Abstract
Background
The efficacy of rituximab (RTX) in primary membranous nephropathy (PMN) patients with high titers of anti-PLA2R antibodies (aPLA2R) is controversial. This study aimed to evaluate RTX efficacy in PMN patients with high versus low aPLA2R antibodies, and to compare RTX with traditional immunosuppressive regiments in patients with high aPLA2R antibodies.
Methods
We enrolled 118 PMN patients with positive serum aPLA2R antibodies. According to baseline aPLA2R antibody levels, patients treated with RTX were classified into low-titer (L-aPLA2R-RTX) and high-titer (H-aPLA2R-RTX) groups. Meanwhile, high aPLA2R antibody patients were divided into RTX (H-aPLA2R-RTX), tacrolimus (H-aPLA2R-TAC) and cyclophosphamide (H-aPLA2R-CTX) groups according to initial therapy. All patients were followed for 12 months. The primary outcome was complete or partial remission (CR or PR) at 12 months. Secondary outcomes included changes in laboratory parameters, relapse, and adverse events.
Results
At 12months, 36 patients (74%) in the L-aPLA2R-RTX group and 13 patients (46%) in the H-aPLA2R-RTX group achieved CR or PR (OR = 3.20, 95% CI:1.20–8.49). CR rates were 33% and 11% in the L-aPLA2R-RTX and H-aPLA2R-RTX groups (OR = 4.04, 95% CI:1.06–15.40). Regarding adverse events, there were 22% in the L-aPLA2R-RTX group and 46% in the H-aPLA2R-RTX group (p = 0.03). Relapse rates did not differ significantly between the two groups. At 12 months, CR rates were 11%, 25% and 62% in the H-aPLA2R-RTX, H-aPLA2R-CTX and H-aPLA2R-TAC groups, respectively (p = 0.001). No significant differences were observed among the three groups in terms of CR or PR rates at 12 months, relapse and adverse events.
Conclusion
PMN patients with high baseline aPLA2R antibody titers had lower remission rates with RTX compared to those with low titers. Among high-titer patients, TAC or CTX were associated with higher remission rates than RTX, particularly TAC.
Clinical trial number
Not applicable.
Supplementary Information
The online version contains supplementary material available at 10.1186/s12882-025-04692-1.
Keywords: Primary membranous nephropathy, Rituximab, Cyclophosphamide, Tacrolimus, Anti-PLA2R antibody
Introduction
Primary membranous nephropathy (PMN) is a primary glomerular disease mediated by autoantibodies, in which the M-type phospholipase A2 receptor (PLA2R) is recognized as the principal pathogenic target antigen [1, 2]. Although approximately one-third of PMN patients may experience spontaneous remission, initiation of immunosuppressive therapy is generally recommended for those with moderate or high-risk, including persistently high anti-PLA2R (aPLA2R) antibodies, massive proteinuria, or progressive renal dysfunction [3, 4]. Despite decades of progress in treatment strategies, a universally accepted optimal regimen has yet to be established.
Compared with conventional immunosuppressive regimens, rituximab (RTX) has gradually become one of the first-line therapeutic options for PMN due to good targeting and low toxicity [5, 6]. Despite the overall efficacy of RTX, some patients still fail to achieve clinical remission after RTX treatment, or experience relapse or even drug resistance [7, 8]. Several mechanisms contributing to treatment failure have been proposed. The production of anti-rituximab antibodies (ARAs) is recognized as a contributor to diminished RTX efficacy, and their formation is associated with high aPLA2R antibodies and may lead to faster B-cell reconstitution and an increased risk of relapse [8–11]. Similarly, RTX underdosing has been identified as another risk factor for suboptimal response, as insufficient RTX exposure may lead to incomplete B-cell depletion and treatment failure [8, 12]. These findings suggest that high aPLA2R antibody levels may influence the therapeutic response to RTX. It is noteworthy that there is a strong correlation between anti-PLA2R antibody levels and the risk of PMN progression associated with anti-PLA2R antibodies [13, 14]. However, a study by Teisseyre et al. [10] showed that the presence of ARAs had no significant effect on remission rates at 6 and 12 months in PMN patients who had received RTX treatment. Therefore, it is crucial to clarify the role of baseline aPLA2R antibody levels in the proteinuria remission in PMN patients receiving RTX treatment, which is an important guideline for the development of individualized initial treatment strategies.
This study examined the efficacy of RTX in inducing proteinuria remission in PMN at different baseline aPLA2R antibody titers and compared it with conventional immunosuppressive regimens in patients with high titers.
Methods
The study was conducted in accordance with the Declaration of Helsinki, with protocol approval obtained from the Ethics Committee of the Second Affiliated Hospital of Nanchang University. Written informed consent was obtained from all participants.
Study design and patients
This retrospective study included consecutively enrolled patients with nephropathy who attended the Department of Nephrology of the Second Affiliated Hospital of Nanchang University between January 2021 and February 2024. The inclusion criteria included (1) age > 18 years; (2) diagnosis of PMN confirmed by renal biopsy; (3) positive serum aPLA2R antibody (> 20 RU/mL by EUROIMMUN ELISA); (4) proteinuria > 3.5 g/d, serum albumin < 30 g/L, and estimated glomerular filtration rate (eGFR) ≥ 30 ml/min/1.73 m²prior to the initial immunosuppressive therapy; (5) receipt of a single immunosuppressive regimen (RTX, TAC, or CTX) and completion of at least 12 months of follow-up. Exclusion criteria: (1) Prior immunosuppressive therapy; (2) Pregnant or lactating women; (3) Other causes of MN, such as autoimmune diseases, hepatitis, HIV, and malignant tumors, etc.; (4) Presence of other serious conditions, such as severe cardiovascular disease or hepatic dysfunction.
All patients were classified into low-titer (20–200 RU/ml) and high-titer (>200 RU/ml) groups with reference to baseline aPLA2R antibody levels, according to Teisseyre et al. [10]. This study was conducted in two phases. In the first phase, all patients who received RTX treatment were further divided into a low-titer aPLA2R RTX (L-aPLA2R-RTX) group and a high-titer aPLA2R RTX (H-aPLA2R-RTX) group based on aPLA2R antibody levels. In the second phase, patients with high aPLA2R titers were selected and divided into the high-titer aPLA2R RTX (H-aPLA2R-RTX) group, the high-titer aPLA2R TAC (H-aPLA2R-TAC) group, and the high-titer aPLA2R CTX (H-aPLA2R-CTX) group, based on the regimen they received.
Clinical data
Patient demographic and clinical data were obtained from the electronic medical record, which included age, gender, blood pressure and laboratory parameters. Laboratory parameters included: serum aPLA2R antibody titers, serum albumin, serum creatinine, proteinuria, and eGFR. eGFR was calculated by the CKD-EPI formula [15]. Serum aPLA2R levels were measured by EUROIMMUN ELISA, with reference values: <14 RU/ml as negative, 14–20 RU/ml as threshold, and >20 RU/mL as positive [16].
Interventions
Patients in the RTX group received a standard dosage regimen consisting of 375 mg/m2 intravenously weekly for 4 doses or 1 g intravenously every 2 weeks for 2 doses, and the CTX group were treated with 0.5–1 g/m² (up to 1 g) of CTX intravenously every month for 6 months. The TAC group received an initial oral dose of 0.05–0.1 mg/kg/d, aiming for a target blood concentration of 5–7 ng/ml, which was individually adjusted and reduced as needed in cases of renal impairment. RTX was reintroduced for those who did not achieve significant resolution of proteinuria (i.e., proteinuria persisted at > 3.5 g/d or decreased by less than 50% from baseline) within 6 months of the initial reintroduction of the drug, or who experienced a relapse. For patients who achieve partial remission (PR), TAC should continue for 12 months. In patients achieving complete remission (CR), TAC may be tapered over 3 to 6 months whilst monitoring for relapse. Patients failing to achieve PR after at least 6 months of adequate therapy were classified as having initial treatment failure. During the administration of TAC or CTX, oral prednisone was initiated at 0.5 mg/kg/d for 1 month and thereafter tapered over 6 months until discontinued. All patients received standard supportive therapy. This included maximally tolerated renin-angiotensin-aldosterone system (RAAS) blockade agents, strict blood pressure control, and management of hyperlipidemia and edema. All enrolled patients were assessed for the risk of renal function loss according to the 2021 KDIGO guidelines and received appropriate pharmacological interventions on this basis.
Follow-up and outcomes
Follow-up events were recorded from the time of first immunosuppressive therapy to assess clinical indicators, remission, relapse, and drug-related adverse events at 3, 6, and 12 months, respectively.
The primary outcome was the composite of CR or PR at 12 months. Secondary outcomes included CR at 12 months; changes in proteinuria, serum creatinine, eGFR, and serum albumin at 12 months compared to baseline; relapse; and adverse events.
CR was defined as proteinuria below 0.3 g/d with serum albumin ≥ 35 g/l; PR referred to a ≥ 50% reduction in proteinuria from baseline, with a final level between 0.3 and 3.5 g/d. Relapse was defined as proteinuria rising above 3.5 g/d following a prior CR or PR. Adverse events included infections, drug infusion reactions or drug intolerance, and steroid diabetes to name a few.
Statistical analysis
Continuous variables were expressed as mean ± SD or median with interquartile range (IQR, 25%-75%), based on data distribution. Categorical data were expressed as counts and percentages. For comparisons between two groups, the independent-samples t-test or the Wilcoxon rank-sum test was applied as appropriate. Comparisons across three groups utilized one-way ANOVA or the Kruskal-Wallis test. The Pearson chi-square test or Fisher’s exact test was used for categorical variables, as appropriate. Kaplan-Meier analysis estimated cumulative remission rates, with intergroup differences evaluated via the log-rank test.
Subgroup analyses of the primary outcome were conducted according to baseline characteristics, including age, gender, proteinuria, serum creatinine, eGFR, serum albumin, and serum aPLA2R antibody levels. To assess differences in treatment effects among subgroups, a Cox proportional hazards model was employed, incorporating interaction terms to test for statistical heterogeneity. Interaction effects were presented as HRs with corresponding 95% CIs.
Statistical analyses were carried out using SPSS version 26.0 (IBM Corp., Armonk, NY, USA). Graphs were produced with GraphPad Prism 10.1.2 and R 4.4.3. Statistical significance was defined as a two-sided p-value<0.05.
Results
Baseline characteristics
A total of 118 patients with biopsy-proven PMN and positive serum aPLA2R antibodies were enrolled in this study, including 69 patients with high aPLA2R antibodies and 49 with low aPLA2R antibodies. In the first phase, 77 patients received RTX treatment, of which 49 were categorised in the L-aPLA2R-RTX group and 28 in the H-aPLA2R-RTX group (Fig. 1). The mean (SD) age of the patients included in first phase was 59 ± 2 years and 55 patients (71%) were male. The mean (SD) serum albumin was 23.9 ± 4.0 g/l. The median (IQR) proteinuria and aPLA2R antibody levels were 8.5 g/d (6.1–12.2) and 109.9 RU/ml (42.6–338.0). As shown in Table 1, compared with the L-aPLA2R-RTX group, patients in the H-aPLA2R-RTX group had significantly higher baseline aPLA2R antibody levels (p < 0.001). There were no significant differences between the two groups in terms of age, sex, proteinuria, serum albumin, serum creatinine, eGFR, or blood pressure, RTX dosing regimens.
Fig. 1.
Patient selection flowchart. PMN, primary membranous nephropathy; RTX, rituximab; TAC, tacrolimus; CTX, cyclophosphamide
Table 1.
Baseline characteristics of patients with different anti-PLA2R antibody titers in the rituximab group
| Characteristic | Total (N = 77) |
L-aPLA2R-RTX (N = 49) |
H-aPLA2R-RTX (N = 28) |
P Value |
|---|---|---|---|---|
| Age, yr | 59 ± 2 | 57 ± 14 | 63 ± 11 | 0.06 |
| Male sex, n (%) | 55 (71) | 37 (76) | 18 (64) | 0.29 |
| Blood pressure, mmHg | ||||
| Systolic | 128.2 ± 2.1 | 129.7 ± 18.5 | 125.6 ± 17.4 | 0.34 |
| Diastolic | 78.0 ± 1.2 | 79.3 ± 10.1 | 75.8 ± 11.4 | 0.17 |
| Serum albumin, g/L | 23.9 ± 4.0 | 24.5 ± 3.9 | 22.9 ± 4.1 | 0.11 |
| Serum creatinine, umol/L | 0.12 | |||
| Median | 91.4 | 94.9 | 87.5 | |
| Interquartile range | 76.1–109.0 | 78.1-121.2 | 73.8–96.8 | |
| Proteinuria, g/d | 0.20 | |||
| Median | 8.5 | 8.0 | 9.5 | |
| Interquartile range | 6.1–12.2 | 5.9–12.0 | 6.9–14.2 | |
| Anti-PLA2R levels, RU/ml | <0.001 | |||
| Median | 109.9 | 67.1 | 421.4 | |
| Interquartile range | 42.6–338.0 | 26.5-106.8 | 320.8-659.2 | |
| eGFR, ml/min/1.73 m² | 79 ± 30 | 76 ± 35 | 84 ± 21 | 0.27 |
| RTX Treatment Regimensa, n (%) | 52 (67.5) | 34 (69.4) | 18 (64.3) | 0.801 |
yr, year; eGFR, estimated glomerular filtration rate; a, RTX 1000 mg x 2 doses. L-aPLA2R-RTX, Patients with low anti-PLA2R antibody titers treated with rituximab; H-aPLA2R-RTX, Patients with high anti-PLA2R antibody titers treated with rituximab; Values are presented as mean ± SD, n (%), or median (interquartile range); P < 0.05 was statistical difference
In the second phase, 69 patients with high aPLA2R antibodies were included, of whom 28 received RTX, 21 received TAC, and 20 received CTX (Fig. 1). The mean (SD) age of the patients included was 61 ± 11 years, with 48 male patients (70%). The mean (SD) serum albumin was 22.8 ± 5.1 g/l. The median (IQR) proteinuria and aPLA2R antibody levels were 9.5 g/d (6.6–13.9) and 397.7 RU/ml (289.4-648.1). Table 2 shows that baseline characteristics did not differ significantly among the three groups.
Table 2.
Baseline characteristics of patients with high anti-PLA2R antibody titers according to treatment group
| Characteristic | Total (N = 69) |
H-aPLA2R-RTX (N = 28) |
H-aPLA2R-TAC (N = 21) |
H-aPLA2R-CTX (N = 20) |
P Value |
|---|---|---|---|---|---|
| Age, yr | 61 ± 11 | 63 ± 11 | 60 ± 12 | 59 ± 8 | 0.46 |
| Male sex, n (%) | 48 (70) | 18 (64) | 15 (71) | 15 (75) | 0.71 |
| Blood pressure, mmHg | |||||
| Systolic | 126.7 ± 16.3 | 125.6 ± 17.4 | 127.5 ± 16.7 | 127.5 ± 15.1 | 0.89 |
| Diastolic | 78.7 ± 11.3 | 75.8 ± 11.4 | 80.5 ± 11.2 | 81.1 ± 10.7 | 0.19 |
| Serum albumin, g/l | 22.8 ± 5.1 | 22.9 ± 4.1 | 23.5 ± 5.3 | 21.9 ± 6.2 | 0.60 |
| Serum creatinine, umol/l | 0.06 | ||||
| Median | 89.0 | 87.5 | 89.0 | 107.0 | |
| Interquartile range | 74.4-109.9 | 73.8–96.8 | 74.3-107.5 | 82.8-175.9 | |
| Proteinuria, g/d | 0.59 | ||||
| Median | 9.5 | 9.5 | 8.0 | 11.3 | |
| Interquartile range | 6.6–13.9 | 6.9–14.2 | 5.3–13.9 | 6.9–14.5 | |
| Anti-PLA2R levels, RU/ml | 0.14 | ||||
| Median | 397.7 | 421.4 | 311.9 | 488.0 | |
| Interquartile range | 289.4-648.1 | 320.8-659.2 | 271.0-457.4 | 270.7-863.7 | |
| eGFR, ml/min/1.73 m² | 78 ± 25 | 84 ± 21 | 80 ± 27 | 68 ± 26 | 0.08 |
yr, year; eGFR, estimated glomerular filtration rate; H-aPLA2R-RTX, Patients with high anti-PLA2R antibody titers treated with rituximab; H-aPLA2R-TAC, Patients with high anti-PLA2R antibody titers treated with tacrolimus; H-aPLA2R-CTX, Patients with high anti-PLA2R antibody titers treated with cyclophosphamide; Values are presented as mean ± SD, n (%), or median (interquartile range); P < 0.05 was statistical difference
Primary outcome
All participants underwent a follow-up of at least 12 months. Among the 77 patients treated with RTX, 36 patients (74%) in the L-aPLA2R-RTX group achieved CR or PR at 12 months, compared with 13 patients (46%) in the H-aPLA2R-RTX group (OR = 3.20, 95% CI:1.20–8.49, p = 0.02) (Table 3). Kaplan-Meier analysis demonstrated a significantly higher cumulative CR or PR rate in the L-aPLA2R-RTX group starting from 6 months of treatment, indicating an earlier onset of remission in this group (Log-rank p = 0.047) (Fig. 2A).
Table 3.
Complete, composite remission and relapse at 3–12 months in patients with different anti-PLA2R antibody titers in rituximab group
| Variables | L-aPLA2R-RTX (N = 49) |
H-aPLA2R-RTX (N = 28) |
OR (95% CI) | P Value |
|---|---|---|---|---|
| Complete remission | ||||
| 3 mo | 2/49 (4) | 0/28 (0) | - | 0.74 |
| 6 mo | 5/49 (10) | 2/28 (7) | 1.48 (0.27–8.17) | 0.97 |
| 12 mo | 16/49 (33) | 3/28 (11) | 4.04 (1.06–15.40) | 0.03 |
| Complete or partial remission | ||||
| 3 mo | 13/49 (27) | 7/28 (25) | 1.08 (0.38–3.14) | 0.88 |
| 6 mo | 29/49 (59) | 11/28 (39) | 2.24 (0.87–5.79) | 0.09 |
| 12 mo | 36/49 (74) | 13/28 (46) | 3.20 (1.20–8.49) | 0.02 |
| Relapse | 0/49 (0) | 2/28 (7) | 0.35 (0.25–0.47) | 0.25 |
L-aPLA2R-RTX, Patients with low anti-PLA2R antibody titers treated with rituximab; H-aPLA2R-RTX, Patients with high anti-PLA2R antibody titers treated with rituximab; Values are presented as No. of Patients with Remission/Total No. (%); P < 0.05 was statistical difference
Fig. 2.
Kaplan-Meier analysis of remission outcomes by treatment group. Kaplan-Meier analysis of (A) complete or partial remission and (B) complete remission in the L-aPLA2R-RTX and H-aPLA2R-RTX groups. Kaplan-Meier analysis of (C) complete or partial remission and (D) complete remission in the H-aPLA2R-RTX, H-aPLA2R-TAC and H-aPLA2R-CTX groups. L-aPLA2R-RTX, Patients with low anti-PLA2R antibody titers treated with rituximab; H-aPLA2R-RTX, Patients with high anti-PLA2R antibody titers treated with rituximab; H-aPLA2R-TAC, Patients with high anti-PLA2R antibody titers treated with tacrolimus; H-aPLA2R-CTX, Patients with high anti-PLA2R antibody titers treated with cyclophosphamide
In the second phase, 13 participants (46%) in the H-aPLA2R-RTX, 14 (70%) in the H-aPLA2R-CTX group, and 15 (71%) in the H-aPLA2R-TAC group achieved CR or PR at 12 months (p = 0.13; Table 4). As shown in Fig. 2B, differences in the cumulative CR or PR rates emerged among the three groups as early as 3 months, though these were not statistically significant (Log-rank p = 0.22).
Table 4.
Complete, composite remission and relapse at 3–12 months in patients with higher anti-PLA2R antibody titers according to treatment group
| Variables | H-aPLA2R-RTX (N = 28) |
H-aPLA2R-TAC (N = 21) |
H-aPLA2R-CTX (N = 20) |
P Value |
|---|---|---|---|---|
| Complete remission | ||||
| 3 mo | 0/28 (0) | 1/21 (5) | 0/20 (0) | 0.31 |
| 6 mo | 2/28 (7) | 4/21 (19) | 2/20 (10) | 0.42 |
| 12 mo | 3/28 (11) | 13/21 (62) | 5/20 (25) | 0.001 |
| Complete or partial remission | ||||
| 3 mo | 7/28 (25) | 8/21 (38) | 5/20 (25) | 0.54 |
| 6 mo | 11/28 (39) | 14/21 (67) | 13/20 (65) | 0.09 |
| 12 mo | 13/28 (46) | 15/21 (71) | 14/20 (70) | 0.13 |
| Relapse | 2/28 (7) | 2/21 (10) | 2/20 (10) | 0.93 |
H-aPLA2R-RTX, Patients with high anti-PLA2R antibody titers treated with rituximab; H-aPLA2R-TAC, Patients with high anti-PLA2R antibody titers treated with tacrolimus; H-aPLA2R-CTX, Patients with high anti-PLA2R antibody titers treated with cyclophosphamide; Values are presented as No. of Patients with Remission/Total No. (%); P < 0.05 was statistical difference
Secondary outcome
At 12 months, the CR rates were 33% and 11% in the L-aPLA2R-RTX group and H-aPLA2R-RTX group, respectively (OR = 4.04, 95% CI:1.06–15.40; p = 0.03) (Table 3). The cumulative rate of CR rates between the two groups showed a difference starting at 3 months, but was not statistically different (Log-rank p = 0.09) (Fig. 2C). The CR rates at 12 months were 11%, 25% and 62% for H-aPLA2R-RTX, H-aPLA2R-CTX and H-aPLA2R-TAC group, respectively (p = 0.001) (Table 4). Kaplan-Meier analysis further demonstrated that the cumulative rate of CR in the H-aPLA2R-TAC and H-aPLA2R-CTX groups became significantly higher than that of the H-aPLA2R-RTX group starting from 3 months and remained consistently elevated throughout the study period, especially most prominent in the H-aPLA2R-TAC (Log-rank p<0.001) (Fig. 2D).
In the L-aPLA2R-RTX group, proteinuria decreased from a baseline level of 8.0 g/d (IQR, 5.9–12.0) to 1.7 g/d (0.3–3.5) at 12 months. In contrast, the H-aPLA2R-RTX group showed a reduction from 9.5 g/d (6.9–14.2) at baseline to 3.7 g/d (0.8–4.9) at 12 months (p = 0.045) (Fig. 3A). Although serum albumin levels increased in both groups during the 12-month follow-up, the intergroup difference was not statistically significant (Fig. 3B). Similarly, changes in eGFR and serum creatinine between the two groups did not reach statistical significance (Fig. 3A-B). Furthermore, among H-aPLA2R-RTX, H-aPLA2R-TAC and H-aPLA2R-CTX group, changes in each of the laboratory parameters from baseline to 12 months were also not significant (Fig. 3C-D).
Fig. 3.
Changes in clinical indicators during follow-up across the different groups. Evolution of proteinuria, serum albumin, Scr, and eGFR. Data are presented as median (interquartile range) (proteinuria and Scr) or mean ± SD (serum albumin and eGFR) of follow-up times. eGFR, estimated glomerular filtration rate; Scr, serum creatinine; L-aPLA2R-RTX, Patients with low anti-PLA2R antibody titers treated with rituximab; H-aPLA2R-RTX, Patients with high anti-PLA2R antibody titers treated with rituximab; H-aPLA2R-TAC, Patients with high anti-PLA2R antibody titers treated with tacrolimus; H-aPLA2R-CTX, Patients with high anti-PLA2R antibody titers treated with cyclophosphamide. * p < 0.05
No relapse events were observed in the L-aPLA2R-RTX group, whereas 2 of the 28 patients (7%) in the H-aPLA2R-RTX group experienced relapse after initial remission (p = 0.25) (Table 3). Similarly, 2 relapse events were recorded in each of the H-aPLA2R-RTX (7%), H-aPLA2R-TAC (10%) and H-aPLA2R-CTX (10%) groups, with no significant difference among them (p = 0.93) (Table 4). During the entire follow-up period, 20 patients (41%) in the L-aPLA2R-RTX group and 19 patients (68%) in the H-aPLA2R-RTX group received additional doses of RTX treatment.
Post hoc subgroup analysis
Post-hoc analyses showed that after adjusting for baseline data, a higher proportion of patients in the H-aPLA2R-TAC or H-aPLA2R-CTX groups continued to achieve CR or PR at 12 months than in the H-aPLA2R-RTX group (HR = 1.88, 95% CI: 0.97–3.62) (Fig. 4).
Fig. 4.
Post hoc subgroup analyses of the primary composite outcome in patients with high anti-PLA2R antibodies. Post hoc subgroup analyses of complete or partial remission of conventional treatment regimens (TAC or CTX) and rituximab treatment in patients with high anti-PLA2R antibodies at month 12, based on baseline data. TAC, tacrolimus; CTX, cyclophosphamide
Furthermore, a significant interaction between baseline aPLA2R antibodies and treatment response was observed (P-interaction = 0.01) (Fig. 4), indicating that patients with lower aPLA2R antibodies respond better to RTX, while those with higher aPLA2R antibodies are better able to benefit from TAC or CTX.
Adverse events
The incidence of adverse events was significantly lower in the L-aPLA2R-RTX group compared to the H-aPLA2R-RTX group (22% vs. 47%, p = 0.03) (Table 5). Additionally, adverse events were reported in 13 patients (46%) in the H-aPLA2R-RTX group, 7 patients (33%) in the H-aPLA2R-TAC group, and 14 patients (70%) in the H-aPLA2R-CTX group (p = 0.06) (Table 5). Specifically, the most frequent adverse events in the H-aPLA2R-RTX group were drug infusion reactions and drug intolerance. In contrast, adverse events such as infections and steroidal diabetes were more likely to occur in the H-aPLA2R-CTX and H-aPLA2R-TAC groups. All adverse events were taken seriously and dealt with proactively, and no serious adverse events occurred. No cases of malignancy or death occurred in any of patients during the 12-month follow-up period.
Table 5.
Adverse events according to anti-PLA2R antibody titers and treatment groups
| Event | L-aPLA2R-RTX (N = 49) |
H-aPLA2R-RTX (N = 28) |
P Value | H-aPLA2R-RTX (N = 28) |
H-aPLA2R-TAC (N = 21) |
H-aPLA2R-CTX (N = 20) |
P Value |
|---|---|---|---|---|---|---|---|
| Any adverse eventa | 11/11 | 13/14 | 0.03 | 13/14 | 7/8 | 14/17 | 0.06 |
| Infections | |||||||
| Pneumonia | 2 (4) | 2 (7) | 0.96 | 2 (7) | 3 (14) | 4 (20) | 0.42 |
| Urinary tract infections | 1 (2) | 1 (4) | 1.00 | 1 (4) | 2 (10) | 3 (15) | 0.38 |
| Tuberculosis | 0 (0) | 0 (0) | - | 0 (0) | 0 (0) | 1 (5) | 0.29 |
| Skin infection | 0 (0) | 1 (4) | 0.78 | 1 (4) | 0 (0) | 1 (5) | 0.61 |
| Steroidal diabetes | 0 (0) | 0 (0) | - | 0 (0) | 3 (14) | 7 (35) | 0.003 |
|
Drug infusion reactions /drug intolerance |
8 (16) | 10 (36) | 0.05 | 10 (36) | 0 (0) | 1 (5) | 0.001 |
L-aPLA2R-RTX, low-titer aPLA2R rituximab; H-aPLA2R-RTX, Patients with high anti-PLA2R antibody titers treated with rituximab; H-aPLA2R-TAC, Patients with high anti-PLA2R antibody titers treated with tacrolimus; H-aPLA2R-CTX, Patients with high anti-PLA2R antibody titers treated with cyclophosphamide; Values are presented as No. of Patients with adverse events (%); a, No. of patients with adverse events/the No. of total events; P < 0.05 was statistical difference
Discussion
The results of this study support that RTX is more effective in achieving sustained proteinuria remission in PMN patients with lower aPLA2R antibody titers compared with those with higher titers. Furthermore, in patients with high aPLA2R antibody titers, TAC or CTX outperformed RTX in sustaining proteinuria remission over 12 months, with TAC showing the most pronounced effect. Notably, patients in the H-aPLA2R-TAC and H-aPLA2R-CTX groups also achieved earlier clinical remission compared to those in the H-aPLA2R-RTX group, as differences in cumulative CR or composite remission were already apparent by the third month of treatment. These results highlight the clinical importance of quantitative assessment of serum aPLA2R antibody titers in guiding the initial therapeutic strategy for PMN.
In our study, when RTX was used as the initial therapy for PMN patients, those in the L-aPLA2R-RTX group had a CR or PR rate of 74% at 12 months, comparable to rates reported in several prior studies: 69.1% in the study by Ruggenenti et al. [17], 62.0% in the RI-CYCLO study [18], 60.0% in the MENTOR study [19] and 64.9% in the GEMRITUX study [20]. This may be related to the median baseline anti-aPLA2R antibody level in the L-aPLA2R-RTX group (67.1 RU/ml), which was comparable to the median levels observed in the overall populations of studies such as RI-CYCLO (63 RU/ml) and GEMRITUX (40.5 RU/ml). In addition, we also observed a significantly higher CR rate of 33% and a composite remission rate of 74% in the L-aPLA2R-RTX compared with those in the H-aPLA2R-RTX group of 11% and 46% at month 12. Importantly, a recent cohort study from Italy have further expanded upon the findings of Teisseyre et al., reporting that patients who developed ARAs exhibited significantly lower remission rates [11]. Moreover, their study observed a marked difference in baseline aPLA2R antibody titers between ARA-positive and ARA-negative patients, providing additional support for an association between baseline aPLA2R antibody levels and treatment response.
RTX has long been recommended as the preferred first-line treatment option for patients with intermediate to high-risk PMN [4, 17]. However, our study suggests that its efficacy may be limited in patients with high titers of aPLA2R. We observed that among patients with high baseline aPLA2R antibodies, the CR rates at months 3 and 6 in the RTX group were slightly lower than those in the TAC and CTX groups. Although these differences were not statistically significant at early time points, by month 12, the CR rate in the RTX group was significantly lower than the other two groups. This observation was further confirmed through post hoc subgroup analysis. These results are consistent with the findings of Logt et al. [21], which reported that even with a cumulative RTX dose of 2 g, its immunologic induction efficacy in patients with high aPLA2R antibodies was inferior to that of CTX during a 6-month follow-up. This phenomenon can be explained by the delayed onset of RTX in the study of Dahan et al. [22], in which the reduction in proteinuria was usually delayed until after 6 months of treatment. Furthermore, the study by Teisseyre et al. [10] found that ARAs were most commonly detected at a median of 9 months (6–12) post-treatment, which may diminish the late maintenance effect of RTX.
With regards to pharmacological mechanisms, TAC rapidly reduces proteinuria in the short term through a dual mechanism. On the one hand, it exerts non-immune podocyte protection by directly stabilizing the podocyte cytoskeleton and reducing podocyte fusion [23, 24]. On the other hand, as a calcineurin inhibitor, it persistently suppresses T-cell function, thereby indirectly inhibiting the production of pathogenic antibodies [25]. In contrast, CTX suppresses T-cell and B-cell activation through cytotoxic effects, also facilitating long-term control of immune activity, but lacks direct podocyte protection [26, 27]. These mechanistic differences may confer greater potential to TAC than CTX in inducing and sustaining deep clinical remission. Furthermore, these mechanisms help explain why TAC and CTX appear more effective than RTX in patients with higher aPLA2R antibody titers. Naturally, prospective studies with larger sample sizes are needed to further validate these findings.
In terms of adverse events, no statistically significant difference was observed in the H-aPLA2R-TAC and H-aPLA2R-CTX groups compared to the H-aPLA2R-RTX group. This is consistent with the findings of RI-CYCLO study [18]. The relapse rates within 12 months were 10% in the H-aPLA2R-TAC group, 10% in the H-aPLA2R-CTX group, and 7% in the H-aPLA2R-RTX group, which were not statistically different but were generally lower than the data from previous studies [28–30]. This may be related to the relatively short follow-up period of our study. Notably, in response to the high relapse rate after discontinuation of CNIs, it has been suggested in recent years that combining treatment with RTX during tapering of CNIs can help reduce the risk of relapse due to discontinuation [31–33]. Therefore, in the future, combination or sequential treatment strategies based on individual immune status assessment could continue to be explored in depth to optimize long-term outcomes and safety.
There are several limitations in this study. Firstly, as a single-center retrospective cohort study, the risk of selection bias and confounding factors cannot be fully excluded. Secondly, dynamic changes in aPLA2R antibody titers were not systematically analyzed, which limited our in-depth exploration of the relationship between antibody trends and clinical response. Thirdly, patients received different RTX treatment regimens, although no significant differences were observed between the regimens. Finally, due to the high cost, this study did not assess the presence of ARAs and residual rituximab levels, which is a limitation worth noting. A significant association between high serum aPLA2R antibody titers and the presence of ARAs has been demonstrated. Thus, the results observed in the high titers of aPLA2R antibody group may be related, at least in part, to the presence of ARAs. Nevertheless, this study provides important clinical evidence supporting the role of baseline aPLA2R antibody titers in guiding individualized treatment for PMN.
In conclusion, this study highlights the potential value of baseline serum aPLA2R antibody titers in guiding the initial immunosuppressive treatment strategy for PMN. It is the first to suggest that in patients with high aPLA2R antibody titers, conventional immunosuppressive regimens (particularly TAC) may be superior to RTX in achieving and maintaining proteinuria remission.
Supplementary Information
Below is the link to the electronic supplementary material.
Acknowledgements
Not applicable.
Author contributions
Research idea and study design: LS and BK; data acquisition: HLC and XTL; data analysis/interpretation and statistical analysis: HLC and XTL; supervision and mentorship: LS and BK. Observation of drug safety and side effects: LS and BK.
Funding
This work was supported by grants from the Natural Science Foundation of China (82360145 and 82560145).
Data availability
The datasets used or analyzed during the current study are available from the corresponding author upon reasonable request.
Declarations
Ethical approval and consent to participate
The study was conducted in accordance with the Declaration of Helsinki and was approved by the Bioethics Committee of The Second Affiliated Hospital to Nanchang University (IRB approval no.: The Second Affiliated Hospital to Nanchang University, 257). All patients were unrelated. All patients signed an informed consent for participation prior to their inclusion in the study.
Consent for publication
Not applicable.
Competing interests
The authors declare no competing interests.
Footnotes
Correspondence with articles is handled by Ben Ke at all stages of the refereeing and publication process and post-publication.
Publisher’s note
Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.
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Associated Data
This section collects any data citations, data availability statements, or supplementary materials included in this article.
Supplementary Materials
Data Availability Statement
The datasets used or analyzed during the current study are available from the corresponding author upon reasonable request.