WASHINGTON, D.C. — The U.S. Food and Drug Administration approved Fayuvi, a one-time gene therapy from Ultragenyx Pharmaceutical Inc., as the first treatment for children with mucopolysaccharidosis type IIIA, providing an option designed to alter the course of a rare inherited disease previously managed only through its symptoms.
Fayuvi, or rebisufligene etisparvovec-hopf, is administered as a single intravenous infusion. The therapy uses a modified, non-infectious adeno-associated virus serotype 9, or AAV9, to deliver a functioning copy of the SGSH gene into a patient’s cells.
MPS IIIA, also known as Sanfilippo syndrome type A, progressively damages the brain and nervous system. Children with the disease lose cognitive, language and other developmental abilities over time.
The genetic defect causes patients to lack sufficient sulfamidase, an enzyme needed to break down heparan sulfate. Fayuvi is designed to enable cells to produce the missing enzyme, reducing accumulation of heparan sulfate in the body and brain.
FDA based its assessment of effectiveness on an open-label, single-arm, multicenter study of pediatric patients with MPS IIIA. Researchers measured changes in cognitive scores among patients ages 2 to 5 and compared the results with an untreated historical control group.
According to the agency, children treated with Fayuvi maintained or improved cognitive function compared with the historical controls, diverging from the plateau and decline expected as the disease progresses.
“Parents and clinicians have been waiting far too long for an option,” Karim Mikhail, director of the FDA’s Center for Biologics Evaluation and Research, said. “Today’s approval of Fayuvi is a meaningful step forward.”
The therapy carries significant safety considerations. The most common adverse reactions reported in more than 5% of patients included elevated liver enzymes, nausea and vomiting, fever, decreased appetite, reductions in white blood cells and platelets, and increased amylase.
FDA also identified a risk of thrombotic microangiopathy, a potentially serious complication involving small blood vessels. As with other AAV-based gene therapies, the agency said there is a potential long-term risk that inserted genetic material could integrate into the genome and contribute to tumor development.
Fayuvi must be administered in a healthcare setting equipped to manage infusion reactions. Patients receive corticosteroids beginning one day before infusion and continuing for at least eight weeks afterward.
The FDA previously granted Fayuvi Orphan Drug, Fast Track and Breakthrough Therapy designations.
The approval was granted to Ultragenyx Pharmaceutical Inc.
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