REGENXBIO's RGX-121 for Hunter Syndrome Hits FDA Clinical Hold Over Asymptomatic Spine Findings
Event summary
- FDA placed a clinical hold on REGENXBIO's RGX-121 for MPS II (Hunter Syndrome) due to asymptomatic spine MRI findings in five participants.
- REGENXBIO does not expect to resubmit the RGX-121 Biologics License Application (BLA) in the near term.
- All five participants continue to do well clinically with no serious adverse events reported.
- RGX-121 utilizes a different capsid and route of administration compared to REGENXBIO's other candidates.
- REGENXBIO plans to submit the Duchenne BLA this quarter and announce wet AMD topline pivotal data in Q4 2026.
The big picture
REGENXBIO's setback with RGX-121 highlights the regulatory scrutiny facing gene therapies targeting the central nervous system. The company's ability to pivot focus to its Duchenne and retinal disease candidates will be critical in maintaining investor confidence. The clinical hold underscores the challenges of developing treatments for ultra-rare diseases, where long-term safety data is limited.
What we're watching
- Regulatory Headwinds
- How the FDA's clinical hold will impact the timeline and approval prospects for RGX-121.
- Pipeline Focus
- Whether REGENXBIO can maintain momentum with its Duchenne and retinal disease candidates amid the RGX-121 setback.
- Execution Risk
- The pace at which REGENXBIO can gather additional data and address the FDA's concerns for RGX-121.
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