Here's some more informed commentary than mine:
New cancer case halts US gene therapy trials
14:10 15 January 02
NewScientist.com news service
Nearly 30 US gene therapy trials were halted on Tuesday following the announcement that a second child in a pioneering French gene therapy trial has developed leukaemia as a result of the treatment.
The French trial is testing a treatment for "bubble boy" disease, or SCID (Severe Combined Immunodeficiency Disease). The initial results were hailed as one of the first great successes for gene therapy.
But the trial was halted in October 2002 following the first diagnosis of leukaemia in one of the boys. Three similar US gene therapy trials were suspended at the same time. A similar trial in the UK was not halted, as British doctors argued that without the treatment many of patients would certainly die.
However, the second leukaemia case has prompted the US Food and Drug Administration to suspend other trials that use the same type of virus to shuttle therapeutic genes into blood cells.
"Precautionary measure"
The FDA has no evidence of leukaemia caused by gene therapy in US studies, but says the suspension of trials using retroviruses is a "precautionary measure". The UK's Committee on the Safety of Medicines has said it will consider the implications of the French announcement at a meeting on Wednesday.
Cure rates for childhood leukaemia are often as high as 90 per cent, but boys with SCID almost always die within a year without a bone marrow transplant. As a result, Philip Noguchi, head of gene therapy issues at the FDA has said that the agency would consider allowing the gene therapy to continue on those children already being treated and who will die without it.
Noguchi added: "We continue to see gene therapy as a promising therapy for all those who have not benefited from current technologies."
Boys with SCID have no resistance to infection due to a faulty copy of an X-chromosome gene that makes an immune protein called interleukin-2. The gene therapy corrects the genetic defect by shuttling a correct copy of the gene into the patient's cells using a virus. The treatment appears to have cured a number of boys.
The two boys with leukaemia are now being treated with chemotherapy and are clinically stable.
The leukaemia may have been caused by the fact that the injected DNA cannot be targeted to insert into a specific part of a chromosome. Scientists suspect the first child developed the cancer because the gene inserted next to an oncogene, called Lmo2, in a single white blood cell. This could have triggered the cell to proliferate uncontrollably, causing the disease.
According to Reuters, gene therapy experts called to an emergency meeting on Friday at the US National Institutes of Health have said that the development of leukaemia could be unique to the SCID gene therapy trial.
newscientist.com
Peter
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