Trial of treatment for rare, childhood illness is halted, again.
Scientists have halted clinical trials of gene therapy to treat a rare immune disorder — less than a year after the trials were relaunched following an earlier stoppage.
The trials use gene therapy to treat different forms of severe combined immunodeficiency disease (SCID). The first trial to be stopped was halted in October 2002, and other trials were halted three months later, after two children in the trials developed cancer. But authorities allowed them to resume during the past year because the treatment had cured many children who lack reliable alternative treatments.
Researchers have now halted the trials again, after a third patient was found to have developed cancer. The suspension is a significant setback for the nascent field of gene therapy, because SCID treatment has been its most promising application to date.
The child with cancer was a patient of Alain Fischer of the Necker Hospital in Paris. He has been using gene therapy to treat the X-linked form of SCID, which is otherwise only treatable with bone-marrow transplant and is still often fatal. Fischer's trial restarted last May, and his team has treated one child since then.
But on 24 January, the French medical regulatory authority AFSSPS announced that a child who was treated by Fischer in April 2002 now has cancer.
As a result, Fischer's trial and similar ones in the United States have been halted again. The agency also said that one of the original two patients who had been diagnosed with cancer — both of whom were in Fischer's trial — died last October.
Fischer is now investigating why the third child, who was treated at a later age than the previous two children, developed cancer. The child's cells did not seem to have the same genetic glitch that caused the first two cancers, he says, but he cautions that the analysis is still under way.
Fischer adds that he still believes in gene therapy as a treatment for X-linked SCID, because 15 children treated in this way are still alive, and 14 are doing well four years later. But his group will not treat any more children using its current gene-therapy system, he says. He adds that he plans to change a key step in the treatment by changing the vector — the modified virus that delivers the therapeutic gene to the patients.
“The efficacy is there, but we have to improve on the safety,” Fischer says, adding that this is “not an uncommon situation” in medical research.
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Annals of Biomedical Engineering (2012)