Objectives To analyze the effectiveness and safety of Belimumab in SLE patients with data from a Real-World cohort.

Methods A single center observational study was performed including SLE patients who had initiated treatment with Belimumab from September 2017 to January 2023. Demographic, clinical, laboratory, effectiveness and safety variables were collected. Effectiveness was evaluated according to changes from the baseline in SLEDAI-2K and disease activity markers (proteinuria, complement consumption and/or Anti DNAds). Safety data was collected including any adverse event (AE) due to any cause. AE was considered serious (SAE) if it was life-threatening or result in hospitalization, disability or in death.

Results Overall, 15 patients were included in the study, whose baseline characteristics are exposed in the table 1. Nine patients were still receiving the drug with a mean drug survival of 15.6 months. Belimumab allowed steroid tapering in all cases, but treatment was discontinued just in 1 patient (7%). Treatment also improved disease activity markers in all (100%) patients. Belimumab was well tolerated, and the AE reported were infection (14 events) and malaise in 1 patient. In 11 cases, infection was mild (9 upper respiratory tract infection, 1 urinary tract infection and 1 gastroenteritis). 3 severe infections were registered (1 pneumonia, 1 pyelonephritis and 1 meningitis).

Regarding LN patients, treatment exposure achieved was 10.85 patients/year. Renal Biopsy demonstrated class III in a patient (20%) and class IV in 4 patients (80%). Mean proteinuria at baseline was 6.66g/24h. In 3 cases, Belimumab was started in the first 6 months after LN diagnosis was established. In 4 cases (80%), Belimumab addition allowed significant reduction of proteinuria and corticosteroids. In 2 out 5 (40%) treatment was discontinued, one case due to an insufficient response and in the other, to a SAE (Cryptococcus neoformans meningitis).

Conclusion Belimumab maintained an acceptable safety profile and an adequate effectiveness. Intravenous and subcutaneous formulations showed similar performance. Belimumab addition resulted in reduction in proteinuria and corticosteroid use.