Another Child Devloped Cancer: SCID Trials Suspended – ABC

Tue, 14 Jan 2003

ABC News reports that the FDA suspended 30 gene therapy trials after a second child developed leukemia. So far, two boys who had undergone the experimental gene therapy treatment for immunodeficiency, “bubble boy disease” — or SCID–developed leukemia. “In gene therapy, a vector — usually but not always a virus — is used to carry a healthy gene into the cells of patients.”

The FDA has been reviewing 150 gene therapy trials that used a retrovirus as a vector. Since October, about 50 of those trials had closed down because all the patients enrolled for gene therapy had died of their diseases.

An emergency meeting has been called for Friday by the Office of Biotechnology Activities at the National Institutes of Health.

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U.S. Delays Gene Therapy Trials After Cancer Case

Jan. 14

By Maggie Fox, Health and Science Correspondent

WASHINGTON (Reuters) – The U.S. Food and Drug Administration said on Tuesday it was halting about 30 gene therapy trials after learning a second child in a French gene therapy experiment has leukemia.

The two boys in France were diagnosed with leukemia after undergoing the experimental treatment for “bubble boy disease” — a deadly condition known officially as x-linked severe combined immunodeficiency, or SCID.

A genetic defect leaves such children — always boys — without an immune system. Without treatment, they can die of infections that would hardly affect a healthy child.

The gene therapy, which reinforces the children’s bone marrow with genetically engineered immune cells, had worked remarkably well in the children. They had seemingly been cured of SCID before the leukemia symptoms began and were among 10 gene therapy patients in France who were living normal lives.

Both leukemia patients are apparently being helped by chemotherapy, said Dr. Philip Noguchi, head of gene therapy issues at the FDA. “We do know that both children, the first one and second one, are clinically stable,” he told Reuters.

The French researchers, led by Dr. Alain Fischer of Necker Hospital in Paris, declined to comment, saying they would need to notify the parents of all their patients first.

In both cases, the French researchers have quickly but quietly notified U.S. health officials, including the FDA, so that similar experiments in the United States can be assessed.

TRIALS SUSPENDED

After the first boy in France was diagnosed with leukemia in September 2002 the FDA suspended three similar gene therapy trials that had started or were about to start in the United States. British regulators declined to suspend similar experiments there.

The FDA told scientists those suspensions will hold until the leukemia cases are checked out. As a precaution, they have added just under 30 trials that also used retroviruses to target bone marrow stem cells, Noguchi said.

In gene therapy, a vector — usually but not always a virus — is used to carry a healthy gene into the cells of patients. If it works correctly, the virus injects its DNA and the new gene into cells and corrects the genetic defect.

Scientists told a meeting in October it was possible the retrovirus used in the French experiments had injected its DNA into a vulnerable site in a single blood cell of the leukemia patient. This could have caused damage that would cause that cell to proliferate wildly, causing the leukemia.

The FDA had started a careful review of 150 gene therapy trials that used a retrovirus as a vector. Noguchi said since October, about 50 of those trials had closed down because all the patients enrolled for gene therapy had died of their diseases, but the rest are still being reviewed.

SERIOUS SETBACK TO GENE THERAPY

The French cases mark the most serious setback to the still-experimental field of gene therapy since Jesse Gelsinger, 18, died in the United States in 1999 as the result of a gene therapy experiment aimed at curing a rare liver disorder.

The question is whether the risk of cancer outweighs the risk from gene therapy, which is highly experimental but often a patient’s only hope. In the initial French case, the child was reported to be faring well on chemotherapy for his cancer.

Childhood leukemia is generally easy to treat, with cure rates of 90 percent or more. In contrast, children with SCID who cannot get a bone marrow transplant almost always die within a year.

“I think we shouldn’t view this as death knell to gene therapy,” said Dr. Harry Malech of the National Institute of Allergies and Infectious Diseases, whose scheduled gene therapy trial involving X-SCID patients has been suspended.

“We need more good science to sort out what went wrong,” he said in a telephone interview.

The Office of Biotechnology Activities at the National Institutes of Health has called an emergency meeting for Friday to discuss the issue.

Gene therapy experts who have been called to the meeting — and who did not wish to be named because the French researchers have asked for confidentiality — say the development of leukemia could be unique to the X-SCID cases.

Noguchi said the FDA would consider allowing the most desperate patients — those who will die without treatment — to continue on gene therapy.

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