Ionis Pharmaceuticals (NASDAQ: IONS) announced Thursday September 3, 2026 FDA approval of Zanvastro (zilganersen, an intrathecally-administered antisense oligonucleotide designed to reduce glial fibrillary acidic protein / GFAP production) for the treatment of Alexander disease in pediatric and adult patients. The approval is the first-ever disease-modifying therapy for Alexander disease, an ultra-rare autosomal dominant neurodegenerative disorder caused by GFAP gene mutations that presents in infancy through adulthood with progressive motor and cognitive decline. Approval landed 19 days ahead of the September 22, 2026 PDUFA target action date. In the registrational trial, walking speed stayed stable in Zanvastro-treated patients while control patients saw a 33% decline. FDA granted Ionis a Rare Pediatric Disease Priority Review Voucher (PRV) alongside the approval; PRVs have historically sold for $150-350 million on secondary markets. Zanvastro follows Ionis's Wainua (eplontersen) commercial franchise for hereditary transthyretin amyloid polyneuropathy and lands after the August 28 CARDIO-TTRansform ATTR-CM Phase 3 primary endpoint miss for the same molecule.
Ultragenyx Pharmaceutical (NASDAQ: RARE) awaits its September 19, 2026 PDUFA target action date for UX111 (rebisufligene etisparvovec, an AAV9 gene therapy delivering the SGSH gene) for the treatment of Sanfilippo syndrome type A (mucopolysaccharidosis type IIIA, MPS IIIA, a rare autosomal recessive lysosomal storage disorder caused by SGSH gene mutations that results in progressive cognitive decline in early childhood and death typically by the second decade). If approved, UX111 would become the first FDA-approved therapy for MPS IIIA, where the current standard of care remains supportive symptom management. The AAV9-based intravenous delivery approach mirrors the Novartis Zolgensma (onasemnogene abeparvovec) commercial template for spinal muscular atrophy and continues the neurometabolic gene therapy pipeline. Not a peptide, but the approval would extend the AAV gene therapy commercial category that has continued to reshape the rare-disease landscape alongside enzyme replacement therapies and the emerging small-molecule chaperone class.
Ionis Pharmaceuticals (NASDAQ: IONS) awaits its September 22, 2026 PDUFA target action date for zilganersen (an intrathecally-administered antisense oligonucleotide designed to reduce production of glial fibrillary acidic protein / GFAP) for the treatment of Alexander disease, a rare autosomal dominant neurodegenerative disease caused by GFAP gene mutations. If approved, zilganersen would become the first FDA-approved therapy for Alexander disease and Ionis's next commercial launch following Wainua (eplontersen) for hereditary transthyretin amyloid polyneuropathy (with the CARDIO-TTransform ATTR-CM primary endpoint miss now behind the company). Zilganersen was granted FDA Fast Track designation and Orphan Drug designation. Alexander disease presents in infancy through adulthood with progressive motor and cognitive decline; no disease-modifying therapies are currently approved. Not a peptide, but the antisense oligonucleotide class continues to complement peptide-based rare-disease therapies (Rein Therapeutics LTI-03 Caveolin-1 peptide for IPF among others) as the RNA modality expands into ultra-orphan indications.