Ionis Pharmaceuticals won FDA approval for Zanvastro, the first disease-modifying therapy for Alexander disease, in a pivotal program designed around walking speed as a core motor endpoint. The approval covers both children and adults. In the trial supporting approval, treated patients’ walking speed remained stable while those in the control group saw a 33% decline. The dataset also showed hints that earlier treatment—particularly in young children—may improve motor function rather than just slowing decline. Safety was generally manageable, with serious adverse events occurring more often in the control group than among treated patients. The approval marks a new regulatory milestone for antisense approaches in rare neurodegeneration, where options remain limited.