A zinc finger nuclease (ZFN) is an engineered molecular tool used for targeted gene editing, composed of a zinc finger protein (ZFP) DNA-binding domain — designed to recognize a specific genomic sequence — fused to the nuclease domain of the FokI restriction enzyme, which introduces a double-strand break (DSB) at the target site. ZFNs were among the first programmable gene editing platforms developed, preceding TALENs and CRISPR-Cas9, and have been applied in cell line development, ex vivo gene therapy, and the engineering of therapeutic cell populations such as CAR-T cells and hematopoietic stem cells (HSCs). Although largely superseded in research settings by CRISPR-Cas9 due to its greater simplicity and flexibility, ZFNs remain relevant in clinical gene therapy programs where their intellectual property landscape and established safety profile offer specific advantages.
