B Cell Suppression in Primary Glomerular Disease Ilse M. Rood, Julia M. Hofstra, Jeroen K. J. Deegens, and Jack F. M. Wetzels Membranous nephropathy, focal segmental glomerulosclerosis (FSGS), and minimal change disease (MCD) are the most common causes of idiopathic nephrotic syndrome. For many years prednisone, alkylating agents, and calcineurin inhibitors have been the standard of therapy for these patients. More effective or better tolerated treatment modalities are needed. B cell targeted therapy was recently introduced in clinical practice. In this review, we briefly summarize the current standard therapy and discuss the efficacy of B cell targeted therapy in primary glomerular diseases. Observational, short-term studies suggest that rituximab is effective and comparable to standard therapy in maintaining remissions in patients with frequently relapsing or steroid-dependent MCD or FSGS. In contrast, response is limited in patients with steroid-resistant nephrotic syndrome. Rituximab also induces remissions in patients with membranous nephropathy. Controlled clinical trials on kidney endpoints are urgently needed to position B cell targeted therapy in clinical practice. Q 2014 by the National Kidney Foundation, Inc. All rights reserved. Key Words: Rituximab, Membranous nephropathy, Focal segmental glomerulosclerosis, Minimal change disease

Introduction The incidence of idiopathic nephrotic syndrome is 30 to 50/million people/year in adults and 10 to 30/ million people/year in children.1 The most common causes are membranous nephropathy, focal segmental glomerulosclerosis, and minimal change disease (MCD). Most patients need immunosuppressive therapy, and for many years prednisone, alkylating agents, and calcineurin inhibitors (CNIs) have been the standard of therapy. Increased knowledge of the pathogenesis of glomerular disorders and the development of new treatment modalities has provided hope that patients in the future can be treated with more effective and better tolerated therapy. In this review, we briefly summarize the current standard therapy and discuss the efficacy of B cell targeted therapy in primary glomerular diseases, with emphasis on idiopathic membranous nephropathy (iMN), MCD, and idiopathic focal segmental glomerulosclerosis (iFSGS).

The B Cell as Target of Therapy in Idiopathic Nephrotic Syndrome B cell targeted therapy is a plausible treatment option in diseases in which B cells and antibodies play a critical role. Membranous nephropathy, a glomerular disease characterized by the presence of immune deposits in the subepithelial space, is traditionally considered an immunological disease.2 Membranous nephropathy can occur secondary to infection, malignancy, drugs, or systemic autoimmune disease such as systemic lupus eryFrom Department of Nephrology, Radboud University Nijmegen Medical Centre, Nijmegen, The Netherlands. Financial Disclosure: The authors declare that they have no relevant financial interests. Address correspondence to Ilse M. Rood, MD, Department of Nephrology 464, Radboud University Nijmegen Medical Center, PO Box 9101, 6500 HB Nijmegen, The Netherlands. E-mail: [email protected] Ó 2014 by the National Kidney Foundation, Inc. All rights reserved. 1548-5595/$36.00 http://dx.doi.org/10.1053/j.ackd.2014.01.005

166

thematosus (SLE).3 In 70% of patients no underlying cause can be identified, and these patients are considered to suffer from iMN. The discovery of antibodies against the M-type phospholipase A2 receptor (PLA2R) in the serum of patients with iMN provided supportive evidence that iMN is an autoimmune disease.4 AntiPLA2R antibodies are present in more than 70% of patients with iMN.5 Meanwhile, antibodies with other antigenic specificities have been described.6 Admittedly, in the absence of an appropriate animal model, there is no formal prove that these antibodies are pathogenetic. Still, the discovery of antibodies has provided support for the use of anti-B cell therapy in iMN. The pathogenesis of MCD and iFSGS is still unsolved, and the rationale for anti-B cell therapy may seem less evident. Immune deposits are not observed in kidney biopsies, and circulating antibodies have not been detected in the serum of patients with MCD or iFSGS. Circulating factors are likely involved in the pathogenesis of MCD and iFSGS. Older literature suggested that MCD was caused by T cell-dependent vascular permeability factors.7 Permeability factors are also found in iFSGS, with soluble urokinase receptor as the most recently proposed culprit.8 However, there is no proof that these permeability factors are derived from B cells. The introduction of rituximab as a treatment modality for MCD and iFSGS was driven by chance findings. Benz and colleagues reported a patient with steroid-dependent iFSGS.9 This patient was diagnosed with idiopathic thrombocytopenic purpura. After treatment with rituximab, the patient remained in remission without concomitant use of steroids. Nozu and colleagues reported a patient with recurrent FSGS after kidney transplantation.10 Four months after transplantation, a diffuse large B cell lymphoma developed and the boy was treated with rituximab. The lymphoma resolved and interestingly the proteinuria reduced to normal. Many case reports and cohort studies supported the benefits of rituximab and its efficacy provided strong support for a role for B cells in these disorders. This stimulated research in this area. It has been proposed that B cells not only are important as

Advances in Chronic Kidney Disease, Vol 21, No 2 (March), 2014: pp 166-181

B Cell Suppression in Primary Glomerular Disease

antibody-producing cells, but they also can act as antigen-presenting cells and they can produce cytokines, which in turn may activate or change the T cells.11

167

cept, abatacept, and abetimus, are now studied in patients with SLE and are discussed elsewhere.12

Membranous Nephropathy Anti-B Cell Therapy

The current standard therapy for iMN is summarized in recently published guidelines.13 Because almost half of In the group of anti-B cell therapies, rituximab has the patients with iMN and nephrotic syndrome develop longest history. Rituximab is a chimeric monoclonal spontaneous remission, it is advised to restrict immunoantibody (30% murine) against CD20, an antigen present suppressive therapy to the 50% of patients with persison B cells in different stages of maturation: from pre-B tent and progressive disease activity. A combination of cells until memory B cells. Binding of rituximab to cyclophosphamide and prednisone is preferred as initial CD20 activates B cell apoptosis via complement- and therapy. There is grade A level of evidence that such antibody-dependent cytotoxicity. Treatment with rituxitreatment improves kidney outcome.14,15 There is now mab results in depletion of B cells in peripheral blood, supportive evidence that treatment can be restricted to which could persist for more than 6 months. Of note, rithigh-risk patients. In a cohort study that included 254 uximab does not affect plasma cells, which partly expatients with iMN, 124 (49%) patients needed immunoplains maintenance of serum immunoglobulin (Ig) G suppressive therapy.16 The predicted 10-year overall levels. Rituximab was first introduced as treatment of survival was 90%, and only 4% of patients developed non-Hodgkin’s lymphoma. More recently, rituximab ESRD. Monotherapy with was approved by the U.S. prednisone, mycophenoFood and Drug Adminislate mofetil, or azathiotration for a wide range CLINICAL SUMMARY prine is ineffective and of lymphoid malignancies should not be used.17 and autoimmune dis
B cell targeted therapy is increasingly used in patients with CNIs increase remission orders such as rheumatoid idiopathic nephrotic syndrome, such as idiopathic membranous nephropathy, MCD, and idiopathic FSGS. rate and are advised in paarthritis, granulomatosis tients who do not tolerate with polyangiitis, and
The most investigated B cell targeted therapy in primary or do not wish to be microscopic polyangiitis. It glomerular diseases is rituximab. Belimumab is under investigation in membranous nephropathy. treated with alkylating is currently under investiagents.13 Of note, there is gation for SLE, Sjogren’s
It is suggested that rituximab is equivalent to standard no evidence that CNIs syndrome, and primary immunosuppressive therapy in steroid-dependent MCD/ idiopathic FSGS. There is no proof of efficacy in steroidreduce the number of glomerular diseases. resistant disease. hard kidney endpoints. A novel anti-B cell therapy is belimumab, now
Rituximab induces remissions in membranous nephropathy. approved for the treatment B Cell Suppression in of SLE and currently under iMN research for its efficacy in reducing antibodies in The first study with rituxiMN (NCT01610492). Belimumab is a fully human imab in iMN was performed a decade ago by the BerIgG-lambda monoclonal antibody against the circugamo group.18 These investigators treated 8 patients lating B-lymphocyte stimulation factor (BLyS). BLyS is with iMN and nephrotic syndrome; treatment resulted a co-stimulator of B cells and is necessary for the surin remission of proteinuria in 5 of them. More studies, vival and maturation of B cells to plasma cells. BLyS all uncontrolled, have followed. The results are summahas 3 target receptors: (1) B-cell activating factor receprized in Table 1. tor (present on each B cell), (2) transmembrane activator In 2006, Ruggenenti and colleagues reported retroand calcium modulator and cyclophilin ligand interacspective data on 14 nephrotic patients with iMN who tor (present on memory B cells), and (3) B cell maturawere treated with 4 doses of 375 mg/m2 rituximab.19 tion antigen (present on plasma cells). Another The overall remission rate was 43%, but when performproliferating inducing ligand (abbreviated as APRIL) ing subgroup analysis that was based on the presence also targets the transmembrane activator and calcium of tubulointerstitial (TI) damage as observed in the basemodulator and cyclophilin ligand interactor and B-cell line kidney biopsy, it became clear that there was no maturation antigen receptors. Therefore, treatment benefit of rituximab in patients with severe TI damage with belimumab will not result in complete B cell deplewhereas high remission rates were achieved in patients tion. without significant TI injury. The latter observation was Other therapies that target B cells are emerging. These confirmed in a prospective cohort of 9 patients with newer agents, such as ocrelizumab, epratuzumab, atacimild TI injury, with remission occurring in 6 patients

168

Table 1. Rituximab in Idiopathic Membranous Nephropathy: Cohort Studies Baseline Proteinuria (g/d)*

Remuzzi 2002

8 [3/5]

1.4 6 1.4

8.6 6 1.5

Ruggenenti 200619

6 [5/1]

2.1 6 1.0

9.4 6 4.0

8 [3/5]

1.3 6 0.4

9.1 6 4.0

9 [4/5]

1.0 6 0.3

8.9 6 5.3

12 [8/4]

1.4 6 0.5

10.3 6 8.9

24 [16/8]

1.5 6 0.7

9.3 6 3.8

Fervenza 200821

15 [13/2]

1.4 6 0.5

13.0 6 5.7

Segarra 200924

13 [11/2]

1.0 (0.8-1.4

2.3 (0.7-3.2)

Fervenza 201022

20 [17/3]

1.5 6 0.5

11.9 6 4.9

100 [72/28]

1.2 (1.0-1.7)

9.1 (5.8-12.8)

Study 18

Cravedi 200720

Ruggenenti 201223

Rituximab Treatment Dose

FU (mo)

Remission (%)

Relapse (%)

ESRD (%)

Remarks

5

63

NA

NA

12

0

NA

NA

4 3 375 mg/m2 once weekly

12

75

NA

NA

4 3 375 mg/m2 once weekly

12

67

NA

NA

1 3 375 mg/m2 (B cell driven protocol)* 4 3 375 mg/m2 once weekly 2 3 1 g (1-wk interval)

12

67

NA

NA


Pilot study with very limited FU
Retrospective cohort, patients with TI score .1.7 (see text)
Retrospective cohort, patients with TI score ,1.7 (see text)
Prospective cohort, patients with TI score ,1.7 (see text)
Treatment repeated if B cells .5/mm3 (n ¼ 1)

12

67

NA

NA

12

53

NA

13

4 3 375 mg/m2 once weekly

30

100

23

NA

4 3 375 mg/m2 once weekly 1 3 375 mg/m2 or 4 3 375 mg/m2

24

80

5

NA

31

65

25

4

4 3 375 mg/m once weekly 4 3 375 mg/m2 once weekly 2

Abbreviations: CNI, calcineurin inhibitor; FU, follow-up; M/F, male/female; NA, not available; TI, tubulointerstitial. Conversion factors for units: serum creatinine in mg/dL to mmol/L, 388.4. *Mean 6 standard deviation or median (range).


Treatment repeated after 6 mo if B cells .5 3 106/L and proteinuria .3 g/d (n ¼ 10)
CNI-dependent patients, withdrawal of CNI after rituximabinduced remission
Treatment repeated after 6 mo in all patients

Rood et al

Patients (n) [M/F]

Baseline Serum Creatinine (mg/dL)*

B Cell Suppression in Primary Glomerular Disease

(67%). In a follow-up, these investigators showed that a B cell titrated protocol in which patients initially received a single dose of rituximab (375 mg/m2) followed by a second infusion only when 5 or more B cells per cubic millimeter were detected in the circulation during follow-up was as effective as the 4-dose protocol but at a lower cost.20 In this study, the remission rate was 67% at 1 year after treatment. Further evidence that rituximab monotherapy can induce remissions in patients with iMN came from 2 studies led by Mayo Clinic investigators. In the first study, 15 severely nephrotic patients with iMN, of who 7 were refractory to previous immunosuppressive treatment, were treated with 2 3 1 g rituximab (2-week interval).21 In those patients who remained proteinuric but had recovered B cell counts at 6 months, a second course was given. At the end of follow-up (at 12 months), complete remission was achieved in 2 patients (13%) and partial remission in 6 patients (40%). Two patients had progressed to ESRD. The authors tried to identify markers that could predict which patients would benefit from treatment, but no relationship between the response and B cell count, CD20 cells in the kidney biopsy, degree of TI fibrosis, starting proteinuria, or creatinine values was found. In a second study, 20 patients (again, 50% of who had failed prior immunosuppressive therapy) were treated with 4 once-weekly infusions of 375 mg/m2 rituximab.22 Four patients (20%) showed a complete remission after 2 years, and partial remission occurred in 12 additional patients (60%). A relapse occurred in 1 patient (6%). The response in proteinuria was gradual and sustained. Comparison between the studies suggested no difference in the effectiveness of the 2 dosing regimens at 1 year. The Bergamo group recently reported the largest study to date with extended follow-up.23 This study included 100 consecutive patients with iMN and nephrotic syndrome who were treated with rituximab, almost 1/3 of who were refractory to standard immunosuppressive agents.23 Patients were treated with either a single dose of 375 mg/m2 or 4 weekly doses of 375 mg/m2. The mean follow-up was 31 months. Remission was achieved in 65% of patients, approximately 25% of remitting patients relapsed, 4 patients died, and 4 developed ESRD. In addition to studies using rituximab as initial therapy in iMN, Segarra and colleagues treated CNI-dependent iMN patients (at least 4 previous CNIresponsive relapses) with rituximab (4 3 375 mg/m2).24 Rituximab enabled successful withdrawal of CNIs in all 13 patients. Three patients relapsed (mean follow-up 35 months) but were successfully retreated with a second course of rituximab. The beneficial effect of rituximab in iMN likely results from the depletion of B cells responsible for producing pathogenic autoantibodies. A recent study showed that anti-PLA2R antibodies disappeared in 17 of 25 (68%) patients with iMN who were treated with rituximab.25 A

169

decline in antibody levels preceded a decrease in proteinuria, and disappearance of antibodies was associated with a higher remission rate. Next to rituximab, there is another B cell suppressant that is currently under study in patients with iMN in a Phase II clinical trial (NCT 01610492).26 The monoclonal antibody belimumab reduced the serum levels of rheumatoid factor and anti-dsDNA in patients with rheumatoid arthritis and SLE, respectively.27 Because iMN is associated with autoantibody generation and has proven to be responsive to rituximab, belimumab is considered a potentially effective therapy in iMN.

MCD and Focal Segmental Glomerulosclerosis MCD is the most common cause of the nephrotic syndrome in children. A kidney biopsy diagnosis is not required. Most children with MCD will respond to corticosteroids; moreover, patients with other histologies that respond to corticosteroids have a similar, good prognosis and maintain kidney function.28 Therefore, the term steroid-sensitive nephrotic syndrome is used to define these patients. In contrast, in adults with a nephrotic syndrome, the diagnosis is based on kidney biopsy. MCD is defined by the absence of glomerular abnormalities in light and immunofluorescence microscopy. Classically, FSGS is defined by the presence of glomerular lesions characterized by mesangial sclerosis, obliteration of capillaries, hyalinosis, foam cells, and adhesion between the glomerular tuft and Bowman’s capsule. A proposed classification describes several other histological variants, including tip lesions, collapsing FSGS, and perihilar FSGS.29 FSGS is not a disease entity. In many patients FSGS is secondary to genetic causes, infections, hyperfiltration, or other underlying glomerulopathies.30 In this review, we discuss idiopathic FSGS, a diagnosis that only can be made after exclusion of all secondary causes. There is debate whether MCD and iFSGS are separate diseases or are different manifestations of a single disorder. The response to steroid therapy is clinically more important than the histological classification, and literature data thus classify patients on the basis of their steroid responsiveness. The available data, although limited, also suggest that the response to B cell therapy is more dependent on previous steroid responsiveness than on histology. The current standard of therapy for MCD and iFSGS is summarized in recently published guidelines.13 Initial therapy consists in both cases of corticosteroids. In adults the initial period of high-dose prednisone therapy should be more prolonged (Table 2). Response to therapy is variable. Patients can develop a complete remission of proteinuria (steroid sensitive). However, many patients will develop 1 or more relapses after withdrawal of steroids. Two or more relapses within 6 months after initial response or 4 or more relapses

170

Rood et al

Table 2. Standard Immunosuppressive Therapy in Nephrotic Syndrome (MCD and iFSGS) in Children and Adults13 Moment of Treatment

Children

Initial treatment nephrotic syndrome

Prednisone (2 mg/kg/d, max 60 mg) for 4-6 wk, followed by 1.5 mg/kg (max 40 mg) on alternate days with tapering over a period of 2-5 mo.

Infrequent relapses nephrotic syndrome

Prednisone (2 mg/kg/d, max 60 mg) until the child has been in remission for at least 3 d. Thereafter, 1.5 mg/kg (max 40 mg) on alternate days at least 4 wk. (1) Cyclophosphamide 2 mg/kg/d for 8-12 wk (after steroid-induced remission). (2) Chlorambucil 0.1-0.2 mg/kg/d for 8 wk (alternative for cyclophosphamide). (3) Levamisole 2.5 mg/kg on alternate days for .12 mo (4) CNI (CsA 4-5 mg/kg/d or tacrolimus 0.1 mg/kg/d) for at least 12 mo. Monitor CNI levels during therapy to limit toxicity. (5) MMF 1200 mg/m2/d for at least 12 mo. (6) Rituximab (off-label) should be considered only in children with FRNS or SDNS who have continuing frequent relapses despite optimal combinations of prednisone and steroid-sparing agent and/or who have serious adverse effects of therapy. (1) CNI for 6 mo (extend to 12 mo if partial remission achieved). (2) If no remission after CNI, MMF (with or without high-dose prednisone).

Frequently relapse or SDNS

SRNS

Adults Prednisone (1 mg/kg/d, max 80 mg) for a maximum period of 16 wk.
Remission: slowly tapering over a period of 6 mo.
No remission: tapering over a period of 6 wk. Prednisone (1 mg/kg/d, max 80 mg) until remission and slowly tapering over a period of 6 mo. (1) Cyclophosphamide 2-2.5 mg/kg/d for 8 wk. (2) CNI (CsA 3-5 mg/kg/d or tacrolimus 0.05-0.1 mg/kg/d) for 1-2 y. Monitor CNI levels during therapy to limit toxicity. (3) MMF 500-1000 mg twice daily in case of intolerance for steroids, cyclophosphamide, or CNI.

(1) CsA (3-5 mg/kg/d) for at least 4-6 mo (prolonged if partial or complete remission of 12 mo, followed by slow taper). (2) If CsA not tolerated: MMF 500-1000 mg twice daily with high-dose dexamethasone.

Abbreviations: CNI, calcineurin inhibitor; CsA, cyclosporine A; iFSGS, idiopathic focal segmental glomerulosclerosis; MCD, minimal change disease; MMF, mycophenolate mofetil; FRNS, frequently relapsing nephrotic syndrome; SDNS, steroid-dependent nephrotic syndrome; SRNS, steroid-resistant nephrotic syndrome. Definitions according Kidney Disease/Improving Global Outcomes clinical practice guideline for glomerulonephritis.13

within 12 months is used to define frequently relapsing nephrotic syndrome (FRNS).13 Steroid-dependent nephrotic syndrome (SDNS) is defined as 2 consecutive relapses during corticosteroid therapy or within 14 days of ceasing therapy. Some patients will not develop a complete remission, and steroid-resistant nephrotic syndrome (SRNS) is defined as the persistence of proteinuria despite prednisone 1 or 2 mg/kg per day every other day for more than 8 weeks in children or 4 months in adults. Patients with FRNS and SDNS are often treated with a prolonged course of prednisone and additional therapy (Table 2).13 Treatment often has to be given for many years and is limited by well-known side effects such as hyperglycemia, reduced bone mineral density, hypertension, impaired growth, mental disorders (mood swings), facial changes, obesity, nephrotoxicity, infertility, bone marrow depression, liver function abnormalities, neurotoxicity, gum hypertrophy, and vasculitis.

Therefore, alternative therapy with fewer adverse effects is needed.

B Cell Therapy in MCD and iFSGS The only investigated B cell targeted therapy is rituximab. This drug is used off-label and is mostly studied in patients with SDNS and SRNS. Patients with FRNS are mostly successfully treated with standard therapy, although in the case of severe side effects, B cell targeted therapy may be an option. Literature data are summarized in Tables 3-5. We have only selected studies that included 4 or more patients. We have categorized the patients into 3 groups: SDNS, SRNS, and recurrent iFSGS after kidney transplantation. Because well-designed and adequately powered controlled clinical trials are lacking, conclusions are drawn from retrospective and prospective cohort studies.

B Cell Suppression in Primary Glomerular Disease

SDNS Eight studies were uncontrolled, retrospective, and included in total 169 children and 22 adults with SDNS (Table 3).31-38 In almost all cases rituximab was administered while patients were in remission. Treatment was quite variable: a single course of rituximab consisted of 1 to 4 consecutive pulses of 375 mg/m2 at weekly intervals. Many patients received additional courses either given because of a relapse or because of an increased CD19 count (B cell recovery). Details on concomitant therapy are often lacking, and only a few studies explicitly mention that all other immunosuppressive drugs were withdrawn. Follow-up is mostly limited to 12 months. Overall, a sustained remission was observed in 14% to 83% of patients at 12 months and in 32% to 44% of patients at 24 months after the start of rituximab.32-34,36,39 Relapses occurred after a median of 5 to 11.4 months.34,35,38 Two retrospective studies provided more detailed information regarding immunosuppressive-free remission. Kemper and colleagues studied 37 patients with a followup of more than 2 years.34 After rituximab, steroids were discontinued in 35 of 37 (94.5%) patients after a median of 1.3 (0.37-6) months. Other maintenance immunosuppressive medication was discontinued completely in 22 patients and continued at the discretion of the local center in 15 patients. Twelve patients remained in remission after the initial rituximab course, and in 7 there was sustained remission without further immunosuppressive therapy. Muyentwali and colleagues reported 17 adults with a follow-up of 5 to 82 months.38 These patients received 1 to 4 doses rituximab (375 mg/m2 once weekly). Eleven patients attained remission and all were able to discontinue the concomitant immunosuppressive medication. Both studies suggest that treatment with rituximab facilitates tapering or withdrawal of other immunosuppressive medication, although for a limited time period. We summarize 8 prospective studies (Table 3). All were uncontrolled and at best compared the relapse rate before and after rituximab.40,41 In some studies patients apparently were allowed to continue concomitant immunosuppressive therapy. Because in patients with SDNS the relapse rate decreases with age and many patients eventually will develop persistent remission,42 the efficacy of rituximab cannot be reliably judged and remission rates will be overestimated. Three of these prospective studies reported the outcome of rituximab therapy in a cohort study with reasonably strict and protocolized withdrawal of immunosuppressive agents. Ravani and colleagues included 46 children with SDNS who never had a remission without immunosuppressive therapy.43 After 1 to 5 doses of rituximab, the immunosuppressive medication was tapered and discontinued in 45 days. At 12 months of follow-up, 9 patients (20%) had not relapsed. Sellier-Leclerc and colleagues studied 30 chil-

171

dren who received rituximab with repeated courses to maintain B cell depletion for at least 15 months.44 Concomitant immunosuppressive medication was tapered off over 3 months after B cell depletion. After a follow-up of 26 to 52 months, 18 patients (60%) were still in remission. Takei and colleagues studied 25 adults who initially received 1 dose of rituximab and a second dose after 6 months.45 At 6 months of follow-up, 22 patients (88%) were in remission. All patients with a relapse (n ¼ 3) achieved a new remission after the second dose of rituximab. At 12 months of follow-up, 24 patients were in remission and 15 had discontinued all concomitant immunosuppressive medication. Altogether, these studies suggest that rituximab may represent an attractive alternative to current immunosuppressive therapy. Two comparative studies provided additional evidence that rituximab can replace standard immunosuppressive agents. In the study of Sinha and colleagues, all patients who received rituximab treatment (2 or 3 doses) discontinued prednisolone in 3 to 4 months after rituximab treatment.39 Other immunosuppressive medication was already stopped at the time of infusion. These patients (n ¼ 10) were compared to a group of patients (n ¼ 13) who received prednisolone with tacrolimus. The prednisolone was reduced to 0.2 to 0.3 mg/kg on alternate days in the tacrolimus group. Other immunosuppression was also stopped. At 12 months of follow-up, 50% of the patients in the rituximab group and 54% of the tacrolimus group had a relapse. The time to relapse was not different between the 2 groups (Table 3). Another open-label randomized trial compared 2 doses of 375 mg/m2 rituximab (together with a lowdose prednisone and CNI) with a normal dose of prednisone and CNI in children.46 The mean level of proteinuria was 1.6 g/day (standard deviation: 2.8). At 3 months of follow-up proteinuria was 70% lower in the group who received rituximab (confidence interval 35-86%, P ¼ .003). At 12 months of follow-up 25% of the children assigned to the rituximab group were still in remission without using prednisone or CNIs.

SRNS Four retrospective cohort studies were performed in children with SRNS (Table 4).31,33,35,47 In these studies, remission was reached in 41 of 83 patients with complete remission in 22 patients and partial remission in 19 patients. The major problem in the interpretation of these data is the definition of steroid resistance. These studies defined steroid resistance as a lack of remission after 4 weeks of corticosteroid therapy. The minimum requirement of corticosteroid exposure to define resistance remains unclear. However, because remissions may develop after an extended period of corticosteroids,48 the Kidney Disease Improving Global Outcomes guideline stated that the minimum exposure

172

Table 3. SDNS Rituximab 375 mg/m2 Once Weekly

Outcome FU (mo)

Remission (%)

Relapse (%)

Time to Relapse (mo)*

28

NA; NA

1-4 doses 2 course: n ¼ 5

1-10

36

46

6 (1-16)

7

13.8 6 5.2; 6.3 6 3.3

1 dose 2 course: n ¼ 3

12

14

86

NA

Gulati 201033

24

11.7 6 2.9; 8.9 6 2.9

2 course: n ¼ 1

12

83

17

Kemper 201234

37

13.4 (6.4-18.2); 2.0-14.8

1-4 doses $2 course: n ¼ 19

12 24

70 32

30 68

— —

Ito 201335

55

4.5 (0.9-16.3); 4.8 (0.2-14.7)

1.8 6 1.4 doses (range 1-7)

7-31

49

51

5 (1-24)

Tellier 201336

18

13.5 (5.9-18); 10.4 (3.5-16)

1-4 doses $2 courses: n ¼ 15

24

44

56

13 (5-22)

5

29.2 6 3.9; 18.3 6 10.2

1-4 doses

14

100

0

NA

Study Retrospective studies Prytula 201031

Ito 201132

Kronbichler 201337

11.2 (8-14)

Remarks


No data available about indication and timepoint of repeated course rituximab.
5 patients without response to rituximab.
2 course because of relapse (timepoint not available).
Steroid-induced remission before rituximab administration.
At end FU at 12-38 mo: sustained remission in 17 patients.
Steroid-induced remission before rituximab administration.
No data available about indication of repeated courses rituximab.
Overall time to relapse after initial course rituximab: 9.6 mo (5.2-64.1).
Including $15 patients from other studies.32,40,41
Steroid-induced remission before rituximab administration.
Repeated courses when relapse or CD19 .1%
Steroid-induced remission before rituximab administration.
Childhood onset: 3; adult onset: 2.
After total FU (range 14-55 mo) 1 relapse after 23 mo.
Steroid-induced remission before rituximab administration in 2 patients, 3 patients with proteinuria.

Rood et al

Patients (n)

Age (y); Duration Disease (y)*

Munyentwali 201338

Mean 11.4
Childhood onset: 12; adult (range 4.8-16.3) onset: 5.
Steroid-induced remission before rituximab administration in 10 patients, 7 patients with proteinuria.

29.4 (18.5-65); 12.9 (1.8-30.5)

1-4 doses

5-82

65

35

46

9.9 6 4.3; 6.3 6 4.1

1-5 doses

12

20

80

NA

Sellier-Leclerc 201244

30

12.9 (3.7-19.7); 9.5 (0.3-17.5)

1-4 doses $2 courses: n ¼ 30

26-52

60

40

NA

Kamei 200940

12

12.7 (5-19); 7.2 (1.5-10.6)

1 dose

12

25

75

Fujinaga 201041

10

11.1 6 4.5; 4.6 (2.8-10.8)

1-2 doses

12

70

30

Prospective studies Ravani 201343

4 (0.3-12)

NA


Including long-term FU of 27 children from previous study.46
Inclusion criteria: never a remission without IS therapy.
Relapse: presence of proteinuria or restart of IS after complete withdrawal of IS therapy.
Steroid-induced remission before rituximab administration.
Repeated courses to maintain B cell depletion for at least 15 mo.
Steroid-induced remission before rituximab administration.
Relapse rate in 6 mo before/after rituximab: 2.83 (SD 1.19) vs 1.08 (SD 1.08) (P ¼ .016).
Steroid-induced remission before rituximab administration.
At end FU at 16.8 6 5.9 mo sustained remission in 5 patients; 5 patients had a relapse and these patients discontinued the CsA at rituximab infusion.
Relapse rate in 12 mo before/after: 4.1 6 1.7 vs 0.6 6 0.6 (P , .01).
Steroid-induced remission before rituximab administration. (Continued )

B Cell Suppression in Primary Glomerular Disease

17

173

Study

Patients (n) 56

Age (y); Duration Disease (y)*

Rituximab 375 mg/m2 Once Weekly

174

Table 3. SDNS (Continued ) Outcome FU (mo)

Remission (%)

Relapse (%)

Time to Relapse (mo)*

22

14.3 (6.3-22.1) 11.0 (3.6-16.5)

2-4 doses $2 courses (n ¼ 12)

6-39

73

14

7-17

Hoxha 201161

6

24.8 6 6.3; 7.9 6 4.9

1 dose .2 course: n ¼ 5

12

50

50

4-12

Takei 201345

25

30 6 12; 10 6 8

1 dose 2 course at 6 mo

6 12

88 96

12 4

5-6 12

Comparative studies Sinha 201239

23

Group 1 (n ¼ 10): 12.2 6 2.3; 3.6 6 1.5 (age at onset) Group 2 (n ¼ 13): 12.3 6 3.0; 3.6 6 2.2 (age at onset)

2-3 doses in Group 1

12

50 (Group 1) 50 (Group 1) 46 (Group 2) 54 (Group 2)

8.5 6 5.1 (Group 1) 9.8 6 5.6 (Group 2)


Including 2 steroid-resistant, CsA-sensitive patients.
Steroid-induced remission before rituximab administration in 15 patients, 7 patients with proteinuria.
Indication repeated courses: when response on first course (defined as no relapse of proteinuria before reappearance of CD19 cells despite IS tapering below the usual threshold of relapse).
3 patients without response to rituximab.
Additional courses rituximab when B cells increased or when proteinuria increased.
At end of FU (17.2 6 4.8 mo), 5 patients attained complete remission and 1 patient a partial remission after repeated infusions of rituximab.
Proteinuria 0.2-9.4 g/d at moment of rituximab administration.
In total, 4 different patients with a relapse.
Steroid-induced remission before rituximab administration in 9 patients; 16 patients with proteinuria.


Retrospective study.
Group 1 received rituximab treatment; Group 2 received tacrolimus 0.1-0.2 mg/kg/d.
Including 3 patients from another study.33

Rood et al

Guigonis 2008

Remarks

Abbreviations: CI, confidence interval; CNI, calcineurin inhibitor; CsA, cyclosporine A; FU, follow-up; IS, immunosuppression; MMF, mycophenolate mofetil; NA, not available; PSL, prednisolone; SD, standard deviation; SDNS, steroid-resistant nephrotic syndrome. *Mean 6 SD or median (range).

Ravani 201146

54

Group 1: 10.2 6 4.0; 5.7 6 3.5 Group 2: 11.3 6 4.3; 7.8 6 4.0

Group 1: 1-2 doses with low-dose PSL 1 CNI Group 2: PSL 1 CNI normal doses

3

Proteinuria was 70% lower in Group 1 compared with Group 2 (CI 35-86%; P ¼ .003)


Steroid-induced remission before rituximab administration.
Randomized controlled trial.
Proteinuria 1.6 g/24 h (62.8) at moment of rituximab administration.

B Cell Suppression in Primary Glomerular Disease

175

to high-dose prednisone should be 8 weeks in children and 16 weeks in adults before defining steroid resistance.13 The role of rituximab in steroid-resistant patients was questioned in 2 other studies in which steroid resistance was defined as a minimum exposure to high-dose steroids of at least 4 months.49,50 Patients had a nephrotic syndrome at baseline in both studies. Magnasco and colleagues conducted an open-label randomized controlled trial and compared a group of children (n ¼ 16) who received 2 doses of 375 mg/m2 rituximab in addition to standard therapy with a group of children (n ¼ 15) who received only standard therapy. Standard therapy consisted of prednisone and a CNI. In contrast to the results from the retrospective studies, Magnasco and colleagues did not find a difference in reduction of proteinuria between the 2 groups (P ¼ .77). Fernandez and colleagues showed that none of the 8 adults who received 4 doses of rituximab developed a complete or partial remission (defined as proteinuria ,2 g/day). These 2 studies indicate that rituximab has no beneficial effect in SRNS. Of note, on the basis of the study data, this conclusion holds for patients who were still nephrotic after prolonged steroid therapy. It is unknown whether patients who partially respond to steroids may benefit from rituximab. It is also unclear if patients with secondary steroid resistance may respond as suggested by the study of Bagga and colleagues51 (Table 4).

Recurrence After Transplantation Recurrence of iFSGS after transplantation in patients with iFSGS is high and counts up to 42%.52 Plasmapheresis is used as a treatment for recurrent FSGS. Approximately 70% of the children and 63% of the adults treated with plasmapheresis attain a complete or partial remission of proteinuria.53 Rituximab has been used in patients with recurrent FSGS. Five studies included 4 or more patients (Table 5). Interpretation is hampered by the use of concomitant plasmapheresis in most patients. Araya and colleagues studied 39 patients, and 38 patients were treated with plasmapheresis.54 The single patient who was not treated with plasmapheresis developed a remission. Details of this particular patient are lacking. The best evidence comes from the study of Kumar and colleagues.55 Seven patients remained nephrotic despite plasmapheresis therapy for 1 to 61 months. Rituximab was given in 1 to 4 weekly doses. Two patients developed a complete remission and 3 patients a partial remission.

B Cell Monitoring After Treatment With Rituximab In patients with glomerular disease, peripheral B cell depletion (defined as a CD19 count ,5-10 cells/mm3 or

176

Table 4. SRNS Outcome

Study

Patients (n)

Retrospective studies Gulati 201033 33

Age (y); Duration Disease (y)*

Rituximab 375 mg/m2 Once Weekly

FU (mo)

Remission (%)

No Response (%)

12.7 6 9.1; 6.4 6 4.7

1-4

6

48: CR :27 PR: 21

52

27

NA

1-5

NA

44:CR:22PR:22

56

Ito 201335

19

NA

2.3 6 1.4

12

63: CR:31.5 PR:31.5

37

Kari 201147

4

9.7 6 1.5; 2.3 (0.5-5)

1

3

25 (CR)

75

Fernandez 200950

8

31 6 14; 50 6 35 (mo)

4 doses 2 course (n ¼ 3):
at 6 mo: 2 doses (n ¼ 1)
at 12 mo: 4 doses (n ¼ 2)

1-12

0

100

Remarks

32 d (8-60 d)
Definition SRNS: lack of remission despite therapy with prednisone for 4 wk.
Primary resistance: 24; secondary resistance: 9.
No significant difference in response between primary or late resistance. NA
Definition SRNS: lack of remission despite therapy with prednisone for 4 wk.
Primary resistance: 13; secondary resistance: 13.
FU after initial response (6-12 mo) : sustained remission: 2/12; relapse: 9/12 (time to relapse: 5 mo (1-16)) (data only available of 11 patients). NA
Definition SRNS: lack of remission despite therapy with prednisone for 4 wk.
Including 1 patient with a mutation in WT1 (no response to rituximab). NA
Definition SRNS: lack of remission despite therapy with prednisone for 4 wk.
Primary resistance: 2; secondary resistance: 2.
FU after initial response: relapse: 1/1 (time to relapse: 4 mo). —
Definition SRNS: nephrotic syndrome despite prednisone therapy (1 mg/kg per day) for $4 mo. At 1 mo:
Proteinuria .50% diminished: 3. At 6 mo:
Sustained .50% decrease of proteinuria: 1
Relapse: 2. At 12 mo
Proteinuria .50% diminished: 2 (these patients

Rood et al

Prytula 201031

Time to Remission (mo)*

Abbreviations: CNI, calcineurin inhibitor; CR, complete remission; FU, follow-up; IS, immunosuppression; NA, not available; PR, partial remission; PSL, prednisolone; SRNS, steroidresistant nephrotic syndrome. *Mean 6 SD or median (range).


Definition SRNS: primary and delayed resistance to corticosteroids and CNIs for at least 6 mo.
Standard therapy of PSL 1 CNI 30 d after rituximab reduction of IS if proteinuria is ,1 g/d/m2 3 Randomized controlled trial Magnasco 31 201249

8 (2-16); 1.5

Group 1 (n ¼ 16): 2 doses 1 standard therapy Group 2 (n ¼ 15): standard therapy

No difference in reduction of proteinuria between the 2 groups (P ¼ .77)


Definition SRNS: resistance to high-dose steroids, alkylating agents, and CNI. NA 0 100: CR:60 PR:40 10 wk 4 10.5 y 6 5.3; 8.3 6 5 5 Prospective study Bagga 200751

received a 2 course rituximab).

B Cell Suppression in Primary Glomerular Disease

177

,1% of lymphocytes) is obtained after 1 week in 83% to 100% of the patients irrespective of the level of proteinuria.40,41,44,56 Still, in patients with iMN and proteinuria, serum levels of rituximab were lower than in patients with rheumatoid arthritis.21 No correlation was observed in these patients between the levels of rituximab and the clinical response.21,57 B cell counts started to recover after 3 months, much faster than described in patients with anti-neutrophil cytoplasmic antibody-associated vasculitis, rheumatoid arthritis, or non-Hodgkin’s lymphoma, suggesting that the lower serum levels result in more rapid B cell recovery.21 Rapid relapses are also described in patients with SDNS treated with 1 dose of rituximab.32,40 The optimal regimen in MCD and iFSGS is undetermined. B cell depletion may not be necessary for the development of remission.31,40 On the other hand, although most relapses occur after B cell recovery, relapses despite ongoing B cell depletion have also been observed.40,44 The available data on B cell depletion/B cell recovery in relation to remission and relapse of nephrotic syndrome suggest no clear and established relationship. This is in line with a study in patients with rheumatoid arthritis in which no relationship was found between B cell depletion and clinical response and between the recovery of B cells and the return of disease activity.58 Therefore, monitoring of B cells is generally not helpful to guide therapy in clinical practice. However, there may be exceptions to the rule. In the above mentioned Italian study, titrating rituximab to circulating B cells was as effective as the standard protocol in achieving a remission of iMN but at lower costs and possibly fewer side effects.20 Whether such a strategy would also be cost-effective in MCD/iFSGS is currently unknown. Further studies are needed to evaluate whether monitoring circulating B cells can guide treatment in MCD/ iFSGS.

Conclusion In iMN, treatment with rituximab is associated with high remission rates, and relapse rates are low or at least comparable to those of standard immunosuppressive therapy. Only mild side effects have been reported. It is important to note that several studies have shown rituximab-induced remission in patients who previously failed other treatments. Rituximab therapy may be less beneficial in patients with iMN and moderate TI fibrosis than in those with mild or no interstitial fibrosis, but this has not been confirmed. It is not established that rituximab improves kidney survival in iMN. In SDNS, the data support the beneficial effects of rituximab. Treatment with rituximab might especially be of value in patients with SDNS with unacceptable side effects of other immunosuppressive medication and may

178

Table 5. Recurrent iFSGS After Transplantation

Study

Patients (n)

Retrospective studies Prytula 201031 15

Tsagalis 201162

Araya 201154

4

39

Age (y); Duration Disease (y)* NA; NA Age at onset 11 (mo)-13 (y)

21-48; 1-5

18 (5-48); age at onset 6 (1-40)

Time to Recurrence

1-4

NA

1 g, 2 doses every 2 wk, and after 1 year

2 mo-6 y

1-6

74.3% within 1 mo

Rituximab was administered to prevent recurrence

Audard 201263

4

28-43; age at onset: 9-22

1 Second dose after 1 week in 2 patients

Kumar 201355

8

5-17

1-4

Outcome At end of study 9/15 good initial response
Sustained remission: 5 (FU: 5-84 mo)
Relapse: 3 (time to relapse: 6-16 mo)
Complete remission: 2/4 (FU: 24 and 60 mo)
Time to complete remission in 1 patient: 7 mo
Partial remission: 2/4 (FU 18 and 36 mo)
Complete remission: 17
Partial remission: 8
No response: 14 No recurrence at FU 12-54 mo

In 7 patients immediately
Complete remission: after transplantation; 2 (time to response: 1.5 mo and 8 mo) in 1 patient after 4 y
Partial remission: 4 (Time to response: 0.5 to 9 mo)
No response: 2 FU: 1-33 mo

Abbreviations: FSGS, focal segmental glomerulosclerosis; FU, follow-up; NA, not available. *Mean 6 SD or median (range).

Concomitant Plasmapheresis NA

Pretransplantation: 0 Post-transplantation: 4 (20-69 sessions)

Pretransplantation: 9 Post-transplantation: 38 (0-133 sessions)

Remarks
Definition good response: no or mild proteinuria/albumin .30 g/L.
Children.
Adults.
3/4 patients still receive maintenance plasmapheresis (1 complete remission and 2 partial remission).
Retrospective review of case reports.
children: n ¼ 19.


Second transplantation due to recurrence of FSGS, rituximab as prophylactic therapy.
All patients were primarily steroid resistant. Pretransplantation: 4
All children received Post-transplantation: 8 rituximab after minimal or no response to plasmapheresis (1.2-6 mo treatment with plasmapheresis before rituximab in the patients who attained a complete remission).
1 patient with partial remission died 1 mo later because of multiorgan failure.

Pretransplantation: 0 Post-transplantation: 2 (6 and 5 sessions)

Rood et al

Rituximab 375 mg/m2 Once Weekly

179

B Cell Suppression in Primary Glomerular Disease

Table 6. Ongoing Clinical Trials in Primary Glomerular Diseases26 NCT

Disease

Title Study

Phase

NCT01508468

iMN

3

NCT01180036 NCT00977977

iMN iMN

NCT01610492

iMN

NCT01762852

iMN

NCT01716442

SRNS 1 SDNS

NCT01268033

CNI-dependent nephrotic syndrome

NCT01573533

Steroid resistant FSGS

NCT00498368

IgA nephropathy

Evaluate Rituximab Treatment for Idiopathic Membranous Nephropathy (GEMRITUX) MEmbranous Nephropathy Trial Of Rituximab (MENTOR) Rituximab Plus Cyclosporine in Idiopathic Membranous Nephropathy A Study of Belimumab in Idiopathic Membranous Glomerulonephropathy Efficacy and Safety Study of Intravenous Belimumab Versus Placebo in Subjects With Idiopathic Membranous Nephropathy (Note: this study was recently withdrawn) Rituximab Trial for Pediatric Nephrotic Syndrome (RTX2012) Efficacy of Rituximab for the Treatment of Calcineurin Inhibitors Dependent Nephrotic Syndrome During Childhood (NEPHRUTIX) A Pilot Study to Assess the Efficacy of Rituximab Therapy in Treatment Resistant FSGS Rituximab in Progressive IgA Nephropathy

213 2 2 2

213 213

2 4

Abbreviations: CNI, calcineurin inhibitor; FSGS, focal segmental glomerulosclerosis; IgA, immunoglobulin A; iMN, idiopathic membranous nephropathy; SDNS, steroid-dependent nephrotic syndrome; SRNS, steroid-resistant nephrotic syndrome.

be used as rescue therapy. Rituximab might also be useful in patients with secondary steroid resistance.49,51 There is currently no evidence of efficacy in patients with primary SRNS. Only limited research is performed in other glomerular diseases. One prospective study showed no beneficial effect of rituximab in 5 patients with IgA nephropathy.59 In 6 patients with type I membranoproliferative glomerulonephritis, rituximab reduced proteinuria.60 Long term benefits of rituximab clearly remain unproven, and the results of upcoming randomized controlled trials with hard kidney endpoints are eagerly awaited (Table 6).26

Acknowledgments I.M.R. is supported by an AGIKO-grant of ZonMw-NWO (grant 92003587). J.M.H. is supported by the Dutch Kidney Foundation (grant KJPB11.021).

References 1. Braden GL, Mulhern JG, O’Shea MH, Nash SV, Ucci AA Jr, Germain MJ. Changing incidence of glomerular diseases in adults. Am J Kidney Dis. 2000;35(5):878-883. 2. Glassock RJ. Human idiopathic membranous nephropathy–a mystery solved? N Engl J Med. 2009;361(1):81-83. 3. Glassock RJ. Secondary membranous glomerulonephritis. Nephrol Dial Transplant. 1992;7(suppl 1):64-71. 4. Beck LH Jr, Bonegio RG, Lambeau G, et al. M-type phospholipase A2 receptor as target antigen in idiopathic membranous nephropathy. N Engl J Med. 2009;361(1):11-21. 5. Hofstra JM, Wetzels JF. Anti-PLA(2)R antibodies in membranous nephropathy: ready for routine clinical practice? Neth J Med. 2012;70(3):109-113.

6. Murtas C, Bruschi M, Candiano G, et al. Coexistence of different circulating anti-podocyte antibodies in membranous nephropathy. Clin J Am Soc Nephrol. 2012;7(9):1394-1400. 7. Yoshizawa N, Kusumi Y, Matsumoto K, et al. Studies of a glomerular permeability factor in patients with minimal-change nephrotic syndrome. Nephron. 1989;51(3):370-376. 8. Wei C, El Hindi S, Li J, et al. Circulating urokinase receptor as a cause of focal segmental glomerulosclerosis. Nat Med. 2011;17(8): 952-960. 9. Benz K, Dotsch J, Rascher W, Stachel D. Change of the course of steroid-dependent nephrotic syndrome after rituximab therapy. Pediatr Nephrol. 2004;19(7):794-797. 10. Nozu K, Iijima K, Fujisawa M, Nakagawa A, Yoshikawa N, Matsuo M. Rituximab treatment for posttransplant lymphoproliferative disorder (PTLD) induces complete remission of recurrent nephrotic syndrome. Pediatr Nephrol. 2005;20(11): 1660-1663. 11. 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(1):62-74. 12. Vincenti F, Cohen SD, Appel G. Novel B cell therapeutic targets in transplantation and immune-mediated glomerular diseases. Clin J Am Soc Nephrol. 2010;5(1):142-151. 13. Kidney Disease: Improving Global Outcomes (KDIGO) Glomerulonephritis Work Group. KDIGO Clinical Practice Guideline for Glomerulonephritis. Kidney Int Suppl. 2012;2:139-274. 14. Hofstra JM, Wetzels JF. Introduction of a cyclophosphamide-based treatment strategy and the risk of ESRD in patients with idiopathic membranous nephropathy: a nationwide survey in the Netherlands. Nephrol Dial Transplant. 2008;23(11):3534-3538. 15. Hofstra JM, Wetzels JF. Alkylating agents in membranous nephropathy: efficacy proven beyond doubt. Nephrol Dial Transplant. 2010; 25(6):1760-1766. 16. Van den Brand JA, Van Dijk PR, Hofstra JM, Wetzels JFM. Long term outcomes in idiopathic membranous nephropathy using a restrictive treatment strategy. J Am Soc Nephrol. 2013;25(1): 150-158. 17. Hofstra JM, Fervenza FC, Wetzels JF. Treatment of idiopathic membranous nephropathy. Nat Rev Nephrol. 2013;9(8):443-458.

180

Rood et al

18. Remuzzi G, Chiurchiu C, Abbate M, Brusegan V, Bontempelli M, Ruggenenti P. Rituximab for idiopathic membranous nephropathy. Lancet. 2002;360(9337):923-924. 19. Ruggenenti P, Chiurchiu C, Abbate M, et al. Rituximab for idiopathic membranous nephropathy: who can benefit? Clin J Am Soc Nephrol. 2006;1(4):738-748. 20. Cravedi P, Ruggenenti P, Sghirlanzoni MC, Remuzzi G. Titrating rituximab to circulating B cells to optimize lymphocytolytic therapy in idiopathic membranous nephropathy. Clin J Am Soc Nephrol. 2007;2(5):932-937. 21. Fervenza FC, Cosio FG, Erickson SB, et al. Rituximab treatment of idiopathic membranous nephropathy. Kidney Int. 2008;73(1): 117-125. 22. Fervenza FC, Abraham RS, Erickson SB, et al. Rituximab therapy in idiopathic membranous nephropathy: a 2-year study. Clin J Am Soc Nephrol. 2010;5(12):2188-2198. 23. Ruggenenti P, Cravedi P, Chianca A, et al. Rituximab in idiopathic membranous nephropathy. J Am Soc Nephrol. 2012;23(8): 1416-1425. 24. Segarra A, Praga M, Ramos N, et al. Successful treatment of membranous glomerulonephritis with rituximab in calcineurin inhibitor-dependent patients. Clin J Am Soc Nephrol. 2009;4(6): 1083-1088. 25. Beck LH Jr, Fervenza FC, Beck DM, et al. Rituximab-induced depletion of anti-PLA2R autoantibodies predicts response in membranous nephropathy. J Am Soc Nephrol. 2011;22(8):15431550. 26. ClinicialTrials.gov: A service of the U.S. National Institutes of Health. Available at: www.clinicaltrials.gov. Accessed: July 1, 2013. 27. Stohl W, Hiepe F, Latinis KM, et al. Belimumab reduces autoantibodies, normalizes low complement levels, and reduces select B cell populations in patients with systemic lupus erythematosus. Arthritis Rheum. 2012;64(7):2328-2337. 28. Schwartz MM. The role of podocyte injury in the pathogenesis of focal segmental glomerulosclerosis. Ren Fail. 2000;22(6):663-684. 29. D’Agati VD, Fogo AB, Bruijn JA, Jennette JC. Pathologic classification of focal segmental glomerulosclerosis: a working proposal. Am J Kidney Dis. 2004;43(2):368-382. 30. Deegens JK, Wetzels JF. Immunosuppressive treatment of focal segmental glomerulosclerosis: lessons from a randomized controlled trial. Kidney Int. 2011;80(8):798-801. 31. Prytula A, Iijima K, Kamei K, et al. Rituximab in refractory nephrotic syndrome. Pediatr Nephrol. 2010;25(3):461-468. 32. Ito S, Kamei K, Ogura M, et al. Maintenance therapy with mycophenolate mofetil after rituximab in pediatric patients with steroiddependent nephrotic syndrome. Pediatr Nephrol. 2011;26(10): 1823-1828. 33. Gulati A, Sinha A, Jordan SC, et al. Efficacy and safety of treatment with rituximab for difficult steroid-resistant and -dependent nephrotic syndrome: multicentric report. Clin J Am Soc Nephrol. 2010;5(12):2207-2212. 34. Kemper MJ, Gellermann J, Habbig S, et al. Long-term follow-up after rituximab for steroid-dependent idiopathic nephrotic syndrome. Nephrol Dial Transplant. 2012;27(5):1910-1915. 35. Ito S, Kamei K, Ogura M, et al. Survey of rituximab treatment for childhood-onset refractory nephrotic syndrome. Pediatr Nephrol. 2013;28(2):257-264. 36. Tellier S, Brochard K, Garnier A, et al. Long-term outcome of children treated with rituximab for idiopathic nephrotic syndrome. Pediatr Nephrol. 2013;28(6):911-918. 37. Kronbichler A, Konig P, Busch M, Wolf G, Mayer G, Rudnicki M. Rituximab in adult patients with multi-relapsing/steroid-dependent minimal change disease and focal segmental glomerulosclerosis: a report of 5 cases. Wien Klin Wochenschr. 2013;125(11-12):328-333. 38. Munyentwali H, Bouachi K, Audard V, et al. Rituximab is an efficient and safe treatment in adults with steroid-dependent minimal change disease. Kidney Int. 2013;83(3):511-516.

39. Sinha A, Bagga A, Gulati A, Hari P. Short-term efficacy of rituximab versus tacrolimus in steroid-dependent nephrotic syndrome. Pediatr Nephrol. 2012;27(2):235-241. 40. Kamei K, Ito S, Nozu K, et al. Single dose of rituximab for refractory steroid-dependent nephrotic syndrome in children. Pediatr Nephrol. 2009;24(7):1321-1328. 41. Fujinaga S, Hirano D, Nishizaki N, et al. Single infusion of rituximab for persistent steroid-dependent minimal-change nephrotic syndrome after long-term cyclosporine. Pediatr Nephrol. 2010;25(3): 539-544. 42. Kyrieleis HA, Lowik MM, Pronk I, et al. Long-term outcome of biopsy-proven, frequently relapsing minimal-change nephrotic syndrome in children. Clin J Am Soc Nephrol. 2009;4(10):1593-1600. 43. Ravani P, Ponticelli A, Siciliano C, et al. Rituximab is a safe and effective long-term treatment for children with steroid and calcineurin inhibitor-dependent idiopathic nephrotic syndrome. Kidney Int. 2013;84(5):1025-1033. 44. Sellier-Leclerc AL, Baudouin V, Kwon T, et al. Rituximab in steroid-dependent idiopathic nephrotic syndrome in childhood–follow-up after CD19 recovery. Nephrol Dial Transplant. 2012; 27(3):1083-1089. 45. Takei T, Itabashi M, Moriyama T, et al. Effect of single-dose rituximab on steroid-dependent minimal-change nephrotic syndrome in adults. Nephrol Dial Transplant. 2013;28(5):1225-1232. 46. Ravani P, Magnasco A, Edefonti A, et al. Short-term effects of rituximab in children with steroid- and calcineurin-dependent nephrotic syndrome: a randomized controlled trial. Clin J Am Soc Nephrol. 2011;6(6):1308-1315. 47. Kari JA, El-Morshedy SM, El-Desoky S, Alshaya HO, Rahim KA, Edrees BM. Rituximab for refractory cases of childhood nephrotic syndrome. Pediatr Nephrol. 2011;26(5):733-737. 48. Tarshish P, Tobin JN, Bernstein J, Edelmann CM Jr. Cyclophosphamide does not benefit patients with focal segmental glomerulosclerosis. A report of the International Study of Kidney Disease in Children. Pediatr Nephrol. 1996;10(5):590-593. 49. Magnasco A, Ravani P, Edefonti A, et al. Rituximab in children with resistant idiopathic nephrotic syndrome. J Am Soc Nephrol. 2012; 23(6):1117-1124. 50. Fernandez-Fresnedo G, Segarra A, Gonzalez E, et al. Rituximab treatment of adult patients with steroid-resistant focal segmental glomerulosclerosis. Clin J Am Soc Nephrol. 2009;4(8):1317-1323. 51. Bagga A, Sinha A, Moudgil A. Rituximab in patients with the steroid-resistant nephrotic syndrome. N Engl J Med. 2007;356(26): 2751-2752. 52. Maas RJ, Deegens JK, van den Brand JA, Cornelissen EA, Wetzels JF. A retrospective study of focal segmental glomerulosclerosis: clinical criteria can identify patients at high risk for recurrent disease after first renal transplantation. BMC Nephrol. 2013;14:47. 53. Ponticelli C. Recurrence of focal segmental glomerular sclerosis (FSGS) after renal transplantation. Nephrol Dial Transplant. 2010; 25(1):25-31. 54. Araya CE, Dharnidharka VR. The factors that may predict response to rituximab therapy in recurrent focal segmental glomerulosclerosis: a systematic review. J Transplant. 2011;2011:374213. 55. Kumar J, Shatat IF, Skversky AL, et al. Rituximab in post-transplant pediatric recurrent focal segmental glomerulosclerosis. Pediatr Nephrol. 2013;28(2):333-338. 56. Guigonis V, Dallocchio A, Baudouin V, et al. Rituximab treatment for severe steroid- or cyclosporine-dependent nephrotic syndrome: a multicentric series of 22 cases. Pediatr Nephrol. 2008;23(8):12691279. 57. Brezinschek HP, Rainer F, Brickmann K, Graninger WB. B lymphocyte-typing for prediction of clinical response to rituximab. Arthritis Res Ther. 2012;14(4):R161. 58. Breedveld F, Agarwal S, Yin M, et al. Rituximab pharmacokinetics in patients with rheumatoid arthritis: B-cell levels do not correlate with clinical response. J Clin Pharmacol. 2007;47(9):1119-1128.

B Cell Suppression in Primary Glomerular Disease

59. Sugiura H, Takei T, Itabashi M, et al. Effect of single-dose rituximab on primary glomerular diseases. Nephron Clin Pract. 2011;117(2):c98-c105. 60. Dillon JJ, Hladunewich M, Haley WE, Reich HN, Cattran DC, Fervenza FC. Rituximab therapy for Type I membranoproliferative glomerulonephritis. Clin Nephrol. 2012;77(4):290-295. 61. Hoxha E, Stahl RA, Harendza S. Rituximab in adult patients with immunosuppressive-dependent minimal change disease. Clin Nephrol. 2011;76(2):151-158.

181

62. Tsagalis G, Psimenou E, Nakopoulou L, Laggouranis A. Combination treatment with plasmapheresis and rituximab for recurrent focal segmental glomerulosclerosis after renal transplantation. Artif Organs. 2011;35(4):420-425. 63. Audard V, Kamar N, Sahali D, et al. Rituximab therapy prevents focal and segmental glomerulosclerosis recurrence after a second renal transplantation. Transpl Int. 2012;25(5): e62-e66.