





The new method was born when researchers observed that bone marrow transplants in children and in patients with some other diseases can be successful even when some of the patient’s defective cells survive the chemotherapy and radiation intended to eradicate them. “We thought, ‘Can we intentionally do this, partially replace bone marrow, knowing that a little bit (of healthy cells) could be enough to make sickle cell go away?’” said the study’s senior author, Dr. John F. Tisdale of the National Heart, Lung and Blood Institute. “That would allow us to use less-toxic chemotherapy and radiation.”
The researchers tested their theory in 10 patients aged 16 to 45 with severe sickle cell who did not respond to hydroxyurea. The patients were given low doses of radiation and the immunosuppressive drug sirolimus to fight rejection of the donor cells. The chemotherapy normally given to suppress the immune system was eliminated completely. The patients then received marrow donated by siblings with matched markers in their blood. The result was a mix of cells from patient and donor.
After an average of 30 months, all are still alive and nine of the patients are considered cured of sickle cell. There were no significant side effects from the procedure and none of the patients experienced graft-versus-host-disease (GVHD), one of the most common complications of bone marrow transplants in which the body rejects the new marrow. “Because sickle red blood cells only live about six or seven days and normal red blood cells live 120 days, if you can get a little bit of the donor cells in there, the donor cells take over,” Tisdale said.
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