Spinal muscular atrophy type 3 and treatment adherence in a changing therapeutic landscape: a national-center...

To report on treatment outcomes in adult patients with spinal muscular atrophy type 3 (SMA3) who had their nusinersen treatment initiated in adulthood.

The study enrolled 11 adults treated with nusinersen for SMA3 at the Croatian National Referral Centre for Neuromuscular Disorders from 2019 to 2022. We prospectively collected validated SMA outcome measures: Revised Hammersmith score (RHS), Revised Upper Limb Module, and 6-minute walk test (6MWT) as motor function outcomes and the Individualized Neuromuscular Quality of Life questionnaire. Baseline outcomes were compared with the outcomes after three years of treatment.

All patients reported subjective improvement, and 9/11 reported an increased quality of life. Overall, 10/11 patients experienced clinically significant improvement in at least one measured outcome, while the remaining 1 patient reported the absence of disease progression. The mean increase in RHS was 2.7 points (P=0.062), and the mean increase in 6MWT was 39.7 m (P=0.239). Younger age and shorter disease duration correlated with better treatment outcomes (r=-0.543 and r=-0.666, respectively). After the approval of risdiplam in 2022, a third of patients chose to switch therapies despite observed subjective and objective positive nusinersen treatment effects.

Nusinersen had a positive treatment effect despite missed doses during the COVID-19 pandemic. Although the most significant improvements can be expected in patients treated the earliest, nusinersen treatment can be beneficial even in long-standing SMA.