FDA approves gene therapy for childhood blindness

Scientists have made a major advancement in the field of genetic medicine with the approval of the first gene therapy for an inherited eye disease. The new treatment improves the sight of patients with a rare form of childhood blindness, called retinal dystrophy.

Although more than 200 types of faulty genes can cause retinal dystrophy, the therapy, called Luxturna and made by Spark Therapeutics Inc., has been approved for children and adults who have the inherited condition due to a particular mutated RPE65 gene. The faulty gene is responsible for severe visual impairment starting from infancy that then progresses to the gradual loss of peripheral and central vision and eventually to blindness.

The one-time treatment is injected with a microscopic needle into the eye to deliver healthy versions of the gene to the retina. In order to be a candidate for the new therapy, patients need to first be tested to determine whether the cause of their blindness is indeed a mutation of the RPE65 gene.

The study measured changes in the vision of 31 patients based on their ability to navigate an obstacle course in low light. The group who received the therapy had significant improvements in completing the course compared to a control group.

The treatment’s long-term effectiveness, however, remains unclear. William Hauswirth, an ophthalmology professor at the University of Florida College of Medicine who worked on developing the therapy, noted that one study found that most patients' vision regresses to what it was before therapy after about six years, while patients that were enrolled in the key study had not seen any deterioration in their vision for as long as four years. Some reported risks of the treatment include cataracts, elevated eye pressure, retinal tears and holes, and inflammation.

Despite the mixed results, the CEO of Spark Therapeutics, Jeffrey Marrazzo, said to CBS news, “All the data we have today suggests it’s long-lasting, if not lifelong.” 

Dr Cosmos O Mangunsong, an Ophthalmologist Vitreoretina specialist at the Jakarta Eye Center, who was not part of the research, told Global Health and Travel that, “While this condition is caused by a specific inherited gene, there are good chances that an offspring with this mutated gene could grow up having healthy eyesight. In fact, some people with RPE65-related diseases could have healthy parents and siblings. This is because there are many other factors involved beside one specific mutation of one gene that causes the condition.”

He recommends parents do a genetic test of their offspring to detect whether an RPE65 mutation exists. If it does, it’s best to first see whether any symptoms arise before seeking treatment. Dr Mangunsong believes early detection might help the condition’s progress.

"Today's approval marks another first in the field of gene therapy, both in how the therapy works and in expanding the use of gene therapy beyond the treatment of cancer to the treatment of vision loss. This milestone reinforces the potential of this breakthrough approach in treating a wide range of challenging diseases," FDA Commissioner Scott Gottlieb, M.D., said in a statement.

This story was originally published in the Global Health and Travel issue of March-April 2018.