The role of baseline BLyS levels and type 1 interferon-inducible gene signature status in determining belimumab response in systemic lupus erythematosus: a post hoc meta-analysis

Abstract Background Elevated B lymphocyte stimulator (BLyS) levels in patients with systemic lupus erythematosus (SLE) correlate positively with disease activity; BLyS expression is directly linked to interferon (IFN) pathway activation. This post hoc meta-analysis of BLISS-52 and BLISS-76 explored the relationship between baseline BLyS mRNA/protein levels and/or type 1 IFN-inducible gene signature (IFN-1) and responses to the BLyS-targeting monoclonal antibody belimumab in SLE. Methods In BLISS-52 and BLISS-76, patients with autoantibody-positive SLE and a SELENA-SLEDAI score ≥ 6 and receiving stable standard SLE therapy were randomised to intravenous belimumab 10 mg/kg or placebo, plus standard of care (SoC), for 52 or 76 weeks. For this post hoc meta-analysis, patients with an appropriate mRNA sample were stratified by BLyS mRNA expression (tertiles: high/medium/low; revised quantiles: high/low), IFN-1 mRNA expression (high/low) and BLyS protein level (high/low). Co-primary endpoints were correlation between baseline BLyS and IFN-1 mRNA levels and SLE Responder Index (SRI)4 response at week 52 within BLyS/IFN-1 subgroups. Secondary endpoints included time to first severe SELENA-SLEDAI Flare Index (SFI) flare. Results Of 554 patients included in this analysis, 281 had received belimumab and 273 had received placebo. Baseline BLyS and IFN-1 mRNA levels were highly correlated (Spearman’s rank correlation coefficient 0.7799; 95% confidence interval [CI] 0.7451, 0.8106; p