There are several diseases that are caused by one or more genetic defects without specific treatment. These diseases can be congenital, such as Duchenne syndrome and thalassemia, or diseases that arise during a person’s life, such as various types of cancer. Since there is no specific treatment for genetic diseases, for these patients, treatment strategies are only to maintain their survival and prolong their life, which is very expensive and imposes a lot of cost on the health system and has a lot of social effects. For this reason, many successful studies have been conducted to investigate whether genetic defects can be repaired with gene therapy. Gene therapy can be defined as making changes in the genetic material inside the nucleus of cells, which is called DNA. This modification is done by inserting genetic material into cells, usually through vectors. Some modified viruses that do not cause disease are often used as vectors because they can transmit the new gene by infecting cells through viruses such as retroviruses, adenoviruses, and adenoviruses. The most well-known gene therapy technology is Car-T Cell Therapy, in which the infected patient’s white blood cells are infected with the virus ex-vivo. These modified T cells are multiplied in the laboratory and returned to the patient. Chemotherapy is used before re-injection of engineered T cells to prevent rejection by the immune system. These new CAR T cells identify and destroy specific cancer cells that express these types of receptors. Kymriah is the first CAR T cell therapy approved by the FDA in August 2017 for the treatment of a specific type of ALL in patients under 25 years of age. This was a promising step towards the treatment of cancer, end-stage disease and rare diseases.