A Multicenter Randomized Controlled Trial of Rituximab versus Cyclosporine in the Treatment of Idiopathic Membranous Nephropathy (MENTOR)

Anti-Phospholipase A2 Receptor 1 and Anti-Cysteine Rich Antibodies, Domain Recognition and Rituximab Efficacy in Membranous Nephropathy: A Prospective Cohort Study

RATIONALE & OBJECTIVE

Proteinuria and anti-phospholipase A2 receptor 1 (anti-PLA2R1) antibody titers are associated with primary membranous nephropathy (MN) outcomes. We evaluated the association of antibodies against the cysteine-rich (CysR) and C-type lectin 1, 7, and 8 (CTLD1, CTLD7, and CTLD8) domains of PLA2R1 with MN outcomes.

STUDY DESIGN

Prospective cohort study.

SETTING & PARTICIPANTS

One-hundred-thirteen consecutive, consenting patients referred to the Nephology Unit of the Azienda-Socio-Sanitaria-Territoriale (ASST) Papa Giovanni XXIII (Bergamo, Italy) with PLA2R1-related, biopsy-proven MN whose persistent nephrotic syndrome (NS) was managed conservatively for>6 months and were monitored with serial evaluations of proteinuria, autoantibodies (by enzyme-linked immunosorbent assay), and clinical outcomes.

EXPOSURE

Rituximab.

OUTCOME

Complete (proteinuria<0.3g/24h) or partial (proteinuria≥0.3g/24h and<3.0g/24h with>50% reduction vs basal) NS remission.

ANALYTICAL APPROACH

Univariable and multivariable Cox regression analyses.

RESULTS

All patients had anti-CysR antibodies; 62 (54.9%) were multidomain recognizers. Anti-PLA2R1 and anti-CysR antibody titers were strongly correlated at baseline (P<0.001, r=0.934), 6 months (P<0.001, r=0.964), and 12 months (P<0.001, r=0.944). During a median follow-up of 37.1 (IQR, 20.3-56.9) months, 71 patients (62.8%) achieved either complete or partial remission of their NS. Lower baseline anti-PLA2R1 (HR, 0.997 [95% CI, 0.996-0.999], P=0.002) and anti-CysR [HR, 0.996 [95% CI, 0.993-0.998], P=0.001) titers were associated with a higher probability of remission, along with female sex, lower proteinuria, and lower serum creatinine levels (P<0.05 for all comparisons). Anti-CTLD antibodies were not associated with outcomes. At 6 and 12 months, compared to baseline, anti-PLA2R1 and anti-CysR antibody titers decreased more in patients progressing to partial or complete remission than in those without remission (P<0.05 for all comparisons).

LIMITATIONS

Observational design.

CONCLUSIONS

In PLA2R1-related MN, anti-PLA2R1 and anti-CysR antibodies similarly predict rituximab efficacy independent of PLA2R1 domain recognition. The choice between these tests should be dictated by feasibility and costs. Evaluating anti-CTLD antibodies appears unnecessary.

PLAIN-LANGUAGE SUMMARY

Primary membranous nephropathy (MN), a leading cause of nephrotic syndrome (NS) in adults, is an autoimmune disease caused by autoantibodies binding to the podocyte antigen phospholipase A2 receptor 1 (PLA2R1). We assessed whether the effects of anti-CD20 cytolytic therapy with the monoclonal antibody rituximab are associated with detection rates and levels of anti-PLA2R1 antibodies and antibodies against PLA2R1 domains such as cysteine-rich (CysR), and C-type lectin 1, 7, and 8 (CTLD1, 7, and 8), in patients with PLA2R1-related MN and persistent NS. The probability of rituximab-induced complete or partial NS remission was associated with baseline anti-PLA2R1 and anti-CysR antibody titers, but not with anti-CTLD1, 7 and 8 antibodies or multidomain recognition. Integrated evaluation of anti-PLA2R1 or anti-CysR antibodies with proteinuria and kidney function may play a role in monitoring the effects of rituximab in patients with PLA2R1-related NS and MN.

The Safety and Efficacy of Rituximab-Based Regimen in Atypical Membranous Nephropathy: A Single Center Retrospective Cohort Study

Purpose

There are increasing reports of atypical membranous nephropathy (AMN) cases with similar pathological characteristics to secondary membranous nephropathy (SMN) without definite underlying causes. Although rituximab has become a first-line option in treating idiopathic membranous nephropathy (IMN), the efficacy and safety of rituximab-based regimen for AMN is not clear.

Patients and Methods

This is a retrospective, single-center study. AMN patients who received rituximab-based therapy were included. IMN patients treated with rituximab during the same period were selected as the control group matched by gender, sex, baseline urinary protein and albumin levels. Baseline data and follow-up data were collected.

Results

A total of 20 AMN patients and 40 IMN patients were included. The baseline levels of urinary protein were comparable between the two groups [6.77 (IQR 3.34, 11.49) g/24 h vs 6.47 (IQR 3.4, 10.76) g/24 h, P=0.944]. The baseline levels of serum albumin were 26.15±6.71 g/L and 26.8±5.54 g/L (P=0.689) respectively. The cumulative remission rate for rituximab-based treatment at the 12th month was lower in AMN group than IMN group [13 (65%) vs 36 (90%), P=0.045]. In AMN group, non-responders showed a higher level of proteinuria and a worse renal function at baseline than those of responders. There was no significant difference in the overall adverse events or serious adverse events between the two groups.

Conclusion

In our study, AMN patients obtained proteinuria remission in a lower percentage compared with IMN patients. In general, rituximab-based therapy is effective in AMN patients with an acceptable safety profile.

Membranous nephropathy: Mechanistic insights and therapeutic perspectives

Membranous nephropathy (MN) is one of the most common causes of non-diabetic nephrotic syndrome in adults. About 80% of cases are renal limited (primary MN) and 20% are associated with other systemic diseases or exposures (secondary MN). Autoimmune reaction is the main pathogenic factor of MN, and the discovery of autoantigens including the phospholipase A₂ receptor and thrombospondin type-1 domain-containing protein 7A has led to new insights into the pathogenesis, they can induce humoral immune responses led by IgG₄ makes them suitable for the diagnosis and monitoring of MN. In addition, complement activation, genetic susceptibility genes and environmental pollution are also involved in MN immune response. In clinical practice, due to the spontaneous remission of MN, the combination of supportive therapy and pharmacological treatment is widely used. Immunosuppressive drugs are the cornerstone of MN treatment, and the dangers and benefits of this approach vary from person to person. In summary, this review provides a more comprehensive review of the immune pathogenesis, interventions and unresolved issues of MN in the hope of providing some new ideas for clinical and scientific researchers in the treatment of MN.

From KDIGO 2012 towards KDIGO 2021 in idiopathic membranous nephropathy guidelines: what has changed over the last 10 years?

The recommendations in the Kidney Disease: Improving Global Outcomes (KDIGO) 2021 guidelines regarding Idiopathic Membranous Nephropathy (IMN) management include significant changes as compared to those published in 2012. According to the recent guidelines, a biopsy is not always needed for IMN diagnosis; since diagnosis can be allowed for by the detection of circulating antibodies against the M-type transmembrane phospholipase A2 receptor (anti-PLA2R). Moreover, alterations in anti-PLA2R concentrations, along with other serum and urinary markers, may guide further follow-up. The findings of numerous recent studies which compared different immunosuppressive treatments resulted in substantial changes in treatment indications in the KDIGO 2021 guidelines, suggesting the stratification of patients into four risk categories. The definition of resistant cases and relapses was likewise modified. All the above will lead to a more granular and personalized approach, whose results need to be tested over time. In this commentary, we discuss the changes in the 2012 and 2021 guidelines, adding information from the most recent literature.

A Guide for Adult Nephrologists and Hematologists to Managing Atypical Hemolytic Uremic Syndrome and C3 Glomerulopathy in Teens Transitioning to Young Adults

Atypical hemolytic uremic syndrome and C3 glomerulopathy/immune complex membranoproliferative glomerulonephritis are ultra-rare chronic, complement-mediated diseases with childhood manifestation in a majority of cases. Transition of clinical care of patients from pediatric to adult nephrologists-typically with controlled disease in native or transplant kidneys in case of atypical hemolytic uremic syndrome and often with chronic progressive disease despite treatment efforts in case of C3 glomerulopathy/immune complex membranoproliferative glomerulonephritis-identifies a challenging juncture in the journey of these patients. Raising awareness for the vulnerability of this patient cohort; providing education on disease pathophysiology and management including the use of new, high-precision complement antagonists; and establishing an ongoing dialog of patients, families, and all members of the health care team involved on either side of the age divide will be inevitable to ensure optimal patient outcomes and a safe transition of these patients to adulthood.

Revisiting immunological and clinical aspects of membranous nephropathy

Idiopathic or primary membranous nephropathy (IMN) is one of the most frequent causes of nephrotic syndrome in adults and the elderly. It is characterized by a thickening of the wall of the glomerular capillaries due to the presence of immune complex deposits. 85% of membranous nephropathy cases are classified as primary or idiopathic (IMN). The rest are of secondary origin (SMN), caused by autoimmune conditions or malignant tumors as lung cancer, colon and melanomas. It is an organ-specific autoimmune disease in which the complement system plays an important role with the formation of the membrane attack complex (MAC; C5b-9), which produces an alteration of the podocyte structure. The antigen responsible for 70-80% of IMN is a podocyte protein called M-type phospholipase A2 receptor (PLA2R). More recently, another podocyte antigen has been identified, the "Thrombospondin type-1 domain-containing 7A" (THSD7A), which is responsible for 10% of the cases of negative IMN for anti- PLA2R.

How Times Have Changed! A Cornucopia of Antigens for Membranous Nephropathy

The identification of the major target antigen phospholipase A2 receptor (PLA2R) in the majority of primary (idiopathic) cases of membranous nephropathy (MN) has been followed by the rapid identification of numerous minor antigens that appear to define phenotypically distinct forms of disease. This article serves to review all the known antigens that have been shown to localize to subepithelial deposits in MN, as well as the distinctive characteristics associated with each subtype of MN. We will also shed light on the novel proteomic approaches that have allowed identification of the most recent antigens. The paradigm of an antigen normally expressed on the podocyte cell surface leading to in-situ immune complex formation, complement activation, and subsequent podocyte injury will be discussed and challenged in light of the current repertoire of multiple MN antigens. Since disease phenotypes associated with each individual target antigens can often blur the distinction between primary and secondary disease, we encourage the use of antigen-based classification of membranous nephropathy.

Immunosuppressive treatment for primary membranous nephropathy in adults with nephrotic syndrome

BACKGROUND

Primary membranous nephropathy (PMN) is a common cause of nephrotic syndrome in adults. Without treatment, approximately 30% of patients will experience spontaneous remission and one third will have persistent proteinuria. Approximately one-third of patients progress toward end-stage kidney disease (ESKD) within 10 years. Immunosuppressive treatment aims to protect kidney function and is recommended for patients who do not show improvement of proteinuria by supportive therapy, and for patients with severe nephrotic syndrome at presentation due to the high risk of developing ESKD. The efficacy and safety of different immunosuppressive regimens are unclear. This is an update of a Cochrane review, first published in 2004 and updated in 2013.

OBJECTIVES

The aim was to evaluate the safety and efficacy of different immunosuppressive treatments for adult patients with PMN and nephrotic syndrome.

SEARCH METHODS

We searched the Cochrane Kidney and Transplant Register of Studies up to 1 April 2021 with support from the Cochrane Kidney and Transplant Information Specialist using search terms relevant to this review. Studies in the Register were identified through searches of CENTRAL, MEDLINE, and EMBASE, conference proceedings, the International Clinical Trials Register (ICTRP) Search Portal and ClinicalTrials.gov.

SELECTION CRITERIA

Randomised controlled trials (RCTs) investigating effects of immunosuppression in adults with PMN and nephrotic syndrome were included.

DATA COLLECTION AND ANALYSIS

Study selection, data extraction, quality assessment, and data synthesis were performed using Cochrane-recommended methods. Summary estimates of effect were obtained using a random-effects model, and results were expressed as risk ratios (RR) and their 95% confidence intervals (CI) for dichotomous outcomes, and mean difference (MD) and 95% CI for continuous outcomes. Confidence in the evidence was assessed using the Grading of Recommendations Assessment, Development and Evaluation (GRADE) approach.

MAIN RESULTS

Sixty-five studies (3807 patients) were included. Most studies exhibited a high risk of bias for the domains, blinding of study personnel, participants and outcome assessors, and most studies were judged unclear for randomisation sequence generation and allocation concealment. Immunosuppressive treatment versus placebo/no treatment/non-immunosuppressive treatment In moderate certainty evidence, immunosuppressive treatment probably makes little or no difference to death, probably reduces the overall risk of ESKD (16 studies, 944 participants: RR 0.59, 95% CI 0.35 to 0.99; I² = 22%), probably increases total remission (complete and partial) (6 studies, 879 participants: RR 1.44, 95% CI 1.05 to 1.97; I² = 73%) and complete remission (16 studies, 879 participants: RR 1.70, 95% CI 1.05 to 2.75; I² = 43%), and probably decreases the number with doubling of serum creatinine (SCr) (9 studies, 447 participants: RR 0.46, 95% CI 0.26 to 0.80; I² = 21%). However, immunosuppressive treatment may increase the number of patients relapsing after complete or partial remission (3 studies, 148 participants): RR 1.73, 95% CI 1.05 to 2.86; I² = 0%) and may lead to a greater number experiencing temporary or permanent discontinuation/hospitalisation due to adverse events (18 studies, 927 participants: RR 5.33, 95% CI 2.19 to 12.98; I² = 0%). Immunosuppressive treatment has uncertain effects on infection and malignancy. Oral alkylating agents with or without steroids versus placebo/no treatment/steroids Oral alkylating agents with or without steroids had uncertain effects on death but may reduce the overall risk of ESKD (9 studies, 537 participants: RR 0.42, 95% CI 0.24 to 0.74; I² = 0%; low certainty evidence). Total (9 studies, 468 participants: RR 1.37, 95% CI 1.04 to 1.82; I² = 70%) and complete remission (8 studies, 432 participants: RR 2.12, 95% CI 1.33 to 3.38; I² = 37%) may increase, but had uncertain effects on the number of patients relapsing, and decreasing the number with doubling of SCr. Alkylating agents may be associated with a higher rate of adverse events leading to discontinuation or hospitalisation (8 studies 439 participants: RR 6.82, 95% CI 2.24 to 20.71; I² = 0%). Oral alkylating agents with or without steroids had uncertain effects on infection and malignancy. Calcineurin inhibitors (CNI) with or without steroids versus placebo/no treatment/supportive therapy/steroids We are uncertain whether CNI with or without steroids increased or decreased the risk of death or ESKD, increased or decreased total or complete remission, or reduced relapse after complete or partial remission (low to very low certainty evidence). CNI also had uncertain effects on decreasing the number with a doubling of SCr, temporary or permanent discontinuation or hospitalisation due to adverse events, infection, or malignancy. Calcineurin inhibitors (CNI) with or without steroids versus alkylating agents with or without steroids We are uncertain whether CNI with or without steroids increases or decreases the risk of death or ESKD. CNI with or without steroids may make little or no difference to total remission (10 studies, 538 participants: RR 1.01, 95% CI 0.89 to 1.15; I² = 53%; moderate certainty evidence) or complete remission (10 studies, 538 participants: RR 1.15, 95% CI 0.84 to 1.56; I² = 56%; low certainty evidence). CNI with or without steroids may increase relapse after complete or partial remission. CNI with or without steroids had uncertain effects on SCr increase, adverse events, infection, and malignancy. Other immunosuppressive treatments Other interventions included azathioprine, mizoribine, adrenocorticotropic hormone, traditional Chinese medicines, and monoclonal antibodies such as rituximab. There were insufficient data to draw conclusions on these treatments.

AUTHORS' CONCLUSIONS

This updated review strengthened the evidence that immunosuppressive therapy is probably superior to non-immunosuppressive therapy in inducing remission and reducing the number of patients that progress to ESKD. However, these benefits need to be balanced against the side effects of immunosuppressive drugs. The number of included studies with high-quality design was relatively small and most studies did not have adequate follow-up. Clinicians should inform their patients of the lack of high-quality evidence. An alkylating agent (cyclophosphamide or chlorambucil) combined with a corticosteroid regimen had short- and long-term benefits, but this was associated with a higher rate of adverse events. CNI (tacrolimus and cyclosporin) showed equivalency with alkylating agents however, the certainty of this evidence remains low. Novel immunosuppressive treatments with the biologic rituximab or use of adrenocorticotropic hormone require further investigation and validation in large and high-quality RCTs.

The clinical implication of monoclonal gammopathies: monoclonal gammopathy of undetermined significance and of renal significance

Monoclonal gammopathy of renal significance (MGRS) has introduced a new perspective to several well-known disease entities impacting nephrology, haematology and pathology. Given the constantly changing disease spectrum of these entities, it is clinically imperative to establish diagnostic and treatment pathways supported by evidence-based medicine. MGRS is a disease of the kidney, secondary to plasma cell clonal proliferation or immune dysfunction, requiring therapeutic intervention to eradicate the offending clone. To fully understand the disease(s), it is prerequisite to determine the significance of the findings. The diagnostic work up should be extensive due to the wide heterogeneity of clinical presentation, ultimately necessitating kidney biopsy. Particular patient profiles such as AL amyloidosis, which may be diagnosed through biopsies of other tissues/organs, may be an exception. Treatment decisions should be formulated by multi-disciplinary consensus: nephrologists, haematologists and pathologists. The ultimate goal in managing MGRS is eradication of the offending plasma cell clone which requires targeted chemotherapy and, in eligible cases, haematopoietic stem cell transplantation. We present a review of diagnostic procedures, treatment options and advances in the last few years in the management of MGRS in an effort to acquaint specialists with this new face of several older diseases.

Treatment Patterns Among Adults and Children With Membranous Nephropathy in the Cure Glomerulonephropathy Network (CureGN)

Introduction

The 2012 Kidney Disease: Improving Global Outcomes (KDIGO) Clinical Practice Guidelines for Glomerulonephritis recommend that patients with membranous nephropathy (MN) at risk for progression receive immunosuppressive therapy (IST), usually after 6 months of observation. A cyclophosphamide (CYC) or calcineurin inhibitor (CNI)–based regimen is recommended as first-line IST. However, the extent to which KDIGO recommendations are adopted in practice remains largely unknown.

Methods

We evaluated prescribing practice among patients with primary MN (diagnosed 2010–2018) enrolled in the Cure Glomerulonephropathy Network (CureGN) cohort study. We also evaluated the availability of testing for phospholipase A2 receptor (PLA2R) in the contemporary era.

Results

Among 361 patients (324 adults and 37 children) with MN who were IST-naïve at biopsy and had at least 6 months of follow-up, 55% of adults and 58% of children initiated IST <6 months after biopsy. Of these, 1 in 5 had no indication for (i.e., urine protein-to-creatinine ratio [uPCR] <4 g/g) or an apparent contraindication to (i.e., an estimated glomerular filtration rate [eGFR] <30 ml/min per 1.73 m²) IST. As first-line IST, half of treated patients received either CYC (16% of adults; 0% of children) or a CNI (40% and 46%, respectively), whereas 1 in 5 received corticosteroid monotherapy (20% and 27%, respectively) and 1 in 6 rituximab (15% and 15%, respectively). More than 80% of surveyed centers had access to PLA2R testing.

Conclusion

These findings suggest that providers are not aware of, or lack confidence in, current KDIGO guidelines for MN. Treatment patterns observed in this cohort might critically inform the drafting of planned updates to KDIGO guidelines.

Rituximab or Cyclosporine in the Treatment of Membranous Nephropathy

BACKGROUND

B-cell anomalies play a role in the pathogenesis of membranous nephropathy. B-cell depletion with rituximab may therefore be noninferior to treatment with cyclosporine for inducing and maintaining a complete or partial remission of proteinuria in patients with this condition.

METHODS

We randomly assigned patients who had membranous nephropathy, proteinuria of at least 5 g per 24 hours, and a quantified creatinine clearance of at least 40 ml per minute per 1.73 m² of body-surface area and had been receiving angiotensin-system blockade for at least 3 months to receive intravenous rituximab (two infusions, 1000 mg each, administered 14 days apart; repeated at 6 months in case of partial response) or oral cyclosporine (starting at a dose of 3.5 mg per kilogram of body weight per day for 12 months). Patients were followed for 24 months. The primary outcome was a composite of complete or partial remission of proteinuria at 24 months. Laboratory variables and safety were also assessed.

RESULTS

A total of 130 patients underwent randomization. At 12 months, 39 of 65 patients (60%) in the rituximab group and 34 of 65 (52%) in the cyclosporine group had a complete or partial remission (risk difference, 8 percentage points; 95% confidence interval [CI], -9 to 25; P = 0.004 for noninferiority). At 24 months, 39 patients (60%) in the rituximab group and 13 (20%) in the cyclosporine group had a complete or partial remission (risk difference, 40 percentage points; 95% CI, 25 to 55; P<0.001 for both noninferiority and superiority). Among patients in remission who tested positive for anti-phospholipase A₂ receptor (PLA2R) antibodies, the decline in autoantibodies to anti-PLA2R was faster and of greater magnitude and duration in the rituximab group than in the cyclosporine group. Serious adverse events occurred in 11 patients (17%) in the rituximab group and in 20 (31%) in the cyclosporine group (P = 0.06).

CONCLUSIONS

Rituximab was noninferior to cyclosporine in inducing complete or partial remission of proteinuria at 12 months and was superior in maintaining proteinuria remission up to 24 months. (Funded by Genentech and the Fulk Family Foundation; MENTOR ClinicalTrials.gov number, NCT01180036.).

Impact of Recent Clinical Trials on Nephrology Practice: Are We in a Stagnant Era?

BACKGROUND

Although renal replacement therapy prevents death from uremia, survival among patients with acute and chronic kidney diseases (CKD) remains an imperative concern. The expected life span of US dialysis patients 60-64 years of age is approximately 4.5 years; this is similar to that of patients with lung cancer. Despite substantial progress in many medical specialties over the past decades (e.g., notable reductions in myocardial infarction, stroke, and mortality rates in the general population), survival among dialysis patients has not improved significantly over the same period. A few decades ago, HIV infection and AIDS were pretty much a death sentence. Because of progress in HIV treatment, now it can be controlled with a daily pill, and ongoing research is pushing treatment even further and controls the virus with longer-acting treatment. A cure is no longer impossible for HIV and other viral infections such as hepatitis B and C and many malignancies, but so far there is no cure for CKD.

SUMMARY

Billions of dollars have been spent on kidney disease research in the past decades, with no tangible progress in clinical practice. The challenges of improving the quantity and quality of trials in nephrology are enormous. The number of randomized controlled trials (RCTs) published in nephrology is lower than that in other medical subspecialties, and most of the big RCTs in nephrology yield negative results. Nephrology studies evaluating hard clinical endpoints or surrogate endpoints are scarce.

KEY MESSAGE

Herein we discuss the slow progress in nephrology research that has impacted clinical practice over the last couple of decades and highlight the major obstacles, challenges, and potential solutions.

Primary membranous nephropathy: comprehensive review and historical perspective

Membranous nephropathy (MN) is the most common cause of nephrotic syndrome in non-diabetic Caucasian adults over 40 years of age. It has an estimated incidence of 8–10 cases per 1 million. Fifty per cent of patients diagnosed with primary MN continue to have nephrotic syndrome and 30% of patients may progress to end-stage renal disease over 10 years. Although it was recognised as a distinct clinic-pathological entity in 1940s by immunofluorescence and electron microscopy, the pathogenesis and treatment have become more apparent only in the last decade. Discovery of M-type phospholipase A2 receptor (PLA2R) antibodies and thrombospondin type 1 domain-containing 7A antibodies has given new perspectives in understanding the pathogenesis of the disease process. Anti-PLA2R antibody is the first serologic marker that has promising evidence to be used as a tool to prognosticate the course of the disease. More importantly, therapeutic agents such as rituximab and adrenocorticotropic hormone analogues are the newer therapeutic options that should be considered in the therapy of primary MN.

Rituximab Exhibits Altered Pharmacokinetics in Patients With Membranous Nephropathy

BACKGROUND

Rituximab (RTX) is a chimeric monoclonal anti-CD20 antibody used off-label in the treatment of membranous nephropathy (MN). Unfortunately, limited information is available on the pharmacokinetics of therapeutic proteins such as RTX in patients with glomerular kidney diseases.

OBJECTIVE

The current study evaluated RTX pharmacokinetics in patients with MN (n = 20) who received 4 RTX weekly intravenous infusions (375 mg/m²) over a month, with a repeat of the identical treatment at 6 months. Baseline patient characteristics were gender (17 male/3 female), age (49 ± 13 years), and body surface area (2.2 ± 0.24 m²).

METHODS

Compartmental pharmacokinetic analyses were conducted using Phoenix, and comparisons of these parameters were made between the MN patients and published data from 2 reference populations without kidney diseases (follicular lymphoma and autoimmune disorders).

RESULTS

Patients with MN exhibited a shorter half-life, reduced volume of central compartment, decreased area under the serum concentration-time curve (exposure), and increased RTX clearance from the central compartment versus previous reports in the reference patient populations.

CONCLUSIONS AND RELEVANCE

These results suggest that shorter half-life and lower exposures to RTX in patients with MN may necessitate higher doses and/or changes to dosing frequency to optimize the relationships between serum concentrations and therapeutic effects.

Urinary N-acetyl-β-glucosaminidase and estimated Glomerular filtration rate may identify patients to be treated with immuno-suppression at diagnosis in idiopathic membranous nephropathy

AIM

The clinical course of idiopathic membranous nephropathy (IMN) varies from spontaneous remission of nephrotic syndrome (NS) to end-stage renal disease (ESRD). The aim of the study was baseline identification of patients with high risk of progression for which immunosuppressive therapy is mandatory.

METHODS

Eighty-six IMN subjects were followed for a median of 69 months (range 6-253). Receiver operating characteristic curve and Cox proportional hazards model were used to evaluate prognostic factors for progression, defined as ESRD or estimated glomerular filtration rate (eGFR) reduction ≥50% of baseline.

RESULTS

Among all, 24 subjects had progression. Area under the ROC curve of N-acetyl-β-glucosaminidase/creatinine ratio (NAG/C) were significantly higher than proteinuria/24 h (0.770 and 0.637 respectively, P = 0.018). In Cox proportional hazards regression analysis, NAG/C and eGFR were independent predictors of progression. Compared to lowest tertile of NAG/C (<9.4 UI/gC) or highest tertile of eGFR (≥88 mL/min per 1.73m² ), the multivariable-adjusted hazard ratio of highest tertile of NAG/C (≥19.2) was 18.97 (95%CI, 1.70-211.86) and lowest tertile of eGFR (<59) was 11.58 (95%CI, 2.02-66.29). Subjects with high NAG/C or low eGFR (high-risk, n = 43) had greater progression rate compared to moderate to low NAG/C and high eGFR (low-risk, n = 43) with or without NS at baseline (Log-rank test P = 0.001 and 0.006, respectively). In NS subjects (n = 65), high-risk group progression rate was significantly higher (91% vs. 29%, P = 0.003) and remission rate significantly lower (0% vs. 42%, p < 0.001) in non-immunosuppressed compared to steroids and cyclophosphamide treated patients; no significant differences were observed in low-risk group.

CONCLUSION

Idiopathic membranous nephropathy subjects with high NAG/C and low eGFR have greater risk of progression, and immunosuppressive treatment is suggested at diagnosis.

Intravenous pulse cyclophosphamide and steroids induce immunological and clinical remission in New-incident and relapsing primary membranous nephropathy

AIM

Primary membranous nephropathy is associated with progression to end stage renal diseasein some patients. Standard therapy with cyclical cyclophosphamide and corticosteroids can be associated with significant adverse effects. We aimed to assess immunological and clinical response with intravenous pulse cyclophosphamide and oral steroids in patients with severe nephrotic syndrome - in a prospective observational cohort study.

METHODS

A total of 17 consecutive patients (nine new-incident and eight relapses) with severe nephrotic syndrome received monthly intravenous pulse cyclophosphamide and oral steroids after failure to achieve remission with supportive therapy. Immunosuppressive therapy was discontinued at 6 months or earlier if proteinuria regressed to <100 mg/mmol and patients were followed for 12 months. Achievement of partial remission was primary outcome; changes in clinical parameters and anti-PLA₂ R were secondary outcomes.

RESULTS

Dose of cyclophosphamide received was 5.4 g in New-incident patients and 4.2 g in patients with relapses. All 17 patients achieved partial remission within 6 months: proteinuria improved from 656 to 102 mg/mmol at 6 months and 55 mg/mmol at 12 months (P < 0.001); eGFR improved from 31 to 48 mL/min per 1.73 m² at 6 months and 45 mL/min per 1.73 m² at 12 months (P < 0.05). Anti-PLA₂ R levels reduced from 244 to 10 U/L at 6 months and 10 U/L at 12 months (P < 0.001). Two out of nine patients in the New-incident group developed subsequent relapse. Cumulative doses of cyclophosphamide and steroids that patients received was about half of the standard regime.

CONCLUSION

Pulse cyclophosphamide with oral steroids induced immunological and clinical partial remission at significantly reduced doses in primary membranous nephropathy.

Rituximab as a front-line therapy for adult-onset minimal change disease with nephrotic syndrome

Minimal change disease (MCD) accounts for 15% of adult nephrotic syndrome (NS) cases. Adult-MCD patients may have more severe clinical features than pediatric patients. In children, Rituximab (RTX) has been used since 2006 to treat frequently relapsing NS. In adults, data about the efficacy of RTX for MCD are limited. We report our experience on the use of RTX in adult biopsy-proven MCD. Our series includes 6 adult patients (2 males and 4 females), age 45–73 years, treated with RTX (4 weekly doses of 375 mg/m²). Proteinuria decreased from 11,2 (23–4.8) g/24 hours to 0.6 (0–2) g/24 hours after 6 months, and to 0.4 (0–1, 4) g/24 h in the 4 pts with the longer follow-up. Creatinine decreased from 1.95 (0.5–5) mg/dl to 0.88 (0.6–1.3) mg/l. Five patients achieved a complete renal remission, while in 1 pt proteinuria decreased by 75%. RTX successfully depleted CD19 lymphocytes in 100% of pts for at least 6 months. No clinically relevant adverse events have been observed. This case series shows a remarkable efficacy of RTX in treatment of MCD. RTX can be an attractive alternative both in recurrent forms and in induction-therapy of MCD. RTX may be preferentially used in patients at a high risk of development of the adverse effects of corticosteroids and should be considered as an alternative option in patients with recurrent NS. Additional data are needed to inform clinical practice on how best to use RTX in this patient population, so that definitive randomized trials can be planned.

Low-dose rituximab is poorly effective in patients with primary membranous nephropathy

Background

The optimal dosing and the efficacy of rituximab for primary membranous nephropathy (PMN) has not been established. This multicentric prospective study evaluates the efficacy and safety of low-dose rituximab (RTX) therapy in patients with PMN in clinical practice.

Methods

Thirty-four consecutive patients with PMN and nephrotic syndrome were included and received RTX (375 mg/m2) once (18 patients) or twice (16 patients). RTX was the first-line therapy for 19 (56%) and the second line for 15 (44%) patients. All patients were followed for 12 months after RTX and 24 for at least 18 months (mean 23.9 ± 18.6 months).

Results

At 12 months, 5 patients (14.7%) achieved complete response, 10 (29.4%) partial and 19 (55.8%) no response. Response occurred ∼6 months after RTX. At 24 months, the clinical situation was unchanged: two non-responders achieved partial response and two responders relapsed. Responders had significantly higher baseline GFR and lower anti-PLA2R antibodies compared with non-responders. Outcome was similar between one or two doses of RTX (non-responders 55.5 versus 56%, respectively) and between patients who had received previous therapy versus those receiving RTX as first-line therapy (non-responders 40 versus 68%, respectively). In the 15 patients already treated, the response to RTX was comparable to that of previous therapies.

Conclusion

Low-dose RTX obtains remission in <50% of PMN patients. Probably, higher doses and longer treatments are needed to induce and maintain a response. The balance between the costs and benefits should guide the selection of the patient and the optimal dosage.

Membranous Nephropathy and Anti-Podocytes Antibodies: Implications for the Diagnostic Workup and Disease Management

The discovery of circulating antibodies specific for native podocyte antigens has transformed the diagnostic workup and greatly improved management of idiopathic membranous nephropathy (iMN). In addition, their identification has clearly characterized iMN as a largely autoimmune disorder. Anti-PLA2R1 antibodies are detected in approximately 70% to 80% and anti-THSD7A antibodies in only 2% of adult patients with iMN. The presence of anti-THSD7A antibodies is associated with increased risk of malignancy. The assessment of PLA2R1 and THSD7A antigen expression in glomerular immune deposits has a better sensitivity than measurement of the corresponding autoantibodies. Therefore, in the presence of circulating anti-podocytes autoantibodies and/or enhanced expression of PLA2R1 and THSD7A antigens MN should be considered as primary MN (pMN). Anti-PLA2R1 or anti-THSD7A autoantibodies have been proposed as biomarkers of autoimmune disease activity and their blood levels should be regularly monitored in pMN to evaluate disease activity and predict outcomes. We propose a revised clinical workup flow for patients with MN that recommends assessment of kidney biopsy for PLA2R1 and THSD7A antigen expression, screening for circulating anti-podocytes antibodies, and assessment for secondary causes, especially cancer, in patients with THSD7A antibodies. Persistence of anti-podocyte antibodies for 6 months or their increase in association with nephrotic proteinuria should lead to the introduction of immunosuppressive therapies. Recent data have reported the efficacy and safety of new specific therapies targeting B cells (anti-CD20 antibodies, inhibitors of proteasome) in pMN which should lead to an update of currently outdated treatment guidelines.

Membranous nephropathy: thinking through the therapeutic options

Idiopathic membranous nephropathy (IMN) remains the most common cause of the nephrotic syndrome in adults and one of the leading identifiable causes of end-stage kidney disease. Prior to considering the best approach to treatment, three important components need to be considered. First, the natural history of the typical membranous patient today; second, the importance of identifying the causative factors; and third, the integration of the current data on the known autoantibody/antigen systems involved in IMN into the diagnosis and management of the patient. Combining this with information on the known indicators associated with a poor prognosis plus new data on surrogate markers that provide important clues that the treatment plan is correct has provided us with a more secure platform for choosing the right treatment for each patient. This already provides a more rational and precise approach to the use of our current therapeutic options. Even today, we can slow disease progression and in the future new approaches and new therapies are likely to lead to prevention of progression or even reversal of the injury in IMN, thereby leading to improved quality of life of our patients.

Pre- and Posttransplant Refractory Idiopathic Membranous Glomerulonephritis: The Forgotten Potential Culprit

Idiopathic membranous nephropathy has been recently recognized as an autoimmune disease that may recur or develop de novo posttransplant, whereby specific auto- or alloantibodies are directed against recently recognized podocyte structures such as the phospholipase receptor PLAR2 and the thrombospondin receptor THSD7A. The observed inconsistencies in therapeutic responses with all presently recognized therapies irrespective of immunosuppressive regimen used and the superiority of complete and sustained remission rates in recurrent disease after kidney transplant compared with native disease imply the existence of different immunopathogenic signatures that may be operational, either isolated or combined, in the pathogenesis of membranous nephropathy. These pathogenic mechanisms involve primarily B-cell-mediated pathways with a T-cell help component and distinct auto- and alloantibody-secreting mechanisms involving different B cells. These pathways are present in separate compartments such as in CD20+-activated B cells found in spleen and lymph nodes, CD19+/CD20- plasmablasts and short-lived plasma cells in the blood, and CD19-/CD20-/CD38+/CD138+ long-lived memory plasma cells niched naturally in the bone marrow and ectopically in the native or grafted inflamed kidney. These latter nonproliferating plasma cells lacking CD19 and CD20 markers would be resistant to in vivo B-cell depletion by anti-CD20 monoclonal therapies. They produce considerable amounts of immunoglobulin G (IgG) autoantibodies and alloantibodies and provide the basis for humoral memory and refractory autoimmune diseases. This may explain the limited rate of sustained complete remission, which, as observed in most studies, does not exceed a rate of 20% in all rituximab-treated patients despite total B-cell eradication. There is an important need for the development of new biomarkers to help identify and predict therapeutic responses. Potential new therapeutic targets against plasma cells such as proteasome inhibitors, anti-CD38 monoclonal antibodies, and autoreactive pathogenic B-cell-specific depleting regimens, as well as new anti-CD20 monoclonal antibodies, may help tailor therapy to the individual need for optimal outcome.

Treatment of membranous nephropathy: time for a paradigm shift

In patients with membranous nephropathy, alkylating agents (cyclophosphamide or chlorambucil) alone or in combination with steroids achieve remission of nephrotic syndrome more effectively than conservative treatment or steroids alone, but can cause myelotoxicity, infections, and cancer. Calcineurin inhibitors can improve proteinuria, but are nephrotoxic. Most patients relapse after treatment withdrawal and can become treatment dependent, which increases the risk of nephrotoxicity. The discovery of nephritogenic autoantibodies against podocyte M-type phospholipase A2 receptor (PLA₂R) and thrombospondin type-1 domain- containing protein 7A (THSD7A) antigens provides a clear pathophysiological rationale for interventions that specifically target B-cell lineages to prevent antibody production and subepithelial deposition. The anti-CD20 monoclonal antibody rituximab is safe and achieves remission of proteinuria in approximately two-thirds of patients with membranous nephropathy. In those with PLA₂R-related disease, remission can be predicted by anti-PLA₂R antibody depletion and relapse by antibody re-emergence into the circulation. Thus, integrated evaluation of serology and proteinuria could guide identification of affected patients and treatment with individually tailored protocols. Nonspecific and toxic immunosuppressive regimens will fall out of use. B-cell modulation by rituximab and second-generation anti-CD20 antibodies (or plasma cell-targeted therapy in anti-CD20 resistant forms of disease) will lead to a novel therapeutic paradigm for patients with membranous nephropathy.

Safety of Rituximab Compared with Steroids and Cyclophosphamide for Idiopathic Membranous Nephropathy

Guidelines recommend steroid plus cyclical cyclophosphamide (St-Cp) therapy for patients with idiopathic membranous nephropathy at high risk of progression to ESRD. Rituximab (Rtx) may be a safer alternative. In this retrospective, observational cohort study, we compared time to any adverse event (primary outcome); serious or nonserious events; partial and complete remission of the nephrotic syndrome; and a composite of doubling of serum creatinine, ESRD, or death between 100 Rtx-treated patients and 103 patients who received daily St-Cp We monitored patients with standardized protocols and adjusted for baseline characteristics by Cox regression. Over a median follow-up of 40 months, the Rtx group had significantly fewer adverse events than the St-Cp group (63 versus 173; P<0.001), both serious (11 versus 46; P<0.001) and nonserious (52 versus 127; P<0.001). Cumulative incidence of any first (35.5% versus 69.0%; P<0.001), serious (16.4% versus 30.2%; P=0.002), or nonserious (23.6% versus 60.8%; P<0.001) event was significantly lower with Rtx Adjusted hazard ratios (95% confidence intervals) between Rtx and St-Cp groups were 0.27 (0.16 to 0.44) for any first adverse event, 0.32 (0.15 to 0.68) for serious adverse events, and 0.23 (0.13 to 0.41) for nonserious adverse events. Although the cumulative incidence of partial remission was lower in the Rtx group, rates of complete remission and the composite renal end point did not differ significantly between groups. Because of its superior safety profile, we suggest that Rtx might replace St-Cp as first-line immunosuppressive therapy in patients with idiopathic membranous nephropathy and nephrotic syndrome.

Recent Treatment Advances and New Trials in Adult Nephrotic Syndrome

The etiology of nephrotic syndrome is complex and ranges from primary glomerulonephritis to secondary forms. Patients with nephrotic syndrome often need immunosuppressive treatment with its side effects and may progress to end stage renal disease. This review focuses on recent advances in the treatment of primary causes of nephrotic syndrome (idiopathic membranous nephropathy (iMN), minimal change disease (MCD), and focal segmental glomerulosclerosis (FSGS)) since the publication of the KDIGO guidelines in 2012. Current treatment recommendations are mostly based on randomized controlled trials (RCTs) in children, small RCTs, or case series in adults. Recently, only a few new RCTs have been published, such as the Gemritux trial evaluating rituximab treatment versus supportive antiproteinuric and antihypertensive therapy in iMN. Many RCTs are ongoing for iMN, MCD, and FSGS that will provide further information on the effectiveness of different treatment options for the causative disease. In addition to reviewing recent clinical studies, we provide insight into potential new targets for the treatment of nephrotic syndrome from recent basic science publications.

Glomerular Diseases and Renal Transplantation: Pathogenic Pathways and Evolution of Therapeutic Interventions

Glomerular diseases and renal transplantation are the main fields of nephrology in which the immune system plays a prevalent role. Glomerular diseases have traditionally been attributed to auto-immune conditions, whereas allograft rejection has been considered an allo-immune response. However, common immunopathologic mechanisms that include Toll-like receptors, complement and B-cell activation, as well as genetic and infectious factors appear to be involved in the pathogenesis of both entities. Novel therapeutic regimens directed against specific targets of the immune system show promising results in glomerulopathies as well as in renal transplantation.

Rituximab for immunologic renal disease: What the nephrologist needs to know

Rituximab (RTX), a chimeric, monoclonal anti-CD20 antibody, is increasingly used in immune-mediated renal diseases. While licensed in the induction treatment of ANCA-associated vasculitis, it represents one of the most commonly prescribed off-label drugs. Much of the information regarding its safety has been drawn from experience in hematology and rheumatology. Ample evidence illustrates the safety of RTX, however, rare but serious adverse events have emerged that include progressive multifocal leucoencephalopathy and hepatitis B reactivation. Moderate to severe hypogammaglobulinemia and late-onset neutropenia following RTX therapy confer an increased infectious risk and factors predicting these side effects (i.e. a genetic basis) need to be identified. Nephrologists initiating RTX need to bear in mind that long-term risks and optimal dosing for many renal indications remain unclear. Special considerations must be given when RTX is used in women of childbearing age. We summarize practical aspects concerning the use of RTX. This review will provide nephrologists with information to guide their use of RTX alerting them to safety risks and the need for patient counselling.

Membranous nephropathy: integrating basic science into improved clinical management

Idiopathic membranous nephropathy (INM) remains a common cause of the nephrotic syndrome in adults. The autoimmune nature of IMN was clearly delineated in 2009 with the identification of the glomerular-deposited IgG to be a podocyte receptor, phospholipase A2 receptor (PLA2R) in 70% to 75% of cases. This anti-PLA2R autoantibody, predominantly the IgG4 subclass, has been quantitated in serum using an enzyme-linked immunosorbent assay and has been used to aid diagnosis and monitor response to immunosuppressive therapy. In 2014, a second autoantigen, thrombospondin type 1 domain-containing 7A (THSD7A), was identified. Immunostaining of biopsy specimens has further detected either PLA2R or THSD7A antigen in the deposited immune complexes in 5% to 10% of cases autoantibody seronegative at the time of biopsy. Therefore, the term IMN should now be superseded by the term primary or autoimmune MN (AMN) (anti-PLA2R or anti-THSD7A positive) classifying ∼80% to 90% of cases previously designated IMN. Cases of secondary MN associated with other diseases show much lower association with these autoantibodies, but their true incidence in secondary cases still needs to be defined. How knowledge of the autoimmune mechanism and the sequential measurement of these autoantibodies is likely to change the clinical management and trajectory of AMN by more precisely defining its diagnosis, prognosis, and treatment is discussed. Their application early in the disease course to new and old therapies will provide additional precision to AMN management. We also review innovative therapeutic approaches on the horizon that are expected to lead to our ultimate goal of improved patient care in A(I)MN.

Single-dose Rituximab Therapy for Refractory Idiopathic Membranous Nephropathy: A Single-center Experience

To date, a recognized treatment for refractory membranous nephropathy (MN) has not been established. Recently, several reports have indicated the efficacy of rituximab as a novel treatment option. However, only a few published accounts exist of rituximab therapy for idiopathic MN (IMN) in the Asian population. We present the cases of three IMN patients who were treated with single-dose rituximab after they showed no response to conventional therapies, including corticosteroids, cyclosporine, cyclophosphamide, mizoribine, and mycophenolate mofetil. Although one case showed no response, a complete or incomplete remission was achieved in the other two cases. Rituximab may therefore be a beneficial treatment option for IMN.

Treatment with rituximab in idiopathic membranous nephropathy

BACKGROUND

Rituximab represents a valid therapeutic option to induce remission in patients with primary glomerulonephritis. Despite several studies proving its efficacy in improving outcomes in patients with membranous nephropathy (MN), its role in therapeutic protocols is not yet defined.

METHODS

We studied 38 patients with idiopathic MN treated with rituximab (in 13 patients as first-line therapy, in the remaining 25 after conventional immunosuppressive therapy). The patients were analyzed for a 15-month median (interquartile range 7.7-30.2) follow-up, with serial monitoring of 24-h proteinuria, renal function and circulating CD19⁺ B cells.

RESULTS

The percentages of patients who achieved complete remission, partial remission and the composite endpoint (complete or partial remission) were 39.5% (15 patients), 36.8% (14 patients) and 76.3% (29 patients), respectively. The 24-h proteinuria was reduced significantly during the entire period of follow-up (from a baseline value of 6.1 to 0.9 g/day in the last visit; P < 0.01), while albuminemia increased constantly (from a baseline value of 2.6 to 3.5 g/dL in the last observation; P < 0.01). Renal function did not significantly change during the observation period. Circulating CD19⁺ B cells were reduced significantly from the baseline value to the 24-month value (P < 0.01); data about anti-phospholipase A₂ receptor antibodies were available in 14 patients, 10 of which experienced a decreasing trend after treatment. No significant adverse events were described during and after infusions.

CONCLUSIONS

The present study confirmed that treatment with rituximab was remarkably safe and allowed for a large percentage of complete or partial remissions in patients with MN.

Rituximab use in adult primary glomerulopathy: where is the evidence?

Rituximab is a chimeric anti-CD20 antibody that results in depletion of B-cell lymphocytes. It is currently used in the treatment of a variety of autoimmune diseases, in addition to CD20-positive lymphomas. The use of rituximab in the treatment of the adult primary glomerular diseases has emerged recently, although not yet established as first-line therapy in international guidelines. In patients with steroid-dependent minimal change disease or frequently relapsing disease, and in patients with idiopathic membranous nephropathy (IMN), several retrospective and prospective studies support the use of rituximab to induce remission, whereas in idiopathic focal and segmental glomerulosclerosis (FSGS), the use of rituximab has resulted in variable results. Evidence is still lacking for the use of rituximab in patients with immunoglobulin A nephropathy (IgAN) and idiopathic membranoproliferative glomerulonephritis (MPGN), as only few reports used rituximab in these two entities. Randomized controlled trials (RCTs) are warranted and clearly needed to establish the definitive role of rituximab in the management of steroid-dependent and frequently relapsing minimal change disease, IMN, both as first-line and second-line treatment, and in MPGN. We await the results of an ongoing RCT of rituximab use in IgAN. Although current evidence for the use of rituximab in patients with idiopathic FSGS is poor, more RCTs are needed to clarify its role, if any, in the management of steroid-resistant or steroid-dependent FSGS.

Biologics for the treatment of autoimmune renal diseases

Biological therapeutics (biologics) that target autoimmune responses and inflammatory injury pathways have a marked beneficial impact on the management of many chronic diseases, including rheumatoid arthritis, psoriasis, inflammatory bowel disease, and ankylosing spondylitis. Accumulating data suggest that a growing number of renal diseases result from autoimmune injury - including lupus nephritis, IgA nephropathy, anti-neutrophil cytoplasmic antibody-associated glomerulonephritis, autoimmune (formerly idiopathic) membranous nephropathy, anti-glomerular basement membrane glomerulonephritis, and C3 nephropathy - and one can speculate that biologics might also be applicable to these diseases. As many autoimmune renal diseases are relatively uncommon, with long natural histories and diverse outcomes, clinical trials that aim to validate potentially useful biologics are difficult to design and/or perform. Some excellent consortia are undertaking cohort studies and clinical trials, but more multicentre international collaborations are needed to advance the introduction of new biologics to patients with autoimmune renal disorders. This Review discusses the key molecules that direct injurious inflammation and the biologics that are available to modulate them. The opportunities and challenges for the introduction of relevant biologics into treatment protocols for autoimmune renal diseases are also discussed.

Hurdles to the introduction of new therapies for immune-mediated kidney diseases

Innovative immunotherapies continue to markedly benefit many disciplines in clinical medicine but disappointingly, these benefits have not translated to the treatment of kidney diseases despite encouraging findings from preclinical models of kidney dysfunction. This lack of progress in nephrology might relate to the unique biology of the kidney. More likely, this lack of progress relates to conceptual hurdles in the application of newer therapies to renal disease. In this Review we discuss seven hurdles that must be addressed in order to appropriately assess and introduce immunologic therapies for immune-mediated kidney disease: the use of appropriate criteria to define disease categories; issues relating to the heterogeneity of kidney diseases and how this heterogeneity affects approaches to treatment; issues related to the rarity of most kidney diseases; the paucity of good animal models of human kidney disease; issues relating to trial design; problems with current approaches to the identification and use of appropriate and feasible study end points; and a lack of adequate biomarkers of intrarenal inflammation and parenchymal injury. We suggest that overcoming these hurdles, in addition to searching for better therapeutic targets, will be necessary to progress the treatment of immune-mediated kidney disease into a new age of drug therapy.

B Cells, Antibodies, and More

B cells play a central role in the immunopathogenesis of glomerulonephritides and transplant rejection. B cells secrete antibodies that contribute to tissue injury via multiple mechanisms. In addition, B cells contribute to disease pathogenesis in autoimmunity and alloimmunity by presenting antigens as well as providing costimulation and cytokines to T cells. B cells also play an immunomodulatory role in regulating the immune response by secreting cytokines that inhibit disease onset and/or progression. B cell-targeted approaches for treating immune diseases of the kidney and other organs have gained significant momentum. However, much remains to be understood about B-cell biology in order to determine the timing, duration, and context of optimal therapeutic response to B cell-targeted approaches. In this review, we discuss the multifaceted roles of B cells as enhancers and regulators of immunity with relevance to kidney disease and transplantation.