Gene Therapy Experiments Put on Hold
Federal authorities have temporarily suspended three gene therapy experiments -- two of them in Los Angeles -- following news that a third child in a similar French study has developed leukemia and that one of the three has died.
A Food and Drug Administration advisory panel is meeting in suburban Washington today in an effort to determine whether the French cases are an isolated incident caused by the specific gene being used in the therapy or a precursor of problems that will affect all gene therapy attempts.
Experts don't expect an immediate consensus from the advisory panel, but there appears to be a growing feeling among researchers that the problem is of limited scope and reflects the combination of the virus and gene used by the French. Experiments using other genes have, so far, been free of adverse effects.
Most of the researchers involved will be gathering in Washington March 15 for a separate meeting sponsored by the National Institutes of Health's Recombinant DNA Advisory Committee. They are scheduled to discuss their results to date. Despite the three leukemia cases, the results have been promising.
The experiments in question have involved treatments for severe combined immunodeficiency disease, or SCID, a potentially fatal genetic disorder that leaves its victims susceptible to life-threatening infections. The best-known example of the disease was David, the Houston "bubble boy" who lived for 12 years in a sterile enclosure to keep infections out.
Dr. Alain Fischer of Necker Hospital in Paris has been treating patients with so-called X-linked SCID, which is caused by a defective gene called GammaC. Fischer put a healthy form of the gene in a modified mouse leukemia virus, which was used to insert the gene into embryonic blood cells that were then infused into the patient.
Fischer has treated 17 patients, and virtually all have shown major improvement if not a cure. But two years ago, Fischer said that two of the patients had developed leukemia, presumably as a result of the treatment.
The FDA temporarily suspended 27 gene therapy trials in the United States but eventually allowed them to proceed again after concluding that there were special circumstances in the cancer victims. Both were below the age of 2 and had received large doses of cells.
In recent weeks, Fischer revealed that one of the two original leukemia victims had died of the disease and that a third child had apparently contracted it. That child, moreover, was older than the first two and received a lower dose of altered cells.
