Initial clinical trial of epratuzumab (humanized anti-CD22 antibody) for immunotherapy of systemic lupus erythematosus

An exploratory dose-escalating study investigating the safety, tolerability, pharmacokinetics and pharmacodynamics of intravenous atacicept in patients with systemic lupus erythematosus

Atacicept, a recombinant fusion protein containing the extracellular, ligand-binding portion of the transmembrane activator and calcium modulator and cyclophilin-ligand interactor receptor, and the Fc portion of human immunoglobulin (Ig) G, is designed to block the activity of B-lymphocyte stimulator and a proliferation-inducing ligand, and may have utility as a treatment for B-cellmediated diseases, such as systemic lupus erythematosus (SLE). This Phase Ib study investigated the safety, tolerability, pharmacokinetics (PK) and pharmacodynamics of intravenous (i.v.) atacicept in patients with mild-to-moderate SLE. Patients (n = 24) were randomised (5:1) to receive atacicept (single dose: 3, 9 or 18 mg/kg; or multiple dose: 2 × 9 mg/kg) or matching placebo. Patients were followed for 6 weeks after dosing (9 weeks in the 2 × 9 mg/kg cohort). Local tolerability of atacicept was comparable with that of placebo, with only mild injection-site reactions reported with atacicept. Atacicept i.v. was generally well tolerated, both systemically and locally, in patients with mild-to-moderate SLE. Atacicept displayed non-linear PK, which was predictable across doses and between single and repeat doses. The biological activity of atacicept was demonstrated by its marked effect in reducing B-cells and Ig levels in patients with SLE. This supports the utility of this therapeutic approach in the treatment of autoimmune diseases, such as SLE.

Current status on B-cell depletion therapy in autoimmune diseases other than rheumatoid arthritis

Since the approval of the chimeric anti-CD20 antibody rituximab for the treatment of adults with severe-to-moderate rheumatoid arthritis after an inadequate response to TNF blockade, B-cell depletion therapy has been used for the treatment of a broad range of refractory autoimmune disorders. Based on current experiences and a literature search, a systematic review and evaluation of the current status of B-cell depletion therapy in autoimmune diseases other than rheumatoid arthritis, including rheumatic, nephrologic, dermatologic and neurologic autoimmune entities, was performed by an international group of experts based at several academic centres. Although important questions remain about the value and place of B-cell depletion in autoimmune diseases other than RA, preliminary data indicate the value of this therapeutic approach in otherwise refractory patients. However, given the lack of robust data from large randomised controlled trials, anti-CD20 therapy should be considered on an individual basis in otherwise refractory patients and its use based on a risk/benefit net calculation.

A perspective on B-cell-targeting therapy for SLE

In recent years, large controlled trials have tested several new agents for systemic lupus erythematosus (SLE). Unfortunately, none of these trials has met its primary outcome. This does not mean progress has not been made. In fact, a great deal has been learned about doing clinical trials in lupus and about the biological and clinical effects of the drugs being tested. Many of these drugs were designed to target B cells directly, e.g., rituximab, belimumab, epratuzumab, and transmembrane activator and calcium modulator and cyclophilin ligand interactor-immunoglobulin (TACI-Ig). The enthusiasm for targeting B cells derives from substantial evidence showing the critical role of B cells in murine models of SLE, as well promising results from multiple open trials with rituximab, a chimeric anti-CD20 monoclonal antibody that specifically depletes B cells (Martin and Chan in Immunity 20(5):517-527, 2004; Sobel et al. in J Exp Med 173:1441-1449, 1991; Silverman and Weisman in Arthritis Rheum 48:1484-1492, 2003; Silverman in Arthritis Rheum 52(4):1342, 2005; Shlomchik et al. in Nat Rev Immunol 1:147-153, 2001; Looney et al. in Arthritis Rheum 50:2580-2589, 2004; Lu et al. in Arthritis Rheum 61(4):482-487, 2009; Saito et al. in Lupus 12(10):798-800, 2003; van Vollenhoven et al. in Scand J Rheumatol 33(6):423-427, 2004; Sfikakis et al. Arthritis Rheum 52(2):501-513, 2005). Why have the controlled trials of B-cell-targeting therapies failed to demonstrate efficacy? Were there flaws in design or execution of these trials? Or, were promising animal studies and open trials misleading, as so often happens? This perspective discusses the current state of B-cell-targeting therapies for human lupus and the future development of these therapies.

Translational Mini-Review Series on B Cell-Directed Therapies: Recent advances in B cell-directed biological therapies for autoimmune disorders

B cell-directed therapies are promising treatments for autoimmune disorders. Besides targeting CD20, newer B cell-directed therapies are in development that target other B cell surface molecules and differentiation factors. An increasing number of B cell-directed therapies are in development for the treatment of autoimmune disorders. Like rituximab, which is approved as a treatment for rheumatoid arthritis (RA), many of these newer agents deplete B cells or target pathways essential for B cell development and function; however, many questions remain about their optimal use in the clinic and about the role of B cells in disease pathogenesis. Other therapies besides rituximab that target CD20 are the furthest along in development. Besides targeting CD20, the newer B cell-directed therapies target CD22, CD19, CD40-CD40L, B cell activating factor belonging to the TNF family (BAFF) and A proliferation-inducing ligand (APRIL). Rituximab is being tested in an ever-increasing number of autoimmune disorders and clinical studies of rituximab combined with other biological therapies are being pursued for the treatment of rheumatoid arthritis (RA). B cell-directed therapies are being tested in clinical trials for a variety of autoimmune disorders including RA, systemic lupus erythematosus (SLE), Sjögren's syndrome, vasculitis, multiple sclerosis (MS), Graves' disease, idiopathic thrombocytopenia (ITP), the inflammatory myopathies (dermatomyositis and polymyositis) and the blistering skin diseases pemphigus and bullous pemphigoid. Despite the plethora of clinical studies related to B cell-directed therapies and wealth of new information from these trials, much still remains to be discovered about the pathophysiological role of B cells in autoimmune disorders.

Lupus nephritis

Lupus nephritis (LN) is one of the common manifestations of systemic lupus erythematosus. Kidney biopsy remains a mainstay of LN diagnosis, which is usually prompted by abnormal urinary sediment, proteinuria, or elevated creatinine. New International Society of Nephrology/Renal Pathology Society classification of LN tends to remove some of the ambiguities of World Health Organization classification and results in better categorization of patients. Although prognosis of LN has improved with the combined use of cytotoxic and steroid therapy, up to 20% of these patients progress to renal failure. Moreover, toxicity of the current regimens remains a major concern. Last few decades have seen a tremendous progress being made in understanding the pathogenesis of LN, but a little has been added to armamentarium against LN, leaving physicians with a few choices. Fortunately, with unfolding of molecular processes involved in disease pathogenesis, new targets for drug therapy have emerged. Whether these medications will prove to be more efficacious and less toxic remains a matter of debate and will be answered by several ongoing trials and future studies.

B-cell-directed therapies for autoimmune disease

Approval of the anti-CD20 antibody rituximab for the treatment of moderate-to-severe rheumatoid arthritis in patients who fail to respond to anti-tumor-necrosis-factor agents has raised interest in B-cell-directed therapy for this disease. A number of direct and indirect modalities with distinct mechanisms of action are being investigated, including anti-CD20 and anti-CD22 therapies, and new approaches for blocking members of the tumor necrosis factor cytokine family including B cell activating factor (BAFF) and a proliferation ligand (APRIL), which are at late stages of clinical development. Clinical experience is most extensive with rituximab, and suggests that targeting 'autoimmune' memory B cells is a feasible approach for treating autoimmune disease. Although anti-CD20 therapy has only been approved for rheumatoid arthritis thus far, data suggest this approach could be valid for other autoimmune diseases, including systemic lupus erythematosus, Sjögren's syndrome, vasculitides, autoimmune cytopenias, and neurologic and dermatologic autoimmune diseases. Additional studies of direct and indirect B-cell-directed treatments are needed before we can draw conclusions as to the value of this approach in patients with various autoimmune diseases and whether more precisely defined techniques than these are required to target the complex humoral system effectively.

[Translational aspects on the role of B-cells in autoimmune diseases. "From bench to bedside" and "from bed to benchside"]

In recent years, new findings in immunology have been successfully converted to therapeutic principles, in particular for rheumatoid arthritis (RA) and spondylarthritides. The introduction of cytokine blockers in RA using tumor necrosis factor (TNF)-alpha and interleukin (IL)-1 inhibitors presented the first original therapy modalities in rheumatology, after proliferation-inhibiting drugs, such as methotrexate and cyclophosphamide, had been accepted in oncology. This advance was and is still being extended with the co-stimulation blockade using abatacept and IL-6 receptor inhibition. Anti-CD20 therapies are of particular importance, initially approved for the treatment of non-Hodgkin's lymphoma (NHL), this therapy modality has been approved in recent years for the treatment of RA following the failure of TNF-blockade. However, questions remain regarding the role of B cells in a number of autoimmune diseases, as well as the working principles of B-cell targeted therapy. In this context, close clinical observation of patients has yielded answers to and confirmation of basic scientific concepts.

New directions in the treatment of systemic lupus erythematosus

OBJECTIVE

The aim of this review is to provide an up-to-date overview of treatment approaches for systemic lupus erythematosus (SLE), highlighting the multiplicity and heterogeneity of clinical symptoms that underlie therapeutic decisions. Discussion will focus on the spectrum of currently available therapies, their mechanisms and associated side-effects. Finally, recent developments with biologic treatments including rituximab, epratuzumab, tumor necrosis factor (TNF) inhibitors, and belimumab, will be discussed.

RESEARCH DESIGN AND METHODS

A MEDLINE literature search for 'systemic lupus erythematosus' and 'damage' and 'treatment' was undertaken for 1996-2008. Secondary citations were obtained from selected manuscripts. Individual case studies were excluded.

FINDINGS

SLE is an autoimmune disease involving multiple organ systems, a clinical pattern of flares and remissions, and the presence of anti-nuclear autoantibodies. Whereas early symptoms most frequently involve the skin and joints, disease morbidity and mortality are usually associated with cardiovascular events and damage to major organs, particularly the kidneys. Many of the current therapeutic options are considered to be inadequate because of toxicities, accrual of organ damage, and insufficient control of the underlying disease pathology. Improved understanding of SLE pathogenesis and immunology has led to the identification of new treatment targets. Current interest is mainly focused on the targeted immunosuppressive actions provided by biologic therapy. Although the potential long-term beneficial or harmful effects of the new molecular treatments are unclear, their precise molecular targeting may reveal key relationships within the immune system and advance the cause of individualized molecular medicine.

CONCLUSIONS

Biologic compounds that target specific immunologic mechanisms offer a new paradigm in the treatment of SLE, one that may, at best, reverse the course of the disease and, at the very least, might provide some new alternatives to reduce symptoms and limit tissue damage without undue contribution to overall morbidity and mortality.

B cell-targeted therapies in autoimmunity: rationale and progress

B cells are recognized as main actors in the autoimmune process. Autoreactive B cells can arise in the bone marrow or in the periphery and, if not properly inhibited or eliminated, can lead to autoimmune diseases through several mechanisms: autoantibody production and immune complex formation, cytokine and chemokine synthesis, antigen presentation, T cell activation, and ectopic lymphogenesis. The availability of agents capable of depleting B cells (that is, anti-CD20 and anti-CD22 monoclonal antibodies) or targeting B cell survival factors (atacicept and belimumab) opens new perspectives in the treatment of diseases such as systemic lupus erythematosus, rheumatoid arthritis, type 1 diabetes, and multiple sclerosis.

Antibody engineering to develop new antirheumatic therapies

There has been a therapeutic revolution in rheumatology over the past 15 years, characterised by a move away from oral immuno-suppressive drugs toward parenteral targeted biological therapies. The potency and relative safety of the newer agents has facilitated a more aggressive approach to treatment, with many more patients achieving disease remission. There is even a prevailing sense that disease 'cure' may be a realistic goal in the future. These developments were underpinned by an earlier revolution in molecular biology and protein engineering as well as key advances in our understanding of rheumatoid arthritis pathogenesis. This review will focus on antibody engineering as the key driver behind our current and developing range of antirheumatic treatments.

The role of B lymphocyte stimulator (BLyS) in systemic lupus erythematosus

SLE, a chronic, multisystem autoimmune disorder with a broad range of symptoms, involves defective B cell selection and elimination of self-reactive B cells. B lymphocyte stimulator (BLyS), a soluble ligand of the TNF cytokine family, is a prominent factor in B cell differentiation, homeostasis, and selection. BLyS levels affect survival signals and selective apoptosis of autoantibody-producing B cells. High levels of BLyS may relax B cell selection and contribute to autoantibody production, exacerbating the SLE disease state. This review discusses the mechanism of BLyS action on B cells, its role in SLE, and specific targeting of BLyS in the treatment of SLE.

In vitro end points for the assessment of cellular immune response-modulating drugs

BACKGROUND

The concept of immunotoxicology and the development of a battery of immune-function assays to screen potential immunotoxic compounds have been increasingly used in the past. Immunotoxic outcome generally seems appropriate to evaluate the risk in drug development. Improving this approach is possible, by using methods now available, to study the effect of a chemical compound on the immune system.

OBJECTIVE

The goal of this review is to provide an overview of the current and recent methodologies for testing the immunological effect and immunotoxic risks in drug candidates.

METHODS

The methodological details here discussed include a synthetic description of the immunocompetent cells in cell-mediated immunity and the choice of the most appropriate assay (bioassays, immunoassays, molecular biology techniques, flow cytometry).

CONCLUSION

This review offers an assessment of in vitro models to study the toxic impact of (bio)pharmaceuticals on cellular immune system and aid drug scientists in understanding the significance and the methods to approach immunotoxicology.

B-cell-directed therapy for inflammatory skin diseases

The basic understanding of inflammatory dermatoses and autoimmune-mediated skin disorders has greatly advanced and broadened our understanding of underlying immune mechanisms that shape the complex network of chronic inflammation and autoimmunity. The new treatment options for psoriasis exemplify how new insights into (auto)immune responses, especially the role and function of various immune cells and proinflammatory cytokines, may lead to new therapeutic strategies. The concept of targeting B cells in autoimmune-mediated disorders is closely related to the discovery of autoantibodies and their cellular origin. However, the appreciation of B cells in autoimmunity has significantly changed and is not limited to their role as progenitors of autoantibody secreting plasma cells. Recent investigations of various inflammatory skin diseases, that is, autoimmune blistering disorders, collagen vascular diseases, and atopic dermatitis, actually support the concept that B cells might be as important as T cells in the etiopathogenesis of these disorders. The striking clinical improvement seen in patients with rheumatoid arthritis following B-cell depletion with the anti-CD20 mAb rituximab has tremendously catalyzed the interest in B-cell-targeted therapies in different autoimmune diseases. Future translational and clinical investigations are mandatory to precisely define the role and the contribution of impaired B-cell function in (auto)immune-mediated skin diseases.

Systemic Lupus Erythematosus: A Therapeutic Update

Systemic lupus erythematosus (SLE) is a complex autoimmune disease with variable clinical manifestations that is characterized by flares and periods of relative quiescence. The disease occurs approximately 10 times more frequently in women and is more prevalent among certain ethnic groups. The etiology is complex and dependent upon an interaction of genetic, hormonal, and environmental factors. Corticosteroids and immunosuppressive agents have transformed the outlook for patients with lupus. Unfortunately, the increased lifespan unmasked an accelerated process of atherosclerosis and cardiovascular disease. Early mortality is usually attributable to active lupus, but deaths late in the disease process are often secondary to thrombotic events. Advancements in the understanding of molecular and cellular mechanisms involved in the pathogenesis have resulted in development of novel therapies. Immunomodulatory drugs developed for other diseases are being investigated for use in specific manifestations of lupus. Individualization of treatment and lifelong monitoring are required in most patients.

CD19 regulates the development of bleomycin-induced pulmonary fibrosis in a mouse model

OBJECTIVE

The contribution of CD19 and B lymphocytes to pulmonary fibrosis is controversial. The aim of this study was to address the role of CD19 during the development of pulmonary fibrosis.

METHODS

Mice lacking or overexpressing the B cell surface molecule CD19, which is known as a positive regulator of B cell activation, were used in a model of bleomycin-induced pulmonary fibrosis. Ten or sixteen days after intratracheal injection of bleomycin, lung sections from mice were evaluated by histologic analysis. Seven days after instillation, the total leukocyte count and the number of B cells in bronchoalveolar lavage fluid (BALF) were determined, using a hemocytometer and flow cytometry. Bleomycin was also administered into selectin-deficient or intercellular adhesion molecule 1-deficient mouse strains. The level of CXCR3 expression on B cells was determined by flow cytometry.

RESULTS

CD19 deficiency significantly reduced susceptibility to intratracheal bleomycin challenge on day 16, while CD19 overexpression augmented fibrosis even on day 10. Furthermore, the survival rate and number of B cells in BALF also correlated with CD19 expression levels. The accumulation of B cells in BALF was dependent on CD19 levels, whereas there was no association with the levels of selectins or intercellular adhesion molecule 1. Additionally, CXCR3 was up-regulated in BALF B cells, while it was rarely expressed on circulating B cells. Furthermore, CD19 signaling facilitated B cell CXCR3 up-regulation in response to stimulation in vitro.

CONCLUSION

These results suggest that CD19 signaling is associated with the development of pulmonary fibrosis by controlling B cell infiltration into lung tissue, which may be associated with CXCR3 up-regulation.

B-cell-targeted therapy for systemic lupus erythematosus: an update

Systemic lupus erythematosus (SLE) is a classic autoimmune disease characterized by a myriad of immune system aberrations, most likely resulting from pathogenic autoantibody production, immune complex deposition, and subsequent end-organ damage. B cells play a key role in the pathogenesis; therefore, B-cell-targeted therapies, including B-cell depletion and blockage of B-cell survival factors such as B-lymphocyte stimulator (BLyS), are potential therapeutic targets for SLE. In uncontrolled clinical trials from approximately 20 studies, rituximab--a mouse-human chimeric anti-CD20 monoclonal antibody that effectively depletes B cells--has been demonstrated to reduce disease activity and decrease serum autoantibodies, with a clinical response of 86% in a case series of approximately 400 SLE patients with refractory disease, with or without concomitant use of cyclophosphamide. Epratuzumab, a humanized anti-CD22 monoclonal antibody that partially depletes B cells, has also been shown to reduce disease activity but not to decrease autoantibody levels in patients with moderately active SLE. Randomized controlled phase I/II trials in patients with active SLE have documented that belimumab, a humanized anti-BLyS monoclonal antibody, reduces B-cell numbers, inhibits disease activity and decreases anti-double-stranded DNA autoantibody in SLE patients. All these therapies are well tolerated, but accompanying infectious complications have been observed. Other B-cell-targeted therapies such as 'humanized' monoclonal antibodies to CD20 (e.g. ocrelizumab) and agents that interrupt B-cell/T-cell interactions also have potential, and the efficacy of these, along with rituximab, belimumab and epratuzumab, needs to be determined by randomized controlled trials.

Induction of mucosal tolerance in SLE: a sniff or a sip away from ameliorating lupus?

Systemic lupus erythematosus (SLE) is an autoimmune disease characterized by aberrant immune responses against intracellularly derived self antigens. Treatment for SLE relies on the use of aggressive immunosuppressants and steroids that are nonspecific and can cause serious adverse effects. The observation that a systemic immune tolerance to self antigens or generation of regulatory T cells may follow mucosal (nasal or oral) exposure to self proteins or monoclonal antibody against CD3 respectively suggests that induction of mucosal tolerance offers the basis of a side effect-free therapy that could re-establish the ability to distinguish self from non-self and restore peripheral tolerance in individuals susceptible to developing autoimmune diseases. Here I review studies on mucosal tolerance in autoimmune diseases and discuss the therapeutic potential of inducing tolerance for the treatment of SLE.

Biologic activity and safety of belimumab, a neutralizing anti-B-lymphocyte stimulator (BLyS) monoclonal antibody: a phase I trial in patients with systemic lupus erythematosus

Introduction

This trial evaluated the safety, biologic activity, and pharmacokinetics of belimumab, a fully human monoclonal antibody that inhibits the biologic activity of the soluble form of the essential B-cell survival factor B-lymphocyte stimulator (BLyS) in patients with systemic lupus erythematosus (SLE).

Methods

Seventy patients with mild-to-moderate SLE were enrolled in a phase I, double-blind, randomized study and treated with placebo (n = 13) or belimumab (n = 57) at four different doses (1.0, 4.0, 10, and 20 mg/kg) as a single infusion or two infusions 21 days apart. Patients were followed for 84 to 105 days to assess adverse events, pharmacokinetics, peripheral blood B-cell counts, serology, and SLE disease activity. Data from the study were summarized using descriptive statistics. χ² type tests were used to analyze discrete variables. The Kruskal-Wallis test, the Wilcoxon test, and the analysis of covariance were used to analyze the continuous variables, as appropriate. The analysis was performed on all randomized patients who received study agent.

Results

The incidences of adverse events and laboratory abnormalities were similar among the belimumab and placebo groups. Belimumab pharmacokinetics were linear across the 1.0 to 20 mg/kg dose range. Long terminal elimination half-life (8.5 to 14.1 days), slow clearance (7 ml/day per kg), and small volume of distribution (69 to 112 ml/kg) were consistent with a fully human antibody. Significant reductions in median percentages of CD20⁺ B cells were observed in patients treated with a single dose of belimumab versus placebo (day 42: P = 0.0042; and day 84: P = 0.0036) and in patients treated with two doses of belimumab versus placebo (day 105: P = 0.0305). SLE disease activity did not change after one or two doses of belimumab.

Conclusions

Belimumab was well tolerated and reduced peripheral B-cell levels in SLE patients. These data support further studies of belimumab in autoimmune disorders.

Trial Registration

NCT00657007 [clinicaltrials.gov].

Chemoimmunotherapy reinduction with epratuzumab in children with acute lymphoblastic leukemia in marrow relapse: a Children's Oncology Group Pilot Study

PURPOSE

To determine the tolerability and serum concentration of epratuzumab, a humanized monoclonal antibody targeting CD22, administered alone and in combination with reinduction chemotherapy in children with relapsed acute lymphoblastic leukemia (ALL), and to preliminarily assess tumor targeting and efficacy.

PATIENTS AND METHODS

Therapy consisted of a single-agent phase (epratuzumab 360 mg/m(2)/dose intravenously twice weekly x four doses), followed by four weekly doses of epratuzumab in combination with standard reinduction chemotherapy. Morphologic and minimal residual disease (MRD) responses were determined at the end of this 6-week period. Serum concentrations of epratuzumab were determined before and 30 minutes after infusions, and CD22 targeting efficiency was determined by quantifying changes in CD22 expression after epratuzumab administration.

RESULTS

Fifteen patients (12 fully assessable for toxicity) with first or later CD22-positive ALL marrow relapse enrolled on the feasibility portion of this study from December 2005 to June 2006. Two dose-limiting toxicities occurred: one grade 4 seizure of unclear etiology and one asymptomatic grade 3 ALT elevation. In all but one patient, surface CD22 was not detected by flow cytometry on peripheral blood leukemic blasts within 24 hours of drug administration, indicating effective targeting of leukemic cells by epratuzumab. Nine patients achieved a complete remission after chemoimmunotherapy, seven of whom were MRD negative.

CONCLUSION

Treatment with epratuzumab plus standard reinduction chemotherapy is feasible and acceptably tolerated in children with relapsed CD22-positive ALL. CD22 targeting was efficient, and the majority of patients achieved favorable early responses.

Treating patients with lupus with B-cell depletion

A new era in the treatment of systemic lupus erythematosus has dawned with the increasing introduction of monoclonal antibodies and other approaches, that target the key molecules involved in the pathogenesis of the disease. At present the ability to block the CD20 molecule on those B cells that carry this marker has proved the most effective way to treat patients resistant to conventional immunosuppressive drugs. However, these studies have all been open label and the results of double blind controlled studies are eagerly awaited.

B-cell-targeted treatment for multiple sclerosis: mechanism of action and clinical data

Strategies for treating autoimmune disorders are increasingly employing targeted therapies rather than non-specific, multitargeted treatments. Accumulating evidence on the involvement of B lymphocytes in the pathophysiology of autoimmune demyelinating disease has led to a renewed interest in B cells as potential therapeutic targets. In particular, antigen presentation between B cells and T cells, increased trafficking of B cells across the blood-brain barrier, and autoantibodies produced by plasma cells may contribute to the pathophysiology of autoimmune disorders such as multiple sclerosis. Several B-cell-targeted, depletion therapies are currently in development, including rituximab, epratuzumab, diphtheria toxin-single chain Fv (DC2219), belimumab, atacicept, abatacept, and abetimus sodium. Of these agents, only rituximab and abatacept have been evaluated in multiple sclerosis patients. Preliminary results of a phase II trial of rituximab in multiple sclerosis suggest that rituximab is well tolerated and significantly reduces the number of gadolinium enhancing lesions over 24 weeks of treatment. Results of an exploratory analysis suggest the potential promise of abatacept 10 mg/kg for multiple sclerosis. It is expected that future clinical trials will establish a role for B-cell-targeted therapies in the treatment of multiple sclerosis and other autoimmune neurological diseases. This article describes the mechanism of action behind B-cell-targeted depletion therapies in development and reviews available clinical data.

[Indications and options of new immune modulatory therapies for Sjögren's syndrome]

Sjögren's syndrome is a systemic inflammatory rheumatic disorder of unknown origin with so far inadequate therapy options. Management of Sjögren's syndrome is still primarily palliative using local symptomatic measures, and if appropriate glucocorticoids, NSAIDs and immunosuppressive drugs. New clues to the pathogenesis of this disorder pave the way for new therapeutic strategies. In particular targeting B-cells offers promising results and emphasizes the role of B-cells in the pathogenesis of this complex disorder. Rituximab was introduced into the standard treatment of different forms of low-grade and high-grade B-cell non-Hodgkins lymphomas, and is also an option for some lymphomas associated with Sjögren's syndrome. Whether interference with T-cell function is also a safe and effective strategy in Sjögren's syndrome, has to be shown in controlled clinical trials. However, there is no clear evidence to suggest that treatment with TNF-alpha blockers is efficacious in Sjögren's syndrome. Standardization of disease activity and outcome measurements are critical for further clinical trials for Sjögren's syndrome.

Targeted B-cell depletion therapy in childhood-onset systemic lupus erythematosus: progress to date

Childhood-onset systemic lupus erythematosus (SLE) is a multisystemic autoimmune disease associated with significant morbidity and mortality with lupus nephritis being a major prognostic factor. Children with SLE tend to have more severe hematologic and renal involvement compared with adults. Although the morbidity and mortality have greatly improved over the last 20 years, recent studies show that there are still associated major risks from under treatment (with resultant severe flares of disease activity) and over treatment (with additional medication adverse effects including risks of severe infection; many of these patients have inherent abnormal complement pathways). Therapies used to treat children with SLE need to be individualized based on multiorgan involvement, severity of disease, history of disease flares, and knowledge of recent relevant clinical, hematologic, and immunologic parameters. These medications need to be the most effective treatments, allowing normal growth, development, fertility, and the avoidance of severe toxicity and future malignancies. Many toxic effects of current medications range from the well described Cushingoid features of corticosteroids to the gastrointestinal adverse effects of mycophenolate mofetil. In vitro studies have shown that rituximab causes B-cell depletion by mechanisms involving antibody-dependent cell-mediated cytotoxicity, complement-dependent cytotoxicity, and direct signaling leading to apoptosis. As the adverse effect profile of B-cell depletion with rituximab has been well described in adults and children with oncologic and other autoimmune diseases, initial pilot studies using rituximab in patients with refractory SLE have been carried out according to different protocols. Evidence to date in open studies demonstrates that targeted B-cell depletion therapy can be safe and efficacious as an addition to standard immunosuppressant agents in refractory childhood-onset and adult-onset disease. Although there are positive outcomes in using this therapy, caution is necessary with respect to minimizing the number of doses and treatments given to reduce the incidence of developing human anti-chimeric antibodies. The next phase for the clinical and research community are multicenter randomized controlled trials of rituximab in severe childhood SLE, such as a comparative trial of rituximab versus intravenous cyclophosphamide in patients both at presentation and with exacerbations of disease activity.

Targeting B lymphocytes as therapy for ANCA-associated vasculitis

This article focuses on the initial results achieved with the more selective immunosuppressive approach of B-lymphocyte depletion in patients who fail cyclophosphamide or have contraindications for its use in the treatment of antineutrophil cytoplasmic antibody (ANCA)-associated vasculitis (AAV). This novel approach has sparked hope for patients and physicians in their search for effective, well-tolerated therapy for AAV. B-cell depletion is now undergoing rigorous investigation in randomized clinical trials.

B-cell-directed therapies in systemic lupus erythematosus

OBJECTIVE

Owing to their ability to promote the onset and flares of systemic lupus erythematosus (SLE), B-cells are now established as key players in the pathogenesis of the disease, and, therefore, have become a major therapeutic focus in SLE. In this article, we review the literature on B-cell-directed therapies for SLE focusing on B-cell depletion, B-cell tolerance, costimulatory signals, and cytokines that affect B-cell survival and activation.

METHODS

The clinical trials reviewed in this article were accessed from the PubMed database (www.pubmed.gov) and Clinical Trials database (www.clinicaltrials.gov) through an English language search of the literature published between January 2002 and March 2007. Keywords included the following terms: B-cells, SLE, and therapy.

RESULTS

Seventeen completed clinical trials enrolling 973 patients and 5 ongoing studies with anticipated enrollment of 785 patients were reviewed. Novel SLE therapies that target B-cells directly or indirectly were included. B-cell-depleting therapies with the monoclonal antibodies rituximab and epratuzumab have shown good therapeutic results. On the contrary, the well-studied B-cell tolerogen LJP 394 has not demonstrated much clinical benefit. Studies targeting costimulatory pathways have shown variable results; clinical trials with anti-CD40L antibody were terminated because of thromboembolic events, whereas studies targeting the B7-CD28 pathway seem promising. Anticytokine agents against B-lymphocyte stimulator (BLyS), interleukin (IL)-10, IL-6, and interferon alpha (IFN-alpha) are the newcomers that need further evaluation in the treatment of SLE.

CONCLUSIONS

Progress in technology has led to the variety of B-cell-directed therapies. In contrast to general immunosuppressants, novel treatments that interfere with specific aspects of B-cell functions create the possibility of developing targeted therapeutic approaches for specific subpopulations of lupus patients.

Biologic treatments for systemic rheumatic diseases

Many rheumatologic disorders, most notably Sjögren's syndrome, are associated with dental complications and in some cases oral diseases may trigger or drive connective tissue disease. During the past three decades the treatment in rheumatology was revolutionized by the introduction of disease-modifying anti-rheumatic drugs. Advances in our understanding of the pathogenesis of rheumatic diseases have led to the discovery of critical mechanisms of inflammation and autoimmunity and the invention of new target-specific biologic agents. In this review, we will summarize the current state of biologic therapies in rheumatology and discuss the implications of these on oral health and disease.

Systemic lupus erythematosus: pharmacological developments and recommendations for a therapeutic strategy

The management of systemic lupus erythematosus (SLE) has improved thanks to a better understanding of the immunopathogenesis of the disease and important advances in drug development. In contrast to the worrying paucity of new therapies for SLE at the end of the last century, several agents have emerged as useful treatments for this condition in the last decade. The efficacy of mycophenolate mofetil in the treatment of patients with lupus nephritis has been recently established in several clinical trials. There are increasing data from open-label studies to support the belief that B-cell depletion using the chimeric antibody rituximab is useful in the treatment of SLE. However, larger double-blind clinical trials to confirm this belief are awaited. Other specific targeted therapeutic agents that act by inducing B-cell depletion, inhibiting co-stimulatory molecules necessary for T-cell activation, tolerising B and T cells, blocking pro-inflammatory cytokines or complement and immunoablation are exciting advances in the race towards improving the outcome for patients with SLE.

[Systemic lupus erythematosus: news and therapeutic perspectives]

Lupus treatment has evolved considerably with spectacular advances that can be summarized in 10 points. Hydroxychloroquine and cyclophosphamide are still standard drugs, provided their use is optimized. Contraception and postmenopausal hormone replacement therapy have finally been tested in randomized studies with fairly reassuring results, although prudence remains essential in patients with severe lupus and above all in those with thrombotic complications (antiphospholipid syndrome). Mycophenolic acid has been shown to be useful in the treatment of lupus nephropathies, but its specific place in the therapeutic strategy remains to be defined. Other drugs (sirolimus, abatacept) are currently being evaluated. Anti-lymphocyte B therapies are growing in popularity. Rituximab and other drugs (anti-BAFF, TACI-Fc) are also being evaluated and their results appear very interesting. Interferon alpha (type I) inhibition is an attractive therapeutic approach in lupus but its use in humans is still premature. Peptide vaccination with fragments of autoantibodies or autoantigens is an elegant strategy, and preliminary results justify further studies. Anti-TNF molecules may be beneficial in lupus. Complement inhibition can be useful in lupus and antiphospholipid syndrome but drugs usable in humans (anti-C5) must be developed. Atheromatosis in lupus is the principal cause of morbidity and mortality and must be managed. Smoking cessation is essential, but other approaches (statins) should also be discussed. Many futuristic types of immune manipulation may be envisioned (proteasome inhibition, modulation of Fc gammaRIIB, and modulation of cell signaling (PI3kgamma)). Hence the perspectives are numerous. We will soon be able to optimize the treatment of our patients. Nevertheless, rigorous evaluation of the risk/benefit ratio of new drugs and of their most appropriate place in the therapeutic strategy against systemic lupus is indispensable.

Targeting of the immune system in systemic lupus erythematosus

Systemic lupus erythematosus (SLE) is a complex immune disorder in which loss of tolerance to nucleic acid antigens and other crossreactive antigens is associated with the development of pathogenic autoantibodies that damage target organs, including the skin, joints, brain and kidney. New drugs based on modulation of the immune system are currently being developed for the treatment of SLE. Many of these new therapies do not globally suppress the immune system but target specific activation pathways relevant to SLE pathogenesis. Immune modulation in SLE is complicated by differences in the immune defects between patients and at different disease stages. Since both deficiency and hyperactivity of the immune system can give rise to SLE, the ultimate goal for SLE therapy is to restore homeostasis without affecting protective immune responses to pathogens. Here we review recent immunological advances that have enhanced our understanding of SLE pathogenesis and discuss how they may lead to the development of new treatment regimens.

The potential utility of B cell-directed biologic therapy in autoimmune diseases

Increasing awareness of the importance of aberrant B cell regulation in autoimmunity has driven the clinical development of novel B cell-directed biologic therapies with the potential to treat a range of autoimmune disorders. The first of these drugs-rituximab, a chimeric monoclonal antibody against the B cell-specific surface marker CD20-was recently approved for treating rheumatoid arthritis in patients with an inadequate response to other biologic therapies. The aim of this review is to discuss the potential use of rituximab in the management of other autoimmune disorders. Results from early phase clinical trials indicate that rituximab may provide clinical benefit in systemic lupus erythematosus, Sjögren's syndrome, vasculitis, and thrombocytopenic purpura. Numerous case reports and several small pilot studies have also been published reporting the use of rituximab in conditions such as myositis, antiphospholipid syndrome, Still's disease, and multiple sclerosis. In general, the results from these preliminary studies encourage further testing of rituximab therapy in formalized clinical trials. Based on results published to date, it is concluded that rituximab, together with other B cell-directed therapies currently under clinical development, is likely to provide an important new treatment option for a number of these difficult-to-treat autoimmune disorders.

Anti-CD20 monoclonal antibody in rheumatoid arthritis and systemic lupus erythematosus

Rheumatoid arthritis (RA) and systemic lupus erythematosus (SLE) are both chronic autoimmune rheumatic diseases. In the last few years, evolution in the understanding of RA and SLE pathogenesis and underlying molecular mechanisms has resulted in development and availability of novel therapies. In particular, the recent acknowledgement of a more significant role for B cells in the pathogenesis of RA, in contrast to the view that it was predominantly a T cell disorder, provided rationale for trials of B cell depletion therapy with the chimeric anti-CD20 monoclonal antibody rituximab. The efficacy and favourable safety profile of rituximab have resulted in the recent approval by the European Medicines Agency for its usage in patients with RA unresponsive to conventional therapies. The salient features from the pivotal open and randomised controlled trials are reviewed in this chapter. Given the recognition of B cell dysfunction as central to SLE pathogenesis, the use of anti-CD20 antibody therapy for this patient group has also been established. Results of the open trials have been encouraging, particularly in patients not responding to usual therapies, and a randomised controlled trial is underway.

Autosomal loci associated with a sex-related difference in the development of autoimmune phenotypes in a lupus model

Sex-related differences (SrD) are a general characteristic of human autoimmune diseases. There is an increasing body of evidence that suggests a link between sex-related hormones and autoimmune onsets. Here, through a genetic approach using a lupus mouse model, we attempted to show the involvement of genetic factors in the development of SrD in autoimmune diseases. Using MRL/lpr x (MRL/lpr x C57BL/6.Fas(lpr))F1 (MBN2) mice, the whole genome was searched to identify linkage loci to autoimmune phenotypes inherited from a lupus MRL/Mp.Fas(lpr) (MRL/lpr) strain of mice, which exhibits glomerulonephritis, splenomegaly and antinuclear autoantibody. The genome-wide association study confirmed four linkage loci on chromosomes 4, 7, 13, and 17. Furthermore, differential analyses performed using male and female groups of MBN2 mice revealed that two loci located on chromosomes 4 (41-72 cM, MRL/lpr allele) and 7 (4-21 cM, B6/lpr allele) were male specific and suppressed autoimmune phenotypes. Notably, the sum effect of the two loci adequately explained a range of SrD developed in the MBN2 mice. Our present findings suggest the presence of a male-predominant mechanism underlying the development of SrD in autoimmunity, depending on the effects of autosomal loci under an undefined male-specific condition.

Development of biologicals for the therapy of lupus erythematosus

Lupus erythematosus is a chronic autoimmune inflammatory disease with largely unknown etiopathogenesis and no known cure. However, key steps in its pathophysiology have been recognized and targeted by specific therapeutic techniques. Human patients and murine models of lupus erythematosus manifest a wide range of immunological abnormalities. Therapeutic antibodies, which affect the activation of potentially autoreactive B cells, have been developed and are being tested in clinical trials. Preclinical studies have provided proof of concept for the feasibility and efficacy of gene therapy in human lupus erythematosus. In this article, we briefly review the clinical characteristics and immunological abnormalities of lupus erythematosus and summarize recent studies on the use of therapeutic antibodies and gene therapy for the management of human lupus erythematosus.

B-cell targeting: a novel approach to immune intervention today and tomorrow

B cells and their products, antibodies, play an important role in the diagnosis and, in some instances, in the pathogenesis of many autoimmune diseases. Specific B-cell directed therapies are of recent interest as their impact on B-cell activity can influence a variety of autoimmune diseases. The development and introduction of rituximab, a depleting antibody targeting CD20+ B cells, and previously CD52-directed treatment with Campath-1h for the treatment of B-cell malignancies as well as rheumatoid arthritis have pioneered this therapeutic field. Other non-depleting strategies employ CD22 or B-cell activating factor/B lymphocyte stimulator and apoptosis-inducing ligand as targets and are under clinical investigation at present. Abnormalities of B-cell subsets have been identified by a number of independent groups which often represent characteristic patterns of disturbances of the human B-cell repertoire. However, the clinical value of specific B-cell subset targeting/depletion has not been addressed extensively. As such an approach may afford the possibility to avoid unnecessary adverse events related to depletion of non-pathogenic B-cell populations, B-cell subset targeting may have the capacity to enhance the benefit/risk ratio of B-cell immune intervention.

Targeting CD22 as a strategy for treating systemic autoimmune diseases

B-cells play an important role in the diagnosis and to some extent the pathogenesis of many autoimmune diseases. Specific B-cell directed antibodies are now gaining an increasing role in the management of these diseases. The first antibody target in this regard was CD20, with the development and introduction of rituximab in the management of B-cell malignancies as well as rheumatoid arthritis. A second candidate target is CD22, and the first antagonistic antibody to this B-cell marker is epratuzumab, which appears to function, in contrast to CD20 antibodies, more by modulation of B-cells than by their depletion capacity. Originally developed for the treatment of non-Hodgkin lymphoma, epratuzumab has now been reported to be effective, with a very good safety profile, in two prototype autoimmune diseases, systemic lupus erythematosus and primary Sjögren's syndrome. As such, this new investigational antibody may provide distinct therapeutic effects and may be complementary to the known effects and role of CD20 antibodies.