Nusinersen and risdiplam are available in the Brazilian Unified Health System (SUS) for the treatment of spinal muscular atrophy (SMA) type 1. Onasemnogene abeparvovec, a promising gene therapy, was approved in 2020 in Brazil. Given the high cost of this therapy and its promise of a lifetime effect, the objective of this study was to evaluate the cost effectiveness of onasemnogene abeparvovec, compared with nusinersen and risdiplam, in the treatment of SMA type 1 from the perspective of SUS in different scenarios.

A Markov model was adapted from one originally developed for the USA that considers five states of health. Short-term data were obtained from pivotal clinical trials and long-term survival curves were extracted from published reports from the USA. Maintenance of motor function milestones achieved at the end of follow up in clinical trials was considered until death. Costs and quality-adjusted life-years (QALYs) were discounted at five percent per year over a baseline lifetime time horizon. Alternative scenarios were evaluated for horizons of five and ten years, with and without a discount.

Onasemnogene abeparvovec resulted in an incremental cost of BRL742,890 (USD297,156) per QALY and an increase of 3.32 QALYs in relation to the alternatives over a lifetime time horizon. In the same time horizon, but without the discount, onasemnogene abeparvovec resulted in an incremental cost-effectiveness ratio (ICER) of BRL166,539 (USD66,615) per QALY. In a five-year time horizon, considering the discount rate, the therapy resulted in an ICER of BRL12,527,667 (USD5,011,066); in ten years the ICER was BRL3,384,793 (USD1,353,917).

Since the benefits of onasemnogene abeparvovec mainly occur in the long term, decision makers need to consider the uncertainty of assumptions of sustained effectiveness in view of the high initial cost of the technology.