US regulators have approved the first treatment for Sanfilippo syndrome type A, a rare and fatal inherited disease that gradually destroys the brains of young children. The Food and Drug Administration cleared the gene therapy, sold as Fayuvi and developed by Ultragenyx Pharmaceutical, on September 17. The approval covers pediatric patients aged 2 to 5 and gives families their first authorized medical option for a condition that previously had none. The company said it would work with treatment centers to make the therapy available.
Sanfilippo syndrome type A, also known as MPS IIIA, is caused by a missing or deficient enzyme called sulfamidase. Without it, a complex sugar molecule builds up in cells and damages the nervous system. Children with the disease typically develop normally at first, then lose speech, cognitive ability and motor skills over time. The condition is one of a group of disorders known as mucopolysaccharidoses, is sometimes described as childhood Alzheimer’s, and most patients do not survive into adulthood.
Fayuvi, known scientifically as rebisufligene etisparvovec-hopf, is given as a single one-time intravenous infusion in a medical setting. Patients begin a course of corticosteroids one day before the infusion and continue for at least eight weeks to manage the body’s response. The therapy is designed to deliver a working copy of the gene needed to produce the missing enzyme, addressing the underlying cause rather than the symptoms.
In its decision, the FDA said patients treated with the therapy maintained or improved cognitive function when compared with an untreated group drawn from historical records. The agency described that as a meaningful departure from the usual course of the disease, in which abilities plateau and then decline during a critical window of early childhood development. Regulators granted the approval based on those measures of neurological function.
Ultragenyx did not immediately disclose a price for the therapy, and gene treatments for rare diseases have often carried costs among the highest in medicine. The number of children affected by the condition is small, which shapes both the commercial market and the way such therapies are studied. Patient advocates who campaigned for years for a treatment welcomed the decision as a starting point for families facing the diagnosis. Advocacy groups said access, insurance coverage and long-term monitoring would be the next questions for families weighing the therapy.
