Gene Therapy Worries Grow

For the second time in 4 months, a child has developed a leukemia-like disease after receiving gene therapy at the Necker Hospital for Sick Children in Paris. Concerned about the safety of such trials, the U.S. panel that monitors the field for the National Institutes of Health has scheduled a public meeting on 17 January to review the clinical data and weigh its next steps.

The news of this second case of cancer in the French trial reached the U.S. Food and Drug Administration (FDA) on 20 December and quickly spread to other gene-therapy researchers. FDA responded by putting a hold on studies that, like the French trial, use retroviruses to shuttle therapeutic genes into the chromosomes of target cells.

Researchers say this second report of an adverse event mimics the first, which came to light in September (ScienceNOW, 3 October 2002). In that case, the Necker Hospital's lead investigator, pediatrician Alain Fischer told health authorities in France and abroad that one of 10 boys treated by his group for a disorder called X-linked severe combined immune deficiency (X-SCID) had developed a blood problem. A type of immune cell whose growth had been boosted by gene therapy was discovered to be replicating at an unhealthy rate. French clinicians treated it as though it were leukemia and reported within several weeks that they had successfully stopped its proliferation. But Fischer himself raised the possibility that his X-SCID cure--which was credited as the first unequivocal success for gene therapy--could have caused the cancerlike response.

The second adverse event in the Necker trial could have a devastating impact on researchers' plans and the hopes of patients who volunteered for these trials. "It kind of threw a wet blanket over everything," said Joseph Glorioso, president of the American Society of Gene Therapy and a molecular biologist at the University of Pittsburgh. "We will have to take a hard look" at possible causes. The Society also issued a statement today supporting the FDA's decision and saying it has "initiated a comprehensive review to understand the cause of the leukemia."

Related site
American Society of Gene Therapy Press Release