Cost effectiveness and budget impact of natalizumab in patients with relapsing multiple sclerosis

Background: Disease-modifying therapy (DMT) is the largest single-cost item that contributes to the total perpatient cost of multiple sclerosis (MS), a disabling disorder of the central nervous system. Natalizumab is the most recent DMT to be approved for the treatment of relapsing MS and may be an attractive alternative to interferon beta and glatiramer acetate (GA). Objectives: To determine from the perspective of a United States payer (1) the incremental cost effectiveness of natalizumab compared with other DMTs and (2) the budgetary impact of utilization of natalizumab for the treatment of relapsing MS. Methods: A combined cost effectiveness and budget impact model was developed. Model inputs were drug acquisition costs (wholesale acquisition cost), costs of drug administration and monitoring, costs of treating relapses, anticipated reduction in relapse rates after 2 years of therapy, and estimated market utilization of natalizumab. Outcomes included total 2-year costs of therapy per patient, costs per relapse avoided for each treatment, and overall 2-year costs to the health plan and per member per month (PMPM) costs. Drug acquisition costs are in 2008 US dollars, and all other costs were inflated to 2008 US dollars when necessary. Univariate sensitivity analyses were performed to determine the model inputs with the greatest influence on the cost per relapse avoided for natalizumab. Results: The overall 2-year cost of therapy per patient was $72 120 for natalizumab, $56 790 for intramuscular (IM) interferon beta-1a (IFN beta-1a), $56 773 for IFN beta-1b, $57 180 for GA, and $58 538 for subcutaneous (SC) IFN beta-1a. The cost per relapse avoided was lowest for natalizumab at $ 56 594, followed by $87 791 for IFN beta-1b, $ 93 306 for IM IFN beta-1a, $96 178 for SC IFN beta-1a, and $ 103 665 for GA. The incremental cost-effectiveness ratios of natalizumab relative to IM IFN beta-1a, IFN beta-1b, GA, and SC IFN beta-1a were $23 029, $24 452, $20 671, and $20 403 per additional relapse avoided, respectively. An increase in natalizumab utilization to 9% resulted in an increase of approximately $61 760 in total 2-year costs to a hypothetical health plan of 1 million members, or a $0.003 PMPM incremental cost. Univariate sensitivity analyses indicated that the model inputs with the most influence on cost per relapse avoided for natalizumab were the weighted average number of relapses before treatment and the anticipated relative relapse rate reduction. Conclusions: Natalizumab was the most cost-effective therapy as measured by total cost per relapse avoided, not withstanding a higher drug acquisition cost versus other DMTs. Entry of natalizumab to the market is likely to result in a minimal increase in health-plan costs on a PMPM basis. Limitations of the study include the use of a surrogate measure, relapse avoided, as an outcome measure; also, adverse events were not included in the model.