BEACON - Phase III Clinical Study of Rugonersen in Angelman Syndrome.

Inclusion Criteria: * Male or female and ≥ 1 year to ≤ 50 years of age at signing of the informed consent form. * Independent of the age of the participant, the participant has a parent, caregiver or legal representative (herein after referred to as caregiver) who is reliable and competent in the Investigator's judgement. The caregiver is: * Able to consent for the participant according to ICH and local regulations, * At least 18 years of age, * Willing and able to accompany the participant to clinic visits and be available to the investigational site by telephone, email, or other electronic form as needed, * Is, and will likely remain, sufficiently knowledgeable of participant's condition throughout the study to be able to respond to queries, and is willing and able to complete caregiver assessments and inform the site personnel about the participant's condition as requested. * Clinical diagnosis of Angelman syndrome. * Pre-existing medical records confirm the clinical diagnosis of AS and the molecular diagnosis with genotypic classification of either: * Mutation in the UBE3A gene, and the pathogenic or likely pathogenic variant identified, * Deletion on the maternally inherited chromosome 15q11-q13 that encompasses the UBE3A gene. * Able to comply with all study requirements. * Able to tolerate blood draws. * Able to undergo LP and IT injection, under sedation or anesthesia without intubation as deemed appropriate. * Has stable medical status for at least 4 w…