Denali Therapeutics has received FDA approval for AVLAYAH (tividenofusp alfa-eknm), the first biologic specifically designed to cross the blood-brain barrier and reach the brain[3]. The drug is intended for the treatment of neurological manifestations of Hunter's syndrome (mucopolysaccharidosis type II) in pediatric patients weighing at least 5 kg before advanced neurological damage[3]. AVLAYAH is an enzyme replacement therapy that supplies the missing enzyme throughout the body, including the brain[7]. The approval was granted based on data from an open-label, single-arm, phase 1/2 study in 47 participants with Hunter syndrome[7]. Continued approval of the drug may be contingent upon verification of clinical benefit in the confirmatory Phase 2/3 COMPASS study, in which participants are randomized 2:1 to treatment with either AVLAYAH or idursulfase[3]. In connection with the approval of AVLAYAH, the FDA granted Denali Therapeutics a Rare Pediatric Disease Priority Review Voucher[3].