Severe aplastic anemia (SAA) and myelodysplastic syndrome (MDS) are life-threatening bone marrow disorders. For SAA patients, long term survival can be achieved with immunosuppressive treatment. However, of those patients treated with immunosuppressive therapy, one quarter to one third will not respond, and about 50 percent of responders will relapse.
Allogeneic bone marrow transplantation from either HLA-matched sibling or matched unrelated donor cures about 70 percent of patients with SAA and 30-60 percent of patients with MDS. Unfortunately, most patients with these disorders are not suitable candidates for hematopoietic stem cell transplantation (HSCT) due to advanced age or lack of a histocompatible donor. For such patients, transplantation using unrelated cord blood (UCB) has been shown to be a reasonable alternative transplant strategy. The advantage to UCB transplant is the ease and rapidity of availability, requirement of less than perfect HLA match, and lower rates of graft versus host disease compared to mismatched bone marrow or peripheral blood stem cell transplants. The major disadvantage of UCB transplantation in adults is the limited number of nucleated cells contained within the cord unit resulting in prolonged neutropenia and failure of engraftment which contributes to infection and transplant related mortality (TRM). In order to harness the advantage of UCB availability and to overcome the disadvantage of delayed neutrophil recovery, we propose to test whether co-administration of unrelated umbilical cord blood and a relatively low number of highly purified haploidentical peripheral blood CD34+ cells from a related donor might promote rapid engraftment and reduce TRM secondary to prolonged neutropenia associated with conventional UCBT.
This research protocol is therefore designed to evaluate the safety and effectiveness of co-infusion of unrelated umbilical cord blood and haploidentical CD34 plus cells from a related donor following nonmyeloablative conditioning for neutropenic patients with SAA or MDS with refactory anemia (RA) that has proven to be refractory to medical therapy. Subjects will receive a novel non-myeloablative immunosuppressive conditioning regimen of cyclophosphamide, fludarabine, horse ATG and one dose of total body irradiation (200cGy) followed by an infusion of the allografts. The haploidentical stem cell product will be T-cell depleted and enriched for CD34 plus cells using the Miltenyi CliniMacs system. To reduce TRM secondary to prolonged neutropenia associated with conventional UCB transplantation, haploidentical CD34+ stem cells will be co-infused with a single UCB unit (serologically matched at greater than or equal to 4/6 HLA loci).
The primary endpoint is donor engraftment by day 42 (defined as an ANC of greater than 500 from either the haplo donor, the cord, or both combined). Secondary endpoints will include standard transplant outcome variables such as non-hematological toxicities, incidence and severity of acute and chronic GVHD, and relapse of disease. We will also evaluate ANC recovery (ANC greater than 500 cells/microl) at day 22, and 100 day and 200 day treatment related mortality (TRM) of this novel transplant approach. Health related quality of life will also be assessed pre-transplant 30 and 100 days poste transplant, and every 6 months until 5 years post transplant.