Biotech company Regenxbio has reached an agreement with the US Food and Drug Administration on accelerated approval for its gene therapy Navsunli – the only potential one‑time treatment for Hunter syndrome, also known as mucopolysaccharidosis type II (MPS II). The regulator said it would reverse its earlier refusal, confirmed that existing clinical data are sufficient for filing an application, and did not require any new studies.
The FDA had rejected the company’s marketing application in February 2026, citing uncertainty over the clinical trial design. However, the agency has since revised its position. Regenxbio noted that no additional patient enrolment or new studies – including the previously requested placebo‑controlled trial – will be required.
The company plans to request a formal meeting with the FDA in July and refile its marketing application in the third quarter of 2026. The regulator has said it will review the application on an accelerated timeline, with labelling discussions to begin shortly after submission. Regenxbio shares jumped 10% in pre‑market trading on the news.
Hunter syndrome is an extremely rare genetic disorder in which the body cannot break down certain sugar molecules, leading to physical and cognitive impairments.
The move is part of a broader trend of the FDA softening its approach to rare disease therapies. Earlier in June, acting FDA commissioner Kyle Diamantas met with patient advocacy groups, signalling the agency’s effort to improve dialogue with the industry. The FDA has also shifted its stance on uniQure’s Huntington’s disease gene therapy, and in May, Replimune reached an agreement with the regulator on a third attempt to gain approval for its skin cancer drug.