FDA Approves First Drug Targeting Rare Alexander Disease

The U.S. Food and Drug Administration (FDA) has approved Zanvstro (zilganersen), the first treatment specifically designed to target the underlying mechanism of Alexander disease, a rare and progressive genetic neurological disorder. The drug works by reducing the production of the abnormal GFAP protein that accumulates in brain cells, a hallmark of the disease.

Alexander disease affects the central nervous system and the brain's white matter, leading to symptoms such as impaired walking, speech difficulties, swallowing problems, muscle weakness, and seizures. Previously, treatments focused solely on managing these symptoms. Zanvstro is administered via spinal injection every three months and is intended for both children and adults diagnosed with the condition.

The FDA's approval is based on a clinical trial involving 53 patients aged two to 53. The study showed a significant improvement in walking speed among patients receiving the 50-milligram dose, with an average difference of 33.3% compared to the control group after 61 weeks. However, due to the rarity of the disease and the small trial size, long-term monitoring is necessary to fully assess the treatment's effectiveness, duration, and safety profile across different patient groups and disease stages.

The drug, developed by Ionis Pharmaceuticals, is expected to be available in the U.S. in the coming weeks. Its price is set at $285,000 per dose, potentially exceeding $1 million annually per patient before insurance or financial assistance. While approved in the U.S., its availability in other countries, including Israel, is not yet confirmed. This approval marks a significant shift for patients and families, offering the first therapy that directly addresses the disease's biological cause.