Background Belimumab in conjunction with mycophenolate mofetil has been proven to be effective for treating systemic lupus erythematosus (SLE) in several randomized controlled trials. Usefulness of calcineurin inhibitors has also been reported in controlling the activity of SLE. However, the safety and effectiveness of belimumab-calcineurin inhibitor combination therapy have not been addressed. Therefore, we conducted a single-center retrospective study to analyze the safety/efficacy profile of belimumab-tacrolimus (B-T) combination therapy in patients with SLE.

Methods Patients with SLE administered belimumab and tacrolimus during their treatment were included in the study, and samples collected were analyzed for the drug retention rate/SLE flare rate/infection incidence rate/glucocorticoid-sparing effect of the B-T combination therapy.

Results Thirty-three patients with SLE were treated with B-T combination therapy at our institution. Four patients discontinued the treatment because of insufficient response/adverse events. The drug retention rate was over 90% at week 52 and approximately 80% at day 1000. Only one patient developed serious infection.

The lupus low disease activity state (LLDAS) achievement ratio was 9.1% on the day of initiation and improved to 64.0% at 52 weeks after initiation.

SLE flares were observed in only three patients (9.1%) in the first 52 weeks after initiation, and in five patients (15.2%) throughout the study period. A glucocorticoid-reducing effect was also observed in patients treated with B-T combination therapy.

Conclusions In most patients with SLE, B-T combination therapy was well tolerated, and showed a good efficacy profile and glucocorticoid-reducing effect. Thus, B-T combination therapy can be a feasible option for patients with refractory lupus.