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.