Denali Therapeutics’ application for approval of its Hunter syndrome therapy tividenofusp alfa has been delayed by the FDA, with the decision date pushed back by three months to April 5, 2026. The delay follows Denali’s submission of updated clinical pharmacology information in response to a routine FDA request. According to Denali, this information is not related to efficacy, safety, or biomarkers, and the FDA did not request any new clinical data. The FDA classified the amendment as a major change, extending the Biologics License Application’s review period as per regulatory guidelines.
FDA Review Timelines Extended
The FDA initially set the Prescription Drug User Fee Act (PDUFA) target date for January 5, 2026, when it accepted Denali’s BLA in July 2025, granting priority review for tividenofusp alfa for mucopolysaccharidosis type II (Hunter syndrome). The extended review period was triggered by Denali’s submission of updated molecular weight data for the investigational enzyme replacement therapy, which was classified as a major amendment due to implications for label-related calculations. Analysts consider the delay a technical issue rather than one impacting the drug’s approvability.
Company Response and Outlook
Denali’s management has stated that the amendment does not affect the benefit-risk profile or clinical pharmacology underpinning the application. CEO Ryan Watts emphasized ongoing collaboration with the FDA and continued preparation for potential product launch pending regulatory approval. Tividenofusp alfa aims to address neurological as well as physical symptoms of Hunter syndrome, which currently lacks effective treatments for the central nervous system manifestations. Denali continues enrollment in its Phase 2/3 COMPASS study to support global approval efforts.
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