Will rapamycin work in people with leukemia?
The researchers found that rapamycin was incredibly effective at both restoring normal blood-forming stem cells and eliminating leukemic stem cells. If they treated mice with rapamycin early in the onset of leukemia, the mice remained healthy indefinitely -- long after all the untreated mice were dead.
Dr. Morrison's research indicated rapamycin was most effective at curing mice with leukemia when they were treated early before they had too many leukemic stem cells in their bone marrow. Some people with chronic myeloid leukemia are in a similar situation. CML patients today are often treated with a drug called Gleevec, which reduces the number of leukemic cells, but doesn't cure anyone, because it doesn't kill the leukemic stem cells.
Rapamycin has been used extensively in patients and is known to be well tolerated. It's generally used as an immunosuppressant in people receiving organ transplants. The hope is that using rapamycin, in addition to Gleevec, will cure some of these patients. If it works, this will be a therapy that kills cancer stem cells without harming normal stem cells.