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

OBJECTIVE: To evaluate the efficacy, safety and predictive factors of belimumab (BEL)-based triple therapy in proliferative lupus nephritis (LN) in real-world settings. METHODS: We 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. RESULTS: 49 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