ToolGen Inc. announced encouraging data from a study evaluating Campylobacter jejuni Cas9 (CjCas9), the smallest Cas9 orthologue characterized to date, for efficient genome editing in vivo. The study was led by researchers from ToolGen, Dr. Jin-soo Kim, Principal Investigator, from the Institute for Basic Science and Dr. Jeong Hun Kim from Seoul National University Hospital. The study demonstrated the ability to package the CjCas9 gene, its sgRNA sequence into a single Adeno-associated virus (AAV) vector for in vivo gene surgery. Furthermore, CjCas9 was shown to be highly specific in cleaving the target sites in the human or mouse genome in vitro, which could have significant potential precision genome editing and gene surgery. CjCas9 delivered via AAV, induced target mutations in mouse muscle cells and retinal pigment epithelium cells (RPE) with no off-target mutations detected in the genome. The study confirmed that CjCas9 targeted to the Vegfa or Hif1a gene in RPE cells reduced the size of laser-induced choroidal neovascularization, a condition leading to the formation of new blood vessels in the choroid layer of the eye. This suggests that gene surgery with CjCas9 could be a promising treatment option for age-related macular degeneration, a leading cause of blindness in adults.