Development of an ASO therapy for Angelman syndrome by targeting an evolutionarily conserved region at the start of theUBE3A-AStranscript

ABSTRACT Angelman syndrome is a devastating neurogenetic disorder for which there is currently no effective treatment. It is caused by mutations or epimutations affecting the expression or function of the maternally inherited allele of the ubiquitin-protein ligase E3A ( UBE3A ) gene. The paternal UBE3A allele is imprinted in neurons of the central nervous system (CNS) by the UBE3A antisense ( UBE3A-AS ) transcript, which represents the distal end of the SNHG14 transcription unit. Reactivating the expression of the paternal UBE3A allele in the CNS has long been pursued as a therapeutic option for Angelman syndrome. Here, we designed and optimized antisense oligonucleotides (ASO) targeting an evolutionarily conserved region demarcating the start of the human UBE3A-AS transcript and show that ASOs targeting this region can reverse imprinting of UBE3A in cultured Angelman syndrome neurons and throughout the CNS of a non-human primate model. Findings from this study advanced the first investigational molecular therapy for Angelman syndrome into clinical development (ClinicalTrials.gov, NCT04259281 ). SUMMARY Here, we describe the preclinical studies supporting the first investigational molecular therapy for Angelman syndrome to advance into clinical development (ClinicalTrials.gov, NCT04259281 ).