The FDA cleared Ionis Pharmaceuticals’ antisense therapy Zanvastro (zilganersen) for Alexander disease in both pediatric and adult patients, establishing the first disease-modifying treatment for the ultra-rare, progressive neurological disorder. The approval follows pivotal trial results that showed treated patients had less decline in gait speed than controls, with additional signals in younger children. With Zanvastro given quarterly as an intrathecal injection, the decision also marks Ionis’ first wholly owned neurology launch without a commercialization partner. The agency granted a rare pediatric disease priority review voucher, and Ionis said the drug will be available in the coming weeks. For clinicians and payers, the approval provides a first-targeted option aimed at reducing GFAP-related disease biology, rather than symptomatic care. For the broader biotech sector, it reinforces how RNA-based therapeutics can move from late-stage readouts to a commercially relevant regulatory foothold in rare neurodegeneration.