A perspective on B-cell-targeting therapy for SLE

Pharmacological inhibition of NF-κB-inducing kinase (NIK) with small molecules for the treatment of human diseases

NIK is a key kinase required for the activation of alternative NF-κB signaling pathways. Overactivation of NIK in patients has been observed and is implicated in the pathogenesis of inflammatory diseases, B-cell malignances, and solid tumors. Over the past decade, inhibition of NIK overactivation with small molecules has been pursued as an attractive strategy for drug discovery, where numerous potent and selective NIK inhibitors with novel pharmacophores have been identified. This review summarizes the structural features and key efficacy studies of the NIK inhibitors reported, which justify the mechanism of action of such inhibitors in animal models driven by NIK overactivation. Given the strong pathological associations between overactivation of NIK and human diseases, human clinical trials of NIK inhibitors as drug candidates are eagerly awaited. Information showcased in this review article might be helpful for the discovery and clinical development of the next generation of NIK inhibitors in the near future.

Mesenchymal Stem Cells: Allogeneic MSC May Be Immunosuppressive but Autologous MSC Are Dysfunctional in Lupus Patients

Mesenchymal stem cells (MSCs) have a potently immunosuppressive capacity in both innate and adaptive immune responses. Consequently, MSCs transplantation has emerged as a potential beneficial therapy for autoimmune diseases even though the mechanisms underlying the immunomodulatory activity of MSCs is incompletely understood. Transplanted MSCs from healthy individuals with no known history of autoimmune disease are immunosuppressive in systemic lupus erythematosus (SLE) patients and can ameliorate SLE disease symptoms in those same patients. In contrast, autologous MSCs from SLE patients are not immunosuppressive and do not ameliorate disease symptoms. Recent studies have shown that MSCs from SLE patients are dysfunctional in both proliferation and immunoregulation and phenotypically senescent. The senescent phenotype has been attributed to multiple genes and signaling pathways. In this review, we focus on the possible mechanisms for the defective phenotype and function of MSCs from SLE patients and summarize recent research on MSCs in autoimmune diseases.

Systemic lupus erythematosus: Diagnosis and clinical management

Systemic lupus erythematosus (SLE) is a worldwide chronic autoimmune disease which may affect every organ and tissue. Genetic predisposition, environmental triggers, and the hormonal milieu, interplay in disease development and activity. Clinical manifestations and the pattern of organ involvement are widely heterogenous, reflecting the complex mosaic of disrupted molecular pathways converging into the SLE clinical phenotype. The SLE complex pathogenesis involves multiple cellular components of the innate and immune systems, presence of autoantibodies and immunocomplexes, engagement of the complement system, dysregulation of several cytokines including type I interferons, and disruption of the clearance of nucleic acids after cell death. Use of immunomodulators and immunosuppression has altered the natural course of SLE. In addition, morbidity and mortality in SLE not only derive from direct immune mediated tissue damage but also from SLE and treatment associated complications such as accelerated coronary artery disease and increased infection risk. Here, we review the diagnostic approach as well as the etiopathogenetic rationale and clinical evidence for the management of SLE. This includes 1) lifestyle changes such as avoidance of ultraviolet light; 2) prevention of comorbidities including coronary artery disease, osteoporosis, infections, and drug toxicities; 3) use of immunomodulators (i.e. hydroxychloroquine and vitamin D); and 4) immunosuppressants and targeted therapy. We also review new upcoming agents and regimens currently under study.

NF-κB inducing kinase is a therapeutic target for systemic lupus erythematosus

NF-κB-inducing kinase (NIK) mediates non-canonical NF-κB signaling downstream of multiple TNF family members, including BAFF, TWEAK, CD40, and OX40, which are implicated in the pathogenesis of systemic lupus erythematosus (SLE). Here, we show that experimental lupus in NZB/W F1 mice can be treated with a highly selective and potent NIK small molecule inhibitor. Both in vitro as well as in vivo, NIK inhibition recapitulates the pharmacological effects of BAFF blockade, which is clinically efficacious in SLE. Furthermore, NIK inhibition also affects T cell parameters in the spleen and proinflammatory gene expression in the kidney, which may be attributable to inhibition of OX40 and TWEAK signaling, respectively. As a consequence, NIK inhibition results in improved survival, reduced renal pathology, and lower proteinuria scores. Collectively, our data suggest that NIK inhibition is a potential therapeutic approach for SLE.

Toll-like receptors in systemic lupus erythematosus: potential for personalized treatment

Systemic lupus erythematosus (SLE) is a complex autoimmune disease characterized by the loss of tolerance to self-nuclear antigens. The symptoms of SLE, progression of pathology and the array of autoantibodies present in the serum differ significantly from patient to patient, which calls for a personalized approach to treatment. SLE is polygenic and strongly influenced by gender, ethnicity, and environmental factors. Data from genome-wide association studies suggests that polymorphisms in as many as 100 genes contribute to SLE susceptibility. Recent research has focused on genes associated with Toll-like receptors (TLRs), type I interferons, immune regulation pathways, and immune-complex clearance. TLR7 and TLR9 have been extensively studied using lupus-prone mouse models. In multiple systems overexpression of TLR7 drives disease progression but interestingly, a loss of TLR9 results in an almost identical phenotype. While TLR7 overexpression has been linked to human SLE, the possible role of TLR9 in human disease remains elusive. In the present review, we focus on TLR polymorphisms and TLR expression in SLE patients and discuss their potential as biomarkers for individualized treatment.

Profile of epratuzumab and its potential in the treatment of systemic lupus erythematosus

Management of systemic lupus erythematosus (SLE) represents a fascinating, emerging field. Research has recently provided us with a better understanding of the immunologic alterations of SLE, leading to the creation of immunomodulatory agents designed to disrupt specific cell targets and pro-inflammatory pathways. Despite the improvement in the prognosis of SLE in the last 50 years with the use of immunosuppressive therapy such as cyclophosphamide and mycophenolate mofetil, cytotoxicity remains a major complication of these medications and the need for more specific targeted immunotherapy is increasing. Early recognition and treatment of SLE with targeted immunotherapy has the potential to improve quality of life and reduce the risk of disease flare-ups and complications. In this review, we will explore the role of B-cells in the pathogenesis of SLE highlighting current insights into SLE development and management. In addition, we will discuss epratuzumab’s role in the treatment of SLE. Epratuzumab is a humanized anti-CD22 monoclonal antibody that targets CD22 on B-cell and its role in B-cell modulation, migration, function, and inhibition of B-cell receptor signaling. Epratuzumab is currently in a Phase III study evaluating its efficacy in the management of moderate to severe SLE. All published trials on epratuzumab have shown great promise with safe profiles.

Retinoic acid-producing, ex-vivo-generated human tolerogenic dendritic cells induce the proliferation of immunosuppressive B lymphocytes

While much is known about tolerogenic dendritic cell effects on forkhead box protein 3 (FoxP3)⁺ regulatory T cells, virtually nothing is known about their effects on another arm of immunoregulation that is mediated by a subpopulation of immunosuppressive B cells. These cells suppress rheumatoid arthritis, lupus and inflammatory bowel disease in mice, and functional defects have been reported in human lupus. We show that co-stimulation-impaired tolerogenic dendritic cells that prevent and reverse type 1 diabetes mellitus induce the proliferation of human immunosuppressive B cells in vitro. We also show that the suppressive properties of these B cells concentrate inside the CD19⁺ CD24⁺ B cell population and more specifically inside the CD19⁺ CD24⁺ CD38⁺ regulatory B cell population. We discovered that B cell conversion into suppressive cells in vitro is partially dependent on dendritic cell production of retinoic acid and also that CD19⁺ CD24⁺ CD38⁺ B regulatory cells express retinoic acid receptors. Taken together, our data suggest a model whereby part of the immunosuppressive properties of human tolerogenic dendritic cells could be mediated by retinoic acid which, in addition to its known role in favouring T cell differentiation to FoxP3⁺ regulatory T cells, acts to convert B cells into immunosuppressive cells.

Protein kinase Cβ is required for lupus development in Sle mice

OBJECTIVE

To evaluate the requirement for protein kinase Cβ (PKCβ) in the development of lupus in mice, and to explore the potential of targeting PKCβ as a therapeutic strategy in lupus.

METHODS

Congenic mice bearing the disease loci Sle1 or Sle1 and Sle3, which represent different stages of severity in the development of lupus, were crossed with PKCβ-deficient mice. The effect of PKCβ deficiency in lupus development was analyzed. In addition, the effects of the PKCβ-specific inhibitor enzastaurin on the survival of B cells from mice with lupus and human 9G4-positive B cells as well as the in vivo effect of enzastaurin treatment on the development of lupus in Sle mice were investigated.

RESULTS

In Sle mice, PKCβ deficiency abrogated lupus-associated phenotypes, including high autoantibody levels, proteinuria, and histologic features of lupus nephritis. Significant decreases in spleen size and in the peritoneal B-1 cell population, reduced numbers of activated CD4 T cells, and normalized CD4:CD8 ratios were observed. PKCβ deficiency induced an anergic B cell phenotype and preferentially inhibited autoreactive plasma cells and autoantibodies in mice with lupus. Inhibition of PKCβ enhanced apoptosis of both B cells from Sle mice and human autoreactive B cells (9G4 positive). Treatment of Sle mice with the PKCβ-specific inhibitor enzastaurin prevented the development of lupus.

CONCLUSION

This study identifies PKCβ as a central mediator of lupus pathogenesis, suggesting that PKCβ represents a promising therapeutic target for the treatment of systemic lupus erythematosus. Moreover, the results indicate the feasibility of using a PKCβ inhibitor for the treatment of lupus.

Taming lupus-a new understanding of pathogenesis is leading to clinical advances

Systemic lupus erythematosus (SLE) is an autoimmune disease that is characterized by the loss of tolerance to nuclear self antigens, the production of pathogenic autoantibodies and damage to multiple organ systems. Over the years, patients with SLE have been managed largely with empiric immunosuppressive therapies, which are associated with substantial toxicities and do not always provide adequate control of the disease. The development of targeted therapies that specifically address disease pathogenesis or progression has lagged, largely because of the complex and heterogeneous nature of the disease, as well as difficulties in designing uniform outcome measures for clinical trials. Recent advances that could improve the treatment of SLE include the identification of genetic variations that influence the risk of developing the disease, an enhanced understanding of innate and adaptive immune activation and regulation of tolerance, dissection of immune cell activation and inflammatory pathways and elucidation of mechanisms and markers of tissue damage. These discoveries, together with improvements in clinical trial design, form a platform from which to launch the development of a new generation of lupus therapies.

Resolve, revise, and relax: the 3 Rs of B cell repertoire adjustment

Competition for limited, cell extrinsic survival factors is a general feature of peripheral selection checkpoints involved in B lymphocyte maturation and activation. Perhaps the best-characterized example involves BLyS (B lymphocyte stimulator), which modulates the size and composition of mature naïve B cell pools, but evidence for analogous competitive checkpoints is emerging for both germinal center B cells and plasma cells. Here we discuss how deliberate alteration of BLyS levels might be used to manipulate B cell repertoire selection in order to restore self-tolerance in autoimmunity, remodel the repertoire to accommodate neo-self antigens introduced through transplantation and gene therapy, or expand repertoire diversity to reveal novel, therapeutically useful specificities.

[Pathogenic basis of B cell targeted therapy in systemic lupus erythematosus (SLE)]

Recent success of B-cell targeted therapies in rheumatoid arthritis suggests their potential efficacy for other auntoantibody-mediated autoimmune diseases. Currently, multiple agents directed toward different B-cell specific targets are under development. Although the best strategy is yet to be defined, multiple functional inhibitors or cytolitic agents such as anti-CD20 or anti-CD19 are available. According to studies in RA, the most likely mechanism of action of rituximab (anti-CD20) consists of a secondary reduction in local (synovial) or systemic autoantibody producing short-lived plasma cells. According to this data, it is expected that these therapies will be efficacious in SLE, were B-cell enhanced function and autoantibodies play relevant pathogenetic roles. Clinical trials confirm B-cell effects, delayed activity on autoantibody synthesis, and most importantly, the feasibility of these therapies to treat SLE. However, there are no sufficient data confirming their therapeutic value when added to convencional therapy. Although multiple open trials suggest that rituximab might be useful for refractory manifestations of SLE, more controlled trials are needed in order to establish the indications and strategies of its use in SLE.

Targeting BLyS in rheumatic disease: the sometimes-bumpy road from bench to bedside

PURPOSE OF REVIEW

BLyS family ligands and receptors are key players in the selection and survival of most mature B lymphocytes. The fundamental role of BLyS in transitional B cell selection, coupled with the relative BLyS-independence of memory B cells and plasma cells, suggests that BLyS may be a useful therapeutic target in strategies directed against preimmune B cell pools. Several agents that target BLyS are in clinical trials now, and we summarize recent results here, with a focus on systemic lupus erythematosus (SLE).

RECENT FINDINGS

Belimumab, a human neutralizing anti-BLyS monoclonal antibody, has delivered moderate but positive results in two separate phase III clinical trials for SLE, and was recently recommended for approval by an FDA advisory panel. Additional agents targeting BLyS or other members of this cytokine receptor family are also being tested in clinical trials.

SUMMARY

Together, these trials should yield novel therapies for a debilitating and often intractable illness and offer insights that in turn should foster subsequent generations of personalized, targeted therapies for rheumatic diseases.

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.

Targeting B cells for the treatment of SLE: the beginning of the end or the end of the beginning?

Systemic Lupus Erythematosus (SLE) is a systemic autoimmune disease for which therapeutic advances in immunosuppressive and support therapy have significantly improved survival over the last 5 decades. Unfortunately, SLE still carries substantially increased rates of mortality and end stage renal disease which are even more elevated in younger patients. No new drugs have been approved for SLE in over 50 years. Hence, a lot of hope and excitement has been generated by the development of biological agents designed to eliminate B cells either through direct killing (anti-B cell antibodies such as rituximab) or attrition by inhibition of survival (anti-BLyS/BAFF agents such as belimumab). Indeed a strong rationale for targeting B cells in SLE is supported by the major pathogenic roles they play in SLE through both autoantibody production and multiple antibody-independent functions. These hopes, however, have been darted by the failure of two different phase III randomized placebo-controlled trials of rituximab. Yet, clinicians continue to use rituximab off-label with the belief that it provides significant benefit and can rescue patients with disease that is refractory to current modalities. Moreover, recent positive results of two large controlled trials of belimumab have restored confidence that B cell targeting may after all be of benefit in SLE. In this review we discuss the background and rationale for the use of anti-B cell agents in SLE, review the available results, and provide models that could help reconcile the opposing results observed in different studies. These models could also help frame the design and evaluation of current and future B cell therapies.

Innovative management of lupus erythematosus

This article focuses on the management of discoid lupus erythematosus, subacute cutaneous lupus erythematosus, and systemic lupus erythematosus when the usual therapeutic arsenal such as oral antimalarial drugs and topical/oral steroids fail or provide insufficient treatment efficacy. Many of the treatments listed are the same or similar to each other because of similarities in the pathogenesis of various subtypes of cutaneous lupus. The clinical challenge is to determine the indications for topical versus systemic therapy, and to also identify the scenarios when combined therapy is necessary.

Regulatory B cells (B10 cells) have a suppressive role in murine lupus: CD19 and B10 cell deficiency exacerbates systemic autoimmunity

B cells play critical roles in the pathogenesis of lupus. To examine the influence of B cells on disease pathogenesis in a murine lupus model, New Zealand Black and New Zealand White F(1) hybrid (NZB/W) mice were generated that were deficient for CD19 (CD19(-/-) NZB/W mice), a B cell-specific cell surface molecule that is essential for optimal B cell signal transduction. The emergence of anti-nuclear Abs was significantly delayed in CD19(-/-) NZB/W mice compared with wild type NZB/W mice. However, the pathologic manifestations of nephritis appeared significantly earlier, and survival was significantly reduced in CD19(-/-) NZB/W mice compared with wild type mice. These results demonstrate both disease-promoting and protective roles for B cells in lupus pathogenesis. Recent studies have identified a potent regulatory B cell subset (B10 cells) within the rare CD1d(hi)CD5(+) B cell subset of the spleen that regulates acute inflammation and autoimmunity through the production of IL-10. In wild type NZB/W mice, the CD1d(hi)CD5(+)B220(+) B cell subset that includes B10 cells was increased by 2.5-fold during the disease course, whereas CD19(-/-) NZB/W mice lacked this CD1d(hi)CD5(+) regulatory B cell subset. However, the transfer of splenic CD1d(hi)CD5(+) B cells from wild type NZB/W mice into CD19(-/-) NZB/W recipients significantly prolonged their survival. Furthermore, regulatory T cells were significantly decreased in CD19(-/-) NZB/W mice, but the transfer of wild type CD1d(hi)CD5(+) B cells induced T regulatory cell expansion in CD19(-/-) NZB/W mice. These results demonstrate an important protective role for regulatory B10 cells in this systemic autoimmune disease.

B-cell biology and related therapies in systemic lupus erythematosus

Systemic lupus erythematosus (SLE) is a complex disease characterized by numerous autoantibodies and clinical involvement in multiple organ systems. The immunologic events triggering the onset and progression of clinical manifestations have not yet been fully defined, but a central role for B cells in the pathogenesis has been brought to the fore in the last several years. The breakdown of B-cell tolerance is likely a defining and early event in the disease process and may occur by multiple pathways, including alterations in factors that affect B-cell activation thresholds, B-cell longevity, and apoptotic cell processing. Antibody-dependent and -independent mechanisms of B cells are important in SLE. Thus, autoantibodies contribute to autoimmunity by multiple mechanisms including immune complex mediated type III hypersensitivity reactions, type II antibody-dependent cytotoxicity, and by instructing innate immune cells to produce pathogenic cytokines including interferon alpha, tumor necrosis factor, and interleukin 1. Recent data have highlighted the critical role of toll-like receptors as a link between the innate and adaptive immune system in SLE immunopathogenesis. Given the large body of evidence implicating abnormalities in the B-cell compartment in SLE, there has been a therapeutic focus on developing interventions that target the B-cell compartment. Several different approaches to targeting B cells have been used, including B-cell depletion with monoclonal antibodies against B-cell-specific molecules, induction of negative signaling in B cells, and blocking B-cell survival and activation factors. Overall, therapies targeting B cells are beginning to show promise in the treatment of SLE and continue to elucidate the diverse roles of B cells in this complex disease.