Gene therapy: concepts and methods. Few applications so far.

(1) Gene therapy consists of inserting foreign genetic material into a patient's cells to correct a health disorder; (2) Only a fraction of gene therapy trials involve hereditary single-gene disorders. Most trials focus on acquired disorders such as cancer and cardiovascular disease; (3) The therapeutic gene can be delivered directly into the target organ or the general circulation, or alternatively into cells that are first isolated from the patient and then reinjected; (4) One of the main problems with gene therapy is finding an appropriate vector (viral or non-viral) that is both effective and safe. Most currently available vectors confer only weak and transient therapeutic gene expression. In addition, many carry major risks such as immunological disorders and oncogenicity; (5) In early 2009, only one therapeutic gene product is commercially available, in China.