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

## TL;DR

Injecting CRISPR/Cas9 in newborn mice via liposomes did not cause tumors or off-target effects, suggesting safe gene editing.

## Contribution

Demonstrates the safety of liposomal CRISPR/Cas9 delivery in newborn mice with no off-target effects or tumor induction.

## Key findings

- Liposomal CRISPR/Cas9 complexes showed no significant tumor induction compared to controls.
- Molecular analysis revealed 0% off-target effects and about 3% on-target gene editing events.
- Histological and qPCR analyses confirmed the safety of the gene editing approach.

## Abstract

Background: 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. Methods: Liposomes were obtained through microfluidization. The CRISPR/Cas9 plasmid and a donor plasmid containing the Idua 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. Results: 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. Conclusions: We conclude that this set of experiments demonstrates the potential of the chosen gRNA sequence to perform safe gene editing at the murine ROSA26 locus, corroborating the safety of the CRISPR/Cas9 gene editing platform.