Peripheral Blood Stem Cell Transplantation (PBSCT)From Haploidentical Related Donors

Fewer than 35% of patients who might benefit from allogeneic HCT have an HLA-identical sib. Transplantation of peripheral blood stem cells (PBSCs) or bone marrow (BM)from HLA-matched or one-locus mismatch unrelated volunteer donors may be an alternative in some patients who lack HLA-matched sib donors. Despite increasing numbers of volunteer unrelated donors in national and international registries, identification of suitable unrelated donors who are matched with the recipient at all HLA-A, -B, -C and -DRB1 loci (8/8 HLA match) or mismatched at one of those loci (7/8 HLA match) is still challenging, especially for patients who are African-American or multiracial. Additionally, the 3- to 4-month delay between initiation of unrelated donor search to HCT is unacceptably long in patients with aggressive hematologic malignancies that are likely to relapse or progress during that interval. Transplantation of single or dual unrelated umbilical cord blood cells (UCB) units is another alternative, although problems with inadequate cell doses, delayed engraftment, graft rejection and infection persist in adult recipients of unrelated UCB transplants.

This is a phase II single-arm open-label study to evaluate the efficacy and safety of haploidentical related allogeneic PBSCT using a nonmyeloablative preparative regimen of intravenous busulfan (Busulfex®), intravenous melphalan (Alkeran®) and intravenous alemtuzumab (Campath®) in subjects who are candidates for related or unrelated allogeneic hematopoietic cell transplantation (HCT; transplantation of bone marrow or PBSCs) but who lack histocompatible related or unrelated donors. This study will also evaluate immunological reconstitution following haploidentical PBSCT by measurement of circulating T cell receptor excision circle (TREC)-positive cells, an indicator of thymic output. Systematic analyses of TREC-positive cells have not been performed in recipients of haploidentical PBSCT after the preparative regimen described in this protocol.