Recent advances, prospects and problems in designing new strategies for oligonucleotide and gene delivery in therapy.

The field of gene therapy has been in rapid expansion since the first submissions of gene therapy trials in the early 1990s which provided encouraging results. Since then, many gene therapy protocols have been approved for phase I clinical trials for the treatment of inherited genetic diseases and cancer. The possibility of employing gene transfer technology to treat AIDS and neurologic diseases is currently under evaluation. Many gene delivery systems have been developed for in vivo studies and therapy. The efficiency of in vivo gene transfer, however, still needs to be optimized, even though significant advances have recently been achieved in improving gene delivery, gene regulation and avoidance of immune responses. This review provides a general outline focusing on the description of the most common gene delivery systems and on their current applications in therapeutics.