Genome editing technologies, including clustered regularly interspaced short palindromic repeat (CRISPR)/CRISPR-associated protein 9 (Cas9) system, are expected to become a state-of-the-art strategy for human gene therapy. However, there are several new safety issues to be addressed before clinical use. This review article summarizes the current regulatory status of the safety assessment of genome editing for human gene therapy. In addition, with a focus on unintended genome editing by

more »

... s9 system, this review outlines the methods used to detect off-target sites, and introduces a proposed technical guidance on the safety assessment of ex vivo genome-edited cell products that have been developed by the Regulatory Science (RS) research project of the Japan Agency for Medical Research and Development (AMED) for genome editing.