Newborn Intravenous Injection of Liposomal CRISPR/Cas9 Complex Has No Incidence of Off-Targets or Tumors in Mice

<b>Background</b>: Genome editing at specific loci is an innovative therapeutic approach; however, it faces many challenges, so optimizing delivery vectors is essential to enhance the safety and efficacy of the CRISPR/Cas9 system. This study investigated whether the hydrodynamic administration of liposomal CRISPR/Cas9 complexes (LCs) in newborn mice induces off-target events or tumors. <b>Methods</b>: Liposomes were obtained through microfluidization. The CRISPR/Cas9 plasmid and a donor plasmid containing the <i>Idua</i> cDNA (alpha-L-iduronidase enzyme) were incorporated by adsorption, and complexes (LCs) were characterized regarding physicochemical properties. C57BL/6 newborn mice were divided in two groups, one received the complexes through hydrodynamic intravenous injection (n = 15) and the other was used as control (n = 15). After 21 months, mice were euthanized and organs were analyzed regarding histological characteristics. Lungs and liver were analyzed by qPCR searching for potential off-target sites in chromosomes 2, 5, 11, and 17 and on-target site in chromosome 6, identified by COSMID. Sequences were analyzed using an ICE tool for indels detection. <b>Results</b>: LCs exhibited 136 nm mean vesicle diameter with PDI below 0.15 and a zeta potential around +43 mV. Immediate biodistribution was predominant in the lungs and liver. There was no significant increase in tumor induction (20% in LCs vs. 33% in control). Molecular analyses indicated 0% off-target effects and around 3% on-target events. <b>Conclusions</b>: We conclude that this set of experiments demonstrates the potential of the chosen gRNA sequence to perform safe gene editing at the murine <i>ROSA26</i> locus, corroborating the safety of the CRISPR/Cas9 gene editing platform.