B cell non-Hodgkin's lymphoma: rituximab safety experience

A substantial body of data supports use of rituximab as first-line and maintenance therapy for the treatment of indolent non-Hodgkin's lymphoma. With 7 years of postmarketing surveillance experience and more than 370,000 patient exposures, the safety profile of rituximab is well defined. Several multicenter trials suggest that infusion reactions associated with rituximab administration are well characterized and generally associated with the first infusion; toxicity is reduced with subsequent doses. Since some adverse events are related to circulating tumor loads of non-Hodgkin's lymphoma, fewer events are anticipated in rheumatoid arthritis. Low infection rates in oncology would indicate similar safety in patients with rheumatoid arthritis.     

B cell targeted therapies

Although the precise pathogenesis of rheumatoid arthritis (RA) remains unclear, many cell populations, including monocytes, macrophages, endothelial cells, fibroblasts and B cells, participate in the inflammatory process. Ongoing research continues to evaluate the critical roles played by B cells in sustaining the chronic inflammatory process of RA. These findings have contributed to the development of targeted therapies that deplete B cells, such as rituximab, as well as inhibitors of B lymphocyte stimulation, such as belimumab. In a phase I trial, belimumab treatment significantly reduced CD20+ levels in patients with systemic lupus erythematosus. Phase I and phase II trials of rituximab found that rituximab plus methotrexate achieved significantly better American College of Rheumatology 50% responses for patients with RA than those patients receiving monotherapy with methotrexate. These clinical trial data present promising evidence for B cell targeted therapies as future therapeutic options for RA.     

B-cell depletion for rheumatic diseases: where are we?

Immune system dysfunction is common to rheumatic disorders, with rheumatoid arthritis (RA) and systemic lupus erythematosus (SLE) being classic examples. Altered development and function of B cells may play a prominent role. B-cell abnormalities also occur in other rheumatic diseases, eg, Sjogren's syndrome, Behcet's disease, antineutrophil cytoplasmic antibody (ANCA)-associated vasculitis, and dermatomyositis. Hence, B-cell depletion has been investigated as a therapeutic option. Clinical trials in RA and SLE have shown that rituximab, an anti-CD20 monoclonal antibody, can profoundly reduce disease activity and is generally well tolerated. Reports of rituximab treatment for ANCA-associated vasculitis and dermatomyositis are also promising. These encouraging results validate the strategy of B-cell depletion in various rheumatic diseases. B-cell depletion with rituximab is under study in larger clinical trials for the purposes of regulatory approval to define more closely its place in RA and SLE treatment paradigms, and smaller clinical trials are ongoing or planned in associated inflammatory diseases.     

Differential effects on BAFF and APRIL levels in rituximab-treated patients with systemic lupus erythematosus and rheumatoid arthritis

The objective of this study was to investigate the interaction between levels of BAFF (B-cell activation factor of the tumour necrosis factor [TNF] family) and APRIL (a proliferation-inducing ligand) and B-cell frequencies in patients with systemic lupus erythematosus (SLE) and rheumatoid arthritis (RA) treated with the B-cell-depleting agent rituximab. Ten patients with SLE were treated with rituximab in combination with cyclophosphamide and corticosteroids. They were followed longitudinally up to 6 months after B-cell repopulation. Nine patients with RA, resistant or intolerant to anti-TNF therapy, treated with rituximab plus methotrexate were investigated up to 6 months after treatment. The B-cell frequency was determined by flow cytometry, and serum levels of BAFF and APRIL were measured by enzyme-linked immunosorbent assays. BAFF levels rose significantly during B-cell depletion in both patient groups, and in patients with SLE the BAFF levels declined close to pre-treatment levels upon B-cell repopulation. Patients with SLE had normal levels of APRIL at baseline, and during depletion there was a significant decrease. In contrast, patients with RA had APRIL levels 10-fold higher than normal, which did not change during depletion. At baseline, correlations between levels of B cells and APRIL, and DAS28 (disease activity score using 28 joint counts) and BAFF were observed in patients with RA. In summary, increased BAFF levels were observed during absence of circulating B cells in our SLE and RA patient cohorts. In spite of the limited number of patients, our data suggest that BAFF and APRIL are differentially regulated in different autoimmune diseases and, in addition, differently affected by rituximab treatment.     

利妥昔单抗联合化疗治疗弥漫型大B细胞淋巴瘤患者的临床研究

目的:探讨利妥昔单抗与化疗相结合治疗弥漫型大B细胞淋巴瘤(diffuse large Bcelllymphoma,DLBCL)患者的可行性。方法:选取2002年1月至2011年5月我院收治的84例CD20阳性的DLBCL患者,采用利利妥昔单抗与化疗相结合的方法治疗,对其疗效及安全性进行评价,并对其影响因素进行分析。结果:有56例患者治疗艹6个周期,占66.67%;有28例患者治疗6个周期,占33.33%。84例患者治疗的总有效率为83.33%。其中,初治组的总有效率为91.67%,明显高于复治组的62.5%,差异有统计学意义(P0.05)。红细胞沉降率、国际预后指数评分、是否为初治、是否存在B症状以及利妥昔单抗的治疗周期等变量成为影响治疗效果的独立危险因素(P0.05)。随访5年,治疗后第l年、2年、3年和5年患者的生存率分别为88.1%(74/84)、72.62%(61/84)、60.71%(51/84)、60.71%(51/84)。国际预后指数评分、利妥昔单抗的治疗周期以及治疗效果等变量是影响患者生存的独立危险因素(P0.05)。结论:对于弥漫型大B细胞淋巴瘤患者尤其是对初治患者而言,利妥昔单抗联合化疗治疗具有更好的治疗效果,临床应用时不会加重患者的不良反应。     

The shaving reaction: rituximab/CD20 complexes are removed from mantle cell lymphoma and chronic lymphocytic leukemia cells by THP-1 monocytes

Clinical investigations have revealed that infusion of immunotherapeutic mAbs directed to normal or tumor cells can lead to loss of targeted epitopes, a phenomenon called antigenic modulation. Recently, we reported that rituximab treatment of chronic lymphocytic leukemia patients induced substantial loss of CD20 on B cells found in the circulation after rituximab infusion, when rituximab plasma concentrations were high. Such antigenic modulation can severely compromise therapeutic efficacy, and we postulated that B cells had been stripped (shaved) of the rituximab/CD20 complex by monocytes or macrophages in a reaction mediated by FcgammaR. We developed an in vitro model to replicate this in vivo shaving process, based on reacting rituximab-opsonized CD20(+) cells with acceptor THP-1 monocytes. After 45 min at 37 degrees C, rituximab and CD20 are removed from opsonized cells, and both are demonstrable on acceptor THP-1 cells. The reaction occurs equally well in the presence and absence of normal human serum, and monocytes isolated from peripheral blood also promote shaving of CD20 from rituximab-opsonized cells. Tests with inhibitors and use of F(ab')(2) of rituximab indicate transfer of rituximab/CD20 complexes to THP-1 cells is mediated by FcgammaR. Antigenic modulation described in previous reports may have been mediated by such shaving, and our findings may have profound implications for the use of mAbs in the immunotherapy of cancer.     

B淋巴细胞表面分子靶向治疗类风湿关节炎的研究进展

类风湿关节炎(rheumatoid arthritis,RA)是一种慢性、系统性的自身免疫性疾病,迄今病因尚不明确,且缺乏针对其安全有效的治疗药物.由于B淋巴细胞在RA致病机制中的重要作用,近年来不断有针对B淋巴细胞上不同靶点的治疗药物推出.这些B淋巴细胞靶向生物制剂包括针对CD20分子的抗CD20单克隆抗体,如rituximab、ocrelizumab和ofatumumab等;针对B淋巴细胞刺激因子(B lymphocyte stimulator,BLyS)及其受体的belimumab和atacicept等以及处于初期研究阶段的抗CD22单克隆抗体和B、T淋巴细胞之间CD40/CD40L共刺激反应阻断剂等.上述靶向制剂的疗效在对RA及其动物模型的治疗中得到了证实,提示将B淋巴细胞作为RA治疗靶点是一项非常有前景的治疗策略.     

Short- and long-term effects of anti-CD20 treatment on B cell ontogeny in bone marrow of patients with rheumatoid arthritis

Introduction  

In the present study we evaluated changes in the B cell phenotype in peripheral blood and bone marrow (BM) of patients with rheumatoid arthritis (RA) following anti-CD20 treatment using rituximab.     

Unmet needs in rheumatoid arthritis

Until the pathophysiology/etiology of rheumatoid arthritis (RA) is better understood, treatment strategies must focus on disease management. Early diagnosis and treatment with disease-modifying antirheumatic drugs (DMARDs) are necessary to reduce early joint damage, functional loss, and mortality. Several clinical trials have now clearly shown that administering appropriate DMARDs early yields better therapeutic outcomes. However, RA is a heterogeneous disease in which responses to treatment vary considerably for any given patient. Thus, choosing which patients receive combination DMARDs, and which combinations, remains one of our major challenges in treating RA patients. In many well controlled clinical trials methotrexate and other DMARDs, including the tumor necrosis factor-alpha inhibitors, have shown considerable efficacy in controlling the inflammatory process, but many patients continue to have active disease. Optimizing clinical response requires the use of a full spectrum of clinical agents with different therapeutic targets. Newer therapies, such as rituximab, that specifically target B cells have emerged as viable treatment options for patients with RA.     

Toxic epidermal necrolysis in two rhesus macaques (Macaca mulatta) after administration of rituximab

A 2- and a 7-year-old rhesus macaque developed toxic epidermal necrolysis (TEN) after administration of ritux imab. Rituximab, a chimeric monoclonal antibody (mAb) directed against the CD20 antigen on B lymphocytes, is used to treat certain B cell neoplasias. The macaques were part of a gene therapy study that involved administering an adeno-associated viral vector encoding human factor IX (hFIX) to the animals. Both animals developed antibody against hFIX, which eliminated expression of the protein. Rituximab was administered to deplete the population of B cells producing antibodies against the protein. Two days after treatment, the 7-year-old animal developed erythemic skin lesions that rapidly progressed in severity, resulting in epidermal sloughing and ulceration. Despite aggressive treatment with analgesics, antibiotics, and corticosteroids, the animal had to be euthanized 5 days later. The 2-year-old macaque had no reaction to the initial dose of rituximab and received a second infusion 2 weeks later. Two days after drug administration, skin lesions developed; aggressive analgesic, antibiotic, and corticosteroid treatment was initiated, and the lesions resolved. A third rituximab dose was given approximately 2 months after the second. Skin lesions developed and were treated. The animal made a full recovery. In both cases, skin biopsies were taken and histopathologic findings were consistent with TEN. A severe, life-threatening condition, TEN manifests as an intolerance reaction in the skin. The most common cause of TEN is a response to previous drug administration. To our knowledge, this condition has not been reported in association with rituximab administration in macaques.     

Effect of prednisone on type I interferon signature in rheumatoid arthritis: consequences for response prediction to rituximab

IntroductionElevated type I interferon (IFN) response gene (IRG) expression has proven clinical relevance in predicting rituximab non-response in rheumatoid arthritis (RA). Interference between glucocorticoids (GCs) and type I IFN signaling has been demonstrated in vitro. Since GC use and dose are highly variable among patients before rituximab treatment, the aim of this study was to determine the effect of GC use on IRG expression in relation to rituximab response prediction in RA.MethodsIn two independent cohorts of 32 and 182 biologic-free RA patients and a third cohort of 40 rituximab-starting RA patients, peripheral blood expression of selected IRGs was determined by microarray or quantitative real-time polymerase chain reaction (qPCR), and an IFN-score was calculated. The baseline IFN-score was tested for its predictive value towards rituximab response in relation to GC use using receiver operating characteristics (ROC) analysis in the rituximab cohort. Patients with a decrease in disease activity score (∆DAS28) >1.2 after 6 months of rituximab were considered responders.ResultsWe consistently observed suppression of IFN-score in prednisone users (PREDN⁺) compared to non-users (PREDN⁻). In the rituximab cohort, analysis on PREDN⁻ patients (n = 13) alone revealed improved prediction of rituximab non-response based on baseline IFN-score, with an area under the curve (AUC) of 0.975 compared to 0.848 in all patients (n = 40). Using a group-specific IFN-score cut-off for all patients and PREDN⁻ patients alone, sensitivity increased from 41% to 88%, respectively, combined with 100% specificity.ConclusionsBecause of prednisone-related suppression of IFN-score, higher accuracy of rituximab response prediction was achieved in PREDN⁻ patients. These results suggest that the IFN-score-based rituximab response prediction model could be improved upon implementation of prednisone use.     

抗人B淋巴细胞单克隆抗体清除中国恒河猴体内B淋巴细胞效果观察

目的用抗人B淋巴细胞单克隆抗体（利妥昔单抗注射液,Rituximab）通过静脉滴注的方法敲除中国恒河猴体内B淋巴细胞,并观察其敲除效果,为建立B淋巴细胞缺失的恒河猴动物模型提供基础的实验数据。方法选取健康的中国恒河猴两只,静脉滴注抗人B淋巴细胞单克隆抗体,定期采集外周血、腹股沟淋巴结和十二指肠黏膜组织,制备淋巴细胞悬液,应用流式细胞术的方法系统性测定B淋巴细胞及T淋巴细胞亚群的变化。结果静脉滴注利妥昔单抗注射液后24 h,中国恒河猴外周血中B淋巴细胞的缺失即能达到100%,持续约14 d;腹股沟淋巴结中B淋巴细胞在静注后7 d缺失100%;十二指肠黏膜组织中B淋巴细胞在静脉滴注后7 d缺失达到90%,维持28 d。并且在成功敲除B淋巴细胞的情况下,CD4＋T及CD8＋T淋巴细胞无明显波动,维持在一个稳定的水平。结论利妥昔单抗注射液能有效去除中国恒河猴体内B淋巴细胞,为建立B淋巴细胞缺失动物模型奠定基础。     

Interleukin-21 Enhances Rituximab Activity in a Cynomolgus Monkey Model of B Cell Depletion and in Mouse B Cell Lymphoma Models

Rituximab, a monoclonal antibody targeting CD20 on B cells, is currently used to treat many subtypes of B cell lymphomas. However, treatment is not curative and response rates are variable. Recombinant interleukin-21 (rIL-21) is a cytokine that enhances immune effector function and affects both primary and transformed B cell differentiation. We hypothesized that the combination of rIL-21 plus rituximab would be a more efficacious treatment for B cell malignancies than rituximab alone. We cultured human and cynomolgus monkey NK cells with rIL-21 and found that their activity was increased and proteins associated with antibody dependent cytotoxicity were up-regulated. Studies in cynomolgus monkeys modeled the effects of rIL-21 on rituximab activity against CD20 B cells. In these studies, rIL-21 activated innate immune effectors, increased ADCC and mobilized B cells into peripheral blood. When rIL-21 was combined with rituximab, deeper and more durable B cell depletion was observed. In another series of experiments, IL-21 was shown to have direct antiproliferative activity against a subset of human lymphoma cell lines, and combination of murine IL-21 with rituximab yielded significant survival benefits over either agent alone in xenogeneic mouse tumor models of disseminated lymphoma. Therefore, our results do suggest that the therapeutic efficacy of rituximab may be improved when used in combination with rIL-21.     

Subcutaneous versus Intravenous Administration of Rituximab: Pharmacokinetics,CD20 Target Coverage and B-Cell Depletion in Cynomolgus Monkeys

The CD20-specific monoclonal antibody rituximab (MabThera^®, Rituxan^®) is widely used as the backbone of treatment for patients with hematologic disorders. Intravenous administration of rituximab is associated with infusion times of 4–6 hours, and can be associated with infusion-related reactions. Subcutaneous administration of rituximab may reduce this and facilitate administration without infusion-related reactions. We sought to determine the feasibility of achieving equivalent efficacy (measured by endogenous B-cell depletion) and long-term durability of CD20 target coverage for subcutaneously administered rituximab compared with intravenous dosing. In these preclinical studies, male cynomolgus monkeys were treated with either intravenous rituximab or novel subcutaneous formulation of rituximab containing human recombinant DNA-derived hyaluronidase enzyme. Peripheral blood samples were analyzed for serum rituximab concentrations, peripheral B-cell depletion, and CD20 target coverage, including subset analysis according to CD21+ status. Distal lymph node B-cell depletion and CD20 target coverage were also measured. Initial peak serum concentrations of rituximab were significantly higher following intravenous administration than subcutaneous. However, the mean serum rituximab trough concentrations were comparable at 2 and 7 days post-first dose and 9 and 14 days post-second dose. Efficacy of B-cell depletion in both peripheral blood and distal lymph nodes was comparable for both methods. In lymph nodes, 9 days after the second dose with subcutaneous and intravenous rituximab, B-cell levels were decreased by 57% and 42% respectively. Similarly, levels of peripheral blood B cells were depleted by >94% for both subcutaneous and intravenous dosing at all time points. Long-term recovery of free unbound surface CD20 levels was similar, and the duration of B-cell depletion was equally sustained over 2 months for both methods. These results demonstrate that, despite initial peak serum drug level differences, subcutaneous rituximab has similar durability, pharmacodynamics, and efficacy compared with intravenous rituximab.     

Rituximab and abatacept but not tocilizumab impair antibody response to pneumococcal conjugate vaccine in patients with rheumatoid arthritis

Introduction

The objective of the study was to investigate the impact of newer biologic treatments including rituximab, abatacept and tocilizumab on antibody response following pneumococcal vaccination using a 7-valent conjugate vaccine in patients with established rheumatoid arthritis (RA).

Methods

Patients with RA receiving rituximab, abatacept or tocilizumab as monotherapy or combined with methotrexate (MTX) participated in the study. Specific IgG antibodies against 23F and 6B serotypes were measured at vaccination and 4 to 6 weeks after vaccination using standardised ELISA. Geometric mean antibody levels (GML) were calculated. Antibody response (AR) was defined as the ratio between post- and pre-vaccination antibody levels and a positive antibody response (posAR) was AR ≥2.

Results

In total, 88 patients were enrolled in the study. Of 55 patients treated with rituximab, 26 (46%) were on concomitant MTX. Of patients receiving abatacept (n = 17) and tocilizumab (n = 16) biologic treatment was given in combination with MTX in 13 (76%) and 9 (56%) patients, respectively. Patients treated with rituximab had significantly lower AR compared to those on tocilizumab, as well as compared to previously reported RA patients on MTX and controls (spondylarthropathy patients treated with NSAIDs and/or analgesics). In total, 10.3% of patients on rituximab monotherapy and no patient on rituximab + MTX had posAR for both serotypes. For abatacept and tocilizumab the corresponding figures were 17.6% and 50%.

Conclusion

In this cohort of patients with established RA, treatment with rituximab and abatacept was associated with diminished antibody response but this was most pronounced for rituximab. Pneumococcal conjugate vaccine administrated during ongoing tocilizumab treatment seems to be associated with sufficient antibody response. Pneumococcal vaccination should preferably be encouraged before initiation of rituximab or abatacept treatment.

Trial registration

NCT00828997 and EudraCT EU 2007-006539-29.     

Prostaglandin E2 synthesizing enzymes in rheumatoid arthritis B cells and the effects of B cell depleting therapy on enzyme expression

Introduction

B cells may play an important role in promoting immune activation in the rheumatoid synovium and can produce prostaglandin E₂ (PGE₂) when activated. In its turn, PGE₂ formed by cyclooxygenase (COX) and microsomal prostaglandin E₂ synthase 1 (MPGES1) contributes to the rheumatoid arthritis (RA) pathological process. Therapeutic depletion of B cells results in important improvement in controlling disease activity in rheumatoid patients. Therefore we investigated the expression of PGE₂ pathway enzymes in RA B cells and evaluated the effects of B cell depleting therapy on their expression in RA tissue.

Methods

B cells expressing MPGES1 and COX-2 were identified by flow cytometry in in vitro stimulated and control mononuclear cells isolated from synovial fluid and peripheral blood of RA patients. Synovial biopsies were obtained from 24 RA patients before and at two consecutive time points after rituximab therapy. Expression of MPGES1, COX-1 and COX-2, as well as interleukin (IL)-1β and IL-6, known inducers of MPGES1, was quantified in immunostained biopsy sections using computerized image analysis.

Results

Expression of MPGES1 or COX-2 was significantly upregulated upon stimulation of B cells from blood and synovial fluid while control cells displayed no detectable enzymes. In synovial biopsy sections, the expression of MPGES1, COX-1 or COX-2 was resistant to rituximab therapy at 8 or 16 weeks after start of treatment. Furthermore expression of IL-1β in the synovial tissue remained unchanged, while IL-6 tended to decrease after therapy.

Conclusions

Therapy with B cell depleting agents, although efficient in achieving good clinical and radiographic response in RA patients, leaves important inflammatory pathways in the rheumatoid synovium essentially unaffected.     

Rituximab infusion promotes rapid complement depletion and acute CD20 loss in chronic lymphocytic leukemia

Complement plays an important role in the immunotherapeutic action of the anti-CD20 mAb rituximab, and therefore we investigated whether complement might be the limiting factor in rituximab therapy. Our in vitro studies indicate that at high cell densities, binding of rituximab to human CD20(+) cells leads to loss of complement activity and consumption of component C2. Infusion of rituximab in chronic lymphocytic leukemia patients also depletes complement; sera of treated patients have reduced capacity to C3b opsonize and kill CD20(+) cells unless supplemented with normal serum or component C2. Initiation of rituximab infusion in chronic lymphocytic leukemia patients leads to rapid clearance of CD20(+) cells. However, substantial numbers of B cells, with significantly reduced levels of CD20, return to the bloodstream immediately after rituximab infusion. In addition, a mAb specific for the Fc region of rituximab does not bind to these recirculating cells, suggesting that the rituximab-opsonized cells were temporarily sequestered by the mononuclear phagocytic system, and then released back into the circulation after the rituximab-CD20 complexes were removed by phagocytic cells. Western blots provide additional evidence for this escape mechanism that appears to occur as a consequence of CD20 loss. Treatment paradigms to prevent this escape, such as use of engineered or alternative anti-CD20 mAbs, may allow for more effective immunotherapy of chronic lymphocytic leukemia.     

Early restoration of immune and vascular phenotypes in systemic lupus erythematosus and rheumatoid arthritis patients after B cell depletion

This translational multi‐centre study explored early changes in serologic variables following B lymphocyte depletion by rituximab (RTX) treatment in systemic lupus erythematosus (SLE) and rheumatoid arthritis (RA) patients and investigated in vitro effects on the activity of other immune cells and the vascular endothelium. Eighty‐five SLE patients, seventy‐five RA patients and ninety healthy donors were enrolled. Two additional cohorts of selected SLE and RA patients were treated with RTX for 3 months. Changes in circulating levels of inflammatory mediators, oxidative stress markers and NETosis‐derived bioproducts were evaluated. Serum miRNomes were identified by next‐generation sequencing, and RTX‐induced changes were delineated. Mechanistic in vitro studies were performed to assess activity profiles. Altered inflammatory, oxidative and NETosis‐derived biomolecules were found in SLE and RA patients, closely interconnected and associated to specific miRNA profiles. RTX treatment reduced SLE and RA patients' disease activity, linked to a prominent alteration in those biomolecules and the reversal of altered regulating miRNAs. In vitro studies showed inhibition of NETosis and decline of pro‐inflammatory profiles of leucocytes and human umbilical vein endothelial cells (HUVECs) after B cell depletion. This study provides evidence supporting an early RTX‐induced re‐setting of the pro‐inflammatory status in SLE and RA, involving a re‐establishment of the homeostatic equilibrium in immune system and the vascular wall.     

Dendritic cells and the promise of antigen-specific therapy in rheumatoid arthritis

Rheumatoid arthritis (RA) is a systemic inflammatory disease resulting from an autoimmune response to self-antigens, leading to inflammation of synovial tissue of joints and subsequent cartilage and bone erosion. Current disease-modifying anti-rheumatic drugs and biologic inhibitors of TNF, IL-6, T cells and B cells block inflammation nonspecifically, which may lead to adverse effects, including infection. They do not generally induce long-term drug-free remission or restoration of immune tolerance to self-antigens, and lifelong treatment is usual. The development of antigen-specific strategies in RA has so far been limited by insufficient knowledge of autoantigens, of the autoimmune pathogenesis of RA and of the mechanisms of immune tolerance in man. Effective tolerance-inducing antigen-specific immunotherapeutic strategies hold promise of greater specificity, of lower toxicity and of a longer-term solution for controlling or even preventing RA. This paper reviews current understanding of autoantigens and their relationship to immunopathogenesis of RA, and emerging therapeutics that aim to leverage normal tolerance mechanisms for implementation of antigen-specific therapy in RA.     

B cell depletion in autoimmune disease

The CD20 cell marker appears early in the process of B cell development. In this review we focus on the results of attempts to utilize B cell depletion based on the use of a chimeric monoclonal antibody (MAb) specific for human CD20, rituximab, for the treatment of patients with autoimmune diseases. In 1997, rituximab was approved for the treatment of low-grade B cell non-Hodgkin's lymphoma. Following these encouraging results, rituximab started to be used experimentally in other diseases presumed to be due to B cell pathology. The first autoimmune disease to be treated effectively was chronic idiopathic thrombocytopaenia. More recent success has been demonstrated in patients with rheumatoid arthritis and systemic lupus erythematosus.