Nusinersen for type-III spinal muscular atrophy: a 12-month retrospective study in a Brazilian cohort

Spinal muscular atrophy (SMA) is a progressive, autosomal recessive motor neuron disorder caused by mutations in the SMN1 gene. While clinical trials in type-I and -II SMA led to the approval of nusinersen for all SMA types, evidence on its long-term efficacy and safety in type-III patients is still scarce.

The present study investigated treatment responses in SMA type-III patients subjected to nusinersen therapy.

Pediatric and adult patients with genetically confirmed 5q SMA type III on nusinersen treatment for at least 12 months were included in the current retrospective study. We collected data on demographics, genetics, nutritional status, swallowing function, and adverse events associated with nusinersen treatment. Motor function was assessed in all patients using the Hammersmith Functional Motor Scale-Expanded (HFMSE), and respiratory function was evaluated through forced vital capacity in patients aged 6 and older.

Nineteen patients (12 males; 63.2%) were included in the study. Most patients (94.7%) had a homozygous SMN1 exon 7 deletion, and 63.2% had 3 SMN2 copies. At baseline, 68.4% of patients were ambulant, 21.1% had scoliosis, and 36.8% had lower limb deformities. One patient required non-invasive ventilation, which was discontinued after treatment with nusinersen. Hammersmith Functional Motor Scale-Expanded scores improved in 94.7% of patients after 12 months of treatment, with gains of 1 to 9 points (mean 4.0 points; p < 0.001). Adverse events were mild and resolved within 24 hours.

Nusinersen was well tolerated and improved motor function in SMA type-III patients, supporting its potential benefits in real-world settings.