World first with the treatment in utero of a fetus with spinal muscular atrophy. This case, recently reported by the journal New England Journal of Medicine, is that of a little girl now two and a half years old who has not yet shown any symptoms of the disease.
This neuromuscular disorder (one in 6,000 to 10,000 cases depending on the form, approximately 120 cases per year in France) is of genetic origin and affects motor neurons, the nerve cells controlling muscle activity. It is due to a mutation in the SMN1 gene, discovered in 1995 by a team from Necker Hospital (Paris) which codes for the motor neuron survival protein essential for the normal functioning of these cells. However, in patients, this protein is missing.
A disease that can be rapidly fatal
As the parents of this little girl had already lost a first child with this condition at the age of 16 months, the couple's second pregnancy was obviously subject to very special monitoring with the performance of an amniocentesis, a puncture of amniotic fluid having confirmed the diagnosis, as specified by the press release from Saint Jude Children's Hospital (Memphis, United States) who initiated this first.
Faced with this condition, which is often rapidly fatal depending on the form, it is only since 2016 that three drugs, all of which enable the production of the motor neuron survival protein, have been developed: Spinraza, Zolgensma in 2019, presented as the most expensive in the world, and also the Évrysdi in 2021.
A medication taken daily during the last six weeks of pregnancy
As specified in the review Nature According to Dr. Finkel, the head of pediatrics, the idea for prenatal treatment actually came from the family, and the Food and Drug Administration (US health services) gave its approval for this specific case. Ultimately, Evrysdi (risdiplam), the only drug available in oral solution form, the others being injectable, was chosen. It was given to the mother every day during the last six weeks of pregnancy and the baby girl was born without symptoms of spinal muscular atrophy.
However, as stated in the publication and press release, the little girl presented at birth certain anomalies (heart malformation since resolved, asymmetry of the brain stem, associated delays in vision and overall development), all considered to have appeared early in her development, that is to say before exposure to risdiplam, and which would therefore not be, according to the authors, linked to taking the drug.
At this stage, the child will nevertheless have to continue taking the treatment. In France, the national screening program spinal muscular atrophy has been put in place but is slow to be deployed.
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