Investing.com -- Shares of Regenxbio Inc . (NASDAQ: RGNX ) climbed 7.2% in premarket trading after the company announced the U.S. Food and Drug Administration (FDA) has accepted for priority review its Biologics License Application (BLA) for RGX-121, a potential gene therapy for Mucopolysaccharidosis II (MPS II), also known as Hunter syndrome.

The FDA’s decision to grant the BLA Priority Review status, with a Prescription Drug User Fee Act (PDUFA) target action date set for November 9, 2025, has sparked investor optimism. The therapy is poised to become the first gene therapy and one-time treatment for MPS II, a move that could significantly alter the treatment paradigm for the condition.

REGENXBIO’s President and CEO, Curran M. Simpson, expressed excitement over the milestone, noting the therapy’s potential to address both neurodevelopmental and systemic effects of Hunter syndrome. The company has highlighted positive biomarker data and long-term outcomes that support the therapy’s transformative potential, which could reduce the burden patients and families face with the current standard of weekly enzyme replacement therapy.

The strategic partnership with Nippon Shinyaku, announced in January 2025, positions NS Pharma, Inc., a subsidiary of Nippon Shinyaku, to lead the commercialization of RGX-121 in the U.S. upon FDA approval. Additionally, the approval of RGX-121 could result in the receipt of a Priority Review Voucher (PRV), with REGENXBIO retaining all rights to any proceeds from the potential sale of the PRV.

RGX-121 has received multiple designations from the FDA, including Orphan Drug Product, Rare Pediatric Disease, Fast Track, and Regenerative Medicine Advanced Therapy (RMAT), as well as advanced therapy medicinal products (ATMP) classification from the European Medicines Agency, underscoring its significance in treating MPS II.

Investors are responding positively to the news, reflecting confidence in the therapy’s market potential and the company’s strategic position in leading commercial manufacturing and supply chain efforts for the gene therapy. The acceptance of the BLA by the FDA marks a critical step forward for REGENXBIO as it works to bring this innovative treatment to the MPS II patient community.

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