Gene therapy improves vision in those with blinding disease

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British researchers report that an experimental gene therapy has shown promise in treating patients who are going blind.

The experimental therapy improved the vision of patients with a blinding eye disease during the early phase of a study that was originally launched to test only the safety of the therapy.

Yet, as physicians reported this past week, the gene therapy ended up improving the sight of the patients by putting a stop to the ongoing degeneration of their vision, as well as reversing some of the damage that led to the vision loss in the first place.

In one case, the vision improvement continued to last for two years, according to the researchers, whose study has been published in The Lancet medical journal.

Although it’s still too soon to know if the gene therapy will continue to improve vision, research leader Dr. Robert MacLaren of the Nuffield Laboratory of Ophthalmology at the University of Oxford said in a statement that “the vision improvements have been maintained” for as long as the research team has been following the patients “which is two years in one case.”

He added that the team did not expect to see “such dramatic improvements in visual acuity”, so the researchers contacted the primary opticians of the patients’ to obtain their visual medical histories prior to the start of the gene therapy trial.

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As a result, MacLaren and his team found that the visual data they received from the patients’ home opticians confirmed exactly what they had seen during the trial.

All of the patients who participated in the trial were men who have choroideremia, a genetic disease that causes deterioration of vision during childhood. The blinding disease affects males almost all of the time due to a defective gene, CHM, on the x chromosome. Females, on the other hand, have an extra x chromosome, which usually makes up for any lost function.

The National Institutes of Health report that the eye condition causes approximately 4 percent of all cases of blindness by breaking down parts of the retina, which is located in the back of the eye and reflects images. The gene therapy treatment uses a virus to transport and deliver directly into the retina a corrective gene.

Although gene therapy in general isn’t always effective for treating other parts of the body, the eye is considered a good place to start, as it allows medical professionals to see how it’s working in real time, not to mention that it can treat one eye while using the other eye to compare results.

Dr. Richard Weleber, a professor of ophthalmology who is leading researchers at Oregon Health and Science University in an attempt to treat Usher Syndrome with gene therapy, says that he thinks this latest trial is an important study.

MacLaren agrees, saying it “has huge implications for anyone with a genetic retinal disease such as age-related macular degeneration or retinitis pigmentosa, because it has for the first time shown that gene therapy can be applied safely before the onset of vision loss.”

So far, MacLaren says that 9 patients have had gene therapy treatment in one at the Oxford Eye Hospital, each of whom has different amounts of vision loss. However, MacLaren believes it’s best to treat people with a blinding disease early on, when they’re children, to prevent further damage to the eye.

SOURCE: The Lancet medical journal, Retinal gene therapy in patients with choroideremia: initial findings from a phase 1/2 clinical trial, published January 16, 2014.

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