Background/Purpose: Belimumab (BEL), a B-cell modulator mAb that selectively inhibits soluble B-lymphocyte stimulator and reduces autoreactive B cells that drive lupus disease activity, is approved for SLE and LN in adults and children.1 While early response to BEL has been demonstrated to occur within weeks for several key clinical endpoints,2 robust real-world evidence is limited regarding the characteristics of patients who experience early improvement in SLE disease activity measures (DAM). To address this knowledge gap, we identified key predictors of early improvement in SLE DAM among patients with SLE in the US.

Methods: This retrospective, longitudinal cohort study (GSK Study 222157) used electronic health record data from the Specialty Networks rheumatology practice database. Eligible patients were aged ≥18 years, diagnosed with SLE, initiated either subcutaneous or intravenous BEL (9/1/2011–12/25/2024; defined index), and had ≥12 months of pre-index (defined the baseline period) and ≥2 months of post-index clinical activity. For the analysis of each SLE DAM, patients had ≥1 record of disease activity with a nonzero value in baseline and ≥1 record of the same DAM within 2 months post-index. Early improvement in each DAM was evaluated within 2 months post-index and defined as presence of ≥1 observation that was less than the mean baseline score (at the patient level) minus its minimal important difference (0.5×standard deviation of baseline DAM) or value of 0. Predictors of early improvement for patient pain index (PPI), Health Assessment Questionnaire Disability Index (HAQ-DI), swollen joint count (SJC), and tender joint count (TJC) were assessed separately and in ≥1 of these measures on aggregate using a least absolute shrinkage and selection operator (LASSO) regression model. Predictors assessed at baseline included age, sex, race, year of index, baseline DAM, SLE disease severity, organ damage, Quan-Charlson Comorbidity Index (QCCI), and comorbidities.

Results: Overall, 684 patients were included, 54.7% (n=374) of whom experienced early (within 2 months) improvement in ≥1 DAM on aggregate. Early improvement in PPI, HAQ-DI, SJC, and TJC was experienced by 41.2%, 32.5%, 48.7%, and 38.8% of patients, respectively (Table 1). Demographics and clinical characteristics of patients with improvement in ≥1 DAM versus those without improvement are summarized in Table 2. LASSO identified male sex (vs female) (odds ratio [OR; 95% confidence interval (CI)]: 2.25 [1.03, 5.29]), minority race (vs White) (OR [95% CI]: 1.77 [1.21, 2.60]), and baseline moderate/severe SLE (vs mild) (OR [95% CI]: 1.50 [1.08, 2.10]) as predictors of early improvement in ≥1 SLE DAM on aggregate (Table 3).

Conclusion: Greater than half of patients with SLE initiating BEL experienced early (within 2 months) improvement in burdensome dimensions of disease activity (e.g. pain and joint involvement), demonstrating the rapid therapeutic effect of BEL. Moderate/severe SLE and non-White race were predictive of early improvement, suggesting a potentially greater treatment benefit of BEL in these subgroups.Funding: GSKReferences 1GSK. Benlysta US prescribing information. 20242Fanouriakis A et al. Lupus Sci Med 2019;8;6(1):e000310

Table 1. SLE disease activity measures during the 12-month baseline period and 2 months post-BEL initiation.

*For all four SLE disease activity measures, higher values indicate greater disease activity; †for patients with multiple measurements of the same SLE disease activity during the baseline period, the mean value was used to represent the patient’s baseline level; ‡for patients with multiple SLE activity measurements 2 months post-BEL initiation, the mean value was used.

IQR, interquartile range; SD, standard deviation.

Table 2. Patient demographics and clinical characteristics by SLE disease activity improvements during the 12-month baseline period.

*SLE disease severity was identified using a previously published algorithm based on validated measures of SLE activity and the consensus of expert clinical opinion; †organ damage was identified by ≥3 outpatient diagnoses (within the same organ system) for any of the medical conditions associated with organ damage.

Table 3. LASSO-selected predictors of early improvement in SLE disease activity measures*.

*ORs and 95% CIs were estimated from a logistic regression model using only covariates selected by the LASSO procedure. The tuning parameter that results in the lowest misclassification error was chosen for the LASSO procedure; †“minority” includes American Indian/Alaskan Native, Asian, Black/African American, Native Hawaiian/Other Pacific Islander, and individuals identifying as multiple races.

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ACR Meeting Abstracts - https://acrabstracts.org/abstract/belimumab-is-associated-with-early-improvement-in-disease-activity-measures-among-patients-with-systemic-lupus-erythematosus-in-the-us/