Back in August, the FDA approved the first gene therapy for general use in the United States. That particular treatment, for cancer, was beset by controversy due to its exorbitant price tag and potential side effects. Now another gene therapy is on the cusp of approval, this time to treat a form of hereditary blindness. If given the tick by the FDA, this therapy could pave the way for a whole host of treatments for genetically-based vision problems.

The gene therapy focuses on a rare inherited retinal disease called Leber congenital amaurosis (LCA), which is caused by a mutation in one of 19 particular genes. The therapy focuses in one specific gene called RPE65. A healthy version of that gene is attached to a genetically modified harmless virus and injected into a patient's eyes.

The treatment is currently undergoing final phase 3 clinical trials after nearly a decade of research and the early results have been excitingly positive. Data from the first phase 3 trial showed 93 percent of subjects (27 out of 29) displayed "meaningful improvements in their vision."

"These are kids who could not walk through a room in normal light, and who were absolutely paralyzed in dim light," says study leader Stephen Russell. "Now they're walking around markedly better."

The final FDA approval decision is hoped to come by January 2018, and back in October an advisory panel unanimously endorsed the efficacy of the treatment. The FDA doesn't have to follow the advice of this expert panel, but it traditionally does.

The gene therapy focuses on a rare inherited retinal disease called Leber congenital amaurosis(Credit: paulistano/Depositphotos)

While this particular therapy is not a complete cure, and it is targeted at a rare genetic disease, many hope it is the first in a new wave of gene therapies directed at a wide variety of occular diseases. There are over 225 known genetic mutations that cause blindness, and the genetically modified virus used in this particular treatment can likely be used as a delivery mechanism in treatments for a great majority of those conditions.

If this therapy is ultimately approved it will certainly be a landmark for modern gene therapy. Unlike the prior cancer therapy approved in August, which concentrates on genetically modifying immune cells, this treatment will be the first to replace, or essentially fix, specific missing and mutated genes that directly cause disease.

The early trial results were published in the journal The Lancet.

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