FDA approval of Zanvastro (zilganersen) marks the first disease‑modifying therapy for Alexander disease, an ultra‑rare and often fatal neurological disorder. The RNA‑targeted drug reduces GFAP protein production and is given as a 50 mg intrathecal dose every three months. In patients aged five and older, Zanvastro stabilized gait at Week 61 versus control (10‑Meter Walk Test: 33.3% difference, p = 0.041); children aged two to four showed motor gains on the GMFM‑88. Ionis licensed ex‑U.S. rights to Recordati and plans regulatory filings in Europe and Japan in 2027.
FDA Approves Zanvastro (zilganersen) — First Disease‑Modifying Therapy for Alexander Disease
Ionis Drug Wins FDA Approval as First Alexander Disease Treatment
The U.S. Food and Drug Administration has approved Zanvastro (zilganersen), developed by Ionis Pharmaceuticals, for the treatment of Alexander disease in adult and pediatric patients.
Alexander disease is an ultra‑rare, progressive, and frequently life‑threatening neurological disorder caused by mutations in the GFAP gene. These mutations drive overproduction and toxic accumulation of glial fibrillary acidic protein in astrocytes, which in turn damages nearby neurons and myelin and leads to progressive cognitive, motor, autonomic, and gastrointestinal decline.
Zanvastro is an RNA‑targeted therapy designed to reduce production of GFAP protein, addressing a root cause of the disease rather than only treating symptoms. The medicine is administered as a 50 mg intrathecal injection every three months (quarterly).
Clinical Evidence
The FDA approval is based on positive data from a pivotal clinical trial. In patients aged five years and older, the primary endpoint was met: quarterly 50 mg dosing produced statistically significant and clinically meaningful stabilization in gait speed versus control at Week 61 as measured by the 10‑Meter Walk Test. The reported result showed a 33.3% least‑squares mean difference in favor of Zanvastro (p = 0.041).
In children aged two to four years, treatment with Zanvastro produced improvements in motor function measured by the Gross Motor Function Measure‑88 (GMFM‑88). Secondary and exploratory endpoints — including clinician, caregiver, and patient‑reported outcomes — consistently favored Zanvastro over control.
Commercial and Regulatory Plans
In June 2026, Ionis signed a licensing agreement with Italian specialty pharmaceutical company Recordati that grants Recordati exclusive rights to commercialize and develop zilganersen outside the United States. Ionis and Recordati are collaborating on regulatory submissions for Europe and Japan, with planned filings in 2027.
What This Means: Zanvastro represents the first disease‑modifying option for people living with Alexander disease, offering a new therapeutic approach for a condition that historically had no treatments beyond symptom management.
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