A Study of the Safety and Tolerability of GTX-102 in Children With Angelman Syndrome

Inclusion Criteria: * Signed informed consent from parent(s) or legal guardian(s) * Documented genetic confirmation of full maternal UBE3A gene deletion causing AS in the region of 15q11.2-q13 including class I, II or III * Stable seizure control (defined as clinically stable with no changes in antiepileptic medications over the prior 1 month before the screening visit, other than weight associated dose adjustments) * Able to ambulate independently, or with an assistive device (note, a child whose primary means of mobility is by wheelchair is excluded from the study) * Platelet count, prothrombin time / international normalized ratio, and partial thromboplastin time within 1.2 x the normal limits * Normal renal function with serum creatinine and spot urine protein ≤ 1.4 x the upper limit of normal (ULN) * Normal hepatic function with total bilirubin, aspartate aminotransferase, alanine aminotransferase, and alkaline phosphatase ≤ 1.4 x ULN. Exception: levels ≤ 2 × ULN are acceptable if due to anti-epileptic drugs (AEDs) or Gilbert syndrome * Willing and able to comply with scheduled visits, drug administration plan, laboratory tests, study restrictions, and all study procedures, including LP procedure * Able to tolerate the anesthetic regimen, if required for LP procedure * A female patient is eligible to participate if she is not pregnant, not breastfeeding, and at least one of the following conditions applies: Female of non-childbearing potential (ie, pre-menarche), Female…