Real-World Data from Nusinersen Treatment for Patients with Later-Onset Spinal Muscular Atrophy: A Single Center Experience

Background: Spinal muscular atrophy (SMA) is a motor neuron disease associated with progressive muscle weakness and motor disability. Objective: This study aims to report the evaluation of nusinersen, an antisense oligonucleotide, on motor function in patients with SMA types 2 and 3. Methods: This single-center retrospective observational study assessed nusinersen therapy outcomes, measured by HSMFSE or CHOP-INTEND scales, in patients with SMA types 2 and 3, compared to untreated patients, for at least 24 months. Results: A total of 41 patients with SMA types 2 and 3 under nusinersen treatment were included. In 30 treated patients (mean age: 10.6 years; 14 with SMA type 2), the mean change in HFMSE scores was +1.47 points (SD = 0.4) and +1.60 points (SD = 0.6) after 12 and 24 months of treatment, respectively. In contrast, the control group (N= 37) (mean age: 10.2 years; 20 with SMA type 2) presented a mean change of -1.71 points (SD = 0.02) and -3.93 points (SD = 0.55) after 12 and 24 months of follow-up, respectively. The most severe patients under nusinersen treatment (N= 11) showed a change of +2.37 (SD = 1.13) on the CHOP-INTEND scale after 12 months of follow-up. Disease duration at the beginning of treatment was the main predictor of functional improvement. Despite functional gain and motor stabilization, treatment with nusinersen did not prevent the progression of scoliosis. Conclusions: Our data provide evidence for the long-term safety and efficacy of nusinersen use in the treatment of later-onset SMA, and patients with shorter disease duration showed better response to treatment.