Efficacy and Safety of Belimumab in Patients with Rheumatoid Arthritis: A Phase II, Randomized, Double-blind, Placebo-controlled, Dose-ranging Study

The role of BAFF in the progression of rheumatoid arthritis

Rheumatoid arthritis (RA) is a common autoimmune disease that is marked by a systemic inflammatory reaction and joint erosions. Elevated levels of B cell activating factor (BAFF) have been detected in the serum and synovial fluid of RA patients. Moreover, the levels of BAFF increase in cases of autoimmune disease and are correlated with the level of disease activity. As an innate cytokine mediator, BAFF affects the immune response of the synovial microenvironment. In this review, we consider recent observations of BAFF and its receptors in RA progression, as well as the effects of BAFF on the cell-cell interactions network. We also summarize the clinical development of BAFF antagonists for the treatment of RA.

Rheumatoid arthritis therapy reappraisal: strategies, opportunities and challenges

Rheumatoid arthritis (RA) is considered a chronic disease that cannot be cured. Biologic agents have enabled good therapeutic successes; however, the response to biologic therapy depends on treatment history and, especially, disease duration. In general, the more drug-experienced the patients, the lower the response rates, although this limitation can be overcome by promptly adjusting or switching treatment in a treat-to-target approach. Another challenge is the question of how long therapy should be continued once the treatment target, which should be remission or at least a state of low disease activity, has been reached. The data available suggest that, in most patients with established disease, cessation of biologic therapy will be followed by disease flares, whereas a reduction of dose or an increase in the interval between doses enables maintenance of treatment success. Induction therapy very early in the disease course followed by withdrawal of the biologic agent might also be a feasible approach to attain sustained good outcomes, but currently available data are not strong enough to allow for such a conclusion to be reached. Taken together, this underscores the importance of research into the cause(s) of RA so that curative therapies can be developed.

Specific therapy to regulate inflammation in rheumatoid arthritis: molecular aspects

Rheumatoid arthritis (RA) is a chronic inflammatory disease in which persistent inflammation of synovial tissue results in a progressive functional decline of the joint and premature mortality. TNF inhibitors were the first biological disease-modifying antirheumatic drugs (DMARDs) used to treat RA. Since then, new biological drugs have emerged, such as inhibitors of IL-1, IL-6 and others, with different mechanisms of action that include the depletion of B cells and the inhibition of T-cell costimulation. Recently, RA treatments have incorporated the use of synthetic DMARDs. This review describes the molecular aspects of the mechanisms of action of biological and synthetic DMARDs, discusses the adverse effects and limitations of established therapies and analyses the alternative approaches to RA treatment.

Non-canonical NF-κB signaling in rheumatoid arthritis: Dr Jekyll and Mr Hyde?

The nuclear factor-κB (NF-κB) family of transcription factors is essential for the expression of pro-inflammatory cytokines, but can also induce regulatory pathways. NF-κB can be activated via two distinct pathways: the classical or canonical pathway, and the alternative or non-canonical pathway. It is well established that the canonical NF-κB pathway is essential both in acute inflammatory responses and in chronic inflammatory diseases, including rheumatoid arthritis (RA). Although less extensively studied, the non-canonical NF-κB pathway is not only central in lymphoid organ development and adaptive immune responses, but is also thought to play an important role in the pathogenesis of RA. Importantly, this pathway appears to have cell type-specific functions and, since many different cell types are involved in the pathogenesis of RA, it is difficult to predict the net overall contribution of the non-canonical NF-κB pathway to synovial inflammation. In this review, we describe the current understanding of non-canonical NF-κB signaling in various important cell types in the context of RA and consider the relevance to the pathogenesis of the disease. In addition, we discuss current drugs targeting this pathway, as well as future therapeutic prospects.

MiR-30a-3p negatively regulates BAFF synthesis in systemic sclerosis and rheumatoid arthritis fibroblasts

We evaluated micro (mi) RNA-mediated regulation of BAFF expression in fibroblasts using two concomitant models: (i) synovial fibroblasts (FLS) isolated from healthy controls (N) or Rheumatoid Arthritis (RA) patients; (ii) human dermal fibroblasts (HDF) isolated from healthy controls (N) or Systemic Sclerosis (SSc) patients. Using RT-qPCR and ELISA, we first showed that SScHDF synthesized and released BAFF in response to Poly(I:C) or IFN-γ treatment, as previously observed in RAFLS, whereas NHDF released BAFF preferentially in response to IFN-γ. Next, we demonstrated that miR-30a-3p expression was down regulated in RAFLS and SScHDF stimulated with Poly(I:C) or IFN-γ. Moreover, we demonstrated that transfecting miR-30a-3p mimic in Poly(I:C)- and IFN-γ-activated RAFLS and SScHDF showed a strong decrease on BAFF synthesis and release and thus B cells survival in our model. Interestingly, FLS and HDF isolated from healthy subjects express higher levels of miR-30a-3p and lower levels of BAFF than RAFLS and SScHDF. Transfection of miR-30a-3p antisense in Poly(I:C)- and IFN-γ-activated NFLS and NHDF upregulated BAFF secretion, confirming that this microRNA is a basal repressors of BAFF expression in cells from healthy donors. Our data suggest a critical role of miR-30a-3p in the regulation of BAFF expression, which could have a major impact in the regulation of the autoimmune responses occurring in RA and SSc.

Distinct effects of methotrexate and etanercept on the B cell compartment in patients with juvenile idiopathic arthritis

Objective

B cells have been shown to play an important role in the pathogenesis of rheumatoid arthritis and juvenile idiopathic arthritis (JIA). Current treatments include the disease-modifying antirheumatic drugs methotrexate (MTX) and tumor necrosis factor α inhibition with etanercept. This study was undertaken to determine how these drugs influence the B cell compartment in patients with JIA.

Methods

B cell subpopulations and follicular helper T (Tfh) cells in the peripheral blood of JIA patients were investigated by multicolor flow cytometry. Serum immunoglobulin and BAFF levels were determined by enzyme-linked immunosorbent assay.

Results

There was a significant decrease in transitional B cells and significantly lower serum immunoglobulin levels in patients receiving MTX than in untreated patients and those receiving etanercept. In contrast, etanercept treatment had no effect on most of the B cell subpopulations, but resulted in significantly lower BAFF levels and increased numbers of Tfh cells. Thus, our findings indicate an unexpected and previously unknown direct effect of low-dose MTX on B cells, whereas etanercept had a more indirect influence.

Conclusion

Our results contribute to a better understanding of the potency of MTX in autoantibody-mediated autoimmune disease and present a possible mechanism of prevention of the development of drug-induced antibodies to biologic agents. The finding that MTX and etanercept affect the B cell compartment differently supports the notion that combination therapy with etanercept and MTX is more effective than monotherapy.

Effects of B-lymphocyte dysfunction on the serum copper, selenium and zinc levels of rheumatoid arthritis patients

Objective: To study the effects of B-lymphocyte dysfunction on the serum copper, selenium and zinc levels of rheumatoid arthritis (RA) patients, and to provide evidence for clinical practice.

Methods: Sixty RA patients enrolled in our hospital from August 2009 to August 2013 were selected as the observation group. Another 60 healthy subjects who received physical examinations in our hospital were selected as the control group. Their B-lymphocyte stimulator (BlyS) levels and CD19⁺CD25⁺ lymphocyte percentages were determined. The levels of trace elements were measured, and correlation analysis was performed.

Results: The BlyS levels of the observation group and the control group were (0.39±0.21) ng/ml and (0.13±0.04) ng/ml respectively, which were significantly different (P<0.05). The percentages of CD25⁺, CD19⁺ and CD19⁺CD25⁺ lymphocytes in the observation group were significantly higher than those in the control group (P<0.05). The serum copper, selenium and zinc levels of the observation group were significantly lower than those of the control group (P<0.05). Pearson's correlation analysis showed that the BlyS level was correlated with the levels of copper, selenium and zinc respectively (r=-0.541, -0.370, -0.430, P<0.05).

Conclusion: Rheumatoid Arthritis may be induced by BlyS-mediated B-lymphocyte dysplasia and dysfunction, accompanied by decreased expressions of copper, selenium and zinc.

Atacicept as an investigated therapy for rheumatoid arthritis

INTRODUCTION

Rheumatoid arthritis (RA) is a chronic, painful and debilitating autoimmune disease. Although the outcome for patients with RA has improved markedly in the past decades, adequate disease control cannot be achieved in a substantial proportion of patients. Since RA is a syndrome with different biological subsets, new drugs with a novel mechanism of action may represent a valuable addition to the current armamentarium.

AREAS COVERED

This review focuses on the pharmacodynamics and pharmacokinetics of atacicept . Furthermore, the article both summarises and comments on the drug's efficacy and safety profile in RA patients.

EXPERT OPINION

Atacicept is designed to neutralise B-lymphocyte stimulator (BLyS) and a proliferation-inducing ligand, two cytokines involving B-cell function and survival. Two recent Phase II studies have demonstrated that atacicept was not effective in RA patients with an inadequate response to methotrexate or TNF antagonists. However, atacicept displayed significant biological activity, including reduction of Ig and rheumatoid factor levels. Adverse events were slightly more frequent among patients treated with atacicept compared with placebo. In contrast to patients with systemic lupus erythematosus, RA patients receiving atacicept did not show an increased susceptibility to infections. In view of its important impact on immunoglobulin-secreting cells, this drug might be a rational therapy for hematological diseases.

Regulation of B lymphocytes and plasma cells by innate immune mechanisms and stromal cells in rheumatoid arthritis

B cells mediate multiple functions that influence immune and inflammatory responses in rheumatoid arthritis. Production of a diverse array of autoantibodies can happen at different stages of the disease, and are important markers of disease outcome. In turn, the magnitude and quality of acquired humoral immune responses is strongly dependent on signals delivered by innate immune cells. Additionally, the milieu of cells and chemokines that constitute a niche for plasma cells rely strongly on signals provided by stromal cells at different anatomical locations and times. The chronic inflammatory state therefore importantly impacts the developing humoral immune response and its intensity and specificity. We focus this review on B cell biology and the role of the innate immune system in the development of autoimmunity in patients with rheumatoid arthritis.

Efficacy and safety implications of molecular constructs of biological agents for rheumatoid arthritis

INTRODUCTION

Targeted biologic immunomodulatory therapies have had a major impact in rheumatoid arthritis (RA) treatment, including tumor necrosis factor (TNF)-α inhibition, B-cell depletion, interference in T-cell costimulation and interleukin (IL)-1 and IL-6 inhibition. Along with the recognition of the importance of early, aggressive disease-modifying antirheumatic drugs (DMARDs) grounded in the use of methotrexate, the introduction of biologic DMARDs (bDMARDs) has provided significantly improved outcomes in patients with RA with a goal of true remission, or at least a state of very low disease activity, now possible in many. There are a number of methods to inhibit cytokines, cellular receptors and pathways of signal transduction that have been used thus far and are in development. In some cases, the method of target inhibition and differences in molecular construct has impacted efficacy and/or safety; whereas, in other cases, similar safety and/or efficacy signals across compounds have demonstrated class- or target-related effects. As the development of targeted therapies moves forward, it is increasingly important to understand the role of the target both in RA disease pathogenesis and normal host defense and the mechanisms of target inhibition.

AREAS COVERED

This review covers the targets of therapy for biologic agents in rheumatic diseases, their molecular constructs and implications on efficacy and safety, with focus on approved treatments for RA.

EXPERT OPINION

Advances in molecular biology have provided a number of different ways to impact pathobiologically relevant pathways and targets in terms of the molecular construct of individual compounds. The use of these agents have provided important mechanistic insights into disease pathogenesis, and in some cases are associated with differences in efficacy and safety among agents even with the same downstream target. As bDMARDs identify promising mechanisms, oral agents that target or specifically regulate downstream pathways are made possible.

Targeting spleen tyrosine kinase-Bruton's tyrosine kinase axis for immunologically mediated glomerulonephritis

The importance of B-cell activation and immune complex-mediated Fc-receptor activation in the pathogenesis of immunologically mediated glomerulonephritis has long been recognized. The two nonreceptor tyrosine kinases, spleen tyrosine kinase (Syk) and Bruton's tyrosine kinase (Btk), are primarily expressed by hematopoietic cells, and participate in B-cell-receptor- and Fc-receptor-mediated activation. Pharmacological inhibitors of Syk or Btk are undergoing preclinical development and clinical trials for several immune diseases; and Syk inhibitors have been shown to reduce disease activity in rheumatoid arthritis patients. However, the clinical therapeutic efficacies of these inhibitors in glomerulonephritis have not been evaluated. Herein, we review recent studies of Syk and Btk inhibitors in several experimental primary and secondary glomerulonephritis models. These inhibitors suppressed development of glomerular injury, and also ameliorated established kidney disease. Thus, targeting Syk and Btk signaling pathways is a potential therapeutic strategy for glomerulonephritis, and further evaluation is recommended.

Emerging immunotherapies for rheumatoid arthritis

Novel treatments in development for rheumatoid arthritis target 3 broad areas: cytokines, cells, and signaling pathways. Therapies from each domain share common advantages (for example previously demonstrated efficacy, potential long-term immunomodulation, and oral administration respectively) that have stimulated research in each area but also common obstacles to their development. In this review recent progress in each area will be discussed alongside the factors that have impeded their path to clinical use.

Non-tumor necrosis factor-based biologic therapies for rheumatoid arthritis: present, future, and insights into pathogenesis

The way rheumatoid arthritis is treated has changed dramatically with the introduction of anti-tumor necrosis factor (anti-TNF) biologics. Nevertheless, many patients still have less than adequate control of their disease activity even with these therapeutic regimens, and current knowledge fails to explain all the data already gathered. There is now a wide range of drugs from different classes of biologic disease-modifying anti-rheumatic drugs available (and soon this number will increase significantly), that provides the opportunity to address each patient as a particular case and thereby optimize medical intervention. Currently available biologics for the treatment of rheumatoid arthritis apart from anti-TNF-based therapies are reviewed, along with an analysis of the new insights they provide into the pathogenesis of the disease and a discussion of future prospects in the area.

B-cell-targeted therapy in adult glomerulonephritis

INTRODUCTION

There are many mechanisms through which B lymphocytes have been implicated in the pathogenesis of glomerulonephritis. There are a number of trials and clinical studies in glomerulonephritis involving depletion of CD20(+) B lymphocytes using rituximab. Newer anti-CD20 agents are currently under evaluation, as are drugs targeting alternative B-cell targets such as B lymphocyte stimulator. Such selective, targeted B-cell therapies, if shown to be effective, may be of value in minimising toxicity from more conventional agents.

AREAS COVERED

This article reviews the role of B cells as a target for therapy in adult renal disease resulting from primary glomerulonephritis and that occurring secondary to systemic disease. It will not address intracellular signalling or co-stimulatory pathways as therapeutic targets.

EXPERT OPINION

There are indications for B-cell targeted therapies in a number of adult glomerulonephritides, with varying degrees of evidence. Further understanding of the mechanisms of B-cell depletion and repletion, and interplay with B-cell survival factors, is necessary in order to identify patients who will respond favourably.

Monoclonal antibody treatments for rheumatoid arthritis

INTRODUCTION

Rheumatoid arthritis (RA) is a systemic disease and the most prevalent of all autoimmune disorders. Here we review recent advances in the development and availability of biologic agents with a focus on monoclonal antibody or smaller formats of targeted engineered therapeutics including novel, non-antibody-based therapeutics.

AREAS COVERED

Today an array of biologics blocking either proinflammatory cytokines or lymphocyte activation/survival are available that enable a substantial improvement over conventional disease-modifying antirheumatic drugs (DMARDs). We review the engineering process of antibody-based biologics, their preclinical and clinical application, and current efforts to treat RA by interfering with B-cell function (notable targets covered are CD20, CD38, B-cell activating factor, transmembrane activator and calcium-modulating and cyclophilin interactor), with T-cell function (CD3, CD4, CD28), with bone erosion (RANKL), and with cytokines or growth factors (tumor necrosis factor, interleukin-1 [IL-1], IL-6, IL-17, VEGF). Future treatment choices might encompass the blockade or modulation of danger-associated molecular patterns such as HMGB1, pattern recognition receptors, messenger RNAs or noncoding RNAs, histone acetylation, and inflammasome components.

EXPERT OPINION

Although current therapies can reduce the signs and symptoms of RA for many patients, the quest for a cure (or a more complete blockade of the structural damage) in RA is still ongoing and will need treatment approaches, which are not exclusively confined to blocking a particular cytokine, receptor, or autoreactive B or T cell involved in disease progression. To this end exciting treatment alternatives and drug targets are on the horizon that may become available to patients in the future.