Ionis Pharmaceuticals secured FDA approval for Zanvastro, described as the first disease-modifying therapy for Alexander disease, a rare and deadly neurological condition. The therapy is approved for children and adults after a pivotal trial showed walking speed remained stable in treated patients, while those in the control group saw a 33% decline. Ionis said the trial also offered signals that treating younger children may improve motor function rather than just stabilize it. Safety results were generally consistent with the program, with serious adverse events reported more frequently in the control group than among treated participants. With no previously approved disease-modifying option for Alexander disease, the decision marks a regulatory milestone for antisense oligonucleotide approaches in rare neurogenetic disorders. The approval also intensifies competition for therapies targeting other leukodystrophies and neurodegenerative conditions, where early clinical endpoints and functional measures increasingly guide regulatory decisions.