Ligand-directed targeting of genes to the site of disease

Fundamental changes in the understanding of the primary influences that govern specific gene delivery, combined with rational approaches to engineer the gene transfer vectors, are now transforming targeted in vivo gene transfer from concept to reality. Many viral-based vectors have been designed to avoid gene transfer through their native receptors and redirected to a variety of tissue- and tumor-specific receptors. Non-viral vectors have likewise been engineered to avoid nonspecific gene transfer. Future challenges include advancing these vectors into clinical testing, designing improvements to avoid innate and acquired immunity, and elucidating the mechanisms that govern their biodistribution and pharmacokinetics.