Ultragenyx stock falls after FDA issues complete response letter for gene therapy

Published 11/07/2025, 22:06
© Reuters.

Investing.com -- Ultragenyx Pharmaceutical (TADAWUL:2070) Inc. (NASDAQ:RARE) stock fell over 5% after the company announced that the U.S. Food and Drug Administration (FDA) has issued a Complete Response Letter (CRL) for its gene therapy treatment for Sanfilippo syndrome type A.

The FDA’s letter requested additional information and improvements related to specific aspects of chemistry, manufacturing, and controls (CMC) and addressed observations from recently completed manufacturing facility inspections. The regulatory setback will delay the potential approval of UX111 (ABO-102) to 2026, according to the company.

Ultragenyx stated that it believes the observations are "readily addressable" and primarily related to facilities and processes rather than the quality of the product itself. The company plans to work with the FDA over the next few months to resolve these issues before resubmitting the Biologics License Application (BLA).

The FDA acknowledged that the neurodevelopmental outcome data provided to date are "robust" and that biomarker data provide additional supportive evidence. The CRL did not note any review issues related to the clinical data package or clinical inspections but requested that updated clinical data from current patients be included in the resubmission.

"Our goal is to get UX111 to patients as quickly as possible knowing how critical this first therapy is to the Sanfilippo community," said Emil D. Kakkis, M.D., Ph.D., chief executive officer and president of Ultragenyx. "We have been diligently responding to the recent CMC observations and our priority is to resolve them so that we can resubmit the BLA as soon as possible."

Following resubmission, the company anticipates up to a six-month review period by the FDA.

This article was generated with the support of AI and reviewed by an editor. For more information see our T&C.

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