Biological therapies for the treatment of severe psoriasis in patients with previous exposure to biological therapy: a cost-effectiveness analysis

BACKGROUND: Biologic therapies have revolutionised the care of patients with psoriasis, although they come at significant extra cost. Guidance on their use in the UK National Health Service (NHS) has so far focused on patients who are "biologic naive", yet a minority of patients have poor response and require further treatment.

OBJECTIVES: To assess the potential cost effectiveness of sequential biologic therapies in patients with psoriasis who have been exposed to previous biologic therapy.

METHODS: A two-part model with a 10-year time horizon was built to model an initial 13.5-week "trial" phase and a longer-term "treatment" period with annual Markov cycles. Psoriasis Area and Severity Index (PASI) response rates from subgroup analyses of three randomised placebo-controlled trials evaluating biologic agents were considered. A meta-analysis of these data provided probabilities of achieving PASI response (50/75/90) in the short term, and published evidence and assumptions were used to predict outcomes over the longer term. Benefits were measured in quality-adjusted life years (QALYs), and costs (2013-14) to the UK NHS included drugs, administration, monitoring, and hospitalisation. Costs and benefits were discounted 3.5 % per annum. Cost effectiveness of sequential biologic therapy was measured using an incremental cost-effectiveness ratio (ICER) compared to best supportive care (BSC). Extensive sensitivity analyses were performed to assess the impact of alternative assumptions on the results.

RESULTS: Results indicate that over 10 years, switching to a second biologic following intolerance to or failure of a first is likely to generate more QALYs than BSC, but at a higher cost. Base case results suggest the ICER of the second biologic compared to BSC is £17,681 per QALY; however, sensitivity analyses indicate that changes in the efficacy of BSC, drug costs, dropout rates, and rates of hospitalisation have a significant impact, causing the ICER to range from less than £10,000 to over £50,000 per QALY.

CONCLUSIONS: Further biologic therapy for patients with psoriasis who have previously been treated with biologic therapy may be cost effective, although there is considerable uncertainty in the results. Future studies should be designed to evaluate the clinical efficacy of biologic therapies in this subgroup with particular attention given to short-term and longer-term responses.