FDA issues Complete Response Letter for Ultragenyx UX111 BLA; resubmission planned with 6-month review

Ultragenyx Pharmaceutical Inc.

FDA CRL received July 11, 2025, for UX111 (ABO-102) AAV gene therapy for Sanfilippo syndrome type A.
CRL requests additional CMC documentation and addresses observations from manufacturing facility inspections.
Company states observations are readily addressable and unrelated to product quality; clinical data package not cited.
FDA acknowledged robust neurodevelopmental outcome data and supportive biomarker evidence; updated clinical data requested.
Ultragenyx plans to resubmit BLA within months, expecting up to 6-month FDA review period.

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