Newer classes of targeted drugs for moderate to severe plaque psoriasis are more effective and more expensive than older classes, posing a difficult and potentially costly decision about whether to use them as initial targeted treatments.
To estimate the clinical and economic outcomes of initial targeted treatment for the following drugs: adalimumab, etanercept, and infliximab (TNFα inhibitors); apremilast (PDE4 inhibitor); ustekinumab (IL-12/23 inhibitor); and ixekizumab, secukinumab, and brodalumab (IL-17 inhibitors).
We developed a Markov model to simulate patient outcomes as measured by quality-adjusted life-years (QALYs) and health care costs over a 10-year period. We assumed that patients who fail initial targeted treatment either proceed to subsequent therapy or discontinue targeted treatment. Effectiveness estimates for initial treatment were defined as improvement in Psoriasis Area and Severity Index (PASI) from baseline and derived from a 2018 network meta-analysis. Wholesale acquisition drug costs were discounted by a class-specific, empirically derived rebate percentage off of 2016 costs. We conducted one-way and probabilistic sensitivity analyses to assess uncertainty in results.
The incremental benefits compared with no targeted treatment were, in descending order: ixekizumab 1.68 QALYs (95% credible range [CR] = 1.11-2.02), brodalumab 1.64 QALYs (95% CR = 1.08-1.98), secukinumab 1.51 QALYs (95% CR = 1.00-1.83), ustekinumab 1.43 QALYs (95% CR=0.94-1.74), infliximab 1.27 QALYs (95% CR = 0.89-1.55), adalimumab 1.15 QALYs (95% CR = 0.76-1.44), etanercept 0.97 QALYs (95% CR = 0.61-1.25), and apremilast 0.87 QALYs (95% CR = 0.52-1.17). Costs of care without targeted treatment totaled $66,451, and costs of targeted treatment ranged from $137,080 (apremilast) to $255,422 (ustekinumab). Probabilistic sensitivity analysis results indicated that infliximab and apremilast are likely to be the most cost-effective initial treatments at willingness-to-pay thresholds around $100,000 per QALY, while IL-17 drugs are more likely to be cost-effective at thresholds approaching $150,000 per QALY. Acquisition cost of the initial targeted drug and utility of clinical response were the most influential parameters.
Our findings suggest that initial targeted treatment with IL-17 inhibitors is the most effective treatment strategy for plaque psoriasis patients who have failed methotrexate and phototherapy. Apremilast, brodalumab, infliximab, ixekizumab, and secukinumab are cost-effective at different willingness-to-pay thresholds. Additional research is needed on whether the effectiveness of targeted agents changes when used after previously targeted agents.