A new study suggests that children with Spinal muscular atrophy (SMA) can achieve improvements in motor function after six months of treatment with the drug nusinersen, particularly when treatment began before seven months of age.

SMA is a genetic disease that affects motor neurons in the spinal cord, resulting in muscle atrophy and widespread weakness that eventually impair swallowing and breathing. A new study conducted at IOS Press suggests that SMA should be routinely included in newborn screening for early diagnosis. SMA type 1 is the most common and also most severe subtype of SMA. After diagnosis infants with SMA type 1 rarely achieve improvements of motor function or attain motor developmental milestones.

SMA is caused by mutations in the survival motor neuron (SMN) 1 gene, which codes for survival motor neuron protein. This leads to loss of function. The SMN 1 gene is located on chromosome 5q13. Nusinersen, the first drug to be approved for SMA, is an antisense oligonucleotide which leads to increased expression of more full-length and functional SMN protein by functionally converting the SMN2 gene into the SMN1 gene. Nusinersen is injected into the spinal canal to allow it to distribute to the central nervous system.

Among these, nusinersen is the first drug specifically approved to treat SMA. Prior to approval in Europe, nusinersen was provided to patients with SMA type 1 within an Expanded Access Program (EAP). During the study, patients ranged in age from a few months to almost eight years. Symptoms generally appeared within the first three months of life and most babies were diagnosed before six months of age. Prior to treatment, more than half of the children required ventilation support.

Greater improvements were seen in children who began treatment at seven months or younger compared to those who started treatment after seven months. The findings of this study added to the increasing body of evidence that early diagnosis and initiation of treatment are fundamental for patients with infantile-onset spinal muscular atrophy highlighting the importance of the implementation of a newborn screening. The findings appeared in the Journal of Neuromuscular Diseases.