FDA Reverses Course on Regenxbio Gene Therapy for Hunter Syndrome

The FDA is reopening the door to Regenxbio's experimental gene therapy Navsunli, a treatment for Hunter syndrome, a deadly and rare childhood brain disorder. According to STAT News, the agency will reconsider the therapy just four months after rejecting it.

Hunter syndrome, also known as mucopolysaccharidosis type II, is a progressive genetic disease that affects very few children and currently has limited treatment options. The speed of the FDA's about-face is unusual. Agency reversals of this kind typically take longer and require substantial new data or a successful appeal from the developer.

For Regenxbio, the decision revives a program that appeared stalled and offers families a renewed path to a potential therapy. More broadly, the move suggests the FDA is willing to apply added flexibility when evaluating treatments for ultra-rare, life-threatening pediatric conditions, where the calculus around risk and unmet need differs sharply from larger markets. How the reconsideration unfolds will be watched closely across the gene therapy field.