Researchers at the University of Oxford have carried out the world’s first gene therapy operation to tackle the root cause of age-related macular degeneration (AMD).
An 80-year-old woman with AMD is the first of ten people to receive the treatment. The procedure was carried out at the John Radcliffe Hospital by Professor Robert MacLaren, Professor of Ophthalmology, in a clinical trial (FOCUS) sponsored by Gyroscope Therapeutics. It is too early to know if the patient’s sight loss has been halted, but her vision and all that of all other subjects will be closely monitored. This first stage of the trial is primarily designed to check the safety of the procedure.
The operation involves detaching the retina and injecting a solution containing a benign virus into the retinal pigment epithelium (RPE) layer underneath. The virus contains a modified DNA sequence, which infects cells and corrects a defect in the CF-1 gene that causes AMD. Ideally, if successful, the therapy would need to be performed but once, as the effects are thought to be long-lasting.
A key factor in AMD is the complement system, a system of proteins in our immune system that fights bacteria. In macular degeneration, these proteins are over-active and start to attack the retinal cells, similar to how they would attack bacteria.
Professor MacLaren explains:”When the virus opens up inside the retinal cell it releases the DNA of the gene we have cloned, and the cell starts making a protein that we think can modify the disease, correcting the imbalance of the inflammation caused by the complement system.”
“The idea of this gene therapy is to ‘deactivate’ the complement system, but at a very specific point at the back of the eye, so the patient would otherwise be unaffected by it.” If successful, it is hoped that gene therapy can be used in the future on patients with early AMD to halt the disease before their vision has started to deteriorate.
It is important to emphasize that this study is a very early-stage intervention that will not restore sight, but it is expected to prevent further deterioration. Additionally, the defective CF-1 gene occurs in only about five percent of AMD patients, so the number of candidates for the treatment is relatively small. Still, this is a very important proof-of-concept study that holds a great deal of promise for the future.