Evaluating the real-world effectiveness of belimumab in patients with SLE using SLE-related laboratory values and rheumatoid arthritis-derived disease activity measures: RAPID3, swollen joint count and tender joint count

Objective To investigate the real-world impact of intravenous belimumab treatment among patients with SLE using rheumatoid arthritis-derived disease activity measures and SLE-related laboratory values. Methods This retrospective cohort study used US electronic medical record data from the United Rheumatology Normalised Integrated Community Evidence (UR-NICE) database. Adult patients with SLE who initiated intravenous belimumab between 1 January 2012 and 3 December 2019 (index), had 12 months of pre-index and 24 months of post-index clinical activity, and had ≥6 infusions of belimumab during the 24 months post-index were included. The primary outcome measure was time to first improvement of minimally important difference (MID) for Routine Assessment of Patient Index Data 3 (RAPID3), Patient Pain Index (PPI), swollen joint count, tender joint count (TJC), complement C3 and C4 and anti-double-stranded DNA antibodies during the on-treatment follow-up period of up to 24 months. The secondary outcome measure evaluated the trajectories of these outcome measures for up to 24 months of belimumab treatment. Results Of 495 patients included, between 21.0% and 52.1% had ≥1 record for each of the disease activity measures or laboratory values in the pre-index and post-index periods and were included in analyses for that measure. The proportion of patients achieving MID for each measure increased rapidly within 3 months, with continued gradual improvement throughout the remaining on-treatment period, up to 24 months. After 6 months, 52.3% and 55.3% of patients had achieved MID in RAPID3 and PPI, respectively. Outcome measure trajectories indicated improved disease activity with belimumab treatment, particularly in RAPID3, TJC and laboratory values. Conclusions In this real-world effectiveness study, belimumab therapy for SLE resulted in clinically meaningful improvements in rheumatoid arthritis-derived disease activity measures within 3 months of treatment, with patients who remained on belimumab therapy experiencing improvement even up to 24 months of observation. Data are available on reasonable request. Anonymised individual participant data and study documents can be requested for further research from .