Nonviral delivery techniques for in vivo prime editing

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Gene editing is a promising strategy for treating or even permanently curing genetic diseases. In particular, a new technique called prime editing has the potential to make small targeted insertions, deletions, and substitutions with very high potential coverage of known disease- causing mutations, and while minimizing dangerous double-stranded breaks in DNA. In order to realize this potential, robust delivery strategies must be developed to deliver prime editing tools efficiently to disease-relevant organs. One such delivery strategy is lipid nanoparticle delivery of RNA and/or protein-based prime editing components. LNPs are nonviral, nontoxic, and clinically validated delivery tools. However, there is an extremely diverse space of possible LNPs, with tens of thousands of potential lipid structures that may be useful for LNP delivery. Selecting the best possible LNP for a prime editing application, therefore, is challenging because in vitro testing is often unreliable and in vivo testing of one LNP at a time is extremely low throughput. Here, we propose to combine two scalable techniques to generate and test safe, potent LNP formulations for performing prime editing. First, we will employ combinatorial chemistry techniques to generate large libraries of biodegradable lipids for inclusion into LNPs. Second, we will introduce a new technique which we term pegRNA barcoding to screen dozens to hundreds of LNPs for successful prime editing in a single mouse. We will employ this technique to identify the best biodegradable LNPs for editing of multiple organs, including in particular the lung and the liver. Having identified the top candidates, we will proceed to use our LNPs to apply prime editing to treat mouse models of two different inherited genetic diseases: hereditary tyrosinemia type I (HTI), a liver disease, and cystic fibrosis (CF), primarily a lung disease. We will evaluate the efficiency of prime editing, the levels of undesired editing events, and phenotypic correction of these mice. The results may identify promising preclinical candidates for the treatment of HTI, CF, and many other lung and liver diseases.