Scientists have used a new method to edit genes inside the body for the first time. Until now, doctors performed gene editing in the lab and then injected the modified genes back into the patient. But the results of such procedures may not last, and the technique is not specific: Scientists cannot control exactly where the modified gene will nestle into the patient’s DNA. The lack of specificity can cause unintended results like cancer.
Using the new editing procedure, researchers inserted DNA instructions into a virus that they then injected into a 44-year-old patient suffering from Hunter syndrome, a serious metabolic disease in which a gene that produces an enzyme to break down carbohydrates is missing. The virus carried the DNA instructions to the patient’s liver, where cells used them to make proteins that acted like genetic scissors and cut the DNA, allowing the new gene to slip in. The procedure only needs to correct 1 percent of the liver cells to cure the disease, the researchers said in a statement.
The technique is precise and the DNA modification is permanent. The virus will not invade eggs and sperm or alter future generations because the researchers built in safeguards to prevent it from working anywhere but in the liver. Even so, the procedure is not without risks: Some experts fear the virus could provoke an immune system attack or the modified gene might cause unforeseen effects on other genes, such as accidentally activating a cancer gene. And researchers have no way to reverse any unintended consequences. “You’re really toying with Mother Nature,” said Eric Topol of the Scripps Translational Science Institute in San Diego, adding that the risks can’t be fully known. —J.B.