The U.S. Food and Drug Administration extended review of Denali Therapeutics’ biologics license application for tividenofusp (tivi), a transferrin‑receptor‑engineered enzyme replacement therapy for Hunter syndrome, by three months to April 5, 2026. The agency classified Denali’s submission of updated clinical pharmacology data as a major amendment, triggering the extension. Denali said the amendment did not change the drug’s efficacy, safety or biomarker package and that the information was submitted proactively after identifying a molecular weight discrepancy in a public source used for FDA analyses. Company CEO Ryan Watts said Denali continues to prepare for potential approval and launch. Analysts characterized the delay as procedural and not reflecting new clinical concerns, but it pushes the regulatory timeline for a therapy designed to cross the blood‑brain barrier—an increasingly pivotal mechanism in neurodegenerative and lysosomal disease development.