A breakthrough effect of gene replacement therapy on respiratory outcomes in children with spinal muscular atrophy

Spinal muscular atrophy (SMA) is an inherited progressive neuromuscular disorder characterized by generalized hypotonia, respiratory failure and early death. The introduction of gene replacement therapy (GRT) modified the natural history of the disease. However, more data is needed to understand the long-term effect of GRT on measurable respiratory outcomes. We report the respiratory outcomes in our cohort of patients with SMA post-GRT in 2-year period.

A retrospective chart-review of genetically confirmed children with SMA who received GRT between 2019 and 2021 in Qatar. The evaluated respiratory outcomes were chronic respiratory support, respiratory hospitalizations, escalation of respiratory support and polysomnography results before and after GRT. Nonrespiratory outcomes; nutritional status, swallowing, and motor functions; were also assessed.

A total of 11 patients (9 patients with SMA-1 and 2 patients with SMA-2) received GRT at a median age of 12 months and 22 months in patients with SMA-1 and SMA-2, respectively. All patients were successfully weaned off Noninvasive ventilation (NIV) except one patient who remained on mechanical ventilation through tracheostomy tube. The annualized hospitalization rate dropped by half after GRT. The average length of stay (LOS) in intensive care unit (ICU) decreased by 17.32 days/patient/year after GRT. Duration of required escalation of respiratory support during acute hospitalizations has dropped by 18.56 days/patient/year post-GRT.

We report favorable respiratory outcomes of GRT in our cohort. GRT resulted in discontinuation of chronic respiratory support in majority of ventilated patients. GRT also resulted in decreased respiratory hospitalization rate, hospital-LOS, ICU-LOS, and need for escalation of ventilatory support.