A summer blockbuster


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.



This piece gets some of the info right, but gets one very important part wrong. B-cells are simply a type of white blood cell. In CLL, and in the majority of lymphomas and some other blood cancers, too, some B-cells are malignant but by far most are healthy, functioning white cells essential for immune functioning. The trouble with these designer T-cells, or "serial killer" T-cells (as the researches have dubbed them) is that they persist and deplete any B-cell, healthy as well as malignant.

What effect wholesale destruction of the immune system has on subsequent health of patients who receive this treatment remains to be seen. Even Rituxan, a monoclonal antibody that depletes B-Cells, carries a risk of immune dysfunction and resulting infections. But at least that therapy can be stopped. There is no way to turn these T-cells off. The thymus apparently continues to pass along this memory to kill white B-cells to all the maturing new T-cells.
- Posted by Liz McMillan 9/14/11 1:01 PM


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