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FDA Rejects Regenxbio's Hunter Syndrome Treatment Amid Safety Concerns

2/10/2026

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Summary

Story summary

The FDA rejected Regenxbio's RGX-121 for Hunter syndrome due to concerns about trial design and a biomarker surrogate endpoint.
The decision followed a clinical hold after a brain tumor appeared in a patient treated with RGX-111.
Regenxbio plans to resubmit RGX-121 with additional long-term data.
Experts express disappointment, and the National MPS Society says the decision harms families affected by Hunter syndrome.

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Story summary

The FDA rejected Regenxbio's RGX-121 for Hunter syndrome due to concerns about trial design and a biomarker surrogate endpoint.
The decision followed a clinical hold after a brain tumor appeared in a patient treated with RGX-111.
Regenxbio plans to resubmit RGX-121 with additional long-term data.
Experts express disappointment, and the National MPS Society says the decision harms families affected by Hunter syndrome.