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RGX-121

Drug

Drug Profile

RGX-121 is an investigational one-time AAV9 gene therapy candidate for mucopolysaccharidosis type II (MPS II, Hunter syndrome). The program is intended to deliver iduronate-2-sulfatase gene expression through CNS-directed administration and has been evaluated in Phase I/II studies. As of January 29, 2026, partner disclosures reported an FDA clinical hold on RGX-121.

Drug Class
Investigational one-time AAV9 gene therapy
Approval Status
Investigational; FDA clinical hold reported on January 29, 2026
Mechanism of Action
Uses NAV AAV9 vector to deliver the iduronate-2-sulfatase (IDS) gene for one-time gene therapy treatment
Brand Names
  • RGX-121
Indications
  • \Mucopolysaccharidosis type II (MPS II, Hunter syndrome)\

Related News

FDA Grants Accelerated Approval to First Therapy for Neurological Effects of Hunter Syndrome

The FDA has granted accelerated approval to Denali Therapeutics' Avlayah (tividenofusp alfa-eknm), the first therapy targeting neurological symptoms of Hunter syndrome. The approval was based on a surrogate endpoint measuring heparan sulfate reduction in cerebrospinal fluid, with confirmatory study results required for full approval. The global Hunter syndrome treatment market is projected to reach $2.6 billion by 2033.