We sought to describe real-world outcomes in US patients with SMA aged ≥6 months treated with nusinersen monotherapy, OA monotherapy, or nusinersen switching to OA.

Disease-modifying treatments including nusinersen and OA have significantly improved SMA prognosis, but real-world data on outcomes are limited. 

We conducted a retrospective chart review. The index date was the date of monotherapy initiation or switch to OA. Outcomes were summarized descriptively for patients with available data at or before the index date and with ≥1 follow-up visit.

This interim analysis included 30 patients (11 nusinersen monotherapy; 8 OA monotherapy; 11 nusinersen switching to OA). SMA phenotypes at diagnosis were type 1 (5/11; 2/8; 9/11), type 2 (5/11; 4/8; 1/11), type 3 (1/11; 2/8; 0/11), and undetermined (0/11; 0/8; 1/11), respectively. On the index date, 9/11 patients treated with nusinersen monotherapy, 5/8 with OA monotherapy, and 7/11 switchers weighed ≥8.5 kg; one switcher had missing weight. Mean ages (±standard deviation) were 39.0±13.9, 15.8±6.0, and 17.7±7.4 months, respectively. Improvement/maintenance from index in motor milestones was achieved by 5/10, 8/8, and 7/9 patients, respectively. Mean times to initial improvement in any motor milestone (±standard error) were 7.3±3.8, 1.5±0.7, and 3.9±1.4 months, respectively. Among patients treated with nusinersen monotherapy, OA monotherapy, and switchers, 5/10, 8/8, and 6/9 achieved/maintained normal cry function, respectively. Improvement/maintenance in speech function was achieved by 7/8, 6/6, and 6/8, respectively; improvement/maintenance in any eating function was achieved by 4/8, 5/6, and 5/9, respectively.

Patients with SMA improved and/or maintained function across multiple outcomes after receiving OA at ≥6 months of age, regardless of prior nusinersen therapy. Motor milestone attainment was observed earlier for patients who received OA monotherapy (within 2 months after treatment initiation) or OA with prior nusinersen, compared with nusinersen alone, indicating rapid onset of therapeutic effect.