Gene therapy injected in one eye can travel to the other eye

A gene therapy for a rare form of blindness seems to work well – but the genes injected into one eye have been found to travel to the untreated eye. The discovery has implications for safety, as well as for how the therapy’s effectiveness is measured, because such trials usually compare the treated eye’s vision with that of the untreated eye.

The experimental therapy is for a condition called Leber’s hereditary optic neuropathy, which usually affects young men and leads to progressive sight loss. It is caused by a mutation in one of the genes inside mitochondria, the energy-producing structures inside cells. This kills off cells of the retina, the patch of tissue at the back of the eye that turns light into electrical signals.

The gene therapy involves injecting a harmless virus containing the gene into the eye, where it is taken up by retinal cells. These start making the protein encoded by this gene, which passes into their mitochondria and helps preserve their remaining retina.

Eye disorders are a popular target for gene therapies, because they can...