Toward a Small Molecule Therapy for Angelman Syndrome: Structure-Activity Relationship Studies of 3-Aminopyrazole Phenylacetamides as Paternal Ube3a Unsilencers.

Unsilencing of paternal UBE3A is presently the leading therapeutic strategy for Angelman syndrome, a neurodevelopmental disorder caused by mutation or deletion of maternal UBE3A. Previous work identified (S)-PHA533533 ((S)-3) as a small molecule unsilencer of paternal UBE3A that disrupts UBE3A-ATS, the long noncoding antisense transcript that suppresses paternal UBE3A expression in mature neurons. Initial studies demonstrated that four (S)-3 analogs possess unsilencing behavior, which spurred further interest in the 3-aminopyrazole phenylacetamide (APPA) scaffold. Here, we leveraged mouse primary neurons harboring a sensitive reporter of paternal Ube3a expression to establish structure-activity relationships between APPAs, unsilencing behavior, and undesired cellular toxicity. We uncovered compounds with improved potency and less cytotoxicity than hit (S)-3 and report a concise set of identification efforts. We demonstrate that the most promising APPAs are 3' biased in their transcriptional disruption of Ube3a-ATS. Overall, this work provides a basis for additional development of APPAs.