FDA authorized the use of gene therapy to treat congenital blindness

Published on August 24, 2019

FDA authorized the use of gene therapy to treat congenital blindness

    The use of genetic engineering for the modification of human genes under normal conditions is prohibited in almost all states, with a few exceptions. Among such exceptions now is the USA, where the FDA has allowed gene therapy to cure congenital partial or complete loss of vision, which is caused by a mutation in a particular gene.

    To carry out such therapy, it is planned to use a specialized drug Luxturna. It contains DNA with the active RPE65 gene, which, in particular, uses light-sensitive cells in the eye.

    This year, the FDA broke its own record for the number of approved methods of using gene therapy. Thus, in August, the regulator approved work with genetically modified CAR-T lymphocytes for the treatment of leukemia. In October, similar approval was made for the treatment of certain types of lymphomas. The fact is that the CAR-T method allows you to activate a person’s immunity to fight cancer tumor cells.

    In order to obtain the desired effect, genetic changes were made in the patients' lymphocytes and then reintroduced into the human body. As for the drug Luxterna, it is the first of its kind. The active component contains DNA with a normal gene, which is introduced into the human body directly, where it then replaces the mutated gene.

    This enzyme, RPE65, is formed in the cells of the retina of humans and animals. It takes part in the cycle of formation of a substance (vitamin A1), which provides the so-called visual phototransduction. So called the process of converting visible light into electrical signals in photosensitive cells. If mutations occur in both copies of the RPE65 gene inherited from father and mother by man, then the gene activity is somewhat suppressed. As a result, such a person loses the ability to react to the light, the eyes simply do not perceive the rays of the visible range. In this case, partial or total blindness occurs.

    This does not happen so often. For example, in such a large country as the United States, congenital blindness, provoked by the above mechanism, no more than two thousand people suffer. However, if the disease can be cured by genetic engineering, then why not? The first tests have already been carried out and they have shown their effectiveness.

    Luxterna contains a virus that is harmless to humans and has a normal gene. The drug is injected directly into the eyeball, after which the cells of the retina with the active gene begin to produce the named enzyme, as a result of which the vision improves. To clinical trials of the drug was involved 41 people aged 4 to 44 years. The effectiveness of the treatment after the operation was carried out by specialists according to the quality of the passage of obstacles by patients in a variety of lighting conditions. As it turned out, patients who received the drug showed better results than the control group.

    Of course, this drug has contraindications. For example, it can only be used if the patient has active cells of the retina. If not, then even this powerful tool is not able to help. In addition, the introduction of funds into the body is carried out with the help of injections, and in each eye separately. It is necessary to take a break of six days or even between injections. If you do this more often, immunity is activated, which will reject the drug. To reduce the effect of the immune response, patients are given the drug prednisone. He, in turn, is not very convenient because he has a large number of side effects. One of them is irritation of the conjunctiva, increased intraocular pressure, development of a cataract, or retinal breakdown.

    “The approval of Luxturna opens up broad opportunities for gene therapy. Patients with the RPE65 gene mutation receive the hope of restoring (albeit partial) vision, although it was almost impossible before, ”said project leader Peter Marks. Patient treatment will begin in the near future.