Have Scientists Found a Treatment for Spinal Muscular Atrophy?

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spinal muscular atrophy

Spinal muscular atrophy often leads to an inability to breathe or death. Researchers tested a new gene therapy for the disease.

Spinal muscular atrophy (SMA) is a rare condition that results in the loss of motor neurons, which control muscle function, and an eventual wasting of skeletal muscles. Spinal muscular atrophy often affects very young infants and children and although it can vary in severity, the muscles that help us breathe are the first affected. This means that while some individuals with the condition survive into adulthood with varying levels of mobility, others require a mechanical ventilator and many die from the disease. Importantly, spinal muscular atrophy is caused by a mutation in the SMN1 gene which codes for a protein that is necessary for motor neuron survival. This suggests that treating this mutation using gene therapy could restore normal function to individuals who have or who are prone to the condition.

Testing a New Gene Therapy for Spinal Muscular Atrophy

In the New England Journal of Medicine, Mendell and colleagues tested a new gene therapy designed to treat spinal muscular atrophy. The therapy consisted of injecting a specifically designed virus into patients. The virus is designed to insert an unmutated SMN1 sequence into the patient’s genes. The researchers tested this therapy on 15 patients with a form of spinal muscular atrophy that affects infants under six months of age. Each of the patients received a single dose and was evaluated for adverse effects as well as motor function over the course of twenty months. Disease progression in these patients was then compared to a historical cohort of patients who had not been treated.

Improved Motor Function

By 20 months of age, none of the patients required mechanical ventilation. All the patients had improved motor function scores after their treatment compared to their scores before treatment. Eleven patients were able to meet developmental milestones like achieving head control, rolling over, crawling, standing, walking, and speaking. No untreated patients in the historical cohort were able to achieve any of these milestones. Of5 patients who had required feeding through a tube at the start of the study, 4 were able to swallow and feed after gene therapy. The majority of patients experienced some adverse effects on liver function, which required treatment in at least some of these individuals.

The results from this trial, as well as several other gene therapy trials that have occurred recently, are extremely encouraging for the use of gene therapy to treat spinal muscular atrophy and other genetic conditions that have previously been considered untreatable or incurable. Future work must address longer-term effects and benefits of this kind of therapy.

Written by C. I. Villamil

Reference: Mendell et al. 2017. Single-Dose Gene-Replacement Therapy for Spinal Muscular Atrophy. New England J Medicine. 377(18).