On March 25, the FDA approved Avlayah (tividenofusp alfa-eknm) for the treatment of the neurological manifestations of Hunter syndrome, also known as mucopolysaccharidosis type II, in pediatric patients weighing at least 5 kg who have not yet developed advanced neurological damage.[1] The approval is fast-tracked and it is the first drug for the neurological complications of this syndrome, given by intravenous infusion.[1] The approval is supported by a phase 1/2 study in 47 pediatric patients aged 3 months to 13 years.[1] At week 24, patients with available measurements had an average reduction in CSF heparan sulfate of 91% from baseline, ranging from 72% to 98%.[1] No patient had heparan sulfate levels below the upper limit of normal at baseline, while 93% did at week 24.[1] Treatment is intended for pre-symptomatic or symptomatic patients before advanced neurological damage.[1]