FYI from the NHLBI Index

January 2010: Vol. 10, Issue 3
Feature Article

Breakthrough for Adult Sickle Cell Disease

Breakthrough for Adult Sickle Cell Disease

A modified blood adult stem-cell transplant regimen has effectively reversed sickle cell disease (SCD) in 9 of 10 adults who had been severely affected by the disease, according to results of a National Institutes of Health study reported in the December 10 issue of the New England Journal of Medicine.

SCD, the most common serious inherited blood disorder in the United States, is a problem of significant medical, psychological, social, and economic importance, particularly among the black population. It is caused by a gene mutation that results in abnormal hemoglobin, causing red blood cells to collapse into a sickle shape, become stiff and sticky, and form clumps that block blood flow. As a result, SCD patients often experience severe pain, organ damage from lack of oxygen, and stroke.

Children with severe SCD have been cured with bone marrow transplants after undergoing a regimen in which their own marrow was completely destroyed with chemotherapy. That regimen, however, has proven to be too toxic for adults, who because of years of accumulated organ damage from SCD are less able to tolerate complete marrow transplantation.

This adult trial sought to reduce toxicity by only partially replacing the bone marrow. To achieve this, investigators used a low dose of radiation to the whole body and two drugs, alemtuzumab and sirolimus, to suppress the immune system. The relatively low toxicity regimen allowed patients to become tolerant to the donor immune cells and to achieve stable mixed donor chimerism, a condition in which an individual has two genetically distinct types of cells in the blood. In most patients the donorís red blood cells completely replaced the recipientís and were sufficient to reverse SCD.

The trial was conducted at the NIH Clinical Center in Bethesda, MD, by researchers from the National Institute of Diabetes and Digestive and Kidney Diseases, the National Institute of Allergy and Infectious Diseases, and the NHLBI

Modified 1/13/10
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