To evaluate the incremental cost effectiveness of rituximab in patients with rheumatoid arthritis that failed to respond adequately to tumour necrosis factor-alpha inhibitors (biologic disease-modifying antirheumatic drugs; bDMARDs). A cost-utility model has been developed to simulate the long-term incremental cost and benefits of rituximab using data from clinical trials and registries.
The model estimates the lifetime disease progression of up to 10,000 hypothetical rheumatoid arthritis (RA) patients that failed one bDMARD. It compares cost and outcomes of two treatment sequences, representing the current UK standard both with and without rituximab. The population characteristics match those of the Randomised Evaluation of Long-term Efficacy of rituximab in RA (REFLEX) phase III randomised control trial. Clinical outcomes were based on an indirect comparison of published American College of Rheumatology response rates, adjusted for differences in placebo. To estimate medical resource use, health assessment questionnaire (HAQ) scores were grouped into five categories with UK registry data informing the average cost for each category. Quality-adjusted life years (QALYs) gained were mapped from disease severity (HAQ scores).
Compared to a standard UK treatment sequence (assuming the sequential use of bDMARDs) the introduction of rituximab led to a QALY gain of 0.526 years. The incremental cost-effectiveness ratios (ICERs) based on total direct medical cost were 11,601 pounds. Adding rituximab to a treatment sequence with no sequential use of biologic generates an ICER of 14,690 pounds.
Rituximab has lower average annual treatment costs compared to other bDMARDs and is a highly cost-effective treatment option for patients who have failed to respond adequately to one bDMARD. The cost per QALY gained of rituximab falls well below commonly accepted thresholds within the UK. Potential weaknesses of the model include the paucity of data on the efficacy of bDMARDs or non-biologic DMARDs when used as second-line options; the lack of consensus about the most appropriate therapy in patients who fail all available bDMARDs; probable underestimation of the non-drug related medical costs; indirect measurement of QALY gains with rituximab therapy; and the necessity of synthesising data from a number of clinical trials with different populations and study drugs.