Background Disease modification is an important concept for minimizing disease activity with the fewest treatment-associated toxicities when managing SLE . Belimumab has been used as a maintenance therapy for SLE; however, data on its disease-modifying effects are scarce. Therefore, we aimed to investigate the disease-modifying effects of belimumab in SLE patients.

Methods This single-centre retrospective cohort study included SLE patients treated with belimumab at our institution. We analysed the changes in flare-free ratio, lupus low disease activity state (LLDAS) achievement ratio, glucocorticoid dosage, SLICC/ACR damage index (SDI) score, and drug retention rate after belimumab initiation.

Results Of the 567 patients with SLE followed up in our hospital, 95 used belimumab and to 92 were included in the study.

Fifty-two weeks after initiating belimumab, the flare rate decreased (82.6% to 14.1%) (p<0.01). At week 52 and day 1,000 after initiation of belimumab, >70% and approximately 90% of the patients achieved LLDAS, respectively. Belimumab administration also significantly decreased glucocorticoid demands, and at the end of the study period, 68.5% of patients achieved prednisolone ≤5 mg/day and 22.8% achieved glucocorticoid discontinuation. Furthermore, most patients were free of SDI progression (week 52, ±95%; end of study period, almost 90%), and belimumab showed a high drug retention rate (week 52, 90%; day 1000 after initiation >80% ).

Conclusions Most patients on belimumab achieved LLDAS, decreased flare rate and glucocorticoid demand, and a stable trend of SDI after its induction. Furthermore, belimumab had a high drug retention rate. Therefore, the introduction of belimumab may be a key element in disease modification.