On-target and Off-target Activities of CRISPR Therapeutics Across Scales
Recent FDA-approved gene editing therapies illustrate not only the transformative potential of CRISPR biotechnologies in treating a broad range of diseases but also the spectrum of possible molecular variations CRISPR therapeutics can adopt. These include exagamglogene autotemcel, an ex vivo Cas9-mediated therapy for hemoglobinopathies, and kayjayguran abengcemeran, an in vivo therapy using a PAM-altered, base-editing Cas9 variant for an ultra-rare metabolic disorder. Together, these therapies underscore how far CRISPR has advanced beyond its original use as a tool in biological/biomedical research. Here, we argue that as CRISPR biotechnologies advance beyond the relative simplicity of in vitro applications, our understanding must also evolve to address the challenges of optimizing “on-target” and “off-target” mutational activities across the diverse contexts in which they occur.