This week, the FDA announced its approval for a new gene therapy designed to treat a rare genetic disorder that causes blindness. According to the press release, the new product is the first gene therapy to target a disorder resulting from a specific genetic mutation. This treatment offers fresh hope to those who face an inherited form of blindness.
The disease is known as biallelic RPE65-mediated inherited retinal dystrophy, which affects approximately three to four thousand people in the U.S. “RPE65” refers to a common protein found in the pigmented layer of the retina (back of the eye), consisting of a layer of cells. The primary function of this layer is to absorb light. It also protects the retina and maintains visual function by helping the eye to adapt to varying degrees of light and darkness.
When a “biallelic” mutation is present (a mutation present on two forms of the same gene, inherited from both parents), the RPE65 protein is unable to function properly. The result is a wasting away of the retina, leading to progressive sight impairment starting around age 18. In many cases, the eventual result is total, permanent blindness.
The new treatment, called Luxturna, is a product of Spark Therapeutics. The treatment is directly administered into each via injection. It replaces the defective gene with a functional copy, allowing the retina to convert light and images into electronic signals that are relayed to the brain. Clinical studies that have followed patients for four years after receiving the one-time treatment indicate that Luxturna's effects are permanent. Jeffery Marrazzo, CEO of Spark Therapeutics, says, “All the data we have today suggests it's long-lasting, if not lifelong.”
The bad news is the price tag; although the company has yet to announce pricing, company analysts anticipate that Spark will charge around $1 million for the treatment. The good news is that because of the results of the clinical study and FDA approval, U.S insurers – both public and private – are expected to cover the costs.
Current FDA Commissioner Scott Gottlieb says the approval “...marks another first in the field of gene therapy...this milestone reinforces the potential of this breakthrough approach in treating a wide-range of challenging diseases.” The agency plans to issue new guidelines next year for the research and development of new gene therapy products.
In a related story, a recent study published in Nature reports that scientists have successfully used gene editing to cure a genetic form of deafness in laboratory mice. Last month, scientists made an attempt to edit the DNA of a patient with Hunter Syndrome, a metabolic disorder. Another study in France has shown promise in the application of gene therapy in treating and curing sickle cell anemia.
Fyodor Urnov, Associate Director of the Altius Institute for Biomedical Sciences in Seattle, says, “We have entered the age where the human genome is a real drug target.” He expressed optimism that these early steps will bring new hope to patients suffering from rare genetic diseases.