ZANVASTRO (zilganersen)

September 3, 2026: Ionis Pharmaceuticals (NASDAQ: IONS) said the FDA approved ZANVASTRO (zilganersen) for Alexander disease in pediatric and adult patients, making it the first approved disease-modifying treatment for the ultra-rare neurologic disorder. The company also received a Rare Pediatric Disease Priority Review Voucher.

Approval was based on the pivotal Phase 1-3 Study 1 (NCT04849741), which enrolled 54 participants ages 1.5 to 53 years. In patients age 5 years and older, ZANVASTRO 50 mg met the primary endpoint at Week 61, showing statistically significant stabilization of gait speed on the 10-Meter Walk Test versus control (least square mean difference 33.3%; p=0.041). In patients ages 2 to 4 years, it improved gross motor function on GMFM-88 versus control at Week 61. Secondary and exploratory patient/caregiver- and clinician-reported outcomes consistently favored ZANVASTRO.

ZANVASTRO is given as a 50 mg intrathecal injection every 12 weeks. Safety was described as favorable; most adverse events were mild or moderate, and serious treatment-emergent adverse events were less frequent than in control. Common adverse reactions included vomiting, back pain, cough, headache, and post-lumbar puncture syndrome; aseptic meningitis was reported.

Ionis said U.S. availability is expected in the coming weeks. European and Japanese filings with Recordati are expected in 2027.