Therapeutic Gene Editing

Genome editing, alternatively known as gene editing, allows manipulation of genetic material in a living organism in order to develop means to treat genetic, infectious, or other acquired diseases. Here, customized DNA cutting follows natural DNA repair resulting from either precise cuts, gene insertions, deletions, partial, or full sequence replacements in specific target areas of the host genome. Low recombination rates and random integration into undesired genomic loci restricted broader application. To overcome such limitations in preclinical and clinical studies, researchers first identified the highly targeted genome engineering systems, the zinc finger nucleases (ZFNs) and transcription activator-like effector nucleases (TALENs), which failed in broader use, as each required protein reengineering for site-specific targeting. Ultimately, the cloning and protein engineering difficulties of ZFNs and TALENs sped the development of clustered regularly interspaced short palindromic repeats (CRISPR). CRISPR-Cas-nuclease-based technologies remain the most revolutionized gene-editing system available and have shown early success in genome editing. CRISPR technology has cured patients of certain genetic diseases, but not all patients can receive it due to cost and accessibility. CRISPR technology has been successful in treating a pediatric patient with T-cell acute lymphoblastic leukemia, showing feasibility of its use for cancer immunotherapy. For the human immunodeficiency virus type one (HIV-1), CRISPR technologies were successfully applied in animal model systems because of its unique RNA-based reprogramming system. The translation from animals to humans for HIV-1 infection remains in process due to a need for advanced delivery to virus target cells. The delivery of CRISPR-Cas9 cargos influences therapeutic efficacy but remains a limitation. Safe and effective delivery methods for gene editing include viral and non-viral-based vectors. Use of non-viral vectors requires that the gene-editing payload specifically reach its desired cellular designation, be protected from large-scale enzymatic degradation, and show no off-target toxicities. These challenges remain active areas of research activities.