Ultragenyx Pharmaceutical Inc. Receives Breakthrough Therapy Designation for GTX-102 in Angelman Syndrome

Published: 2025-06-27 10:05:46 ET RARE

Published on 06/27/2025 at 10:05

Ultragenyx Pharmaceutical Inc. announced that it has received Breakthrough Therapy Designation from the U.S. Food and Drug Administration (FDA) for GTX-102 (apazunersen) as a treatment for Angelman syndrome. The FDA's decision is based on preliminary clinical evidence including positive data from the Phase 1/2 study in 74 patients (4-17 years of age) with a full maternal UBE3A gene deletion, that showed participants have made consistent developmental gains with rapid, sustained and continuing improvements across multiple symptom domains when treated for up to 3 years. Breakthrough Therapy Designation aims to expedite the development and review of drugs that are intended to treat serious or life-threatening diseases and whose preliminary clinical evidence indicates that the drug may demonstrate substantial improvement on one or more clinically significant endpoints over existing therapies.

Enrollment in the global Phase 3 Aspire study (NCT06617429) began in December 2024 and is expected to enroll approximately 120 children ages four to 17 with Angelman syndrome with a genetically confirmed diagnosis of full maternal UBE3A genetic deletion. Families can learn more by visiting. About GTX-102 (apazUNersen) is an investigational antisense oligonucleotide (ASO) therapy delivered via intrathecal administration and designed to target and inhibit expression of the UBE3A antisense transcript (UBE3A-AS) to prevent silencing of the paternally inherited allele of the UBE3A gene and reactivate expression of the deficiency protein.

GTX-102 has been granted Breakthrough Therapy Designation, Orphan Drug Designation, Rare Pediatric Disease Designation, and Fast Track Designation from the FDA and Orphan Designation and PRIME designation from the EMA. Angelman syndrome is a rare, neurogenetic disorder caused by loss-of-function of the maternally inherited allele of theUBE3A gene. The maternal-specific inheritance pattern of Angelman syndrome is due to genomic imprinting of UBE3A in neurons of the central nervous system (CNS), a naturally occurring phenomenon in which the maternal UBE3A allele is expressed and the paternal UBE3A is not.