the much touted gene therapy as a miracle cure for diseases linked to genetic disorders recently suffered a major setback with the discovery that it has caused leukaemia in a child undergoing experimental treatment. The child was being treated at the Paris-based Necker-Enfants Malades clinic for x-severe combined immunodeficiency syndrome, a disease characterised by genetic mutation in bone marrow cells as a result of which these cells are unable to make white blood cells -- the main soldiers of the body's immune system.
The disease is conventionally treated by transplanting bone marrow cells. However, lack of suitable donors is always a problem. As the disease is caused due to single gene mutation, gene therapy is considered as a good treatment choice. The therapy involves taking out mutated bone marrow cells and repairing them by inserting a virus gene. The repaired cells are then put back into the bone marrow. Unfortunately, the position where the gene gets inserted cannot be controlled. "There is a chance that it could insert itself into the wrong place and then create problems," says Bobby Gaspar, a consultant immunologist with the London-based Great Ormond Street Children's Hospital. In the Paris case, experts believe that the repaired gene might have caused malfunctioning of the gene implicated for causing leukaemia by getting inserted too close to it.
In response to the catastrophe, France and the us have halted on-going gene therapy studies and trials. But the uk has decided to continue with them under strict vigilance. "We have to weigh the benefits against the possible risks," said Norman Nevin, chairperson of Gene Therapy Advisory Board (gtac) of the uk. "We accept there is a safety risk with this treatment. However, because other treatment options are so limited, we decided on ethical grounds that approval should continue," he added.
In Britain there are 14 gene therapy trials going on involving 160 patients. Following the incident, gtac has decided to now form a specialised sub-committee for reviewing studies involving this type of gene therapy.