Early disease and low baseline damage predict response to belimumab in patients with systemic lupus erythematosus

Objective. To investigate predictors of response, remission, low disease activity (LDA), damage 3 and drug discontinuation in patients with systemic lupus erythematosus (SLE) treated with 4 belimumab. 5 Methods. We retrospectively analysed data of a multicentre cohort of SLE patients receiving 6 intravenous belimumab. Proportion of patients achieving remission, LDA and SLE Responder 7 Index-4 (SRI-4) were evaluated. SLICC damage index (SDI) was calculated yearly. Predictors of 8 outcomes were investigated by multivariate logistic regression. 9 Results. We included 466 active SLE patients from 24 Italian centres: median (range) follow-up 10 18 (1-60) months. SRI-4 was achieved by 49.2%, 61.3%, 69.7%, 69.6% and 66.7% patients at 6, 11 12, 24, 36 and 48 months. Baseline predictors of response at 6 months were SLEDAI-2K≥10 (OR 12 3.14, 95%CI 2.033-4.860) and disease duration≤2 years (OR 1.94, 95%CI 1.078-3.473); at 12 13 months SLEDAI-2K≥10 (OR 3.48, 95%CI 2.004-6.025), SDI=0 (OR 1.74, 95%CI 1.036-2.923); 14 at 24 months SLEDAI-2K≥ 10 (OR 4.25, 95%CI 2.018-8.940), disease duration ≤2 years (OR 15 3.79, 95%CI 1.039-13.52); at 36 months SLEDAI-2K≥10 (OR 14.59, 95%CI 3.54-59.79) and 16 baseline smoking (OR 0.19, 95%CI 0.039-0.69). Patients spending≥25% follow-up in remission 17 (42.9%) or ≥ 50% in LDA (66.0%) accrued significantly less damage (p=0.046 and p=0.007). 18 Baseline SDI=0 independently predicted LDA ≥50% and remission ≥25%; the lower the baseline 19 damage, the higher the probability of remission ≥ 25%. Number of previous flares negatively 20 predicted belimumab discontinuation due to inefficacy (p= 0.009) 21 Conclusions. The early use of belimumab in patients with active SLE and low baseline damage 22 predicts favourable outcomes in a real-life setting.