Seeking the Cause of Induced Leukemias in X-SCID Trial

Details of a second case of cancer in a gene-therapy trial in France, revealed last week, raise the odds that both were therapy induced. In both cases, a retrovirus engineered to shuttle corrective genes into cells inserted itself in or near a cancer-causing gene, apparently triggering uncontrolled cell growth. The risks seem “surprisingly high,” says pediatrician Alain Fischer, who with Marina Cavazzana-Calvo led the trial at the Necker Hospital for Sick Children in Paris.