Limitations of Constitutive CRISPR‑Cas9 Expression and the Off‑Target Genotoxicity Bottleneck In vivo genome editing using CRISPR‑Cas9 and Prime Editor is a pivotal modality for curative treatment of chronic diseases. However, conventional gene‑editing systems retain constitutive expression after delivery, creating a persistent “blind spot” even after the intended genomic correction is achieved. This prolonged presence leads to intracellular accumulation of guide RNAs and nuclease proteins, triggering off‑target mutations, chromosomal rearrangements, and spurious genotoxicity signals—a critical technical bottleneck. The lack of a reversible, drug‑inducible mechanism to precisely control the temporal window of editing activity has long impeded the safety standards of in vivo therapeutics.

PRINCE Platform Architecture: Establishment of a Small‑Molecule‑Inducible Dual‑Gating System This study fully activated the PRINCE system to neutralize genotoxic risk associated with constitutive expression by synchronously regulating the transcriptional kinetics of the nuclease protein and guide RNA (gRNA) with small‑molecule drugs. The team engineered a fusion architecture that couples drug‑responsive promoters and allosteric control modules to both the protein backbone of the gene‑editing nuclease and its RNA encoding region. Only during a defined “golden window” of small‑molecule inducer administration does the complex rapidly assemble to correct the target sequence, and the system autonomously shuts down in a reversible manner upon drug clearance. This temporally precise control demonstrated sustained integrity, significantly suppressing false‑positive off‑target signals over a follow‑up exceeding two years in human cell lines with stable genomic integration.

Kinetic Reversal of Phenotypes via the Miniaturized Little Prince Payload and Single‑AAV Vector Delivery Furthermore, the investigators extended the PRINCE design principles from CRISPR‑Cas9 and Prime Editor to the ultra‑compact nucleic‑acid nuclease platform Little Prince, optimized for nanodelivery. They successfully packaged the entire Little Prince gene‑editing payload into a single adeno‑associated virus (AAV) vector despite its severely limited cargo capacity. In humanized mouse models, precise administration of this construct yielded a metabolic rescue in hypercholesterolemia cohorts, with average reductions of 45% in total serum cholesterol and 47% in low‑density lipoprotein cholesterol (LDL‑C). In parallel, neovascular age‑related macular degeneration (AMD) models exhibited dramatic decreases in lesion size and effective vascular leakage area, establishing a definitive therapeutic endpoint.

Establishment of a Programmable Spatiotemporal Genome‑Engineering Standard The integrated PK/PD‑driven control matrix for genome editing redefines gene‑therapy safety specifications, shifting from post‑hoc monitoring to a programmable, reversible system that computationally governs in vivo activity half‑life. By modulating the dose and temporal pulse of the small‑molecule inducer, the platform enables real‑time in silico simulation and regulation of editing efficiency within target cells, establishing a unique engineering safeguard. The characterized structural dynamics of Little Prince will serve as a computational backbone for pre‑emptively calculating CMC (Chemistry, Manufacturing, and Controls) critical thresholds in IND submissions for chronic disease therapeutics, and will function as a master reference to dramatically accelerate global regulatory timelines for next‑generation safety‑optimized nucleic‑acid nuclease pipelines.