Scientists believe they may be on the cusp of developing a possible cure for some types of blindness.
Several potential fixes—including gene therapy, stem-cell therapy and a modified version of vitamin A—are currently being tested in people with a rare eye disorder called Stargardt disease.
The work, if it pans out, could pave the way to treat the most common type of vision loss known as age-related macular degeneration, scientists say. An estimated 4.2 million Americans are blind or visually impaired, a number that is expected to increase 70% in the next two decades as the population ages. (Check out this blog post for resources to keep track of developments in research.)
“It’s a fundamental breakthrough,” Paul Sieving, director of the National Eye Institute, part of the National Institutes of Health, says about the latest research. “These opportunities didn’t exist 10 years ago,” he says.
It isn’t clear whether the experimental therapies will work. The clinical testing is still at an early stage. And many prospective treatments that show promise in animal trials later fail when studied in people.
The latest developments aimed at halting, or even reversing, vision loss follow decades of research into what causes people to lose their sight. Blindness can have many origins. Scientists have identified nearly 200 genes that play a role in vision loss due to degeneration of the retina, which is located at the back of the eye and contains millions of light-sensitive cells known as rods and cones.
Scientists also have gained a better understanding of the complex biochemical interactions involved in eyesight, says Eric Pierce, director of the Massachusetts Eye and Ear Infirmary’s Ocular Genomics Institute. Potential treatments triggered by this research have shown promise in preliminary testing in animals. Now, clinical trials in people are under way.
Stargardt disease affects some 30,000 Americans. In children, it is the leading cause of degeneration of the macula, part of the retina. There is currently no effective treatment. Scientists say Stargardt is a good candidate to begin looking for a blindness cure because it is linked to a single gene, thus making it relatively easy to target. Evidence suggests that age-related macular degeneration and Stargardt in part share similar origins.
The disease is caused by the body’s inability to properly process vitamin A, which provides the fuel for photoreceptor cells in the eye to sense light. In a normally functioning eye, vitamin A, once used up, is pumped out of the cell and recycled. In Stargardt, because of a defective gene known as ABCA4, vitamin A remains trapped in the cells in clumps. Retinal cells eventually die and vision is lost.
In his laboratory, Ilyas Washington, an assistant professor of ophthalmology at Columbia University Medical Center in New York, sketched for a visitor the molecular structure of the dangerous clumps of vitamin A that remain trapped in the retinal cells.
By identifying the part of the vitamin A molecule where the clumping takes place, Dr. Washington was able to devise a “better” molecule that doesn’t clump as readily but still performs its needed role in the retinal cells. Administering the rejiggered vitamin A to animals with the Stargardt gene defect showed promise, he says.
Alkeus Pharmaceuticals, in Boston, licensed the technology from Columbia University and expects to begin testing pills containing the modified vitamin A in as many as 100 patients in an early-stage trial that could start early next year.
Leonide Saad, Alkeus’s chief executive, says he doesn’t know at this point whether the pills can restore lost eyesight. But if given early enough, he says he believes they could halt the further deterioration of vision. “We [could] prevent you from going blind,” he says. Dr. Washington doesn’t receive compensation from Alkeus but could receive a financial reward from Columbia if the technology succeeds, Alkeus says.
Advanced Cell Technology, in Santa Monica, Calif., is testing 24 patients with Stargardt and 12 patients with the most common type of age-related macular degeneration to see whether injecting healthy retina cells can improve vision.
The firm says it has developed a technology allowing it to create the retina cells from human embryonic stem cells without destroying embryos. So far in the early-stage trial, nine Stargardt patients have undergone the surgery, and some have improved their vision, says Gary Rabin, the company’s chief executive. He says one patient who could only make out her hand before the surgery, was able to count her fingers within a few weeks after the procedure. She could also see five or more letters on an eye chart, he says.
British firm Oxford BioMedica OXB.LN -6.40% is studying a gene therapy that injects Stargardt patients with a healthy ABCA4 gene. An early-stage trial to test the approach in as many as 28 patients began last year. So far, there are no signs of side effects from the gene therapy in at least four patients who have undergone the surgery, says Stuart Naylor, the company’s chief scientific officer.
“It’s really exciting times and [provides] a lot of hope for people with retinal degeneration,” says Stephen Rose, chief research officer at the Foundation Fighting Blindness, a nonprofit that funds research for retinal degenerative diseases.
Edward Babin, of Berwyn, Penn., says he is hopeful the drug development work can help his two sons. Both boys, now ages 19 and 16, were diagnosed with Stargardt disease a few years ago and had to stop playing football and ice hockey after their vision deteriorated, Mr. Babin says. They can’t watch television, or use a computer without special software.
“When they were diagnosed, we were told, ‘I’m sorry, but your sons are going to be blind,’ ” Mr. Babin says. “Now, I’m convinced they’re going to be functional people by the time they’re 30 years old.”
Researchers are also exploring other causes of blindness to develop possible cures. In one study, gene therapy is being tested on patients who are legally blind as a result of a mutation in a gene known as RPE65. This defect causes one form of a rare eye disease called Leber’s congenital amaurosis.
In a first round of testing that finished in 2009, 12 patients, ages 8 to 45, received an injection of corrected genes in one eye. Nearly half regained enough eyesight to no longer be legally blind. None of the patients suffered from side effects from the gene therapy. Eleven of the patients are now receiving the gene therapy in their other eye, in a second round of testing expected to finish in the fall.
“I think it’s going to be a steppingstone” to the application of gene therapy to other eye diseases because “it’s basically demonstrated that the general approach that’s used is safe,” says Jean Bennett, one of the study’s leaders who is a professor of ophthalmology at the University of Pennsylvania.
Write to Jonathan D. Rockoff at firstname.lastname@example.org
A version of this article appeared July 24, 2012, on page D1 in the U.S. edition of The Wall Street Journal, with the headline: Closing In on a Cure for Vision Loss.