Ten years ago, a biotech startup called Advanced Cell Technology (ACT) began trying to create retinal cells from human embryonic stem cells. Because this newly discovered type of cell could both replenish itself and differentiate into any cell type in the body, it was seen as an ideal source of replacement tissue. This year, after spending $20 million on its quest, the company will begin its first human tests of the treatment. ACT won approval from the U.S. Food and Drug Administration this week to start clinical trials of an experimental treatment for age-related macular degeneration, the most common cause of blindness in people older than 60.
It is only the third clinical trial of an embryonic-stem-cell-based therapy to be approved by the FDA. ACT won permission to test the same therapy in patients with a rare genetic disorder related to macular degeneration last fall, and a second company, Geron, began testing a cell therapy for spinal-cord injury last year. However, because macular degeneration is so common—roughly 17 million Americans suffer from the disease—ACT’s new therapy has the biggest potential impact on patient health. No treatments are now available for the so-called dry form of macular degeneration, which accounts for 90 percent of cases.
“If you can intervene early and preserve vision, that’s a major accomplishment,” says Raymond Lund, a researcher at the Casey Eye Institute at Oregon Health Sciences University, who directed some of the animal studies of the therapy.
ACT’s treatment replaces a type of retinal cell called retinal pigment epithelium, which begins to deteriorate early in the course of the disease. These cells help support the photoreceptors that translate light signals from the environment into electrical signals for the brain to process. Without healthy retinal pigment epithelium, the photoreceptors begin to sicken and die, causing loss of vision.
To create the cells, researchers at ACT grow large vats of embryonic stem cells and then differentiate them into retinal pigment epithelium, a process that takes about four to five months. The cells are then injected into the eye. Tests in rodents with similar retinal degeneration show that the cells can slow deterioration and improve vision. “The cells wind up in the back of the eye, as they should, and are able to sustain vision,” says Lund.
The clinical trial of 12 patients will initially assess whether it is safe to inject the cells, but clinicians will also test such things as the patients’ visual acuity and their eyes’ electrical function, the retinal equivalent of an EKG.