PT2:08 Serum IgA2 anti-dsDNA as a theragnostic biomarker for low disease activity with belimumab after rituximab therapy in systemic lupus erythematosus

Objectives Selecting the right treatment for the right patient remains an elusive goal for patients with SLE. We have identified a theragnostic biomarker for response to belimumab following rituximab, IgA2 anti-DNA antibodies, from two independent clinical trials: BEAT-lupus and CALIBRATE both comparing belimumab after rituximab vs. rituximab. We further evaluated its potential as effect-modifier of response and low disease activity (LDA).Methods Treatment–response-biomarker interactions were evaluated through both conventional-statistics and Bayesian posterior-probability analysis using data from these two trials. BILAG persistent LDA is defined as no BILAG-2004 A/B scores in any organ system at 2-consecutive visits 4-weeks apart, with prednisone dose =