Background/Purpose: Development of molecular-targeted agents is essential in treat-to-target treatment strategies for systemic lupus erythematosus (SLE). We analyzed the efficacy and safety of belimumab (BEL) in the clinical practice, focusing on SLE patients in the maintenance phase.

Methods: This study included the patients with SLE in the maintenance phase (SELENA-SLEDAI< 10, glucocorticoid (GC) dose ≤12.5 mg/day). The efficacy of BEL combined with standard-of-care (BEL+SoC group, n=100) was compared with standard-of-care (SoC group including patients using either mycophenolate mofetil or hydroxychloroquine, n=103). Selection bias was reduced to a minimum using propensity score-based inverse probability of treatment weighting (IPTW). We analyzed the trajectories of changes in GC dosage in all patients in this study using growth mixture modeling (GMM). The observation period of the study was 52 weeks.

Results: No significant difference was observed in patient characteristics between the BEL+SoC and SoC groups after adjustment by propensity score-based IPTW. Only one case of BEL discontinuation (involving drug-induced eruption) was observed, and the 52-weeks retention rate was 99% (99/100). The BEL+SoC group had significantly lower GC doses at 52 weeks compared to the SoC group (BEL+SoC group, 2.2±2.7 vs. SoC group, 4.4±3.9 mg/day, respectively, p< 0.001), but no differences in SELENA-SLEDAI, 50% hemolytic complement, and anti-double stranded DNA antibodies was observed. The BEL+SoC group had a lower rate of relapse (defined as new appearance of BILAG A1 or B2 items) compared to the SoC group (BEL+SoC group, 0.9% vs. SoC group, 6.3%, respectively, p=0.031). The incidence of ≥ Grade 2 adverse events infections, as specified by the Common Terminology Criteria for Adverse Events, was significantly lower in the BEL+SoC group compared to the SoC group before adjustment by propensity score-based IPTW (BEL+SoC group, 4.0% vs. SoC group, 17.5%, respectively, p=0.003).

The trajectory of GC dose was divided into four groups by GMM; in a group (GC-free group), GC dosage could be reduced to 0 within 6 months, without any relapse. The majority of the GC-free group (87.5%) consisted of cases with concomitant BEL administration. When multivariable logistic regression analysis was performed for all patients, the factors contributing to belonging to GC-free group was onlyBEL use (odds ratio (OR) 8.86, 95% confidence interval (CI) 2.55-30.78, p< 0.001). Next, multivariable logistic regression analysis was performed for BEL+SoC group. The patients had lower the SELELNA-SLEDAI score (OR 0. 82, 95% CI 0. 68-0.98, p=0.03) and GC doses (OR 0. 75, 95% CI 0. 59-0.98, p=0.02) were more likely to belong to GC-free group.

Conclusion: In maintenance-phase SLE, administration of BEL was able to achieve reduction of GC dose while ensuring strict control of disease activity and suppression of flare-ups.

The present study suggests that among the patients who received BEL, those with low baseline SLEDAI and GC doses could discontinue GC without relapse.

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ACR Meeting Abstracts - https://acrabstracts.org/abstract/comparison-of-belimumab-and-standard-of-care-by-inverse-probability-of-treatment-weighting-analyses-based-on-propensity-score-in-patients-with-systemic-lupus-erythematosus-in-the-maintenance-phase/