OBJECTIVES: Etranacogene dezaparvovec (Etranadez) is a new gene therapy for hemophilia B. This study assessed the cost-effectiveness of Etranadez compared with Factor IX (FIX), in hemophilia B patients without inhibitors eligible for prophylaxis. A special consideration in this assessment was employing a cost savings cap for the new therapy as the existing treatments come at exceptionally high costs.

METHODS: Cost and QALY projections were performed using an evidence based semi Markov model. Important assumptions included no mortality effects of the drugs and use of bleed rates and Pettersson Scores to proportionally project short term costs and QALY implications as well as model longer term consequences of bleeds on joints. The model also features projected declines in efficacy in the gene therapy and eventual discontinuation whereby patients reinitiate FIX prophylaxis. After receiving gene therapy, patients are projected to have slight QALY gains and large cost offsets due to the cost of FIX prophylaxis. Consequently, we feature a cap on cost offsets of $150,000 per year as a scenario analyses to assess a value based price.

RESULTS: Etranadez was associated with a lifetime QALY gain of 0.64 and cost savings of over $6 million in a conventional model as annual costs of Factor IX therapy exceed $700,000 per year. However, when the model is constructed to cap annual cost savings associated with the gene therapy to $150,000 per year etranadez is not found to be cost effective at a price of $3.5 million. Instead, we found a value based price would be $2,958,000 at a willingness to pay of $150,000 per QALY.

CONCLUSIONS: In considering the cost-effectiveness of Etranadez as a new therapy, special consideration should be given to the existing high costs of Factor IX and the impact of capping cost savings associated with the new therapy.