Background Belimumab is a biologic agent approved for the treatment of systemic lupus erythematosus (SLE). Recently, we demonstrated decreasing SLE activity during belimumab treatment in patients from three Swedish clinical settings. In the present study, we aimed to investigate the effects of belimumab on mucocutaneous and articular SLE in relation to smoking status.
Methods Sixty-two patients with active SLE treated with belimumab between 2011 and 2017 were enrolled. We assessed the mucocutaneous disease using the mucocutaneous SLEDAI-2K and the cutaneous lupus erythematous disease area and severity index (CLASI). Musculoskeletal activity was evaluated by the arthritis SLEDAI-2K descriptor and the 28-joint count.
Results At baseline, 44/62 (71.0%) patients had a mucocutaneous SLEDAI-2K score 2 or more (mean mucocutaneous SLEDAI-2K: 2.3; range 0–6; n=62). The mean baseline CLASI activity was score: 8.4 (range: 0–39; n=33). We observed decreased mucocutaneous SLEDAI-2K scores at month 6 (p<0.001) and month 12 (p<0.001) compared to baseline. CLASI activity scores also decreased from baseline to month 6 (p<0.001) and 12 (p<0.001). No significant worsening in CLASI damage scores was observed at either month 6 or 12. Patients with a baseline mucocutaneous SLEDAI-2K score 2 or more with a history of current or previous exposure to tobacco smoking (n=17) displayed a more than six times higher probability of poor response to belimumab compared to never smokers (n=22) (OR: 6.4; 95% CI: 1.5–27.4; p=0.012). We observed decreased SLEDAI-2K scores for the arthritis domain both at month 6 (p<0.001) and 12 (p<0.001). From baseline to month 6, the mean tender joints count decreased from 5.7 to 2.7 (p=0.010), and the swollen joints count from 3.6 to 0.7 (p<0.001); the decreases were sustained through month 12 (p=0.001 for both counts). No impact of smoking habits on treatment outcomes in relation to articular SLE was observed.
Conclusion In line with previous reports, belimumab treatment was effective in limiting mucocutaneous and articular symptoms in patients with SLE. A history of past or current smoking was found to reduce the efficacy of belimumab in mucocutaneous manifestations. Further survey on the impact of smoking on the efficacy of belimumab at a mechanistic level is merited.
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