Bone marrow transplants hold promise for sickle cell patients

By Helen Albert, Senior medwireNews Reporter

Research shows that even partially matched bone marrow transplants are able to eliminate sickle cell disease in some patients with sickle cell anemia.

The team hopes that this finding will make bone marrow transplants accessible to a much greater number of sickle cell patients, as finding perfectly matched donors can be difficult and the myeloablative conditioning required before such transplants is too toxic for many adult patients with this condition.

"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," explained study author Robert Brodsky (Johns Hopkins University School of Medicine, Baltimore, Maryland, USA) in a press statement.

"While bone marrow transplants have long been known to cure sickle cell disease, only a small percentage of patients have fully matched, eligible donors."

To solve the problem of toxicity, lead author Javier Bolaños-Meade and colleagues from Johns Hopkins University School of Medicine recruited 17 patients, aged 15 to 46 years, to undergo nonmyeloablative bone marrow transplantation.

The patients underwent a regimen of anti-thymocyte globulin, fludarabine, and cyclophosphamide in addition to total body irradiation before undergoing either human leukocyte antigen (HLA)-haploidentical (n=14) or HLA-matched (n=3) bone marrow transplantation. Following transplantation, patients were treated with cyclophosphamide, mycophenolate mofetil, and tacrolimus or sirolimus.

Overall, 11 patients had successful transplantations; eight (57%) of the HLA-haploidentical group and all three of the HLA-matched group.

After a median 711 days of follow up (minimum 224 days) 10 of the 11 patients were symptom free and six of the 11 were no longer taking immunosuppressive therapy.

"By safely expanding donor eligibility through the use of HLA-haploidentical related donors and high-dose cyclophosphamide post-transplantation, most such patients in need of bone marrow transplant may now be eligible for this potentially curative therapy," say the investigators.

Writing in Blood, the authors acknowledge that graft rejection remains a problem with haploidentical donors, but say that this "may be acceptable in a fraction of patients if the majority can be cured without serious toxicities."

They also note that in the six patients whose grafts failed, all recovered their own blood cells due to the reduced intensity of the conditioning regimen.

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