Gene therapy is an experimental technique that harnesses genes to treat or prevent disease, via the insertion of genetic material into cells to compensate for abnormal genes or to produce a beneficial protein. To enable a gene inserted directly into a cell to function, a genetically engineered carrier, known as a “vector,” is often required to deliver the gene to its destination. Some viruses can be used as vectors, carrying the new gene by infecting the cell. When used in humans, these viruses are modified so as to prevent them from causing disease.

Gene therapy is still in the experimental stage and involves significant risks, including an undesirable response by the immune system; insertion of the active gene into the wrong cells, which could harm healthy cells and result in cancer or tumor formation; and infection by the carrier virus, which could regain its original pathogenic qualities. In the past, this therapy has even led to patient deaths. It therefore remains a residual treatment, to be attempted only after all other therapy options have been exhausted, that is, in patients without any other effective therapeutic alternative. In the future, this technique might enable doctors to treat genetic disorders by inserting a gene into the patient’s cells by means of medication or a surgical procedure.

There are currently several experimental approaches to gene therapy:

•   Replacing a mutated gene that is causing disease (by failing to produce a vital protein or producing an abnormal one) with a healthy copy of that gene (to restore the protein’s activity).
•  “Deactivating” a mutated gene that is not functioning properly.
•  Introducing a new gene into the body to assist in treating or fighting off a disease.

• Experimental treatment involving not insignificant risks – i.e., a problematic risk : benefit ratio.
• Adequate informed consent – awareness of the therapy’s risks.
• Achieving genetic change by introducing genes to reproductive cells (germline gene therapy), leading to future generations inheriting the change – human control over the creation of humans (“playing God”).
• Costly treatment raises issues of (un)equal access and distributive (in)justice
• Elective use of therapy (“off label” use, contrary to medical intent) to enhance human traits such as height, intelligence, and so on.

https://ghr.nlm.nih.gov/primer/therapy/genetherapy

https://ghr.nlm.nih.gov/primer/therapy/procedures

https://ghr.nlm.nih.gov/primer/therapy/ethics

https://www.mayoclinic.org/tests-procedures/gene-therapy/details/risks/cmc-20243698