Background and aims. To investigate baseline predictors of response to mucocutaneous and musculoskeletal manifestations in belimumab-treated patients affected with SLE.
Methods. We analyzed baseline features from a multicentric cohort of SLE patients with active disease (SLEDAI-2K>0), treated with belimumab (BeRLISS). Mucocutaneous response was defined as Cutaneous Lupus Erythematosus Disease Area and Severity Index (CLASI)=0 and musculoskeletal response as Disease Activity Score (DAS28) <2.6 or <3.2. Response was evaluated at 6, 12, 24 months and predictors were assessed with logistic regression analysis.
Results. Among patients with available CLASI records at baseline (n=318), 195 (61.3%) achieved CLASI=0 throughout a mean follow-up of 26.9 ±14.8 months. Baseline negative predictors of CLASI=0 were mucocutaneous damage (CLASId, OR: 0.63 95%CI 044-090, p 0.011), disease duration before belimumab treatment (OR 0.89, 95%CI 0.83-0.97, p 0.005) and anti-SSB antibodies (OR 0.15, 95% CI 0.04-0.61, p 0.008). Consistently, anti-SSB antibodies negatively predicted mucocutaneous response at all timepoints (p<0.01 for all) while CLASId >1 was an independent negative predictor at 6 and 12 months (p<0.001 for both). Among 328 patients with DAS28 records at baseline, increased baseline SLE-Damage Index was negatively associated with DAS28<2.6 or <3.2 at 12 months (p<0.01 for both). Among patients with both mucocutaneous and musculoskeletal involvement at baseline (n=231), positive anti-SSB and disease duration negatively predicted response in both domains (OR 0.93 95%CI: 0.26 0.08-0.95, p=0.025; and 0.88-0.99, p 0.024, respectively).
Positive anti-SSB, a longer disease duration and mucocutaneous damage may negatively impact musculoskeletal and mucocutaneous response to belimumab in SLE patients.