The cost-effectiveness of gene therapy for severe hemophilia B: a microsimulation study from the United States perspective

Abstract

Adeno-associated virus (AAV)-mediated gene therapy is a novel treatment promising to reduce morbidity associated with hemophilia. Although multiple clinical trials continue to evaluate efficacy and safety, limited cost-effectiveness data have been published. This study compared the potential cost-effectiveness of AAV-mediated factor IX (FIX)-Padua gene therapy for patients with severe hemophilia B in the United States vs on-demand FIX replacement and primary FIX prophylaxis, using either standard or extended half-life FIX products. A microsimulation Markov model was constructed, and transition probabilities between health states and utilities were informed by using published data. Costs were aggregated by using a microcosting approach. A time horizon from 18 years old until death, from the perspective of a third-party payer in the United States, was conducted. Gene therapy was more cost-effective than both alternatives considering a $150 000/quality-adjusted life-year threshold. The price for gene therapy was assumed to be $2 000 000 in the base case scenario; however, one of the 1-way sensitivity analyses was conducted by using observed manufacturing, administration, and 5-year follow-up costs of $87 198 for AAV-mediated gene therapy vector as derived from the manufacturing facility and clinical practice at St Jude Children's Research Hospital. One-way sensitivity analyses revealed 10 of 102 scenarios in which gene therapy was not cost-effective compared with alternative treatments. Notably, gene therapy remained cost-effective in a hypothetical scenario in which we estimated that the discounted factor concentrate price was 20% of the wholesale acquisition cost in the United States. Probabilistic sensitivity analysis estimated gene therapy to be cost-effective at 92% of simulations considering a $150 000/quality-adjusted life-year threshold. In conclusion, based on detailed simulation inputs and assumptions, gene therapy was more cost-effective than on-demand treatment and prophylaxis for patients with severe hemophilia B.