Nusinersen Treatment and Healthcare Costs in Spinal Muscular Atrophy

Abstract

Importance: Patients with severe forms of Spinal Muscular Atrophy (SMA) depend on costly supportive care interventions. Few studies have evaluated how the clinical effectiveness of nusinersen, the first FDA approved treatment for SMA, affects healthcare costs. Objective: To assess the effect of nusinersen treatment on healthcare costs in SMA I and SMA Other (SMA types II-IV). Methods: We conducted a retrospective cohort study using IBM® MarketScan® to identify patients with ≥2 SMA diagnoses ≥30 days apart and ≥30 days of follow-up after their index date. The index date for nusinersen-treated patients was their first nusinersen administration after January 2017, and follow-up ended December 2018. The index date for our historical control group was the first SMA diagnosis after January 2015 and followed through December 2016, before the approval of nusinersen. We used multivariable linear regression to estimate non-nusinersen per member per month (PMPM) costs, adjusting for age category, sex, ventilation support, feeding tube support, Charlson Comorbidity Index score, and region. Results: 194 patients with SMA I (83 treated, 111 controls) and 510 patients with SMA Other (90 treated, 420 controls) were included in the analytic sample. Nusinersen treatment was associated with a trend toward lower PMPM costs in SMA I compared to controls (-$12,144 [95% Confidence Interval (CI): -$32,123, $7,834]), and in SMA Other was significantly associated with higher healthcare costs ($4,517 [95% CI: $1,225, $7,810]). Conclusion: Nusinersen treatment may be associated with lower healthcare costs in SMA I, but in contrast appears to be associated with higher costs in SMA Other. Additional studies using larger sample sizes, reliable diagnosis of SMA subtypes, and adjustment to avoid influential confounders are needed to help clarify the impact of SMA treatments in this rare, complex, and costly disease.