The U.S. Food and Drug Administration has approved Fayuvi (rebisufligene etisparvovec-hopf), the first treatment for pediatric patients with mucopolysaccharidosis type IIIA (MPS IIIA), also known as Sanfilippo syndrome type A, according to a statement from the agency.

MPS IIIA is a rare inherited disease that progressively damages the brain and nervous system, causing children to lose cognitive, language and other developmental abilities over time. Prior to this approval, no FDA-approved therapy existed to alter the course of the disease.

Fayuvi, developed by Ultragenyx Pharmaceutical, Inc., is a one-time intravenous gene therapy that uses a modified adeno-associated virus serotype 9 (AAV9) to deliver a working copy of the SGSH gene into a patient's cells. This enables cells to produce sulfamidase, an enzyme that is missing or deficient in MPS IIIA patients.

The therapy's safety and effectiveness were evaluated in an open-label, single-arm, multicenter clinical study of pediatric patients aged 2 to 5 years. Treated patients maintained or improved cognitive function compared to an untreated historical control group.

Adverse reactions reported in more than 5% of patients included increases in liver enzymes, nausea and vomiting, fever, decreased appetite, decreased white blood cell and platelet counts, and increased amylase. The FDA also noted a risk of thrombotic microangiopathy and a potential long-term risk of tumor development associated with genetic material integration.

Patients receive corticosteroid treatment beginning one day before infusion and continuing for a minimum of eight weeks. The therapy must be administered in a healthcare setting equipped to manage infusion reactions.

Fayuvi received Orphan Drug, Fast Track, and Breakthrough Therapy designations from the FDA.