FDA reviews RGX-121 for Hunter Syndrome

REGENXBIO Inc. announced the FDA has accepted for review the Biologics License Application (BLA) seeking accelerated approval for clemidsogene lanparvovec (RGX 121) for the treatment of Mucopolysaccharidosis II (MPS II), also known as Hunter syndrome. The FDA granted the BLA Priority Review with a Prescription Drug User Fee Act (PDUFA) target action date of November 9, 2025.

"Acceptance of the RGX 121 BLA marks an exciting milestone on our path to bring the MPS II patient community a one-time treatment with the potential to address both the neurodevelopmental and systemic effects of Hunter syndrome," said Curran M. Simpson, President and Chief Executive Officer of REGENXBIO. "Supported by positive biomarker data and long-term outcomes, RGX 121 has the potential to be a first-in-class gene therapy that could dramatically transform the MPS II treatment landscape and reduce the significant burden patients and families currently face with weekly enzyme replacement therapy."

RGX 121 has received Orphan Drug Product, Rare Pediatric Disease, Fast Track and Regenerative Medicine Advanced Therapy (RMAT) designations from the FDA and advanced therapy medicinal products (ATMP) classification from the European Medicines Agency. 

Under the strategic partnership announced in January 2025, following potential FDA approval, RGX 121 will be commercialized by NS Pharma, Inc., a wholly-owned subsidiary of Nippon Shinyaku, in the U.S. Approval of RGX 121 could result in receipt of a Priority Review Voucher (PRV). REGENXBIO retains all rights to, and 100 percent of any proceeds related to the potential sale of, the PRV for RGX 121.