ABCA4 RNA exon editing in vitro and in vivo

Abstract

Purpose : Gene therapies have begun to show their promise with the development and advancement of evolving approaches and delivery methods. However, a range of indications, such as Stargardt disease, remain out of reach for treatment due to limited AAV packaging capacity and high mutational variance within gene targets and/or narrow therapeutic indices. To address this unmet need, we have developed Exon Editor technology, by which an Exon Editor RNA molecule is designed to replace a substantial portion of a targeted disease gene’s pre-mRNA with the correct sequence via RNA trans-splicing using the host cell’s spliceosome and without the aid of exogenous protein expression, resulting in a full-length, correct mRNA molecule and protein rescue.

Methods : To unlock the full potential of this approach, we generated a high throughput, multiplexed screening platform to design, evaluate, and optimize the RNA editing efficiency of thousands of Exon Editor candidates at a time.

Results : Here, we report on Exon Editors that can efficiently replace the 5’ half of the 7 kb ABCA4 coding sequence, which covers ~60% of known patient mutations, resulting in protein rescue in vitro in an engineered mutant cell line, as well as in Non-Human Primate (NHP) retina following subretinal injection of an AAV-encoded Exon Editor construct.

Conclusions : As we continue to work toward realizing the full potential of RNA exon editing while extending it to a number of additional indications, this report demonstrates the translational viability of this therapeutic strategy.

This abstract was presented at the 2023 ARVO Annual Meeting, held in New Orleans, LA, April 23-27, 2023.