Background Corticosteroids, antimalarials, and immunossuppressants, including mycophenolate mofetil (MMF), were permitted as background standard therapy in patients participating in the belimumab BLISS-52 (NCT00424476) and BLISS-76 (NCT00410384) SLE phase 3 trials. Belimumab is a B-lymphocyte stimulator-specific inhibitor approved for treatment of SLE combined with standard therapy.

Objectives To compare SLE responder index (SRI) rates in patients treated with MMF or corticosteroids in the placebo (standard therapy alone) vs belimumab dosing groups.

Methods Post-hoc analysis examined manifestations of SLE in patients treated with MMF or corticosteroids in the placebo vs belimumab arms by reviewing baseline (BL) SELENA-SLEDAI and BILAG organ domain scores. Response rates at 52 wk were assessed by SRI.

Results 189 patients entered the trials on MMF. Patients whose BL manifestations included renal (proteinuria with MMF 26.5% vs no MMF 11.6%) or vasculitic (MMF 9.5% vs no MMF 6.2%) activity were more likely to be receiving treatment with MMF or corticosteroids. Corticosteroid use was also more frequent in patients with positive immunologic findings: low complement, corticosteroids 68.3% vs no corticosteroids 60.6%; and anti-double-stranded DNA, corticosteroids 75.7% vs no corticosteroids 68.2%. SRI rates are shown in table.

Conclusions The subset of patients treated with MMF ± corticosteroids at entry in the BLISS trials does not appear to be random. Trends of increased renal disease and vasculitis, low complement, and anti-double-stranded DNA suggest these patients represent a more active SLE population. In post-hoc analysis, addition of belimumab in patients receiving these background therapies suggests the possibility of greater benefit than in the overall population.

Disclosure of Interest M. Schneider Consultant for: GlaxoSmithKline/Human Genome Sciences, Speakers Bureau: GlaxoSmithKline/Human Genome Sciences, J. Buyon Grant/Research support from: Human Genome Sciences, Consultant for: GlaxoSmithKline/Human Genome Sciences, M. Dooley Grant/Research support from: GlaxoSmithKline/Human Genome Sciences, Consultant for: GlaxoSmithKline/Human Genome Sciences, E. Ginzler Grant/Research support from: GlaxoSmithKline/Human Genome Sciences, Consultant for: GlaxoSmithKline/Human Genome Sciences, S. Cooper Shareholder of: Human Genome Sciences, Employee of: Human Genome Sciences, Z. Zhong Shareholder of: Human Genome Sciences, Employee of: Human Genome Sciences, G. Keenan Shareholder of: Human Genome Sciences, Employee of: Human Genome Sciences, J. Merrill Consultant for: GlaxoSmithKline/Human Genome Sciences