Effects of rituximab on morphofunctional abnormalities of membranous glomerulopathy

Ofatumumab in Rituximab-Resistant and Rituximab-Intolerant Patients With Primary Membranous Nephropathy: A Case Series

RATIONALE & OBJECTIVE

Rituximab is the first-choice therapy for patients with primary membranous nephropathy (MN) and nephrotic syndrome. However, approximately 30% of patients are treatment-resistant or become treatment-intolerant with hypersensitivity reactions upon repeated drug exposures. We aimed to assess whether ofatumumab, a fully human second-generation anti-CD20 antibody, could be a valuable alternative to rituximab in this population.

STUDY DESIGN

Case series.

SETTING & PARTICIPANTS

7 rituximab-intolerant and 10 rituximab-resistant patients with MN who consented to receive ofatumumab (50-300mg, single intravenous infusion) and were followed at the nephrology unit of Azienda Socio-Sanitaria Territoriale Papa Giovanni XXIII (Bergamo, Italy) between September 2015 and January 2019.

FINDINGS

Over a median (IQR) follow-up of 5.0 (3.0-9.8) months, all 7 rituximab-intolerant and 3 of the 10 rituximab-resistant patients exhibited complete (proteinuria<0.3g/d) or partial (proteinuria<3.5g/d with≥50% reduction vs baseline) remission of nephrotic syndrome. Circulating B cells were similarly depleted in all patients by 1 week, and serum anti-phospholipase A2 receptor antibody concentrations decreased to<2.7 relative units/mL in 3 of 4 rituximab-intolerant and 4 of 8 rituximab-resistant patients with phospholipase A2 receptor-related disease. Ofatumumab significantly reduced 24-hour urinary protein and immunoglobulin G excretion and increased serum albumin and immunoglobulin G levels. These effects were greater in rituximab-intolerant than in rituximab-resistant patients. Measured glomerular filtration rate significantly increased by an average of 13.4% at 24 months compared with baseline (P=0.036) among all patients in the series. There were 14 nonserious infusion-related adverse events in 9 patients that recovered with temporary infusion interruption.

LIMITATIONS

Retrospective design, limited number of patients.

CONCLUSIONS

Ofatumumab may represent an effective and safe treatment for rituximab-intolerant cases of MN. Larger prospective studies will be needed to validate these preliminary findings and explore the effectiveness of other second-generation anti-CD20 antibodies in this clinical setting.

PLAIN-LANGUAGE SUMMARY

Primary membranous nephropathy (MN) is one of the most frequent causes of nephrotic syndrome (NS) in adults. In this case series, we explored the efficacy of ofatumumab, a fully human second-generation anti-CD20 antibody, in 17 patients with MN and NS who were intolerant or unresponsive to rituximab. All 7 rituximab-intolerant patients exhibited complete or partial clinical remission, compared with only 3 of the 10 rituximab-resistant patients. Autoantibody levels decreased in all patients with phospholipase A2 receptor-related disease. Ofatumumab achieved a significant reduction in urinary protein and immunoglobulin G excretion while increasing serum albumin and immunoglobulin G levels. Ofatumumab may be a promising option for patients with MN who are rituximab-intolerant. Further investigations are warranted to validate these preliminary findings.

Sexual dimorphic response to rituximab treatment: A longitudinal observational study in a large cohort of patients with primary membranous nephropathy and persistent nephrotic syndrome

Rituximab is one of the first-line therapies for patients with membranous nephropathy (MN) at high risk of progression towards kidney failure. We investigated whether the response to Rituximab was affected by sex and anti-PLA₂R antibody levels in 204 consecutive patients (148 males and 56 females) with biopsy-proven MN who were referred to the Nephrology Unit of the Azienda Socio Sanitaria Territoriale Papa Giovanni XXIII from March 2001 to October 2016 and managed conservatively for at least 6 months. The primary outcome was a combined endpoint of complete (proteinuria <0.3 g/24 h) or partial (proteinuria <3.0 g/24 h and >50% reduction vs. baseline) remission. Patients gave written informed consent to Rituximab treatment. The study was internally funded. No pharmaceutical company was involved. Anti-PLA₂R antibodies were detectable in 125 patients (61.3%). At multivariable analyses, female gender (p = 0.0198) and lower serum creatinine levels (p = 0.0108) emerged as independent predictors of better outcome (p = 0.0198). The predictive value of proteinuria (p = 0.054) and anti-PLA₂R titer (p = 0.0766) was borderline significant. Over a median (IQR) of 24.8 (12.0–36.0) months, 40 females (71.4%) progressed to the combined endpoint compared with 73 males (49.3%). Anti-PLA₂R titers at baseline [127.6 (35.7-310.8) vs. 110.1 (39.9–226.7) RU/ml] and after Rituximab treatment were similar between the sexes. However, the event rate was significantly higher in females than in males [HR (95%): 2.12 (1.44–3.12), p = 0.0001]. Forty-five of the 62 patients (72.3%) with anti-PLA₂R titer below the median progressed to the combined endpoint versus 35 of the 63 (55.6%) with higher titer [HR (95%): 1.97 (1.26–3.07), p < 0.0029]. The highest probability of progressing to the combined endpoint was observed in females with anti-PLA₂R antibody titer below the median (86.7%), followed by females with anti-PLA₂R antibody titer above the median (83.3%), males with titer below the median (68.1%), and males with titer above the median (44.4%). This trend was statistically significant (p = 0.0023). Similar findings were observed for complete remission (proteinuria <0.3 g/24 h) and after analysis adjustments for baseline serum creatinine. Thus, despite similar immunological features, females were more resilient to renal injury following Rituximab therapy. These findings will hopefully open new avenues to identify the molecular pathways underlying sex-related nephroprotective effects.

A conceptual framework linking immunology, pathology, and clinical features in primary membranous nephropathy

Primary membranous nephropathy is a leading cause of adult nephrotic syndrome. The field took a major step forward with the identification of phospholipase A2 receptor (PLA2R) as a target antigen in the majority of cases and with the ability to measure circulating autoantibodies to PLA2R. Since then, the existence of additional target antigens such as thrombospondin type-1 domain-containing 7A, exostosin 1 and 2, neural EGFL like 1, and semaphorin 3B has been demonstrated. The ability to detect and monitor levels of circulating autoantibodies has opened a new window onto the humoral aspect of primary membranous nephropathy. Clinicians now rely on clinical parameters such as proteinuria, as well as levels of circulating autoantibodies against PLA2R and the results of immunofluorescence staining for PLA2R within kidney biopsy tissue, to guide the management of this disease. The relationship between immunologic and clinical disease course is consistent, but not necessarily intuitive. In addition, kidney biopsy provides only a single snapshot of disease that needs to be interpreted in light of changing clinical and serological findings. A clear understanding of these dynamic parameters is essential for staging, treatment, and management of this disease. This review aims to shed light on current knowledge regarding the development and time course of changes in the serum levels of autoantibodies against PLA2R, proteinuria, and histological findings that underlie the pathophysiology of primary membranous nephropathy.

Rituximab in Membranous Nephropathy

Membranous nephropathy (MN) is the most common cause of primary nephrotic syndrome among adults. The identification of phospholipase A2 receptor (PLA2R) as target antigen in most patients changed the management of MN dramatically, and provided a rationale for B-cell depleting agents such as rituximab. The efficacy of rituximab in inducing remission has been investigated in several studies, including 3 randomized controlled trials, in which complete and partial remission of proteinuria was achieved in approximately two-thirds of treated patients. Due to its favorable safety profile, rituximab is now considered a first-line treatment option for MN, especially in patients at moderate and high risk of deterioration in kidney function. However, questions remain about how to best use rituximab, including the optimal dosing regimen, a potential need for maintenance therapy, and assessment of long-term safety and efficacy outcomes. In this review, we provide an overview of the current literature and discuss both strengths and limitations of "the new standard."

Pathophysiology, diagnosis, and treatment of membranous nephropathy

Nephrotic syndrome is in adult patients mainly due to membranous nephropathy (MN) characterized by thickening of the glomerular basement membrane (GBM) and immune complex formation between podocytes and the GBM. Autoantibodies directed against the M-type phospholipase A2 receptor (PLA2R) and thrombospondin 1 domain-containing 7 A (THSD7A) can be used as diagnostic biomarkers. THSD7A seems to be of direct pathogenic significance as is suggested by experimental models and plasmapheresis in humans. Recently, further antigens like NELL-1 (neural tissue encoding protein with EGF-like repeats-1), exostosin 1 and 2 have been discovered. Thus, MN should be classified into antibody positive and antibody negative MN. More specific immunosuppressive treatments directed against B-cells and antibody production like rituximab have been introduced in addition to already existing immunosuppressive protocols including steroids, chlorambucil, cyclophosphamide, and calcineurin inhibitors. Antibody removal using immunoadsorption or plasmapheresis leads to short-term reduction in proteinuria and might be indicated only in patients with very severe proteinuria and complications. Studies are needed to identify a more specific immunosuppression directed against the production and effects of autoantibodies in order to protect the kidneys from autoimmune mediated tissue damage and to identify patients who require an immunosuppressive treatment, as the remission rate is high in patients with MN.

Rituximab for the management of idiopathic membranous nephropathy: a meta-analysis

PURPOSE

The aim of this study was to evaluate the efficacy of rituximab therapy in the management of idiopathic membranous nephropathy (IMN).

METHODS

After literature search, data from eligible studies were used to perform random-effects meta-analyses to estimate remission rates and changes in proteinuria at the latest follow-up after rituximab therapy. The outcomes were used for metaregression to identify the factors affecting the efficacy of rituximab.

RESULTS

Twenty-one studies were included in the analysis (602 patients; age 50 years [95% CI 46.8, 53.3]; 30% females [95% CI 23, 31]). Follow-up duration was 20.3 months [95% CI 17.1, 23.5]. Remission rate (67% [95% CI 61, 73]) was higher in studies with below average baseline proteinuria (76% [95% CI 61, 88]) than in studies with above average baseline proteinuria (61% [95% CI 54, 68]). The complete and partial remission rates were 26% [95% CI 20, 33] and 37% [95% CI 31, 43], respectively. Rituximab therapy significantly reduced proteinuria (mean difference between final and baseline values: - 4.90 g/day [95% CI - 6.18, - 3.63]; p < 0.00001; % reduction: 62% [95% CI 57, 68]). The reduction in proteinuria was inversely associated with baseline serum albumin levels (p = 0.021) and the estimated glomerular filtration rate (p < 0.00001) and was positively associated with baseline proteinuria (p < 0.00001). The remission rate or decrease in proteinuria was not significantly related to the anti-PLA₂R antibody status or previous immunosuppressant therapy.

CONCLUSION

Rituximab therapy in IMN patients can provide approximately 67% remission rate. The reduction in proteinuria was greater in patients who had higher baseline proteinuria.

A Comprehensive Phenotypic and Functional Immune Analysis Unravels Circulating Anti-Phospholipase A2 Receptor Antibody Secreting Cells in Membranous Nephropathy Patients

Introduction

Primary membranous nephropathy (MN) is characterized by the presence of antipodocyte antibodies, but studies describing phenotypic and functional abnormalities in circulating lymphocytes are limited.

Methods

We analyzed 68 different B- and T-cell subsets using flow cytometry in 30 MN patients (before initiating immunosuppression) compared with 31 patients with non–immune-mediated chronic kidney disease (CKD) and 12 healthy individuals. We also measured 19 serum cytokines in MN patients and in healthy controls. Lastly, we quantified the ex vivo production of phospholipase A2 receptor (PLA2R)-specific IgG by plasmablasts (measuring antibodies in culture supernatants and by the newly developed FluoroSpot assay [AutoImmun Diagnostika, Strasberg, Germany]) and assessed the circulating antibody repertoire by phage immunoprecipitation sequencing (PhIP-Seq).

Results

After adjusting for multiple testing, plasma cells and regulatory B cells (B_REG) were significantly higher (P < 0.05) in MN patients compared with both control groups. The percentages of circulating plasma cells correlated with serum anti-PLA2R antibody levels (P = 0.042) and were associated with disease activity. Ex vivo–expanded PLA2R-specific IgG-producing plasmablasts generated from circulating PLA2R-specific memory B cells (mBCs) correlated with serum anti-PLA2R IgG antibodies (P < 0.001) in MN patients. Tumor necrosis factor-α (TNF-α) was the only significantly increased cytokine in MN patients (P < 0.05), whereas there was no significant difference across study groups in the autoantibody and antiviral antibody repertoire.

Conclusion

This extensive phenotypic and functional immune characterization shows that autoreactive plasma cells are present in the circulation of MN patients, providing a new therapeutic target and a candidate biomarker of disease activity.

The Usefulness of Phospholipase A2 Receptor and IgG4 Detection in Differentiation Primary Membranous Nephropathy From Secondary Membranous Nephropathy in Renal Biopsy

Membranous nephropathy (MGN) is the most common cause of the nephrotic syndrome in adults. Most cases of MGN are primary, but secondary MGN are frequently encountered. Determination of secondary MGN is crucial for initiation of appropriate treatment. The diagnostic performance of the phospholipase A2 receptor (PLA2R) and immunoglobulin G4 (IgG4) detection based on immunohistochemistry were evaluated using biopsy tissues of 59 primary and 56 secondary MGN cases for discrimination between primary MGN and secondary MGN. The PLA2R and IgG4 detection based on immunohistochemistry were dominantly positive in primary MGN cases. Sensitivity and specificity values for identification of primary MGN were 83% and 88% for PLA2R, and 76% and 86% for IgG4. Both PLA2R and IgG4 positivity showed a high specificity of 96.4% for identifying primary MGN. A meta-analysis was performed for analysis of the diagnostic accuracy of histologic PLA2R and IgG4 deposition for differentiation of primary from secondary MGN. The overall sensitivity, specificity, and area under curve of summary receiver operating characteristics were 76%, 86%, 0.93 for histologic PLA2R deposition, and 80%, 69%, 0.82 for histologic IgG4 deposition. PLA2R and IgG4 detection based on immunohistochemistry can be useful for differentiation of primary MGN from secondary MGN.

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.

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 in Membranous Nephropathy: Not All Studies Are Created Equal

Many prospective studies and a recent randomized controlled trial have shown that the B-cell-depleting monoclonal antibody, rituximab, safely promotes the remission of nephrotic syndrome in approximately 65% of patients with membranous nephropathy (MN). Mechanistic studies have indicated that rituximab-induced proteinuria reduction is associated with clearance of anti-podocyte antigens phospholipase 2 receptor autoantibodies and subepithelial immune complexes, the hallmarks of the disease. A recently published study reported results which, at first sight, looked less favorable and implied that, due to a publication bias against negative results, the efficacy of rituximab in MN might be overestimated. Since patients received only one or 2 rituximab administrations, the authors suggest that when rituximab is used, higher doses and longer treatments should be considered. In this study, we highlight limitations of the study and warn against an oversimplified interpretation of the data. Though information on the optimal dose of rituximab to use in MN is still limited, available data from studies with predefined rituximab administration protocols collectively support the concept of titrating rituximab to the number of circulating B-cells that are invariably depleted after the first or second administration. Additional doses may increase the risk of adverse effects and related costs without augmenting efficacy. Importantly, underpowered studies with inconclusive results should not be confused with negative studies formally proving a neutral effect of a treatment. Until data from ad hoc designed clinical trials are available, the B-cell-driven protocol should be the preferred regimen, since it is similarly effective, but safer and more cost effective than other protocols employing multiple rituximab administrations.

Functional Human Podocytes Generated in Organoids from Amniotic Fluid Stem Cells

Generating kidney organoids using human stem cells could offer promising prospects for research and therapeutic purposes. However, no cell-based strategy has generated nephrons displaying an intact three-dimensional epithelial filtering barrier. Here, we generated organoids using murine embryonic kidney cells, and documented that these tissues recapitulated the complex three-dimensional filtering structure of glomerular slits in vivo and accomplished selective glomerular filtration and tubular reabsorption. Exploiting this technology, we mixed human amniotic fluid stem cells with mouse embryonic kidney cells to establish three-dimensional chimeric organoids that engrafted in vivo and grew to form vascularized glomeruli and tubular structures. Human cells contributed to the formation of glomerular structures, differentiated into podocytes with slit diaphragms, and internalized exogenously infused BSA, thus attaining in vivo degrees of specialization and function unprecedented for donor stem cells. In conclusion, human amniotic fluid stem cell chimeric organoids may offer new paths for studying renal development and human podocyte disease, and for facilitating drug discovery and translational research.

Rituximab in primary membranous nephropathy: first-line therapy, why not?

The ideal treatment of patients with primary membranous nephropathy (MN) and persistent nephrotic syndrome (NS) is still a matter of debate. This is a major issue since these patients may progress to end-stage kidney disease (ESKD) in 5-10 years. Steroids, alkylating agents, and calcineurin inhibitors have been suggested to achieve NS remission and prevent ESKD in this population. Treatment benefits, however, are uncertain and are often offset by serious adverse events (SAEs). Evidence that B cells play a crucial role in the pathogenesis of the disease, both as precursors of autoantibody-producing cells and as antigen-presenting cells, provided the background for explorative studies testing the role of B cell-depletion therapy with the monoclonal antibody rituximab. This approach aimed at selectively inhibiting disease mechanisms without the devastating consequences of unspecific immunosuppression. Finding that rituximab safely ameliorated NS in 8 patients with primary MN fueled a series of observational studies that uniformly confirmed the safety/efficacy profile of rituximab in this context. Although head-to-head comparisons in randomized clinical trials are missing, comparative analyses between series of homogeneous patient cohorts clearly show at least similar efficacy of rituximab as compared to steroid plus alkylating agents. Moreover, data confirm the dramatically superior safety profile of rituximab that actually appears to be associated with a rate of SAEs even lower than that observed with conservative therapy. Rituximab is also effective in patients resistant to other treatments and its cost-effectiveness is further increased when treatment is titrated to circulating B cells. Recently identified pathogenic antibodies against the M type phospholipase A2 receptor will likely provide a novel tool to monitor disease activity and drive rituximab therapy, at least in a subset of patients. Newly developed anti-CD20 antibodies could represent a valuable option for those who fail rituximab therapy. Steroids, alkylating agents, and calcineurin inhibitors should likely be abandoned.

Fractional excretion of IgG in idiopathic membranous nephropathy with nephrotic syndrome: a predictive marker of risk and drug responsiveness

Background

Treatment of idiopathic membranous nephropathy with nephrotic syndrome is still controversial. There is currently little known about the clinical use of renal biomarkers which may explain contradictory results obtained from clinical trials. In order to assess whether IgG-uria can predict the outcome in membranous nephropathy, we examined the value of baseline EF-IgG in predicting remission and progression of nephrotic syndrome.

Methods

In a prospective cohort of 84 (34 female) idiopathic membranous nephropathy patients with nephrotic syndrome we validated the ability of the clinically available urine biomarker, IgG, to predict the risk of kidney disease progression and the beneficial effect of immunosuppression with steroids and cyclophosphamide. The fractional excretion of IgG (FE-IgG) and α1-microglobulin (FE-α1m), urine albumin/creatinine ratio, and eGFR were measured at the time of kidney biopsy. Primary outcome was progression to end stage kidney failure or kidney function (eGFR) decline ≥ 50% of baseline. Patients were followed up for 7.2 ± 4.1 years (range 1–16.8).

Results

High FE-IgG (≥0.02) predicted an increased risk of kidney failure (Hazard Ratio, (HR) 8.2, 95%CI 1.0–66.3, p = 0.048) and lower chance of remission (HR 0.18, 95%CI 0.09–0.38, p < 0.001). The ten-year cumulative risk of kidney failure was 51.7% for patients with high FE-IgG compared to only 6.2% for patients with low FE-IgG. During the study, only 24% of patients with high FE-IgG entered remission compared to 90% of patients with low FE-IgG. Combined treatment with steroids and cyclophosphamide decreased the progression rate (–40%) and increased the remission rate (+36%) only in patients with high FE-IgG.

Conclusion

In idiopathic membranous nephropathy patients with nephrotic syndrome, FE-IgG could be useful for predicting kidney disease progression, remission, and response to treatment.

B cell depletion: rituximab in glomerular disease and transplantation

B cells play a central role in the pathogenesis of many autoimmune diseases. Selective targeting can be achieved with the use of the monoclonal antibody rituximab. In addition to being a drug for non-Hodgkin's lymphoma, rituximab is also an FDA-approved treatment for refractory rheumatoid arthritis and, since recently, ANCA vasculitis. It has shown efficacy in many autoimmune diseases. This review will discuss current evidence and the rationale of the use of rituximab in glomerular diseases, including randomized controlled trials. The focus will be on the use of rituximab in idiopathic membranous nephropathy, systemic lupus erythematosus and ANCA-associated vasculitis. The emerging role of rituximab in renal transplantation, where it seems to be important for the desensitization protocols for highly sensitized patients as well as for the preconditioning of ABO-incompatible recipients and the treatment of antibody-mediated rejection, will also be addressed.

Contribution of renal and non-renal clearance on increased total clearance of adalimumab in glomerular disease

The contribution of renal and non-renal clearance toward targeted concentrations and/or effects of therapeutic proteins in nephrotic patients are unknown. This study dissected the contribution of clearance pathways to adalimumab elimination in patients with focal segmental glomerulosclerosis (FSGS). Urine was collected from seven patients treated with adalimumab. Renal clearance (ClR ) was measured and non-renal clearance (ClNR ) was calculated as the difference between total clearance and ClR . Differences in cumulative amount in urine, ClR, and ClNR between study weeks 1 and 16 and relationships between proteinuria (protein:creatinine ratio (Up/c)), and ClR and ClNR were evaluated. Up to 13% of the adalimumab dose was lost in urine. ClNR contributed more than ClR to enhanced total clearance. There was a nonlinear relationship between Up/c and ClR (R(2) 0.7059); an increase in ClR beginning at Up/c of 12 mg/mg [slope 1.755, (C.I. -7.825 to 11.34)]. There was a linear relationship between Up/c and ClNR (R(2) 0.5039); for every one unit increase in Up/c, ClNR would increase by 3.5 mL/hr (P = 0.01). Both ClR and ClNR contribute to enhanced total clearance of adalimumab in glomerular disease secondary to FSGS. Additional research is needed to identify mechanisms for the increased ClNR pathways.

Angiotensin II contributes to diabetic renal dysfunction in rodents and humans via Notch1/Snail pathway

In nondiabetic rat models of renal disease, angiotensin II (Ang II) perpetuates podocyte injury and promotes progression to end-stage kidney disease. Herein, we wanted to explore the role of Ang II in diabetic nephropathy by a translational approach spanning from in vitro to in vivo rat and human studies, and to dissect the intracellular pathways involved. In isolated perfused rat kidneys and in cultured human podocytes, Ang II down-regulated nephrin expression via Notch1 activation and nuclear translocation of Snail. Hairy enhancer of split-1 was a Notch1-downstream gene effector that activated Snail in cultured podocytes. In vitro changes of the Snail/nephrin axis were similar to those in renal biopsy specimens of Zucker diabetic fatty rats and patients with advanced diabetic nephropathy, and were normalized by pharmacological inhibition of the renin-angiotensin system. Collectively, the present studies provide evidence that Ang II plays a relevant role in perpetuating glomerular injury in experimental and human diabetic nephropathy via persistent activation of Notch1 and Snail signaling in podocytes, eventually resulting in down-regulation of nephrin expression, the integrity of which is crucial for the glomerular filtration barrier.

Depletion of B lymphocytes in idiopathic membranous glomerulopathy: results from patients with extended follow-up

Aims

To assess the long-term therapeutic benefit of temporary depletion of B lymphocytes in patients with idiopathic membranous glomerulopathy (MGN) and search for potential predictors of response.

Patients and Methods

The patients included had been diagnosed with biopsy-proven MGN in the absence of secondary causes. Estimated glomerular filtration rate should be above 30 ml/min/1.73 m² and 24-hour proteinuria 3 g/day or more. Patients who had been treated with cyclosporine or cytotoxic agents the year prior to study entry were excluded. Depletion of B cells was achieved with rituximab, which was administered intravenously for 4 consecutive weeks. Partial remission was defined as a >50% decrease in proteinuria with absolute proteinuria <3 g/day, while complete remission was defined as a >50% decrease in proteinuria and an absolute protein excretion <0.3 g/day.

Results

Twelve patients were studied (4 females/8 males) with a mean age of 51.3 years. No major adverse effects were observed. During a median follow-up time of 48 months, 11/12 (91.6%) patients achieved remission [7/12 (58.3%) complete remission and 4/12 (33.3%) partial remission], while 1 patient did not respond to therapy. Twelve months after therapy, 68.8% (p = 0.003) of cases had achieved partial and 28.4% complete remission. Measurements of lymphocyte subpopulations did not reveal any changes except for the B cell depletion. B cell infiltrates captured per mm³ of renal tissue in the diagnostic biopsy did not correlate with subsequent response.

Conclusion

Depletion of B cells in idiopathic MGN was well tolerated and resulted in significant and long-lasting response rates in a series of 12 patients.

Mechanisms and treatment of CKD

As CKD continues to increase worldwide, along with the demand for related life-saving therapies, the financial burden of CKD will place an increasing drain on health care systems. Experimental studies showed that glomerular capillary hypertension and impaired sieving function with consequent protein overload play a pathogenic role in the progression of CKD. Consistently, human studies show that proteinuria is an independent predictor of progression and that its reduction is renoprotective. At comparable BP control, inhibitors of the renin-angiotensin system (RAS), including angiotensin converting enzyme (ACE) inhibitors and angiotensin II receptor blockers (ARBs), more effectively than non-RAS inhibitor therapy reduce proteinuria, slow progression to ESRD, and even improve the kidney function achieving disease regression in some cases. In participants with diabetes, RAS inhibitors delay the onset of microalbuminuria and its progression to macroalbuminuria, and ACE inhibitors may reduce the excess cardiovascular mortality associated with diabetic renal disease. In addition to RAS inhibitors, however, multimodal approaches including lifestyle modifications and multidrug therapy will be required in most cases to optimize control of the several risk factors for CKD and related cardiovascular morbidity. Whether novel medications may help further improve the cost-effectiveness of renoprotective interventions is a matter of investigation.

Triggers, bullets and targets, puzzle of membranous nephropathy

Introduction

Idiopathic Membranous Nephropathy (MN) is a common cause of adult nephrotic syndrome. Recently, M-type phospholipase A2 receptor (PLA2-R) has been discovered as the main podocyte antigen in the pathogenesis of idiopathic MN.

Materials and Methods

In this mini review, the author searched English-language MEDLINE for the terms “membranous nephropathy”, “rituximab”, and “phospholipase A2 receptor” up to October 2011.

Results

In support of its earlier discovery, reports from China and Europe confirmed the major pathogenic role of non-complement fixing IgG4 antibody against PLA2-R in the pathogenesis of idiopathic MN. Antibodies against aldose reductase (AR) and manganese superoxide dismutase (SOD2 ), and sub-epithelial deposition of cationic bovine serum albumin (BSA) are also reported in rare occasions. It seems that Rituximab is a good therapeutic choice for those patients who need immunosuppressive therapy.

Conclusions

Great discoveries in the diagnosis and treatment of idiopathic MN have been performed but pathogenic mechanism and triggers for anti-PLA2-R production are still unknown.

Treatment of idiopathic membranous nephropathy

Exciting progress recently has been made in our understanding of idiopathic membranous nephropathy, as well as treatment of this disease. Here, we review important advances regarding the pathogenesis of membranous nephropathy. We will also review the current approach to treatment and its limitations and will highlight new therapies that are currently being explored for this disease including Rituximab, mycophenolate mofetil, and adrenocorticotropic hormone, with an emphasis on results of the most recent clinical trials.

Rituximab in idiopathic membranous nephropathy

Selective depletion of B cells with the mAb rituximab may benefit the autoimmune glomerular disease idiopathic membranous nephropathy (IMN). Here, we describe our experience treating 100 consecutive IMN patients with persistent nephrotic syndrome with rituximab. We defined complete remission as persistent proteinuria <0.3 g/24 h and partial remission as persistent proteinuria <3 g/24 h, each also having >50% reduction in proteinuria from baseline. During a median follow-up of 29 months after rituximab administration, 65 patients achieved complete or partial remission. The median time to remission was 7.1 months. All 24 patients who had at least 4 years of follow-up achieved complete or partial remission. Rates of remission were similar between patients with or without previous immunosuppressive treatment. Four patients died and four progressed to ESRD. Measured GFR increased by a mean 13.2 (SD 19.6) ml/min per 1.73 m(2) among those who achieved complete remission. Serum albumin significantly increased and albumin fractional clearance decreased among those achieving complete or partial remission. Proteinuria at baseline and the follow-up duration each independently predicted the decline of proteinuria. Furthermore, the magnitude of proteinuria reduction significantly correlated with slower GFR decline (P=0.0001). No treatment-related serious adverse events occurred. In summary, rituximab achieved disease remission and stabilized or improved renal function in a large cohort of high-risk patients with IMN.

Very early recurrence of anti-Phospholipase A2 receptor-positive membranous nephropathy after transplantation

Membranous nephropathy is a common cause of adult nephrotic syndrome, with recent evidence suggesting that 70% of idiopathic disease is associated with anti-Phospholipase A(2) receptor autoantibodies. We describe a 63-year-old man with membranous nephropathy who underwent a kidney transplant and developed recurrent membranous nephropathy with fine granular co-localization of Phospholipase A(2) receptor and IgG evident on transplant biopsy on day 6 and elevated circulating levels of serum anti-Phospholipase A(2) receptor autoantibody that declined over time in conjunction with improvement in the serum creatinine and urinary protein. This is a very early case of Phospholipase A(2) receptor-associated recurrent membranous nephropathy with circulating anti-Phospholipase A(2) receptor autoantibody, which supports the emerging evidence that idiopathic membranous nephropathy is an autoimmune disease.

Rituximab in immunologic glomerular diseases

Experimental data suggest that the B-cell antigen CD20 may play a significant role in the pathogenesis of many diseases including glomerular diseases. These and other findings underpin the central concept of B-cell-depleting therapies that target CD20 antigen as treatments for lupus nephritis, idiopathic membranous nephropathy, focal segmental glomerulosclerosis, cryglobulinemic glomerulonephritis, antibody mediated renal allograft rejection and recurrent glomerulonephritis in renal allograft. Use of rituximab as a B-cell depleting therapy has been associated with clinical improvement and has emerged as a possible adjunct or alternative treatment option in this field of nephrology.

Idiopathic membranous nephropathy: an autoimmune disease

For more than 50 years researchers have debated the evidence for an autoimmune basis of human idiopathic membranous nephritis (MN). Work published in the past 2 years has substantially strengthened the belief that MN is indeed an autoimmune disease of the kidney. Autoantibodies of the IgG4 subclass to at least three podocyte membrane proteins including phospholipase A(2)-receptor, aldose reductase, and manganese superoxide dismutase have been detected by immunoblotting in sera as well as in acid eluates prepared from renal biopsy tissue of patients with this disease, using either whole tissue or microdissected glomeruli from frozen sections. In each case the podocyte antigen has been shown to co-localize with the subepithelial glomerular immune deposits in renal tissue of the same patients. It is not certain if any of these podocyte proteins is an inciting/primary autoantigen or whether they are secondary antigens recruited by intermolecular epitope-spreading, initiating from a yet-to-be-discovered autoantigen. Although it is clear that autoantibodies to podocyte membrane proteins are elicited in idiopathic MN and contribute to the formation of the subepithelial deposits, many questions remain concerning the triggers for their development and their contribution toward proteinuria and progression of the disease.

Rat Ace allele variation determines susceptibility to AngII-induced renal damage

INTRODUCTION

Ace b/l polymorphism in rats is associated with differential tissue angiotensin-converting enzyme (ACE) expression and activity, and susceptibility to renal damage. Same polymorphism was recently found in outbred Wistar rat strain with b allele accounting for higher renal ACE, and provided a model for studying renin-angiotensin-aldosterone system (RAAS) response behind the innate high or low ACE conditions.

METHODS

We investigated the reaction of these alleles on chronic angiotensin II (AngII) infusion. Wistar rats were selected to breed male homozygotes for the b (WU-B) or l allele (WU-L) (n = 12). For each allele, one group (n = 6) received AngII infusion via an osmotic minipump (435 ng/kg/min) for 3 weeks. The other group (n = 6) served as a control.

RESULTS

WU-B had higher ACE activity at baseline then WU-L. Interestingly, baseline renal ACE2 expression and activity were higher in WU-L. AngII infusion induced the same increase in blood pressure in both genotypes, no proteinuria, but caused tubulo-interstitial renal damage with increased α-SMA and monocyte/macrophage influx only in WU-B (p < 0.05). Low ACE WU-L rats did not develop renal damage.

CONCLUSION

AngII infusion causes proteinuria-independent renal damage only in rats with genetically predetermined high ACE while rats with low ACE seemed to be protected against the detrimental effect of AngII. Differences in renal ACE2, mirroring those in ACE, might be involved.

Rituximab-induced depletion of anti-PLA2R autoantibodies predicts response in membranous nephropathy

Autoantibodies to the M-type phospholipase A(2) receptor (PLA(2)R) are sensitive and specific for idiopathic membranous nephropathy. The anti-B cell agent rituximab is a promising therapy for this disease, but biomarkers of early response to treatment currently do not exist. Here, we investigated whether levels of anti-PLA(2)R correlate with the immunological activity of membranous nephropathy, potentially exhibiting a more rapid response to treatment than clinical parameters such as proteinuria. We measured the amount of anti-PLA(2)R using Western blot immunoassay in serial serum samples from a total of 35 patients treated with rituximab for membranous nephropathy in two distinct cohorts. Pretreatment samples from 25 of 35 (71%) patients contained anti-PLA(2)R, and these autoantibodies declined or disappeared in 17 (68%) of these patients within 12 months after rituximab. Those who demonstrated this immunologic response fared better clinically: 59% and 88% attained complete or partial remission by 12 and 24 months, respectively, compared with 0% and 33% among those with persistent anti-PLA(2)R levels. Changes in antibody levels preceded changes in proteinuria. One subject who relapsed during follow-up had a concomitant return of anti-PLA(2)R. In summary, measuring anti-PLA(2)R levels by immunoassay may be a method to follow and predict response to treatment with rituximab in membranous nephropathy.

Idiopathic membranous nephropathy and nephrotic syndrome: outcome in the era of evidence-based therapy

BACKGROUND

Contemporary studies analysing the long-term outcomes of patients with idiopathic membranous nephropathy and nephrotic syndrome in the era of evidence-based antiproteinuric and immunosuppressive therapies are sparse. Controversy also persists regarding which immunosuppression (IS) regimen to use. In this retrospective cohort study, we aimed to characterize time to partial remission (PR), complete remission (CR), requirement for renal replacement therapy (RRT) or death. We aimed to assess which factors predicted RRT or death and determine the impact of IS on outcome.

METHODS

Ninety-five consecutive adult patients attending two centres between 1997 and 2008 were identified. Baseline demographics and subsequent treatment and outcome were recorded.

RESULTS

Ninety-five percent of patients were prescribed angiotensin-converting enzyme inhibitors and/or angiotensin-receptor blocker (ACEI/ARB) therapy, 78% statin therapy, 70% antiplatelets and 38% IS. The 5-year actuarial rates for PR, CR, RRT and death were 76.4, 24.4, 11.9 and 16.8%, respectively. In patients achieving at least one PR, the 5-year actuarial risk of relapse was 32.8%. Using multivariate survival analysis, achievement of remission was the factor most strongly associated with reduced risk of RRT or death. There was no significant difference in outcomes between patients who did or did not receive IS, although patients receiving IS had more severe disease. Contrary to published findings, 81.8% of patients treated with the Ponticelli regimen (6 months of alternating prednisolone and cyclophosphamide or chlorambucil) suffered significant treatment-related complications compared with 19% of patients prescribed the Cattran regimen (prolonged combined low-dose prednisolone and cyclosporine).

CONCLUSIONS

Using an approach of widespread ACEI/ARB treatment and targeted IS, 76% of patients can expect to have achieved at least one PR by 5 years. Achievement of remission is the factor most strongly associated with reduced risk of RRT and death. Treatment with IS is associated with significant treatment complications.

Efficacy and safety of rituximab second-line therapy for membranous nephropathy: a prospective, matched-cohort study

BACKGROUND/AIMS

First-line immunosuppression with the B-cell depleting antibody rituximab reduced proteinuria and induced remission of the disease in patients with nephrotic syndrome (NS) secondary to idiopathic membranous nephropathy (IMN). Here we evaluated whether rituximab is equally effective in patients who failed to respond to previous immunosuppressive treatment.

METHODS

This academic, matched-cohort study, compared 2-year outcomes of 11 consecutive IMN patients who received second-line rituximab therapy for NS persisting or relapsing after previous treatment with steroids alone or combined with alkylating agents, cyclosporine, or immunoglobulin G, with those of 11 age- (± 5 years), gender- and proteinuria- (± 1 g/24h) matched reference patients given first-line rituximab therapy.

RESULTS

Patients' and reference patients' baseline characteristics were similar. Compared to baseline, 24-hour proteinuria similarly declined at 1 and 2 years post-rituximab (by 50.5 ± 25.1% and 60.9 ± 17.4% in patients and by 52.7 ± 31.5% and 69.4 ± 40.4% in reference patients, respectively; p < 0.01 for all comparisons vs. baseline). 8 patients and 7 reference patients achieved full (3 vs. 2) or partial (5 per cohort) proteinuria remission. Hypoalbuminemia and hyperlipidemia normalized in both groups. Self-limited infusion-related reactions occurred in 1 subject per cohort.

CONCLUSION

Rituximab reduced proteinuria in IMN patients with no or only transient response to unselective immunosuppression as effectively and safely as in patients without previous immunosuppression.

Beneficial effect of rituximab in the treatment of recurrent idiopathic membranous nephropathy after kidney transplantation

BACKGROUND AND OBJECTIVES

Recurrence of the original kidney disease after renal transplantation is an increasingly recognized cause of allograft loss. Idiopathic membranous nephropathy (iMN) is a common cause of proteinuria that may progress to ESRD. It is known that iMN may recur after kidney transplantation, causing proteinuria, allograft dysfunction, and allograft loss. Limited data regarding the frequency and treatment of recurrent iMN are available.

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

In this single-center study, all patients who had iMN and were receiving a first kidney transplant were included. We retrospectively assessed the incidence of biopsy-confirmed recurrent iMN and compared clinical characteristics of patients with and without recurrence. In addition, the effect of treatment with rituximab on proteinuria and renal allograft function in patients with recurrent iMN was examined

RESULTS

The incidence of recurrent iMN was 44%, and recurrences occurred at a median time of 13.6 months after transplantation. Two patterns of recurrence were identified: Early and late. No predictors of recurrence or disease progression could be identified. Treatment with rituximab was effective in four of four patients in stabilizing or reducing proteinuria and stabilizing renal function.

CONCLUSIONS

Recurrence of iMN is common even in the era of modern immunosuppression. Rituximab seems to be a valuable treatment option for these patients, although lager studies are needed to confirm our data.

Recurrent idiopathic membranous nephropathy: early diagnosis by protocol biopsies and treatment with anti-CD20 monoclonal antibodies

Membranous nephropathy (MN) recurs posttransplant in 42% of patients. We compared MN recurrence rates in a historical cohort transplanted between 1990 and 1999 and in a current cohort diagnosed by protocol biopsies, we analyzed the progression of the disease and we assessed the effects of anti-CD20 antibodies (Rituximab) on recurrent MN. The incidence of recurrent MN was similar in the historical (53%) and the current cohorts (41%), although in the later the diagnosis was made earlier (median, 4[2-21] months vs. 83[6-149], p = 0.002) and the disease was clinically milder. Twelve out of 14 patients (86%) with recurrent MN in the current cohort had progressive increases in proteinuria. Eight recipients were treated with Rituximab after their proteinuria increased from median, 211 mg/day (64-4898) at diagnosis to 4489 (898-13 855) (p = 0.038). Twelve months post-Rituximab, 75% of patients had either partial (PR) or complete remission (CR). After 24 months 6/7 (86%) had PR/CR and one patient relapsed. Posttreatment biopsies showed resorption of electron dense immune deposits in 6/7 cases and were negative for C3 (4/7) and IgG (3/7). Protocol biopsies allow early diagnosis of subclinical recurrent MN, which is often progressive. Treatment of recurrent MN with Rituximab is promising and should be evaluated in a prospective randomized controlled trial.

Idiopathic membranous nephropathy: management strategies

Treatment of idiopathic membranous nephropathy is based on a 'symptomatic' therapy that includes ACE inhibitors or angiotensin II receptor antagonists, and on an 'aetiological' therapy aimed at modulating underlying immunological mechanisms. The role of the latter is still debated given the usually indolent course of disease; furthermore, traditional immunosuppressants would not have an impact on patient and renal survival according to a systematic review of literature. However, up to 40% of untreated patients eventually develop end-stage renal disease and remission of nephrotic syndrome protects patients from related life-threatening complications and is the strongest positive prognostic factor for long-term kidney function. Therefore, immunosuppressive therapy seems to be rational in high-risk patients with nephrotic syndrome or deteriorating renal function. This article outlines a possible role for each 'aetiological' therapy on the basis of available evidence in order to provide some practical recommendations. The first-line therapy is based on a 6-month regimen of alternating corticosteroids and an alkylating agent ('Ponticelli' regimen), whereas oral ciclosporin and intramuscular corticotrophin (adrenocorticotrophic hormone) are alternatives that provide comparable results in terms of remission of proteinuria, with a different adverse effect profile. New drugs are emerging as potential treatments, such as mycophenolate mofetil, tacrolimus, intravenous immunoglobulins and rituximab. Specific settings, such as chronic renal failure or elderly age, require a careful balance between benefits and toxicity of immunosuppression. The tailor-made use of this repertoire of drugs can provide a tool to achieve remission of proteinuria and modify the natural course of idiopathic membranous nephropathy.

Early histological changes in the kidney of people with morbid obesity

BACKGROUND

Morbid obesity represents a major health problem with increasing incidence worldwide. The clinical manifestation of renal involvement in obesity is proteinuria, and the histological feature is glomerulomegaly with or without focal and segmental glomerulosclerosis (FSGS). In this study, we have investigated the very early histological changes in kidneys of people with morbid obesity and no proteinuria. Patients and methods. Eighteen patients with body mass index (BMI) >50 kg/m(2) who underwent a variant of biliopancreatic diversion with Roux-en-Y reconstruction (BPD-RYGBP) and consented to undergo a renal biopsy during the surgical procedure were included in the study. The estimation of early histological changes was performed on light (n = 18) and electron microscopy (n = 13).

RESULTS

The mean glomerular cross-sectional area was 30 943 +/- 10,984 microm(2) that is higher than that observed in non-obese individuals. In 21% of the examined glomeruli, the glomerular planar surface area (GPSA) was >40,000 microm(2). Thickening of the glomerular basement membrane (GBM) and scattered paramesangial deposits were identified in 9 of 13 patients (70%) whose renal tissue was examined by electron microscopy. A reduction in the slit pore frequency was observed in obese patients due to extensive foot process effacement. Significant positive correlations between mean GPSA and body weight (r = 0.462, P = 0.05), and between GBM thickness and HbA1c, serum total cholesterol and triglyceride levels (r = 0.60, P = 0.05; r = 0.789, P = 0.004; r = 0.70, P = 0.016, respectively), were observed.

CONCLUSIONS

Glomerulomegaly as well as histological lesions resembling those of early diabetic nephropathy are observed in kidney biopsies of patients with morbid obesity even before the appearance of microalbuminuria. The potential regression of these changes after weight loss needs to be clarified.

Controversies in the treatment of idiopathic membranous nephropathy

Optimum treatment of idiopathic membranous nephropathy is both controversial and challenging. The most extensively studied and frequently used immunosuppressive regimens for this disease comprise alkylating agents plus corticosteroids or ciclosporin. All of these treatment options have inherent problems: they are not effective in all patients, partial-rather than complete-remissions are common, adverse effects are worrisome, and relapses after treatment cessation remain problematic. Alternative immunosuppressive agents have been tested in an effort to overcome these unresolved issues. This paper reviews the available evidence regarding both established and new agents for the treatment of patients with idiopathic membranous nephropathy, with an emphasis on the results of the most recent clinical trials.

Rituximab therapy for membranous nephropathy: a systematic review

BACKGROUND AND OBJECTIVES

The treatment of membranous nephropathy (MN) remains controversial. Rituximab, which selectively targets B cells, has emerged as a possible alternative treatment option with limited toxicity.

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

The available data on rituximab therapy for MN were reviewed using the MEDLINE database (inception to August 1, 2008), Google Scholar, and selected reference lists. English-language studies investigating the use of rituximab in idiopathic and secondary MN, in native and transplanted kidneys, were included. Study design, subject number, clinical characteristics (diagnosis, previous and concomitant treatment courses, baseline proteinuria, baseline renal function), rituximab protocol, follow-up period, achievement of complete or partial remission, changes in proteinuria and renal function, and adverse effects of therapy were extracted.

RESULTS

Twenty-one articles were included for review; all were either case reports or case series without controls. More than half of the published cases (50 of 85) came from one center where rituximab was used as primary immunosuppression for idiopathic MN. The available data suggest that rituximab, dosed either as 375 mg/m(2) once weekly for 4 wk or as 1 g on days 1 and 15, achieves a 15 to 20% rate of complete remission and a 35 to 40% rate of partial remission. The drug was well tolerated with minimal adverse events.

CONCLUSIONS

Although rituximab may prove to be a better treatment option for MN than alkylating agents or calcineurin inhibitors, the current literature only supports using the drug in research protocols. Whether, when, how, and why to use rituximab in MN remains to be determined.