Transplantation of ex vivo expanded cord blood

Abstract

Umbilical cord blood (CB) from unrelated donors is increasingly used to restore hematopoiesis after myeloablative or more recently, nonmyeloablative therapy. CB transplants are associated with higher rates of delayed and failed engraftment than are bone marrow transplants, particularly for adult patients. At the University of Colorado, we studied the ex vivo expansion of CB in an attempt to improve time to engraftment and reduce the graft failure rate in the recipients. In the study, 43 patients with hematologic malignancies (n = 40) or breast cancer (n = 3) received high-dose therapy followed by unrelated allogeneic CB transplantation [1Shpall E.J. Quinones R. Giller R. et al.Transplantation of ex vivo expanded cord blood.Biol Blood Marrow Transplant. 2002; 8: 368-376Abstract Full Text Full Text PDF PubMed Scopus (340) Google Scholar]. A fraction of each patient’s CB allograft was CD34-selected and cultured ex vivo for 10 or 14 days prior to transplantation in defined media with stem cell factor (SCF), granulocyte colony-stimulating factor (G-CSF), and megakaryocyte growth and differentiation factor (MGDF). The remainder of the CB graft was infused without further manipulation. Two sequential cohorts of patients were accrued to the study. The first cohort had 40% and the second cohort had 60% of their CB graft expanded. This study demonstrated that the CD34 selection and ex vivo expansion of CB prior to transplantation is feasible. The engraftment failure rate was relatively low, and the time to neutrophil in large adults was in the range reported for pediatric recipients of much larger CB cell doses. In the successor cord expansion trial being conducted at the M.D. Anderson Cancer Center, several changes in the approach have been made. Patients with hematologic malignancies are now being randomized to receive either two unmanipulated CB units or one unmanipulated unit and one unit from which all the cells are expanded ex vivo. For the patients randomized to expansion, on day −14 one of their cord units is AC133-selected using the CliniMACS device. The AC133-negative fraction containing the T cells is frozen and the AC133+ fraction is cultured ex vivo for 14 days in media containing SCF, G-CSF and thrombopoietin (TPO). Following administration of the preparative regimen, on Day 0, the second unmanipulated CB unit is infused, followed by the thawed AC133-negative fraction and finally, the fraction which has been in culture for two weeks. This trial was recently initiated and accrual is in progress. Another expansion trial technology involves the use of a copper chelating agent, which has been shown by Peled et al to enhance the expansion of a more primitive CD34+ CB population when combined with early acting growth factors. A clinical trial employing this technology is in progress at M.D. Anderson. Patients with hematologic malignancies undergoing CB transplantation, with a unit that is cryopreserved in two fractions are eligible for the study. Twenty one days prior to infusion, the AC133+ cells are isolated from the smaller cord fraction using the CliniMACS device and cultured for three weeks in media containing interleukin-6 TPO, FLT-3, SCF, and the copper chelator tetraethylenepentamine (TEPA). The patients then receive high-dose therapy with the infusion of the larger, unmanipulated CB fraction on day 0, and infusion of the smaller expanded fraction of day +1. Thus far eight patients have been enrolled on the study and the results will be forthcoming. Future directions include the use of mesenchymal stem cells as a supportive stroma for the expansion of CB mononuclear cell progenitors, developed by McNiece et al. This approach would obviate the need for CD34 or AC133-selection, as those procedures are associated with substantial losses of CD34+ CB cells