Efficacy and safety of salbutamol in treatment of children with later-onset spinal muscular atrophy.

Objectives: To investigate the clinical efficacy and safety of salbutamol in the treatment of children with later-onset spinal muscular atrophy (SMA).

Methods: This study is a prospective single-arm phase Ⅲ clinical study. Pediatric patients with SMA type Ⅱ and Ⅲ who visited Department of Neurology, Children's Hospital, Zhejiang University School of Medicine from December 2020 to June 2022 were enrolled. All patients were evaluated with motor function scales, pulmonary function test and drug safety before study. Patients were treated with salbutamol tablets orally, with an initial dose of 1 mg (tid). If tolerable, the dose was increased to 1.5 mg (tid) in the second week, then increased to 2 mg (tid) from the third week and maintained for 6 months. Patients were followed up at 1, 3 and 6 months of treatment.

Results: Twenty-six patients were enrolled, including 10 boys and 16 girls. There were 16 cases of SMA type Ⅱ and 10 cases of type Ⅲ with age at treatment initiation of 5.67 (3.13, 7.02) years and disease duration of 2.54 (1.31, 4.71) years. The Hammersmith Functional Motor Scale-Expanded (HFMSE) scores were increased from 14.0 (6.5, 43.0) before treatment to 26.0 (15.0, 46.5) after treatment (Z=－4.144, P<0.01) in 25 cases. The Revised Upper Limb Module Scale scores were increased from 33.0 (25.5, 36.0) before treatment to 35.0 (31.0, 36.5) after treatment (Z=－2.214, P<0.05) in 9 cases. In 7 ambulant children with SMA type Ⅲ, the six minutes walking distance was increased by 30 (15, 52) m after a 6-month treatment (Z=－2.366, P<0.05). Compared with the baseline pulmonary functions the patients showed a significant increase in forced vital capacity (FVC), forced expiratory volume in one second (FEV₁), and peak expiratory flow (PEF) in 15 cases after treatment (all P<0.05). According to patients and caregivers subjective reporting, there were various degrees of improvement in coughing, sputum production ability and exercise endurance. No serious adverse events were observed during the study.

Conclusions: Short-term oral administration of salbutamol may improve motor and pulmonary functions in later-onset SMA children with good safety.