We rarely report on Phase 1 trials, primarily because they involve a small number of patients and are limited in scope to studying side effects and establishing a safe administration of treatment. But there's good reason for us to make an exception. The news this week that scientists at the University of Pennsylvania had, for the first time, used gene therapy to treat a form of leukemia is not only welcome but long awaited.You see, it's been more than two decades since researchers hailed gene therapy as the next big thing in medicine. The theory is fairly straightforward: If a damaged gene causes a disease, simply introduce a healthy version of the gene and the disease will be cured. The problem was getting those healthy genes into the cells that needed them. The solution: viruses, which are preprogrammed to deliver their own DNA into the cells they infect. By re-engineering viruses to deliver helpful rather than harmful genes, scientists could theoretically make an effective therapy.But cancer isn't like most other diseases. Because it arises in the body's own cells, the immune system isn't prone to attacking it. So in this study of three patients with advanced chronic lymphocytic leukemia (CLL), the researchers removed the patients' T- cells and reprogrammed them to recognize and attack B cells, the malignant blood component of CLL. Then, by enlisting the help of a deactivated form of HIV, the researchers injected these modified T-cells back into to the patients and unleashed an army of cancer killers. Most important, these "reinvigorated" T-cells managed to reawaken T-cells that had been suppressed by the leukemia, and even helped generate "memory" T-cells that remained for a long time, ensuring that this invading force would not only wipe out the leukemia but also guard against its return.Sounds like a set-up for the summer's biggest action-adventure blockbuster, doesn't it?Check the studies published in The New England Journal of Medicine and Science Translational Medicine.