UX053

UX053 is an investigational mRNA-based biologic therapy developed by Ultragenyx for the treatment of Glycogen Storage Disease Type III (GSD III), also known as Cori’s disease. It consists of messenger RNA encoding the full-length human glycogen debranching enzyme (GDE), encapsulated in a lipid nanoparticle to facilitate delivery into liver cells. The therapy aims to provide functional GDE protein in patients with GSD III, who lack this enzyme due to genetic mutations, leading to pathological accumulation of glycogen in liver and muscle tissues. Preclinical studies have shown that UX053 can reduce hepatic glycogen content, and early clinical trials demonstrated that single infusions were generally well-tolerated. The drug was granted Orphan Drug Designation by both the FDA and European Commission for GSD III but its Phase 1/2 trial was terminated for reasons unrelated to safety.