Sustained improvement in rheumatoid arthritis following a protocol designed to deplete B lymphocytes

Rituximab, an anti-cd20 monoclonal antibody: history and mechanism of action

Rituximab, chimeric anti-human CD20, is approved for treatment of B-cell lymphoma in adults. It is being used experimentally in other various immune-related diseases such as immune thrombocytopenic purpura, systemic lupus erythematosus, myasthenia gravis and rheumatoid arthritis. In transplant recipients, it is used for treatment of post-transplant lymphoproliferative disease, to anecdotally reduce pre-formed anti-HLA and anti-ABO antibodies and for the prevention and treatment of acute rejection. This article primarily reviews the science behind rituximab: its history, pharmacokinetics and potential mechanism of action. A need for controlled clinical trials is clearly indicated before the widespread use of this drug in transplant.

Biological therapies directed against cells in autoimmune disease

Among the cells of the immune system involved in the pathogenesis of autoimmune disease, T cells have received the most attention. The central role of these cells in several animal models of autoimmune diseases and in human disease counterparts has provided the rationale for specific therapeutic targeting of T cell subsets, especially CD4 T cells. So far, the applicability of this approach has not been clearly evident in clinical trials, which was also the case when nondepleting "coating" anti-CD4 monoclonal antibodies was used. In the past several years, experimental evidence supporting a major role of B cells in systemic autoimmune disease has grown. This includes the pathogenicity of certain autoantibodies, the potential of B cells to present antigen in the context of MHC Class II and to signal via costimulatory molecules, and to secrete proinflammatory cytokines. In some instances, engagement of the B cell receptor and other surface receptors is sufficient to stimulate B cells to produce antibodies. The depletion of B cells by targeting the surface marker CD20 has been shown to be effective in treating rheumatoid arthritis with a good side effect profile. Series of cases with other systemic autoimmune diseases indicate that this strategy may be effective in these conditions too. The clinical data add weight to the importance of B cells in the pathogenesis of autoimmune diseases.

Self-reactive CD4+ T cells and B cells in the blood in health and autoimmune disease: increased frequency of thyroglobulin-reactive cells in Graves' disease

The mechanisms underlying activation of potentially self-reactive circulating B cells and T cells remain unclear. We measured the uptake of a self-antigen, thyroglobulin, by antigen presenting cells, and the subsequent proliferation of CD4(+) T cells and B cells from healthy controls and patients with autoimmune thyroiditis. In Hashimoto's thyroiditis, B cells bound increased amounts of thyroglobulin in a complement- and autoantibody-dependent manner, and the thyroglobulin-elicited proliferation of CD4(+) T cells and B cells was complement dependent. Increased proportions of Tg-responsive CD4(+) T cells and B cells were found in patients with Graves' disease. Notably, both patient groups and healthy controls exhibited higher proliferative responses to thyroglobulin than to a foreign recall antigen, tetanus toxoid. Our results suggest that self-tolerance can be broken by exposure of circulating lymphocytes to high local concentrations of self-antigen, and that complement plays a role in the maintenance of autoimmune processes, at least in Hashimoto's thyroiditis.

B-cell targeting in rheumatoid arthritis and other autoimmune diseases

B-cell-targeted therapy for autoimmune disease emerged from theoretical proposition to practical reality between 1997 and 1998, with the availability of the B-cell-depleting monoclonal antibody rituximab. Since then, a score of autoantibody-associated disorders have been treated, with most convincing evidence of efficacy seen in subjects with rheumatoid arthritis. Several classes of B-cell-targeted agent are now under investigation. From the outset, a major goal of B-cell targeting has been the re-establishment of some form of immunological tolerance. In some subjects, the observed improvement of disease for years following therapy fuels hope that this goal might ultimately be achievable.

Anticorps monoclonaux dans le traitement de la polyarthrite rhumatoïde : vers une révolution thérapeutique

The progress of immunopathology allowed the development of targeted drugs or biotherapies. Among them, monoclonal antibodies against T or B lymphocytes or against a cytokine are reported. Monoclonal anti-TNF antibodies are a major therapeutic advance because they can stop the clinical, biological and radiographic evolution of rheumatoid arthritis (RA). Monoclonal anti-CD20 lymphocytes give promising results; they are able to induce prolonged remissions. Monoclonal anti-IL6 receptors are currently being evaluated. They are efficacious in adult RA and in Still's disease. Because of the infectious risk linked to these drugs, the ratio benefit/risk must be carefully evaluated before the prescription of a biotherapy.

Antibody isotype-specific engagement of Fcgamma receptors regulates B lymphocyte depletion during CD20 immunotherapy

CD20 monoclonal antibody (mAb) immunotherapy is effective for lymphoma and autoimmune disease. In a mouse model of immunotherapy using mouse anti–mouse CD20 mAbs, the innate monocyte network depletes B cells through immunoglobulin (Ig)G Fc receptor (FcγR)-dependent pathways with a hierarchy of IgG2a/c>IgG1/IgG2b>IgG3. To understand the molecular basis for these CD20 mAb subclass differences, B cell depletion was assessed in mice deficient or blocked for stimulatory FcγRI, FcγRIII, FcγRIV, or FcR common γ chain, or inhibitory FcγRIIB. IgG1 CD20 mAbs induced B cell depletion through preferential, if not exclusive, interactions with low-affinity FcγRIII. IgG2b CD20 mAbs interacted preferentially with intermediate affinity FcγRIV. The potency of IgG2a/c CD20 mAbs resulted from FcγRIV interactions, with potential contributions from high-affinity FcγRI. Regardless, FcγRIV could mediate IgG2a/b/c CD20 mAb–induced depletion in the absence of FcγRI and FcγRIII. In contrast, inhibitory FcγRIIB deficiency significantly increased CD20 mAb–induced B cell depletion by enhancing monocyte function. Although FcγR-dependent pathways regulated B cell depletion from lymphoid tissues, both FcγR-dependent and -independent pathways contributed to mature bone marrow and circulating B cell clearance by CD20 mAbs. Thus, isotype-specific mAb interactions with distinct FcγRs contribute significantly to the effectiveness of CD20 mAbs in vivo, which may have important clinical implications for CD20 and other mAb-based therapies.

Systemic lupus erythematosus—2005 annus mirabilis?

We are about to enter a new era in the treatment of patients with systemic lupus erythematosus (SLE). For the past 40 years hydroxychloroquine sulfate and corticosteroids, together with varying combinations of immunosuppressive drugs, have been the main treatments for SLE. Although effective for many patients, some patients fail to respond to these drugs and even more suffer from major side effects due to the generalized nature of the immunosuppression. In this article we review the remarkable confluence of new therapies ranging from newer immunosuppressive drugs with fewer side effects, such as mycophenolate mofetil, to the more targeted approaches offered by biological agents. These agents have been designed to block molecules such as CD20, CD22 and interleukin-10 that are thought to have an integral part in the development of SLE. This wolf might not yet be about to become extinct but its survival is increasingly under threat!

Novel therapies for rheumatoid arthritis

Recent years have witnessed significant advancements in the therapeutic approach to rheumatoid arthritis. The introduction of biologic agents, in particular inhibitors of tumor necrosis factor (TNF), has ushered a new era in which the goal of therapy has become achieving very low levels of disease activity. Success achieved with the TNF inhibitors has reinvigorated research into targeting other componenets of the dysregulated immune system in RA. A number of approaches, targeting various cytokines, other inflammatory mediators, and populations of immunocompetent cells, seem promising.

Rituximab for refractory Wegener's granulomatosis: report of a prospective, open-label pilot trial

RATIONALE

Standard therapy for Wegener's granulomatosis is fraught with substantial toxicity and not always effective. B lymphocytes have been implicated in the pathogenesis of Wegener's granulomatosis. Their depletion has been proposed as salvage therapy for refractory disease. Earlier encouraging reports are confounded by concomitant immunosuppressive medications and include only limited available biomarker data.

OBJECTIVES

To evaluate the efficacy and safety of rituximab for remission induction in refractory Wegener's granulomatosis.

METHODS

A prospective open-label pilot trial was conducted with 10 patients monitored for 1 yr. Included were patients with active severe antineutrophil cytoplasmic antibody (ANCA)-associated vasculitis, ANCA positivity, and resistance to (or intolerance of) cyclophosphamide. The remission induction regimen consisted of oral prednisone (1 mg/kg/d) and four weekly infusions of rituximab (375 mg/m(2)). Prednisone was tapered and discontinued over 5 mo. Failure to achieve remission, a clinical flare in the absence of B lymphocytes, and inability to complete the glucocorticoid taper were considered treatment failures.

MAIN RESULTS

Three women and seven men (median age, 57 yr; range, 25-72 yr) were enrolled. All had ANCA reacting with proteinase-3. The median activity score at enrollment was 6 (range, 5-10). All patients tolerated rituximab well, achieved swift B-lymphocyte depletion and complete clinical remission (activity score, 0) by 3 mo, and were tapered off glucocorticoids by 6 mo. Five patients were retreated with rituximab alone for recurring/rising ANCA titers according to protocol. One patient experienced a clinical flare after B lymphocyte reconstitution.

CONCLUSION

In this cohort, rituximab was a well-tolerated and effective remission induction agent for severe refractory Wegener's granulomatosis.

Rituximab for rheumatoid arthritis refractory to anti–tumor necrosis factor therapy: Results of a multicenter, randomized, double-blind, placebo-controlled, phase III trial evaluating primary efficacy and safety at twenty-four weeks

OBJECTIVE

To determine the efficacy and safety of treatment with rituximab plus methotrexate (MTX) in patients with active rheumatoid arthritis (RA) who had an inadequate response to anti-tumor necrosis factor (anti-TNF) therapies and to explore the pharmacokinetics and pharmacodynamics of rituximab in this population.

METHODS

We evaluated primary efficacy and safety at 24 weeks in patients enrolled in the Randomized Evaluation of Long-Term Efficacy of Rituximab in RA (REFLEX) Trial, a 2-year, multicenter, randomized, double-blind, placebo-controlled, phase III study of rituximab therapy. Patients with active RA and an inadequate response to 1 or more anti-TNF agents were randomized to receive intravenous rituximab (1 course, consisting of 2 infusions of 1,000 mg each) or placebo, both with background MTX. The primary efficacy end point was a response on the American College of Rheumatology 20% improvement criteria (ACR20) at 24 weeks. Secondary end points were responses on the ACR50 and ACR70 improvement criteria, the Disease Activity Score in 28 joints, and the European League against Rheumatism (EULAR) response criteria at 24 weeks. Additional end points included scores on the Functional Assessment of Chronic Illness Therapy-Fatigue (FACIT-F), Health Assessment Questionnaire (HAQ) Disability Index (DI), and Short Form 36 (SF-36) instruments, as well as Genant-modified Sharp radiographic scores at 24 weeks.

RESULTS

Patients assigned to placebo (n = 209) and rituximab (n = 311) had active, longstanding RA. At week 24, significantly more (P < 0.0001) rituximab-treated patients than placebo-treated patients demonstrated ACR20 (51% versus 18%), ACR50 (27% versus 5%), and ACR70 (12% versus 1%) responses and moderate-to-good EULAR responses (65% versus 22%). All ACR response parameters were significantly improved in rituximab-treated patients, who also had clinically meaningful improvements in fatigue, disability, and health-related quality of life (demonstrated by FACIT-F, HAQ DI, and SF-36 scores, respectively) and showed a trend toward less progression in radiographic end points. Rituximab depleted peripheral CD20+ B cells, but the mean immunoglobulin levels (IgG, IgM, and IgA) remained within normal ranges. Most adverse events occurred with the first rituximab infusion and were of mild-to-moderate severity. The rate of serious infections was 5.2 per 100 patient-years in the rituximab group and 3.7 per 100 patient-years in the placebo group.

CONCLUSION

At 24 weeks, a single course of rituximab with concomitant MTX therapy provided significant and clinically meaningful improvements in disease activity in patients with active, longstanding RA who had an inadequate response to 1 or more anti-TNF therapies.

Anti-HBs-positive liver failure due to hepatitis B virus reactivation induced by rituximab

A 59-year-old man developed acute hepatitis with reactivated hepatitis B virus (HBV) following administration of rituximab (anti-CD20 monoclonal antibody). The patient was diagnosed with malignant lymphoma in 1998, and virus marker testing indicated HBV surface antigen (HBsAg)-negative and anti-HBs antibody (anti-HBs)-positive results when chemotherapy including rituximab was started. Levels of aminotransferases were elevated, and HBsAg results turned positive. Despite therapy for late-onset hepatic failure, the patient died. Rituximab appears likely to have induced HBV reactivation in this case. Anti-viral agents should be administered for both HBsAg-positive and anti-HBs-positive patients who are scheduled to receive rituximab.

Reconstitution of peripheral blood B cells after depletion with rituximab in patients with rheumatoid arthritis

OBJECTIVE

To study the quantitative and phenotypic reconstitution of peripheral blood B cells and its relationship to the dynamics of clinical response in patients with rheumatoid arthritis (RA) following B cell depletion with rituximab.

METHODS

Twenty-four patients with active RA treated with rituximab were studied. Flow cytometry with combinations of monoclonal antibodies to B cell and T cell subsets was used.

RESULTS

The frequency and total number of CD19+ cells in the peripheral blood decreased a mean of 97% for more than 3 months in all but 1 patient following rituximab therapy. All B cell populations were depleted. More than 80% of residual B cells showed a memory or plasma cell precursor phenotype. B cell repopulation occurred a mean of 8 months after treatment and was dependent on the formation of naive B cells, which showed an increased expression of CD38 and CD5. During repopulation, increased numbers of circulating immature B cells, CD19+,IgD+,CD38(high),CD10(low),CD24(high) cells, were identified. Patients who experienced a relapse of RA on return of B cells tended to show repopulation with higher numbers of memory B cells. A small number of T cells and natural killer cells expressed low levels of CD20. These cells were depleted following rituximab therapy and returned to the circulation a mean of 5 months after treatment. No other significant changes were detected in the T cell populations studied.

CONCLUSION

Rituximab induced a profound depletion of all peripheral blood B cell populations in patients with RA. Repopulation occurred mainly with naive mature and immature B cells. Patients whose RA relapsed on return of B cells tended to show repopulation with higher numbers of memory B cells.

Rituximab Treatment of Refractory Rheumatoid Arthritis

OBJECTIVE

To review published literature using rituximab for treatment of refractory rheumatoid arthritis (RA).

DATA SOURCES

An English-language literature search was conducted using MEDLINE (1966–May 2005) and EMBASE (1980–May 2005). References of identified articles were subsequently reviewed for additional data.

DATA SYNTHESIS

Evidence suggests that B lymphocyte depletion in patients suffering from refractory RA may be a key component in the interruption of the disease pathogenesis. Successful depletion of B lymphocytes with rituximab in patients with RA has been reported in case reports, open-label pilot studies, and a randomized, double-blind, placebo-controlled trial.

CONCLUSIONS

Based on the limited published data, rituximab, when used in combination with other agents (ie, cyclophosphamide or methotrexate), appears to be a reasonable treatment option for refractory RA. However, additional controlled trials need to be conducted to further define optimal dosing, response rates, comparative long-term efficacy, and RA treatment algorithm placement of rituximab in this patient population.

Characterization of lymphocyte populations in nonspecific interstitial pneumonia

Study objectives

Nonspecific interstitial pneumonia (NSIP) has been identified as a distinct entity with a more favorable prognosis and better response to immunosuppressive therapies than usual interstitial pneumonia (UIP). However the inflammatory profile of NSIP has not been characterized.

Design

Using immunohistochemistry techniques on open lung biopsy specimens, the infiltrate in NSIP was characterized in terms of T and B cells, and macrophages, and the T cell population further identified as either CD4 (helper) or CD8 (suppressor-cytotoxic) T cells. The extent of Th1 and Th2 cytokine producing cells was determined and compared to specimens from patients with UIP.

Results

In ten NSIP tissue samples 41.4 ± 4% of mononuclear cells expressed CD3, 24.7 ± 1.8% CD4, 19.1 ± 2% CD8, 27.4 ± 3.9% CD20, and 14.3 ± 1.6% had CD68 expression. Mononuclear cells expressed INFγ 21.9 ± 1.9% of the time and IL-4 in 3.0 ± 1%. In contrast, biopsies from eight patients with UIP demonstrated substantially less cellular staining for either cytokine (INFγ; 4.6 ± 1.7% and IL-4; 0.6 ± 0.3%). Significant populations of CD20 positive B-cells were also identified.

Conclusion

The lymphocytic infiltrate in NSIP is characterized by an elevated CD4/CD8 T-cell ratio, and is predominantly of Th1 type, with additional populations rich in B-cells. Such features are consistent with the favorable clinical course observed in patients with NSIP compared to UIP.

Rheumatoid arthritis: an overview of new and emerging therapies

Rheumatoid arthritis (RA) is a chronic, inflammatory, systemic autoimmune disorder characterized by symmetric inflammation of synovial joints leading to progressive erosion of cartilage and bone. The aim of treatment is to mitigate joint destruction, preserve function, and prevent disability. The American College of Rheumatology guidelines for the treatment of RA recommend that newly diagnosed patients with RA begin treatment with disease-modifying antirheumatic drugs (DMARDs) within 3 months of diagnosis. Methotrexate remains the most commonly prescribed DMARD and is the standard by which recent new and emerging therapies are measured. Increasing knowledge regarding the immunologic basis of RA and advances in biotechnology have resulted in new, targeted biological therapies against proinflammatory cytokines that have dramatically changed the treatment paradigm and outcomes of patients with RA. This article reviews the pharmacological rationale underlying RA therapy, with a focus on currently available biological therapies and new therapies in development.

Population pharmacokinetics of rituximab (anti-CD20 monoclonal antibody) in rheumatoid arthritis patients during a phase II clinical trial

Rituximab is a B cell-depleting anti-CD20 chimeric IgGkappa monoclonal antibody being investigated for the treatment of rheumatoid arthritis. The purpose of this study was to develop a population pharmacokinetic model in rheumatoid arthritis patients. In addition, the final pharmacokinetic model was used to assess the variability in drug exposure (AUC0-infinity) for fixed versus body surface area-based dosing. A total of 102 patients were included in this population pharmacokinetic analysis. A 2-compartment pharmacokinetic model described the data reasonably well. Body surface area and gender were the most significant covariates for both CL and Vc. Body surface area alone only explained about 19.7% of the total interindividual variability of CL. In a simulation study, body surface area-based dosing normalized drug exposure over a wide range of body surface area but did not seem to improve the predictability of rituximab AUC0-infinity in rheumatoid arthritis patients. Therefore, no rationale for body surface area-based dosing for rituximab in rheumatoid arthritis patients was found.

Emerging biologic drugs for the treatment of rheumatoid arthritis

This article reviews the role of emerging biologic drugs for the treatment of rheumatoid arthritis (RA). Besides anti-tumor necrosis factor (TNF)-alpha and anti-interleukin (IL)-1 agents (Infliximab, Adalimumab, Etanercept and Anakinra) whose clinical efficacy is now established, new drugs have been proposed for the therapy of rheumatoid arthritis patients not responding to conventional treatments. These approaches include the blockade of B-cell activity with anti-CD20 monoclonal antibody (Rituximab) and the inhibition of T-cell activation with fusion protein CTLA4Ig. Moreover, promising results have been obtained in animal models utilizing suppressors of cytokine signaling (SOCS) and dominant-negative TNF variants to inactivate TNF signaling.

Rheumatoid Factors: Good or Bad for You?

BACKGROUND

Rheumatoid factors (RFs) are autoantibodies associated with rheumatoid arthritis. They can be detected in normal individuals, although transiently. This dichotomy has led to questions about the origins and types of RFs. Recently it has been shown that B cells that produce RFs only do so when activated by two signals, one from engagement of the B-cell receptor and the other from recognition of a pathogen-associated molecular pattern through a Toll-like receptor (TLR). These autoantibodies thus link the innate and acquired immune responses.

OBJECTIVE

Through a review of the literature, an examination of the current knowledge of RF induction is presented. The focus is on a discussion of a beneficial or detrimental role for RFs in normal individuals and in those with chronic disease.

RESULTS

What makes RF 'good' in some cases and 'bad' in others may reflect the type of RF produced. Low-affinity polyreactive IgM RFs are probably beneficial as they aid in the clearance of immune complexes that are more efficiently cleared, and the RF B cell can act as an antigen-presenting cell and stimulate host defense. However, large amounts of high-affinity RFs found in patients with chronic disease may be harmful by participation in a vicious cycle of autoantibody production by stimulation of self lymphocytes, and/or deposition in blood vessels thus causing vasculitis.

CONCLUSIONS

Whether RFs are beneficial or detrimental depends on the context in which they are expressed, the type and amount of RF produced, whether the response is perpetuated by TLR ligation and whether other cells are stimulated either directly or indirectly by RF-positive B cells.

Immunotherapy using unconjugated CD19 monoclonal antibodies in animal models for B lymphocyte malignancies and autoimmune disease

Immunotherapy with unconjugated CD20 monoclonal antibodies has proven effective for treating non-Hodgkin's lymphoma and autoimmune disease. CD20 immunotherapy depletes mature B cells but does not effectively deplete pre-B or immature B cells, some B cell subpopulations, antibody-producing cells, or their malignant counterparts. Because CD19 is expressed earlier during B cell development, a therapeutic strategy for the treatment of early lymphoblastic leukemias/lymphomas was developed by using CD19-specific monoclonal antibodies in a transgenic mouse expressing human CD19. Pre-B cells and their malignant counterparts were depleted as well as antibody- and autoantibody-producing cells. These results demonstrate clinical utility for the treatment of diverse B cell malignancies, autoimmune disease, and humoral transplant rejection.

Rituximab in the Treatment of Refractory Dermatomyositis

Dermatomyositis is an inflammatory myopathy characterized by muscle weakness and inflammation. In contrast to polymyositis and inclusion body myositis, humoral immune mechanisms appear to contribute to the pathogenesis of dermatomyositis. A 56-year-old man with dermatomyositis resistant to conventional therapies was treated with 6 weekly infusions of the anti-CD-20 monoclonal antibody, rituximab, at a dosage of 100 mg/m in addition to other agents. The patient demonstrated a remarkable clinical response as indicated by an increase in muscle strength and a decline in creatine kinase enzymes. B-cell depletion therapy with rituximab used alone or in combination with other immunosuppressive therapies may be a viable option in patients with dermatomyositis as well as other autoimmune diseases refractory to current therapies.

B-cell depletion in the treatment of patients with systemic lupus erythematosus: a longitudinal analysis of 24 patients

OBJECTIVES

To assess the clinical and basic serological consequences of B-cell depletion with rituximab in the treatment of patients with systemic lupus erythematosus (SLE) who have failed conventional immunosuppression.

METHODS

An open study of 24 patients with severe SLE followed for a minimum of 3 months is reported. In the majority of patients (19 out of 24), 6 months follow-up data are described. Disease activity in these patients was assessed every 1-2 months using the British Isles Lupus Assessment Group (BILAG) system and estimates of anti-double-stranded DNA antibodies and serum C3 levels. During the follow-up period, significant side-effects were sought and the reduction in oral prednisolone was recorded. It was our general practice to stop concomitant immunosuppression (e.g. azathioprine, mycophenolate) when B-cell depletion was given (in most cases in the form of two 1 g intravenous infusions of rituximab 2 weeks apart accompanied by two 750 mg intravenous cyclophosphamide infusions and two methylprednisolone infusions of 250 mg each).

RESULTS

Twenty-two patients were female and two male. At the time of B-cell depletion, the mean age was 28.9 yr (range 17-49) and the mean disease duration was 7.9 yr (range 1-18). The global BILAG score (P < 0.00001), serum C3 (P < 0.0005) and double-stranded DNA binding (P < 0.002) all improved from the time of B-cell depletion to 6 months after this treatment. Only one patient failed to achieve B-lymphocyte depletion in the peripheral blood. The period of B-lymphocyte depletion ranged from 3 to 8 months except for one patient who remains depleted at more than 4 yr. Analysis of the regular BILAG assessments showed that improvements occurred in each of the eight organs or systems. The mean daily prednisolone dose fell from 13.8 mg (s.d. 11.3) to 10 mg (s.d. 3.1).

CONCLUSION

In this open study of patients who had failed conventional immunosuppressive therapy, considerable utility in the use of B-cell depletion has been demonstrated. Our data provide strong support for the performance of a full double-blind control trial.

[Do B cells play an important role in the pathogenesis of rheumatoid arthritis?]

The role of B cells for the pathogenesis of rheumatoid arthritis (RA) has been debated for a long time. Here we show that chronic inflammation in the affected joints leads to the development of ectopic germinal centers. A micro-environment is established which supports B cell activation and differentiation. Plasma cells may develop which secrete autoantibodies of high affinity directly into the synovial tissue. Antigen/antibody complex formation, the activation of the complement cascade and the stimulation of macrophages may contribute to the destruction of joints. Furthermore, B cells are efficient antigen presenting cells. They seem to play a pivotal role in the activation of synovial T cells and the induction of cytokine secretion. The success of B cell depletion therapy by using the monoclonal antibody Rituximab further emphasized the importance of B cells in the pathogenesis of RA.

Emerging biologic therapies in rheumatoid arthritis: cell targets and cytokines

PURPOSE OF REVIEW

Biologic therapy for rheumatoid arthritis targets specific molecules, both cell-bound and soluble, that mediate and sustain the clinical manifestations of this complex disease. The aim of all the therapeutic strategies is to achieve complete and sustained suppression of inflammation, in the absence of unacceptable short-term and long-term toxicity. Despite the success of the currently available biologic inhibitors of tumor necrosis factor-alpha and interleukin-1, a substantial number of rheumatoid arthritis patients are refractory to these treatments. The purpose of this review is to highlight recent clinical trials of emerging biologic treatments for rheumatoid arthritis.

RECENT FINDINGS

T cell co-stimulation has been targeted by the use of cytotoxic T lymphocyte-associated antigen 4-Ig, a genetically engineered fusion protein. In a large controlled clinical trial, this nondepleting approach was shown to achieve impressive clinical responses, without evidence of short-term toxicity. Likewise, rituximab, a B cell-deleting monoclonal antibody, was shown in a controlled clinical trial to have sustained benefit in patients with refractory rheumatoid arthritis. Despite profound B cell depletion with rituximab, there was an acceptable safety profile with this treatment. MRA, a monoclonal antibody that inhibits interleukin-6 by binding to its receptor interleukin-6R, demonstrated clinically significant improvement in rheumatoid arthritis and a particularly impressive reduction in the acute phase response.

SUMMARY

The response of rheumatoid arthritis to a wide spectrum of therapeutic strategies attests to the complexity and heterogeneity of the disease and provides further impetus for studies that use these therapies to enhance our understanding of disease pathogenesis.

Tolerability and safety of rituximab (MabThera)

Rituximab, a human/mouse chimeric anti-CD20 antibody, has become part of standard therapy for patients with CD20-expressing B-cell lymphoma, and is currently under investigation for other indications including autoimmune diseases, in particular rheumatoid arthritis (RA). Its characteristic tolerability profile was established soon after clinical testing began and compares favourably with chemotherapy. The majority of patients experience mild to moderate infusion-related reactions (IRRs) during the first administration of rituximab, but the incidence decreases markedly with subsequent infusions. Current data suggest that the type of adverse events in patients with RA are similar to those in lymphoma, but that adverse events related to the rituximab infusions are less severe and less frequent. Rituximab induces a rapid depletion of normal CD20-expressing B-cells in the peripheral blood, and levels remain low or undetectable for 2-6 months before returning to pretreatment levels, generally within 12 months. Serum immunoglobulin levels remain largely stable, although a reduction in IgM has been described. T-cells are unaffected by rituximab and consequently opportunistic infections rarely occur in association with rituximab therapy. When used in combination with a variety of chemotherapeutic regimens, rituximab does not add to the toxicity of chemotherapy, with the exception of a higher rate of neutropenia. However, this does not translate into a higher infection rate. Over 540,000 patients worldwide have now received rituximab and serious adverse reactions have occurred in a small minority of patients, but for the great majority of patients, rituximab is safe and well tolerated.

B cells as a therapeutic target in autoimmune diseases

Historically, the pathogenic role of B cells in autoimmune disease has been attributed to the formation of autoantibodies which, as soluble immunoglobulins or immunocomplexes, can trigger cellular damage and initiate the inflammatory cascade. Recent results from clinical trials applying B cell-directed therapeutics in rheumatoid arthritis and systemic lupus erythematosus have challenged such traditional views and encouraged novel ideas about the disease involvement of B cells. Suppression of disease activity, often disconnected from effects on autoantibody titers, has supported the notion that B cells may promote autoimmune disease by serving as antigen-presenting cells that sustain T cell activation. Likewise, B cells have been implicated in supporting the process of ectopic lymphoid neogenesis, a mechanism that stabilises pathogenic immune responses in target tissues and thus contributes to disease chronicity. As a general rule, clinical effects of B cell-directed therapeutics have often been unanticipated and unpredicted by experimental models, emphasis-ing the need to explore and verify disease principles in the patient.

Do We Need New Treatment That Goes beyond Tumor Necrosis Factor Blockers for Rheumatoid Arthritis?

Rheumatoid arthritis (RA) has a prevalence of approximately 1%, making it the most common inflammatory rheumatic disease. The outcome for RA patients has significantly improved during recent years. Factors include the introduction of new therapies such as tumor necrosis factor (TNF)-blocking agents and new treatment strategies, especially early and aggressive therapy, including combinations of several disease-modifying antirheumatic drugs (DMARDs). However, only 60-70% of RA patients respond to treatment with a TNF-blocking agent. In addition, most of these patients show only a partial response according to ACR20 criteria. Therefore, to ameliorate painful joint inflammation and prevent disability in RA patients, new treatment principles and more intelligent combination therapies are urgently needed. Interestingly, the strategy of switching patients who no longer respond to one of the TNF blockers to another has often turned out to be effective. Areas of ongoing research include combining TNF-blocking agents with DMARDs other than methotrexate. Also, several new biologics are being tested in clinical trials that promise to soon enhance the therapeutic armamentarium to fight RA. These biologics' mechanisms of action feature blockade of T cell costimulation by a CTLA4Ig fusion protein (abatacept); blockade of interleukin (IL)-6 signaling with an antibody to the IL-6 receptor (MRA); neutralizing IL-15 by a monoclonal antibody; and targeting B cells with an anti-CD20 antibody (rituximab). Other therapeutic approaches, such as blockade of chemokine receptors, adhesion molecules, complement components, and transcription factors regulating the inflammatory response, appear promising; however, they still need careful evaluation in placebo-controlled clinical studies.

New therapies for rheumatoid arthritis

Rheumatoid arthritis (RA) is a chronic, systemic inflammatory disease, which continues to cause significant morbidity in affected persons. In the past few years, a number of new exciting therapeutic options have become available. These reflect the application of knowledge obtained from advancements in understanding of disease pathogenesis and underlying molecular mechanisms. A number of these therapies are outlined in the following review, including the various biological modifiers, in particular, anti-tumour necrosis factor-alpha agents and interleukin-1 (IL-1) receptor antagonists, which have been developed in recognition of the role of pro-inflammatory cytokines in RA. Also notable, is the current interest centring on the development and trials with B cell depletion therapies, specifically rituximab, in patients with RA. This demonstrates acknowledgment for a more significant role for B cells in the aetiology of RA, in contrast to the long held view that RA was a predominantly T cell mediated disease. To evaluate this therapeutic option for RA, salient features from recent rituximab trials have been collated. Finally, a selection of other therapeutic alternatives, including anti-IL-6 receptor monoclonal antibody and tacrolimus, and newer anti-rheumatic therapies presently in development are summarized.

New therapies for systemic lupus erythematosus

In the past 40 years, prognosis for patients with systemic lupus erythematosus (SLE) has improved, with 10-year survival now approximately 90%. This is due probably to a combination of earlier disease diagnosis and diagnosis of milder disease, due in part to availability of multiple serological tests for SLE, use of steroids and other immunosuppressive agents, and availability of renal dialysis and transplantation. Despite this, however, the potential for significant morbidity and mortality remains in the group of patients with partially responsive or treatment resistant disease. More recently, advancements in the understanding of molecular mechanisms involved in the pathogenesis of SLE have translated to the development of novel therapies, offering possible alternatives to this patient cohort. Discussion of these pharmacological options and ongoing research forms the basis of this review.

Rheumatoid arthritis: non-tumor necrosis factor targets

PURPOSE OF REVIEW

The treatment of rheumatoid arthritis has been revolutionised in recent years with the advent of biologic treatments. The purpose of this review is to outline new treatments that target the inflammatory pathway in rheumatoid arthritis other than tumor necrosis factor-alpha.

RECENT FINDINGS

As the use of anti-tumor necrosis factor-alpha treatment has become more widespread, the number of patients in whom this treatment is unsuccessful has also accumulated. Contraindications such as infection and cardiac failure further add to the number of patients who need alternative treatment. A better understanding of the inflammatory pathway in rheumatoid arthritis has led to interest in other therapeutic targets. Promising treatments such as interleukin-6 antagonists (MRA), CTLA4Ig (abatacept), and anti-B cell therapy (rituximab) have already been tested in randomized controlled trials over the past year. Other cytokines have been identified and have been shown to be of benefit in animal models, including interleukin-15, interleukin-17, and interleukin-18, and clinical trials of these agents are currently under way.

SUMMARY

For patients with rheumatoid arthritis that does not respond to anti-tumor necrosis factor-alpha treatment, the promising alternatives MRA, abatacept, and rituximab have been tested. It is hoped that these agents will become available shortly.

Antigen-specific B cells are required as APCs and autoantibody-producing cells for induction of severe autoimmune arthritis

B cells play an important role in rheumatoid arthritis, but whether they are required as autoantibody-producing cells as well as APCs has not been determined. We assessed B cell autoantibody and APC functions in a murine model of autoimmune arthritis, proteoglycan (PG)-induced arthritis, using both B cell-deficient mice and Ig-deficient mice (mIgM) mice that express an H chain transgene encoding for membrane-bound, but not secreted, IgM. The IgH transgene, when paired with endogenous lambda L chain, recognizes the hapten 4-hydroxy-3-nitro-phenyl acetyl and is expressed on 1-4% of B cells. B cell-deficient and mIgM mice do not develop arthritis after immunization with PG. In adoptive transfer of PG-induced arthritis into SCID mice, T cells from mIgM mice immunized with PG were unable to transfer disease even when B cells from PG-immunized wild-type mice were provided, suggesting that the T cells were not adequately primed and that Ag-specific B cells may be required. In fact, when PG was directly targeted to the B cell Ig receptor through a conjugate of 4-hydroxy-3-nitrophenyl acetyl-PG, T cells in mIgM mice were activated and competent to transfer arthritis. Such T cells caused mild arthritis in the absence of autoantibody, demonstrating a direct pathogenic role for T cells activated by Ag-specific B cells. Transfer of arthritic serum alone induced only mild and transient arthritis. However, both autoreactive T cells and autoantibody are required to cause severe arthritis, indicating that both B cell-mediated effector pathways contribute synergistically to autoimmune disease.

What to do with TNF failures

The introduction of TNF inhibitors into the clinic for the treatment of patients with rheumatoid arthritis and other systemic inflammatory conditions has revolutionised the approach to these diseases. Despite the substantial efficacy of these agents, a subset of patients either does not respond or has a suboptimal clinical response. Defining what constitutes 'failure' of this type of therapy is important in both clinical research and practice. For patients who fail to respond to TNF inhibitors, a number of promising avenues targeting other aspects of the immune system are under study, and may be brought to the clinic in the near future.

The plasminogen activator/plasmin system is essential for development of the joint inflammatory phase of collagen type II-induced arthritis

The plasminogen activator (PA) system has been proposed to have important roles in rheumatoid arthritis. Here we have used the autoimmune collagen type II (CII)-induced arthritis (CIA) model and mice deficient for urokinase-type PA (uPA) or plasminogen to investigate the role of the PA system for development of arthritis. Our data revealed that uPA-deficient mice have a lower severity and incidence of CIA than wild-type mice. Furthermore, although >80% of wild-type control mice developed CIA, we found that none of the 50 plasminogen-deficient littermates that were tested developed CIA within a 40-day period. Antibody generation after CII immunization as well as the binding of labeled anti-CII antibodies to the surface of cartilage were similar in wild-type and plasminogen-deficient mice. No sign of inflammation was seen when plasminogen-deficient mice were injected with a mixture of monoclonal antibodies against CII. However, after daily injections of human plasminogen, these mice developed arthritis within 5 days. Our finding that infiltration of inflammatory cells into the synovial joints was impaired in plasminogen-deficient mice suggests that uPA and plasminogen are important mediators of joint inflammation. Active plasmin is therefore essential for the induction of pathological inflammatory joint destruction in CIA.

Remission of proliferative lupus nephritis following B cell depletion therapy is preceded by down-regulation of the T cell costimulatory molecule CD40 ligand: an open-label trial

OBJECTIVE

Autoreactive B cells play a key role in tissue injury in systemic autoimmune disease, and therefore a treatment resulting in B cell depletion could have benefit. This open-label study was undertaken to evaluate the efficacy of the anti-CD20 monoclonal antibody rituximab in the treatment of lupus nephritis.

METHODS

Lupus patients with active proliferative nephritis (4 with focal disease and 6 with diffuse disease) received rituximab (4 weekly infusions of 375 mg/m(2)) combined with oral prednisolone. Clinical, laboratory, and immunologic responses, including peripheral lymphocyte subsets measured by flow cytometry, were prospectively assessed at monthly intervals for 12 months. Complete remission of nephritis was defined as normal serum creatinine and albumin levels, inactive urine sediment, and 24-hour urinary protein <500 mg. Partial remission was defined as >50% improvement in all renal parameters that were abnormal at baseline.

RESULTS

B cell depletion lasted from 1 month to 7 months and was well tolerated. Partial remission was achieved in 8 of 10 patients within a median of 2 months (range 1-4 months); in 5 of them, complete remission was subsequently established (at a median of 3 months from baseline), and it was sustained at 12 months in 4. As early as 1 month from baseline, the expression of the costimulatory molecule CD40 ligand on CD4+ T cells was decreased by 4-fold, and it was almost blocked when partial remission was clinically evident. The expression of T cell activation markers CD69 and HLA-DR was significantly decreased at time points when partial remission was observed, and was further decreased during complete remission. In contrast, in patients who did not exhibit a response or when relapse was detected in patients in whom an initial remission had been achieved, such decreases were not prominent. Serum concentrations of double-stranded DNA autoantibodies were decreased in all patients, regardless of clinical outcome.

CONCLUSION

Following B cell depletion, clinical remission of lupus nephritis is associated with a decrease in T helper cell activation, suggesting an additional role for B cells, independent of autoantibody production, in promoting disease. A controlled trial to confirm these promising clinical results is warranted.

Rheumatoid arthritis: developing pharmacological therapies

Rheumatoid arthritis (RA) is a chronic inflammatory disease that often results in significant morbidity, mortality and disability. Over the past 20 years a better understanding of the pathogenesis of RA has led to the development of new approaches to disease treatment. The recent introduction of biological agents has changed the treatment paradigm for RA. The success of early biological therapies including TNF-alpha and IL-1 antagonists has spurred interest in the development of additional novel targets in the treatment of RA. Biological therapies approved for other indications, such as rituximab, are now being evaluated for the treatment of rheumatic diseases such as RA. A co-stimulatory blocker, abatacept, is also in pivotal Phase III trials. This article reviews evolving pharmacological therapies in RA with an emphasis on the newer approaches to treatment including inhibition of cognate signalling and T- and B-cell targets.

[Rituximab: a original biotherapy in auto-immune disorders]

SUBJECT

After several decades of hegemony of the T lymphocyte, recent work has suggested the importance of the B lymphocyte in auto-immune diseases. As a consequence, there has emerged over the last few years the idea of using anti-B lymphocyte therapy, in particular rituximab (a chimeric anti-CD20 monoclonal antibody).

CURRENT TOPICS AND IMPORTANT RESULTS

This review addresses various current topics: a) the role of B lymphocytes in auto-immune diseases, notably their capacity to be antigen presenting cells and to be activated by original systems like Blys/Baff; b) the mechanism of action of rituximab (apoptosis, complement-dependent cytotoxicity and antibody-dependent cell cytotoxicity) and the phenomena explaining failures and cases escaping treatment, in particular among lymphoproliferations; c) The results include efficacy and tolerance data for the principal auto-immune affections. Among these, the most promising indications would seem to be for rheumatoid polyarthritis and systemic lupus erythematosis, although some preliminary open studies point to an effect in Goujerot-Sjögren's syndrome, neuropathies, auto-immune cytopenia, idiopathic thrombocytopenic purpura, cryoagglutinins, blistering cutaneous affections...

PERSPECTIVES AND PROJECTS

Controlled studies will be required to determine the true efficacy and tolerance of this molecule, as it is imperative to validate these new immunotherapeutic strategies, above all when they concern innovative and expensive therapy. Nevertheless, these different observations arouse great hopes and at the same time exciting questions, notably as to the role of B lymphocytes in auto-immune diseases.

Reduction of soluble complement receptor 2/CD21 in systemic lupus erythomatosus and Sjogren's syndrome but not juvenile arthritis

A soluble form of the complement receptor CD21 (sCD21) is shed from the lymphocyte surface. The amount of sCD21 in serum may modulate immunity as sCD21 levels are correlated with several clinical conditions. We report here the serum levels of sCD21 in juvenile arthritis (JA), systemic lupus erythematosus (SLE) and Sjogren's syndrome (SS). Using enzyme-linked immunosorbent assay, we determined sCD21 levels in SLE, SS and JA patients. Mann-Whitney test for nonparametric two-tail P value was performed to obtain statistical significance. Cytometrical analysis of synovial fluid leucocytes of JA patients was done on a FACSsort. While sCD21 levels in SLE and SS are reduced to levels previously found in rheumatoid arthritis (RA), JA sCD21 levels were normal. sCD21 levels did not correlate with clinical parameters and immunophenotype of synovial cells. CD4 T cells in the synovium were almost all of the CD45RO memory type and 13 of 40 patients displayed synovial expansion of gammadeltaT cells. CD21 shedding in JA differs from RA/SS/SLE. JA sCD21 levels in synovial fluid are always lower compared to blood levels of the same patients. Analysis of JA synovial T cells indicates a T-cell driven response.

Does B cell depletion have a role to play in the treatment of systemic lupus erythematosus?

B cell dysfunction and pathogenic autoantibody formation are thought to be critical in the pathogenesis of systemic lupus erythematosus (SLE). In this review we will summarize the results of attempts to utilize B cell depletion, based on the use of a chimeric monoclonal antibody (MAb) specific for human CD20, rituximab, for the treatment of patients with SLE.

CD22: A Multifunctional Receptor That Regulates B Lymphocyte Survival and Signal Transduction

Recent advances in the study of CD22 indicate a complex role for this transmembrane glycoprotein member of the immunoglobulin superfamily in the regulation of B lymphocyte survival and proliferation. CD22 has been previously recognized as a potential lectin-like adhesion molecule that binds alpha2,6-linked sialic acid-bearing ligands and as an important regulator of B-cell antigen receptor (BCR) signaling. However, genetic studies in mice reveal that some CD22 functions are regulated by ligand binding, whereas other functions are ligand-independent and may only require expression of an intact CD22 cytoplasmic domain at the B-cell surface. Until recently, most of the functional activity of CD22 has been widely attributed to CD22's ability to recruit potent intracellular phosphatases and limit the intensity of BCR-generated signals. However, a more complex role for CD22 has recently emerged, including a central role in a novel regulatory loop controlling the CD19/CD21-Src-family protein tyrosine kinase (PTK) amplification pathway that regulates basal signaling thresholds and intensifies Src-family kinase activation after BCR ligation. CD22 is also central to the regulation of peripheral B-cell homeostasis and survival, the promotion of BCR-induced cell cycle progression, and is a potent regulator of CD40 signaling. Herein we discuss our current understanding of how CD22 governs these complex and overlapping processes, how alterations in these tightly controlled regulatory activities may influence autoimmune disease, and the current and future applications of CD22-directed therapies in oncology and autoimmunity.

B lymphocyte

Recent studies have revealed that B cells play a critical role in autoimmunity and disease expression through various functions, including autoantibody production, cytokine secretion, antigen presentation, and co-stimulatory effect. Selective targeting of B cells has been recently achieved using a chimeric monoclonal antibody against CD20 (Rituximab). Significant clinical efficacy has been demonstrated in several autoimmune diseases including rheumatoid arthritis and systemic lupus erythematosus by the infusion of this antibody. Rituxumab significantly improves the symptoms during the long period of complete B cell depletion. Understanding the dynamics of B cell involvement in autoimmune diseases will be crucial to the development of B cell-targeted strategies. Conversely, the findings derived from studies of anti-B cell therapy provide us a lot of important clues to clarify the pathogenesis of autoimmune diseases. This review focuses on recent data demonstrating the roles of B cells in autoimmune diseases as well as the current studies concerning the treatment of autoimmune diseases by Rituximab.

Contrasting roles of plasminogen deficiency in different rheumatoid arthritis models

OBJECTIVE

To investigate the contrasting roles of plasminogen deficiency between models of collagen-induced arthritis (CIA) and antigen-induced arthritis (AIA).

METHODS

We developed a new animal model of arthritis, which we have called local injection-induced arthritis (LIA). In this model, we replaced methylated bovine serum albumin, which is normally used as an immunogen and is injected intraarticularly into the knee joint, with type II collagen (CII) to induce AIA. The severity of CIA, LIA, and AIA in wild-type and plasminogen-deficient mice was evaluated by clinical scoring or histologic grading. Necrosis was determined by histology and immunohistochemistry.

RESULTS

After CII immunization alone, wild-type mice developed arthritis in most of the paws as well as in the knee joints, whereas plasminogen-deficient mice were totally resistant to the disease. Local knee injections of CII or saline slightly enhanced the severity of the knee arthritis in wild-type mice during a 60-day experimental period. Unexpectedly, the plasminogen-deficient mice also developed arthritis in joints that were injected with CII or saline. However, the arthritis was milder than that in their wild-type littermates. Sustained tissue necrosis was found only in the plasminogen-deficient mice after the local injection.

CONCLUSION

Our data show that both the antigen and the joint trauma caused by the local injection are critical to explaining the contrasting roles of plasminogen deficiency in CIA and AIA. This further indicates that CIA and AIA have distinct pathogenic mechanisms. The data also suggest that plasmin may be required for the induction of these arthritis models that are critically dependent on complement activation.

B lymphocyte depletion therapy in children with refractory systemic lupus erythematosus

OBJECTIVE

To determine the safety and efficacy of B lymphocyte depletion therapy in patients with refractory childhood-onset systemic lupus erythematosus (SLE).

METHODS

Seven patients (4 of whom were female), ages 7.7-16.1 years (median 14.8 years) with active SLE that was resistant to standard immunosuppressive agents were treated with B cell depletion. During a 2-week period, patients received two 750-mg/m2 intravenous infusions of rituximab, with intravenous cyclophosphamide (if they had not previously received this treatment) and high-dose oral corticosteroids.

RESULTS

Patients were followed up for a median of 1.0 years, and no serious adverse effects were noted. In all patients, the clinical symptoms and signs for which rituximab therapy was initiated were improved. There was significant improvement in the British Isles Lupus Assessment Group global scores, from a median score of 22 (range 14-37) at baseline to a median score of 6 (range 4-11) at followup (P = 0.002). In 2 patients with severe multisystem and life-threatening disease unresponsive to standard therapy (including plasma exchange), renal replacement therapy was successfully withdrawn following B cell depletion therapy. These 2 patients have subsequently shown further significant improvement in renal function and proteinuria.

CONCLUSION

This open-label study demonstrates that targeted B cell depletion therapy can be a safe and efficacious addition to therapy with standard immunosuppressive agents in patients with refractory childhood SLE. The drugs used for treatment of childhood SLE need to be the most effective, least toxic agents, allowing normal growth and development.

Rituximab improves peripheral B cell abnormalities in human systemic lupus erythematosus

OBJECTIVE

B lymphocyte depletion has recently emerged as a promising approach to the treatment of systemic lupus erythematosus (SLE). As part of a phase I/II dose-ranging trial of rituximab in the treatment of SLE, we evaluated the fate of discrete B cell subsets in the setting of selective depletion by anti-CD20 monoclonal antibody and during the B cell recovery phase.

METHODS

B cell depletion and phenotype were examined by flow cytometry of peripheral blood mononuclear cells for CD19, CD20, CD27, IgD, and CD38 expression. Changes in autoreactive B lymphocytes and plasma cells were assessed by determination of serum autoantibody levels (anti-double-stranded DNA and VH4.34) and by direct monitoring of a unique autoreactive B cell population bearing surface antibodies whose heavy chain is encoded by the VH4.34 gene segment.

RESULTS

Compared with normal controls, SLE patients displayed several abnormalities in peripheral B cell homeostasis at baseline, including naive lymphopenia, expansion of a CD27-,IgD- (double negative) population, and expansion of circulating plasmablasts. Remarkably, these abnormalities resolved after effective B cell depletion with rituximab and immune reconstitution. The frequency of autoreactive VH4.34 memory B cells also decreased 1 year posttreatment, despite the presence of low levels of residual memory B cells at the point of maximal B cell depletion and persistently elevated serum autoantibody titers in most patients.

CONCLUSION

This study is the first to show evidence that in SLE, specific B cell depletion therapy with rituximab dramatically improves abnormalities in B cell homeostasis and tolerance that are characteristic of this disease. The persistence of elevated autoantibody titers may reflect the presence of low levels of residual autoreactive memory B cells and/or long-lived autoreactive plasma cells.

Emerging approaches for the therapy of autoimmune and chronic inflammatory disease

Progress in defining protein and gene signatures that characterize autoimmune-mediated inflammatory diseases has uncovered a large number of potential therapeutic targets. Preclinical data from rodent models can be generated rapidly, as can data from the genetic crosses of gene-deficient mice on autoimmune-susceptible backgrounds. But humans are not the same as mice, and however robust preclinical data might appear, therapeutic intervention in patients with autoimmune disease remains the definitive experiment. Several studies published in the past year have tested paradigms of autoimmune disease in clinical trials. Recent therapeutic approaches for targeting B-cell subsets and co-stimulatory pathways are described here in detail. It is our belief that the future of immunotherapy in the clinic will depend to some extent upon the availability of biomarkers for defining biological signatures of immune function in vivo.

From the bench to the bedside: ways to improve rituximab efficacy

Rituximab (MabThera, Rituxan) is a chimeric IgG1 monoclonal antibody that specifically targets the CD20 surface antigen expressed on normal and neoplastic B-lymphoid cells. Rituximab is currently used in the treatment of both follicular and aggressive B-cell non-Hodgkin lymphomas. Despite its demonstrated clinical effectiveness, its in vivo mechanisms of action remain unknown and could differ by subtype of lymphoma. Rituximab has been shown to induce apoptosis, complement-mediated lysis, and antibody-dependent cellular cytotoxicity in vitro, and some evidence points toward an involvement of these mechanisms in vivo. Rituximab also has a delayed therapeutic effect as well as a potential “vaccinal” effect. Here, we review the current understanding of the mechanism of action of rituximab and discuss approaches that could increase its clinical activity. A better understanding of how rituximab acts in vivo should make it possible to develop new and more effective therapeutic strategies. (Blood. 2004;104:2635-2642)

Emerging biological therapies in rheumatoid arthritis

The introduction of TNFalpha inhibitors has radically changed the management of patients with refractory rheumatoid arthritis (RA) or spondyloarthropathy. However, among patients with RA unresponsive to methotrexate, only two-thirds respond to TNFalpha inhibitors. Fortunately, more than 5 years after infliximab was introduced on the market, preliminary evidence that emerging biological agents are effective is beginning to accumulate, generating new hope for patients who fail to respond to TNFalpha inhibitors. These novel biological therapies grew out of original pathophysiological hypotheses, a fact that vividly illustrates the importance of basic pathophysiological research for developing new medications. This review provides detailed information on three biological therapies whose efficacy in RA was demonstrated in recently published randomized placebo-controlled trials: a monoclonal antibody to the IL-6 receptor (MRA), CTLA4-Ig (abatacept), and a monoclonal B-cell-specific antibody to CD20 (rituximab). Good risk/benefit ratios seem to be achieved with MRA alone or with abatacept or rituximab combined with methotrexate. However, as yet, no radiographic data are available for these treatments. One of the challenges for the future is to identify ingenious combinations of biological therapies capable of improving the quality and duration of responses without exacerbating side effects.