The FDA approved Ionis Pharmaceuticals’ antisense therapy zilganersen (Zanvastro) for Alexander disease, delivering the first disease-modifying option for the ultra-rare, progressive neurologic disorder. The approval covers pediatric and adult patients, and positions Ionis to commercialize the product without a commercialization partner. Ionis had previously reported that Alexander disease patients can be treated with the RNA-based approach to slow disease progression, but the new approval marks the point where evidence becomes available at the bedside. The decision also expands Ionis’ neurology portfolio beyond its earlier rare-disease footprint. Separately, the approval narrative underscores a broader pattern in rare-disease development: targeted RNA medicines moving from clinical-stage validation to differentiated, mechanism-driven clinical use—where manufacturing scalability and payer pathways often define next steps.