Spinal muscular atrophy (SMA) is a debilitating genetic condition that’s usually fatal by a few years of age. But an intriguing case study might demonstrate a simple new treatment, with a child showing no signs at all two and a half years after birth.
SMA is caused by mutations in a gene called SMN1, which results in a deficiency of a protein crucial for the survival of motor neurons in the spinal cord. This prevents muscles from receiving signals from the brain, causing them to waste away. In its most severe form, SMA-1, motor skills decline rapidly and patients usually only live two to three years.
An oral drug called risdiplam is given to patients to slow progression of the disease, and it has been shown to improve survival and motor function. However, it’s far from a cure, with some symptoms and deaths still occurring.
Treatment with risdiplam is usually started soon after birth, and the earlier the intervention, the better the results seem to be. So in the new trial, the drug was administered before birth for the first time.
The parents were both known carriers of SMN1 gene mutations that raised the risk of SMA, and sadly had previously had a child born with the disease who died at 16 months of age. Genetic testing of their second child in the womb revealed that it had no copies of the SMN1 gene, indicating a high likelihood of being born with SMA-1.
As part of the trial, researchers from St. Jude Children’s Research Hospital had the mother herself take risdiplam daily for the last six weeks of pregnancy. After birth, the baby was given the drug from one week old, and will likely need to take it for the rest of her life.
The scientists found that the child had higher levels of the SMN protein in their bloodstream, compared to babies normally born with the condition. They seemed to have lower levels of nerve damage, and even after 30 months had normal muscle development with no sign of atrophy.
“During the course of the assessment, we really have seen no indication of any signs of SMA,” said Richard Finkel, corresponding author of the study.
Of course, the results of a trial involving one single patient doesn’t mean that the technique will work for everyone, but the team says that it does lay the groundwork for larger-scale studies.
“Our primary objectives were feasibility, safety and tolerability, so we’re very pleased to see that the parent and child are doing well,” said Finkel. “The results suggest it would be worthwhile to continue investigating the use of prenatal intervention for SMA.”
The research was published in the New England Journal of Medicine.