Dangerous antipsychotic shows leukemia-fighting promise in mice

McMaster University researchers in Canada are confronting an interesting challenge: What do you do when a drug pulled from the market over safety concerns appears to display enormous promise in another indication?

The issue is over thioridazine, as the Hamilton Spectator reports. It's a long-standing antipsychotic drug pulled from the shelves by Canadian regulators in 2005 and barely used in the U.S. anymore (except as a last resort) because it can cause an extremely dangerous irregular heartbeat with which patients can abruptly die. But the researchers have found that the drug reduced human leukemia stem cells in mice 50% in just 24 hours. Even more compelling, the drug only targeted the cancer stem cells but didn't appear to hit healthy cells, which would theoretically make it much less toxic than other cancer treatments. (Also, schizophrenia patients who took the drug before it was pulled apparently had far fewer instances of cancer, according to the science team's research.)

So how do you circumvent concerns about thioridazine, a schizophrenia treatment launched more than 50 years ago that began to raise health concerns back in 2000? The answer: You don't. The scientists, aware of the issues, believe that adjusting the dose will be much safer for patients, the story explains. That's because past patients whose deaths appeared related to thioridazine took the drug for a long time. Principal investigator Mick Bhatia, scientific director of McMaster's Stem Cell and Cancer Research Institute, believes that a half-dose of the drug would work if cancer patients took it for 8 to 21 days, hopefully avoiding safety issues.

"We think because it's a very small fraction of the time frame that the previous patients received it, and at a lower dose, we won't see any of the cardiotoxicity effects," Bhatia told the Spectator.

That remains to be seen. But the researchers hope to test their theory in a year, with a human trial involving a small group of leukemia patients, the article notes. For details about the study, read the journal Cell.

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