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

B-cell therapy in lupus nephritis: an overview

Systemic lupus erythematosus (SLE) is an autoimmune multisystem disease that commonly affects the kidneys. It is characterized by persistent autoantibody production that targets a multitude of self-antigens. B-cells, plasmablasts and plasma cells, as the source of these autoantibodies, play a major role in the development of lupus nephritis (LN), and are therefore promising therapeutic targets. To date, however, randomized clinical trials of B-cell therapies in LN have not lived up to expectations, whereas uncontrolled cohort and observational studies of B-cell antagonists have been more promising. In this article, we will review the current experience with B-cell therapy in LN and highlight the pitfalls that may have limited their success. We will conclude by suggesting B-cell-centric approaches to the management of LN based on what has been learned from the overall B-cell experience in SLE.

Multiple Functions of B Cells in the Pathogenesis of Systemic Lupus Erythematosus

Systemic lupus erythematosus (SLE) is an autoimmune disease characterized by excessive autoantibody production and multi-organ involvement. Although the etiology of SLE still remains unclear, recent studies have characterized several pathogenic B cell subsets and regulatory B cell subsets involved in the pathogenesis of SLE. Among pathogenic B cell subsets, age-associated B cells (ABCs) are a newly identified subset of autoreactive B cells with T-bet-dependent transcriptional programs and unique functional features in SLE. Accumulation of T-bet+ CD11c+ ABCs has been observed in SLE patients and lupus mouse models. In addition, innate-like B cells with the autoreactive B cell receptor (BCR) expression and long-lived plasma cells with persistent autoantibody production contribute to the development of SLE. Moreover, several regulatory B cell subsets with immune suppressive functions have been identified, while the impaired inhibitory effects of regulatory B cells have been indicated in SLE. Thus, further elucidation on the functional features of B cell subsets will provide new insights in understanding lupus pathogenesis and lead to novel therapeutic interventions in the treatment of SLE.

Innate Immune Cells' Contribution to Systemic Lupus Erythematosus

Systemic lupus erythematosus (SLE) is a chronic autoimmune disease characterized by the presence of autoantibodies against nuclear antigens, immune complex deposition, and tissue damage in the kidneys, skin, heart and lung. Because of the pathogenic role of antinuclear antibodies and autoreactive T cells in SLE, extensive efforts have been made to demonstrate how B cells act as antibody-producing or as antigen-presenting cells that can prime autoreactive T cell activation. With the discovery of new innate immune cells and inflammatory mediators, innate immunity is emerging as a key player in disease pathologies. Recent work over the last decade has highlighted the importance of innate immune cells and molecules in promoting and potentiating SLE. In this review, we discuss recent evidence of the involvement of different innate immune cells and pathways in the pathogenesis of SLE. We also discuss new therapeutics targets directed against innate immune components as potential novel therapies in SLE.

Prednisone treatment inhibits the differentiation of B lymphocytes into plasma cells in MRL/MpSlac-lpr mice

AIM

A number of evidence shows that the differentiation of B lymphocytes into plasma cells plays an important role in lupus pathogenesis. In this study we investigated how prednisone, a classical therapeutic drug for autoimmune diseases, regulated plasma cell differentiation in MRL/MpSlac-lpr mice.

METHODS

MRL/lpr mice were treated with prednisone (2.5 or 5 mg·kg(-1)·d(-1), ig) for 13 weeks, and the proteinuria levels and survival times were monitored. After the mice were euthanized, blood sample, spleen and thymus were collected. The serum levels of anti-dsDNA antibody, anti-nuclear antibody, IL-21, and IL-10 were detected using ELISA kits. Subsets of splenic B and T lymphocytes were quantified with flow cytometry. Transcription factor Blimp-1 and Bcl-6 expression was determined using qPCR and Western blot.

RESULTS

Prednisone treatment dose-dependently attenuated the lupus symptoms in MRL/lpr mice with decreased proteinuria levels, prolonged survival times, decreased serum anti-nuclear antibody levels, and reduced spleen and thymus indices. Prednisone treatment also significantly decreased the elevated percentages of plasma cells and plasma cell precursors, decreased the percentages of activated T cells, and increased the frequency of CD4(+)CD62L(+) cells, demonstrated that decreased anti-nuclear antibodies and improvements in lupus symptoms were associated with decreased plasma cells. Furthermore, prednisone treatment decreased serum IL-21 and IL-10 levels and reduced the expression of splenic Blimp-1 and Bcl-6 (two key regulatory factors for plasma cell differentiation) in MRL/lpr mice.

CONCLUSION

Prednisone treatment restricts B lymphocyte differentiation into plasma cells in MRL/lpr mice, which may be correlated with the inhibition of IL-21 production and the restoration of the balance between Blimp-1 and Bcl-6.

Inhibition of B lymphocyte-induced maturation protein-1 reduces the production of autoantibody and alleviates symptoms of systemic lupus erythematosus

The B lymphocyte-induced maturation protein-1 (Blimp-1) is an important transcription factor for the maintenance of antigen-specific immune responses, and it is crucial in the development of systemic lupus erythematosus (SLE). This study aimed to investigate the role of Blimp-1 in the development of SLE and autoimmune-like symptoms. Lentivirus-mediated Blimp-1 siRNA was constructed and injected into MRL-Fas(lpr) lupus mice. The expression levels of Blimp-1, J-chain, C-myc, XBP-1 and BCMA in peripheral blood mononuclear cells (PMBCs) were determined by RT-PCR. Anti-dsDNA autoantibody levels were detected using ELISA. The expression levels of Blimp-1 in liver, kidney, spleen and lymph nodes of mice were also detected by Western blot. The 24-h urinary protein was monitored weekly. Our results demonstrated that in MRL-Fas(lpr) lupus mice, Blimp-1 was upregulated in PMBCs, liver, kidney, spleen and lymph nodes. Administration of Blimp-1 siRNA reduced the expression of Blimp-1 and the anti-dsDNA level by 78 and 28%, respectively, in the peripheral blood, and the expression of XBP-1, J-chain and BCMA was also decreased. Although the Blimp-1 level in liver showed no significant changes, the levels of Blimp-1 in kidney, spleen and lymph nodes were dramatically decreased by 95, 72 and 47%, respectively. Kidney diseases induced by SLE in lupus mice were mitigated, and urinary protein levels were significantly decreased. These results indicate that Blimp-1 plays an important role in promoting the progression of SLE. Therefore, Blimp-1 may provide a new therapeutic target in the treatment of SLE.

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.

BAFF regulates activation of self-reactive T cells through B-cell dependent mechanisms and mediates protection in NOD mice

Targeting the BAFF/APRIL system has shown to be effective in preventing T-cell dependent autoimmune disease in the NOD mouse, a spontaneous model of type 1 diabetes. In this study we generated BAFF-deficient NOD mice to examine how BAFF availability would influence T-cell responses in vivo and the development of spontaneous diabetes. BAFF-deficient NOD mice which lack mature B cells, were protected from diabetes and showed delayed rejection of an allogeneic islet graft. Diabetes protection correlated with a failure to expand pathogenic IGRP-reactive CD8(+) T cells, which were maintained in the periphery at correspondingly low levels. Adoptive transfer of IGRP-reactive CD8(+) T cells with B cells into BAFF-deficient NOD mice enhanced IGRP-reactive CD8(+) T-cell expansion. Furthermore, when provoked with cyclophosphamide, or transferred to a secondary lymphopenic host, the latent pool of self-reactive T cells resident in BAFF-deficient NOD mice could elicit beta cell destruction. We conclude that lack of BAFF prevents the procurement of B-cell-dependent help necessary for the emergence of destructive diabetes. Indeed, treatment of NOD mice with the BAFF-blocking compound, BR3-Fc, resulted in a delayed onset and reduced incidence of diabetes.

CD22 and autoimmune disease

CD22 is a 140-kDa member of the Siglec family of cell surface proteins that is expressed by most mature B-cell lineages. As a co-receptor of the B-cell receptor (BCR), it is known to contribute to the sensitive control of the B-cell response to antigen. Cross-linking of CD22 and the BCR by antigen triggers the phosphorylation of CD22, which leads to activation of signaling molecules such as phosphatases. Signal transduction pathways involving CD22 have been explored in a number of mouse models, some of which have provided evidence that in the absence of functional CD22, B cells have a "hyperactivated" phenotype, and suggest that loss of CD22 function could contribute to the pathogenesis of autoimmune diseases. Modulating CD22 activity has therefore been suggested as a possible therapeutic approach to such diseases. For example, the novel CD22-targeting monoclonal antibody epratuzumab is currently under investigation as a treatment for the connective tissue disorder systemic lupus erythematosus (SLE).

Biological therapy in systemic lupus erythematosus

Systemic lupus erythematosus (SLE) is a prototypic inflammatory autoimmune disorder characterized by multisystem involvement and fluctuating disease activity. Symptoms range from rather mild manifestations such as rash or arthritis to life-threatening end-organ manifestations. Despite new and improved therapy having positively impacted the prognosis of SLE, a subgroup of patients do not respond to conventional therapy. Moreover, the risk of fatal outcomes and the damaging side effects of immunosuppressive therapies in SLE call for an improvement in the current therapeutic management. New therapeutic approaches are focused on B-cell targets, T-cell downregulation and costimulatory blockade, cytokine inhibition, and the modulation of complement. Several biological agents have been developed, but this encouraging news is associated with several disappointments in trials and provide a timely moment to reflect on biologic therapy in SLE.

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.

Role and therapeutic potential of Glycodelin A in systemic lupus erythematosus

Glycodelin A (GdA) is a lipocalin with an immunomodulatory role. Low expression of GdA has been implicated in the progression of autoimmune disease. Therefore, strategies targeting GdA may constitute an important target for the design of drugs for autoimmune disease including systemic lupus erythematosus (SLE). This opinion article will focus on current understanding of the role of GdA in the physiological and pathological functions associated with SLE. It is the intention of the article to provide insights that may assist in the development of GdA-based approaches for the treatment of SLE.

Current and emerging strategies for the treatment and management of systemic lupus erythematosus based on molecular signatures of acute and chronic inflammation

Lupus is a chronic, systemic inflammatory condition in which eicosanoids, cytokines, nitric oxide (NO), a deranged immune system, and genetics play a significant role. Our studies revealed that an imbalance in the pro- and antioxidants and NO and an alteration in the metabolism of essential fatty acids exist in lupus. The current strategy of management includes administration of nonsteroidal anti-inflammatory drugs such as hydroxychloroquine and immunosuppressive drugs such as corticosteroids. Investigational drugs include the following: 1) belimumab, a fully human monoclonal antibody that specifically recognizes and inhibits the biological activity of B-lymphocyte stimulator, also known as B-cell-activation factor of the TNF family; 2) stem cell transplantation; 3) rituximab, a chimeric monoclonal antibody against CD20, which is primarily found on the surface of B-cells and can therefore destroy B-cells; and 4) IL-27, which has potent anti-inflammatory actions. Our studies showed that a regimen of corticosteroids and cyclophosphamide, and methods designed to enhance endothelial NO synthesis and augment antioxidant defenses, led to induction of long-lasting remission of the disease. These results suggest that methods designed to modulate molecular signatures of the disease process and suppress inflammation could be of significant benefit in lupus. Some of these strategies could be vagal nerve stimulation, glucose-insulin infusion, and administration of lipoxins, resolvins, protectins, and nitrolipids by themselves or their stable synthetic analogs that are known to suppress inflammation and help in the resolution and healing of the inflammation-induced damage. These strategies are likely to be useful not only in lupus but also in other conditions, such as rheumatoid arthritis, scleroderma, ischemia-reperfusion injury to the myocardium, ischemic heart disease, and sepsis.

A new approach to comparing anti-CD20 antibodies: importance of the lipid rafts in their lytic efficiency

The view that B lymphocytes are pathogenic in diverse pathological settings is supported by the efficacy of B-cell-ablative therapy in lymphoproliferative disorders, autoimmune diseases and graft rejection. Anti-B-cell antibodies (Abs) directed against CD20 have therefore been generated, and of these, rituximab was the first anti-CD20 monoclonal Ab (mAb) to be applied. Rituximab-mediated apoptosis, complement-dependent cytotoxicity and Ab-dependent cellular cytotoxicity differ from one disease to another, and, for the same disease, from one patient to another. This knowledge has prompted the development of new anti-CD20 mAbs in the hope of improving B-cell depletion. The inclusion of CD20/anti-CD20 complexes in large lipid rafts (LRs) enhances the results of some, but not all, anti-CD20 mAbs, and it may be possible to include smaller LRs. Lipid contents of membrane may be abnormal in malignant B-cells, and could explain resistance to treatment. The function of these mAbs and the importance of LRs warrant further investigation. A detailed understanding of them will increase results for B-cell depletion in lymphoproliferative diseases.

Protective and pathogenic roles for B cells during systemic autoimmunity in NZB/W F1 mice

Delineating the relative contributions of B lymphocytes during the course of autoimmune disease has been difficult. Therefore, the effects of depleting all mature B cells using a potent CD20 mAb, or of depleting circulating and marginal zone B cells using a ligand-blocking CD22 mAb, were compared in NZB/W F(1) mice, a model for human systemic lupus erythematosus. Single low-dose mAb treatments depleted B cells efficiently in both NZB/W F(1) and C57BL/6 mice. Prophylactic B cell depletion by repeated CD20 mAb treatments prolonged survival during pristane-accelerated lupus in NZB/W F(1) mice, whereas CD22 mAb had little effect. Despite effective B cell depletion, neither mAb treatment prevented autoantibody generation. In addition, CD20, CD22, and control mAb-treated NZB/W F(1) mice developed anti-mouse IgG autoantibodies in contrast to parental NZB and NZW strains, which may have reduced the effectiveness of B cell depletion. Despite this, low-dose CD20 mAb treatment initiated in 12-28-wk-old mice, and administered every 4 wk thereafter, significantly delayed spontaneous disease in NZB/W F(1) mice. By contrast, B cell depletion initiated in 4-wk-old mice hastened disease onset, which paralleled depletion of the IL-10-producing regulatory B cell subset called B10 cells. B10 cells were phenotypically similar in NZB/W F(1) and C57BL/6 mice, but were expanded significantly in young NZB/W F(1) mice. Thus, B cell depletion had significant effects on NZB/W F(1) mouse survival that were dependent on the timing of treatment initiation. Therefore, distinct B cell populations can have opposing protective and pathogenic roles during lupus progression.

Monoclonal antibodies and fusion proteins and their complications: targeting B cells in autoimmune diseases

The immune system consists of a complex array of immunocompetent cells and inflammatory mediators that exist in complex networks. These components interact through cascades and feedback circuits, maintaining physiologic inflammation and immunosurveillance. In various autoimmune conditions, a foreign or auto-antigen may upset this fine balance, leading to dysregulated immunity, persistent inflammation, and ultimately pathologic sequelae. In recent years, there has been tremendous progress delineating the specific components of the immune system that contribute to normal immunity and specific disease states. With this greater understanding of pathogenesis coupled with advances in biotechnology, many immunomodulatory agents, commonly called biologic agents, have been introduced. The 2 most common classes of biologic agents are monoclonal antibodies and fusion proteins. These agents can inhibit targets with exquisite specificity to optimize outcomes and minimize toxicity. B cells contribute significantly to the initiation and perpetuation of the immune responses. B cells not only can produce potentially pathologic autoantibodies and proinflammatory cytokines but also can present antigens to T cells and provide costimulatory signals essential for T-cell activation, clonal expansion, and effector function. This review focuses on biologic agents targeting B cells in the treatment of rheumatoid arthritis and systemic lupus erythematosus.

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

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

Investigations of a rabbit (Oryctolagus cuniculus) model of systemic lupus erythematosus (SLE), BAFF and its receptors

B-cell activation factor belonging to the tumor necrosis factor family (BAFF) is a major contributor to survival of B lymphocytes during development and maturation. A relationship between circulating BAFF levels and disease activity has been reported in patients with the autoimmune disease Systemic Lupus Erythematosus (SLE). Clinical trials targeting BAFF or its receptors are currently in progress. In order to further characterize a rabbit (Oryctolagus cuniculus) model of SLE, we investigated the expression of BAFF and its receptors in non-inbred, pedigreed rabbits derived from breeding and selection based on autoantibody responses. We immunized rabbits related to previous groups that developed autoantibodies and inflammatory responses after immunizations with peptides synthesized on multiple antigen-branched polylysine backbones. Blood and sera collected before immunization and after boosts were used for health monitoring, analyses of serum autoantibody responses by ELISA and immunofluorescence. Peripheral blood mononuclear cells (PBMC) were studied by flow cytometry and were the source of mRNA for quantitative PCR analyses. We hypothesized that BAFF mRNA expression and serum BAFF levels measured indirectly through BAFF receptor binding might increase in autoantibody-producing rabbits. Immunized rabbits developed elevated levels of leucocyte populations, anti-nuclear, anti-dsDNA and other autoantibodies. BR3 mRNA levels in total PBMC decreased and BAFF levels remained low and unchanged in most immunized rabbits. By flow cytometry, percentages of BAFF positive cells decreased. Percentages of transmembrane activator and CAML interactor (TACI) decreased in most rabbits from all the immunized groups. The rabbit is an important model for human autoimmune and infectious diseases, and a high quality draft rabbit genome assembly was recently completed. Human disease models developed in non-inbred pedigreed animals are better able to reflect the complexities of diseases such as SLE with familial patterns of inheritance. Although no consistent pattern of elevated expression of BAFF mRNA or protein was found in the rabbits studied, the data collected and reported here build upon previous data to refine understanding of a rabbit model of SLE.

Translational Mini-Review Series on B Cell-Directed Therapies: B cell-directed therapy for autoimmune diseases

B cells play an important role in the pathogenesis of both systemic and organ-specific autoimmune diseases. Autoreactive B cells not only produce autoantibodies, but are also specialized to present specific autoantigens efficiently to T cells. Furthermore, these B cells can secrete proinflammatory cytokines and can amplify the vicious cycle of self-destruction. Thus, B cell-directed therapies are potentially an important approach for treating autoimmune diseases. On the other hand, like T cells, there are subsets of B cells that produce anti-inflammatory cytokines and are immunosuppressive. These regulatory B cell subsets can protect against and ameliorate autoimmune diseases. Thus targeting B cells therapeutically will require this balance to be considered. Here we summarize the roles of pathogenic and regulatory B cells and current applications of B cell-directed therapy in autoimmune diseases. Considerations for future development of B cell-directed therapy for autoimmune diseases have also been discussed.

Lupus nephritis

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

CD4(+)CD25(+) T-cells control autoimmunity in the absence of B-cells

OBJECTIVE

Tumor necrosis factor ligand family members B-cell-activating factor (BAFF) and a proliferation-inducing ligand (APRIL) can exert powerful effects on B-cell activation and development, type 1 T-helper cell (Th1) immune responses, and autoimmunity. We examined the effect of blocking BAFF and APRIL on the development of autoimmune diabetes.

RESEARCH DESIGN AND METHODS

Female NOD mice were administered B-cell maturation antigen (BCMA)-Fc from 9 to 15 weeks of age. Diabetes incidence, islet pathology, and T- and B-cell populations were examined.

RESULTS

BCMA-Fc treatment reduced the severity of insulitis and prevented diabetes development in NOD mice. BCMA-Fc-treated mice showed reduced follicular, marginal-zone, and T2MZ B-cells. B-cell reduction was accompanied by decreased frequencies of pathogenic CD4(+)CD40(+) T-cells and reduced Th1 cytokines IL-7, IL-15, and IL-17. Thus, T-cell activation was blunted with reduced B-cells. However, BCMA-Fc-treated mice still harbored detectable diabetogenic T-cells, suggesting that regulatory mechanisms contributed to diabetes prevention. Indeed, BCMA-Fc-treated mice accumulated increased CD4(+)CD25(+) regulatory T-cells (Tregs) with age. CD4(+)CD25(+) cells were essential for maintaining euglycemia because their depletion abrogated BCMA-Fc-mediated protection. BCMA-Fc did not directly affect Treg homeostasis given that CD4(+)CD25(+)Foxp3(+) T-cells did not express TACI or BR3 receptors and that CD4(+)CD25(+)Foxp3(+) T-cell frequencies were equivalent in wild-type, BAFF(-/-), TACI(-/-), BCMA(-/-), and BR3(-/-) mice. Rather, B-cell depletion resulted in CD4(+)CD25(+) T-cell-mediated protection from diabetes because anti-CD25 monoclonal antibody treatment precipitated diabetes in both diabetes-resistant NOD.microMT(-/-) and BCMA-Fc-treated mice.

CONCLUSIONS

BAFF/APRIL blockade prevents diabetes. BCMA-Fc reduces B-cells, subsequently blunting autoimmune activity and allowing endogenous regulatory mechanisms to preserve a prehyperglycemic state.

Pharmacokinetic and pharmacodynamic properties of TRU-015, a CD20-directed small modular immunopharmaceutical protein therapeutic, in patients with rheumatoid arthritis: a Phase I, open-label, dose-escalation clinical study

BACKGROUND

TRU-015 is a small modular immunopharmaceutical protein drug that binds to CD20 and effectively depleted B cells in nonhuman primates.

OBJECTIVE

The aim of this clinical study was to determine the pharmacokinetic (PK) and pharmacodynamic (PD) properties, immunogenicity, and tolerability of TRU-015 in patients with rheumatoid arthritis (RA).

METHODS

This Phase I, open-label, dose-escalation clinical study was conducted at 4 medical centers in the United States. Patients with RA who were receiving stable-dose methotrexate were enrolled in 1 of 8 dose groups and received TRU-015 as a single IV dose of 0.015, 0.05, 0.15, 0.5, 1.5, 5, or 15, or 2 IV doses of 15 mg/kg, administered 7 days apart (30 mg/kg). Patients were enrolled in the next higher dose cohort based on the tolerability observed in the prior cohort. Prior to TRU-015 infusion, patients were premedicated with an antihistamine and acetaminophen and may have received a corticosteroid at the investigator's discretion. Serum samples were collected for analysis of PK properties (serum t((1/2))) and neutralizing antibodies to TRU-015; enzyme-linked immunosorbent assays and a cell-based neutralizing assay were used to evaluate samples from patients. PD response was measured using B-cell (CD19(+)-cell) count using flow cytometry at prespecified time points. Tolerability was assessed during drug infusion and at prespecified time points after infusion using physical examination and laboratory analysis. Patients were followed for >or=4 weeks and until B-cell recovery.

RESULTS

Thirty-seven patients were enrolled. Most were female (81%) and white (95%); the mean age was 53 years. Serum t((1/2)) ranged from 12 to 19 days. B-cell depletion generally increased in degree and duration with increasing doses. No neutralizing antibodies to TRU-015 were detected. Mild adverse events (AEs) included back pain, headache, peripheral edema, and upper respiratory infection (5 patients each). Mild urticaria occurred in 1 patient. Grade 3 AEs included hypertension, arthralgia, and urticaria and bronchospasm (1 patient each). No dose-limiting toxicity was found.

CONCLUSIONS

In this small population of patients with RA, the C(max) and the AUC appeared to increase in a dose-proportional manner. The mean t((1/2)) ranged from 12 to 19 days. TRU-015 was associated with dose-dependent B-cell depletion and an acceptable tolerability profile.