FDA opens path to approval for Hunter syndrome gene therapy

The US Food and Drug Administration (FDA) is allowing biotech company Regenxbio to reapply for licensing of a gene therapy for Hunter syndrome, in a reversal of its previous decision. Hunter syndrome, or mucopolysaccharidosis type II (MPS II), is a rare X-linked disorder caused by mutations in the IDS gene that leads to problems in physical and mental development. Patients typically receive weekly enzyme replacement therapy to delay disease progression and address physical but not cognitive symptoms. Regenxbio, which is based in Rockville, Maryland, has developed Navsunli, a single-dose gene therapy that delivers a functional copy of IDS to the brain. The FDA rejected Regenxbio's application for accelerated approval of Navsunli in February 2026, but has now agreed that existing clinical data may support a resubmission.

'We are encouraged by recent signals from the new FDA leadership reinforcing a commitment to address the unique nature of rare diseases and use the accelerated approval pathway to bring transformative therapies to patients with serious, unmet medical needs,' said Curran Simpson, president and CEO of Regenxbio. 'We remain focused on bringing this...