B-Cell-Targeted Therapy for Systemic Lupus Erythematosus

Systemic lupus erythematosus (SLE) is a classic autoimmune disease characterized by a myriad of immune system aberrations, most likely resulting from pathogenic autoantibody production, immune complex deposition, and subsequent end-organ damage. B cells play a key role in the pathogenesis; therefore, B-cell-targeted therapies, including B-cell depletion and blockage of B-cell survival factors such as B-lymphocyte stimulator (BLyS), are potential therapeutic targets for SLE. In uncontrolled clinical trials from approximately 20 studies, rituximab--a mouse-human chimeric anti-CD20 monoclonal antibody that effectively depletes B cells--has been demonstrated to reduce disease activity and decrease serum autoantibodies, with a clinical response of 86% in a case series of approximately 400 SLE patients with refractory disease, with or without concomitant use of cyclophosphamide. Epratuzumab, a humanized anti-CD22 monoclonal antibody that partially depletes B cells, has also been shown to reduce disease activity but not to decrease autoantibody levels in patients with moderately active SLE. Randomized controlled phase I/II trials in patients with active SLE have documented that belimumab, a humanized anti-BLyS monoclonal antibody, reduces B-cell numbers, inhibits disease activity and decreases anti-double-stranded DNA autoantibody in SLE patients. All these therapies are well tolerated, but accompanying infectious complications have been observed. Other B-cell-targeted therapies such as 'humanized' monoclonal antibodies to CD20 (e.g. ocrelizumab) and agents that interrupt B-cell/T-cell interactions also have potential, and the efficacy of these, along with rituximab, belimumab and epratuzumab, needs to be determined by randomized controlled trials.     

Belimumab for the treatment of systemic lupus erythematosus

Given their pivotal role in autoantibody production, B-cells have become an attractive therapeutic target in systemic lupus erythematosus (SLE). Belimumab, a fully human monoclonal antibody against B lymphocyte stimulator (BLyS), a B-cell survival factor, was licensed in 2011 for the treatment of autoantibody-positive SLE. The BLISS-52 and BLISS-76 Phase III trials successfully demonstrated that belimumab (10 mg/kg) with standard therapy significantly decreased disease activity in SLE patients compared to placebo with standard therapy. Overall, belimumab has been found to be safe and well tolerated. While the BLISS-52 and BLISS-76 studies are the largest clinical trials in SLE to date, they mainly focused on musculoskeletal, mucocutaneous, hematologic and general constitutional features of the disease. Patients with severe lupus nephritis and severe central nervous system disease were excluded from these trials. Studies of belimumab in lupus nephritis are ongoing that may clarify the role of this agent in the clinical management of SLE.     

Improving B-cell depletion in systemic lupus erythematosus and rheumatoid arthritis

Introduction: Rituximab-based B-cell depletion (BCD) therapy is effective in refractory rheumatoid arthritis (RA) and although used to treat patients with refractory systemic lupus erythematosus (SLE) in routine clinical practice, rituximab failed to meet the primary endpoints in two large randomised controlled trials (RCTs) of non-renal (EXPLORER) and renal (LUNAR) SLE.

Areas covered: We review how BCD could be improved to achieve better clinical responses in RA and SLE. Insights into the variability in clinical response to BCD in RA and SLE may help develop new therapeutic strategies. To this end, a literature search was performed using the following terms: rheumatoid arthritis, systemic erythematosus lupus, rituximab and B-cell depletion.

Expert commentary: Poor trial design may have, at least partly, contributed to the apparent lack of response to BCD in the two RCTs of patients with SLE. Enhanced B-cell depletion and/or sequential therapy with belimumab may improve clinical response at least in some patients with SLE     

Epratuzumab, a CD22-targeting recombinant humanized antibody with a different mode of action from rituximab

Epratuzumab is a humanized anti-CD22 monoclonal antibody currently in clinical trials for treatment of non-Hodgkin lymphoma (NHL) and certain autoimmune diseases. Here we report the results of investigations of epratuzumab's mode of action in comparison to and in combination with the anti-CD20 mAb, rituximab. In vitro cell growth inhibition, induction of apoptosis, and the ability of the mAbs to mediate complement-dependent cytotoxicity (CDC) and antibody-dependent cellular cytotoxicity (ADCC) were evaluated. We also investigated the potential activity of epratuzumab in the regulation of B-cell antigen receptor (BCR) activation. Epratuzumab and rituximab displayed very distinct modes of action; epratuzumab acts as an immunomodulatory agent, while rituximab is an acutely cytotoxic therapeutic antibody. Epratuzumab has distinct effects on cell growth from rituximab. For example, rituximab+anti-human IgG Fcgamma yielded marked inhibition of proliferation in human NHL cell lines, while epratuzumab had little or no effect in this assay. However, when cells were immobilized and stimulated with anti-IgM, epratuzumab, but not rituximab, caused a significant antiproliferative effect. Unlike rituximab, no CDC could be detected, and ADCC was modest but significant with epratuzumab. Importantly, combining rituximab and epratuzumab did not decrease rituximab's ability to induce apoptosis, CDC, and ADCC. In fact, the combination is more effective than rituximab alone in inhibiting proliferation of Daudi Burkitt lymphoma cells in the presence of second antibody, and at least equally effective to rituximab in the absence of crosslinking. These observations suggest that it may be possible to enhance clinical efficacy by combination therapy comprised of anti-CD20 and anti-CD22 mAbs.     

B-cell-targeted therapies in systemic lupus erythematosus and ANCA-associated vasculitis: current progress

B cells play a central role in the pathogenesis of systemic lupus erythematosus and anti-neutrophil cytoplasmic antibody-associated vasculitis. There are various strategies for targeting B cells including depletion, inhibition of survival factors, activation and inhibition of co-stimulatory molecules. Controlled trials in systemic lupus erythematosus have shown positive results for belimumab, promising results for epratuzumab and negative results for rituximab. The failure of rituximab in controlled trials has been attributed to trial design, sample size and outcome measures rather than true inefficacy. In anti-neutrophil cytoplasmic antibody-associated vasculitis, rituximab is effective for remission induction and in relapsing disease. However, the optimal long-term re-treatment strategy remains to be determined. Over the next 5 years, evidence will be available regarding the clinical efficacy of these novel therapies, biomarkers and their long-term safety.     

Subcutaneous and intravenous belimumab in the treatment of systemic lupus erythematosus: a review of data on subcutaneous and intravenous administration

Introduction: Loss of B cell tolerance is a hallmark feature of the pathogenesis of Systemic Lupus Erythematosus (SLE). Recent advances in B cell therapy have focused on targeted therapy aimed at inhibiting B cell activation and reducing B cell survival. Belimumab, a human monoclonal antibody against B cell activating factor (BAFF) was licensed in 2011 for the treatment of SLE.

Areas covered: We review the data on the intravenous and subcutaneous formulations of belimumab in the management of patients with SLE. BLISS-52 and BLISS-76 demonstrated the efficacy of intravenous belimumab (10mg/kg) as an add-on therapy in SLE patients with active disease. A recent phase III trial of intravenous belimumab reported similar results in North East Asian patients. Subcutaneous belimumab (200mg/weekly) has demonstrated similar efficacy, safety and tolerability and was approved by the FDA in 2017 for the treatment of active autoantibody positive SLE patients receiving standard therapy.

Expert commentary: Belimumab is generally safe and well tolerated. The most common clinical manifestations of SLE in the clinical trials were arthritis, mucocutaneous disease and serositis. Patients with severe lupus nephritis and central nervous system disease were excluded from these clinical trials.     

Belimumab Therapy in Systemic Lupus Erythematosus

Systemic lupus erythematosus (SLE) is a complex heterogeneous disease, posing challenges to clinical trials. As in other autoimmune diseases, B-lymphocytes play a central role in lupus pathogenesis. The finding that selection and survival of B cells are controlled by a variety of signals, including those provided by the longevity factor BAFF (B-cell activating factor), also called BLyS (B-lymphocyte stimulator), led to preclinical trials that revealed that BAFF represents a promising therapeutic target for human lupus. Belimumab is a fully human monoclonal antibody directed against BAFF. Lessons learned from early clinical trials led to improved methods and success of phase III trials, with recruitment of patients with both clinically and serologically active disease, development and use of a novel SLE Responder Index, and progressive and special restrictions on immunosuppressive and corticosteroid use. These studies offer an attractive blueprint to conduct future clinical trials in SLE. The overall steroid-sparing ability and benefits of belimumab on musculoskeletal and mucocutaneous organ systems suggest that it has an impact on the clinical management of SLE patients. Future directions include studies to determine the role of belimumab in early SLE, as well as in renal or CNS involvement.     

Inhibition of B cell activating factor (BAFF) in the management of systemic lupus erythematosus (SLE)

Introduction: The anti-BAFF monoclonal antibody, belimumab, was approved 5+ years ago by the US Food and Drug Administration for the treatment of adult SLE patients. Although BAFF is now a proven therapeutic target in SLE, the limited clinical efficacy both in the clinical trials setting and in ‘real-life’ experience begs for further therapeutic improvement.

Areas covered: In addition to belimumab, three other BAFF antagonists (atacicept, blisibimod, tabalumab) that biologically differ from belimumab are being or have been evaluated in SLE late-stage clinical trials. Literature search was performed using the search words/phrases, ‘BAFF’, ‘BLyS’, ‘APRIL’, ‘BCMA’, ‘TACI’, ‘BR3’, ‘belimumab’, ‘atacicept’, ‘blisibimod’, ‘tabalumab’, ‘lupus clinical trial’ along with papers from the author’s personal library.

Expert commentary: The reasons underlying current lack of enthusiasm among clinicians for BAFF antagonism are discussed, and speculation if offered regarding the use of a BAFF antagonist as part of sequential therapy and regarding the utility of individual or pairs of BAFF receptors as therapeutic targets.     

Rituximab: a promising therapy in systemic lupus erythematosus

Several trials of new immunologic agents in systemic lupus erythematosus (SLE) have recently been undertaken. Rituximab, a chimeric antibody directed against CD20 on B lymphocytes, has emerged as a promising therapy. Based upon preliminary data, clinical efficacy of rituximab has been documented in both pediatric and adult-onset SLE patients. The specific manifestations reported to be beneficially affected include lupus nephritis, arthralgia/arthritis, serositis, cutaneous vasculitis, mucositis, rashes, fatigue and neurologic symptoms. Although rituximab's mechanisms of action are incompletely understood, the effects of rituximab are likely mediated by antibody-dependent cell-mediated cytotoxicity and the induction of apoptosis. The resultant repopulation of B cells, alteration of abnormal B cell homeostasis and down-regulation of co-stimulatory molecules on both B and T cells all likely contribute to clinical efficacy. Good tolerability of rituximab is reported with rare serious side effects. The positive response to rituximab verifies a central role for B cells in SLE. This article highlights the clinical experience of rituximab therapy in both pediatric and adult-onset SLE. These data suggest a promising role for rituximab in the treatment of SLE. Further controlled trials and long-term outcome studies are imperative to further define its clinical application and to improve the care of patients.     

Spotlight on Rituximab in Non-Hodgkin Lymphoma and Chronic Lymphocytic Leukemia

Rituximab (MabThera, Rituxan is an anti-CD20 monoclonal antibody that induces lysis and apoptosis of normal and malignant human B cells, and sensitizes malignant B cells to the cytotoxic effect of chemotherapy. In phase III trials in patients with indolent or aggressive B-cell non-Hodgkin lymphoma (NHL), intravenous rituximab in combination with chemotherapy was more effective as first- or second-line therapy than chemotherapy alone in terms of tumor remission and patient survival. Likewise, in patients with chronic lymphocytic leukemia (CLL), rituximab in combination with chemotherapy appeared more effective than chemotherapy alone as either first- or second-line treatment. In addition, rituximab maintenance therapy was shown to significantly prolong tumor remission and patient survival in patients with indolent B-cell NHL or CLL. The combination of rituximab with cyclophosphamide, doxorubicin, vincristine and prednisone (CHOP) was cost effective as first-line therapy for advanced-stage diffuse large B-cell NHL compared with CHOP alone. Rituximab, either alone or in combination with chemotherapy, was generally well tolerated in patients with NHL or CLL. Overall, rituximab in combination with chemotherapy, is a valuable option for first- and second-line therapy in patients with advanced-stage indolent or aggressive B-cell NHL, and possibly those with B-cell CLL, and is included in current treatment guidelines for these indications. The drug is also potentially useful as maintenance therapy in patients with indolent B-cell NHL or CLL.     

Novel approaches to therapy for systemic lupus erythematosus: update 2005

This review covers the major advances in the therapeutic potentials related to systemic lupus erythematosus published in Medline between 2000 and February 2005. Controlled, open and Phase I–III trials were included. Anecdotal reports were excluded. Several trials have defined the role of cyclophosphamide, methotrexate, antimalarials, hormonal treatment and mycophenolate mofetil (Cellcept) in the management of systemic lupus erythematosus. The aims of novel biologics for systemic lupus erythematosus are to target the autoimmune disease at different points: B-cell depletion (rituximab [Rituxan®], anti-BLys antibodies [Lymphostat-B?]), inhibition of T–B interaction (rituximab), blockade of cytokines (anti-interleukin-10 antibodies), manipulation of idiotypes (intravenous immunoglobulin), tolerance induction to DNA and immunoglobulin-peptides and peptide therapy (abetimus sodium [Riquent^®]). Low-dose intravenous cyclophosphamide (Euro-Lupus protocol) is as effective as the conventional National Insitutes of Health protocol and is also associated with less toxicity. Stem cell transplantation for severe disease induces remission in most patients, however, the relapse rate in a third of patients and the associated morbity and mortality restricts its use to selected patients with life-threatening disease. Intravenous immunoglobulin, although utilized in open trials, is effective and safe for various manifestations of systemic lupus erythematosus. Major advances have been associated with mycophenolate mofetil and rituximab. Mycophenolate mofetil is effective for induction and maintenance therapy of lupus proliferative glomerulonephritis and is associated with fewer adverse events than monthly intravenous cyclophosphamide. Rituximab is a promising agent, and although its utilization is presently limited, it appears to be effective for lupus patients with severe disease.     

Refractory lupus nephritis: When,why and how to treat

Refractory lupus nephritis indicates an inadequate response to lupus nephritis therapy. It implies persisting or worsening disease activity despite therapy, but the definition is complicated by the parameters of response, proteinuria and renal function, that do not discriminate clearly between activity and irreversible damage. Understanding the causes of refractory disease and developing treatment strategies is important because these patients are more likely to develop poor outcomes, especially end stage renal disease. This review explores current concepts and definitions of refractory disease and summarises treatment approaches that have been used in observational cohort studies and case series. We highlight the importance of optimising adherence to the prescribed immunosuppressive and supportive measures and avoidance of diagnostic delay. Treatment options include higher dose glucocorticoid, switching between cyclophosphamide and mycophenolate acid derivates, or addition of rituximab, the latter potentially in combination with belimumab. Less evidence supports extracorporeal treatment (plasma exchange or immunoadsorption), calcineurin inhibitors (cyclosporine A or tacrolimus), intravenous immunoglobulin and stem cell transplantation. Improvements in understanding what refractory disease is and how definitions can be integrated into treatment pathways has the potential to enhance lupus nephritis outcomes.     

Belimumab Efficacy is ‘Mild’ but Market Potential Still Great

Speaking for the inThought Expert Discussion Series in February, Dr George Tsokos mirrored the opinion of many lupus thought leaders: Human Genome Sciences (HGS) and GlaxoSmithKline’s (GSK) belimumab (Benlysta®) was likely to be approved by the US FDA and, despite modest efficacy, will be used by a large proportion of lupus patients. Dr Tsokos praised HGS and GSK’s clinical trial program for belimumab, noting that huge trials and unique trial endpoints were needed to demonstrate the drug’s efficacy, allowing it to succeed where so many other lupus drugs have failed. Still, belimumab’s trial design may not become standard in future lupus trials — questions about identification of appropriate lupus patients with active disease, trial endpoints, and subgrouping lupus patients remain. Although Dr Tsokos does not expect other agents currently being tested in lupus trials to be significantly more efficacious than belimumab, his research suggests that significantly better results could be obtained using agents targeting interleukin-17, spleen tyrosine kinase (SYK), and calcium/calmodulin-dependent protein kinase type IV (CaMKIV). In line with Dr Tsokos’ comments and consistent with inThought’s outlook for belimumab, the US FDA granted approval for belimumab in March 2011, making it the first new lupus drug to be approved in more than 50 years. inThought projects US sales of $1.1 billion for belimumab by 2017.     

Targeting BAFF and APRIL in systemic lupus erythematosus and other antibody-associated diseases

The B cell-stimulating molecules, BAFF (B cell activating factor) and APRIL (a proliferation-inducing ligand), are critical factors in the maintenance of the B cell pool and humoral immunity. In addition, BAFF and APRIL are involved in the pathogenesis of a number of human autoimmune diseases, with elevated levels of these cytokines detected in the sera of patients with systemic lupus erythematosus (SLE), IgA nephropathy, Sjögren's syndrome, and rheumatoid arthritis. As such, both molecules are rational targets for new therapies in B cell-driven autoimmune diseases, and several inhibitors of BAFF or BAFF and APRIL together have been investigated in clinical trials. These include the BAFF/APRIL dual inhibitor, atacicept, and the BAFF inhibitor, belimumab, which is approved as an add-on therapy for patients with active SLE. Post hoc analyses of these trials indicate that baseline serum levels of BAFF and BAFF/APRIL correlate with treatment response to belimumab and atacicept, respectively, suggesting a role for the two molecules as predictive biomarkers. It will, however, be important to refine future testing to identify active forms of BAFF and APRIL in the circulation, as well as to distinguish between homotrimer and heteromer configurations.

In this review, we discuss the rationale for dual BAFF/APRIL inhibition versus single BAFF inhibition in autoimmune disease, by focusing on the similarities and differences between the physiological and pathogenic roles of the two molecules. A summary of the preclinical and clinical data currently available is also presented.     

B cell immunotherapy in autoimmunity--2010 update

B cells play important roles in normal immunity and human disease. While much has been learned from elegant studies utilizing genetically modified mice or with immunotherapy in normal and in autoimmune mice, we are merely at the start of learning about the mechanism(s) by which B cells contribute to human autoimmune disease. Here, I will review the most recent insights obtained with immunomodulatory therapies in human disease highlighting the clinical and immunological lessons we have learned with B cell depleting (e.g., rituximab) and immunomodulatory (e.g., BAFF/BLys neutralization through belimumab) therapies.     

Epratuzumab for the treatment of systemic lupus erythematosus

Introduction: Systemic lupus erythematosus (SLE) is a multi-system autoimmune disease. There are three drugs licensed for the treatment of lupus: corticosteroids, hydroxychloroquine and belimumab. Immunosuppressants such as azathioprine, methotrexate and mycophenolate are also used. Despite these treatments there is still considerable morbidity. New treatments are needed for the management of active lupus. Epratuzumab a humanized IgG1 monoclonal antibody that targets CD22 resulting in selective B cell modulation that has been considered a potential treatment for SLE.

Areas covered: Summary of the relevant pathogenesis and disease activity measurements used in SLE patients, current treatments and unmet needs in SLE, pharmacokinetics and pharmacodynamics of epratuzumab therapy, and a summary of the 7 clinical trials that have investigated the efficacy and safety of epratuzumab in SLE.

Expert commentary: It is not clear why trials have failed to demonstrate efficacy but high placebo response rates from optimisation of standard of care and a sub-optimal dosing regimen may have played a role. Post-hoc analysis suggested that there may be subgroups that did respond, such as anti-SSA positive patients with features of Sjogren’s syndrome. Further research is needed to explore this and other potential sub-groups that might respond.     

Role of anti-CD20 monoclonal antibody in association with immunomodulatory agents

Chimeric monoclonal anti-CD20 antibody (Rituximab) has been associated with immunomodulatory agents such as interferon alpha, interleukin-2, interleukin-12, G-CSF, GM-CSF and anti-CD22 humanized monoclonal antibody (Epratuzumab). Synergy with interferon is clearly demonstrated increasing complete response rate and response duration. Other associations are promising but must be tested in randomized prospective trials versus rituximab alone, probably in indolent lymphomas where chemotherapy could be avoided.     

The 2018 pipeline of targeted therapies under clinical development for Systemic Lupus Erythematosus: a systematic review of trials

Currently, Systemic Lupus Erythematosus (SLE) therapies range from antimalarials to glucocorticoids, in addition to immunosupressive agents or biologics such as rituximab or belimumab, when needed. Several unmet needs remain in the treatment SLE and more targeted drugs with improved safety profiles are expected. Based on recent advances in the understanding of the complex pathogenesis of SLE, several targeted treatments are currently assessed in clinical trials. In this study, we performed a systematic review of all targeted therapies under clinical development in SLE in 17 online registries of clinical trials. The search yielded a total of 1140 trials, from which we identified 74 targeted therapies for SLE. Those treatments target inflammatory cytokines, chemokines, or their receptors (n?=?17), B cells or plasma cells (n?=?17), intracellular signalling pathways (n?=?10), T/B cells costimulation molecules (n?=?8), interferons (n?=?7), plasmacytoid dendritic cells (pDC) (n?=?3), as well as various other targets (n?=?12). Not all these candidate drugs will reach phase III, but the broad spectrum of drugs being investigated may satisfy the urgent need for improved lupus medications. The identification of biomarkers that would allow adequate prediction of response-to-therapy remains high, but when solved will allow a more rationale selection of the optimal pharmacological agent at the patient level.     

Treatment options for severe lupus nephritis

Renal involvement in systemic lupus erythematosus is a common complication that significantly worsens morbidity and mortality. Landmark trials conducted by the National Institutes of Health established cyclophosphamide as the mainstay of therapy. Since then, the prognosis of patients with lupus nephritis has markedly improved, and 10-year survival rates now surpass 75%.These superior outcomes have come at the expense of adverse events such as serious infections and gonadal failure in a significant number of patients,and the relapsing nature of the disease continues to pose a problem. For thesereasons, new treatment protocols, such as mycophenolate mofetil induction or sequential therapies using azathioprine or mycophenolate mofetil in the maintenance phase, have been developed in recent years with the goal to maintain remission and reduce adverse events. In addition, ongoing research into the pathogenesis of lupus nephritis has confirmed the importance of B and T cell activation, leading to the identification of potential new therapeutic targets. This article discusses established and novel treatment options for patients with severe lupus nephritis corresponding to WHO classes III, IV, and V withIII or V with IV.     

Abetimus: Abetimus sodium,LJP 394

Abetimus [Abetimus sodium, LJP 394, Rentol, Riquent] is a synthetic Toleragen molecule consisting of four double-stranded oligodeoxyribonucleotides attached to nonimmunogenic polyethylene glycol, a proprietary carrier platform. It was originated by La Jolla Pharmaceuticals. Abetimus is an immunomodulating agent that induces tolerance in B cells directed against double-stranded DNA (dsDNA). It does this by cross-linking surface antibodies. These antibodies are thought to be responsible for lupus nephritis, a chronic kidney disease that develops in patients with systemic lupus erythematosus. A phase III trial of abetimus was completed in December 2002. La Jolla Pharmaceuticals previously established two licensing agreements for abetimus, which have since been terminated. One of the agreements was with Leo Pharmaceutical Products of Denmark. The company was licensed rights to abetimus covering Europe and the Middle East. The other agreement was with Abbott Laboratories. Abbott returned all rights to abetimus to La Jolla Pharmaceuticals in September 1999 based on the results of an analysis of the phase II/III trial of abetimus in lupus patients with a history of renal disease. A phase III trial, named "PEARL" (Program Enabling Antibody Reduction in Lupus), has been conducted in the US in patients with lupus nephritis. It enrolled 317 patients with a history of lupus who were treated with a weekly dose of abetimus 100mg or placebo. The trial was completed in December 2002 and preliminary results were reported in February 2003. PEARL was designed to determine whether abetimus can significantly delay renal flares and delay the need for treatment with high-dose corticosteroids and/or cyclophosphamide in patients with high affinity IgG antibodies to the double-stranded oligonucleotide epitope in abetimus. Patients with high-affinity antibodies, were selected using a surface plasmon resonance (SPR)-based pharmacoproteonomics assay provided by Biacor International. Following the completion of PEARL in December 2002, La Jolla Pharmaceuticals initiated an on-going, open-label, follow-on trial. All patients who had completed PEARL were eligible to enroll and receive weekly treatment with abetimus. However, in April 2003, La Jolla Pharmaceuticals announced that it was closing this trial, which was designed to collect additional long-term safety data, to conserve resources for the continued development of the drug. Previously, La Jolla Pharmaceuticals and Abbott initiated a phase II/III trial of abetimus in more than 200 patients with lupus nephritis. However, this trial was discontinued in May 1999 because the primary end-point (time to renal flare) was much shorter than expected. After the trial was halted, further analysis of trial data using a new blood test to measure the strength of the binding between abetimus and a patient's antibodies to dsDNA was conducted. The additional analysis showed that the number of renal flares in the high-affinity patients (responders) treated with abetimus was less than half of the number of renal flares in high-affinity patients treated with placebo. Responders also showed a significant reduction in the use of high-dose corticosteroids and cyclophosphamide. Being able to screen patients to identify those likely to respond to therapy lead La Jolla Pharmaceuticals to initiate PEARL after Abbott's withdrawal from the drug. It is believed that screening patients will help increase the cost-effectiveness of clinical development. In September 2000, the US FDA granted orphan drug status for abetimus in the treatment of lupus nephritis. The European Commission followed suit in November 2001, granting orphan drug status for abetimus in the EU.