Cost-Effectiveness Analyses of Natalizumab (Tysabri®) Compared with Other Disease-Modifying Therapies for People with Highly Active Relapsing-Remitting Multiple Sclerosis in the UK

Natalizumab (Tysabri®) is a new disease-modifying therapy that has been shown to be clinically effective in patients with relapsing-remitting multiple sclerosis (RRMS) and has been licensed for use in patients with highly active RRMS (HARRMS). These patients are those who experience higher relapse rates and faster disability progression than the general RRMS population.

To estimate the cost effectiveness of natalizumab compared with interferon-ß, glatiramer acetate and best supportive care from various UK cost perspectives.

A 30-year Markov model was developed, based on previously published models for multiple sclerosis, to estimate transition between disability states and the probability of relapse within disability states. The model was parameterized with data from the UK Multiple Sclerosis (MS) Survey 2005 and data from the AFFIRM study, a 2-year multicentre, randomized, double-blind, placebo-controlled trial of natalizumab in RRMS patients. Additional data were sourced from the literature.

A UK societal cost perspective was used in the base case, with additional cost perspectives considered in the sensitivity analysis. The baseline characteristics for the patient group were taken from the patient population in the AFFIRM study (mean age 36 years, mean time since diagnosis 5 years and a mean Kurtzke Extended Disability Status Scale [EDSS] score of 2.5). The model and its parameterization were designed and developed to support a reimbursement application for natalizumab submitted to the UK National Institute for Health and Clinical Excellence (NICE). Efficacies for natalizumab and glatiramer acetate were taken from clinical trial data, and for interferon-ß from a meta-analysis of clinical trial data. Disutilities from adverse events for each comparator were also included in the model. Outcomes and costs were discounted at 3.5% per anum.

Costs for interferon-ß and glatiramer acetate were based on published prices (year 2006 values) under the UK Risk Sharing Scheme, and for natalizumab the UK NHS list price was used. Diagnostic, administration and adverse event costs were also included. The incremental cost-effectiveness ratios (ICERs) were calculated for the base case, and a probabilistic sensitivity analysis was performed to assess the probability of cost effectiveness at different willingness-to-pay thresholds.

The ICER for natalizumab compared with interferon-ß was £2300 per QALY. Compared with glatiramer acetate, it was £2000 per QALY, and compared with best supportive care it was £8200 per QALY. From a health and social care cost perspective, the ICERs were £18 700, £20 400 and £25 500 per QALY, respectively. At a willingness-to-pay threshold of £30 000 per QALY, the probability of natalizumab being cost effective against any comparator from a societal perspective was >89%.

If UK society is willing to pay more than £8200 per QALY, or Health and Social Services are willing to pay more than £26 000 per QALY, this analysis suggests that natalizumab is likely to be a cost-effective treatment for all patients with HARRMS.