The U.S. Food and Drug Administration granted accelerated approval on 25 March 2026 for Avlayah (tividenofusp alfa-eknm), Denali Therapeutics’ enzyme replacement therapy for neurologic manifestations of Hunter syndrome in pediatric patients weighing at least 5 kg when initiated prior to advanced neurologic impairment.
The approval was based on Phase 1/2 data showing a 91% reduction in cerebrospinal fluid heparan sulfate at week 24 and normalization of CSF heparan sulfate levels in 93% of treated patients; continued approval may be contingent on confirmatory evidence from the ongoing Phase 2/3 COMPASS study.
Avlayah combines the iduronate 2-sulfatase enzyme with Denali’s TransportVehicle platform, which the company claims delivers therapeutics to the brain via transferrin receptor-mediated transcytosis. The therapy is administered once weekly, and the most common adverse reaction reported in trials was infusion-related reactions.
In connection with the approval, the FDA awarded Denali a Rare Pediatric Disease Priority Review Voucher, and the company says Avlayah will be available in the United States shortly after approval.
