Background/Purpose: Belimumab (BEL), a B-cell modulator mAb that selectively inhibits soluble B-lymphocyte stimulator and reduces autoreactive B cells that drive lupus disease activity, is approved for SLE and LN in adults and children.1 Prolonged oral glucocorticoid (OGC) use can lead to organ damage, and OGC reduction is an important treatment goal in SLE. BEL has been shown to reduce OGC use in the real world; however, limited evidence exists regarding the characteristics of patients who are able to reduce OGC use with BEL. We studied OGC reduction or discontinuation within 6 months of BEL initiation in patients with SLE in US clinical practice and aimed to identify patient characteristics that may support prediction of early OGC dose reduction or discontinuation. Methods: This retrospective, longitudinal cohort study (GSK Study 222157) used health record data from the Specialty Networks rheumatology practice database. Eligible patients were aged ≥18 years, diagnosed with SLE, initiated either subcutaneous (SC) or intravenous (IV) BEL (9/1/2011–4/25/2024; defined index), had ≥12 months of pre-index (defined as baseline period) and ≥10 months of post-index clinical activity, ≥1 OGC prescription with dose information (in prednisone-equivalent units), and no OGC discontinuation during baseline. To ensure sufficient exposure, within 3 months of index prescription, SC BEL initiators were required to have ≥1 SC or ≥1 IV BEL record while IV BEL initiators were required to have ≥1 SC or ≥2 IV BEL records. OGC dose reduction by ≥50% or discontinuation (≥120 consecutive days without OGC supply) within 6 months was defined as “early” if it occurred within the first quartile of the time from index to either event calculated across all patients, using a data-driven approach. Predictors of early OGC dose reduction or discontinuation were identified using a least absolute shrinkage and selection operator (LASSO) logistic regression model. Candidate predictors included age, sex, race, year of index, SLE disease severity, organ damage, Quan-Charlson Comorbidity Index, and comorbidities. Results: Among 541 patients included in the study, approximately half (50.8%, n=275) achieved ≥50% OGC dose reduction or discontinuation within 6 months of initiating BEL. Median time to ≥50% dose reduction or discontinuation was 177 days and 25% (n=136) of patients achieved this outcome in < 2 months (57 days). Patients with early (i.e. within 57 days) OGC reduction or discontinuation were slightly older than those without (50.3 vs 48.3 years), a greater proportion had moderate (74.3% vs 66.9%) or severe (3.7% vs 2.2%) SLE, but the same proportion (9.6%) had evidence of baseline organ damage (Table 1). LASSO regression identified moderate/severe SLE at baseline (vs mild) (odds ratio [95% confidence interval]: 1.64 [1.04, 2.65]) as a predictor of early OGC dose reduction or discontinuation (Table 2). Conclusion: Among patients initiating BEL treatment for SLE, half achieved OGC discontinuation or dose reduction by ≥50% within 6 months. This outcome was achieved by 25% of patients within 2 months of BEL initiation, with this earlier benefit more likely in patients who had moderate/severe SLE.
