Zilganersen Receives Fast Track Designation from FDA

The US Food and Drug Administration (FDA) has granted Fast Track designation to zilganersen for the treatment of a rare type of leukodystrophy known as Alexander disease.

Topline data from the pivotal study of zilganersen is expected in the second half of 2025. The FDA grants investigational medicines Fast Track designation to facilitate the development and expedite the review of medicines that demonstrate the potential to treat serious conditions and fill an unmet medical need.

"With no approved treatments available for people living with AxD, receiving this Fast Track designation for zilganersen reflects the seriousness of this ultra-rare disease and the significant unmet need for treatment in this patient population," said Eugene Schneider, M.D., executive vice president and chief clinical development officer at Ionis. "Zilganersen was designed to address the underlying cause of disease and help improve the functioning of people living with AxD. We look forward to a data readout next year and working closely with the FDA to potentially bring forward the first approved AxD treatment."

The pivotal Phase 1-3 study of zilganersen in adults and children living with AxD completed enrollment earlier this year across 13 sites in eight countries.

About Alexander Disease (AxD)

AxD is an ultra-rare, progressive, and ultimately fatal type of leukodystrophy, which are a group of genetic disorders that affect the brain's white matter. AxD is estimated to occur in approximately one in one million to one in three million people worldwide and usually leads to death within 14 - 25 years after symptom onset. AxD can present throughout life as loss of independence and lack of ability to control muscles for swallowing, airway protection, and purposeful movements, though the impact of AxD can vary depending on factors like age of onset. Diagnosing AxD is based on a combination of clinical presentation, brain magnetic resonance imaging (MRI) findings, and genetic testing. AxD is caused by changes in the glial fibrillary acidic protein (GFAP) gene that lead to a build-up of abnormal proteins in cells, causing progressive damage to the nervous system. There are no medicines approved for people with AxD, and current treatments focus on managing their symptoms.

About Zilganersen (ION373)

Zilganersen is an investigational antisense oligonucleotide medicine being developed as a potential treatment for people with genetically confirmed Alexander disease (AxD). Zilganersen is designed to stop the excess glial fibrillary acidic protein (GFAP) production that accumulates because of disease-causing variants in the GFAP gene. In 2020, the U.S. Food and Drug Administration (FDA) granted zilganersen Orphan Drug designation and Rare Pediatric Disease designation. In addition, the European Medicines Agency (EMA) granted zilganersen Orphan Drug designation in 2019.