In a preliminary clinical trial, investigators at Johns Hopkins have shown that even partially matched bone marrow transplants can eliminate sickle cell disease in some patients, ridding them of painful and debilitating symptoms and the need for a lifetime of pain medications and blood transfusions.
The researchers say the use of such marrow could potentially help make bone marrow transplants accessible to a majority of sickle cell patients who need them.
After a median follow-up of two years, the transplants successfully eliminated sickle cell disease in 11 of 17 patients. Three were fully matched to their donors and eight received half-matched donor marrow. All 11 patients are free of painful sickle cell crises and 10 no longer have anemia. There were no deaths and no unexpected toxicities.
Six of the 11 patients (all half-matched) have stopped taking immunosuppressive drugs, although some still require narcotics for chronic pain because of sickle cell-related organ damage. Blood tests on the six patients show that their red cells are now completely derived from their donors' marrow.
Patients with severe sickle cell disease (SCD) face shortened life spans, intractable pain and eventual organ damage as a result of their disease, an inherited disorder caused by a mistake in the oxygen-carrying hemoglobin molecules in red blood cells. The flawed genetic code stiffens red cells, and shapes them into a pronged "sickle" that clump and stick into blood vessel walls, cutting off blood and oxygen to tissues and organs throughout the body.
SCD occurs in approximately one in 400 African Americans and rarely in Caucasians. An estimated 100,000 people are currently living with sickle cell disease in the United States.
Most patients die before age 50; many suffer poor quality of life with frequent episodes of "off-the-charts" pain and an increased risk for kidney failure, stroke, deep-vein thrombosis and lung disease.
Treatments include blood transfusions and a drug, hydroxyurea. Many patients use narcotics to control severe pain and have repeat hospitalizations. Bone marrow transplants have been successful in curing some cases, but matching donors are rare and the procedure itself poses risk.
In the current study, 17 patients at The Johns Hopkins Hospital were offered bone marrow transplant options, including the use of half-matched donor marrow to try to replace their "sickled" blood cells with healthy new ones. The transplants were successful in 11 of the patients, of whom eight were only half-matches. Results of the trial were published in the Sept. 6 early online edition of Blood.
"We're trying to reformat the blood system and give patients new blood cells to replace the diseased ones, much like you would replace a computer's circuitry with an entirely new hard drive," says Robert Brodsky, M.D., director of the Division of Hematology at Johns Hopkins and the Johns Hopkins Family Professor of Medicine and Oncology. "While bone marrow transplants have long been known to cure sickle cell disease, only a small percentage of patients have fully matched eligible donors."
National registries often are of little help in finding donors for sickle cell patients, because most of those in need are African American and other minorities who are vastly underrepresented in registries, say the Johns Hopkins researchers.
To overcome the shortage of donors, investigators at Johns Hopkins developed techniques, recently tested in leukemia and lymphoma patients, to transplant with bone marrow that is half-identical or "haploidentical" to the patient's tissue type. Half-matched bone marrow can be obtained from parents, children and most siblings and is extracted by needle from the hip bone.