Drug that kills cancer stem cells has safety concerns

An antipsychotic drug found by McMaster University researchers to kill cancer stem cells was pulled from the shelves by Health Canada years ago because of safety concerns.

Thioridazine could dramatically change cancer treatment. The researchers recently discovered it reduced leukemia stem cells by 50 per cent in 24 hours in mice injected with primary human samples.

We have certainly not seen any drug weve ever tested have that kind of potency, said Dr. Mick Bhatia, scientific director of McMasters Stem Cell and Cancer Research Institute and principal investigator of the study published Thursday in the science journal CELL.

Thioridazine is also remarkable because its a smart drug that kills only cancer stem cells and appears to have no effect on normal cells. As a result, it avoids the toxic side-effects of conventional cancer treatments.

Were excited we have something interesting, but were always nervous because we want to make sure it helps people, said Bhatia. The impact of this will be determined if we can put some patients in remission and certainly thats my romantic goal.

But there are questions about the safety of the drug. Health Canada halted sales of Thioridazine in September 2005.

It was pulled because it can cause a serious type of irregular heartbeat that may cause sudden death. Three deaths in Canada between 2000 and 2005 were reported by Health Canada to be possibly related to thioridazine.

Concerns started to be raised in 2000 about the drug used to treat schizophrenia since 1959.

Its no longer approved in Canada and is only used as a last-ditch hope in the United States for schizophrenia patients who have already tried at least two other antipsychotic medications.

But Bhatia believes it will be safer for cancer patients because theyre only on it for eight to 21 days instead of a number of years, and they take half the dose.

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Drug that kills cancer stem cells has safety concerns