Gene Transfer for Sickle Cell Disease

A promising approach for the treatment of genetic diseases is called gene therapy. Gene therapy is a relatively new field of medicine that uses genetic material (mostly DNA) from the patient to treat his or her own disease. In gene therapy, the investigators introduce new genetic material in order to fix or replace the patient's disease gene, with the goal of curing the disease. The procedure is similar to a bone marrow transplant, in that the patient's malfunctioning blood stem cells are reduced or eliminated using chemotherapy, but it is different because instead of using a different person's (donor) blood stem cells for the transplant, the patient's own blood stem cells are given back after the new genetic material has been introduced into those cells. This approach has the advantage of eliminating any risk of GVHD, reducing the risk of graft rejection, and may also allow less chemotherapy to be utilized for the conditioning portion of the transplant procedure. The method used to introduce the gene into the patient's own blood stem cells is to engineer and use a modified version of a virus (called a 'vector') that efficiently inserts the "correcting" genetic material into the cells. The vector is a specialized biological medicine that has been formulated for use in human beings. The investigators have recently discovered a gene that is very important in the control of fetal hemoglobin expression. Increasing the expression of this gene in sickle cell patients could increase the amount of fetal hemoglobin while simultaneously reducing the amount of sickle hemoglobin in their blood, and therefore potentially cure the condition. In summary, the advantages of a gene therapy approach include: 1) it can be used even if the patient does not have a matched donor available; 2) it may allow a reduction in the amount of chemotherapy required to prepare the patient for the transplant; and 3) it will avoid the strong medicines often required to prevent and treat GVHD and rejection. The goal is to test whether this approach is safe, and whether using gene therapy to change the expression of this particular gene will lead to increased fetal hemoglobin production in people with sickle cell disease.