A new therapeutic approach for spinal muscular atrophy is demonstrated in a mouse model in this week's Nature Biotechnology. Although further research is needed to determine whether the approach will be viable in human infants, the results are considered promising by spinal muscular atrophy experts.
Spinal muscular atrophy, a genetic disorder of infants, is caused by reduced function of the 'survival motor neuron' protein in nerve cells and leads to progressive muscle weakness and early death. Brian Kaspar and colleagues previously showed that a gene can be delivered to spinal motor nerve cells in newborn mice simply by injecting a specific engineered virus carrying the gene into the blood. Now, working with spinal muscular atrophy researcher Arthur Burghes, the Kaspar team has used the engineered virus to deliver the survival motor neuron gene to a strain of mouse that is used as a model of spinal muscular atrophy. Without treatment, these mice die within about 15 days, and previous experimental therapies had increased their survival to only about 45 days. In contrast, the new gene therapy outlined in this paper kept the mice alive for more than 250 days and substantially improved their muscle function.
As a first step in evaluating whether this approach could be translated to human infants, the authors injected the engineered virus carrying a fluorescent 'reporter' gene ― which is easy to track ― into a newborn cynomolgus monkey. They found that the fluorescent gene was successfully delivered to spinal motor nerve cells, suggesting that the therapy could work in non-human primates and, possibly, in humans.