The first gene therapy trial for Alzheimer’s disease has delivered promising early results.The trial was designed to test the safety of injecting genetically modified cells directly into a part of the brain most severely affected by the disease. The modified cells contain a gene for nerve growth factor (NGF).Eight patients underwent the surgery in 2001. One has since died of a heart attack, but the remaining patients are not declining anywhere near as rapidly as expected, says Mark Tuszynski, from the University of California in San Diego.Animal experiments have shown that NGF can protect the type of neurons that die in Alzheimer’s disease, and seems to encourage the remaining cells to proliferate and work more effectively. But the molecule has to be delivered directly into the brain for long periods to be effective. So Tuszynski and his team turned to gene therapy techniques.They took skin cells called fibroblasts from each patient, and used a genetically modified virus to infect them with the NGF gene. The cells were allowed to multiply, then were injected into the brain, in a region called the nucleus basalis, which is severely affected by the disease. “They act as biological pumps for the long term administration of NGF in the brain,” says Tuszynski.
