Duration of Belimumab Therapy and Timing of Initiation as Predictors of Clinical Outcomes in Childhood-Onset Systemic Lupus Erythematosus: A Real-World Retrospective Study.

INTRODUCTION

Belimumab is the only biologic approved for childhood-onset systemic lupus erythematosus (cSLE), yet evidence on the optimal timing of initiation and duration of therapy remains limited. This study aimed to evaluate the impact of belimumab treatment duration and timing of initiation on clinical outcomes in cSLE.

METHODS

This retrospective study included 182 patients with cSLE treated with belimumab at Beijing Children's Hospital between September 2015 and September 2025. Patients were stratified by timing of initiation (≤ 6 months vs. > 6 months from diagnosis) and treatment duration. Primary outcomes included childhood Lupus Low Disease Activity State (cLLDAS) and childhood Clinical Remission (cCR). In a subgroup of 95 patients with ≥ 2 years of follow-up, outcomes were compared by treatment duration (< 1 year, 1-2 years, ≥ 2 years) and by timing of initiation. Multivariable logistic regression was performed to identify independent predictors.

RESULTS

Among 182 patients (81.9% female; median age 11.2 years), the median belimumab treatment duration was 14 months (IQR 7-23.8). Among 95 patients with ≥ 2 years of follow-up, cLLDAS rates increased with treatment duration: 50.0% (n = 10), 70.7% (n = 41), and 81.8% (n = 44); cCR rates were 20.0% (n = 10), 41.5% (n = 41), and 61.4% (n = 44), respectively (P = 0.101). Early initiation (≤ 6 months) was associated with significantly higher cCR rates (74.4% vs. 30.4%, P < 0.001) and lower SLEDAI-2K scores at last follow-up (0 vs. 2, P = 0.006) despite higher baseline disease activity. Multivariable logistic regression identified treatment duration as an independent predictor of cLLDAS (OR 1.17 per month, 95% CI 1.11-1.24; P < 0.001), cCR (OR 1.15, 95% CI 1.09-1.21; P < 0.001), and glucocorticoid reduction to ≤ 7.5 mg/day (OR 1.20, 95% CI 1.13-1.27; P < 0.001). Early initiation was independently associated with higher cCR rates (OR 4.31, 95% CI 1.26-14.79; P = 0.020).

CONCLUSION

Longer belimumab treatment duration was associated with a higher likelihood of achieving favorable clinical outcomes in cSLE. Early initiation within 6 months of diagnosis was also associated with an increased probability of achieving clinical remission. These findings suggest that both sustained therapy and earlier initiation may contribute to improved disease control in cSLE.