miRNA-based UBE3A Unsilencing for a Potential One-Time, AAV-Mediated Gene Therapy for Angelman Syndrome

Quick Overview

Dr. Stephanie Tagliatella, co-founder and chief scientific officer of ENCODED Therapeutics, presented preclinical data on an AAV-mediated gene therapy for Angelman Syndrome at the 2023 FAST Science Summit. The therapy utilizes a vectorized microRNA approach to unsilence the paternal copy of UBE3A. The team has demonstrated success in mice, showing knockdown of the antisense transcript and upregulation of UBE3A expression. They have also seen rescue of multiple phenotypes associated with Angelman Syndrome. In human-derived induced pluripotent neurons, they have identified candidates that show robust upregulation of paternal UBE3A. The team is now working on optimizing the candidates for improved potency and selectivity and plans to move forward with non-human primate studies. This research provides proof of concept for a potential one-time, AAV-mediated gene therapy for Angelman Syndrome.

Introduction

Dr. Stephanie Tagliatella, co-founder and chief scientific officer of ENCODED, presented an overview of their preclinical data for an AAV-mediated gene therapy for Angelman Syndrome at the 2023 FAST Science Summit. ENCODED is a privately owned gene therapy company based in South San Francisco, California, with a mission to unlock the full potential of gene therapy by harnessing the power of gene regulation.

AAV Vector Engineering Platform

ENCODED has developed a vector engineering platform that optimizes the genomic components of AAV vectors to improve safety and potency. This platform is primarily focused on AAV as it has demonstrated the most clinical validation for in vivo viral vectors. However, the platform is applicable to any RNA or DNA-based therapy. ENCODED has optimized enhancer and promoter regions, effector genes, DNA binding proteins, transcription factors, and elements in the three prime region of the gene to enhance potency and selectivity.

Focus on Pediatric CNS Disorders

ENCODED’s primary focus is on pediatric CNS disorders. Their lead program is focused on SCN1A+ Dravet syndrome and will be entering the clinic next year. For Angelman Syndrome, ENCODED sought to develop a vectorized microRNA approach to unsilence the paternal UBE3A allele.

AAV Construct and Delivery

The AAV construct developed by ENCODED consists of a microRNA sequence and regulatory elements that drive expression of the delivery system. This construct is packaged into an AAV capsid and delivered to the brain through a one-time administration into the CSF space. ENCODED has extensive experience with the ICV route of administration, which is a clinically utilized route to access the CSF.

Preclinical Data in Mice

In preclinical studies using mice, ENCODED demonstrated knockdown of the antisense transcript and upregulation of UBE3A with their vectorized microRNA construct. They also observed rescue of multiple phenotypes, including body weight, hypoactivity, and seizure sensitivity.

In Vitro Testing in Human-Derived Neurons

ENCODED developed human candidates targeting the human antisense sequence and tested them in human-derived induced pluripotent neurons in vitro. They identified six candidates that showed robust upregulation of the paternal UBE3A allele, with candidate one showing nearly complete unsilencing of the paternal allele.

In Vivo Testing in Non-Human Primates

To test the approach in an in vivo setting, ENCODED delivered their candidate via a direct intercortical injection in non-human primates. They observed dose-dependent knockdown of the antisense transcript and upregulation of UBE3A. The increase in UBE3A protein was also observed in the injected region of the brain.

Enhanced Potency and Selectivity

ENCODED has been optimizing their candidates to improve potency and selectivity. Their next-generation candidates have shown enhanced potency, with higher levels of unsilencing at lower dose levels. They have also improved the specificity profile of the microRNA candidates by making genomic changes.

Next Steps

ENCODED is now taking their updated candidates into non-human primate studies. They are working towards overcoming the hurdles before filing an IND. The vectorized microRNA approach shows promise in providing a durable and stable way to restore expression of UBE3A for Angelman Syndrome.

Acknowledgements

Dr. Tagliatella acknowledged the tremendous work of the team at ENCODED, particularly Sirika Pillay, who spearheaded the project. She thanked the collaboration and privilege of working with the ENCODED team across various domains of drug development.