The FDA approved Ionis Pharmaceuticals’ Zanvastro, the first disease-modifying therapy for Alexander disease, extending motor function stability versus decline in a pivotal trial. The approval covers both children and adults, reflecting the disease’s broad clinical spectrum. In the key study, walking speed—an established motor function measure—remained stable in treated patients while the control group saw a 33% decline. Ionis also reported safety findings consistent with the program, with serious adverse events more common in controls. The approval adds another targeted antisense option to the growing set of FDA-cleared RNA-based medicines and could accelerate uptake among clinicians treating this ultra-rare neurological condition.