Epratuzumab (humanised anti-CD22 antibody) in primary Sjögren's syndrome: an open-label phase I/II study

Topical and systemic medications for the treatment of primary Sjögren's syndrome

The treatment of primary Sjögren's syndrome (SS) is based principally on the management of sicca features and systemic manifestations. Sicca manifestations are treated symptomatically through administration of topical therapies, such as saliva substitutes and artificial tears; in patients with residual salivary gland function, stimulation of salivary flow with a sialogogue is the therapy of choice. The management of extraglandular features must be tailored to the specific organ or organs involved; however, limited data have been obtained from controlled trials in SS to guide the treatment of systemic symptoms using therapies including antimalarials, glucocorticoids, immunosuppressive drugs and biologic agents. Nevertheless, randomised controlled trials of biologic agents that target molecules and receptors involved in the aetiopathogenesis of primary SS have initiated a new era in the therapeutic management of the disease, although the potential risks and benefits of these agents must be carefully considered. In this Review, we analyse the evidence regarding the efficacy of the therapeutic agents currently available to treat the manifestations of SS. On the basis of this evidence, we provide guidance on the use of these agents in different clinical scenarios.

Translational Mini-Review Series on B cell subsets in disease. Transitional B cells in systemic lupus erythematosus and Sjögren's syndrome: clinical implications and effects of B cell-targeted therapies

Systemic lupus erythematosus (SLE) and Sjögren's syndrome are autoimmune disorders which are characterized by a disturbed B cell homeostasis which leads ultimately to dysfunction of various organs. One of the B cell subsets that appear in abnormal numbers is the population of transitional B cells, which is increased in the blood of patients with SLE and Sjögren's syndrome. Transitional B cells are newly formed B cells. In mice, transitional B cells undergo selection checks for unwanted specificity in the bone marrow and the spleen in order to eliminate autoreactive B cells from the circulating naive B cell population. In humans, the exact anatomical compartments and mechanisms of the specificity check-points for transitional B cells remain unclear, but appear to be defective in SLE and Sjögren's syndrome. This review aims to highlight the current understanding of transitional B cells and their defects in the two disorders before and after B cell-targeted therapies.

Susceptibility of patients with rheumatic diseases to B-cell non-Hodgkin lymphoma

Autoimmune rheumatic diseases (ARD), such as systemic lupus erythematosus (SLE), rheumatoid arthritis (RA) and Sjögren's syndrome (SS), have consistently been associated with the development of B-cell non-Hodgkin lymphoma (BCNHL). In this Review, we focus on reports published since 2006 and summarize the data regarding the BCNHL subtypes and clinical findings associated with this increased risk. Patients with these ARD, particularly those with detectable autoantibodies and systemic involvement, are at increased risk of developing BCNHL, especially diffuse large B-cell lymphoma and marginal zone lymphoma. SS shows the strongest association with BCNHL. Male sex, advanced age, prolonged disease course and increased disease severity, but not family history of autoimmune conditions, seem to be associated with an increased risk of non-Hodgkin lymphoma. Chronic immune stimulation, genetic and environmental factors and some immunosuppressive drugs might be involved in lymphomagenesis in these patients. The reason why some ARD are associated with BCNHL and other autoimmune diseases are not remains unclear. These associations are important as they provide information about the mechanisms of lymphomagenesis, and might help identify new therapeutic targets.

[Etiologic treatment of sicca syndrome. What can the rheumatologist offer?]

No effective treatment has been documented for the glandular primary Sjögren syndrome (PSS) despite the development of oral and biologic agents that have significant activity against other autoimmune disorders. Some disease-modifying agents have been empirically evaluated for the treatment of PSS. Targeting B cells also seems very promising in SSP because of the B-cell hyperactivity recognized in this desease. This article reviews existing data on the use of disease-modifying therapy for glandular of SSP. To date, published studies and trials of oral DMARDs for the treatment of SSP have shown disappointing results. B-cell modulation is clearly a promising therapy for PSS. Many challenges in trial design and execution are evident from the studies reviewed.

Epidemiology and management of refractory lupus nephritis

Although the survival of patients with lupus nephritis (LN) has improved considerably in recent years, refractory LN appears in a substantial proportion of patients and, therefore, treatment of LN remains a real challenge today. We will use the term "refractory" LN, for those cases with none or partial response to first-line therapies. In this sense, numerous epidemiological factors, including racial, socioeconomic, histological and serological parameters, may influence treatment response and, therefore, may have an impact on the outcome of renal involvement. Initial conventional therapy will depend somewhat on these epidemiological factors. If this initial therapy fails, fortunately today we have alternative therapies that include the multitarget therapy and the use of biologics. Published evidence about these therapies is presented in this review. Important terms in the management of LN, such as the definition of complete response, partial response, sustained response and renal flare as well as the discrimination of different types of flare, are also discussed here according to the European consensus statement on the terminology used in the management of lupus glomerulonephritis.

Biological therapies in primary Sjögren's syndrome

INTRODUCTION

Primary Sjögren's syndrome (PSS) is a relatively common immune-mediated condition characterized by oral and ocular dryness, fatigue, musculoskeletal pain and poor health-related quality of life. Other extra-glandular organs can also be affected and PSS is associated with a markedly increased risk of lymphoma. Furthermore, the health-economic cost for PSS is substantial. There is currently no effective treatment available. With better understanding of the pathophysiology of PSS and advances in technologies, it is now possible to develop biological therapies to target specific molecules or molecular pathways that are important in PSS pathogenesis. Indeed, a limited number of biological therapies have already been tested in PSS with mixed successes.

AREAS COVERED

Published data on the use of biological therapies in PSS, the possible roles for other biological therapies and the potential challenges for their use.

EXPERT OPINION

The use of biological agents targeting key cellular and molecular pathways in PSS pathogenesis represents a promising therapeutic strategy. Clinical trials assessing the efficacy of biological therapies in PSS should be encouraged but patient selection and outcome measures used in these studies must be carefully considered to ensure that the true effects of biological therapies on the outcomes of PSS are being appropriately evaluated.

Treatment of systemic lupus erythematosus with epratuzumab

Systemic lupus erythematosus is a prototypic autoimmune disease characterized by abnormalities in the activity of B-cells and T-cells. A novel specific treatment for autoimmune diseases is B-cell depletion with monoclonal antibodies. Epratuzumab is a monoclonal antibody that targets CD22 antigen on B-cells. Initial phase II and two terminated early phase III studies suggest that treatment of systemic lupus erythematosus with this immunomodulatory agent is effective, well tolerated and significantly improves the patient's quality of life. In vitro studies and clinical trials with non-Hodgkin lymphoma patients indicate epratuzumab can potentially serve as a complementary drug in combination therapy with another inhibitor of B-cell activity, rituximab, which is a monoclonal anti-CD20 antibody.

What have we learned from clinical trials in primary Sjögren's syndrome about pathogenesis?

In vitro and in vivo experimental data have pointed to new immunopathogenic mechanisms in primary Sjögren's syndrome (pSS). The availability of targeted treatment modalities has opened new ways to selectively target these mechanistic pathways in vivo. This has taught us that the role of proinflammatory cytokines, in particular TNFα, is not crucial in the immunopathogenesis of pSS. B cells appear to play a major role, as depletion of B cells leads to restoration of salivary flow and is efficacious for treatment of extraglandular manifestations and mucosa-associated lymphoid tissue lymphoma. B cells also orchestrate T-cell infiltration and ductal epithelial dearrangement in the salivary glands. Gene profiling of salivary gland tissue in relation to B-cell depletion confirms that the axis of IFNα, B-cell activating factor, B-cell activation, proliferation and survival constitutes a major pathogenic route in pSS.

Therapeutic targeting of B cells for rheumatic autoimmune diseases

Autoreactive B cells are characterized by their ability to secrete autoantibodies directed against self-peptides. During the last decade, it has become increasingly apparent that B lymphocytes not only produce autoantibodies but also exert important regulatory roles independent of their function as antibody-producing cells. This is especially relevant in the context of autoimmunity, because autoreactive B cells have been shown to possess the ability to activate pathogenic T cells, to produce pro-inflammatory cytokines, and to promote the formation of tertiary lymphoid tissue in target organs. The production of monoclonal antibodies against B-cell-surface molecules has facilitated the characterization of several distinct B lymphocyte subsets. These cell-surface molecules have not only served as useful cell differentiation markers but have also helped to unravel the important biological functions of these cells. Some of these molecules, all of which are expressed on the cell surface, have proven to be effective therapeutic targets. In both animal models and in clinical assays, the efficient elimination of B lymphocytes has been shown to be useful in the treatment of rheumatoid arthritis and other autoimmune diseases. The treatment of most rheumatic autoimmune diseases relies mainly on the use of cytotoxic immunosuppressants and corticosteroids. Although this has resulted in improved disease survival, patients may nonetheless suffer severe adverse events and, in some cases, their relapse rate remains high. The increasing need for safer and more effective drugs along with burgeoning new insights into the pathogenesis of these disorders has fueled interest in biological agents; clinical trials involving the B-cell depletion agent rituximab have been especially promising. This article reviews the current knowledge of B-cell biology and pathogenesis as well as the modern therapeutic approaches for rheumatic autoimmune diseases focusing in particular on the targeting of B-cell-specific surface molecules and on the blocking of B-cell activation and survival.

Emerging small molecule and biological therapeutic approaches for the treatment of autoimmunity

IMPORTANCE OF THE FIELD

Biological therapeutics targeting TNF-α, IL-6, CD20 and CD80/86 is proving to be an important weapon in the clinicians' armory to fight autoimmunity alongside long-standing small molecule therapeutics such as methotrexate and glucocorticoids. However, there still remains a high unmet clinical need in the field of autoimmunity and many researchers are continuing to discover and develop new therapeutics to address this.

AREAS COVERED IN THIS REVIEW

A new wave of small molecule and biological therapeutics targeting different pathways is being developed which could generate exciting new options for clinicians. This review aims to highlight those emerging therapies that are most advanced in clinical development.

WHAT THE READER WILL GAIN

The reader will gain an appreciation of new approaches being developed to address the high unmet clinical need in the field of autoimmunity.

TAKE HOME MESSAGE

Despite recent success in the development of therapeutics to treat autoimmunity, new therapeutic strategies are being developed to address the remaining areas of a high unmet clinical need.

Pathogenesis of Sjögren's syndrome and therapeutic consequences

PURPOSE OF REVIEW

To summarize recent findings on new pathogenic mechanisms of interaction between genetic and environmental factors and between innate and adaptive immunity in primary Sjögren's syndrome and to reconcile pathogenesis and treatment by focusing on the crucial pathogenic steps that could be targeted by emerging therapies.

RECENT FINDINGS

Regarding genetic predisposition, the functional relevance of IRF5 and STAT4 gene polymorphisms in the activation of type I interferon pathways has been demonstrated. It has also been shown that the isolated stimulation of innate immunity in mice can result in dryness, which precedes lymphocytic infiltrates in salivary glands. In animal models, possible environmental triggers of the disease, such as oestrogen deficiency and/or infection by Epstein-Barr virus, can lead to innate immune followed by autoimmune epithelitis. The IFN-BAFF-B lymphocyte pathogenic axis is, therefore, targeted by numerous drugs currently in evaluation. The development of consensus disease activity scores and patient-related outcomes might help to initiate new controlled trials. The first positive randomized controlled trial with rituximab has been recently published.

SUMMARY

Hopefully, persistent and joint efforts by many teams to improve the knowledge on the pathogenesis of the disease may allow identification of new therapeutic targets in Sjögren's syndrome.

Targeting B cells with biologics in systemic lupus erythematosus

IMPORTANCE OF THE FIELD

The use of biologics as immune modulators in several autoimmune diseases has provided new tools to the physician's therapeutic armamentiarium and has led to improved patients' outcomes and quality of life. By producing autoantibodies, B cells in systemic lupus erythematosus (SLE) are key players in the pathogenesis of the disease and in its clinical manifestations. Therefore, biologics that target B cells in SLE aim at reducing the activity of these cells for the induction of remissions and/or amelioration of disease activity, reduction of organ involvement, and limitation of the complications and side effects caused by immunosuppressive therapies.

AREAS COVERED IN THIS REVIEW

This review describes the past and current clinical trials with B-cell-targeted biologics in SLE, to provide a historical perspective and the state-of-the-art on the topic.

WHAT THE READER WILL GAIN

We review how the disappointment in the field from promising agents has been instrumental in providing valuable lessons leading to an improved design of new trials that are now giving encouraging results.

TAKE HOME MESSAGE

In systemic lupus erythematosus (SLE), the use of B-cell-based biologics in clinical trials has shown both disappointment and promise.

Emerging biotherapies for Sjögren's syndrome

IMPORTANCE OF THE FIELD

Sjögren's syndrome (SS) is an autoimmune epithelitis. This exocrinopathy is frequently associated with extraglandular complications, and the patients are at risk of developing B cell lymphoma. Given the lack of disease-modifying drugs, and the fact that SS is a quintessential B-cell mediated disease, attention has recently been focused on biotherapies.

AREAS COVERED IN THIS REVIEW

Despite negative grounds, TNF-alpha antagonists have been tested in the disease, and proven not be efficient. However, B-cell depleting therapy using anti-CD20 antibodies such as rituximab, which is a chimeric mAb, has shown promise in the field, while anti-CD22 mAb seems to be less active.

WHAT THE READER WILL GAIN

New treatments against the B-cell activating factor of the TNF family are about to be tested, or replaced by receptor immunoglobulin decay protein.

TAKE HOME MESSAGE

B-cell depleting therapies seem promising in SS, but no data are, thus far, available on treatments targeting B-cell activating factor of the TNF family.

The point on the ongoing B-cell depleting trials currently in progress over the world in primary Sjögren's syndrome

Conventionnal therapy (moisturizers, pilocarpine, Cevimeline, local Cyclosporine, and hydroxychloroquine) remains the basis for the treatment of primary Sjögren's syndrome (pSS) but they do not modify the course of the disease. Rituximab is currently the most fully evaluated biologics in pSS. Open-label studies suggest that Rituximab is well tolerated (although infusion-related reactions and serum sickness remain possible), induces a rapid depletion of B cells in the blood and salivary glands, and could improve early active pSS or pSS with active extra glandular involvement. Two small double blind randomized studies have been conducted and now published, demonstrating its efficacy on fatigue and sicca syndrome in early disease. Two large double blind studies are currently ongoing or planned: The TEARS study (Tolerance and EfficAcy of Rituximab in primary Sjögren syndrome) in France, is currently including 120 patients having either a recent and active disease and/or at least one extraglandular severe signs. The 'TRACTISS' Study (Anti-B-Cell Therapy In Patients With Primary Sjögren's Syndrome), in UK, will include 100 patients having anti-Ro/La antibodies, reduced basal secretion but an increased salivary flow with stimulation, within 10years of diagnosis, symptomatic oral dryness, fatigue and at least one systemic feature.

[Current therapeutic options in Sjögren's syndrome]

Sjögren's syndrome is a systemic inflammatory-rheumatic disorder of hitherto unknown origin and, hence, adequate therapy options are not available in most cases. Treatment of sicca symptoms in Sjögren's patients is primarily symptomatic. Glucocorticoids, NSAIDs and/or immunosuppressive drugs may be used for the treatment of extraglandular manifestations or complications. Although there have been few clinical studies to date, new insights into the pathogenesis of this disorder may permit novel therapeutic strategies. Targeting B-cell candidates as a new therapeutic option in this entity has shown promising results. B-cell-depletion using Rituximab has been tested in initial clinical trials for the treatment of Sjögren patients, both with and without associated B-cell non-Hodgkin-lymphoma; however, further studies as well as reliable outcome criteria are needed. Further therapeutic options are currently in development or early clinical testing.

Primary Sjögren's syndrome: pathophysiological, clinical and therapeutic advances

Primary Sjögren's syndrome was long a vexing dilemma, as the underlying pathophysiological mechanisms remained obscure, disease activity was challenging to evaluate, and no specific treatments were known to be effective. However, recent years have witnessed major advances in these three areas. Convincing evidence has been obtained that innate immunity, most notably mediated by the interferons, plays a role in the initial B-cell activation. A disease activity score was developed during a consensus conference sponsored by the EULAR. Even more importantly, B-cell depletion constitutes a highly promising therapeutic approach. Thus, rituximab was effective in two controlled clinical trials.

Primary Sjogren's syndrome: too dry and too tired

Chronic fatigue is one of the most prevalent and debilitating symptoms in primary SS (pSS). Approximately 70% of pSS patients suffer from disabling fatigue, which is associated with reduced health-related quality of life. In this article, we review the instruments used for evaluating pSS-related fatigue, our current understanding of the underlying psychosocial and physiological mechanisms of fatigue in pSS and the therapeutic strategies that have been studied in the management of fatigue in pSS.

Autoantibody-mediated regulation of B cell responses by functional anti-CD22 autoantibodies in patients with systemic sclerosis

Studies have demonstrated that B cells play important roles in systemic sclerosis (SSc), especially through the CD19/CD22 autoimmune loop. CD22 is a B cell-specific inhibitory receptor that dampens B cell antigen receptor (BCR) signalling via tyrosine phosphorylation-dependent mechanism. In this study, we examined the presence and functional property of circulating autoantibodies reacting with CD22 in systemic sclerosis. Serum samples from 10 tight skin (TSK/+) mice and 50 SSc patients were assessed for anti-CD22 autoantibodies by enzyme-linked immunosorbent assays using recombinant mouse or human CD22. The association between anti-CD22 antibodies and clinical features was also investigated in SSc patients. Furthermore, the influence of SSc serum including anti-CD22 autoantibodies for CD22 tyrosine phosphorylation was examined by Western blotting using phosphotyrosine-specific antibodies reacting with four major tyrosine motifs of CD22 cytoplasmic domain. Anti-CD22 autoantibodies were positive in 80% of TSK/+ mice and in 22% of SSc patients. Patients positive for anti-CD22 antibodies showed significantly higher modified Rodnan skin thickness score compared with patients negative for anti-CD22 antibodies. Furthermore, anti-CD22 antibodies from patients' sera were capable of reducing phosphorylation of all four CD22 tyrosine motifs, while sera negative for anti-CD22 antibodies did not affect CD22 phosphorylation. Thus, a subset of SSc patients possessed autoantibodies reacting with a major inhibitory B cell response regulator, CD22. Because these antibodies can interfere CD22-mediated suppression onto B cell activation in vitro, SSc B cells produce functional autoantibodies that can enhance their own activation. This unique regulation may contribute to the autoimmune aspect of SSc.

B cell-targeted therapies in Sjögren's syndrome

Sjögren's syndrome (SS) or autoimmune epithelitis is characterized by focal lymphocytic infiltrates surrounding the tubular epithelium of exocrine glands and by overactivity of the B-cell population. Although T cells were long considered the main effectors in SS, recent findings indicating a key role for B cells have prompted studies of treatments designed to deplete the B-cell population. Among molecules that can be targeted to achieve B-cell depletion, CD20 and CD22 are surface antigens expressed specifically by B lymphocytes; and the cytokine B-cell-activating factor belonging to the TNF family (BAFF) is a TNF receptor ligand involved in B-cell differentiation, survival, and activation. The aim of this review is to discuss the clinical outcomes of SS patients treated with B-cell depletion.

Targeting B cells in immune-mediated inflammatory disease: a comprehensive review of mechanisms of action and identification of biomarkers

B cell-depletion therapy, particularly using anti-CD20 treatment, has provided proof of concept that targeting B cells and the humoral response may result in clinical improvements in immune-mediated inflammatory disease. In this review, the mechanisms of action of B cell-targeting drugs are investigated, and potential biomarkers associated with response to treatment in patients with autoimmune diseases are identified. Most available data relate to B cell depletion using anti-CD20 therapy (rituximab) in patients with rheumatoid arthritis (RA). Treatment leads to significant clinical benefit, but apparently fails to deplete long-lived plasma cells, and discontinuation is associated with relapse. Biomarkers commonly used in studies of B cell-targeted therapies include rheumatoid factor, anti-citrullinated peptide antibodies, and immunoglobulin (Ig) levels. More recently, there has been interest in markers such as B cell phenotype analysis, and B lymphocyte stimulator (BLyS)/a proliferation-inducing ligand (APRIL), the latter particularly in studies of the IgG Fc-transmembrane activator and CAML interactor (TACI) fusion protein (atacicept) and anti-BLyS therapy (belimumab). Data from clinical trials of B cell-depleting agents in RA suggest that specific autoantibodies, BLyS, APRIL, and circulating and synovial B lineage cell levels may have potential as biomarkers predictive of response to treatment. Further trials validating these markers against clinical outcomes in RA are required. In patients with systemic lupus erythematosus, Fc receptors and levels of circulating immune cells (including B cells and natural killer cells) may be relevant markers.

Novel targeted therapies for autoimmunity

The emergence of new targeted therapies is rapidly improving the treatment of autoimmune disease. These drugs have been variably designed to deplete specific T and B cell subsets, interrupt receptor-ligand interactions, and inhibit the activity of inflammatory mediators relevant to immune function. Abatacept, a co-stimulatory blocker, and rituximab, a B cell depleting antibody, are among the approved therapies seeking new indications, while the newer therapies include Fc receptor-non-binding CD3-specific antibodies, IL-12/23 antibodies, an IL-6 receptor antagonist, a sphingosine-1-phosphate agonist, and small molecule inhibitors of intracellular protein kinases. Antigen-specific therapies are in their infancy, but the latest results administering glutamic acid dehydrogenase peptide to type 1 diabetics are promising. In the future, treatment strategies may increasingly explore the use of drug combinations acting at multiple sites of aberrant immunoregulation to achieve disease quiescence and immune tolerance.

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.

Potent small molecule mouse CD22-inhibitors: exploring the interaction of the residue at C-2 of sialic acid scaffold

Our previous study revealed that compound 1 (9-(4'-hydroxy-4-biphenyl)acetamido-9-deoxy-Neu5Gcalpha2-6GalOMP) has the most promising affinity for mCD22. Replacing the subterminal galactose residue of 1 with benzyl or biphenylmethyl as aglycone led to 38- and 20-fold higher potency, respectively. This discovery represents a new direction in inhibitor design suitable for pharmaceutical development.

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.

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.

Therapeutic potential for B-cell modulation in Sjögren's syndrome

B-cell hyperactivity has been recognized for a long time in Sjögren's syndrome. This B-cell activation is firstly polyclonal but can progress to monoclonal B-cell lymphoproliferation. This article addresses the therapeutic potential of B-cell modulation in Sjögren's syndrome.

Anti-CD20 treatment in primary Sjögren's syndrome

We performed a search for publications on rituximab (Rtx) in the treatment of primary Sjögren's syndrome (pSS), and assessed the reports for the efficacy of the drug on complaints like sicca symptoms, systemic manifestations and pSS associated lymphoma. We also reviewed the effects on laboratory parameters and potential adverse effects. From the published literature there is little evidence supporting Rtx to have an effect on sicca symptoms, and there is particularly lack of objective improvements in measures of oral and ocular dryness. Systemic manifestations such as fatigue, synovitis, arthralgia, cryoglobulinaemia-related vasculitis, neurological, renal and pulmonary involvement all seem to react favourably to Rtx treatment. The effect on pSS associated non-Hodgkin's lymphoma is also beneficial. Rheumatoid factor concentration is decreasing during Rtx treatment. The levels of anti-SSA and -SSB antibodies are, however, unaltered according to the majority of the studies. The most common complications to Rtx treatment are mild and transient infusion related reactions. Delayed moderate-to-severe reactions are less common, and occur mostly in patients who develop human anti-chimeric antibodies. In conclusion, Rtx is a promising treatment option for severe pSS with systemic complications, but more data from randomized controlled trials are warranted before conclusions on the drug's role can be made with more accuracy.

Translating co-stimulation blockade into clinical practice

Currently available information from clinical trials and open-label extensions suggest that abatacept is a good alternative to other biologicals in rheumatoid arthritis. Although at first glance the efficacy of all biologicals appears to be the same, in routine practice one might expect there to be differences in effectiveness, safety profiles and specific patient-centered outcomes. These patient-centered outcomes, as well as safety, deserve further attention in follow-up registries, but also in prospective studies, if we are to optimize patient care. After failing a first tumor necrosis factor blocker, patients have several treatment options - starting a second tumor necrosis factor blocker, or rituximab or abatacept - but no formal randomized studies are available to indicate what is the optimal strategy. Potential differences between treatments with biologicals with different modes of action in very early disease also require more study. It is difficult to determine how co-stimulation blockade will influence Crohn's disease or psoriatic arthritis as well as other diseases characterized by a specific role of the adaptive immune system, such as systemic lupus erythematosus and multiple sclerosis. It is clear, however, that every additional targeted therapy creates new opportunities for treatment in many different patient populations.

[B-cell-depleting antibodies in skin diseases]

Basic insight into immune mechanisms, particularly the role and function of various immune cells and proinflammatory cytokines in the etiopathogenesis of inflammatory dermatoses and autoimmune skin disorders, has made possible the development of novel therapeutic strategies. Because of their properties as antigen presenting cells and progenitors of autoantibody-secreting plasma cells, B cells have a major impact in different autoimmune diseases and represent an important therapeutic target. The remarkable clinical improvement seen in patients with rheumatoid arthritis after treatment with the monoclonal anti-CD20 antibody, rituximab, has strongly augmented the interest in B-cell-targeted therapies in different autoimmune diseases. Future clinical and immunological investigations are mandatory to precisely define the contribution of impaired B-cell function in development and progression of autoimmune mediated skin disorders.

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.

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.

Bifunctional CD22 ligands use multimeric immunoglobulins as protein scaffolds in assembly of immune complexes on B cells

CD22 is a B cell-specific sialic acid-binding immunoglobulin-like lectin (Siglec) whose function as a regulator of B cell signaling is modulated by its interaction with glycan ligands bearing the sequence NeuAc alpha2-6Gal. To date, only highly multivalent polymeric ligands (n = 450) have achieved sufficient avidity to bind to CD22 on native B cells. Here we demonstrate that a synthetic bifunctional molecule comprising a ligand of CD22 linked to an antigen (nitrophenol; NP) can use a monoclonal anti-NP IgM as a decavalent protein scaffold to efficiently drive assembly of IgM-CD22 complexes on the surface of native B cells. Surprisingly, anti-NP antibodies of lower valency, IgA (n = 4) and IgG (n = 2), were also found to drive complex formation, though with lower avidity. Ligands bearing alternate linkers of variable length and structure were constructed to establish the importance of a minimal length requirement, and versatility in the structural requirement. We show that the ligand drives assembly of IgM complexes exclusively on the surface of B cells and not other classes of white blood cells that do not express CD22, which lends itself to the possibility of targeting B cells in certain hematopoietic malignancies.

[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.

B cells in Sjögren's syndrome: indications for disturbed selection and differentiation in ectopic lymphoid tissue

Primary Sjögren's syndrome (pSS) is an autoimmune disorder characterized by specific pathological features. A hallmark of pSS is B-cell hyperactivity as manifested by the production of autoantibodies, hypergammaglobulinemia, formation of ectopic lymphoid structures within the inflamed tissues, and enhanced risk of B-cell lymphoma. Changes in the distribution of peripheral B-cell subsets and differences in post-recombination processes of immunoglobulin variable region (IgV) gene usage are also characteristic features of pSS. Comparison of B cells from the peripheral blood and salivary glands of patients with pSS with regard to their expression of the chemokine receptors CXCR4 and CXCR5, and their migratory capacity towards the corresponding ligands, CXCL12 and CXCL13, provide a mechanism for the prominent accumulation of CXCR4⁺CXCR5⁺ memory B cells in the inflamed glands. Glandular B cells expressing distinct features of IgV light and heavy chain rearrangements, (re)circulating B cells with increased mutations of cμ transcripts in both CD27^- and CD27⁺ memory B-cell subsets, and enhanced frequencies of individual peripheral B cells containing IgV heavy chain transcripts of multiple isotypes indicate disordered selection and incomplete differentiation processes of B cells in the inflamed tissues in pSS. This may possibly be related to a lack of appropriate censoring mechanisms or different B-cell activation pathways within the ectopic lymphoid structures of the inflamed tissues. These findings add to our understanding of the pathogenesis of this autoimmune inflammatory disorder and may result in new therapeutic approaches.