Gene therapy treats blindness

For patients with choroideremia a rare form of progressive blindness there are no current treatment options that can help stop their visual degeneration. But now a new innovative procedure may be the key.

In a new study published in The Lancet, researchers used a novel gene therapy technique on choroideremia patients, which helped restore some of the sight they had already lost over the years. Gene therapy involves injecting patients with a vital gene that is either missing or defective in their genetic code.

Gene therapy is exciting; its a new type of medicine, lead author Robert MacLaren, a professor at the University of Oxford, told FoxNews.com. And what were doing is it on a very small scale, because were looking at a very straightforward gene to replace.

Caused by a mutation in the CHM gene on the X chromosome, choroideremia causes progressive blindness due to degeneration of the choroid, retinal pigment epithelium and retina. Patients with this disease can start their lives with perfect vision, but eventually start to experience problems with light sensitivity and peripheral vision as they age.

The condition, which affects 1 in every 50,000 people, ultimately leads to the death of the photoreceptor cells in the retina causing complete blindness in middle age.

Its like looking down through a telescope at a small central island of vision, MacLaren explained of the disorder. And by the time theyre in their 40s and 50s, they lose vision completely.

Because choroideremia is caused by a defect in a single gene, MacLaren believed that gene therapy could hold promise for patients with this form of progressive blindness. Additionally, because the cellular degeneration occurs so slowly, the researchers had a large window of opportunity in which they could test their treatment before complete visual loss occurred.

In order to fix the mutation found in choroideremia patients, MacLaren and his colleagues genetically altered an adeno-associated virus (AAV), so that it carried a corrective copy of the CHM gene.

The virus is a small biological organism, and its very good at getting into cells, MacLaren said. But rather than deliver the viruss DNA, weve taken out most of the viral DNA and instead put in the missing gene. So it releases the DNA into the nucleus its a single stranded DNA with the missing [CHM] gene.

The researchers injected their engineered virus into the retinas of six patients between the ages of 35 and 63, all of whom were experiencing different stages of choroideremia. Four of the patients still had good eyesight, though they had almost no peripheral vision, and the other two patients had already started to experience vision loss.

Read the original here:
Gene therapy treats blindness