Giving the Silent Paternal Gene a Voice Again: Antisense Therapy for Angelman Syndrome Enters Phase 3 Trial

Angelman syndrome research is moving beyond alleviating seizures, sleep problems, and behavioral issues toward directly addressing the disease’s molecular cause. Oak Hill Bio announced that the first participant has been dosed in the global Phase 3 BEACON trial, which has begun evaluating whether the antisense oligonucleotide rugonersen can restore UBE3A gene expression in neurons and thereby improve patients’ cognitive and communication abilities.

Angelman syndrome is a rare neurodevelopmental disorder. Patients commonly experience severe developmental delays, limited language abilities, impaired motor coordination, and seizures. In neurons, the paternally inherited UBE3A is normally silenced; if the maternal UBE3A cannot function properly because of a deletion or another genetic abnormality, the brain lacks sufficient UBE3A protein. Rugonersen is designed to use an antisense oligonucleotide to lift the silencing of the paternal gene, allowing it to produce protein again.

According to the clinical trial registry, BEACON, identified as NCT07605429, is a randomized, double-blind, sham procedure-controlled study expected to enroll up to 165 patients between 1 and 50 years of age. The drug will be delivered into the cerebrospinal fluid by intrathecal injection. The control design is intended to distinguish, as much as possible, the effects of the drug from changes in care and the effects of trial participation itself.

The trial’s primary assessment time point is Week 56. The key endpoint is the change from baseline in the cognitive and/or expressive communication raw scores on the Bayley-4 scale. This choice focuses on whether patients acquire new developmental abilities rather than measuring only molecular markers. After the double-blind phase, the study includes an open-label extension of approximately 116 weeks to track longer-term efficacy and safety. The primary study is currently estimated to be completed in March 2029.

The launch of Phase 3 does not mean efficacy has been established. Patients with Angelman syndrome vary widely in age, genotype, and baseline abilities, and the broad inclusion range of 1 to 50 years may also make interpreting the results more complex. The tolerability of repeated intrathecal dosing, implementation of the sham procedure control, and whether changes in scale scores reflect meaningful improvements experienced by patients and families will all be important considerations when interpreting the trial results.

The program has also received new financial backing. Industry media reported that Oak Hill Bio plans to merge with Research Alliance Corporation III, in a transaction expected to generate approximately $175 million in gross proceeds to advance development work including rugonersen; the transaction remains subject to closing conditions. For patients, the crucial answer must still come from BEACON: whether restoring UBE3A expression can deliver measurable, sustained functional improvements across different ages and stages of disease.