The U.S. Food and Drug Administration approved Ionis Pharmaceuticals’ Zanvastro, or zilganersen, as the first and only disease-modifying therapy for Alexander disease in adults and children. The ultra-rare, progressive neurological disorder affects roughly one in every one to three million people worldwide and is caused by mutations in the GFAP gene that lead to toxic accumulation of glial fibrillary acidic protein in astrocytes. Zanvastro is an RNA-targeted medicine designed to reduce GFAP production and is administered as a 50 mg intrathecal injection every quarter. In patients aged five and older, a pivotal study showed statistically significant and clinically meaningful gait-speed stabilization versus control at Week 61, with a 33.3% least-squares mean difference on the 10-Meter Walk Test (p=0.041). Children aged two to four showed motor-function improvements on the Gross Motor Function Measure-88. Ionis agreed in June 2026 to give Recordati exclusive rights to develop and commercialize zilganersen outside the U.S., with European and Japanese regulatory submissions planned for 2027. Ionis shares rose 0.57% to $58.46 in premarket trading on Friday, according to Benzinga Pro data.