Myeloid Chimerism Clinical Trial
Official title:
Repeat Peripheral Blood Stem Cell Transplantation for Patients With Sickle Cell Disease or Beta-Thalassemia and Falling Donor Myeloid Chimerism Levels
Background: Sickle cell disease can often be treated with blood stem cell transplants. But for some people the disease returns. This study will give a second transplant to people whose disease has returned but still have some donor cells in their body. Objective: To cure people s sickle cell disease by giving a second treatment that makes more room in their bone marrow for donor cells. Eligibility: People ages 4 and older with sickle cell disease who had a transplant but the disease returned, and their donor relatives. Donors can be 2 years of age or older. Design: Participants will be screened with medical history, physical exam, and blood tests. Recipients will also be screened with heart and breathing tests, x-rays, a bone marrow sample, and teeth and eye exams. They must have a caregiver. Donors will have 7-8 visits. They will take a drug for 5-6 days to prepare them for the donation. For the donation, blood is taken from a vein in the arm or groin. The stem cells are collected. The rest of the blood is returned. This may be repeated. Recipients will get a long IV line in their arm or chest for about 1-2 months. They will take drugs to help their body accept the donor cells. They will get the donor cells and red blood cell transfusions through the line. They will stay in the hospital about 30 days after the transfusion of donor cells. In first 3 months after the infusion, recipients will have many visits. Then they will have visits every 6 months to 1 year for 5 years. During those visits they will repeat some of the screening tests....
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. An additional protocol is ongoing for patients with high risk of graft rejection which employs pentostatin and oral cyclophosphamide (PC) pre-transplant to further deplete recipient lymphocytes in an attempt to decrease the rate of graft rejection, and to date the engraftment rate has substantially improved. Our first haploidentical transplant protocol showed improving engraftment and success rates with the addition of post-transplant cyclophosphamide, but with a median follow-up of 5 years, the disease-free survival was at best 50%. Our new haploidentical transplant protocol has had some encouraging early results in the first 5 patients transplanted. Based on 67 patients undergoing HLA-matched sibling or haploidentical PBSC transplants at the NIH, we sought to determine what donor chimerism level is necessary to reverse SCD. Three of the patients had falling donor myeloid chimerism (DMC) levels, and when the DMC level fell below 20%, all 3 patients had return of their SCD. Our mathematical model showed that only 20% DMC (which tracks with donor erythroid chimerism) is necessary due to vast differences in donor and recipient red blood cell (RBC) survival. As all 3 patients had persistent but insufficient donor chimerism levels, we performed a PBSC boost using the same donor and busulfan/alemtuzumab conditioning. Haploidentical patients received CD34-selected PBSCs and HLA-matched sibling patients received unmanipulated PBSCs. All 3 patients now remain free of SCD with DMC levels of 100% at 1, 2.5, and 3.5 years post-transplant. Because the same donor was used and no patient experienced graft rejection, the failure of the original protocols likely was due to insufficient myelosuppression and not insufficient immunosuppression. Therefore, in this protocol, we propose repeat PBSC transplants using increased myelosuppression and CD34-selected PBSCs in patients with a haploidentical donor or unmanipulated PBSCs in patients with an HLA-matched sibling donor from the same donor in a population of patients who have falling DMC and return of SCD. ;