Systematic literature review of the economic burden of spinal muscular atrophy and economic evaluations of treatments

BACKGROUND: Spinal muscular atrophy (SMA) is a rare and devastating condition for which new disease-modifying treatments have recently been approved. Given the increasing importance of economic considerations in healthcare decision-making, this review summarizes the studies assessing the cost of SMA and economic evaluations of treatments. A systematic review of the literature in PubMed and Scopus up to 15 September 2020 was conducted according to PRISMA guidelines. RESULTS: Nine studies reporting the annual cost of care of patients with SMA and six evaluations of the cost-effectiveness of SMA treatments were identified. The average annual cost of SMA1, the most frequent and severe form in which symptoms appear before the age of 6 months were similar according to the different studies, ranged from $75,047 to $196,429 per year. The yearly costs for the forms of the later-onset form, called SMA2, SMA3, and SMA4, which were usually pooled in estimates of healthcare costs, were more variable, ranging from $27,157 to $82,474. The evaluations of cost-effectiveness of treatment compared nusinersen treatment against standard of care (n = 3), two treatments (nusinersen and onasemnogene abeparvovec) against each other and no drug treatment (n = 1), nusinersen versus onasemnogene abeparvovec (n = 1), and standard of care versus nusinersen with and without newborn screening (n = 1). The incremental cost-effectiveness ratio (ICER) of nusinersen compared to standard of care in SMA1 ranged from $210,095 to $1,150,455 per quality-adjusted life years (QALY) gained and that for onasemnogene abeparvovec ranged from $32,464 to $251,403. For pre-symptomatic patients, the ICER value ranged from $206,409 to $735,519. The ICERs for later-onset forms of SMA (2, 3 and 4) were more diverse ranging from $275,943 to $8,438,049. CONCLUSION: This review confirms the substantial cost burden of standard of care for SMA patients and the high cost-effectiveness ratios of the approved drugs at the current price when delivered in post-symptomatic patients. Since few studies have been conducted so far, there is a need for further prospective and independent economic studies in pre- and post-symptomatic patients.