B-Cell Targeted Therapies in Systemic Lupus Erythematosus

Systemic lupus erythematosus is a multisystem autoimmune disease characterized by the formation of autoantibodies that target a variety of self antigens. B cells are fundamental to the development of these antibodies and are a target for intervention in the disease. This review discusses four therapies that target B cells by inducing B-cell depletion, reduction in B-cell proliferation and differentiation, or modulation of B-cell function. Rituximab is an anti-CD20 chimeric monoclonal antibody that depletes B cells but not plasma cells. Systematic reviews of open label studies, particularly in lupus patients refractory to conventional therapy, have suggested that rituximab can be an effective treatment for non-renal lupus and lupus nephritis. However, randomized, double-blind, controlled trials comparing rituximab with placebo in addition to standard of care therapy for non-renal lupus and lupus nephritis over 12 months failed to demonstrate efficacy using the planned primary endpoints, although there were some post-hoc analyses suggesting that rituximab may have beneficial effects that would be worthy of further study as no significant toxicity has been demonstrated. Treatment with belimumab, a humanized monoclonal antibody targeted against B lymphocyte stimulator (BLys), was more efficacious than placebo and had no significant increase in adverse events in two non-renal, phase III lupus trials when given in addition to standard of care therapy for 52 weeks. Belimumab is licensed for the management of lupus in the US and in Europe. Atacicept is a humanized fusion protein that binds BLys and APRIL (a proliferation-inducing ligand) that might be more effective than belimumab in the management of lupus. Unfortunately a phase II/III trial of atacicept in lupus nephritis had to be stopped due to the development of low immunoglobulin levels and pneumonias in some patients. However, in retrospect these complications may have been due to concomitant treatment with mycophenolate mofetil and results of a 52-week, non-renal, phase III trial with atacicept are awaited. Epratuzumab is a humanized monoclonal antibody that targets CD22 on B cells and results in modulation of B-cell function and migration, as CD22 regulates adhesion and inhibits B-cell receptor (BCR) signalling. Epratuzumab at a cumulative dose of 2,400 mg over 4 weeks has been shown to improve lupus disease activity compared with placebo 12 weeks after initiation of therapy in a phase II study, and a 12-month phase III study is on-going. B-cell targeted therapies are an attractive prospect for treating lupus disease and the results of current phase III trials are eagerly awaited. Finding the most appropriate trial design to demonstrate efficacy in lupus trials has been a challenge. The SRI (SLE response index) used in the belimumab studies and the BICLA (British Isles Lupus Assessment Group-based Composite Lupus Assessment) used in the epratuzumab studies are currently the promising trial designs for non-renal studies. For lupus nephritis it is important that trials are of adequate duration to be able to demonstrate benefit of new therapies over conventional therapy.     

Belimumab for the treatment of systemic lupus erythematosus

Given their pivotal role in autoantibody production, B-cells have become an attractive therapeutic target in systemic lupus erythematosus (SLE). Belimumab, a fully human monoclonal antibody against B lymphocyte stimulator (BLyS), a B-cell survival factor, was licensed in 2011 for the treatment of autoantibody-positive SLE. The BLISS-52 and BLISS-76 Phase III trials successfully demonstrated that belimumab (10 mg/kg) with standard therapy significantly decreased disease activity in SLE patients compared to placebo with standard therapy. Overall, belimumab has been found to be safe and well tolerated. While the BLISS-52 and BLISS-76 studies are the largest clinical trials in SLE to date, they mainly focused on musculoskeletal, mucocutaneous, hematologic and general constitutional features of the disease. Patients with severe lupus nephritis and severe central nervous system disease were excluded from these trials. Studies of belimumab in lupus nephritis are ongoing that may clarify the role of this agent in the clinical management of SLE.     

Rituximab: Beyond Simple B Cell Depletion

Rituximab, a chimeric anti-CD20 monoclonal antibody, has a proven track record for over a decade in the treatment of lymphomas, where it has been used to eradicate malignant lymphocytes. In appreciation of the putative role of B cells, especially with respect to autoantibody production, in the pathogenesis of autoimmune diseases, successful trials of B-cell depletion therapy in RA, SLE, and other autoimmune diseases have been carried out. In these trials, clinical benefit has generally correlated with the extent and duration of B-cell depletion, but at times imperfectly, and autoantibody reduction only selectively. Additional mechanisms whereby rituximab may assert its clinical benefit in autoimmune diseases have been examined including a look at B-cell functions as T-cell modulator and antigen-presenting cell, T-regulatory cell behavior, NK cell activity, and macrophage activities in immune inflammation. The available data on rituximab’s action in autoimmune diseases is reviewed.     

B-cell-targeted therapies in systemic lupus erythematosus

Autoreactive B cells are one of the key immune cells that have been implicated in the pathogenesis of systemic lupus erythematosus (SLE). In addition to the production of harmful auto-antibodies (auto-Abs), B cells prime autoreactive T cells as antigen-presenting cells and secrete a wide range of pro-inflammatory cytokines that have both autocrine and paracrine effects. Agents that modulate B cells may therefore be of potential therapeutic value. Current strategies include targeting B-cell surface antigens, cytokines that promote B-cell growth and functions, and B- and T-cell interactions. In this article, we review the role of B cells in SLE in animal and human studies, and we examine previous reports that support B-cell modulation as a promising strategy for the treatment of this condition. In addition, we present an update on the clinical trials that have evaluated the therapeutic efficacy and safety of agents that antagonize CD20, CD22 and B-lymphocyte stimulator (BLyS) in human SLE. While the results of many of these studies remain inconclusive, belimumab, a human monoclonal antibody against BLyS, has shown promise and has recently been approved by the US Food and Drug Administration as an indicated therapy for patients with mild to moderate SLE. Undoubtedly, advances in B-cell immunology will continue to lead us to a better understanding of SLE pathogenesis and the development of novel specific therapies that target B cells.     

Emerging biological drugs: a new therapeutic approach for Systemic Lupus Erythematosus. An update upon efficacy and adverse events

B-cells abnormalities leading to autoantibody production play a central role in Systemic Lupus Erythematosus (SLE) pathogenesis. B-cell targeted therapies, including anti-B lymphocyte stimulator (BLyS) and anti-CD20 monoclonal antibodies, are at forefront of new SLE treatments. Biologic agents targeting specific pathways (i.e. T-B lymphocyte interaction, cytokines and complement) have been also proposed as new tools for SLE treatment. In this review we will focus on biological drugs whose potential efficacy has been evaluated in open-label and randomized clinical trials.     

Belimumab Therapy in Systemic Lupus Erythematosus

Systemic lupus erythematosus (SLE) is a complex heterogeneous disease, posing challenges to clinical trials. As in other autoimmune diseases, B-lymphocytes play a central role in lupus pathogenesis. The finding that selection and survival of B cells are controlled by a variety of signals, including those provided by the longevity factor BAFF (B-cell activating factor), also called BLyS (B-lymphocyte stimulator), led to preclinical trials that revealed that BAFF represents a promising therapeutic target for human lupus. Belimumab is a fully human monoclonal antibody directed against BAFF. Lessons learned from early clinical trials led to improved methods and success of phase III trials, with recruitment of patients with both clinically and serologically active disease, development and use of a novel SLE Responder Index, and progressive and special restrictions on immunosuppressive and corticosteroid use. These studies offer an attractive blueprint to conduct future clinical trials in SLE. The overall steroid-sparing ability and benefits of belimumab on musculoskeletal and mucocutaneous organ systems suggest that it has an impact on the clinical management of SLE patients. Future directions include studies to determine the role of belimumab in early SLE, as well as in renal or CNS involvement.     

Belimumab: A Guide to Its Use in Systemic Lupus Erythematosus

Belimumab (Benlysta?), a fully human recombinant IgG1λ monoclonal antibody that inhibits the binding of soluble B lymphocyte stimulator to B cells, is indicated for the treatment of adult patients with active, autoantibody-positive systemic lupus erythematosus (SLE) with a high degree of disease activity despite receiving standard therapy. In multinational trials, significantly more belimumab recipients than placebo recipients achieved an SLE Responder Index response at 52 weeks.     

Subcutaneous and intravenous belimumab in the treatment of systemic lupus erythematosus: a review of data on subcutaneous and intravenous administration

Introduction: Loss of B cell tolerance is a hallmark feature of the pathogenesis of Systemic Lupus Erythematosus (SLE). Recent advances in B cell therapy have focused on targeted therapy aimed at inhibiting B cell activation and reducing B cell survival. Belimumab, a human monoclonal antibody against B cell activating factor (BAFF) was licensed in 2011 for the treatment of SLE.

Areas covered: We review the data on the intravenous and subcutaneous formulations of belimumab in the management of patients with SLE. BLISS-52 and BLISS-76 demonstrated the efficacy of intravenous belimumab (10mg/kg) as an add-on therapy in SLE patients with active disease. A recent phase III trial of intravenous belimumab reported similar results in North East Asian patients. Subcutaneous belimumab (200mg/weekly) has demonstrated similar efficacy, safety and tolerability and was approved by the FDA in 2017 for the treatment of active autoantibody positive SLE patients receiving standard therapy.

Expert commentary: Belimumab is generally safe and well tolerated. The most common clinical manifestations of SLE in the clinical trials were arthritis, mucocutaneous disease and serositis. Patients with severe lupus nephritis and central nervous system disease were excluded from these clinical trials.     

Anti-interleukin-6 monoclonal antibody inhibits autoimmune responses in a murine model of systemic lupus erythematosus

Systemic lupus erythematosus (SLE) is an autoimmune disease resulting from dysregulation of the immune system. Interleukin-6 (IL-6) is a multifunctional cytokine produced by macrophages, monocytes and T and B cells. It stimulates B-cell differentiation/maturation, immunoglobulin secretion, and T-cell functions. Elevated levels of IL-6 in serum, urine and renal glomeruli were detected in patients with active SLE and in murine models of SLE. Our study investigated the role of IL-6 in an SLE-like disease in New Zealand Black/White (NZB/W) F1 mice by administration of an anti-murine IL-6 monoclonal antibody (mAb). Intraperitoneal administration of the anti-IL-6 mAb suppressed the production of anti-dsDNA autoantibody. B-cell proliferation induced by anti-IgM and anti-CD40 was lower in the anti-IL-6 mAb-treated mice, ex vivo studies demonstrated that anti-IL-6 mAb treatment inhibited anti-dsDNA production. Anti-CD3-induced T-cell proliferation and mixed lymphocyte reactions were inhibited by anti-IL-6 mAb treatment, indicating a partial down-regulation of T cells. Histological analysis showed that treatment with anti-IL-6 mAb prevented the development of severe kidney disease. These results suggest that treatment with anti-IL-6 mAb has a beneficial effect on autoimmunity in murine SLE and that autoreactive B cells may be the primary target for anti-IL-6 mAb treatment; its effect on autoreactive T cells is also indicated.     

A double-edged sword in B-cell-targeted therapy for inflammatory diseases

Cells of the immune system, including B cells, perform inflammatory functions against microbial invasion, accompanied by anti-inflammatory responses to avoid host damage. B-cell-depletion therapy using anti-CD20 monoclonal antibodies against inflammatory diseases has beneficial or adverse effects depending on the timing and/or microenvironment in which they are used. To achieve effective B-cell-targeted therapy, it is necessary to identify and understand the modes of action of pathogenic and regulatory B cells, which include antibody production, formation of immune complexes, cytokine and chemokine production, cytotoxic killing, lymphoid neogenesis and antigen presentation. B cells interact with multiple cells, including dendritic cells, T cells and natural killer T cells, creating a complex regulatory network. Specific targeting of B-cell subsets and/or their interaction partners might lead to clinical benefits with minimal host damage.     

B cells in SLE: different biological drugs for different pathogenic mechanisms

Systemic Lupus Erythematosus (SLE) is a chronic autoimmune disease characterized by a complex multi-factorial pathogenesis and a great clinical polymorphism. SLE is considered to be a B cell disease in which autoantibodies are the major players. Recently, the central role of B cells has been confirmed and it has been shown that that the relative frequency of B cells subsets is altered in SLE patients. Conventional immunosuppressive therapies such as azathioprine, cyclophosphamide or methotrexate, reduce disease activity and improves the patient's general health conditions. These treatments have possible side effects; in fact they could compromise liver function, fertility and innate and adaptive immune responses. Moreover, for unknown reasons a small group of SLE patients is refractory to immunosuppressive therapy. In these cases finding an effective treatment becomes a challenge. The progress in therapeutic antibody technology has led to the production of a wide array of humanized monoclonal antibodies, targeting specific cell types or pathways, initiating a new era in the treatment of autoimmune disorders. In contrast to general immuno-suppression, the availability of drugs interfering with specific pathogenetic pathways gives the possibility to choose therapies tailored to each disease in each patient.     

The therapeutic potential of anti-CD20 "what do B-cells do?"

B-cells play a major role in the immunopathogenesis of autoimmune diseases. Not only do they produce autoantibodies, but they regulate other cell types, secrete cytokines, and present antigens. They are thus potential targets for therapeutic intervention. CD20 is a B-cell specific cell surface molecule of uncertain function. An anti-CD20 chimeric mAb (rituximab) has been FDA approved for treatment of B-cell lymphomas since 1997. Rituximab also depletes normal B-cells by several mechanisms, including ADCC. Over the past seven years, it has shown promise in a number of autoimmune diseases in phase I trials and anecdotal reports. Efficacy in rheumatoid arthritis has already been demonstrated in randomized control trials (RCTs), and RCTs in SLE, inflammatory myositis, and ANCA associated vasculitis are under way. Safety does not appear to be a major problem, but continued vigilance is warranted. The increased use of rituximab, other anti-CD20 agents, and other B-cell targeting therapies holds great promise for substantial clinical benefits, as well as providing special opportunities to understand better disease pathogenesis.     

Unmet Needs in the Pathogenesis and Treatment of Systemic Lupus Erythematosus

Systemic lupus erythematosus (SLE) is an autoimmune rheumatic disease with a prevalence of approximately 1 in 1000. Over the last 30 years, advances in treatment such as use of corticosteroids and immunosuppressants have improved life expectancy and quality of life for patients with lupus and the key unmet needs have therefore changed. With the reduced mortality from disease activity, development of cardiovascular disease (CVD) has become an increasingly important cause of death in patients with SLE. The increased CVD risk in these patients is partly, but not fully explained by standard risk factors, and abnormalities in the immune response to lipids may play a role. Invariant natural killer T cells, which are triggered specifically by lipid antigens, may protect against progression of subclinical atherosclerosis. However, currently our recommendation is that clinicians should focus on optimal management of standard CVD risk factors such as smoking, blood pressure and lipid levels. Fatigue is one of the most common and most limiting symptoms suffered by patients with SLE. The cause of fatigue is multifactorial and disease activity does not explain this symptom. Consequently, therapies directed towards reducing inflammation and disease activity do not reliably reduce fatigue and new approaches are needed. Currently, we recommend asking about sleep pattern, optimising pain relief and excluding other causes of fatigue such as anaemia and metabolic disturbances. For the subgroup of patients whose disease activity is not fully controlled by standard treatment regimes, a range of different biologic agents have been proposed and subjected to clinical trials. Many of these trials have given disappointing results, though belimumab, which targets B lymphocytes, did meet its primary endpoint. New biologics targeting B cells, T cells or cytokines (especially interferon) are still going through trials raising the hope that novel therapies for patients with refractory SLE may be available soon.     

Costimulation Blockade in the Treatment of Rheumatic Diseases

The autoimmune response is executed via cognate interactions between effector immune cells and antigen presenting cells. Cognate interactions provide the immune effectors with specific signals generated through the antigen receptor as well as with second, non-specific signals, generated from the interaction of pairs of cell-surface molecules (costimulatory molecules) present on their plasma membrane. Disruption of this second, non-specific costimulatory signal results in the interruption of the productive (auto)immune response, leading to anergy, a state of immune unresponsiveness. The CD28:B7 families of molecules and the CD40:CD40L pair of molecules are considered as critical costimulatory elements. Disruption of the CD28:B7 interaction using a genetically engineered soluble form of the inhibitory molecule CTLA4 in vitro, as well as in experimental models of rheumatoid arthritis (RA) and systemic lupus erythematosus (SLE), led to the inhibition of the autoimmune response. Similarly, promising data stem from the use of an anti-CD40L monoclonal antibody (mAb) in murine SLE. While such treatments prevent the development of autoimmunity in animal models, this preventive approach is inapplicable to human diseases. However, the rational bench-to-bedside approach led investigators to clinical trials of CTLA4-Ig and of two different humanized anti-human CD40L mAbs in patients with RA and SLE, respectively. Initial experience with the use of CTLA4-Ig in patients with RA is encouraging, since in one short-term trial the construct was well-tolerated and produced clinically meaningful improvement of the disease in a significant proportion of those treated. Surprisingly, the anti-CD40L mAb treatment approach in human lupus was not fruitful, since short-term administration of the anti-CD40L mAb ruplizumab in lupus nephritis was correlated with life-threatening prothrombotic activity despite initial encouraging data in the serology and renal function of the patients. Also, IDEC-131 anti-CD40L mAb treatment did not prove to be clinically effective in human SLE, despite being well tolerated. Precise tailoring of the administration schemes for these novel therapeutic modalities is awaited.Finally, conceptually different approaches to block costimulation by inhibiting the induced expression of costimulatory molecules or the transmission of their specific intracytoplasmic signal have already produced encouraging preliminary results.     

B-lymphocyte depletion reduces skin fibrosis and autoimmunity in the tight-skin mouse model for systemic sclerosis

Systemic sclerosis (scleroderma) is an autoimmune disease characterized by excessive extracellular matrix deposition in the skin. A direct role for B lymphocytes in disease development or progression has remained controversial, although autoantibody production is a feature of this disease. To address this issue, skin sclerosis and autoimmunity were assessed in tight-skin mice, a genetic model of human systemic sclerosis, after circulating and tissue B-cell depletion using an anti-mouse CD20 monoclonal antibody before (day 3 after birth) and after disease development (day 56). CD20 monoclonal antibody treatment (10 to 20 microg) depleted the majority (85 to 99%) of circulating and tissue B cells in newborn and adult tight-skin mice by days 56 and 112, respectively. B-cell depletion in newborn tight-skin mice significantly suppressed (approximately 43%) the development of skin fibrosis, autoantibody production, and hypergammaglobulinemia. B-cell depletion also restored a more normal balance between Th1 and Th2 cytokine mRNA expression in the skin. By contrast, B-cell depletion did not affect skin fibrosis, hypergammaglobulinemia, and autoantibody levels in adult mice with established disease. Thereby, B-cell depletion during disease onset suppressed skin fibrosis, indicating that B cells contribute to the initiation of systemic sclerosis pathogenesis in tight-skin mice but are not required for disease maintenance.     

B-Cell Depletion and Repopulation in Autoimmune Diseases

Although T-lymphocytes have long been regarded as the prime effector of autoimmune diseases, numerous studies have since highlighted a key role for B-lymphocytes. For example, disturbances in the distribution of circulating B-cell subsets were reported in primary Sjögren’s syndrome (pSS) and systemic lupus erythematosus (SLE). Consequently, this was the rationale to treat such patients for B-cell depletion with anti-CD20 monoclonal antibody (rituximab). The aim of this review is to describe and analyze the B-cell subset distribution at baseline and after rituximab therapy in patients with SLE, rheumatoid arthritis, and pSS. Finally, we will compare factors that may interfere with anti-CD20-mediated B-cell depletion in these autoimmune diseases.     

B-lymphocyte effector functions in health and disease

B-lymphocytes have traditionally been thought to contribute to immunity and autoimmune disease through terminal differentiation into plasma cells that secrete antibody. However, studies in mice and recent clinical studies have demonstrated that genetically altered B-cell function and B-cell-targeted therapies can significantly affect autoimmune diseases that were predominantly thought to be T-cell-mediated. B-cell depletion in mouse models of disease has also led to the identification of alternative B-cell effector functions that regulate normal immune responses and autoimmune disease. This review highlights multiple B-cell effector mechanisms, including the promotion of cellular immunity, the negative regulation of immune responses, and the production of pathogenic antibodies.     

Similar CD19 Dysregulation in Two Autoantibody-Associated Autoimmune Diseases Suggests a Shared Mechanism of B-Cell Tolerance Loss

: We report here that dysregulation of CD19, a coreceptor that augments B-cell receptor (BCR) signaling, occurs at two B-cell differentiative stages in patients with systemic lupus erythematosus (SLE) and antineutrophil cytoplasmic autoantibody (ANCA) associated small vessel vasculitis (SVV). The na?ve B cells of nearly all SLE and ANCA-SVV patients express approximately 20% less CD19 than healthy control (HC) B cells. In contrast, a subset of memory B cells of some SLE and ANCA-SVV Pts (25-35%) express two to fourfold more CD19 than HC B cells. These CD19(hi) memory B cells are activated and exhibit evidence of antigen selection. Proteome array analysis of 67 autoantigens indicates that CD19(hi) SLE Pts exhibit a distinct autoantibody profile characterized by high levels of antibodies to small nuclear ribonucleoproteins and low levels of antiglomerular autoantibodies. These findings have implications for autoreactive B-cell activation and suggest a shared mechanism of B-cell tolerance loss in these two diseases.     

The efficacy of novel B cell biologics as the future of SLE treatment: A review

Systemic lupus erythematosus (SLE) is a chronic autoimmune inflammatory disease with wide ranging multi-systemic effects. Current understanding centralises B cells in SLE pathogenesis with clinical features resulting from autoantibody formation, immune complex deposition, antigen presentation and cytokine activation. Existing standard of care therapies generates adverse side effects; secondary to corticosteroid use and untargeted immunosuppression. The inability to uphold remission and abolish the disease process, in addition to the increasing numbers of patients seen with refractory disease with these therapies, has provoked the development of novel B cell biologics targeting specific pathogenic pathways fundamental to the SLE disease process.