Trials of gene therapy in the treatment of Parkinson's disease are to begin in the US. The treatment has been authorised by the US Food and Drugs Administration (FDA) following publication of successful results in rats with a Parkinson's-like condition in the journal Science.
The particular gene therapy that will be used in the trial has been developed by scientists from the US and New Zealand. It involves placing a small amount of a virus, carrying a new gene to be inserted, into the brain. The new gene, called GAD, carries an instruction for brain cells to produce an inhibitor rather than an excitor substance, thereby ameliorating the symptoms of the disease. When the treatment was performed in rats, they were shown to be partly protected against symptoms of Parkinson's. In addition, dopamine-producing nerve cells stopped dying, a process which happens gradually in people with the disease.
This type of gene therapy is 'not just inserting a replacement for a missing or mutated gene for a genetic disorder', said Michael Oshinski, one of the researchers, based at the Thomas Jefferson University in Philadelphia. He added, 'we're changing the brain's circuitry as a treatment for a disease'.
Recently, gene therapy has come under criticism after a child developed leukaemia-like symptoms following gene treatment for severe combined immunodeficiency syndrome (SCID) in Paris, France. Similar French and American studies were halted, but now a panel of experts has urged the FDA to resume the experiments in the US. The panel recommended that all participants in gene therapy trials using retroviruses, like the one in France, should be warned that such a virus had apparently caused cancer in a child.