Subcutaneous veltuzumab, a humanized anti-CD20 antibody, in the treatment of refractory pemphigus vulgaris

Updates on the Management of Autoimmune Bullous Diseases

Background

Autoimmune bullous diseases are associated with high morbidity and mortality. Traditionally, systemic corticosteroids and conventional immunosuppressive agents have been the mainstay of treatment, but their broad immunosuppressive effects and long-term complications have prompted the exploration of newer more targeted therapies.

Materials and Methods

This review explores the evolving landscape of therapeutic options for immunobullous diseases, with a particular focus on pemphigus, bullous pemphigoid (BP), and mucous membrane pemphigoid, by searching PubMed, clinicaltrials.gov, and Cochrane databases for published literature from 2014 to 2023.

Results/Discussion

We discuss emerging treatments for pemphigus such as B cell modulatory drugs, anti-inflammatory drugs, those inhibiting autoantibody half-life or blister-inducing activity, and stem cell therapy, while offering insights into the level of evidence, potential benefits, and limitations of each approach. The role of biologics and novel therapies like rituximab, omalizumab, and dupilumab in reshaping the management of BP is also discussed.

Conclusion

The article highlights the need for further research, clinical trials, and comparative studies to determine the most effective and safest treatment options for patients with immunobullous diseases.

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.

Targeting therapy in pemphigus: Where are we now and where are we going?

Pemphigus is a heterogeneous group of autoimmune skin disorders characterized by blistering of the skin and mucosal membranes, potentially affecting the quality of life if left unchecked. The current mainstay of treatment is systemic corticosteroids and immunosuppressive agents. Nevertheless, long-term use of these drugs can easily cause infections and other life-threatening adverse reactions. Thus, currently, researchers are trying to develop new and safer therapeutic approaches. Specifically, targeted therapies to pathogenic immune pathways have been gradually introduced and used for the treatment of pemphigus or in clinical trials, such as monoclonal anti-CD20 antibody, BAFF inhibitor, BTK inhibitor, CAAR-T therapy, FcRn antagonist, and TNF-α inhibitor. In addition, IL-4Rα antibody, IL-17 blockade, mTOR pathway inhibitor, CTLA-4Ig, and p38 MAPK inhibitors are theoretically promising treatment for pemphigus. Here, we review the research progress on the mechanism of targeted therapies for pemphigus.

Review of an Anti-CD20 Monoclonal Antibody for the Treatment of Autoimmune Diseases of the Skin

Biologic therapies targeting B-cells are emerging as an effective strategy to treat a variety of immune-mediated diseases. One of the most studied B-cell-targeted therapies is rituximab, an anti-CD20 monoclonal antibody that exemplifies B-cell depletion therapy and has served as the prototype for other anti-CD20 monoclonal antibodies and the development of biosimilars. While there are multiple studies on the use of rituximab in dermatology, a comprehensive review of rituximab therapy in autoimmune skin conditions is lacking. In this literature review, we summarize indications, treatment efficacy, and safety of rituximab among common autoimmune diseases of the skin: pemphigus vulgaris, cutaneous lupus erythematous, dermatomyositis, systemic sclerosis, thyroid dermopathy, autoimmune pemphigoid diseases, and cutaneous vasculitis diseases. Existing data on rituximab support the approach of rituximab, biosimilars, and newer B-cell-targeting therapies in immune-mediated cutaneous diseases. Overall, rituximab, which targets CD20, provides an effective alternative or concomitant option to traditional immunosuppressants in the management of various autoimmune diseases of the skin. Further studies are necessary to expand the understanding and possible utility of B-cell-targeted therapies among autoimmune skin diseases.

[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.

Cost-Utility Analysis of Rituximab vs Mycophenolate Mofetil for the Treatment of Pemphigus Vulgaris

Importance

There is an increasing body of literature that supports the use of rituximab as a first-line steroid-sparing agent in pemphigus vulgaris. However, the cost of rituximab is substantial compared with conventional agents, and there are limited health economic data to justify its use.

Objective

To evaluate the cost-effectiveness of rituximab biosimilars relative to mycophenolate mofetil as a first-line steroid-sparing agent for moderate to severe pemphigus vulgaris.

Design, Setting, and Participants

A cost-utility analysis over a 24-month time horizon was conducted from the perspective of the Australian health care sector using a modeled cohort of treatment-naive adult patients with moderate to severe pemphigus vulgaris. A Markov cohort model was constructed to simulate disease progression following first-line treatment with rituximab biosimilars or mycophenolate mofetil. The simulated cohort transitioned between controlled disease, uncontrolled disease, and death. Efficacy and utility data were obtained from available published literature. Cost data were primarily obtained from published government data. One-way and probabilistic sensitivity analyses were performed to assess uncertainty. Primary outcomes were the changes in cost and quality-adjusted life-years (QALYs), and incremental cost-effectiveness ratio (ICER) over the 24 months.

Interventions

Rituximab biosimilars and mycophenolate mofetil.

Results

The simulated cohort of treatment-naive patients had a mean age of 50.8 years, a female-to-male ratio of 1.24, and moderate to severe disease as classified by the Harman criteria. First-line rituximab biosimilars were associated with a cost reduction of AU$639 and an improvement of 0.07 QALYs compared with mycophenolate mofetil, resulting in an ICER of -AU$8818/QALY. Rituximab biosimilars were therefore more effective and less costly compared with mycophenolate mofetil. Sensitivity analyses demonstrated that rituximab biosimilars remained cost-effective across a range of values for cost, utility, and transition probability input parameters and willingness-to-pay thresholds.

Conclusions and Relevance

In this cost-utility analysis, rituximab biosimilars were cost-effective compared with mycophenolate mofetil for moderate to severe pemphigus vulgaris. Further investigation into its cost-effectiveness over a longer time horizon is necessary, but the favorable results of this study suggest that the high acquisition costs of rituximab biosimilars may be offset by its effectiveness and provide economic evidence in support of its listing on the Pharmaceutical Benefits Scheme for pemphigus vulgaris.

Current and Innovated Managements for Autoimmune Bullous Skin Disorders: An Overview

Autoimmune bullous skin disorders are a group of disorders characterized by the formation of numerous blisters and erosions on the skin and/or the mucosal membrane, arising from autoantibodies against the intercellular adhesion molecules and the structural proteins. They can be classified into intraepithelial or subepithelial autoimmune bullous dermatoses based on the location of the targeted antigens. These dermatoses are extremely debilitating and fatal in certain cases, depending on the degree of cutaneous and mucosal involvement. Effective treatments should be implemented promptly. Glucocorticoids serve as the first-line approach due to their rapid onset of therapeutic effects and remission of the acute phase. Nonetheless, long-term applications may lead to major adverse effects that outweigh the benefits. Hence, other adjuvant therapies are mandatory to minimize the potential harm and ameliorate the quality of life. Herein, we summarize the current therapeutic strategies and introduce promising therapies for intractable autoimmune bullous diseases.

Immunogenicity of Monoclonal Antibodies and the Potential Use of HLA Haplotypes to Predict Vulnerable Patients

The use of monoclonal antibodies (mAbs) in the clinic has successfully expanded to treatment of cancer, viral infections, inflammations, and other indications. However, some of the classes of mAbs that are used in the clinic show the formation of anti-drug antibodies (ADAs) leading to loss of efficacy. This review describes ADA formation for the various mAbs, and its clinical effect. Lastly, this review considers the use of HLA-haplotypes as biomarkers to predict vulnerability of patients sensitive to formation of ADAs.

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.

Autoimmune Pemphigus: Latest Advances and Emerging Therapies

Pemphigus represents a group of rare and severe autoimmune intra-epidermal blistering diseases affecting the skin and mucous membranes. These painful and debilitating diseases are driven by the production of autoantibodies that are mainly directed against the desmosomal adhesion proteins, desmoglein 3 (Dsg3) and desmoglein 1 (Dsg1). The search to define underlying triggers for anti-Dsg-antibody production has revealed genetic, environmental, and possible vaccine-driven factors, but our knowledge of the processes underlying disease initiation and pathology remains incomplete. Recent studies point to an important role of T cells in supporting auto-antibody production; yet the involvement of the myeloid compartment remains unexplored. Clinical management of pemphigus is beginning to move away from broad-spectrum immunosuppression and towards B-cell-targeted therapies, which reduce many patients’ symptoms but can have significant side effects. Here, we review the latest developments in our understanding of the predisposing factors/conditions of pemphigus, the underlying pathogenic mechanisms, and new and emerging therapies to treat these devastating diseases.

Comprehensive review on the pathophysiology, clinical variants and management of pemphigus (Review)

Pemphigus represents a group of chronic inflammatory disorders characterized by autoantibodies that target components of desmosomes, leading to the loss of intercellular adhesion between keratinocytes and causing intraepithelial blistering. The pemphigus group consists of four main clinical types with several variants: pemphigus vulgaris (with pemphigus vegetans and pemphigus herpetiformis as variants), pemphigus foliaceus, paraneoplastic pemphigus and IgA pemphigus (with two clinical variants: intraepidermal neutrophilic IgA dermatosis and subcorneal pustular dermatosis). Genetic factors are involved in the pathogenesis, with HLA-DR4 (DRB1*0402) and HLA-DRw6 (DQB1*0503) allele more common in patients with pemphigus vulgaris, HLA class II DRB1*0344 and HLA Cw*1445 correlated with paraneoplastic pemphigus, and HLA-DRB1*04:01, HLA-DRB1*04:06, HLA-DRB1*01:01, HLA-DRB1*14, associated with a higher risk of developing pemphigus foliaceus. Autoantibodies are conducted against structural desmosomal proteins in the skin and mucous membranes, mainly desmogleins, desmocollins and plakins. Cell-mediated immunity may also play a role, especially in paraneoplastic pemphigus. Patients may present erythema, blisters, erosions, and ulcers that may affect the skin, as well as mucosal surfaces of the oral cavity, eyes, nose, leading to severe complaints including pain, dysphagia, and fetor. Oral mucosal postbullous erosive lesions are frequently the first sign of disease in pemphigus vulgaris and in paraneoplastic pemphigus, without skin involvement, making the diagnosis difficult. Treatment options classically include immunosuppressive agents, such as corticosteroids and corticosteroid-sparing agents such as azathioprine, mycophenolate mofetil, cyclophosphamide, methotrexate or dapsone. Newer therapies focus on blocking cell signaling events induced by pathogenic autoantibodies and/or targeting specific autoantibodies. The disease evolution is conditioned by the treatment with maximum doses of corticosteroids and the side effects associated with long-term immunosuppressive therapy, which is why patients need a multidisciplinary approach in following the treatment. In this review, we provide a comprehensive overview of the epidemiology, pathophysiology, clinical aspect, diagnosis and management of the main intraepidermal blistering diseases from the pemphigus group.

Biologics in autoimmune bullous diseases: Current scenario

Autoimmune bullous diseases can be intraepidermal (pemphigus group of disorders) or subepidermal (pemphigoid group of disorders). The treatment of these disorders chiefly comprises corticosteroids and immunosuppressant adjuvants like azathioprine and mycophenolate mofetil. Autoantibodies are the main mediators of these diseases. Rituximab, a chimeric anti-CD20 monoclonal antibody targeting B-cells, has emerged as an excellent treatment option for refractory pemphigus vulgaris in the last decade. Since then, many new biologics have been proposed/explored for managing autoimmune bullous diseases. These hold potential for greater efficacy and lesser adverse effects than conventional immunosuppressants. In this review, we discuss the role of various biologics in the treatment of autoimmune bullous diseases, followed by a brief discussion on the drawbacks to their use and new developments in this area.

De-escalation of anti-CD20 monoclonal antibody (Rituximab) protocols in Pemphigus Vulgaris - a systematic review

Introduction: This review assesses current evidence supporting dose de-escalated rituximab therapy in pemphigus vulgaris, compared to standard protocols. Primary outcome measures were remission and relapse rates. Adverse effects, cumulative steroid dosages, and serological markers of disease activity were also reported.Areas covered: A literature search was performed to look for reports describing the use of de-escalated rituximab therapy in pemphigus vulgaris. Results from heterogenous studies showed a large variation in remission and relapse rates. Complete remission rates from de-escalated treatment ranged from 41.7 to 100.0%, while rates in the control groups ranged from 60.0 to 90.9%. Relapse rates varied from 8.0 to 81.3% in the de-escalated group and from 0.0 to 72.4% in the control group. Of the 165 patients included in this report, only two major adverse effects were reported.Expert Opinion: Overall, dose de-escalated rituximab protocols reported to date appear effective and safe. However, it is unclear if treatment effect parallels that of standard regimens in regard to disease control in the long term. A lower limit of effective dosing for rituximab in pemphigus vulgaris has not yet been reached or defined. The role for and timing of repeated cycles of low-dose rituximab therapy require further exploration.

Immunobullous disease

Immunobullous diseases are blistering cutaneous disorders that are caused by pathogenic antibodies binding to protein targets within the skin. There are a range of immunobullous disorders with characteristic morphology that relates to the structural properties of the target protein. In this article we will describe the pathogenesis, clinical features and treatment of the most common immunobullous disorders.

Exploring the role of immunotherapeutic drugs in autoimmune diseases: A comprehensive review

Autoimmune diseases are group of disorders where an immune response is mounted against the self. The prevalence and burden of this well established and recognised entity is on the rise. Irrespective of being a systemic or organ specific autoimmune disorder, the common underlying mechanism of action, is the imbalance in immune system resulting in loss of tolerance to self-antigens. The oral cavity is no alien to these disorders or to their influences. Pemphigus group of lesions, systemic lupus erythematosus, psoriasis and even Sjogren's syndrome are some of the established autoimmune disorders with prominent oral manifestations. Though these diseases are well documented and enumerated, however addressing them is where the dilemma lies. Science, research and discoveries are a crucial part of medical discipline which help in looking beyond the horizon. With the introduction of selective targeted immunotherapies for autoimmune diseases as a treatment modality either in solitary or in combination with the conventional immunosuppressive treatments, are emerging as a promising elixir for patients enduring them. However, being unique, exploration of these biologics from its inception, to its mechanism of action, recognition of its application and evaluation of its safety norms are equally vital. Therefore, this review aims to provide a comprehensive particular on the novel biologics, the immunotherapies in autoimmune disorders targeting the different cells, their receptors or cytokines of the immune system.

Clinical and biological activity of rituximab in the treatment of pemphigus

B-cells are major effector cells in autoimmunity since they differentiate into plasmocytes that produce pathogenic auto-antibody such as anti-desmoglein antibodies in pemphigus patients. Major advances were obtained using whole B-cell depleting therapies including anti-CD20 antibodies in refractory pemphigus patients that lead to rituximab approval in pemphigus patients in EU and USA. This review summarizes the data supporting the efficacy of rituximab in pemphigus and provides an overview of the reported immunological changes underlying its therapeutic action. Short and long-term remission in pemphigus is explained by the removal of autoreactive B-cells involved in the production of pathogenic IgG auto-antibodies and by enhancement of the appearance of regulatory B-cells that could maintain long term immune tolerance.

Novel Therapies for Pemphigus Vulgaris

Pemphigus vulgaris (PV) is a severe chronic autoimmune blistering disease that affects the skin and mucous membranes. It is characterized by suprabasal acantholysis due to disruption of desmosomal connections between keratinocytes. Autoantibodies against desmosomal cadherins, desmoglein 3 and 1, have been shown to induce disease. Certain human leukocyte antigen (HLA) types and non-HLA foci confer genetic susceptibility. Until the discovery of corticosteroids in the 1950s, PV was 75% fatal. Since then, multiple PV treatments, such as systemic corticosteroids and adjunctive therapy with immunosuppressive medications (mycophenolate mofetil, azathioprine, cyclophosphamide, cyclosporine, methotrexate, gold, and others) have been introduced; however, none have led to long-term remissions and many have undesired adverse effects. Our growing understanding of the pathophysiologic mechanisms in PV is leading to development of new targeted therapies, such as intravenous immunoglobulin, anti-CD20 monoclonal antibodies, inhibitors of Bruton tyrosine kinase and neonatal Fc receptors, and adoptive cellular transfer, that may result in lasting control of this life-threatening disease.

Therapy of autoimmune mouth bullous disease: 2020 review

Most diseases of oral mucosa are either autoimmune in nature or are the results of immunologically mediated events. The diseases with autoimmune pathogenesis are namely pemphigus and pemphigoid; the oral involvement is frequent or regularly observed in these diseases. The treatments with traditional drugs or biologic agents or combinations of these molecules are employed in clinical practice. New therapeutic targets aim to provide new treatment strategies that may go beyond nonspecific immunosuppression.

B-cell targeted therapies in pemphigus

Pemphigus is a rare autoimmune disease of the skin, characterized by autoantibodies targeting adhesion proteins of the epidermis, in particular desmoglein 3 and desmoglein 1, that cause the loss of cell-cell adhesion and the formation of intraepidermal blisters. Given that these autoantibodies are both necessary and sufficient for pemphigus to occur, the goal of pemphigus therapy is the elimination of autoreactive B-cells responsible for autoantibody production. Rituximab, an anti-CD20 monoclonal antibody, was the first targeted B-cell therapy approved for use in pemphigus and is now considered the frontline therapy for new onset disease. One limitation of this treatment is that it targets both autoreactive and non -autoreactive B-cells, which accounts for the increased risk of serious infections in treated patients. In addition, most rituximab-treated patients experience disease relapse, highlighting the need of new therapeutic options. This review provides a concise overview of rituximab use in pemphigus and discusses new B-cell and antibody-directed therapies undergoing investigation in clinical studies.

Pemphigus vulgaris - approach and management

The place of pemphigus vulgaris (PV) among autoimmune bullous dermatoses is well known. In pemphigus, IgG autoantibodies are directed against desmogleins 1 and 3, which are part of the cadherin family of cell-cell adhesion molecules. These structures are responsible for maintaining the intercellular adherence in stratified squamous epithelia, such as the skin and oral mucosa. The incidence of autoimmune bullous dermatoses is steadily increasing, being associated with a high degree of morbidity. The pathophysiology of these dermatoses is very well understood, complemented by recent genetic studies. The gold standard for the diagnosis of pemphigus vulgaris is the detection of autoantibodies or complement component 3 by direct immunofluorescence microscopy of a perilesional biopsy. Early diagnosis and initiation of treatment are necessary in order to achieve a favorable prognosis. Although the first line of treatment is corticotherapy, there are no clear guidelines on dosing regimens, and long-term adverse effects are important. Corticosteroid-sparing adjuvant therapies have been employed in the treatment of PV, aiming to reduce the necessary cumulative dose of corticosteroids. In addition, therapies with anti-CD20 antibodies are used, but antigen-specific immune suppression-based treatments represent the future.

Updates on diagnosis and management of autoimmune blistering diseases

Over the last several decades, advances in the understanding of the pathogenesis of autoimmune blistering diseases has resulted in significant improvements in diagnosis and management. These improvements include new diagnostic assays and therapies targeted at specific disease mediators. Furthermore, the abundance of new therapies in clinic trials for autoimmune blistering diseases will translate to an enhanced therapeutic armamentarium for clinicians. The aim of this article is to review new developments in the understanding of autoimmune blistering diseases and to summarize advancements in their diagnosis and management.

The pathogenesis of bullous skin diseases

Bullous skin diseases are a group of dermatoses characterized by blisters and bullae in the skin and mucous membranes. The etiology and pathogenesis of bullous skin diseases are not completely clear. The most common are pemphigus and bullous pemphigoid (BP). Autoantibodies play critical roles in their pathogenesis. Abnormalities in the adhesion between keratinocytes in patients with pemphigus leads to acantholysis and formation of intra-epidermal blisters. Anti-desmoglein autoantibodies are present both in the circulation and skin lesions of patients with pemphigus. The deficient adhesion of keratinocytes to the basement membrane in BP patients gives rise to subepidermal blisters. Autoantibodies against the components of hemidesmosome can be detected in BP patients. Many novel therapeutics based on knowledge of the pathogenesis have emerged in recent years.

From bench to bedside: evolving therapeutic targets in autoimmune blistering disease

Autoimmune blistering diseases comprise a group of heterogenous conditions characterized by the loss of tolerance and subsequent development of autoantibodies targeting epidermal and subepidermal adhesion proteins. Blisters and erosions form on the skin and mucous membranes leading to significant morbidity and mortality. Traditional therapies rely on systemic immunosuppression. Advancements in our understanding of the pathophysiology of pemphigus and pemphigoid have led to the development of molecules which target specific pathways involved in induction and perpetuation of disease. In this review, we outline the novel therapeutic strategies including B-cell depletion, T-regulatory cell repletion, cell signalling inhibitors and small molecular inhibitors, inhibitory monoclonal antibodies, as well as complement inhibition. We additionally review their current level of clinical evidence. We lastly review therapeutics targets gleaned from the experimental epidermolysis bullosa acquisita mouse model. These emerging treatments offer an exciting progression from basic science discoveries that have the potential to transform the treatment paradigm in autoimmune blistering diseases.

Pemphigus: Current and Future Therapeutic Strategies

Pemphigus encompasses a heterogeneous group of autoimmune blistering diseases, which affect both mucous membranes and the skin. The disease usually runs a chronic-relapsing course, with a potentially devastating impact on the patients' quality of life. Pemphigus pathogenesis is related to IgG autoantibodies targeting various adhesion molecules in the epidermis, including desmoglein (Dsg) 1 and 3, major components of desmosomes. The pathogenic relevance of such autoantibodies has been largely demonstrated experimentally. IgG autoantibody binding to Dsg results in loss of epidermal keratinocyte adhesion, a phenomenon referred to as acantholysis. This in turn causes intra-epidermal blistering and the clinical appearance of flaccid blisters and erosions at involved sites. Since the advent of glucocorticoids, the overall prognosis of pemphigus has largely improved. However, mortality persists elevated, since long-term use of high dose corticosteroids and adjuvant steroid-sparing immunosuppressants portend a high risk of serious adverse events, especially infections. Recently, rituximab, a chimeric anti CD20 monoclonal antibody which induces B-cell depletion, has been shown to improve patients' survival, as early rituximab use results in higher disease remission rates, long term clinical response and faster prednisone tapering compared to conventional immunosuppressive therapies, leading to its approval as a first line therapy in pemphigus. Other anti B-cell therapies targeting B-cell receptor or downstream molecules are currently tried in clinical studies. More intriguingly, a preliminary study in a preclinical mouse model of pemphigus has shown promise regarding future therapeutic application of Chimeric Autoantibody Receptor T-cells engineered using Dsg domains to selectively target autoreactive B-cells. Conversely, previous studies from our group have demonstrated that B-cell depletion in pemphigus resulted in secondary impairment of T-cell function; this may account for the observed long-term remission following B-cell recovery in rituximab treated patients. Likewise, our data support the critical role of Dsg-specific T-cell clones in orchestrating the inflammatory response and B-cell activation in pemphigus. Monitoring autoreactive T-cells in patients may indeed provide further information on the role of these cells, and would be the starting point for designating therapies aimed at restoring the lost immune tolerance against Dsg. The present review focuses on current advances, unmet challenges and future perspectives of pemphigus management.

Pharmacological advances in pemphigus

This is an updated review of the literature on the emerging therapeutic options for the treatment of pemphigus to provide better care for patients. There is an increasing range of molecules targeted for pemphigus therapy against CD20, Bruton tyrosine kinase, chimeric antigen receptor, T-cell immune components, B-cell activating factor, proliferation-inducing ligand (APRIL), CD25, p38 mitogen-activated protein kinase (p38MAPK) and cytokine modulation therapies (anti-IL-4, anti-IL-6). The main aim of the current new therapies is to provide specific pathology-focused therapeutic options which have long-term sustainable therapeutic effects on disease progress, cause less side effects without systemic immunosuppression, and have less risk of getting antibodies against the medication during treatment.

[Therapy of pemphigus]

BACKGROUND

Pemphigus diseases are a heterogeneous group of potentially life-threatening autoimmune bullous disorders. Therefore, rapidly acting and effective therapeutic approaches are essential.

OBJECTIVES

In this review, current therapeutic options in line with available guidelines are presented and new therapeutic approaches are discussed.

METHODS

A literature search was performed using PubMed.

RESULTS

Treatment of pemphigus is based on systemic glucocorticosteroids, frequently combined with potentially corticosteroid-sparing immunosuppressants such as azathioprine and mycophenolate mofetil/mycophenolic acid. Recently, the impressive efficacy of the anti-CD20 antibody rituximab has been shown in a prospective randomized trial. In severe or treatment-refractory cases, immunoadsorption or high-dose intravenous immunoglobulins (IVIG) are recommended. Adjuvant immunoadsorption also seems to be useful within the first 8-12 weeks of therapy in patients with very high autoantibody levels. A variety of new therapeutic approaches is currently evaluated in phase IIa studies.

CONCLUSION

Therapy of pemphigus has been greatly improved by the employment of rituximab. The use of glucocorticosteroids, associated with a high number of adverse events and elevated mortality, could be reduced by the additional use of rituximab. After approval of rituximab for the treatment of pemphigus by the US Food and Drug Administration in 2018, licensing in Europe is expected in 2019.

Next-generation anti-CD20 monoclonal antibodies in autoimmune disease treatment

The clinical success of anti-CD20 monoclonal antibody (mAb)-mediated B cell depletion therapy has contributed to the understanding of B cells as major players in several autoimmune diseases. The first therapeutic anti-CD20 mAb, rituximab, is a murine-human chimera to which many patients develop antibodies and/or experience infusion-related reactions. A second generation of anti-CD20 mAbs has been designed to be more effective, better tolerated, and of lower immunogenicity. These include the humanized versions: ocrelizumab, obinutuzumab, and veltuzumab, and the fully human, ofatumumab. We conducted a literature search of relevant randomized clinical trials in the PubMed database and ongoing trials in Clinicaltrials.gov. Most of these trials have evaluated intravenous ocrelizumab or subcutaneous ofatumumab in rheumatoid arthritis, multiple sclerosis, or systemic lupus erythematosus. Understanding how newer anti-CD20 mAbs compare with rituximab in terms of efficacy, safety, convenience, and cost is important for guiding future management of anti-CD20 mAb therapy in autoimmune diseases.

Shifting Focus in the Therapeutics of Immunobullous Disease

Therapeutics of autoimmune bullous disease has seen a major shift of focus from more global immunosuppression to targeted immunotherapy. Anti CD 20 monoclonal antibody Rituximab revolutionized the therapeutics of autoimmune bullous disease particularly pemphigus. Though it is still being practiced off-label, evidences in the form of RCT and meta analysis are now available. Other novel anti CD 20 monoclonal antibodies like ofatumumab, veltuzumab, and ocrelizumab, tositumomab or obinutuzumab/GA101 may add to the therapeutic options in coming days. Beyond anti CD 20 monoclonal antibodies other options that show promise at least in select scenario are omalizumab, TNF inhibitors plasmapheresis and intravenous immunoglobulin. The present article will discuss the role of rituximab and other newer therapeutics in the treatment of autoimmune blistering disease, especially pemphigus and suggests their positions in the therapeutic ladder.

Pemphigus

Pemphigus is a group of IgG-mediated autoimmune diseases of stratified squamous epithelia, such as the skin and oral mucosa, in which acantholysis (the loss of cell adhesion) causes blisters and erosions. Pemphigus has three major subtypes: pemphigus vulgaris, pemphigus foliaceus and paraneoplastic pemphigus. IgG autoantibodies are characteristically raised against desmoglein 1 and desmoglein 3, which are cell-cell adhesion molecules found in desmosomes. The sites of blister formation can be physiologically explained by the anti-desmoglein autoantibody profile and tissue-specific expression pattern of desmoglein isoforms. The pathophysiological roles of T cells and B cells have been characterized in mouse models of pemphigus and patients, revealing insights into the mechanisms of autoimmunity. Diagnosis is based on clinical manifestations and confirmed with histological and immunochemical testing. The current first-line treatment is systemic corticosteroids and adjuvant therapies, including immunosuppressive agents, intravenous immunoglobulin and plasmapheresis. Rituximab, a monoclonal antibody against CD20⁺ B cells, is a promising therapeutic option that may soon become first-line therapy. Pemphigus is one of the best-characterized human autoimmune diseases and provides an ideal paradigm for both basic and clinical research, especially towards the development of antigen-specific immune suppression treatments for autoimmune diseases.

Targeting B cells in treatment of autoimmunity

B cells have emerged as effective targets for therapeutic intervention in autoimmunities in which the ultimate effectors are antibodies, as well as those in which T cells are primary drivers of inflammation. Proof of this principle has come primarily from studies of the efficacy of Rituximab, an anti-CD20 mAb that depletes B cells, in various autoimmune settings. These successes have inspired efforts to develop more effective anti-CD20s tailored for specific needs, as well as biologicals and small molecules that suppress B cell function without the risks inherent in B cell depletion. Here we review the current status of B cell-targeted therapies for autoimmunity.

Comparison of two dosing schedules for subcutaneous injections of low-dose anti-CD20 veltuzumab in relapsed immune thrombocytopenia

We compared two dosing schedules for subcutaneous injections of a low-dose humanized anti-CD20 antibody, veltuzumab, in immune thrombocytopenia. Fifty adults with primary immune thrombocytopenia, in whom one or more lines of standard therapy had failed and who had a platelet count <30×10⁹/L but no major bleeding, initially received escalating 80, 160, or 320 mg doses of subcutaneous veltuzumab administered twice, 2 weeks apart; the last group received once-weekly doses of 320 mg for 4 weeks. In all dose groups, injection reactions were transient and mild to moderate; there were no other safety issues. Forty-seven response-evaluable patients had 23 (49%) objective responses (platelet counts ≥30×10⁹/L and ≥2 × baseline) including 15 (32%) complete responses (platelets ≥100×10⁹/L). Responses (including complete responses) and bleeding reduction occurred in all dose groups and were not dose-dependent. In contrast, response duration increased progressively with total dose, reaching a median of 2.7 years with the four once-weekly 320-mg doses. Among nine responders retreated at relapse, three at higher dose levels responded again, including one patient who was retreated four times. In all dose groups, B-cell depletion occurred after the first dose until recovery starting 12 to 16 weeks after treatment. Veltuzumab serum levels increased with dose group according to total dose administered, but terminal half-life and clearance were comparable. Human anti-veltuzumab antibody titers developed without apparent dose dependence in nine patients, of whom six responded including five who had complete responses. Subcutaneous veltuzumab was convenient, well-tolerated, and active, without causing significant safety concerns. Platelet responses and bleeding reduction occurred in all dose groups, and response durability appeared to improve with higher doses. Clinicaltrials.gov identifier: NCT00547066.

[Pemphigus. Model disease for targeted therapy]

BACKGROUND

Pemphigus is a severe bullous autoimmune dermatosis that represents a clinical challenge despite high-dose immunosuppressive therapy due to the therapy-related comorbidities and the lack of long-term control of disease activity.

OBJECTIVES

Which targeted therapies are currently used in pemphigus and which innovative therapeutic strategies are in clinical development?

MATERIALS AND METHODS

A review of the literature in PubMed was performed under consideration of the current guideline for the treatment of pemphigus as well as of our own results. Discussion of basic findings and results of targeted therapies in autoantibody-mediated autoimmune disorders were taken into account.

RESULTS

Immunapheresis and high-dose intravenous immunoglobulins with the aim of reducing circulating autoantibodies have been successfully used in the treatment of pemphigus. Depletion of autoreactive B-lymphocytes provides the rationale for the use of the monoclonal anti-CD20 antibody rituximab which demonstrated long-term clinical remission of pemphigus in clinical trials. Current developments include the investigation of humanised B-cell depleting antibodies in other B-cell driven autoimmune disorders as well as the identification of new cellular and molecular target structures that are essential in the humoral autoimmune cascade and exert important immune regulatory functions, respectively.

CONCLUSIONS

The well-characterised basic pathogenesis of pemphigus results in targeted therapies. Currently, therapies aiming at rapid reduction of circulating autoantibodies and the depletion of autoreactive B-cells are in clinical use. More cellular and molecular target structures are being investigated in other autoantibody-driven autoimmune disorders and they provide promising candidates for innovative pathogenesis-related therapeutic strategies in pemphigus in the future.

Future therapies for pemphigus vulgaris: Rituximab and beyond

The conventional treatment for patients with pemphigus vulgaris (PV) centers on global immunosuppression, such as the use of steroids and other immunosuppressive drugs, to decrease titers of antidesmoglein autoantibodies responsible for the acantholytic blisters. Global immunosuppressants, however, cause serious side effects. The emergence of anti-CD20 biologic medications, such as rituximab, as an adjunct to conventional therapy has shifted the focus to targeted destruction of autoimmune B cells. Next-generation biologic medications with improved modes of delivery, pharmacology, and side effect profiles are constantly being developed, adding to the diversity of options for PV treatment. We review promising monoclonal antibodies, including veltuzumab, obinutuzumab (GA-101), ofatumumab, ocaratuzumab (AME-133v), PRO131921, and belimumab.

The emerging role of rituximab in autoimmune blistering diseases

Rituximab is a chimeric monoclonal antibody that selectively binds to the CD20 molecule on B cells, resulting in their lysis. In autoimmune blistering diseases, the auto-antibody-producing B cells are destroyed and auto-antibody levels are reduced or eliminated. In the majority of patients, rituximab produces rapid clinical response and early resolution. In part, this accounts for the increased use of rituximab. Rituximab does not distinguish normal from pathologic B cells. Hence, shortly after its use, B-cell levels are zero and remain so for several months. In most patients, the use of systemic corticosteroids and immunosuppressive agents are continued after rituximab therapy, while their dosages are significantly decreased. In the majority of patients rituximab is used according to the protocol used in treating lymphoma patients or patients with rheumatoid arthritis. Approximately 50% of patients experience a relapse, requiring additional therapy. Serious adverse events and fatal outcomes have been reported, although their incidence is less than that observed with conventional therapy. Nonetheless, the causes, i.e. infections and septicemia, are similar. Several gaps exist in our understanding of how to optimally benefit from the use of this valuable biological agent. Future studies need to be targeted in designing and implanting protocols that maximize the benefit of rituximab and result in producing sustained prolonged remissions with minimal adverse events and a high quality of life.

The combination of milatuzumab, a humanized anti-CD74 antibody, and veltuzumab, a humanized anti-CD20 antibody, demonstrates activity in patients with relapsed and refractory B-cell non-Hodgkin lymphoma

As a result of the anti-tumour activity observed in vitro and in vivo with combined anti-CD20 and anti-CD74 antibodies, we initiated a phase I/II trial of veltuzumab and milatuzumab in patients with relapsed or refractory B-cell non-Hodgkin lymphoma (NHL). Patients received an induction of veltuzumab 200 mg/m(2) weekly combined with escalating doses of milatuzumab at 8, 16 and 20 mg/kg weekly for 4 weeks. Patients without disease progression could receive an extended induction with treatment on weeks 12, 20, 28 and 36. A total of 35 patients enrolled on the study. Median age was 63 years, median number of prior therapies was 3, and 63% of patients were rituximab refractory. No dose-limiting toxicities were observed in the phase I study. Related grade 3-4 toxicities included lymphopenia, leucopenia, neutropenia, anaemia, infusion reactions, hyperglycaemia, fatigue and atrial tachycardia. Median weeks of therapy was 12 and 29% of patients completed all 36 weeks of therapy. The overall response rate was 24%, median duration of response was 12 months, and responses were observed at all dose levels and in 50% of patients refractory to rituximab. Combination therapy with veltuzumab and milatuzumab demonstrated activity in a population of heavily pre-treated patients with relapsed or refractory indolent NHL.