Rituximab in the treatment of anti-neutrophil cytoplasm antibody associated vasculitis and systemic lupus erythematosus: past, present and future

Transcription

1 mini review & 2007 International Society of Nephrology Rituximab in the treatment of anti-neutrophil cytoplasm antibody associated vasculitis and systemic lupus erythematosus: past, present and future M Walsh 1,2 and D Jayne 1 1 Department of Renal Medicine, Addenbrooke s Hospital, Cambridge, United Kingdom and 2 Department of Community Health Sciences, University of Calgary, Calgary, Canada Nephritis is the most frequent severe manifestation of anti-neutrophil cytoplasm antibody associated (ANCA) systemic vasculitis (AASV) and systemic lupus erythematosus (SLE) and carries substantial morbidity. Although immunosuppressive medications and glucocorticoids are effective at inducing remission, patients still suffer from high relapse rates and experience significant treatment-related toxicity. Rituximab (RTX), a chimeric antibody directed against CD20, found on B lymphocytes, shows potential as a treatment for both AASV and SLE. Although direct comparisons with standard therapies are currently unavailable, patients in several studies of refractory and relapsing disease have achieved a remission despite the failure of standard therapies. These reports are supported by several lines of experimental evidence that underlie the rationale for using targeted B-cell therapies and have improved our understanding of the pathogenesis of these complex diseases. Future randomized control trials and long-term follow-up studies are required to confirm the role of RTX and other B-cell targeting therapies in AASV and SLE. Kidney International (2007) 72, ; doi: /sj.ki ; published online 4 July 2007 KEYWORDS: vasculitis; systemic lupus erythematosus; lupus nephritis; rituximab; monocolonal antibody Correspondence: M Walsh, Box 118, Vasculitis and Lupus Office, Renal Medicine, Addenbrooke s Hospital, Hills Road, Cambridge CB2 2QQ, UK. dj106@cam.ac.uk Received 26 March 2007; revised 19 April 2007; accepted 1 May 2007; published online 4 July 2007 Anti-neutrophil cytoplasm antibody (ANCA) associated systemic vasculitis (AASV) and systemic lupus erythematosus (SLE) with nephritis are characterized as small vessel inflammatory diseases with multisystem involvement and autoantibody production. Both diseases have a dismal natural history with 5-year survival rates between 0 and 20% left untreated and end-stage renal disease, a common complication. The current accepted standard of care for both diseases is glucocorticoids and an immunosuppressive, most often cyclophosphamide. This has improved 5-year survival rates to between 70 and 90%. Despite this remarkable improvement in survival, up to 20% of patients with these diseases do not respond to standard drug regimens and of those who do respond, up to 50% have relapses of their disease. This is further complicated by the toxicity of both glucocorticoids and cyclophosphamide. In particular, high infection rates, gonadal toxicity, and malignancy are of concern. Given these factors, newer treatments are clearly indicated and ideally will provide longer lasting remission and a less toxic adverse event profile. B-cell depleting therapies, such as rituximab (RTX), have been considered as a potential treatment for AASV and SLE. We will review the rationale for this treatment, the current state of evidence for its efficacy and toxicity, and highlight areas for future research with B-cell depleting therapies and other B-cell targeted therapies. THE RATIONALE FOR TARGETED B-CELL THERAPY B cells occupy a central role in the normal immune system (Figure 1). Within the context of autoimmunity, T-cell autoreactivity, an important component of inflammatory autoimmune diseases, is supported by B cells, 1 either through antigen presentation or co-stimulation. Unlike dendritic cells, B cells are antigen specific and capable of clonal expansion amplifying immune responses. T-cell-derived cytokines (e.g. BLyS and APRIL) modify B-cell activity via surface receptors (e.g. TACI). Following activation and maturation, B cells traffic to sites of 676 Kidney International (2007) 72,

2 Plasma cell IL-10, interferon α B cell Costimulatory ligand-receptor Antigen presenting (dendritic) cell MHC/antigen-TCR TACI 1 BLyS, 2 APRIL Auto antibodies T cell Organ damage Figure 1 Central role B cells in the development of autoimmune target organ damage. (1) Auto-antigen stimulation of T cells by antigen presenting cells (APC) or B cells via MHC/antigen T-cell receptor interactions in conjunction with co-stimulation by CD80(86)-CD28 or CD40-CD40L interactions; (2) T-cell secretion of cytokines such as BLyS or APRIL, which, via cell surface receptors like TACI, induce B-cell maturation and differentiation to plasma cells; (3) B-cell secretion of cytokines such as interleukin-10 and interferon-a induce differentiation of APC to monocytes; (4) B-cell clonal proliferation after exposure to autoantigens; (5) Neutrophil activation and recruitment in peripheral tissues by cytokines; (6) B-cell differentiation to autoantibody-producing plasma cells. inflammation and recruit inflammatory cells or differentiate to plasmablasts. Thus, B-cell activity may be influenced by targeting B-cell stimulatory cytokines, B-cell surface receptors, or via B-cell depletion. Although plasma cells are not affected directly by B-cell-targeted therapies, depleting B cells, which may differentiate into autoantibody-producing plasma cells or alter circulating plasmablast function, make B cells a rational target. 2 Thus, while B- cell depleting therapy specifically removes B cells and not other cells of the immune system, the effects of B-cell depletion or modifying B-cell activity may have widespread immunologic effects. Specific evidence for the roles of B cells in AASV and SLE can also be found. In AASV, abnormal B-cell clusters adjacent to proteinase 3 (PR3)-ANCA-positive cells and plasma cells have been observed in nasal biopsies. 3 Additionally, the regulation of T lymphocytes, known to be important in AASV, is interdependent on B-cell function. 4,5 In SLE, abnormalities of B-cell interactions with antigenpresenting cells and B-cell hyperactivity may drive the autoimmune process. 6,7 THE EVIDENCE FOR RITUXIMAB RTX is an IgG1 k mouse/human chimeric monoclonal antibody directed against the B-cell surface receptor CD20. It was licensed in 1997 for use in non-hodgkin lymphoma and over patients have now been treated with RTX for this indication. RTX is now also licensed for rheumatoid arthritis. CD20 is a cell surface receptor stably expressed on immature and mature B cells but not on plasma cells. Binding of RTX to CD20 induces apoptosis, antibody-dependent cellular cytotoxicity, and complement-dependent cytotoxicity. In SLE, the efficacy of B-cell depletion by RTX may depend in part on the FcgRIIIa genotype of the patient. 8 Patient selection and basis for studies As an experimental therapy, published reports of RTX use in AASV and SLE are limited to retrospective case series and small prospective open-label trials of patients treated with RTX for refractory or frequently relapsing disease. The clinical experience with RTX in both AASV and SLE is much more extensive than the published experience and the probability of a positive publication bias must be considered in the review of this body of literature. Additionally, these studies generally occur in referral centers with experience in refractory AASV/SLE and the administration of immunotherapies. Furthermore, the effect of RTX with respect to long-term outcomes, sustained remissions of disease, and the prevention of hard end points, such as death and renal failure, are not addressed in the current body of literature. Lastly, all the studies mentioned below included patients with renal involvement but not necessarily rapidly progressive nephritis or severe renal dysfunction. In SLE studies, only two are dedicated to proliferative lupus nephritis (PLN). 9,10 With these caveats in mind, the results of RTX studies in these difficult to treat patients have encouraging biological and clinical results. The results of published case series and open-label trials are summarized for AASV and SLE in Tables 1 and 2, respectively. Therapeutic protocols Experience with RTX in lymphoma has standardized four weekly doses of 375 mg/m 2, while experience in rheumatoid arthritis has developed a protocol of two 1000 mg doses biweekly. Protocols for administering the RTX to patients with AASV and SLE have varied between lymphoma doses and rheumatoid doses. One small dose-escalating study varied the total dose given to patients with SLE between 100 and 1500 mg/m 2, 11 and one study of AASV used a dose of 375 mg/m 2 every 4 weeks. 12 No obvious differences in either efficacy or toxicity have been demonstrated between the lymphoma and rheumatoid protocols although direct comparisons are lacking. The majority of studies cited below utilized traditional lymphoma dosing protocols with a few using rheumatoid protocols. There is little guidance on the use of RTX alone, with glucocorticoids or with glucocorticoids and immunosuppressive Kidney International (2007) 72,

3 Table 1 Summary of published reports of rituximab use in anti-neutrophil cytoplasm antibody associated systemic vasculitis Study No. of patients (no. of nephritis) Dose of RTX Aries (2006) 8 (2) 375 mg/m 2 every 4 weeks 4 Concomitant treatments Remission (nephritis) B-cell depletion ANCA serology Relapse CYC, MMF, MTX 2/8 (1/2) 8/8 0/8 became negative; no significant change in titer Eriksson (2005) 9 (7) 500 mg weekly 4 or MMF, AZA, CYC 8/9 complete, 500 mg every other 1/9 partial (7/7) week 2 9/9 0/7 became negative; no significant change in titer 2 (12 and 13 Keogh (2005) 11 (4) 375 mg/m 2 weekly 4 PLEX for nephritis 10/11 complete, 1/11 partial (4/4) 11/11 8/11 became negative; 2 (7 and 12 Keogh (2006) 10 (7) 375 mg/m 2 weekly 4 10/10 complete (7/7) 10/10 6/10 became negative; Omdal (2005) 3 (3) 375 mg/m 2 weekly 4 3/3 complete 3/3 0/3 became negative; 1 (9 3/3 (8, 13, and 15 Smith (2006) 11 (6) 375 mg/m 2 weekly 4; 1 g every other MMF 9/11 complete, 1/11 partial week 2 for retreatment 11/11 6/10 became negative; 6/10 (median 16.5 Stasi (2006) 10 (6) 375 mg/m 2 weekly 4 9/10 complete, 1/10 partial 10/10 8/10 became negative; 3/10 (12, 16, and 24 ANCA, anti-neutrophil cytoplasm antibody; AZA, azathioprine; CYC, cyclophosphamide;, glucocorticoids; MMF, mycophenolate mofetil; MTX, methotrexate;, not reported; PLEX, plasma exchange; RTX, rituximab. Table 2 Summary of published reports of rituximab use in systemic lupus erythematosus Study No. of patients (no. of nephritis) Dose of RTX Concomitant treatments Remission (nephritis) B-cell depletion Anti-dsDNA serology Relapse Gottenberg 13 (4) 375 mg/m 2 every 4 weeks 1 4 7/13 complete, 2/13 partial (2/4) 4 became negative; 2 decreased; 3 no change, and 2 increased; 2 missing data 2/9 (9 and 15 Leandro 24 (17) 500 mg every other week 2or 1000 mg every other week 2 CYC 24/24 improved (17/17 improved) 23/24 Statistically significant decrease reported 7/24 (timing ) Looney 18 (6) 100 mg/m 2 1or 375 mg/m 2 1or 375 mg/m 2 weekly 4 AZA, MTX, HCQ 13/18 improved (4/6 improved) Sfikakis 10 (10) 375 mg/m 2 weekly 4 5/10 complete, 3/10 partial (8/10) Smith 11 (6) 375 mg/m 2 weekly 4 MMF, AZA 6/11 complete, 5/11 partial (6/6) 11/17 No significant change reported 9/10 Statistically significant decrease reported 11/11 No significant change reported (4/11 with improvement subsequently worsened) 3/8 (5, 5, and 8 7/11 (median 12 Vigna-Perez 22 (22) mg every other week 2 MMF, MTX, AZA 5/22 complete, 7/22 partial, 18/22 improved (12/22) 20/22 No significant change reported ANCA, anti-neutrophil cytoplasm antibody; AZA, azathioprine; CYC, cyclophosphamide;, glucocorticoids; HCQ, hydroxychloroquine; MMF, mycophenolate mofetil; MTX, methotrexate;, not reported; RTX, rituximab. 678 Kidney International (2007) 72,

4 medications. The majority of studies considered here used concomitant glucocorticoids and immunosuppressive medications Following treatment with RTX, glucocorticoids were generally tapered as allowed by reductions in clinical symptoms. For patients with AASV and renal involvement, a single study systematically employed concomitant plasma exchange without the use of other immunosuppressive medications. 16 Immunologic response Studies of patients with AASV treated with RTX demonstrate peripheral B-cell depletion universally within 4 weeks of treatment. 13,15 19 The return of peripheral B cells was generally noted to occur within 6 12 months of treatment. ANCA titers were significantly reduced in most studies and dropped below the lower limit of detection in 60 80% of patients in four studies ,19 In two studies, however, no significant changes in ANCA titers were noted despite peripheral B-cell depletion. 12,13 Reductions in ANCA titers were slower than B-cell depletion, as expected, and generally ANCA did not return or begin to rise again until after peripheral B cells began reconstitution. In contrast to the AASV experience, peripheral B-cell depletion is expected but does not occur universally in patients with SLE treated with RTX. No general association between the RTX protocol ( lymphoma vs rheumatoid ) or patient characteristics and the likelihood of peripheral B-cell depletion are apparent. Peripheral B cells returned to measurable levels between 1 and 17 months after treatment. 9,14,15,20 Unlike the autoantibodies of AASV, RTX did not have consistent effects on anti-dsdna antibodies. Two studies show significant reductions in anti-dsdna antibodies, 9,14 one of which was specifically in patients with PLN. 9 All other studies showed inconsistent changes in anti-dsdna antibody titers between patients and no significant overall effect. 10,11,15,20 However, sub-studies specifically aimed at determining antibody responses to RTX frequently show a reduction in autoantibody titers. 9,21 23 A similar change in antimicrobial antibody titers was not demonstrated; a finding which suggests that the turn-over of plasma cells producing autoantibodies is more rapid than those producing microbial antibodies and thus more sensitive to the effects of B-cell depletion. 21 Complement levels generally improved in patients. Several studies have also explored the mechanistic immunologic effects of RTX in patients with SLE. Anolik et al. 24 demonstrated that RTX reversed several abnormalities of B-cell homeostasis and reduced the number of autoreactive memory B cells up to 1 year after treatment with RTX. Downregulation of CD40 and CD80, co-stimulatory molecules for T lymphocytes, after RTX have also been demonstrated and imply possible modification of T lymphocyte function after B-cell depletion. In patients with PLN, RTX has been shown to decrease T-helper cells and improve T-regulatory cell function. 9,10 Clinical response: induction Patients generally experienced a remission of disease after treatment with RTX in these studies. All patients in five out of seven studies with AASV treated with RTX had at least a partial remission. In the six studies with favorable responses, complete remission occurred in 50 out of 54 patients reported. 13,15 19 These patients included 33 with renal involvement of which two were on dialysis at the time of treatment. Remission was obtained by 6 months after treatment in all of these cases. Inflammatory markers such as erythrocyte sedimentation rate and C-reactive protein were noted to decrease in parallel with clinical activity. In a single study of eight patients, only three experienced a reduction of disease activity, one of whom had renal involvement. 12 The disease of patients in this study was largely characterized by refractory retro-orbital granulomas, an uncommon manifestation in patients in other studies and a different dosing schedule of RTX. Four studies of SLE including 64 patients, 11,14,15,20 half of which had PLN, and two studies of 32 patients specifically with PLN 9,10 all demonstrate some improvement in SLE activity. Complete responses did not occur as commonly as in AASV. All six studies, reporting on 96 patients, reported almost all patients had some improvement. Of the four studies reporting complete and partial remissions, 9,10,15,20 within 1 8 months of treatment, 23 of 56 patients had complete remissions and an additional 17 had partial remissions. In those patients with PLN, proteinuria was consistently decreased after treatment with RTX although the course of resolution was sometimes prolonged. 11,15 One study also demonstrated the largest improvements were primarily experienced in musculoskeletal and dermatologic systems. 11 A case series of lupus nephritis proven refractory to cyclophosphamide treatment by biopsy, however, showed improvement with the addition of RTX to cyclophosphamide on subsequent biopsies. 25 These generally positive reports in adult patients are also supported by reports in children with severe manifestations of SLE. 26 Clinical response: relapse and retreatment Relapse after treatment with RTX remains a major concern in both AASV and SLE. In AASV studies, 20 out of 44 patients had a relapse Relapses occurred between 12 and 24 months after treatment. Rising ANCA titers frequently preceded clinical relapses and all but one relapse occurred in patients with at least partial reconstitution of peripheral B cells. 15 In studies of patients with SLE treated with RTX, between 15 and 65% of patients experienced a relapse between 6 and 23 months after treatment (most commonly at approximately 1 year after treatment). 9,15,20 In all but one case, relapse occurred after the reconstitution of peripheral B lymphocytes. 15 Retreatment with RTX is only reported infrequently and its effects and associated toxicity remain largely unknown. However, retreatment of both AASV and SLE with RTX generally appeared efficacious although the duration of B-cell depletion may be slightly shorter. 15 Kidney International (2007) 72,

5 In addition, repeated RTX infusions may be associated with a higher risk of infusion reactions and the development of human anti-chimeric antibodies (HACA) (see Toxicity and side effects below). 27 Toxicity and side effects Toxicity data specific to AASV and SLE is still limited. In related autoimmune inflammatory phenotypes such as rheumatoid arthritis, over 300 patients have been treated in the context of clinical trials with RTX and it was very well tolerated in the short-term data currently available. 28 In the above studies in AASV and SLE, serious infusion reactions were rare. Similarly, serious infections were rarely reported in either condition but there has been concern raised as to the role of rituximab in the rare development of unusual infections, such as progressive multifocal leukoencephalopathy, in patients with SLE. 29 The relative contribution of RTX and previous or ongoing immunosuppressive medications is also unknown. Additionally, many studies of RTX, in AASV, SLE, and rheumatoid arthritis, demonstrate reductions in circulating immunoglobulins ranging from mild to quite severe. 11,15 17,19 Additionally, infective risks may be increased due to an impaired secondary humoral response (e.g. immunizations). 30 There has also been concern over the use of RTX repeatedly due to the antigenicity of its murine component. This may increase the chances of serum sickness or hypersensitivity reactions. 31 Repeat doses may also induce high levels of human antibodies directed against RTX, which could neutralize the actions of RTX. Although HACA are commonly found in patients treated with RTX, their clinical significance is poorly understood. There are cases where the antibodies interfere with the efficacy of RTX, particularly in high titer, 14,27 but the majority of patients with HACA still have a clinical response to at least two repeated doses. Repeated doses beyond this are not yet well studied. Differences in HACA assay techniques may contribute to the uncertainties about what levels of HACA are clinically relevant. The occurrence of other immunologic phenomena after treatment with RTX has also been reported. These include coagulopathies 32,33 and RTX-induced cutaneous vasculitides. 34,35 These occurrences are still the subject of case reports and the nature and magnitude of the association of new autoimmune diseases after treatment with RTX is, as yet, unknown. FUTURE DIRECTIONS FOR TARGETED B-CELL THERAPIES IN VASCULITIS AND LUPUS Several randomized controlled trials are now underway (short titles: RITUXVAS and RAVE in AASV and EXPLORER and LUNAR in SLE clinicaltrials.gov), testing the efficacy of RTX against traditional therapies in both AASV and SLE. These trials are designed to show the efficacy of RTX as an induction agent either alone or in conjunction with a reduced dose of cyclophosphamide. As such, the ability of RTX to prevent future relapses, end-stage renal disease, or death will not be directly answered by these trials. Additionally, the question as to whether RTX should be used as an adjuvant or an alternative to traditional immunosuppressive medications will not be directly answered although differences in trial designs may give important clues to this topic. Although the trials currently underway will provide very important information regarding the efficacy and short-term safety of RTX in these diseases, longer term studies focusing on hard clinical end points will still be warranted. Should RTX prove both as more effective and less toxic than drugs such as IV cyclophosphamide, in the ongoing clinical trials, there will still be several questions as to its use. These include the use of RTX as a chronic immunosuppressive rather than an induction drug and the role and timing of re-dosing and the role of biomarkers in redosing. Additionally, the use of RTX in related disorders such as anti-phospholipid antibody syndromes, 36,37 CNS lupus, 38 and non-anca vasculitides, the use of B-cell depleting therapy in primary glomerular diseases, and the pharmacodynamic and pharmacokinetic impacts of heavy proteinuria and low glomerular filtration rate remain to be determined. The goals of all RTX, and of new therapies for AASV and SLE in general, are invariant: to improve the quality and length of life of patients while limiting treatment-related toxicity. An important component of this is the ability of new therapies to reduce patients exposure to immunosuppressive medications and glucocorticoids. A durable remission in the absence of glucocorticoids appears unlikely with RTX, given current experiences with high rates of late relapses in both AASV and SLE. Whether this can be overcome with more effective B-cell targeted therapies remains to be seen but there are several potential therapies in development. New B-cell depleting medications, such as the humanized anti-cd20 antibodies, ocrelizumab, and ofatumumab, may induce more complete and longer lasting B-cell depletion as well as alter the proportions of B-cell death that occur through complement-dependent, apoptotic, and antibody-dependent mechanisms. In addition to these, non-depleting, targeted, B-cell therapies are under development. These include anti-blys (belimumab) and anti-april which inhibit the interactions of B cells with T cells and are involved in B-cell survival and maturation in both the lymphoid tissues and periphery. Preclinical studies have already demonstrated that tissue B- cell depletion may be enhanced by the addition of anti-blys to the administration of RTX, 39 and preclinical and clinical trials of these agents are beginning in other diseases. Cell surface receptors have also been targeted with TACI-Ig (atacicept) in early clinical trials for SLE. CONCLUSION While studies of RTX for AASV and SLE are limited to case reports/series and small clinical trials, it shows promise as a 680 Kidney International (2007) 72,

6 new treatment for these difficult to manage diseases. The available data suggest that RTX appears safe and in the hands of experienced centers may be considered for the treatment of refractory AASV or SLE. More widespread use of RTX for these indications requires efficacy to be demonstrated in randomized control trials, several of which are underway. However, several issues regarding the use of RTX will remain even after the completion of these trials. These issues include: RTX as initial therapy for these diseases has not yet been investigated; the dosing regimen and need for concomitant therapies must be explored; and the impact of RTX on long-term clinical outcomes, such as end-stage renal disease and death and adverse events. In the future, drugs such as RTX may prove to not only increase the number of medications available for the treatment of these disorders but also provide a more durable response and a novel method for exploring the pathogenesis of AASV and SLE. Should RTX prove efficacious in these diseases, other B-cell-targeted therapies may also prove useful for these difficult to treat diseases. ACKNOWLEDGMENTS We apologize to the authors of the many important works that we were unable to reference in this mini-review due to editorial constraints. Dr Walsh is supported by the Kidney Research Scientist Core Education National Training Program, the Alberta Heritage Foundation for Medical Research, and the Royal College of Physicians and Surgeons of Canada. REFERENCES 1. Takemura S, Klimiuk PA, Braun A et al. T cell activation in rheumatoid synovium is B cell dependent. J Immunol 2001; 167: Odendahl M, Jacobi A, Hansen A et al. Disturbed peripheral B lymphocyte homeostasis in systemic lupus erythematosus. J Immunol 2000; 165: Voswinkel J, Mueller A, Kraemer JA et al. B lymphocyte maturation in Wegener s granulomatosis: a comparative analysis of VH genes from endonasal lesions. Ann Rheum Dis 2006; 65: Popa ER, Franssen CF, Limburg PC et al. In vitro cytokine production and proliferation of T cells from patients with anti-proteinase 3- and antimyeloperoxidase-associated vasculitis, in response to proteinase 3 and myeloperoxidase. Arthritis Rheum 2002; 46: Shlomchik MJ, Craft JE, Mamula MJ. From T to B and back again: positive feedback in systemic autoimmune disease. Nat Rev Immunol 2001; 1: Liossis SN, Kovacs B, Dennis G et al. B cells from patients with systemic lupus erythematosus display abnormal antigen receptormediated early signal transduction events. J Clin Invest 1996; 98: Lipsky PE. Systemic lupus erythematosus: an autoimmune disease of B cell hyperactivity. Nat Immunol 2001; 2: Anolik JH, Campbell D, Felgar RE et al. The relationship of FcgammaRIIIa genotype to degree of B cell depletion by rituximab in the treatment of systemic lupus erythematosus. Arthritis Rheum 2003; 48: Sfikakis PP, Boletis JN, Lionaki S et al. Remission of proliferative lupus nephritis following B cell depletion therapy is preceded by downregulation of the T cell costimulatory molecule CD40 ligand: an openlabel trial. Arthritis Rheum 2005; 52: Vigna-Perez M, Hernandez-Castro B, Paredes-Saharopulos O et al. Clinical and immunological effects of rituximab in patients with lupus nephritis refractory to conventional therapy: a pilot study. Arthritis Res Ther 2006; 8: R Looney RJ, Anolik JH, Campbell D et al. B cell depletion as a novel treatment for systemic lupus erythematosus: a phase I/II dose-escalation trial of rituximab. Arthritis Rheum 2004; 50: Aries PM, Hellmich B, Voswinkel J et al. Lack of efficacy of rituximab in Wegener s granulomatosis with refractory granulomatous manifestations. Ann Rheum Dis 2006; 65: Eriksson P. Nine patients with anti-neutrophil cytoplasmic antibodypositive vasculitis successfully treated with rituximab. J Internal Med 2005; 257: Leandro MJ, Cambridge G, Edwards JC et al. B-cell depletion in the treatment of patients with systemic lupus erythematosus: a longitudinal analysis of 24 patients. Rheumatology 2005; 44: Smith KG, Jones RB, Burns SM, Jayne DR. Long-term comparison of rituximab treatment for refractory systemic lupus erythematosus and vasculitis: remission, relapse, and re-treatment. Arthritis Rheum 2006; 54: Keogh KA, Ytterberg SR, Fervenza FC et al. Rituximab for refractory Wegener s granulomatosis: report of a prospective, open-label pilot trial. Am J Resp Crit Care Med 2006; 173: Keogh KA, Wylam ME, Stone JH, Specks U. Induction of remission by B lymphocyte depletion in eleven patients with refractory antineutrophil cytoplasmic antibody-associated vasculitis. Arthritis Rheum 2005; 52: Omdal R, Wildhagen K, Hansen T et al. Anti-CD20 therapy of treatmentresistant Wegener s granulomatosis: favourable but temporary response. Scand J Rheumatol 2005; 34: Stasi R, Stipa E, Del PG et al. Long-term observation of patients with antineutrophil cytoplasmic antibody-associated vasculitis treated with rituximab. Rheumatology 2006; 45: Gottenberg JE, Guillevin L, Lambotte O et al. Tolerance and short term efficacy of rituximab in 43 patients with systemic autoimmune diseases. Ann Rheum Dis 2005; 64: Cambridge G, Leandro MJ, Teodorescu M et al. B cell depletion therapy in systemic lupus erythematosus: effect on autoantibody and antimicrobial antibody profiles. Arthritis Rheum 2006; 54: Tomietto P, Gremese E, Tolusso B et al. B cell depletion may lead to normalization of anti-platelet, anti-erythrocyte and antiphospholipid antibodies in systemic lupus erythematosus. Thromb Haemost 2004; 92: Vallerskog T, Gunnarsson I, Widhe M et al. Treatment with rituximab affects both the cellular and the humoral arm of the immune system in patients with SLE. Clin Immunol 2007; 122: Anolik JH, Barnard J, Cappione A et al. Rituximab improves peripheral B cell abnormalities in human systemic lupus erythematosus. Arthritis Rheum 2004; 50: van Vollenhoven RF, Gunnarsson I, Welin-Henriksson E et al. Biopsyverified response of severe lupus nephritis to treatment with rituximab (anti-cd20 monoclonal antibody) plus cyclophosphamide after biopsy-documented failure to respond to cyclophosphamide alone. Scand J Rheumatol 2004; 33: Marks SD, Tullus K. Successful outcomes with rituximab therapy for refractory childhood systemic lupus erythematosus. Pediatr Nephrol 2006; 21: Tahir H, Rohrer J, Bhatia A et al. Humanized anti-cd20 monoclonal antibody in the treatment of severe resistant systemic lupus erythematosus in a patient with antibodies against rituximab. Rheumatology 2005; 44: Smolen JS, Keystone EC, Emery P et al. Consensus statement on the use of rituximab in patients with rheumatoid arthritis. Ann Rheum Dis 2007; 66: Rituximab Information: FDA alert US Food and Drug Administration Website. 18 December 2006, rituximab/default.htm. 30. Bearden CM, Agarwal A, Book BK et al. Rituximab inhibits the in vivo primary and secondary antibody response to a neoantigen, bacteriophage phix174. Am J Transplant 2005; 5: Hellerstedt B, Ahmed A. Delayed-type hypersensitivity reaction or serum sickness after rituximab treatment. Ann Oncol 2003; 14: Clatworthy MR, Jayne DR. Acquired hemophilia in association with ANCA-associated vasculitis: response to rituximab. Am J Kidney Dis 2006; 47: Lian EC, Tzakis AG, Andrews D et al. Response of factor V inhibitor to rituximab in a patient who received liver transplantation for primary biliary cirrhosis. Am J Hematol 2004; 77: Dereure O, Navarro R, Rossi JF, Guilhou JJ. Rituximab-induced vasculitis. Dermatology 2001; 203: Kandula P, Kouides PA. Rituximab-induced leukocytoclastic vasculitis: a case report. Arch Dermatol 2006; 142: Kidney International (2007) 72,

7 36. Erdozain JG, Ruiz-Irastorza G, Egurbide MV, Aguirre C. Sustained response to rituximab of autoimmune hemolytic anemia associated with antiphospholipid syndrome. Haematologica 2004; 89: ECR Lambotte O, Durbach A, Kotb R et al. Failure of rituximab to treat a lupus flare-up with nephritis. Clin Nephrol 2005; 64: Tokunaga M, Saito K, Kawabata D et al. Efficacy of rituximab (anti-cd20) for refractory systemic lupus erythematosus involving the central nervous system. Ann Rheum Dis 2007; 66: Gong Q, Ou Q, Ye S et al. Importance of cellular microenvironment and circulatory dynamics in B cell immunotherapy. JImmunol2005; 174: Kidney International (2007) 72,