FDA has approved Ionis Pharmaceuticals’ zilganersen (Zanvastro) as the first disease-modifying therapy for ultra-rare Alexander disease. The approval marks a milestone for a rare neuroscience pipeline built around RNA-targeting and antisense platforms. For Ionis, the decision establishes a new commercial and clinical reference point for its neurology strategy beyond prior rare-disease indications. The move also signals regulator readiness to translate mechanism-driven rare-disease data into approvals even where evidence bases are small. The approval is likely to shape payer and clinician expectations for subsequent pipeline programs in genetic leukodystrophies, where biomarker and functional endpoints remain central to early development.