Human diseases are mainly caused by imbalances in the metabolism of important substances in life activities or imbalances in the regulation of corresponding signal pathways. A considerable part of these diseases are caused by defects in gene expression. Traditional drugs act on the protein level, and patients often need long-term medication. Gene therapy starts with DNA, the source of protein synthesis, and changes the transmission of genetic information by regulating DNA, thereby changing the properties of proteins and curing the disease from the root.

Gene therapy is the process of delivering expression units including "therapeutic genes" into the patient's body through drug carriers, so that they can exist and express therapeutic proteins for a long time. It is similar to the process of a gene transplant, so it has a long-term therapeutic effect that traditional chemical drugs or protein structure drugs cannot achieve.
The most widely used gene therapy drug carrier is the adeno-associated virus vector (AAV vector), which is widely used due to its good safety, low immunogenicity, and good tissue specificity.

Gene therapy has a wide range of applications and can treat a variety of diseases, including genetic diseases, tumors, cardiovascular diseases, nervous system diseases, immune system diseases, etc. The current hot application areas include ophthalmic diseases, nervous system diseases with genetic etiology, muscle diseases, and metabolic monogenic genetic diseases (rare diseases). As an emerging treatment method that uses modern molecular biology technology and precision medicine theory and practice, gene therapy will continue to develop in breadth and depth, and related research and applications still need to be continuously explored and improved.

One of the important advantages of AAV as a gene therapy vector is that it mediates long-term expression of the target gene. The academic community believes that after the AAV virus infects and enters the cell nucleus, the capsid disintegrates and releases its genome, synthesizing the second chain with the help of the single-stranded AAV genome of the host cell function, and undergoing intermolecular or intramolecular recombination under the drive of ITR to form a circular episome, which persists in the host cell nucleus in a form independent of the host cell chromosome. Therefore, at the cellular level, AAV-mediated expression of the target gene runs through the entire cell life cycle, which is the theoretical basis for the long-term effectiveness of AAV gene therapy.
In biological individuals, since the lifespan of non-dividing cells (such as neurons) is basically the same as the lifespan of individuals, gene therapy targeting non-dividing cells is long-lasting, even lifelong. For example, a study found that after a single injection of AAV gene drugs into the brain parenchyma of non-human primates, the target gene continued to be expressed for more than 15 years.
Compared with traditional therapies, the therapeutic effect of AAV gene therapy targeting dividing cells is also long-term.