Comparative analysis of long-term organ damage in patients with systemic lupus erythematosus using belimumab versus standard therapy: a post hoc longitudinal study.

OBJECTIVE: Long-term extension (LTE) studies of belimumab in SLE do not include a comparator arm, preventing comparisons between belimumab plus standard therapy and standard therapy alone for organ damage accrual. Propensity score matching can be used to match belimumab-treated patients from LTE studies with standard therapy-treated patients from observational cohort studies. This analysis was designed to compare organ damage progression between treatment groups (belimumab plus standard therapy vs standard therapy alone) in patients with SLE with ≥5 years of follow-up, reproducing our previous study with more generalisable data. METHODS: This exploratory post hoc analysis used a heterogeneous population of US and non-US patients receiving monthly intravenous belimumab from pooled BLISS LTE trials (BEL112234/NCT00712933) and standard therapy-treated patients from the Toronto Lupus Cohort. Sixteen clinical variables were selected to calculate the propensity score. RESULTS: The 592 LTE and 381 Toronto Lupus Cohort patients were highly dissimilar across the 16 variables; an adequately balanced sample of 181 LTE and 181 matched Toronto Lupus Cohort patients (mean bias=3.7%) was created using propensity score matching. Belimumab treatment was associated with a smaller increase in Systemic Lupus International Collaborating Clinics/American College of Rheumatology Damage Index (SDI) over 5 years than standard therapy alone (mean treatment difference=-0.453 (95% CI -0.646 to -0.260); p<0.001). Patients treated with belimumab were 60% less likely to progress to a higher SDI score over any given year of follow-up, compared with standard therapy alone (HR (95% CI) 0.397 (0.275 to 0.572); p<0.001). CONCLUSION: Using propensity score matching, this highly heterogeneous sample was sufficiently matched to the Toronto Lupus Cohort, suggesting that patients treated with intravenous belimumab may have reduced organ damage progression versus standard therapy alone. This analysis of a large and diverse pooled SLE population was consistent with our previously published US-focused study.