Regenxbio's RGX-121 Review Timeline Extended by FDA

Regenxbio's RGX-121 review by the FDA has been extended. The company develops gene therapy using its proprietary adeno-associated virus platform to address genetic diseases. RGX-121 is being developed to treat Mucopolysaccharidosis type II, a neurodegenerative lysosomal storage disorder.

The U.S. Food and Drug Administration (FDA) has extended the review timeline for Regenxbio's RGX-121, a gene therapy candidate designed to treat Mucopolysaccharidosis type II (MPS II), also known as Hunter syndrome. The Prescription Drug User Fee Act (PDUFA) goal date has been moved from November 9, 2025, to February 8, 2026 [1].

Regenxbio announced the extension following the submission of longer-term clinical data for all patients in the pivotal study of RGX-121 (n=13) in response to an FDA information request. These positive 12-month clinical data are consistent with biomarker and neurodevelopmental data previously submitted on the same patients in the BLA [1].

The extension comes after the FDA completed a pre-license inspection and bioresearch monitoring information inspection for the RGX-121 BLA with no observations. No safety-related concerns have been raised by the FDA during the BLA review [1].

Regenxbio's RGX-121 is a one-time AAV therapeutic designed to deliver the iduronate-2-sulfatase (IDS) gene to the central nervous system (CNS), aiming to provide a permanent source of secreted iduronate-2-sulfatase (I2S) protein beyond the blood-brain barrier. This could potentially provide long-term cross correction of cells throughout the CNS, addressing the underlying genetic cause of Hunter syndrome [1].

The company plans to present updated pivotal data during the International Congress of Inborn Errors of Metabolism (ICIEM) in September 2025 [1]. Regenxbio's RGX-121 has received Orphan Drug Product, Rare Pediatric Disease, Fast Track, and Regenerative Medicine Advanced Therapy (RMAT) designations from the FDA [1].

References:
[1] https://finance.yahoo.com/news/regenxbio-announces-fda-review-extension-210000898.html
[2] https://www.prnewswire.com/news-releases/regenxbio-announces-fda-review-extension-of-bla-for-rgx-121-to-treat-patients-with-mps-ii-302532620.html