Ionis Receives FDA Breakthrough Therapy Designation for Zilganersen in Alexander Disease
Ionis Pharmaceuticals has announced that the U.S. Food and Drug Administration (FDA) has granted Breakthrough Therapy designation to zilganersen for the treatment of Alexander disease (AxD), a rare, progressive and often fatal neurological condition.
AxD affects approximately 1 in 1–3 million people worldwide and leads to progressive loss of mobility, independence, and difficulties with walking, speaking, swallowing, and breathing. There are currently no approved disease-modifying treatments for the condition.
Breakthrough Therapy designation is intended to expedite the review of treatments for serious or life-threatening conditions that show preliminary clinical evidence of substantial improvement over existing therapies.
Zilganersen is an investigational antisense oligonucleotide designed to reduce excess glial fibrillary acidic protein (GFAP) caused by disease-related variants in the GFAP gene.
The designation is supported by topline results from a pivotal global Phase 1–3 study (NCT04849741) in 54 participants aged 1.5–53 years.
In the study, the 50 mg dose of zilganersen demonstrated statistically significant and clinically meaningful stabilization in gait speed, assessed by the 10-Meter Walk Test, alongside consistent improvements in secondary endpoints and favourable safety and tolerability.
Ionis plans to submit a New Drug Application to the FDA in Q1 2026 and initiate an Expanded Access Program in the U.S.
The company’s neurology portfolio also includes investigational treatments for rare and serious neurological diseases, continuing Ionis’ focus on addressing unmet medical needs.
