Ionis Pharmaceuticals has reported positive top-line results from a pivotal Phase 3 study evaluating zilganersen, an antisense oligonucleotide for Alexander disease, a rare and fatal inherited neurological disorder. The trial showed a significant disease-modifying effect, notably improvement in gait speed. Following the success, Ionis plans to file for FDA approval in early 2026, marking a potential first approved therapy for this ultra-rare condition.