P128 Efficacy of intravenous belimumab in children with systemic lupus erythematosus with markers of high disease activity: across-trial comparison with adult belimumab studies

Background Belimumab is approved as add-on therapy for patients ≥5 years with active, autoantibody-positive systemic lupus erythematosus (SLE).1 The PLUTO trial (NCT01649765) demonstrated safety and efficacy of belimumab in children with SLE2 as generally consistent with adult studies. The current analysis assessed the efficacy of belimumab 10 mg/kg given intravenously (IV) to patient subgroups with baseline markers of high disease activity in PLUTO versus pooled BLISS-52 (NCT00424476) and BLISS-76 (NCT00410384) SLE trials. Methods Patients 5–17 years (PLUTO) and ≥18 years (BLISS-52 and BLISS-76) with active SLE were randomised to IV belimumab 10 mg/kg or placebo, plus standard of care (SoC) (PLUTO);2 and IV belimumab 10 mg/kg, or placebo, plus SoC (BLISS trials).3 The primary endpoint was SLE Responder Index 4 (SRI4) at Week 52. This post hoc across-trial comparison (intention-to-treat [ITT] population) investigated the treatment effect of belimumab according to baseline disease activity indicators (Safety of Estrogens in Lupus Erythematosus National Assessment-SLE Disease Activity Index [SELENA-SLEDAI] score, anti-dsDNA and complement C3/C4 levels) and steroid use; analyses were descriptive. Results In PLUTO, belimumab demonstrated higher SRI4 response versus placebo; this response was similar for patients with baseline SELENA-SLEDAI scores of ≥10 and ≤9, and for and those receiving steroids, but greater in those with scores ≥13, low anti-dsDNA, or normal/high C3/C4 (table 1). Subgroup analyses from the BLISS adult studies demonstrated similar findings with the exception of patients with high anti-dsDNA or low C3/C4 (table 1). Conclusions Subgroup analyses from the PLUTO trial demonstrated favourable belimumab responses in paediatric patients with high SELENA-SLEDAI scores, similar to those observed in adult belimumab studies. However, these results should be interpreted with caution due to the small sample size of PLUTO, the post hoc nature of the analyses and other limitations. Disclosures DLB, MO, AH, BJ, DR and HQ are employees of GSK. BJ and DLB hold stocks and shares in GSK; MO, AH, DR and HQ hold shares in GSK. Acknowledgements This study was funded by GSK. Medical writing support was provided by Gosia Carless, PhD, Fishawack Indicia Ltd, UK, and was funded by GSK. References Benlysta US prescribing information. GlaxoSmithKline; 2018. Available at: https://www.gsksource.com/pharma/content/dam/GlaxoSmithKline/US/en/Prescribing_Information/Benlysta/pdf/BENLYSTA-PI-MG-IFU-COMBINED.PDF Brunner H.I., Abud-Mendoza C., Viola D.I., Calvo I., Levy D.M., Calderon Gallegos J., et al. Efficacy and safety of intravenous belimumab in children with systemic lupus erythematosus. Arthritis Rheumatol 2018;70(59):3224–3225, Abstract 2867. van Vollenhoven R.F., Petri M.A., Cervera R., Roth D.A., Ji B.N., Kleoudis, et al. Belimumab in the treatment of systemic lupus erythematosus: high disease activity predictors of response. Ann Rheum Dis 2012; 71:1343–1349.