By Dean Seal

Ultragenyx Pharmaceutical said federal regulators have issued a complete response letter to its application for a metabolic disorder treatment that may delay the potential approval to 2026.

The biopharmaceutical company said Friday that the Food and Drug Administration's letter requested more information and potential improvements to the UX111 treatment that would address the regulator's chemistry, manufacturing and controls-related observations from manufacturing facility inspections.

"The company believes that these observations are readily addressable, related to facilities and processes, and are not directly related to the quality of the product," Ultragenyx said.

The letter will likely delay the potential approval of UX111 to 2026, the company said. It will work with the FDA in the coming months to resolve the observations.

"We are working with urgency to respond and resubmit," Ultragenyx said.

UX111 is a gene therapy being developed for Sanfilippo syndrome type A, a rare fatal lysosomal storage disease that affects the brain and currently has no approved treatment.

Write to Dean Seal at dean.seal@wsj.com

(END) Dow Jones Newswires

July 11, 2025 16:47 ET (20:47 GMT)

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