Cancer fears cast doubts on future of gene therapy

Washington

A once-promising gene-therapy treatment should be used only as a last resort, advisers to the US National Institutes of Health (NIH) said this week.

Members of the NIH's Recombinant DNA Advisory Committee, meeting in Bethesda, Maryland, on 10 February, said that patients suffering from severe combined immunodeficiency disease (SCID) should be treated by gene therapy only if they fail to respond to all other treatments. SCID, which disrupts the development of the immune system, is the only disease so far to have been cured by gene therapy.

SCID trials in the United States were suspended last year by the Food and Drug Administration (FDA) after a child in the world's most advanced study, led by Alain Fischer of the Necker Hospital for Sick Children in Paris, developed leukaemia. The agency halted 24 similar gene-therapy trials when a second child in Fischer's trial was diagnosed with leukaemia in December (see Nature 421, 305; 200310.1038/421305a).

In both cases, the retrovirus used to deliver the corrective gene to the patient inserted itself into a stretch of DNA in or near a gene called LMO2, which can cause childhood leukaemia. Since then, Christof von Kalle, a molecular geneticist at the Cincinnati Children's Hospital, has found that a similar insertion has occurred in a third child in Fischer's study, although this patient has not developed leukaemia.

The committee's advice to limit the use of SCID gene therapy is expected to influence the FDA's final decision on the US trials. The agency will consider whether to halt the SCID trials permanently when its advisory committee meets on 28 February.

Scientists say that this meeting is crucial for the future of gene therapy. “People are very worried that these cases will shut down the entire field of gene transfer,” says Diane Wara, a paediatrician at the University of California, San Francisco, who sits on the NIH committee.