Ionis Pharmaceuticals prices first approved Alexander disease therapy at $285,000 per dose

Ionis Pharmaceuticals (IONS) priced zilganersen, its newly approved treatment for Alexander disease, at $285,000 per dose, a day after U.S. regulators cleared the injectable drug as the first approved therapy for the rare genetic disorder in both adults and children.

Alexander disease is a rare neurodegenerative condition that typically manifests in early childhood, progressively damaging brain cells and impairing movement, speech and swallowing. Fewer than 1,000 people in the United States are affected, according to the National Institutes of Health.

Branded as Zanvastro, the therapy is administered by injection into the spinal canal every three months by a healthcare professional. Ionis expects peak annual sales to exceed $100 million and said the drug would be available in the United States within weeks.

In a combined early-to-late-stage clinical study, patients who received a 50 mg dose of Zanvastro demonstrated a statistically significant improvement in gait speed, as measured by a 10-meter walk test at 61 weeks. Jenny Pearson, whose daughter participated in the trial, described the approval as a "miracle" that offered families meaningful hope.

Jay Olson, an analyst at Oppenheimer, said the approval materially reduces risk across Ionis' broader neurology pipeline, including obudanersen, its candidate for Angelman syndrome, for which late-stage trial data are expected in the second half of 2027. Olson said he did not view the recent late-stage failure of Ultragenyx Pharmaceutical's (RARE) rival Angelman syndrome drug apazunersen as bearing negatively on obudanersen's prospects. Ionis said it would continue to study Zanvastro in an open-label extension trial.