Abstract
Objective: To assess the combined therapeutic effects of belimumab and mycophenolate mofetil (MMF) in severe lupus nephritis (LN), focusing on renal recovery, immune regulation, and long-term outcome. Methods: We retrospectively analyzed data from 188 patients hospitalized between March 2019 and April 2022. Of these, 106 received belimumab (10 mg/kg) in addition to standard therapy, while 82 received standard care alone. Endpoints included renal function indices (proteinuria, serum creatinine, albumin), Systemic Lupus Erythematosus Disease Activity Index (SLEDAI) scores, anti-dsDNA antibody titers, complement C3 and C4 levels, and inflammatory markers (hs-CRP, IL-6, TNF-α). Remission rates were calculated, and prognostic factors for end-stage renal disease (ESRD) and mortality were evaluated using Cox regression and competing risk analysis. Results: The combination therapy yielded a 94% remission rate, significantly higher than the 70% observed for controls (P<0.001). Complete remission was achieved in about 50% of treated patients, compared to 40% in the control group (P=0.025), with a notably lower non-responder rate. Belimumab-treated patients exhibited greater reductions in proteinuria, serum creatinine, SLEDAI score, erythrocyte sedimentation rate (ESR), and inflammatory cytokines, alongside increases in albumin and complement levels (all P<0.001). Baseline creatinine and albumin levels were consistent predictors of ESRD (P<0.001) and mortality (P=0.006) by multivariate and competing risk analyses. Conclusion: In severe LN, the combination of belimumab and MMF provided superior improvements in renal function, immune status, and long-term prognosis compared to standard therapy. Baseline renal biomarkers, particularly creatinine and albumin, may guide patient stratification and personalized treatment approaches.
Keywords: Belimumab, mycophenolate mofetil, lupus nephritis, clinical efficacy, systemic lupus erythematosus disease activity index, renal function
Introduction
Systemic lupus erythematosus (SLE) is a chronic autoimmune disease marked by impaired immune regulation and excessive activation of inflammatory pathways, leading to damage across multiple organ systems, particularly the kidneys [1]. Lupus nephritis (LN), a severe manifestation of SLE, affects 40-50% of patients and presents with various clinical signs, including proteinuria, hematuria, edema, hypertension, and impaired renal function [2,3]. The extent of renal involvement correlates with overall disease activity and is a key prognostic factor. Severe LN can lead to irreversible kidney damage, progressing to end-stage renal disease (ESRD), which significantly worsens both lifespan and quality of life [4]. Thus, the primary therapeutic goals in severe LN are to restore kidney function, halt progression, and prevent irreversible loss of renal capacity.
Current treatment strategies for severe LN primarily involve glucocorticoids, immunosuppressive agents, and other immunomodulatory drugs [5]. While these therapies improve outcome and slow disease progression, their effectiveness is often limited, and prolonged use is associated with side effects such as increased infection risk, osteoporosis, and metabolic disorders like diabetes [6]. Furthermore, a subset of patients does not respond adequately to standard treatments, highlighting the need for new approaches that offer better efficacy with fewer side effects.
Belimumab, a recombinant humanized monoclonal antibody, is a targeted biological therapy for SLE [7]. It binds to and neutralizes B-cell activating factor (BAFF), reducing abnormal B cell activation, a key mechanism in SLE pathogenesis [8]. Its safety and efficacy have been established in various patient populations, resulting in global regulatory approval for SLE treatment [9]. Another key drug in LN therapy is mycophenolate mofetil (MMF), a potent immunosuppressant that inhibits T and B cell proliferation and antibody production, making it effective for both induction and maintenance therapy in severe LN [10-12]. However, some patients do not respond adequately to either therapy alone, providing a rationale for combining treatments to optimize outcome [13].
While the efficacy of belimumab in SLE is well-documented, evidence on its combination with MMF, specifically for severe LN, is limited [14]. Furthermore, systematic data on the effects of this combination on renal function, immune response, and long-term outcome are scarce. This study aims to fill this gap by evaluating the effects of belimumab plus MMF in severe LN, focusing on renal recovery, immunological markers, and prognosis over extended follow-up.
Materials and methods
Sample size calculation
The required sample size was based on primary efficacy renal response rates reported by Yu et al. [15], with response incidences of 62% for the belimumab group and 37% for the placebo group. These values were used as expected response rates for the treatment (62%) and control (37%) cohorts. Using G*Power software for comparison of two independent proportions, we set a two-sided significance level (α) of 0.05 and statistical power (1 - β) of 90% (β=0.1). The calculation yielded a minimum of 78 participants per study arm. With a 1:1 allocation ratio, the total required sample size was 156 participants, sufficient to maintain the planned statistical power for all analyses.
Functional scoring
The Systemic Lupus Erythematosus Disease Activity Index (SLEDAI) was used to quantify lupus disease activity. SLEDAI integrates 24 clinical and laboratory data across multiple organ systems (neurological, renal, dermatologic, musculoskeletal, hematologic, and immunologic), yielding a total score between 0 and 105. Higher scores reflect greater disease activity. SLEDAI values ≥12 is generally considered indicative of high disease activity, often correlating with multi-organ involvement and increased risk of irreversible organ damage. In LN, a SLEDAI ≥12 is used as a criterion for severe disease, and this threshold was applied to the inclusion criteria for patient enrollment [16].
General information
This retrospective cohort study included 188 patients with severe LN (SLEDAI score ≥12 and pathologic classification of type III/IV) admitted between March 2019 and April 2022. Patients were divided into a combination therapy group (n=106) and a control group (n=82). The study was approved by the medical ethics committee of Tongchuan People’s Hospital.
Inclusion and exclusion criteria
Inclusion criteria: (1) Patients diagnosed with SLE according to the 2023 European Alliance of Associations for Rheumatology Updated Guidelines for SLE Management [17]; (2) Complete clinical data; (3) Renal biopsy confirmation with no contraindications to renal puncture; (4) Newly diagnosed patients in the active phase of LN; (5) Age ≥18 years.
Exclusion criteria: (1) Organ failure other than renal; (2) Coagulation disorders; (3) Infection with human immunodeficiency virus, tuberculosis, or hepatitis B virus; (4) Pregnancy.
Treatment regimens
The control group received conventional therapy, including prednisone acetate tablets (National Pharmaceutical Group Rongsheng Pharmaceutical Co., Ltd.; H41020636; 5 mg/tablet) at 0.5-1.0 mg/kg body weight, administered orally once daily; hydroxychloroquine sulfate tablets (Shanghai Shangsheng Pharmaceutical Co., Ltd.; H19990263; 0.1 g/tablet) at 0.2 g (2 tablets) twice daily orally; and MMF capsules (Qionglai Tianyin Pharmaceutical Co., Ltd.; H20080819; 0.25 g/capsule) at 0.75 g (3 capsules) twice daily orally. Treatment lasted for 6 months, with dosage adjustments based on patient condition and immunological markers to assess efficacy.
The combination group received the same conventional therapy, supplemented with belimumab (GlaxoSmithKline (Ireland) Limited; SJ20190032; 120 mg/vial) at 10 mg/kg body weight, administered by intravenous infusion. Belimumab was given every 2 weeks for the first 6 weeks, then every 4 weeks thereafter. Treatment duration was 6 months, with dosage adjustments and immunological monitoring identical to the control group.
Clinical data collection
At admission, clinical data were recorded, including demographic variables (age, gender, BMI), medical history (diabetes, hypertension), clinical and pathological classifications, and renal biopsy results (class III or IV). Histopathologic changes were described, including tubular atrophy, interstitial inflammatory cell infiltration, and fibrosis. Laboratory tests were performed before treatment and at the 6-month follow-up, assessing renal function (urinary total protein [UTP], serum creatinine [SCr], albumin [Alb]), disease activity (SLEDAI), ESR, immunological markers (anti-double-stranded DNA antibody [ds-DNA], complement components [C3, C4]), and inflammatory mediators (high-sensitivity C-reactive protein [Hs-CRP], interleukin-6 [IL-6], tumor necrosis factor-α [TNF-α]).
Laboratory testing methods
Biochemical and immunological assessments were performed at baseline and after 6 months. Blood and urine samples were processed promptly. UTP, SCr, and Alb were quantified using a Beckman 5800 automated analyzer. Immunological indices (ds-DNA, C3, C4) were measured with a Siemens immunoassay analyzer. Inflammatory markers (hs-CRP, IL-6, TNF-α) were analyzed using enzyme-linked immunosorbent assay (ELISA, Shanghai Enzyme-linked Biotechnology Co., Ltd., China). Disease activity was assessed through SLEDAI scoring, and ESR was determined using the Westergren technique.
Follow-up
Patients were followed up through outpatient records, telephone interviews, and electronic medical records until March 2025. Follow-up occurred every 4 months in the first year and every 6 months thereafter. At each follow-up, clinical data, laboratory markers, adverse events, treatment efficacy, and health status were recorded. Composite endpoint events included all-cause mortality or progression to ESRD, with the endpoint defined as the first occurrence of either.
Outcome measurements
Primary outcomes
Comparison of clinical efficacy across treatment regimens and identification of independent prognostic factors for endpoint events.
Secondary outcomes
Assessment of changes in renal function, immune response, and inflammatory status pre- and post-treatment.
Statistical analysis
Data were analyzed using SPSS 27.0. Categorical variables were expressed as percentages and compared using the Chi-square test. Continuous variables were tested for normality with the Kolmogorov-Smirnov test. Normally distributed variables were expressed as mean ± standard deviation (SD) and compared using independent or paired t-tests; non-normally distributed variables were expressed as median (interquartile range) and compared using the Mann-Whitney U test. Kaplan-Meier survival curves evaluated survival differences between groups, with comparisons made by the Log-rank test. Competing risk analysis assessed risk factors for endpoint events (ESRD, death). Time-dependent receiver operating characteristic (ROC) curve analysis, conducted with the “timeROC” package in R, evaluated the predictive performance of clinical variables for adverse outcomes at 1, 2, and 3 years, with the area under the curve (AUC) indicating discrimination ability. Correlation analyses used Pearson’s coefficient for normally distributed variables and Spearman’s coefficient for non-normally distributed variables. All tests were two-sided, with significance set at P<0.05.
Results
Comparison of baseline characteristics
Baseline characteristics, including age, gender, BMI, diabetes, hypertension, clinical classification, pathological classification, tubular atrophy, interstitial inflammatory cell infiltration, and interstitial fibrosis showed no significant differences between the groups (all P>0.05, Table 1).
Table 1.
Patient baseline characteristics
| Factor | Total | Combination Therapy Group (n=106) | Control Group (n=82) | Statistic | P-value |
|---|---|---|---|---|---|
| Age (years) | 33.72±10.09 | 33.80±9.85 | 33.61±10.44 | 0.129 | 0.897 |
| Gender | 0.856 | 0.355 | |||
| Male | 155 (82.45%) | 85 (80.19%) | 70 (85.37%) | ||
| Female | 33 (17.55%) | 21 (19.81%) | 12 (14.63%) | ||
| BMI (kg/m2) | 23.21±1.41 | 23.11±1.40 | 23.35±1.42 | -1.178 | 0.240 |
| Diabetes | 1.183 | 0.277 | |||
| Yes | 24 (12.77%) | 16 (15.09%) | 8 (9.76%) | ||
| No | 164 (87.23%) | 90 (84.91%) | 74 (90.24%) | ||
| Hypertension | 1.088 | 0.297 | |||
| Yes | 16 (8.51%) | 11 (10.38%) | 5 (6.10%) | ||
| No | 172 (91.49%) | 95 (89.62%) | 77 (93.90%) | ||
| Clinical Classification | 0.564 | 0.453 | |||
| Nephrotic Syndrome | 118 (62.77%) | 69 (65.09%) | 49 (59.76%) | ||
| Acute Nephritis | 70 (37.23%) | 37 (34.91%) | 33 (40.24%) | ||
| Pathological Classification | 0.308 | 0.579 | |||
| III | 115 (61.17%) | 63 (59.43%) | 52 (63.41%) | ||
| IV | 73 (38.83%) | 43 (40.57%) | 30 (36.59%) | ||
| Tubular Atrophy | 0.527 | 0.913 | |||
| None | 29 (15.43%) | 16 (15.09%) | 13 (15.85%) | ||
| Focal | 34 (18.09%) | 18 (16.98%) | 16 (19.51%) | ||
| Multifocal | 65 (34.57%) | 36 (33.96%) | 29 (35.37%) | ||
| Diffuse | 60 (31.91%) | 36(33.96%) | 24 (29.27%) | ||
| Interstitial Inflammatory Cell Infiltration | 1.055 | 0.788 | |||
| None | 18 (9.57%) | 9 (8.49%) | 9 (10.98%) | ||
| Focal | 23 (12.23%) | 12 (11.32%) | 11 (13.41%) | ||
| Multifocal | 71 (37.77%) | 39 (36.79%) | 32 (39.02%) | ||
| Diffuse | 76 (40.43%) | 46 (43.40%) | 30 (36.59%) | ||
| Interstitial Fibrosis | 1.306 | 0.728 | |||
| None | 14 (7.45%) | 7 (6.60%) | 7 (8.54%) | ||
| Focal | 26 (13.83%) | 13 (12.26%) | 13 (15.85%) | ||
| Multifocal | 62 (32.98%) | 34 (32.08%) | 28 (34.15%) | ||
| Diffuse | 86 (45.74%) | 52 (49.06%) | 34 (41.46%) |
Note: BMI = Body Mass Index.
Comparison of clinical efficacy
The combination therapy group achieved a significantly higher total remission rate compared to the control group (94.23% vs. 70.49%, P<0.001). Specifically, the combination group had a complete remission rate of 50.00%, compared to 40.24% for the control group (P=0.025), and a partial remission rate of 46.23% versus 40.24%. The non-remission rate was significantly lower for the combination group (3.77% vs. 19.51%, P<0.001) (Table 2).
Table 2.
Comparison of efficacy evaluation in treatment of severe lupus nephritis
| Group | Combination Therapy Group (n=106) | Control Group (n=82) | Χ2/Z | P-value |
|---|---|---|---|---|
| Complete Remission | 53 (50.00%) | 33 (40.24%) | 2.238 | 0.025 |
| Partial Remission | 49 (46.23%) | 33 (40.24%) | ||
| No Remission | 4 (3.77%) | 16 (19.51%) | ||
| Total Remission Rate (%) | 102 (96.23%) | 66 (80.49%) | - | <0.001 |
Note: Chi-square test using Fisher’s exact test.
Comparison of renal function markers
The combination therapy group demonstrated greater improvements in UTP, SCr, and Alb (all P<0.001). Intra-group differences were significant for UTP and Alb in both groups (both P<0.001). However, inter-group differences in UTP (P=0.713) and SCr (P=0.555) before and after treatment were not significant, although the combination group showed superior overall improvement (Table 3).
Table 3.
Comparison of changes in renal function-related indicators before and after treatment in both groups (UTP, SCr, Alb)
| Group | Combination Therapy Group (n=106) | Control Group (n=82) | t/Z | P-value | |
|---|---|---|---|---|---|
| UTP (g/24 h) | Before Treatment | 4.90 (1.47) | 4.85 (1.30) | 0.368 | 0.713 |
| After Treatment | 1.30 (0.30)* | 2.20 (0.40)* | 11.687 | <0.001 | |
| SCr (μmol/L) | Before Treatment | 159.64±28.06 | 157.29±25.61 | 0.591 | 0.555 |
| After Treatment | 73.47±15.84* | 93.98±17.50* | -8.406 | <0.001 | |
| Alb (g/L) | Before Treatment | 23.00±2.76 | 23.66±3.00 | -1.579 | 0.116 |
| After Treatment | 33.07±3.72* | 29.80±2.71* | 6.711 | <0.001 | |
P<0.05 compared to pretreatment;
UTP = Urinary Total Protein, SCr = Serum Creatinine, Alb = Albumin.
Comparison of SLEDAI scores and ESR
Both groups exhibited significant reductions in SLEDAI scores and ESR post-treatment (both P<0.001). The combination therapy group showed greater improvements in SLEDAI scores and ESR, although inter-group differences were not statistically significant (P=0.863 for SLEDAI, P=0.75 for ESR) (Table 4).
Table 4.
Comparison of changes in SLEDAI scores and ESR before and after treatment in both groups
| Group | Combination Therapy Group (n=106) | Control Group (n=82) | t/Z | P-value | |
|---|---|---|---|---|---|
| SLEDAI Score | Before Treatment | 17.00 (5.00) | 17.00 (5.75) | 0.172 | 0.863 |
| After Treatment | 7.00 (4.00)* | 9.00 (2.00)* | 5.289 | <0.001 | |
| ESR (mm/h) | Before Treatment | 59.20±12.46 | 59.80±13.54 | -0.319 | 0.75 |
| After Treatment | 29.33±8.51* | 39.20±9.42* | -7.523 | <0.001 | |
P<0.05 compared to pretreatment;
SLEDAI = Systemic Lupus Erythematosus Disease Activity Index, ESR = Erythrocyte Sedimentation Rate.
Comparison of immunological markers
Both groups showed significant improvements in ds-DNA, C3, and C4 levels post-treatment (all P<0.001). The combination therapy group demonstrated more pronounced improvements in C3 and C4 (both P<0.001). Inter-group differences in ds-DNA were not significant (P=0.992), but overall improvements in immunological markers were greater in the combination group (Table 5).
Table 5.
Comparison of changes in ds-DNA, C3, and C4 before and after treatment in both groups
| Group | Combination Therapy Group (n=106) | Control Group (n=82) | t/Z | P-value | |
|---|---|---|---|---|---|
| ds-DNA (IU/L) | Before Treatment | 39.49±5.63 | 39.49±6.33 | 0.01 | 0.992 |
| After Treatment | 18.98±3.20* | 26.62±4.31* | -13.947 | <0.001 | |
| C3 (g/L) | Before Treatment | 0.37±0.11 | 0.38±0.11 | -0.623 | 0.534 |
| After Treatment | 0.58±0.10* | 0.51±0.11* | 4.464 | <0.001 | |
| C4 (g/L) | Before Treatment | 0.08 (0.03) | 0.08 (0.03) | 1.198 | 0.231 |
| After Treatment | 0.15 (0.06)* | 0.11 (0.04)* | 5.354 | <0.001 | |
P<0.05 compared to pretreatment;
ds-DNA = Double-Stranded DNA, C3 = Complement 3, C4 = Complement 4.
Comparison of inflammatory markers
Both groups showed significant reductions in inflammatory markers (hs-CRP, IL-6, and TNF-α) - post-treatment (all P<0.001). The combination therapy group showed significant intra-group reductions in all markers (P<0.001). Inter-group differences were significant for IL-6 (P<0.001), but not for Hs-CRP (P=0.675) or TNF-α (P=0.139). Overall, the combination group exhibited superior reductions in inflammatory markers (Table 6).
Table 6.
Comparison of changes in inflammatory factors before and after treatment in both groups
| Group | Combination Therapy Group (n=106) | Control Group (n=82) | t/Z | P-value | |
|---|---|---|---|---|---|
| Hs-CRP (mg/mL) | Before Treatment | 40.41±5.91 | 40.79±6.55 | -0.42 | 0.675 |
| After Treatment | 15.29±2.73* | 18.56±3.40* | -7.322 | <0.001 | |
| IL-6 (ng/mL) | Before Treatment | 80.95 (10.57) | 80.35 (9.15) | 0.104 | 0.917 |
| After Treatment | 44.91±5.12* | 49.61±4.18* | -6.762 | <0.001 | |
| TNF-α (ng/mL) | Before Treatment | 108.13±10.32 | 105.76±11.52 | 1.485 | 0.139 |
| After Treatment | 53.24±6.13* | 61.69±6.11* | -9.376 | <0.001 | |
P<0.05 compared to pretreatment;
Hs-CRP = High-Sensitivity C-Reactive Protein, IL-6 = Interleukin 6, TNF-α = Tumor Necrosis Factor Alpha.
Association between clinical variables and prognosis
Correlation analysis showed that pre-treatment serum creatinine (SCr) (r=0.290, P<0.001), SLEDAI score (r=0.236, P=0.001), clinical classification (r=0.215, P=0.003), albumin (Alb) (r=0.185, P=0.011), and treatment regimen (r=-0.172, P=0.019) were weakly associated with prognosis. Higher SCr, SLEDAI score, and more severe clinical classification were associated with worse outcome, while lower Alb levels were linked to poorer prognosis. The treatment regimen showed a weak negative correlation, suggesting a possible protective effect. No significant associations were observed with the following variables: tubular atrophy (r=-0.115, P=0.116), pre-treatment ESR (r=-0.109, P=0.138), age (r=-0.089, P=0.227), hypertension (r=-0.084, P=0.253), pre-treatment C3 (r=0.079, P=0.282), pre-treatment C4 (r=-0.076, P=0.297), pre-treatment TNF-α (r=0.064, P=0.381), pre-treatment IL-6 (r=0.058, P=0.429), pre-treatment ds-DNA (r=-0.053, P=0.473), BMI (r=-0.045, P=0.543), pre-treatment UTP (r=0.032, P=0.664), gender (r=-0.023, P=0.751), interstitial inflammatory cell infiltration (r=-0.016, P=0.824), interstitial fibrosis (r=0.011, P=0.880), pre-treatment Hs-CRP (r=-0.009, P=0.898), pathological classification (r=0.007, P=0.928), and diabetes (r=-0.006, P=0.936) (Figure 1).
Figure 1.
Correlation analysis of clinical variables and patient prognosis.
Prognostic differences by Kaplan-Meier survival analysis
Kaplan-Meier survival analysis showed that the combination therapy group had a significantly lower risk of adverse outcome compared to the control group (P=0.017, Figure 2A). Patients with acute nephritis had a higher risk of poor outcome than those with nephrotic syndrome (P=0.004, Figure 2B). Pre-treatment SCr (P<0.001, Figure 2C), pre-treatment Alb (P=0.004, Figure 2D), and pre-treatment SLEDAI score >15 (P<0.001, Figure 2E) were significantly associated with worse prognosis.
Figure 2.
Kaplan-Meier survival curves for combination therapy group and control group under different clinical classifications, tubular atrophy types, and pre-treatment indicators. A. Treatment Regimen: Kaplan-Meier curves for OS between the combination therapy group and control group, with the combination therapy group having longer survival. B. Clinical Classification: Kaplan-Meier curves for OS between patients with nephrotic syndrome and acute nephritis, with acute nephritis patients having shorter survival. C. Pre-treatment SCr: Kaplan-Meier curves for OS between patients with lower and higher pre-treatment serum creatinine (SCr) levels, with lower SCr levels associated with longer survival. D. Pre-treatment Alb: Kaplan-Meier curves for OS between patients with lower and higher pre-treatment albumin (Alb) levels, with higher Alb levels associated with longer survival. E. Pre-treatment SLEDAI Score: Kaplan-Meier curves for OS between patients with lower and higher pre-treatment SLEDAI scores, with lower SLEDAI scores associated with longer survival. Note: SLEDAI = Systemic Lupus Erythematosus Disease Activity Index, SCr = Serum Creatinine, Alb = Albumin.
Temporal predictive performance of clinical variables
Time-dependent ROC analysis evaluated the prognostic performance of key clinical variables at 1, 2, and 3 years. The treatment regimen (Figure 3A) showed increasing predictive power over time (AUCs: 0.681, 0.683, 0.692). Pre-treatment SCr (Figure 3C) exhibited the highest predictive performance (AUC=0.757 at year 3). Pre-treatment Alb (Figure 3D) had limited predictive value initially but reached an AUC of 0.689 by year 3. Clinical classification (Figure 3B) showed poor prognostic discrimination (AUCs ~0.5). Pre-treatment SLEDAI score (Figure 3E) had consistently low AUCs (<0.6), indicating limited prognostic value. Treatment regimen and pre-treatment SCr were the most reliable predictors of adverse outcome, particularly at year 3.
Figure 3.
Time-dependent ROC curves of relevant factors for predicting prognosis in patients. A. ROC curves of Treatment Regimen for predicting poor prognosis at 1, 2, and 3 years in patients. B. ROC curves of Clinical Classification for predicting poor prognosis at 1, 2, and 3 years in patients. C. ROC curves of Pre-treatment SCr for predicting poor prognosis at 1, 2, and 3 years in patients. D. ROC curves of Pre-treatment Alb for predicting poor prognosis at 1, 2, and 3 years in patients. E. ROC curves of Pre-treatment SLEDAI score for predicting poor prognosis at 1, 2, and 3 years in patients.
Discussion
This study evaluated the clinical efficacy of belimumab combined with MMF in treating severe LN, focusing on its effects on renal function, immune response, and long-term prognosis. SLE is a chronic autoimmune disease, with LN being a frequent and severe complication. While conventional treatments alleviate symptoms, they are associated with significant adverse effects, and some patients show suboptimal responses. Belimumab, a recombinant humanized monoclonal antibody, inhibits BAFF, thereby reducing autoimmune activity. When combined with MMF, a potent immunosuppressive agent, this regimen enhances immune modulation. By assessing clinical outcomes, renal function, and immunological markers, this study provides evidence for a novel therapeutic strategy for severe LN, offering a promising option for affected patients.
Our results demonstrate that belimumab combined with MMF significantly improves clinical outcomes in severe LN. The combination therapy group showed a markedly higher overall remission rate than the control group, with increases in both complete remission and partial remission. Conversely, the proportion of patients without remission was significantly reduced for the combination group (3.77% vs. 19.51%, P<0.001), highlighting a clear therapeutic advantage. These findings are consistent with the phase 2 proof-of-concept study by Kraaij et al. [18], in which combined B-cell targeted therapy with rituximab and belimumab achieved substantial renal responses in patients with severe, refractory LN. Similarly, Gatto et al. [19] in a multicenter real-world analysis found that the addition of belimumab resulted in primary and complete renal responses in most LN patients, further supporting our findings and reinforcing belimumab’s role as an effective adjunct in LN management.
Regarding renal function, patients receiving the combined regimen showed significant post-treatment improvements in UTP, SCr, and Alb levels. Similar trends were observed by Sumichika et al. [20], who reported reductions in both SLEDAI scores and glucocorticoid requirements in SLE patients treated with belimumab. In our study, the combination group also showed significant declines in SLEDAI scores and ESR, suggesting effective suppression of disease activity. The enhanced therapeutic effect likely reflects complementary mechanisms of action: belimumab reduces B cell activation by binding BAFF, while MMF suppresses purine synthesis, limiting T- and B-cell proliferation [21,22].
In immunological assessments, anti-dsDNA antibodies, complement C3, and C4 improved significantly in the combination group. Inflammatory markers, including Hs-CRP, IL-6, and TNF-α, also showed reductions. Stohl et al. [23] provided mechanistic insight, showing that prolonged belimumab therapy depletes specific B cell subsets and lowers serum IgG levels. Elevated baseline B cell counts predicted better systemic lupus response index-4 outcomes, while higher plasma cell levels were linked to poorer responses. This suggests that belimumab selectively depletes autoantibody-producing plasma cells, consistent with the immunological changes observed in our study. Parodis et al. [24] also noted that early post-treatment changes in B and plasma cell kinetics could predict disease relapse, with transient B cell expansion followed by memory B cell decline marking sustained remission.
Compared to controls, the combination therapy group exhibited superior results across remission rates, renal indices, and immunological profiles, with larger magnitudes of change in each index. Depascale et al. [25] emphasized that early initiation of belimumab enhances its clinical effect, a principle reflected in our study design. However, they also highlighted unresolved issues such as optimal discontinuation timing and the potential role of combining belimumab with other biologics, suggesting areas for future research. Our findings provide strong evidence that pairing belimumab with MMF may exceed the efficacy of monotherapy. Plüß et al. [8] expanded on belimumab’s molecular mechanism as a fully human IgG1λ monoclonal antibody capable of neutralizing soluble BAFF, a feature that likely strengthens its role in LN therapy.
Correlation and time-dependent ROC curve analyses revealed that pre-treatment SCr and Alb levels were significant predictors of long-term prognosis. These findings are consistent with Gatto et al. [19], who showed that lower baseline creatinine levels predicted better renal responses to belimumab. Liu et al. [26] demonstrated belimumab’s efficacy in severe LN patients requiring dialysis, with most achieving increased urine output and reduced SCr. Ding et al. [27] found that urinary Alb levels were independently associated with histologic severity in LN, indicating Alb’s role as an early marker of renal injury. Nie et al. [28] noted that hypoalbuminemia was linked to serositis in LN, a marker of SLE activity and worse prognosis. Collectively, these studies underscore pre-treatment SCr and Alb as critical prognostic indicators, reflecting the extent and reversibility of renal damage.
Notably, Liu et al. [26] observed belimumab’s effectiveness in dialysis-dependent LN patients, with most discontinuing dialysis and showing reduced SCr levels. This suggests belimumab holds potential for treating severe cases, thereby broadening its therapeutic applicability. Atisha-Fregoso et al. [7] investigated the use of belimumab following rituximab and cyclophosphamide in LN, reporting no significant improvement in clinical efficacy but noting sustained reductions in B-cell levels and enhanced negative selection of autoreactive B cells. These immunologic effects align with our findings, reinforcing belimumab’s role in immune regulation.
Despite its contributions, this study has limitations. As a retrospective cohort study, it was subject to selection and recall biases, which may limit the generalizability of the findings. The follow-up duration of 1 year was relatively short, limiting the ability to assess long-term prognosis fully. Although combination therapy significantly improved short-term outcomes, its long-term effects require extended follow-up. Additionally, the sample size was modest, which may have limited the detection of subtle differences between groups.
Future research should focus on large-scale multicenter randomized controlled trials to validate the long-term efficacy of belimumab combined with MMF, particularly in patients with type III and IV LN pathological classifications. Extended follow-up is needed to assess the regimen’s impact on renal protection and ESRD prevention, ensuring its long-term safety and efficacy.
Conclusion
Belimumab combined with MMF significantly enhanced clinical outcomes in severe LN, with notable improvements in remission rate, renal function, immune response, and inflammatory markers. This combination therapy offers a promising strategy for managing severe LN, particularly for improving short-term clinical efficacy and supporting renal protection.
Disclosure of conflict of interest
None.
References
- 1.Hoi A, Igel T, Mok CC, Arnaud L. Systemic lupus erythematosus. Lancet. 2024;403:2326–2338. doi: 10.1016/S0140-6736(24)00398-2. [DOI] [PubMed] [Google Scholar]
- 2.Zhang Q, Xing P, Ren H, Chen X, Xie J, Zhang W, Shen P, Li X, Chen N. Mycophenolate mofetil or tacrolimus compared with azathioprine in long-term maintenance treatment for active lupus nephritis. Front Med. 2022;16:799–807. doi: 10.1007/s11684-021-0849-2. [DOI] [PubMed] [Google Scholar]
- 3.Furie RA, Rovin BH, Garg JP, Santiago MB, Aroca-Martínez G, Zuta Santillán AE, Alvarez D, Navarro Sandoval C, Lila AM, Tumlin JA, Saxena A, Irazoque Palazuelos F, Raghu H, Yoo B, Hassan I, Martins E, Sehgal H, Kirchner P, Ross Terres J, Omachi TA, Schindler T, Pendergraft WF 3rd, Malvar A REGENCY Trial Investigators. Efficacy and safety of obinutuzumab in active lupus nephritis. N Engl J Med. 2025;392:1471–1483. doi: 10.1056/NEJMoa2410965. [DOI] [PubMed] [Google Scholar]
- 4.Teoh STY, Yap DYH, Yung S, Chan TM. Lupus Nephritis and chronic kidney disease: a scoping review. Nephrology (Carlton) 2025;30:e14427. doi: 10.1111/nep.14427. [DOI] [PubMed] [Google Scholar]
- 5.Tselios K, Gladman DD, Su J, Urowitz MB. Advanced chronic kidney disease in lupus nephritis: is dialysis inevitable? J Rheumatol. 2020;47:1366–1373. doi: 10.3899/jrheum.191064. [DOI] [PubMed] [Google Scholar]
- 6.Kawazoe M, Nanki T. Comparison of efficacy of continuous mycophenolate mofetil with sequential cyclophosphamide and tacrolimus as maintenance therapy for lupus nephritis. Lupus. 2024;33:319–327. doi: 10.1177/09612033241228177. [DOI] [PubMed] [Google Scholar]
- 7.Atisha-Fregoso Y, Malkiel S, Harris KM, Byron M, Ding L, Kanaparthi S, Barry WT, Gao W, Ryker K, Tosta P, Askanase AD, Boackle SA, Chatham WW, Kamen DL, Karp DR, Kirou KA, Sam Lim S, Marder B, McMahon M, Parikh SV, Pendergraft WF 3rd, Podoll AS, Saxena A, Wofsy D, Diamond B, Smilek DE, Aranow C, Dall’Era M. Phase II randomized trial of rituximab plus cyclophosphamide followed by belimumab for the treatment of lupus nephritis. Arthritis Rheumatol. 2021;73:121–131. doi: 10.1002/art.41466. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 8.Plüß M, Piantoni S, Tampe B, Kim AHJ, Korsten P. Belimumab for systemic lupus erythematosus - Focus on lupus nephritis. Hum Vaccin Immunother. 2022;18:2072143. doi: 10.1080/21645515.2022.2072143. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 9.de la Rubia Navarro M, Ivorra Cortés JR, Grau García E, Román Ivorra JA. Efectiveness of belimumab in the treatment of lupus nephritis: analysis of 8 cases. Med Clin (Barc) 2022;159:344–346. doi: 10.1016/j.medcli.2022.05.003. [DOI] [PubMed] [Google Scholar]
- 10.Bhat R, Tonutti A, Timilsina S, Selmi C, Gershwin ME. Perspectives on mycophenolate mofetil in the management of autoimmunity. Clin Rev Allergy Immunol. 2023;65:86–100. doi: 10.1007/s12016-023-08963-3. [DOI] [PubMed] [Google Scholar]
- 11.Slight-Webb S, Guthridge JM, Chakravarty EF, Chen H, Lu R, Macwana S, Bean K, Maecker HT, Utz PJ, James JA. Mycophenolate mofetil reduces STAT3 phosphorylation in systemic lupus erythematosus patients. JCI Insight. 2019;4:e124575. doi: 10.1172/jci.insight.124575. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 12.Akthar M, Nair N, Carter LM, Vital EM, Sutton E, McHugh N British Isles Lupus Assessment Group Biologics Register (BILAG BR) Consortium; MASTERPLANS Consortium. Bruce IN, Reynolds JA. Deconvolution of whole blood transcriptomics identifies changes in immune cell composition in patients with systemic lupus erythematosus (SLE) treated with mycophenolate mofetil. Arthritis Res Ther. 2023;25:111. doi: 10.1186/s13075-023-03089-5. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 13.Temmoku J, Asano T, Saito K, Matsumoto H, Fujita Y, Furuya-Yashiro M, Matsuoka N, Oda A, Tanabe H, Sato S, Shio-Yano K, Sasajima T, Kiko Y, Kobayashi H, Watanabe H, Shimabukuro M, Migita K. Effect of a multitarget therapy with prednisolone, mycophenolate mofetil, and tacrolimus in a patient with type B insulin resistance syndrome complicated by lupus nephritis. Mod Rheumatol Case Rep. 2022;6:41–46. doi: 10.1093/mrcr/rxab020. [DOI] [PubMed] [Google Scholar]
- 14.You Y, Zhou Z, Wang F, Li J, Liu H, Cheng X, Su Y, Chen X, Zheng H, Sun Y, Shi H, Hu Q, Xu J, Teng J, Yang C, Ye J. Mycophenolate mofetil and new-onset systemic lupus erythematosus: a randomized clinical trial. JAMA Netw Open. 2024;7:e2432131. doi: 10.1001/jamanetworkopen.2024.32131. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 15.Yu X, Chen N, Xue J, Mok CC, Bae SC, Peng X, Chen W, Ren H, Li X, Noppakun K, Gilbride JA, Green Y, Ji B, Liu C, Madan A, Okily M, Tang CH, Roth DA. Efficacy and safety of belimumab in patients with lupus nephritis: subgroup analyses of a phase 3 randomized trial in the east Asian population. Am J Kidney Dis. 2023;81:294–306. e1. doi: 10.1053/j.ajkd.2022.06.013. [DOI] [PubMed] [Google Scholar]
- 16.Suszek D, Dubaj M, Bigosiński K, Dembowska A, Kaniewski M, Sielwanowska W, Skierkowski B, Dzikowska I, Sieczka J, Majdan M. Usefulness in daily practice of the systemic lupus erythematosus disease activity index 2000 scale and the systemic lupus erythematosus disease activity score index for assessing the activity of systemic lupus erythematosus. Reumatologia. 2024;62:187–195. doi: 10.5114/reum.2024.141291. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 17.Fanouriakis A, Kostopoulou M, Andersen J, Aringer M, Arnaud L, Bae SC, Boletis J, Bruce IN, Cervera R, Doria A, Dörner T, Furie RA, Gladman DD, Houssiau FA, Inês LS, Jayne D, Kouloumas M, Kovács L, Mok CC, Morand EF, Moroni G, Mosca M, Mucke J, Mukhtyar CB, Nagy G, Navarra S, Parodis I, Pego-Reigosa JM, Petri M, Pons-Estel BA, Schneider M, Smolen JS, Svenungsson E, Tanaka Y, Tektonidou MG, Teng YO, Tincani A, Vital EM, van Vollenhoven RF, Wincup C, Bertsias G, Boumpas DT. EULAR recommendations for the management of systemic lupus erythematosus: 2023 update. Ann Rheum Dis. 2024;83:15–29. doi: 10.1136/ard-2023-224762. [DOI] [PubMed] [Google Scholar]
- 18.Kraaij T, Arends EJ, van Dam LS, Kamerling SWA, van Daele PLA, Bredewold OW, Ray A, Bakker JA, Scherer HU, Huizinga TJW, Rabelink TJ, van Kooten C, Teng YKO. Long-term effects of combined B-cell immunomodulation with rituximab and belimumab in severe, refractory systemic lupus erythematosus: 2-year results. Nephrol Dial Transplant. 2021;36:1474–1483. doi: 10.1093/ndt/gfaa117. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 19.Gatto M, Saccon F, Andreoli L, Bartoloni E, Benvenuti F, Bortoluzzi A, Bozzolo E, Brunetta E, Canti V, Cardinaletti P, Ceccarelli F, Ciccia F, Conti F, De Marchi G, de Paulis A, De Vita S, Emmi G, Faggioli P, Fasano S, Fredi M, Gabrielli A, Gasparotto M, Gerli R, Gerosa M, Govoni M, Gremese E, Laria A, Larosa M, Mosca M, Orsolini G, Pazzola G, Petricca L, Ramirez GA, Regola F, Rossi FW, Rossini M, Salvarani C, Scarpato S, Tani C, Tincani A, Ubiali T, Urban ML, Zen M, Doria A, Iaccarino L. Durable renal response and safety with add-on belimumab in patients with lupus nephritis in real-life setting (BeRLiSS-LN). Results from a large, nationwide, multicentric cohort. J Autoimmun. 2021;124:102729. doi: 10.1016/j.jaut.2021.102729. [DOI] [PubMed] [Google Scholar]
- 20.Sumichika Y, Yoshida S, Suzuki E, Saito K, Matsumoto H, Temmoku J, Fujita Y, Matsuoka N, Asano T, Sato S, Migita K. Real-world effectiveness of belimumab in patients with active lupus. J Clin Med. 2023;12:7627. doi: 10.3390/jcm12247627. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 21.Uppin V, Gibbons H, Troje M, Feinberg D, Webber BR, Moriarity BS, Parameswaran R. CAR-T cell targeting three receptors on autoreactive B cells for systemic lupus erythematosus therapy. J Autoimmun. 2025;151:103369. doi: 10.1016/j.jaut.2025.103369. [DOI] [PubMed] [Google Scholar]
- 22.Chong YC, Toh TB, Chan Z, Lin QXX, Thng DKH, Hooi L, Ding Z, Shuen T, Toh HC, Dan YY, Bonney GK, Zhou L, Chow P, Wang Y, Benoukraf T, Chow EK, Han W. Targeted inhibition of purine metabolism is effective in suppressing hepatocellular carcinoma progression. Hepatol Commun. 2020;4:1362–1381. doi: 10.1002/hep4.1559. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 23.Struemper H, Kurtinecz M, Edwards L, Freimuth WW, Roth DA, Stohl W. Reductions in circulating B cell subsets and immunoglobulin G levels with long-term belimumab treatment in patients with SLE. Lupus Sci Med. 2022;9:e000499. doi: 10.1136/lupus-2021-000499. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 24.Parodis I, Gomez A, Chow JW, Borg A, Lindblom J, Gatto M. Early B cell and plasma cell kinetics upon treatment initiation portend flares in systemic lupus erythematosus: a post-hoc analysis of three phase iii clinical trials of belimumab. Front Immunol. 2022;13:796508. doi: 10.3389/fimmu.2022.796508. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 25.Depascale R, Gatto M, Zen M, Saccon F, Larosa M, Zanatta E, Bindoli S, Doria A, Iaccarino L. Belimumab: a step forward in the treatment of systemic lupus erythematosus. Expert Opin Biol Ther. 2021;21:563–573. doi: 10.1080/14712598.2021.1895744. [DOI] [PubMed] [Google Scholar]
- 26.Liu D, Zhou Q, Wang D, Qu Y, Guo Q, Wen J, Yu Q, Ai J. Efficacy and safety of belimumab in systemic lupus erythematosus patients with severe lupus nephritis requiring renal replacement therapy. Lupus. 2022;31:1456–1467. doi: 10.1177/09612033221119123. [DOI] [PubMed] [Google Scholar]
- 27.Ding J, Zheng Z, Li X, Feng Y, Leng N, Wu Z, Zhu P. Urinary albumin levels are independently associated with renal lesion severity in patients with lupus nephritis and little or no proteinuria. Med Sci Monit. 2017;23:631–639. doi: 10.12659/MSM.899973. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 28.Nie P, Hu L, Li B, Lou Y, Luo M, Wang Y, Lu X, Luo P. Relationship between hyperuricemia and serositis in patients with lupus nephritis. Int Urol Nephrol. 2022;54:357–364. doi: 10.1007/s11255-021-02873-z. [DOI] [PubMed] [Google Scholar]