Carlene Knight’s vision was so bad that she couldn’t even maneuver around the call center where she works using her cane. But that’s changed as a result of volunteering for a landmark medical experiment. Her vision has improved enough for her to make out doorways, navigate hallways, spot objects and even see colors. Knight is one of seven patients with a rare eye disease who volunteered to let doctors modify their DNA by injecting the revolutionary gene-editing tool CRISPR directly into cells that are still in their bodies. Knight and [another volunteer in the experiment, Michael Kalberer] gave NPR exclusive interviews about their experience. This is the first time researchers worked with CRISPR this way. Earlier experiments had removed cells from patients’ bodies, edited them in the lab and then infused the modified cells back into the patients. […]
CRISPR is already showing promise for treating devastating blood disorders such as sickle cell disease and beta thalassemia. And doctors are trying to use it to treat cancer. But those experiments involve taking cells out of the body, editing them in the lab, and then infusing them back into patients. That’s impossible for diseases like [Leber congenital amaurosis, or LCA], because cells from the retina can’t be removed and then put back into the eye. So doctors genetically modified a harmless virus to ferry the CRISPR gene editor and infused billions of the modified viruses into the retinas of Knight’s left eye and Kalberer’s right eye, as well as one eye of five other patients. The procedure was done on only one eye just in case something went wrong. The doctors hope to treat the patients’ other eye after the research is complete. Once the CRISPR was inside the cells of the retinas, the hope was that it would cut out the genetic mutation causing the disease, restoring vision by reactivating the dormant cells.
The procedure didn’t work for all of the patients, who have been followed for between three and nine months. The reasons it didn’t work might have been because their dose was too low or perhaps because their vision was too damaged. But Kalberer, who got the lowest dose, and one volunteer who got a higher dose, began reporting improvement starting at about four to six weeks after the procedure. Knight and one other patient who received a higher dose improved enough to show improvement on a battery of tests that included navigating a maze. For two others, it’s too soon to tell. None of the patients have regained normal vision — far from it. But the improvements are already making a difference to patients, the researchers say. And no significant side effects have occurred. Many more patients will have to be treated and followed for much longer to make sure the treatment is safe and know just how much this might be helping.