Eloise J. Lockyer

The CRISPR (clustered, regularly interspaced, short palindromic repeats)-Cas9 (CRISPR-associated protein 9) system is a targeted nuclease technology that allows precise genome editing. Since the system was first demonstrated for use in genome editing, there has been huge interest generated in evaluating its potential for human gene therapy, and it has most recently been used to modify human embryos for the first time. The CRISPR-Cas9 system has multiple advantages in comparison to the pre-existing targeted nucleases transcription activator-like effector nucleases and zinc finger nucleases, which are discussed here. However, as a relatively new genome editing platform, safety issues such as off-target editing have yet to be fully investigated. In order to develop CRISPR-Cas9-based gene therapy, diseases amenable for targeting must first be selected, alongside appropriate and efficient delivery methods. This review addresses these challenges and current strategies for improvement, as well as the inherent socio-ethical considerations that surround the use of human genome editing.