We need light to see and now a new gene therapy is restoring sight by sort of lighting up certain people's vision.
These people are suffering from RP, or retinal pigmentosa, a group of rare genetic disorders where certain genes that encode instructions for proteins are mutated. When these proteins malfunction, the two types of cells in the retina that detect light, rods and cones, are slowly lost.
In the new treatment, the gene being targeted is RPE65. Its protein is involved in a process called the visual cycle which is triggered by light entering the eye.
The cycle begins when a molecule similar to vitamin A is converted to another molecule called all-trans retinal. This conversion tells the eye to send electrical signals that transmit images to the brain.
But for us to continue to see, the RPE65 protein has to return the all-trans retinal back into the vitamin-A like molecule so it is ready to go again. This cycle does not happen when the protein malfunctions, so the new therapy targets the protein by using an engineered virus called AAV.
It’s engineered to carry the normal form of the RPE65 gene. The engineered viruses are surgically introduced into the eye where they infect cells and begin making normal RPE65 proteins to correct the defect.
In a clinical trial involving 21 people, all showed improved sensitivity to light. Some nearly blind patients had restored sight even three years after the therapy. The treatment may be approved in 2016, but at one-hundred grand, most people can’t afford it.
But we’re excited that the treatment could benefit other similar genetic vision disorders, and that this is a gene therapy that works.