Background: Multiple sclerosis (MS) is an inflammatory autoimmune disorder of the central nervous system that primarily afflicts young adults. Approximately 400,000 people in the United States are affected by MS. Although several forms of MS exist, the most common course is known as relapsing-remitting MS (RRMS), which affects about 85% of MS patients. This form of MS is characterized by relapses of neurologic symptoms followed by periods of recovery. Progression of disease can lead to increasingly severe disability. Since the introduction of immunomodulatory biologic agents, such as interferon betas and glatiramer acetate, treatment has helped to change the course of the disease. Under budgetary constraints, health services payers are challenged to differentiate the economic value of these agents for formulary selection and/or placement.
Objective: The primary objective of this analysis was to evaluate the 2-year cost-effectiveness of 4 disease modifying drugs (DMDs) used as first-line treatment of RRMS: glatiramer acetate, interferon (IFN) Beta-1a IM injection, IFN Beta-1a SC injection, and IFN Beta-1b SC injection.
Methods: An Excel-based model was developed to compare the relative effectiveness and cost components of relapses, disability progression, and DMDs in the treatment of RRMS over a 2-year time horizon. The relative risk reduction (RRR) method was used to compare reduction in relapse rates and disease progression data from pivotal randomized double-blind placebo-controlled clinical trials of the DMDs. RRRs for relapses and disability progression, respectively, were calculated as the relative difference (treatment vs. placebo) in relapse rates and disease progression rates from placebo-controlled clinical trials. These RRRs were applied to the weighted average rates of relapse and number of disability progression steps seen in the placebo arms of the pivotal studies. The evaluation was conducted from the perspective of a U.S. health care payer (only direct medical costs considered). Medical savings were calculated as costs saved due to relapses avoided and prevention in disability progression steps. In the base case analysis, we assumed 89.4% persistence, a cost per relapse of $4,682, and a cost per disability progression step of $1,788. Monthly cost of therapy was defined as wholesale acquisition cost ($0 contractual discounts and $25 patient copayment assumed in the base case analysis) plus routine monitoring costs as assessed by an expert panel. The primary economic endpoint was cost per relapse avoided. Costs and outcomes occurring in the second year were discounted 3% to bring to 2008 present values. Oneway and multiway probabilistic (Monte Carlo) sensitivity analyses were conducted on key input variables to assess their impact on cost per relapse avoided.
Results: Without DMD treatment, patients were predicted to experience 2.55 relapses and 0.44 disability progression steps over a 2-year period (discounted values). The 2-year reductions in clinical relapses for treatment with glatiramer acetate, IFN Beta-1a IM injection, IFN Beta-1a SC injection, and IFN Beta-1b were 0.66, 0.42, 0.74, and 0.70, respectively. The 2-year reductions in disability progression steps for treatment with glatiramer acetate, IFN Beta-1a IM injection, IFN Beta-1a SC injection, and IFN Beta-1b were 0.05, 0.15, 0.12, and 0.11, respectively. In the base case analysis, IFN Beta-1a SC injection, IFN Beta-1b SC injection, and glatiramer acetate had the most favorable costs per relapse avoided ($80,589; $87,061; and $88,310; respectively) and IFN Beta-1a IM injection had the least favorable cost-effectiveness ratio ($141,721 per relapse avoided). Sensitivity analyses showed that these results were robust to changes in key input parameters, such as the number of relapses and disease progression steps in untreated patients, the RRR in clinical relapse and progression rates, the rate of persistence, the average cost of relapse, and the average cost of a disease progression step.
Conclusion: This evaluation suggests that IFN Beta-1a SC injection, IFN Beta-1b SC injection, and glatiramer acetate represent the most cost-effective DMDs for the treatment of RRMS, where cost-effectiveness is defined as cost per relapse avoided, assuming that (a) the RRR in relapses and disease progression steps calculated from multiple DMD placebo-controlled clinical trials reflect real differences among DMDs over 2 years; and (b) resource unit costs derived from published sources reflect economic consequences of relapses and disease progression.