Therapeutic CRISPR/Cas9 delivery approaches: strengths, limitations, and a roadmap for clinical translation

CRISPR/Cas9 has revolutionized genetic engineering since its repurposing as a programmable nuclease in 2012, yet its clinical translation remains fundamentally constrained by delivery barriers rather than editing efficiency. The system operates through acquisition, biogenesis, and interference mechanisms, but therapeutic application necessitates overcoming delivery challenges that are highly context-dependent. This review moves beyond a descriptive summary of 67 studies to provide a critical, barrier-focused analysis of delivery strategies. Our re-analysis of the tabulated data identifies quantitative trends across viral, non-viral, and physical platforms, evaluates trade-offs between efficiency and safety, and proposes a decision framework for vehicle selection based on target tissue and cargo type. A major focus of this review is the inclusion of recent hybrid systems (VLPs, SORT-LNPs) and the recognition that chemical modification of guide RNAs is a critical parameter for therapeutic success. A key forward-looking insight is that hybrid systems and stimuli-responsive nanoparticles are poised to dominate the next 5 years of clinical development, particularly for liver, CNS, and hematopoietic targets. Successful clinical translation of CRISPR/Cas9 will depend on context-specific delivery strategies that balance editing efficiency, safety, and clinical scalability.