A gene therapy that deliberately infects the eye with a virus can safely preserve vision in people affected by one of the leading causes of blindness, research has shown.
In a small preliminary study, scientists used an altered common cold-type virus to carry a repair gene that combats age-related macular degeneration (AMD).
The disease is marked by abnormal blood vessels that leak fluid into the central part of the retina, or macula.
After being injected into patients' eyes, the virus penetrated retinal cells and deposited the gene, which manufactured a therapeutic protein called FLT01.
Lead researcher Professor Peter Campochiaro, from Johns Hopkins University in the US, said: "This preliminary study is a small but promising step towards a new approach that will not only reduce doctor visits and the anxiety and discomfort associated with repeated injections in the eye, but may improve long-term outcomes."
The Phase I clinical trial involved 19 men and women aged 50 and older with advanced "wet" AMD.
With the help of the gene, retinal cells were turned into "factories" making FLT01.
The scientists hope this will eliminate the need to administer repeated injections of the protein, which suppresses a natural growth-driving molecule called VEGF.
"Prolonged suppression of VEGF is needed to preserve vision, and that is difficult to achieve with repeated injections because life often gets in the way," said Prof Campochiaro.
For safety and ethical reasons, the patient group consisted of people for whom standard approved treatments were highly unlikely to restore vision.
Only 11 patients stood any chance of fluid reduction. Of those, four showed dramatic improvements after the gene therapy. The amount of fluid in their eyes dropped from a "severe" level to almost nothing.
Two other patients experienced a partial reduction in the amount of fluid in their eyes.
The findings are reported in the latest issue of The Lancet medical journal.