Gene therapy is based on the genome modifications by introducing nucleic acids in the cells of the patient to treat diseases. There are various different gene therapy strategies, the most common of which being to add a healthy copy of the disease-inducing gene. Other strategies consist of replacing the gene which is responsible for the disease for a healthy copy or inactivating a gene that is functioning improperly. The genetic engineering step can be achieved ex vivo or in vivo.
Gene therapy is designed for untreatable diseases or for those which require heavy treatment. These are primarily blood diseases, ocular diseases, neurodegenerative diseases, skin diseases, neuromuscular diseases or cancer.