Abstract

Abstract Objectives This study investigated the efficacy, safety, and predictive factors of belimumab (BEL) in induction therapy for patients with proliferative lupus nephritis (LN) in real-world settings. Methods Patients with biopsy-proven ISN/RPS class III or IV LN, with or without coexisting class V LN, who underwent standard of care (SoC), glucocorticoid (GC), and either mycophenolate mofetil or cyclophosphamide treatments were included. Participants were treated with SoC (SoC group, n = 32) or BEL and SoC (BEL+SoC group, n = 30). The primary end point was complete renal response (CRR) at 52 weeks. Results Baseline patient characteristics were not significantly different between the two groups. The 52-week retention rate of BEL was 90.0%. The BEL+SoC group showed significantly higher CRR and primary efficacy renal response achievement at 52 weeks and significantly lower GC dosage, adverse events, and Systemic Lupus International Collaborating Clinics damage index scores. Multivariate analysis of CRR achievement at 52 weeks revealed that the lack of estimated glomerular filtration rate (eGFR) improvement at 4 weeks was associated with CRR failure in the SoC group. A shorter duration (cut-off of 42 days) between the start of induction therapy and addition of BEL was also related to the CRR in the BEL+SoC group. Conclusion BEL, in addition to SoC, controls disease activity, reduces GC use, and suppresses organ damage in case of proliferative LN. Earlier BEL induction within 6 weeks may help achieve CRR in treatment-resistant cases without eGFR improvement at 4 weeks after induction therapy.