152), comparing the dexamethasone, rituximab, and cyclophosphamide (DRC) regimen to the first-generation, ibrutinib are awaited, but more studies are needed to draw definitive conclusions on the comparative efficacy of chemoimmunotherapy and BTKi. Complete response is elusive with BTKi, and combination regimens to improve upon the efficacy and limit the treatment duration are also under evaluation in WM.

What is novel in the clinical management of pemphigus vulgaris?

INTRODUCTION

Pemphigus, an uncommon autoimmune blistering disorder affecting the skin and mucous membranes, currently with mortality primarily attributed to adverse reactions resulting from treatment protocols. Additionally, the existing treatments exhibit a notable recurrence rate. The high incidence of relapse and the considerable adverse effects associated with treatment underscore the imperative to explore safer and more effective therapeutic approaches. Numerous potential therapeutic targets have demonstrated promising outcomes in trials or preliminary research stages. These encompass anti-CD-20 agents, anti-CD-25 agents, TNF-α inhibition, FAS Ligand Inhibition, FcRn inhibition, BAFF inhibition, Bruton's tyrosine kinase (BTK) inhibition, CAAR T Cells, JAK inhibition, mTOR inhibition, abatacept, IL-4 inhibition, IL-17 inhibition, IL-6 inhibition, polyclonal Regulatory T Cells, and autologous hematopoietic stem cell transplantation.

AREAS COVERED

The most significant studies regarding the impact and efficacy of the mentioned treatments on pemphigus were meticulously curated through a comprehensive search conducted on the PubMed database. Moreover, the investigations of interest cited in these studies were also integrated.

EXPERT OPINION

The efficacy and safety profiles of the other treatments under discussion do not exhibit the same level of robustness as anti-CD20 therapy, which is anticipated to endure as a critical element in pemphigus treatment well into the foreseeable future.

Efficacy and safety of Bruton's tyrosine kinase inhibitors in the treatment of pemphigus: A comprehensive literature review and future perspective

Bruton's tyrosine kinase (BTK) is a protein involved in B-cell-receptor signaling and B-cell proliferation. The pathophysiology of several autoimmune diseases, such as pemphigus disorder, relies on the BTK signaling pathway. Therefore, BTK inhibitors were found to be beneficial alternatives to conventional treatmentsThe current study aimed to assess the efficacy and safety of BTK inhibitors in treating pemphigus. A complete search was performed on databases including PubMed/MedLine, Scopus, Web of Science, as well as Google Scholar search engine for studies published by September 20th, 2023. The current review indicates that BTK inhibitors alone or in combination with conventional treatments are promising options in the management of pemphigus. The overall safety profile of BTK inhibitors has been acceptable, and the reported adverse reactions were not severe or life-threatening.

B-cell targeted therapy of pemphigus

Pemphigus is an autoimmune disease that causes blistering and erosion of the skin and mucous membranes because of autoantibodies against desmoglein, which plays an important role in adhesion between epidermal keratinocytes. Treatment of pemphigus has long been centered on corticosteroids, and the guidelines for management of pemphigus have recommended high-dose systemic corticosteroids as the first-line treatment. While guideline-based treatment has been shown to be beneficial in patients with pemphigus, it has also become clear that this treatment is accompanied by significant burden and risk. The challenge for future pemphigus treatment is to maximize efficacy while minimizing risk during the course of the disease. In this regard, treatment targeting B cells is expected to become increasingly important as autoreactive B cells in pemphigus patients are thought to play a major role in the production of autoantibodies, which form the basis of the pathogenesis. The recent expansion of insurance coverage to rituximab, a monoclonal antibody against CD20, for refractory pemphigus in the USA, Europe, and Japan has opened up a new era of pemphigus treatment by enabling treatment strategies with drugs targeting B cells in patients. Here, we discuss the current status and future prospects of pemphigus treatment, focusing on rituximab and Bruton's tyrosine kinase inhibitors, which are expected to become essential drugs for pemphigus treatment in the future.

[Pemphigus: current and future treatment strategies]

Pemphigus diseases are a group of organ-specific autoimmune diseases which are characterised by the production of autoantibodies against intra-epidermal adhesion molecules and structural proteins of skin and mucosae. Depending on the entity, patients develop blisters and erosions on the skin and/or mucosae. According to the AWMF S2k guidelines for diagnosis and therapy of pemphigus diseases, a systemic therapy is recommended. Initially, high-dose, oral corticosteroids in combination with immunosuppressive drugs as corticosteroid-sparing agent, usually azathioprine or mycophenolate mofetil, can be used. Furthermore, rituximab, a monoclonal antibody directed against CD20 on B cells, was recently approved for pemphigus vulgaris and moderate or severe pemphigus foliaceus.

BTK inhibitors in the treatment of hematological malignancies and inflammatory diseases: mechanisms and clinical studies

Bruton's tyrosine kinase (BTK) is an essential component of multiple signaling pathways that regulate B cell and myeloid cell proliferation, survival, and functions, making it a promising therapeutic target for various B cell malignancies and inflammatory diseases. Five small molecule inhibitors have shown remarkable efficacy and have been approved to treat different types of hematological cancers, including ibrutinib, acalabrutinib, zanubrutinib, tirabrutinib, and orelabrutinib. The first-in-class agent, ibrutinib, has created a new era of chemotherapy-free treatment of B cell malignancies. Ibrutinib is so popular and became the fourth top-selling cancer drug worldwide in 2021. To reduce the off-target effects and overcome the acquired resistance of ibrutinib, significant efforts have been made in developing highly selective second- and third-generation BTK inhibitors and various combination approaches. Over the past few years, BTK inhibitors have also been repurposed for the treatment of inflammatory diseases. Promising data have been obtained from preclinical and early-phase clinical studies. In this review, we summarized current progress in applying BTK inhibitors in the treatment of hematological malignancies and inflammatory disorders, highlighting available results from clinical studies.

Ibrutinib-Associated Cardiotoxicity: From the Pharmaceutical to the Clinical

Ibrutinib is the first-in-class Bruton tyrosine kinase (BTK) inhibitor that has revolutionized the treatment of B cell malignancies. Unfortunately, increased incidences of cardiotoxicity have limited its use. Despite over a decade of research, the biological mechanisms underlying ibrutinib cardiotoxicity remain unclear. In this review, we discuss the pharmacological properties of ibrutinib, the incidence and mechanisms of ibrutinib-induced cardiotoxicity, and practical management to prevent and treat this condition. We also synopsize and discuss the cardiovascular adverse effects related to other more selective BTK inhibitors, which may guide the selection of appropriate BTK inhibitors.

Immunotherapy for Pemphigus: Present and Future

Pemphigus is a chronic and severe autoimmune bullous disease caused by autoantibodies targeting adhesion molecules between keratinocytes. It requires 2–3 years on average to manage the disease. To date, although Rituximab combined with short-term systemic glucocorticoids was accepted as first-line therapy, systemic glucocorticoids remain the primary therapeutic option for pemphigus patients, successfully decreasing morbidity and mortality from pemphigus. However, novel therapeutic strategies are desirable due to the low efficacy in some subset of patients and the long-term severe adverse effects of traditional therapies. Recently, immunotherapy has proved to be encouraging for disease control or cure. Based on the current understanding of the immune mechanisms of pemphigus, we review the immune targets and corresponding agents applied in practice or under clinical trials. The goals of the novel treatments are to improve the quality of life of pemphigus patients by improving efficacy and safety, minimizing side effects, achieving fast disease control, or curing the disease.

Translational autoimmunity in pemphigus and the role of novel Bruton tyrosine kinase inhibitors

Bruton tyrosine kinase (BTK) is involved in a multifarious inflammatory and autoimmune process. As a result, BTK has emerged as a promising novel remedial target for amalgamated autoimmune diseases. Medicament corporations have recently devoted considerable attention to the evolution of BTK inhibitors. Pemphigus is an uncommon and often fatal autoimmune illness. Blisters and erosions on cutaneous surfaces and mucous membranes are crippling symptoms of pemphigus vulgaris, which are caused by immunoglobulin G autoantibodies binding to keratinocyte proteins, resulting in keratinocyte adhesion defects. Although systemic corticosteroids and adjuvant medications are used to treat pemphigus, some patients are resistant to these. BTK inhibitors inhibit B-cell signaling, which is clinically useful in treating pemphigus. Assorted clinical trials are underway to assess the safety, tolerability, and pharmacokinetics of distinct BTK inhibitors, including PRN473 and remibrutinib. The current review evaluates translational autoimmunity in pemphigus and discusses BTK inhibitors in the treatment of pemphigus.

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Pemphigus is severe, and potentially fatal B-cell-mediated autoimmune illness.

•Systemic corticosteroids are used to treat pemphigus, some patients are resistant.

•Bruton Tyrosine Kinase (BTK) is involved in a variety of auto-immune processes.

•As a result, BTK has emerged as a new therapeutic target including pemphigus.

•The current review evaluates the translational autoimmunity in pemphigus.

•This review also depicts the role of BTK inhibitors in treatment of pemphigus.

Bruton's tyrosine kinase inhibition-An emerging therapeutic strategy in immune-mediated dermatological conditions

Bruton's tyrosine kinase (BTK), a member of the Tec kinase family, is critically involved in a range of immunological pathways. The clinical application of BTK inhibitors for B‐cell malignancies has proven successful, and there is strong rationale for the potential benefits of BTK inhibitors in some autoimmune and allergic conditions, including immune‐mediated dermatological diseases. However, the established risk‐to‐benefit profile of “first‐generation” BTK inhibitors cannot be extrapolated to these emerging, non‐oncological, indications. “Next‐generation” BTK inhibitors such as remibrutinib and fenebrutinib entered clinical development for chronic spontaneous urticaria (CSU); rilzabrutinib and tirabrutinib are being studied as potential treatments for pemphigus. Promising data from early‐phase clinical trials in CSU suggest potential for these agents to achieve strong pathway inhibition, which may translate into measurable clinical benefits, as well as other effects such as the disruption of autoantibody production. BTK inhibitors may help to overcome some of the shortcomings of monoclonal antibody treatments for immune‐mediated dermatological conditions such as CSU, pemphigus, and systemic lupus erythematosus. In addition, the use of BTK inhibitors may improve understanding of the pathophysiological roles of mast cells, basophils, and B cells in such conditions.

Immunopathology and Immunotherapy of Inflammatory Skin Diseases

Recently, there have been impressive advancements in understanding of the immune mechanisms underlying cutaneous inflammatory diseases. To understand these diseases on a deeper level and clarify the therapeutic targets more precisely, numerous studies including in vitro experiments, animal models, and clinical trials have been conducted. This has resulted in a paradigm shift from non-specific suppression of the immune system to selective, targeted immunotherapies. These approaches target the molecular pathways and cytokines responsible for generating inflammatory conditions and reinforcing feedback mechanisms to aggravate inflammation. Among the numerous types of skin inflammation, psoriasis and atopic dermatitis (AD) are common chronic cutaneous inflammatory diseases. Psoriasis is a IL-17–mediated disease driven by IL-23, while AD is predominantly mediated by Th2 immunity. Autoimmune bullous diseases are autoantibody-mediated blistering disorders, including pemphigus and bullous pemphigoid. Alopecia areata is an organ-specific autoimmune disease mediated by CD8⁺ T-cells that targets hair follicles. This review will give an updated, comprehensive summary of the pathophysiology and immune mechanisms of inflammatory skin diseases. Moreover, the therapeutic potential of current and upcoming immunotherapies will be discussed.