Rituximab in Patients With Phospholipase A2 Receptor-Associated Membranous Nephropathy and Severe CKD

An Updated Review of Membranous Nephropathy

Membranous nephropathy (MN) is one of the most common causes of nephrotic syndrome in adults. The discovery of phospholipase A2 receptor (PLA2R) as a target antigen has led to a paradigm shift in the understanding and management of MN. At present, serum PLA2R antibodies are used for diagnosis, prognostication, and guiding treatment. Now, with the discovery of more than 20 novel target antigens, antigen mapping is almost complete. The clinical association of certain antigens provides clues for clinicians, such as the association of nerve epidermal growth factor-like 1 with malignancies and indigenous medicines. Serum antibodies are detected for most target antigens, except exostosin 1 and 2 and transforming growth factor-beta receptor 3, but their clinical utility is yet to be defined. Genome-wide association studies and studies investigating environmental factors, such as air pollution, shed more light on the underpinnings of MN. The standard therapy of MN diversified from cyclical cyclophosphamide and steroids to include rituximab and calcineurin inhibitors over the past decades. Here, we provide a cutting-edge review of MN, focusing on genetics, immune system and environmental factors, novel target antigens and their clinical characteristics, and currently available and emerging novel therapies in MN.

Anti-CD20 should be the first-line treatment in high-risk membranous nephropathy

Membranous nephropathy (MN) is a common cause of nephrotic syndrome (NS) in adults and if untreated can progress to endstage kidney disease. Factors considered to place a patient at high or very high risk for progression include elevated serum creatinine at baseline, declining kidney function, persistent heavy proteinuria (>8 g/24 h), or persistent NS, presence of life-threatening complications related to NS (such as venous thromboembolic events), or very high anti-PLA2R antibody titers (>150 RU/ml). Patients who are at high or very high risk of progression should be treated with immunosuppression therapy to induce remission of proteinuria and to avoid progressive loss of kidney function. Traditional forms of immunosuppression for patients with MN have included the use of cyclic courses of corticosteroids with cyclophosphamide or calcineurin inhibitors. These forms of therapy are associated with significant toxicity, e.g. corticosteroids (infections, diabetes, weight gain), cyclophosphamide (infertility, severe leukopenia, malignancy), and calcineurin inhibitors (hypertension, nephrotoxicity). The introduction of anti-CD20+ B-cell therapies in the late 1990s has changed the landscape. In this article we will argue that anti-CD20+ B therapy should be the treatment of choice for patients at high/very high risk of progression when considering its efficacy and side-effect profile.

Update on the Application of Monoclonal Antibody Therapy in Primary Membranous Nephropathy

When first introduced, rituximab (RTX), a chimeric anti-CD20 monoclonal antibody, brought about an alternative therapeutic paradigm for primary membranous nephropathy (PMN). Rituximab was shown to be effective and safe in PMN patients with kidney dysfunction, with. patients receiving second-line rituximab therapy achieving remission as effectively as those patients who had not previously received immunotherapy. No safety issues were reported. The B cell-driven protocol seems to be as efficient as the 375 mg/m² × 4 regimen or 1 g × 2 regimen in achieving B cell depletion and remission, but patients with high M-type phospholipase A2 receptor (PLA2R) antibody levels may benefit from a higher dose of rituximab. While rituximab added another therapeutic option to the treatment regimen, it does have limitations as 20 to 40% of patients do not respond. Not all patients respond to RTX therapy for lymphoproliferative disorders either, therefore further novel anti-CD20 monoclonal antibodies have been developed and these may provide alternative therapeutic options for PMN. Ofatumumab, a fully human monoclonal antibody, specifically recognizes an epitope encompassing both the small and large extracellular loops of the CD20 molecule, resulting in increased complement-dependent cytotoxic activity. Ocrelizumab binds an alternative but overlapping epitope region to rituximab and displays enhanced antibody-dependent cellular cytotoxic (ADCC) activities. Obinutuzumab is designed to have a modified elbow-hinge amino acid sequence, leading to increased direct cell death induction and ADCC activities. In PMN clinical studies, ocrelizumab and obinutuzumab showed promising results, while ofatumumab displayed mixed results. However, there is a lack of randomized controlled trials with large samples, especially direct head-to-head comparisons. Alternative molecular mechanisms have been suggested in this context to explore novel therapeutic strategies. B cell activator-targeted, plasma cell-targeted and complement-directed treatments may lead to novel therapy paradigms for PMN. Exploratory strategies for the use of drugs with different mechanisms, such as a combination of rituximab and cyclophosphamide and a steroid, a combination of rituximab and a calcineurin inhibitor, may provide more rapid and efficient remission, but the combination of standard immunosuppression with rituximab could increase infection risk.

Novel Treatments Paradigms: Membranous Nephropathy

Primary membranous nephropathy (MN) is a kidney-specific autoimmune glomerular disease and the leading cause of nephrotic syndrome (NS) in White adults, usually caused by antiphospholipase A2 receptor (PLA2R) antibodies, although several new target antigens have been recently identified. It is characterized by the diffuse thickening of the glomerular basement membrane secondary to immune complex deposition. In patients with persistent NS without response to maximizing conservative therapy including the use of renin-angiotensin system (RAS) blockers, the use of immunosuppressive agents is warranted. However, the optimal immunosuppressive treatment has not yet been established. Classical immunosuppressants, such as cyclophosphamide plus steroids, are effective but may cause clinically relevant adverse effects, limiting their use. Rituximab offers efficacy with a better safety profile whereas calcineurin inhibitors (CNIs) are marred by high relapse rates and nephrotoxicity. Nevertheless, up to 30% of patients fail to respond to standard therapy. Novel and specific therapies targeting B cells and plasma cells have shown encouraging preliminary results, in terms of clinical efficacy and safety profile, especially in patients with poor tolerance or refractory to conventional treatments. In this brief review, we discuss the benefits and limitations of the current therapeutic approach to MN and describe emerging novel therapies that target its pathogenesis.

Primary membranous nephropathy: an endless story

Primary membranous nephropathy (PMN) is an autoimmune disease caused by the attack of autoantibodies against podocyte antigens leading to the in situ production of immune complexes. However, the etiology is unknown and the pathogenesis is still far from being completely elucidated. MN is prevalently idiopathic or primary, but in about 20-30% of cases it is secondary to chronic infections, systemic diseases, exposure to drugs, or malignancy. The differentiation between primary and secondary MN may be difficult, particularly when MN precedes signs and symptoms of the original disease, as in some cases of cancer or systemic lupus erythematosus. The natural course of PMN is variable, but in the long term 40-60% of patients with nephrotic syndrome progress to end-stage renal disease (ESRD) or die from thrombotic or cardiovascular events. PMN is a treatable disease. Patients with asymptomatic proteinuria should receive supportive care. Immunosuppressive treatments should be given to patients with nephrotic syndrome or risk of progression. The most frequently adopted treatments rely on cyclical therapy alternating steroids with a cytotoxic agent every other month, i.e., rituximab at different doses, or calcineurin inhibitors plus low-dose steroids. A good rate of response may be obtained but relapses can occur. Randomized controlled trials, with adequate size, long-term follow-up, and fair definition of endpoints are needed to identify treatment with the best therapeutic index.

Rituximab in patients with membranous nephropathy and kidney insufficiency

Introduction: Patients with membranous nephropathy and kidney insufficiency have an extremely high risk of progression to end-stage renal disease. Whether rituximab can effectively treat membranous nephropathy patients with renal dysfunction remains unknown at present. The aim of our study was to evaluate the effectiveness and safety of rituximab (RTX) in membranous nephropathy with kidney insufficiency.

Methods: We retrospectively analyzed the clinical data of 35 membranous nephropathy patients with kidney insufficiency administered in the First Affiliated Hospital of Zhengzhou University between January 2020 and December 2021. Patients were followed every 1–3 months for a total of 6 months. Clinical data were collected including anti-phospholipase A2 receptor antibody (anti-PLA2R antibody) quantification, 24-h urinary protein, serum albumin, and serum creatinine. The percentage of patients who achieved clinical remission was measured.

Results: There were 7 (20%) patients who achieved complete or partial response at 6 months after RTX treatment. After 6 months of treatment, patients were clinically improved as evidenced by significant improvements in anti- PLA2R antibody titer [7.70 (5.72, 16.72) vs. 59.20 (17.70, 187.50) RU/ml, p < 0.001], 24-h urine protein [7.04 (4.43, 8.90) vs. 10.15 (4.83, 13.57) g/d, p < 0.001], serum albumin [30.55 (24.97, 33.27) vs. 21.40 (16.75, 25.00)g/L, p < 0.001], serum creatinine [99.50 (75.25, 140.25) vs. 152.00 (134.50, 232.50) µmol/L, p = 0.022], and estimated glomerular filtration rate (eGFR) [78.29 (50.15, 101.55) vs. 41.12 (26.53, 51.41) ml/min/1.73 m², p = 0.045]. There were no significantly differences between responders and nonresponders in the baseline levels of anti-PLA2R antibodies, proteinuria, serum albumin, and renal function. After the RTX treatment, anti-PLA2R antibodies turned negative in all responders, but the antibody level persisted maintained positive in all but 5 nonresponders. The patients who achieved response maintained a stable kidney function during the study period, with eGFR 29.03 (28.76, 35.07) ml/min/1.73 m² before rituximab treatment and 62.73 (62.34, 63.13) ml/min/1.73 m² at the end of follow-up (p = 0.053).

Conclusion: RTX therapy might be an alternative treatment in reducing proteinuria and maintaining stable renal function among membranous nephropathy patients even with kidney insufficiency.

Treatment of rituximab in patients with idiopathic membranous nephropathy: a case series and literature review

BACKGROUND/AIMS

Membranous nephropathy (MN) is a major cause of nephrotic syndrome in adults. This study aimed to evaluate the effect of rituximab (RTX) in patients with idiopathic MN (iMN) who have a high risk of progression.

METHODS

We retrospectively analyzed data of 13 patients with iMN, who received RTX treatments from January 2014 to July 2020. RTX was indicated in patients with iMN with severe proteinuria and decreasing estimated glomerular filtration rate (eGFR) in the previous 6 months despite other immunosuppressive therapies.

RESULTS

The patients were predominantly males (n = 11) and with a mean age of 55.3 years; median eGFR, 37.0 mL/min/1.73 m2 (interquartile range [IQR], 26.3 to 66.5); serum albumin level, 2.6 g/dL (IQR, 1.9 to 3.1); and spot urine protein-to-creatinine ratio at baseline, 6.6 g/g (IQR, 5.7 to 12.9). In a median follow-up of 22 months, eight patients (61.5%) achieved complete or partial remission. In responder group (n = 8), median eGFR increased from 31.5 to 61.5 mL/min/1.73 m2 (p = 0.049) and serum albumin level increased from 2.3 to 4.2 g/dL (p = 0.017) from RTX initiation to last follow-up. Antiphospholipase A2 receptor antibody (anti-PLA2R-Ab) was positive in six among seven tested patients, which markedly decreased in the responder group. There were no adverse events after RTX.

CONCLUSION

This study suggests that RTX is a safe and effective treatment option for patients with iMN who have a high risk of progression. Individualized therapy based on anti-PLA2R-Ab titer would be needed for better outcomes.

Recent Advances in Clinical Diagnosis and Pharmacotherapy Options of Membranous Nephropathy

Membranous nephropathy (MN) is the most common cause of nephrotic syndrome among adults, which is the leading glomerular disease that recurs after kidney transplantation. Treatment for MN remained controversial and challenging, partly owing to absence of sensitive and specific biomarkers and effective therapy for prediction and diagnosis of disease activity. MN starts with the formation and deposition of circulating immune complexes on the outer area in the glomerular basement membrane, leading to complement activation. The identification of autoantibodies against the phospholipase A₂ receptor (PLA₂R) and thrombospondin type-1 domain-containing protein 7A (THSD7A) antigens illuminated a distinct pathophysiological rationale for MN treatments. Nowadays, detection of serum anti-PLA₂R antibodies and deposited glomerular PLA₂R antigen can be routinely applied to MN. Anti-PLA₂R antibodies exhibited much high specificity and sensitivity. Measurement of PLA₂R in immune complex deposition allows for the diagnosis of PLA₂R-associated MN in patients with renal biopsies. In the review, we critically summarized newer diagnosis biomarkers including PLA₂R and THSD7A tests and novel promising therapies by using traditional Chinese medicines such as Astragalus membranaceus, Tripterygium wilfordii, and Astragaloside IV for the treatment of MN patients. We also described unresolved questions and future challenges to reveal the diagnosis and treatments of MN. These unprecedented breakthroughs were quickly translated to clinical diagnosis and management. Considerable advances of detection methods played a critical role in diagnosis and monitoring of treatment.

Recent Clinical Trials Insights into the Treatment of Primary Membranous Nephropathy

Immunosuppressive therapy is mandatory for primary membranous nephropathy with persistent nephrotic proteinuria or anti-phospholipase A2 receptor antibodies, reduced kidney function, or another risk factor for progression. Rituximab has demonstrated efficacy for proteinuria remission compared with renin-angiotensin system blockade or cyclosporine in two well-powered randomized controlled trials. More recently, STARMEN showed that alternating glucocorticoid-cyclophosphamide is superior to sequential tacrolimus-rituximab for proteinuria remission, although it was associated with a higher risk of non-serious adverse events. However, sequential tacrolimus-rituximab involved delayed lower dose rituximab and was the worst-performing rituximab regimen among those tested in randomized clinical trials. The RI-CYCLO pilot study did not demonstrate superiority of glucocorticoid-cyclophosphamide over rituximab and found no difference in adverse events. Overall, STARMEN and RI-CYCLO confirmed the efficacy of glucocorticoid-cyclophosphamide in patients with high-risk membranous nephropathy and the role of rituximab as a valid alternative. However, none of the trials tested an optimized rituximab protocol involving a second rituximab cycle before declaring treatment failure. Calcineurin inhibitors should be considered third-line drugs and sequential use of calcineurin inhibitor rituximab did not add over rituximab-only regimens. We critically review recent randomized controlled trials, propose a research agenda, and call for multinational pragmatic trials that enroll patients at referral centers to address unmet research needs.

Immunosuppressive Therapy in Primary Membranous Nephropathy with Compromised Renal Function

INTRODUCTION

Renal dysfunction at presentation is uncommon in primary membranous nephropathy (PMN). The data on the outcome of PMN patients with renal dysfunction at outset are scarce. The objective of the current study was to report the clinical outcomes of PMN patients with renal dysfunction.

MATERIAL AND METHODS

This prospective longitudinal observational study included PMN patients (both incident and treatment resistant) with an estimated glomerular filtration rate of <60 mL/min/1.73 m2. Immunosuppressive treatment was as per the unit's protocol. Patients were evaluated for proteinuria, creatinine, and serum albumin at monthly intervals for 6 months, then quarterly for a year, and then biannually. Both serum and tissue anti-PLA2R were performed at baseline.

OUTCOME

Percentage of patients achieving clinical remission.

RESULTS

Sixty-four adults met study criteria and were analysed. The median (IQR) age of the patients was 48 (40, 56) years. PMN was PLA2R related in 52 (81.3%) patients. Twenty-eight (43.8%) and 30 (46.9%) patients were in remission at 12 months and at the end of the study [median (IQR) follow up: 24 months (12, 35)], respectively. Eight (12.5%) had progressed to end-stage renal disease at the last follow-up. Median (IQR) baseline anti-PLA2R titre was 150.1 RU/mL (38.5, 308). Nineteen (61.3%) and 18 (58.1%) patients with >90% reduction in anti-PLA2R titres at 12 months were in clinical remission at 12 months and at the end of the follow-up, respectively. Both cyclical cyclophosphamide/steroids (cCYC/GC) and rituximab were equally effective in inducing remission, but rituximab had a favourable adverse event profile compared to cCYC/GC.

CONCLUSION

To conclude, both cCYC/GC and rituximab are equally effective in inducing remission of nephrotic state with compromised renal function due to PMN. Immunosuppression induces remission in up to 50% PMN patients with CKD-stage 3-4.

Remissions in Patients with Idiopathic Membranous Nephropathy Treated with Rituximab in Senegal

Objectives: This study aimed to evaluate the efficacy of Rituximab in the management of idiopathic membranous nephropathy (IMN) based on the following criteria: (I) Biological remission at three months (M3) and six months (M6); (II) change in mean proteinuria (24PU), mean serum albumin, and mean serum creatinine at M3 and M6; (III) and side effects. Methods: This retrospective descriptive and analytical study included patients with histologically confirmed IMN with positive plasma anti-PLA2R antibodies who received at least one dose of Rituximab after six months of follow-up without spontaneous remission. Patients with unexplainable records were not included. Results: A total of five patients (P1, P2, P3, P4, and P5), including four males and one female were analyzed. The mean age was 44.20 ± 23.14 years. All patients had IMN type 2. At inclusion, the mean albuminemia, mean creatinine, and mean 24hPU levels were 15.56 ± 5.27 g/L, 17.3 ± 7.6 mg/L, and 6.54 ± 1.13 g/24h, respectively. The median anti-PLA2R antibody titer was 100 IU with extremes of 10 and 800 IU. Partial remission was noted in three patients at M3 (P2, P4, and P5), and it was maintained until M6 in P2. No complete remission was observed. A significant decrease in mean 24hPU at M3 was noted (P < 0.001). Generalized pruritus associated with seizures was noticed in P4 after the first dose of Rituximab. Conclusions: Partial remission was noted in three patients at M3, and one patient maintained this remission at M6. Rituximab significantly reduced 24hPU at M3 after administration. Rituximab administration was well tolerated by the patients.

Membranous nephropathy

Membranous nephropathy (MN) is a glomerular disease that can occur at all ages. In adults, it is the most frequent cause of nephrotic syndrome. In ~80% of patients, there is no underlying cause of MN (primary MN) and the remaining cases are associated with medications or other diseases such as systemic lupus erythematosus, hepatitis virus infection or malignancies. MN is an autoimmune disease characterized by a thickening of the glomerular capillary walls due to immune complex deposition. Identification of the phospholipase A2 receptor (PLA2R) as the major antigen in adults in 2009 induced a paradigm shift in disease diagnosis and monitoring and several other antigens have since been characterized. Disease outcome is difficult to predict and around one-third of patients will undergo spontaneous remission. In those at high risk of progression, immunosuppressive therapy with cyclophosphamide plus corticosteroids has substantially reduced the need for kidney replacement therapy. Owing to carcinogenic risk, other treatments (calcineurin inhibitors and CD20-targeted B cell depletion therapy (rituximab)) have been developed. However, disease relapses are frequent when calcineurin inhibitors are stopped and the remission rate with rituximab is lower than with cyclophosphamide, particularly in patients with high PLA2R antibody titres. Other new drugs are already available and antigen-specific immunotherapies are being developed.

Rapid, quantitative, and high-sensitivity detection of anti-phospholipase A2 receptor antibodies using a novel CdSe/ZnS-based fluorescence immunosorbent assay

Autoantibodies against M-type phospholipase A2 receptor (PLA2R) serve as specific biomarkers for idiopathic membranous nephropathy (IMN), and its quantification helps monitor disease activity. In this study, we describe a rapid and highly sensitive quantum dots-based immunochromatography assay (QD-ICA) for quantifying PLA2R autoantibodies. Serum samples from 135 biopsy-confirmed patients with nephrotic syndrome were analyzed for PLA2R autoantibodies using the novel QD-ICA as well as commercialized enzyme-linked immunosorbent assay (ELISA). Areas under the receiver operating characteristic curve (AUC-ROC) of QD-ICA were significantly greater than those of ELISA (91.1% [95% CI 85.9-96.3%] and 83.9% [95% CI 76.5-91.2%] respectively; p < 0.01). The detection sensitivity and specificity of QD-ICA (80.9% [95% CI 69.2-89.0%] and 100% [95% CI 93.2-100.0%], respectively) exceeded those of ELISA (72.1% [95% CI 59.7-81.9%] and 98.5% [95% CI 90.9-100.0%], respectively). The optimum cut-off value of QD-ICA was 18.18 relative units (RU)/mL, and the limit of detection was 2.86 RU/mL. The novel QD-ICA outperforms ELISA in detecting PLA2R autoantibodies, with shorter detection time, fewer steps, smaller equipment size, and broader testing application, suggesting its capability to improve IMN diagnosis and monitor patient response to treatment.

Primary membranous nephropathy in the era of autoantibodies and biological therapies

Primary membranous nephropathy is an autoimmune kidney disease and the most common cause of nephrotic syndrome in adults. About 70%-80% of cases are caused by anti-PLA2R antibodies. Its association with anti-THSD7A antibodies and other autoantibodies has also been described. Recent pilot studies and clinical trials have shown that several biological agents targeting autoantibody-producing cells are effective in controlling the disease with an acceptable safety profile. In this narrative review, we update key concepts about the pathogenesis, autoantibody-based diagnosis, and kidney biopsy findings in primary membranous nephropathy. In addition, we propose a diagnostic and therapeutic algorithm, including guidance on monitoring the response to therapy. We compare the efficacy and safety of currently available treatments, including rituximab and new biological agents, and identify unmet clinical needs.

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."

Advances in Membranous Nephropathy

Membranous nephropathy (MN) is a rare auto-immune disease where the glomerulus is targeted by circulating auto-antibodies mostly against podocyte antigens, which results in the formation of electron-dense immune complexes, activation of complement and massive proteinuria. MN is the most common cause of nephrotic syndrome in adults leading to severe thrombotic complications and kidney failure. This review is focused on the recent therapeutic and pathophysiological advances that occurred in the last two years. For a long time, we were lacking a head-to-head comparison between cyclophosphamide considered as the gold standard therapy and other medications, notably rituximab. Substantial progress has been achieved owing to three randomized controlled trials. MENTOR (Membranous Nephropathy Trial of Rituximab) and STARMEN (Sequential Therapy with Tacrolimus and Rituximab in Primary Membranous Nephropathy) conclusively established that calcineurin inhibitor-based regimens are slower to result in an immunologic response than rituximab or cyclophosphamide, achieve fewer complete clinical remissions, and are less likely to maintainremission. Rituximab Versus Steroids and Cyclophosphamide in the Treatment of Idiopathic Membranous Nephropathy (RI-CYCLO) suggested that competition between cyclophosphamide and rituximab remains open. Given the technological leap combining laser microdissection of glomeruli and mass spectrometry of solubilized digested proteins, four "new antigens" were discovered including NELL-1 and Semaphorin 3B in so-called primary MN, and exostosins 1 and 2 and NCAM 1 in lupus MN. NELL-1 is associated with about 8% of primary MN and is characterized by segmental immune deposits and frequent association with cancer (30%). Semaphorin 3B-associated MN usually occurs in children, often below the age of two years, where it is the main antigen, representing about 16% of non-lupus MN in childhood. Exostosins 1/2 and NCAM 1 are associated with 30% and 6% of lupus MN, respectively. Exostosins 1/2 (EXT1/2) staining is associated with a low rate of end-stage kidney disease (ESKD) even in mixed classes III/IV+V. These findings already lead to revisiting the diagnostic and therapeutic algorithms toward more personalized medicine.

Fumarate modulates phospholipase A2 receptor autoimmunity-induced podocyte injury in membranous nephropathy

Downstream mechanisms that lead to podocyte injury following phospholipase A2 receptor (PLA2R) autoimmunity remain elusive. To help define this we compared urinary metabolomic profiles of patients with PLA2R-associated membranous nephropathy (MN) at the time of kidney biopsy with those of patients with minimal change disease (MCD) and to healthy individuals. Among the metabolites differentially expressed in patients with PLA2R-associated MN compared to healthy individuals, fumarate was the only significant differentially expressed metabolite in PLA2R-associated MN compared to MCD [fold-difference vs. healthy controls and vs. MCD: 1.76 and 1.60, respectively]. High urinary fumarate levels could predict the composite outcome of PLA2R-associated MN. Fumarate hydratase, which hydrolyzes fumarate, colocalized with podocalyxin, and its expression was lower in glomerular sections from patients with PLA2R-associated MN than in those from healthy individuals, patients with non-PLA2R-associated MN or MCD. Podocytes stimulated with IgG purified from serum with a high anti-PLA2R titer (MN-IgG) decreased expression of fumarate hydratase and increased fumarate levels. These changes were coupled to alterations in the expression of molecules involved in the phenotypic profile of podocytes (WT1, ZO-1, Snail, and fibronectin), an increase in albumin flux across the podocyte layer and the production of reactive oxygen species in podocytes. However, overexpression of fumarate hydratase ameliorated these alterations. Furthermore, knockdown of fumarate hydratase exhibited synergistic effects with MN-IgG treatment. Thus, fumarate may promote changes in the phenotypic profiles of podocytes after the development of PLA2R autoimmunity. These findings suggest that fumarate could serve as a potential target for the treatment of PLA2R-associated MN.