Haploidentical PBMC Transplant for Severe Congenital Anemias

Overview

Background: Bone marrow transplantation (BMT), which involves transplanting a donor's marrow stem cells, is capable of curing some congenital anemias. BMT usually involves high-intensity treatment with chemotherapy and radiation to kill abnormal cells, which affects all systems of the body. People with anemias often have damage to other organs such as the kidneys, which can be further damaged by the chemotherapy. Only approximately 20 percent of patients have a full-matched donor, making treatment for many people with anemias unavailable. However, 90 percent of patients may have a half-matched donor, but using a half-matched donor increases the toxicity of BMT. Objectives: To determine if a research BMT with half-matched donor cells, low-intensity radiation, immunosuppressant drugs, and no chemotherapy will be effective in patients with sickle cell disease and Beta-thalassemia. To determine the effectiveness of cyclophosphamide, an immunosuppressant drug, in preventing rejection of the donor cells. Eligibility: Recipients are individuals at least 18 years of age who have been diagnosed with sickle cell disease and Beta-thalassemia, and who have a family member who is a haploidentical (i.e., half match) tissue match. Donors are healthy individuals between the ages of 2 and 80 who are found to be suitable donors. Design: Donors will undergo apheresis, which involves withdrawing blood from one arm vein, passing it through a machine that removes bone marrow stem cells, and returning the remaining blood through the vein in the other arm. Donors will receive a drug that causes the stem cells to be released into the bloodstream prior to the apheresis procedure. Recipients will undergo routine physical and laboratory examinations, including bone marrow sampling at the beginning of the study. After transplantation, physical and laboratory examinations will occur on a weekly or twice weekly basis at the outpatient clinic. Recipients will be examined every 6 months starting 100 days posttransplant for 5 years. Recipients will receive low-dose radiation in two treatments 1 and 2 days before the transplant. They will also be given immunosuppressant therapy with alemtuzumab and sirolimus. Another immunosuppressant drug, cyclophosphamide, will be given in the future as needed to subsets of the recipients to prevent rejection of donor cells. Recipients will receive the donor stem cells through a previously inserted central line. The process takes up to 8 hours. Recipients will receive blood transfusions as necessary to prevent anemia and bleeding during the posttransplant period. They may also receive intravenous antibiotics to prevent infection.

Nonmyeloablative allogeneic peripheral blood stem cell (PBSC) transplants are currently being investigated in phase I/II trials assessing engraftment, efficacy, and toxicity at a number of transplant centers. Our ongoing protocol for patients with severe congenital anemias, particularly sickle cell disease (SCD), and an HLA-matched sibling donor has had excellent preliminary results. None of the patients who engrafted had sickle-related events or any evidence of graft versus host disease (GVHD). There was no significant toxicity associated with the conditioning regimen. Our main limitation has been a lack of HLA-matched sibling donors in the majority of patients. We performed a study in which patients with severe SCD who lacked a suitable donor underwent a search for a matched unrelated donor or umbilical cord donor. The vast majority of patients were not found to have an appropriate alternative donor. We therefore seek to develop a safe nonmyeloablative regimen to be applied to the haploidentical setting so that family members can serve as donors and greatly expand the donor pool. In this protocol, we propose PBSC transplantation in patients with SCD and thalassemia, considered at high risk for complications from or ineligible for standard bone marrow transplantation, with allogeneic peripheral blood stem cells from a haploidentical donor using a novel immunosuppressive regimen without myeloablation in an attempt to further decrease the transplant-related morbidity/mortality. The low intensity nonmyeloablative conditioning regimen will consist of a relatively low radiation dose for therapeutic radiation, Alemtuzumab (Campath ), Sirolimus (Rapamune ), and Cyclophosphamide (Cytoxan ) as a strategy to provide adequate immunosuppression to allow sufficient engraftment for clinical remission with a lower risk of GVHD development. T-cell replete, donor-derived, granulocyte colony-stimulating factor (G-CSF)-mobilized PBSC will be used to establish hematopoietic and lymphoid reconstitution. The primary endpoint of this study is the percentage of patients who have sustained donor type hemoglobin without significant GVHD for patients with SCD, or who are transfusion-independent and without significant GVHD for patients with thalassemia. Other endpoints include degree of donor-host chimerism necessary for long term graft survival and disease amelioration, incidence of acute and chronic GVHD, incidence of graft rejection, transplant-related morbidity, as well as disease-free and overall survival.