LBA:01:38 Real world clinical outcomes of belimumab treatment in patients with systemic lupus erythematosus: a single-center retrospective observational study

Objectives To describe treatment patterns and clinical outcomes of belimumab therapy in real-world patients with SLE, including clinical and laboratory disease activity measures, over a one-year follow-up at Tel Aviv Medical Center (TLVMC).Methods A retrospective, single-center cohort study at TLVMC, including adult patients with SLE who initiated belimumab between January 2016 -July 2025. Data were collected at baseline and follow-up visits at 6 and 12 months. The primary outcome was the proportion of patients in remission and low disease activity. Secondary outcomes included changes in Systemic Lupus Erythematosus Disease Activity Index-2K (SLEDAI-2K) scores, prednisone use, serological parameters, renal-specific outcomes, adverse events and belimumab drug persistence.Results Eighty-six patients were included (92% female, disease duration at treatment initiation 14.11 years) ( table 1). At 12 months, 48% achieved adapted DORIS remission compared with 16% at baseline (p = 0.00001), and 59% achieved adapted LLDAS compared with 29% at baseline (p = 0.00004) (figure 1a). Mean SLEDAI-2K declined from 6.2 to 3.8 (p = 0.00003), and average daily prednisone decreased from 8.2 mg to 4.2 mg (p = 0.00002) (figure 1b). In patients with LN (n=31), protein excretion >700 mg/day decreased from 50% to 32% (p = 0.0625), with a stable mean eGFR (101 ml/min/1.73 m2). In a subgroup of 8 patients (9.3%) who were unable to receive HCQ, improvements across these outcomes were comparable to those observed in patients treated with both HCQ and belimumab. Median drug persistence was 349 weeks (95% CI 233.4–NE); 31 patients discontinued treatment, with a mean time of 95.4±109.3 weeks, most often due to perceived lack of efficacy. Adverse events were infrequent, with mild infections being the most common (n=24).Abstract LBA:01:38 Figure 1Abstract LBA: 01:38 Table 1Demographic and clinical characteristics of SLE patientsConclusions In this real-world cohort, belimumab treatment was associated with significant improvements in disease activity, reduced glucocorticoid use, and favorable safety and persistence profiles. Notably, in 9.3% of patients, belimumab monotherapy was as effective as combination therapy with HCQ, suggesting that belimumab may be a feasible alternative for patients unable to take HCQ. While the absence of a control group limits causal inference, the consistency of these findings with prior studies supports the use of belimumab in routine clinical practice.