WITHIN just eight days of starting a novel gene therapy, David Aponte's "incurable" leukaemia had vanished. For four other patients, the same happened within eight weeks, although one later died from a blood clot unrelated to the treatment, and another after relapsing. The cured trio, who were all previously diagnosed with usually fatal relapses of acute lymphoblastic leukaemia, have now been in remission for between 5 months and 2 years. Michel Sadelain of the Memorial Sloan-Kettering Cancer Center in New York, co-leader of the group that designed the trial, says that a second trial of 50 patients is being readied,...