Safety and Effectiveness of Intravenous Belimumab in Patients with Systemic Lupus Erythematosus in South Korea: A Multicentre, Observational, Real-World Study

Background: In South Korea, belimumab is indicated for patients with systemic lupus erythematosus (SLE), including paediatric patients aged ≥ 5 years, and for adults with lupus nephritis, based on clinical trial evidence; however, real-world data in this population remain limited. Objective: To assess the real-world safety and effectiveness of intravenous (IV) belimumab administered in patients with SLE in South Korea. Methods: This observational study (GSK Study 216984) enrolled patients with active SLE and patients with lupus nephritis across 18 South Korean institutions (July 2021–February 2023). Patients received on-label IV belimumab plus standard therapy (antimalarials, glucocorticoids and immunosuppressants). Data were collected for a minimum of 48 weeks as part of routine clinical practice (July 2021–March 2024). Safety was assessed by monitoring the incidence of adverse events (AEs), adverse drug reactions (ADRs), serious AEs (SAEs)/ADRs and AEs of special interest (including psychiatric events) and summarised descriptively. Changes in SELENA-SLEDAI scores, laboratory biomarkers and glucocorticoid dosage from baseline to week 24 or 48 were tested using the Wilcoxon signed-rank test. Results: Of 126 enrolled patients, 105 were eligible for the ≥ 48-week safety evaluation (completed ≥ 24 weeks of belimumab treatment). Patients were mostly female (91.4%, n = 96/105), with mean (SD) SLE duration of 9.9 (8.1) years; 45.7% (n = 48/105) of patients had lupus nephritis. AEs and SAEs were experienced by 66.7% (n = 70/105) and 18.1% (n = 19/105) of patients; most events were mild or moderate in severity and unlikely to be related to belimumab. ADRs were reported for 3.8% (n = 4/105) of patients, and psychiatric events for 2.9% (n = 3/105). SELENA-SLEDAI and laboratory biomarkers significantly improved, and glucocorticoid dosage significantly reduced, between baseline and weeks 24 and 48. Conclusions: This real-world study identified no new safety concerns and demonstrated effectiveness of belimumab, supporting its use in Korean patients.