Cost-Effectiveness of Early vs Delayed Belimumab Treatment for Systemic Lupus Erythematosus.

Importance: Belimumab is a biologic therapy for active, autoantibody-positive systemic lupus erythematosus (SLE) that has been shown to reduce disease activity, flare frequency, and glucocorticoid use, thereby preventing organ damage. Belimumab is typically reserved for refractory disease, but emerging evidence suggests earlier initiation may lead to higher response rates, greater achievement of remission or low disease activity, and further reduction in glucocorticoid use. Objective: To evaluate the economic and health-related outcomes of early vs delayed belimumab initiation for biologic-naive patients with clinically active SLE, comparing medical costs and quality-adjusted life-years (QALYs). Design, Setting, and Participants: This economic evaluation using cost-utility analysis from a US payer perspective was conducted with a Markov model with monthly cycles over a 15-year horizon and was informed by studies published from 2013 to 2025, identified through a targeted literature review. Biologic-naive adult SLE patients with active disease (SLE Disease Activity Index 2000 score >0) were included. Patients began in a pretreatment state and transitioned monthly between 5 health states: complete response (per SLE Responder Index-4 [SRI-4]), partial response, nonresponse (failure to meet SRI-4 accompanied by flare or treatment-emergent adverse event), no treatment (standard of care), and death. Exposure: Early (≤2 years of disease duration) or delayed (after failure of standard therapy) initiation of intravenous belimumab. Main Outcomes and Measures: Primary outcomes included total direct medical costs, QALYs, incremental cost-effectiveness ratio (ICER), and incremental net monetary benefit (INMB). The 95% uncertainty intervals (UIs) for incremental costs, QALYs, and INMB were calculated from the 2.5 and 97.5 percentiles of the probabilistic sensitivity analyses. Results: The modeled cohort included 1000 adults (912 female [91.2%]) with a mean (SD) age of 41 (11) years at belimumab initiation. Early initiation provided an additional 0.30 (95% UI, -0.42 to 1.39) QALYs at an incremental cost of -$126 337.12 (95% UI, -$910 010.39 to $168 383.94) per patient relative to delayed initiation, yielding a favorable ICER of -$421 123.73 per QALY. At a $50 000 per QALY threshold, the mean INMB was $141 337.12 (95% UI, -$157 997.53 to $925 019.51), with early initiation preferred in 81.3% of simulations (8125 of 10 000 simulations). Deterministic sensitivity analyses identified time horizon (INMB range, $6351.07 for a 1-year horizon to $156 497.12 for a lifetime horizon) and SRI-4 response odds ratio (INMB range, $69 741.68 for an odds ratio of 1.08 to $209 591.09 for an odds ratio of 3.47) as the most influential parameters. Conclusions and Relevance: In this economic evaluation of early vs delayed belimumab in biologic-naive patients with active SLE, early initiation was associated with improved health outcomes and reduced costs. These findings support earlier clinical adoption and reconsideration of reimbursement criteria to reflect long-term value.