Real-world experience with belimumab-based triple therapy in proliferative lupus nephritis: data from the BEL-SPAIN Registry.

objectiveTo evaluate the efficacy, safety and predictive factors of belimumab (BEL)-based triple therapy in proliferative lupus nephritis (LN) in real-world settings.

methodsWe conducted a multicentre, retrospective study including patients with proliferative LN (new-onset or relapsing) who initiated BEL within 6 months of a renal flare, in combination with standard-of-care.

results49 patients were included (mean age 37 years; 85.7% female; 67.3% Caucasian). The median time from renal flare to BEL initiation was 1 month (IQR 0-3). By 12 months, 67.3% achieved complete renal response (CRR), 75.5% primary efficacy renal response (PERR) and 83.7% at least partial renal response. Median proteinuria declined from 2.7 g/day to 0.49 g/day, with parallel improvement in estimated glomerular filtration rate (71 to 78 mL/min/1.73 m²). Patients with baseline proteinuria <3 g/day achieved significantly higher CRR (78.1% vs 47.1%; p=0.027) and PERR (84.4% vs 58.8%; p=0.048) rates.The mean glucocorticoid (GC) dose decreased from 31.7 mg/day at baseline to 3.5 mg/day at 12 months, and 26.1% of patients achieved complete GC withdrawal. Extrarenal disease activity was present in 81.6% of patients at baseline, predominantly articular and mucocutaneous, with clinically meaningful improvement in 80% during follow-up. At 12 months, 40.8% met remission by Definition Of Remission In Systemic Lupus Erythematosus (DORIS) criteria and 46.9% attained Lupus Low Disease Activity State (LLDAS). Renal treatment failure occurred in 16.3% and renal relapse in 4.1%. Adverse events were mild, and no serious BEL-related events were observed.

conclusionBEL-based triple therapy is effective and safe in proliferative LN, achieving high renal and extrarenal response rates, substantial GC-sparing and treat-to-target outcomes in real-world practice.