Ultragenyx drug for Angelman syndrome shows no benefit in phase 3 trial

Ultragenyx Pharmaceutical has reported that its investigational therapy for Angelman syndrome did not demonstrate a statistically significant benefit over sham treatment in a phase 3 clinical trial. The result is a setback for a disease community with very limited therapeutic options.

Angelman syndrome is a rare neurodevelopmental disorder arising from loss of function of the maternally inherited UBE3A gene on chromosome 15q11–q13. It is characterised by severe intellectual disability, absent or minimal speech, seizures, and a distinctive behavioural phenotype. The condition affects approximately 1 in 12,000–20,000 live births.

Ultragenyx did not specify the mechanism of the experimental therapy in the publicly reported summary reviewed here, and full trial data have not yet been published in a peer-reviewed journal. STAT News reported the top-line result. The failure follows a broader pattern of phase 3 attrition in rare neurodevelopmental conditions, where translating animal-model results to clinical benefit has proved consistently difficult.

Several other programmes targeting Angelman syndrome remain in development, including antisense oligonucleotide and gene therapy approaches aimed at unsilencing the paternal UBE3A copy. Researchers and families await further reporting of the full dataset to understand whether any subgroups or endpoints showed differential responses.