Application of SLE-DAS to assess subcutaneous belimumab efficacy in a cohort of systemic lupus erythematosus patients

Objective. To assess the efficacy of subcutaneous (sc) belimumab (BLM) by the application of SLE-DAS in a monocentric SLE cohort. Methods. We evaluated SLE patients treated with sc BLM from March 2019. Disease activity has been assessed by SLEDAI-2k, SLE-DAS and PGA (Physician Global Assessment) in all the established time-points [baseline (T0), after 1 (T1), 3 (T3), 6 (T6) and 12 (T12) months]. Furthermore, we applied and compared the achievement of remission according to SLE-DAS values (SLEDAS <= 2.08 + PDN <= 5mg/daily) and DORIS definition (clinical SLEDAI2k=0 + PGA<0.5 + antimalarial treatment, PDN <= 5mg/daily, stable immunosuppressive treatment). Results. We enrolled 86 patients [M/F 5/81, median age 48 years (IQR 17.5), median disease duration 166 months (IQR 216)]. At baseline, median values of SLEDA-2k and SLE-DAS were 6 (IQR 4) and 5.77 (IQR 4.33), respectively, and they significantly correlated (r=0.719, CI 95% 0.586-0.815, p<0.0001). Median duration of treatment was 14 months (IQR 20). We found a significant reduction of SLEDAI-2k and SLE-DAS already at T1, maintained in the subsequent time-points (p<0.0001). At T12, a remission state was achieved by 60.4% of patients according to SLE-DAS definition and by 62.3% according to the DORIS definition. Both definitions of remission have demonstrated an agreement of 84%, with a Cohen's kappa equal to 0.6. Conclusion. In this study we applied SLE-DAS to assess the efficacy of sc BLM, by analysing its over-time changes and by comparing its performance with SLEDAI-2k. Indeed, our results suggest the usefulness of this new activity index in a real-life setting.