How doctors treated a genetic disorder in the womb for the first time

Here is a look at what SMA is, and how doctors treated it while the child was in the womb.

What is spinal muscular atrophy?

SMA is a debilitating genetic condition which affects motor neurons that control movement, and leads to progressive muscle weakening. “About one in every 10,000 births have some form of the condition — making it a leading genetic cause of death in infants and children,” according to a report in Nature.

The condition is caused by mutations in the survival motor neuron gene (SMN1) which causes 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,” according to a report in New Atlas.

How was SMA treated in the womb?

For the treatment, scientists used an oral drug called risdiplam, which is given to patients to slow the progression of SMA. Risdiplam is typically given to a patient soon after birth — the earlier the intervention, the better the results seem to be, according to the New Atlas report. Therefore, in the new trial, scientists decided to administer the drug before birth for the first time.

Richard Finkel, a clinical neuroscientist at St Jude Children’s Research Hospital (Tennessee) who led the study, told Nature that the idea of giving the drug in utero came from the parents, who had previously lost a child born with the disease. Through genetic testing the parents learned that their second child in the womb had no copies of the SMN1 gene, indicating a high likelihood of being born with SMA-1.

“The mother, who was 32 weeks pregnant, took Risdiplam daily for six weeks. The baby started taking the drug from roughly one week old, and will probably continue to take it for the rest of her life,” the Nature report said.

The scientists found that the girl had higher levels of the SMN protein in her bloodstream, compared to those usually born with the condition. The girl “seemed to have lower levels of nerve damage, and even after 30 months had normal muscle development with no sign of atrophy,” according to the New Atlas report.

Scientists said that the success of the trial had opened doors for larger studies to see whether the findings could be replicated.