Purpose Belimumab (BEL) is approved for Systemic Lupus erythematosus in addition to standard immunosuppressive therapies. Clinical studies have excluded patients with particular organ manifestations from participation in most clinical trials. Most importantly, Lupus nephritis (LN) and neuropsychiatric Systemic Lupus erythematosus (NPSLE) were exclusion criteria in the relevant clinical studies. We aim to report our experience of BEL’s effect on SLE manifestations which have not been formally addressed in clinical trials.

Methods We performed an observational study of routinely collected clinical data of all patients receiving BEL with or without other immunosuppressive therapy at our institution.

Results We identified 15 patients currently receiving BEL therapy. Of these, 9 were not analysed further because they had no history of LN or NPSLE.

One 48-y/o female patient after renal transplantation with background therapy consisting of prednisone (GC), hydroxychloroquine (HCQ), leflunomide (LEF) and tacrolimus (TAC) had a stable disease but no additional benefit (BEL stopped after 5 months). Three female patients with GC, HCQ and mycophenolate mofetil (MMF) had an improvement of proteinuria, steroid dosage and overall quality of life. One female patient is receiving BEL or placebo (PBO) during a clinical trial (BLISS-LN), she has markedly improved proteinuria with GC, HCQ, MMF and BEL/PBO. One 73-y/o male patient with NPSLE who failed or could not tolerate various standard and additional therapies (including Rituximab and Cyclophosphamide) had a persistent clinical improvement of cutaneous lupus and neuropsychiatric symptoms (dysarthria, concentration, ataxia) after the second BEL infusion. Overall, there was one upper respiratory tract infection but no other adverse events.

Conclusions In the six patients analysed, 3 had improved proteinuria, 1 had stable disease after renal transplantation, 1 improved regarding NPSLE symptoms and 1 had improved proteinuria, but in the last case, it is not yet clear whether the effect is due to BEL. Overall, while the results of the BLISS-LN trial are awaited, we experienced improved Lupus nephritis with BEL in addition to standard therapy and observed one case of improved NPSLE. While BEL has not been approved for these severe organ manifestations, it still might be effective in well-selected patients.