By FieldPulse Editorial · March 25, 2026
Tags: FDA, Pipeline
The FDA has granted accelerated approval to Denali Therapeutics' Avlayah for Hunter syndrome, marking the first clearance of a drug specifically engineered to penetrate the blood-brain barrier.
The FDA on March 25 approved Denali Therapeutics' Avlayah (tividenofusp alfa-eknm) for the treatment of Hunter syndrome, known clinically as mucopolysaccharidosis type II (MPS II) — a decision that marks a genuine inflection point in rare disease drug development. Avlayah is the first FDA-approved therapy explicitly engineered to cross the blood-brain barrier (BBB), a longstanding obstacle in neuroscience and rare disease medicine. Denali achieved this by leveraging the transferrin receptor mechanism, essentially hijacking the brain's natural iron-transport pathway to ferry a therapeutic enzym