Rapid generation of conditional KO mice for in vivo target safety assessment

Abstract

Target safety assessment (TSA), which identify toxicity hazards as drug targets and consider countermeasures, in the early stage of drug development is important to efficiently generate development candidates and increase the success rate of drug development. However, in the early stage, there are often no tool compounds, and TSA is limited to in silico TSA using databases and existing search tools. The creation of gene-knockout mice (KO mice) or conditional KO mice (cKO mice) is a possible option, but the former involves the concern of fetal lethality, while the latter issue requires a very long time using the common Cre/loxP system. Therefore, we have developed a technology that can delete target gene easily in adult mice by combining adeno-associated virus (AAV) and genome editing technology. In experiments targeting blood coagulation factor 9 (F9), whose function in vivo is known, the prolongation of APTT, which is a phenotype observed in F9 gene-deficient mice, was observed about one month after induction of gene deletion by AAV infection. Although there remain the challenges that KO cannot be expected in organs and tissues that cannot be effectively infected with AAV, it was considered that the technology can generate cKO mice for any gene in a short term.