Ionis Pharmaceuticals has concluded enrolment in the pivotal cohort (Cohort 1) of its Phase III REVEAL study of obudanersen (ION582) as an investigational ribonucleic acid (RNA)-targeted medicine for Angelman syndrome (AS).
The randomised, global, controlled, double-blind trial targets people affected by AS, a neurodevelopmental disorder resulting in serious communication, physical, and cognitive impairments.
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Cohort 1 enrolled 136 participants aged two to less than 18 years, all with AS and either a UBE3A deletion or mutation confirmed genetically.
A separate adult cohort (Cohort 2), comprising participants aged 18 to 50 years, is targeted for enrolment completion by the third quarter of 2026.
The company expects topline data from the study in the second half of 2027.
Ionis executive vice-president and chief development officer Holly Kordasiewicz said: “Completion of enrolment in the pivotal cohort of REVEAL marks an important step towards a potential disease-modifying treatment for people living with this serious and complex neurological condition, for which there are no approved medicines.
“Guided by input from the Angelman community, REVEAL was intentionally designed to evaluate obudanersen across a broad range of people living with Angelman syndrome, reflecting the real-world diversity of this condition.”
The REVEAL Phase III trial will enrol approximately 158 individuals with AS.
The primary endpoint is improvement in expressive communication, measured by the Bayley Scales for Infant and Toddler Development-4.
Secondary endpoints include cognition, communication, daily living skills, disease severity, motor function, sleep and other exploratory measures.
Ionis plans to advance obudanersen into the Phase III CHAMPION trial to include individuals with uniparental disomy (UPD) or imprinting defect genotypes, expected to commence before the end of 2026.
Obudanersen holds orphan drug status from both the US Food and Drug Administration (FDA) and the European Medicines Agency, as well as fast track and rare paediatric designations from the FDA.
In September 2025, Ionis Pharmaceuticals reported encouraging top line outcomes from the randomised Phase III CORE and CORE2 trials of the investigational RNA-targeted therapy, olezarsen, in those with severe hypertriglyceridemia.
