Respiratory Outcomes of Spinal Muscular Atrophy Patients Receiving Nusinersen in Hong Kong

Abstract Background: Patients with spinal muscular atrophy (SMA) have significant respiratory morbidity, and their healthcare burden is high. Nusinersen, the first disease-modifying drug available for treating SMA, was administered to our patients in Hong Kong since 2018. We performed a retrospective review of the respiratory outcomes of patients who received Nusinersen at Queen Mary Hospital (QMH) between May 2018 and December 2022 using a new scoring system. Methods: All SMA patients enrolled in the expanded access program (EAP) were recruited. For the primary outcome, the QMH SMA Respiratory Score (QMR score) was used to assess the patient’s respiratory status. This was calculated at the 1st loading dose, 4th loading dose, and every maintenance dose thereafter. For the secondary outcome, forced vital capacity (FVC) was used to reflect the patient’s lung function and was determined annually. Results: Twenty-three patients with types 1–3 SMA were included, of whom all but one were symptomatic at the time of starting the treatment. By using the QMR score, Nusinersen was found not to have a statistically significant effect on respiratory outcomes in types 1–3 SMA. Two patients with type 1 SMA were started on noninvasive ventilation at 18 and 40 months of age, which was considerably later than usual. Conclusions: Our study found that there was no significant positive effect of Nusinersen on respiratory outcomes in SMA patients who were mostly symptomatic, which was consistent with previous studies. The overall “stabilization” may still be considered an improvement compared to the natural disease course.