Cost-effectiveness of caplacizumab in immune thrombotic thrombocytopenic purpura in the United States.

Background: Immune thrombotic thrombocytopenic purpura (iTTP) is a rare, life-threatening thrombotic microangiopathy. Caplacizumab is the only treatment approved by the European Medicines Agency and the US Food and Drug Administration for iTTP, to be given in combination with plasma exchange therapy (PEX) and immunosuppression (IS). The National Institute for Health and Care Excellence's independent appraisal committee assessed the cost-effectiveness of caplacizumab and concluded that the addition of caplacizumab to PEX+IS is cost-effective under a patient access scheme in the United Kingdom.

Objective: To assess the cost-effectiveness of caplacizumab in iTTP from the US payer perspective.

Methods: The National Institute for Health and Care Excellence's model was adapted to the US setting using US costs and discount rates. In contrast to previous cost-effectiveness analyses that accounted only for acute outcomes, our model consisted of a 3-month decision tree for an acute iTTP episode, followed by a Markov model to project long-term costs and outcomes (time horizon: up to 55 years; 3-monthly cycles).

Results: Patients taking caplacizumab with PEX+IS experienced an incremental gain of 2.96 life years (LYs) and 1.75 quality-adjusted LYs relative to PEX+IS alone, at an increased lifetime cost of $256,000. The incremental cost-effectiveness ratio was $86,400 per LY and $146,300 per quality-adjusted LY gained.

Conclusions: Considering willingness-to-pay thresholds of $150,000 to $200,000, the addition of caplacizumab to PEX+IS may be cost-effective compared with PEX+IS alone for the treatment of iTTP in a US setting.