Cost-effectiveness Analysis of Treatment Sequence Initiating With Etanercept Compared With Leflunomide in Rheumatoid Arthritis: Impact of Reduced Etanercept Cost With Patent Expiration in South Korea

Purpose In south Korea, the price of biologics has been decreasing owing to patent expiration and the availability of biosimilars. This study evaluated the cost-effectiveness of a treatment strategy initiated with etanercept (ETN) compared with leflunomide (LFN) after a 30% reduction in the medication cost of ETN in patients with active rheumatoid arthritis (RA) with an inadequate response to methotrexate (MTX-IR). Methods A cohort-based Markov model was designed to evaluate the lifetime cost-effectiveness of treatment sequence initiated with ETN (A) compared with 2 sequences initiated with LFN: LFN-ETN sequence (B) and LFN sequence (C). Patients transited through the treatment sequences, which consisted of sequential biologics and palliative therapy, based on American College of Rheumatology (ACR) responses and the probability of discontinuation. A systematic literature review and a network meta-analysis were conducted to estimate ACR responses to ETN and LFN. Utility was estimated by mapping an equation for converting the Health Assessment Questionnaire-Disability Index score to utility weight. The costs comprised medications, outpatient visits, administration, dispensing, monitoring, palliative therapy, and treatment for adverse events. A subanalysis was conducted to identify the influence of the ETN price reduction compared with the unreduced price, and sensitivity analyses explored the uncertainty of model parameters and assumptions. Findings The ETN sequence (A) was associated with higher costs and a gain in quality-adjusted life years (QALYs) compared with both sequences initiated with LFN (B, C) throughout the lifetime of patients with RA and MTX-IR. The incremental cost-effectiveness ratio (ICER) for strategy A versus B was ₩13,965,825 (US$1726) per QALY and that for strategy A versus C was ₩9,587,983 (US$8050) per QALY. The results indicated that strategy A was cost-effective based on the commonly cited ICER threshold of ₩20,000,000 (US$16,793) per QALY in South Korea. The robustness of the base-case analysis was confirmed using sensitivity analyses. When the unreduced medication cost of ETN was applied in a subanalysis, the ICER for strategy A versus B was ₩20,909,572 (US$17,556) per QALY and that for strategy A versus C was ₩22,334,713 (US$18,753) per QALY. Implications This study indicated that a treatment strategy initiated with ETN was more cost-effective in patients with active RA and MTX-IR than 2 sequences initiated with LFN. The results also indicate that the reduced price of ETN affected the cost-effectiveness associated with its earlier use.