Lipid nanoparticle-based ribonucleoprotein delivery for in vivo genome editing

The clustered regularly interspaced short palindromic repeats (CRISPR)-associated (Cas) system is a technology that is used to perform site-specific gene disruption, repair, and the modification of genomic DNA via DNA repair mechanisms, and is expected to be a fundamental therapeutic strategy for the treatment of infectious diseases and genetic disorders. For clinical applications, the non-viral vector-based delivery of the CRISPR/Cas ribonucleoprotein (RNP) is important, but the poor efficiency of delivery and the lack of a practical method for its manufacture remains as an issue. We report herein on the development of a lipid nanoparticle (LNP)-based Cas RNP delivery system based on optimally designed single stranded oligonucleotides (ssODNs) that allow efficient in vivo genome editing. The formation of sequence-specific RNP-ssODN complexes was found to be important for the functional delivery of RNP. Furthermore, the melting temperature (Tm) between sgRNA and ssODN had a significant effect on in vivo gene knockout efficiency. An ssODN with a high Tm resulted in limited knockout (KO) activity while that at near room temperature showed the highest KO activity, indicating the importance of the cytosolic release of RNPs. Two consecutive intravenous injections of the Tm optimized formulation achieved approximately 70% and 80% transthyretin KO at the DNA and protein level, respectively, without any obvious toxicity. These findings represent a significant contribution to the development of safe in vivo CRISPR/Cas RNP delivery technology and its practical application in genome editing therapies.