OBJECTIVES: The treatment landscape for spinal muscular atrophy type 1 (SMA1), a severe, rapidly progressing genetic neuromuscular disease, has evolved in recent years. However, data on the economic burden of SMA1 since FDA approval of the first effective disease-modifying therapy (nusinersen, 12/23/2016) are limited. We previously conducted a retrospective evaluation of healthcare resource utilization (HCRU) and costs in patients with SMA1, overall and following nusinersen initiation; however, this study was limited by short follow-up duration (median, 7.9 months). Here, we expand these findings with additional/updated observations and greater follow-up. METHODS: Patients with SMA1 were identified in Symphony Health's Integrated Dataverse^® (09/01/2016–08/31/2019). HCRU was assessed from the index date (first SMA diagnosis date after 12/23/2016) until the last date of clinical activity or end of available data. For nusinersen-treated patients, HCRU was also assessed following treatment initiation. RESULTS: We identified 449 patients with SMA1 (55.2% female; median follow-up, 12.4 months). Patients with SMA1 overall and nusinersen-treated patients (n=59) averaged, respectively, 50.6 vs. 46.8 days with medical visits/year (inpatient, 8.2 vs. 4.7; respiratory failure–related, 9.5 vs. 7.4). All of these values, with the exception of average inpatient days/year among nusinersen-treated patients, are lower compared with our earlier analysis. HCRU is expected to translate into substantial healthcare costs, both overall and in nusinersen-treated patients. Updated cost data available at the time of the conference will be presented. An important limitation is that, while >59 patients may have received nusinersen, HCRU could only accurately be assessed among patients with recorded nusinersen-associated procedures or drug codes. CONCLUSIONS: When evaluated over a longer follow-up period, HCRU was generally lower than previously estimated, suggesting that the burden of SMA1 may be higher around date of diagnosis. Nonetheless, results indicate that the burden associated with SMA1 remains substantial, including among patients receiving ongoing disease-modifying therapy. FUNDING: AveXis, Inc., a Novartis company.