The first gene therapy trial for Alzheimer鈥檚 disease has begun in California. Surgeons injected modified skin cells into the brain of a woman suffering from the disease.
The patient鈥檚 own skin cells were modified with a virus containing the gene for human nerve growth factor (NGF). When such cells have been implanted in the brains of rats and monkeys, they were able to produce the growth factor for at least one year.
NGF can stop cells called cholinergic neurons from atrophying or dying and promotes the formation of new connections by these cells. In Alzheimer鈥檚 patients, the death of these neurons appears linked to the onset of dementia and cognitive decline
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In treating neuro-degenerative diseases, gene therapy provides an alternative to implanted neurons derived from human embryos or fetuses. Gene therapy avoids this ethical problem, but was severely tarnished by the death of teenager Jesse Gelsinger during a 1999 gene therapy trial, which aimed to correct a liver defect.
Quality of life
The new 18 month Alzheimer鈥檚 trial is designed to test safety, but leader Mark Tuszynski of the University of California, San Diego says the eight patients in the trial will receive a dose of NGF that was effective at protecting monkey neurons.
鈥淭he hope is this will reduce the rate of degeneration of these cells and improve quality of life from months to years,鈥� he says.
Howard Federoff, who works on Alzheimer鈥檚 gene therapy at the University of Rochester, New York thinks Tuszynski鈥檚 approach is sound. 鈥淗is work in animals has been very well done,鈥� he says 鈥淚 think NGF will prove to be useful in humans as well.鈥�
But Tuszynski cautions that other types of neurons on which NGF has no effect also die off in Alzheimer鈥檚. Even so, the growth factor may be able to stave off the disease鈥檚 most crippling effects.
鈥淭here isn鈥檛 a perfect animal model of Alzheimer鈥檚,鈥� he says. 鈥淪o these are things we can only learn in a human trial.鈥�
Related story: Engineering a cure (25/12/1999).