Background Belimumab, a B-lymphocyte stimulator, was FDA-approved March 2011 for the treatment of adult patients with active, autoantibody-positive SLE receiving standard of care medications. There is a need to evaluate belimumab's effectiveness in real-world practice settings.

Objectives To describe the effectiveness of initiating belimumab treatment on flare episodes.

Methods Patients aged 18–64 years at first belimumab infusion (index date) between 01 Jan 2010 – 31 Dec 2014 were selected from the US Truven Health MarketScan® Commercial Database (study ID 204999). SLE diagnosis (ICD-9 code 710.0) was documented prior to/on index date. We included patients with complete medical and pharmacy benefits ≥6 months prior to index (baseline period). Moderate and severe SLE flare episodes were defined using previously published algorithms developed for claims data (Garris C, 2013). Incidence rates (IRs) and 95% CIs were calculated per subject for 3-month intervals, with two intervals in the baseline period and a variable number of intervals in the follow-up period. In primary “as treated” analyses, person-time spanned the duration of belimumab exposure including one month after last infusion. Sensitivity analyses were performed using “intention to treat” (ITT) analysis including all follow-up during each interval for person-time. To statistically compare the period before and after belimumab initiation, IRs were calculated in the total baseline and follow-up period per patient in both as-treated and ITT analyses, and compared using the Wilcoxon signed-rank test.

Results We identified 1835 belimumab initiators (mean age 43 years, SD 11; 94% female). SLE comorbidities in the baseline period included arthritis (46%), lupus nephritis (7%), anemia (20%), rash (27%), arthralgia (43%), and mood disorders (34%). Similarly, 15% were hospitalized and 27% had ER visits. Baseline medications included antimalarials (68%), oral corticosteroids (71%), immunosuppressants (59%), and NSAIDs (32%). Belimumab continuation rates were 81% at 6 months, 55% at year 1, 35% at year 2 and 27% at year 3 post index. There was a marked and sustained decrease in moderate/severe flare incidence following belimumab initiation (Figure 1). This pattern was similar in the ITT sensitivity analysis. The Wilcoxon signed-rank test yielded highly statistically significant results for both the primary as treated analysis and the ITT analysis (p<0.001).

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Figure 1.

Incidence rates and 95% CIs for moderate and severe SLE flares among 1835 patients initiating belimumab: six month baseline period and follow-up.

Conclusions In this large sample of SLE patients initiating belimumab, the rates of moderate/severe SLE flares during belimumab treatment were significantly lower compared with those in the pre-belimumab period. The comparative effectiveness of belimumab vs. standard of care immunosuppressants, as well as causes and effects of belimumab discontinuation should be further explored.

Acknowledgement Study funded by GSK.

Disclosure of Interest M. Stott-Miller Shareholder of: GSK shares, Employee of: GSK, P. Egger Shareholder of: GSK shares, Employee of: GSK, A. Eudy Employee of: GSK, J. Maskell Employee of: GSK, Q. Fu Shareholder of: GSK shares, Employee of: GSK, H. Kan Shareholder of: GSK shares, Employee of: former employee of GSK, R. Alfonso-Cristancho Shareholder of: GSK shares, Employee of: GSK, K. Costenbader: None declared