Regenxbio FDA Review Timeline Extended

By Philip Seaworth • Tuesday, August 19 15:38 • Permanent Link

Regenxbio Inc. has announced an extension of the U.S. Food and Drug Administration's (FDA) review timeline for the biologics license application (BLA) for Clemidsogene Lanparvovec (RGX-121) to treat mucopolysaccharidosis II (MPS II), also known as Hunter syndrome. The FDA has extended the Prescription Drug User Fee Act (PDUFA) goal date from November 9, 2025, to February 8, 2026.

This extension was prompted by Regenxbio's submission of longer-term clinical data for all patients in the pivotal study of RGX-121 in response to an FDA information request. The company submitted positive 12-month clinical data for 13 patients, consistent with previously submitted biomarker and neurodevelopmental data. These data will be presented during the International Congress of Inborn Errors of Metabolism (ICIEM) in September 2025.

In addition, the FDA conducted a pre-license inspection and bioresearch monitoring information inspection for the RGX-121 BLA in August 2025, with no observations or safety-related concerns raised.

Regenxbio's President and CEO, Curran M. Simpson, emphasized the urgent need for a therapeutic option to address the neurodevelopmental decline in boys with Hunter syndrome. RGX-121 has received orphan drug product, rare pediatric disease, fast track, regenerative medicine advanced therapy (RMAT) designations from the FDA, and advanced therapy medicinal products (ATMP) classification from the European Medicines Agency.

RGX-121 is a potential one-time adeno-associated virus (AAV) therapeutic designed to deliver the iduronate-2-sulfatase (IDS) gene to the central nervous system, aiming to provide a permanent source of secreted IDS protein beyond the blood-brain barrier for long-term cross-correction of cells throughout the CNS.

The FDA's extension of the review timeline signifies a delay in the potential approval of RGX-121, impacting Regenxbio's commercial launch plans. However, the company remains committed to addressing the urgent medical need for a treatment for MPS II. The market has reacted to these announcements by moving the company's shares -7.0% to a price of $8.10. If you want to know more, read the company's complete 8-K report here.

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