Precision of Gene-Editing Technology and Challenges in In Vivo Delivery: Opening New Horizons for Treating Intractable Genetic Diseases
Background
Genome therapy has established itself as a strategy to transcend the limitations of conventional symptomatic treatments by directly correcting molecular-level abnormalities that serve as the fundamental cause of diseases. In the past, treatment for genetic diseases was limited to the continuous external administration of deficient proteins or the simple supplementation of defective genes, making a complete cure difficult to achieve. First and second-generation genome editing tools, such as Zinc Finger Nucleases (ZFN) and TALEN, also showed clear limitations in clinical scalability due to complex protein design processes and low efficiency.
In this context, the emergence of CRISPR/Cas9 technology has shifted the paradigm in the field of genome editing. This system, composed of guide RNA (gRNA) that recognizes target sequences and the Cas9 protein, which acts as a DNA cleavage enzyme, began to attract intense attention from both academia and industry due to its excellent programming convenience, simple structure, and high editing precision. This marks a turning point in the introduction of molecular platforms capable of permanently modifying genetic information into full-scale clinical research.
Key Findings
The CRISPR/Cas9 platform has demonstrated therapeutic potential in precisely correcting causative mutations in various genetic diseases caused by single-gene defects. Notably, therapeutic efficacy has been confirmed across a wide range of fatal genetic diseases, including sickle cell anemia and beta-thalassemia caused by hematopoietic stem cell mutations, as well as familial hypercholesterolemia, phenylketonuria, muscular dystrophy, and cystic fibrosis. It has been observed that the mechanism of precisely cutting specific defective gene loci and replacing them with normal sequences functions in numerous animal models and early-phase human trials.
Technological evolution has progressed toward reducing the risk of cellular damage associated with double-strand breaks (DSB). Representative examples include base editing, which substitutes specific single bases without fully cutting the DNA strands, and prime editing, which precisely rewrites dozens of bases without unintended insertions or deletions by combining reverse transcriptase. These next-generation technologies have dramatically increased editing precision while suppressing genomic damage.
On the other hand, technical obstacles preventing integration into clinical practice still exist. Off-target effects, where non-target similar sequences are mistakenly cleaved, and unintended sequence insertions due to the randomness of endogenous DNA repair pathways remain significant risk factors. Challenges to be addressed also include the immunogenic response induced by the bacteria-derived Cas9 protein within the body, as well as liver toxicity and decreased delivery efficiency occurring during the administration of delivery vehicles such as Adeno-Associated Virus (AAV).
Significance and Outlook
Gene scissors technology has moved beyond the proof-of-concept stage and entered a phase of fundamentally restructuring the treatment pathways for major diseases. The focus is shifting from the initial trend of concentrating solely on target sequence cleavage toward complex platforms that maximize in vivo safety and precision. Beyond ex vivo treatment methods, in which genes are edited outside the body and then re-injected, in vivo gene-editing therapies, which involve directly injecting gene-editing tools into tissues within the body, are gradually coming into focus.
The prevailing assessment is that the success of future commercialization depends on the speed of advancement in delivery vehicle engineering. Efforts to improve viral vectors that suppress immune responses and develop targeted tissue delivery systems using lipid nanoparticles (LNPs) are actively underway. It is expected that the transition to routine clinical practice will proceed smoothly when accompanied by the establishment of long-term safety data to track genomic stability over time after treatment administration and the establishment of ethical standards.
Gene therapy has transformed modern biomedical research by enabling curative strategies that target the molecular basis of disease. Among genome-editing technologies, the CRISPR/Cas9 system has emerged as a versatile and efficient platform due to its programmability, simplicity, and precision. This review summarizes the evolution of gene therapy and highlights the therapeutic potential of CRISPR-based genome editing. CRISPR/Cas9 has demonstrated significant potential in correcting disease-causing mutations across multiple inherited disorders, including sickle cell disease, Ξ²- thalassemia, familial hypercholesterolemia, phenylketonuria, muscular dystrophies, and cystic fibrosis. Emerging technologies such as base editing and prime editing further improved editing precision and reduced unintended genomic alterations. However, challenges including off-target effects, DNA repair pathway bias, immune responses, and vector-associated toxicities remain major limitations. The review highlights the rapid progress of CRISPR-mediated therapeutics and emphasizes the importance of improving editing accuracy, delivery efficiency, and long-term safety. Advances in vector engineering and genome-editing platforms are expected to overcome current technical and ethical barriers, facilitating broader clinical applications. CRISPR/Cas9 and related genome- editing technologies represent promising disease-modifying and potentially curative therapeutic approaches. Continued optimization of precision, safety, and delivery systems will be essential for successful translation into routine clinical practice.
This research presents a concrete pathway to transition the treatment of rare single-gene diseases, previously classified as incurable, from symptomatic therapy to a 'one-shot cure' model. For example, instead of the complex ex vivo culture process of collecting a patient's hematopoietic stem cells, editing genes in a sterile facility, and then re-transplanting them, a representative application scenario is the intravenous injection of base-editing complexes loaded into lipid nanoparticles to directly correct genetic mutations in liver or muscle tissue. This marks a turning point that significantly reduces the lengthy cell culture period and high production costs, while drastically lowering the economic and physical burden on patients who have relied on long-term therapeutic administration.