OBJECTIVES: Spinal muscular atrophy (SMA) is a rare, hereditary neuromuscular disorder. Children with later-onset SMA (type II or III) have limited motor abilities which vary according to disease stage and severity. The objective of this study was to construct a cost-effectiveness model and report the clinical benefits and cost offsets of nusinersen in later-onset SMA from a United States (US) third-party payer perspective.
METHODS: A deterministic cost-effectiveness Markov model was developed based on the clinical outcome measures of the CHERISH trial, natural history data, and clinical opinions. Health states were consistent with later-onset SMA and based on the World Health Organization motor development milestones and the Hammersmith Functional Motor Scale-Expanded scores. US-specific disease management costs and utility values were obtained from literature. In the base case analysis, quality adjusted life years (QALYs) and the incremental cost-effectiveness ratio (ICER) of nusinersen compared with standard of care (SOC) were reported.
RESULTS: Over a lifetime horizon of 80 years, patients treated with nusinersen compared to SOC had an estimated 0.35 discounted LYs (21.39 and 21.04, respectively) and 1.19 discounted QALYs (13.89 and 12.71, respectively). Although the ICER of nusinersen versus SOC exceeded the $500,000/QALY threshold for orphan drugs, the model reported an estimated incremental cost offset of direct disease management of $133,996 and incremental QALY benefit for caregivers of 4.08 for nusinersen-treated patients with later onset SMA compared with SOC. Nusinersen compared with SOC also resulted in an estimated higher proportion of patients achieving unaided standing and walking motor milestones (36.3% vs. 6.5%).
CONCLUSIONS: Compared with SOC, later-onset patients treated with nusinersen were reported to have incremental QALYs. The incorporation of additional long-term data generated by registries is warranted for future model updates to fully capture the long-term benefits (e.g. QALYs or motor function) among patients with later-onset SMA.
