REVEAL Study: Phase 3 Study of the Efficacy and Safety of ION582 in Children and Adults with Angelman Syndrome

Trial status: Authorised 1. Change in Bayley Scales for Infant and Toddler Development-4 (Bayley-4): Cognition Subdomain Raw Score without caregiver input [Time Frame: Baseline and Week 52], 2. Change in Symptoms of Angelman Syndrome -Clinician Global Impression of Change (SAS-CGI-C): Overall AS [Time Frame: Baseline and Week 52], 3. Change in Vineland Adaptive Behavior Scale-3 (Vineland-3): Receptive Communication Subdomain Raw Score [Time Frame: Baseline and Week 52], 4. Change in Vineland Adaptive Behavior Scale-3 (Vineland-3): Daily Living Skills, Personal Subdomain Raw Score [Time Frame: Baseline and Week 52], 5. Change in Symptoms of Angelman Syndrome - Clinician Global Impression of Change (SAS-CGI-C): Sleep Problems [Time Frame: Baseline and Week 52], 6. Change in Bayley Scales for Infant and Toddler Development-4 (Bayley-4): Fine Motor Subdomain Raw Score without caregiver input [Time Frame: Baseline to Week 52], 7. Change in Observer-Reported Communication Ability (ORCA): Overall Emerging T score [Time Frame: Baseline and Week 52], 8. Percentage of Participants with Treatment-emergent Adverse Events (TEAEs) and Serious Adverse Events (SAEs) [Time Frame: Up to Week 52], 9. Change in Vital Signs and Clinical Laboratory Results [Time Frame: Baseline and Week 52] Change in performance on the Expressive Communication subdomain raw score of the Bayley Scales for Infant and Toddler Development-4 (Bayley-4) without caregiver input in Cohort 1 [Time Frame: Baseline and Week 52]

1. Change in Bayley Scales for Infant and Toddler Development-4 (Bayley-4): Cognition Subdomain Raw Score without caregiver input [Time Frame: Baseline and Week 52], 2. Change in Symptoms of Angelman Syndrome -Clinician Global Impression of Change (SAS-CGI-C): Overall AS [Time Frame: Baseline and Week 52], 3. Change in Vineland Adaptive Behavior Scale-3 (Vineland-3): Receptive Communication Subdomain Raw Score [Time Frame: Baseline and Week 52], 4. Change in Vineland Adaptive Behavior Scale-3 (Vineland-3): Daily Living Skills, Personal Subdomain Raw Score [Time Frame: Baseline and Week 52], 5. Change in Symptoms of Angelman Syndrome - Clinician Global Impression of Change (SAS-CGI-C): Sleep Problems [Time Frame: Baseline and Week 52], 6. Change in Bayley Scales for Infant and Toddler Development-4 (Bayley-4): Fine Motor Subdomain Raw Score without caregiver input [Time Frame: Baseline to Week 52], 7. Change in Observer-Reported Communication Ability (ORCA): Overall Emerging T score [Time Frame: Baseline and Week 52], 8. Percentage of Participants with Treatment-emergent Adverse Events (TEAEs) and Serious Adverse Events (SAEs) [Time Frame: Up to Week 52], 9. Change in Vital Signs and Clinical Laboratory Results [Time Frame: Baseline and Week 52]

Age group: 18-64 years, 0-17 years Gender: Female, Male Target enrollment: 30 participants