UM171 Expansion Overcomes Shortcomings of Cord Blood Transplantation While Maintaining Benefits

Background Benefits of cord blood (CB) transplantation include low rates of relapse and chronic graft-versus-host disease (GVHD). However, CB use has rapidly declined because of the high rates of infections, severe acute GVHD, and transplant-related mortality (TRM) as well as prolonged hospitalization. We therefore initiated a clinical trial with UM171, a potent agonist of hematopoietic stem cell (HSC) self-renewal, to attempt to solve these limitations and permit transplantation of smaller, better HLA-matched CBs. Methods Expansion culture lasted 7 days and patients received a myeloablative conditioning regimen followed by a single CB transplant including both the expanded CD34+ cells and the lymphocyte-containing CD34- fraction. Results Between 9/16-11/18, 22 adults with mostly high- to very high-risk hematologic malignancies were transplanted. Median transplant co-morbidity index was 2 (0-5). Five patients had already failed an allogeneic transplant, 3 patients had acute leukemia not in remission, and 2 patients had relapsed/refractory aggressive lymphoma. UM171 treatment profoundly changed the cellular composition of the graft, including a 600 and 8000-fold increase in dendritic and mast cell progenitors, respectively. Neutrophil engraftment was prompt with median time to 100 and 500 neutrophils/μL of 9.5 and 18 days, respectively. Patients seemed to derive clinical benefit from achieving 100 neutrophils rapidly translating into early resolution of febrile neutropenia (median day 7) contributing to shorter hospitalization when compared to conventional CB transplants at same institution with larger cell doses and similar time to 500 neutrophil engraftment. Median CD4 counts at 3 and 12 months were 218 and 413/μL, respectively. Incidence of grade 3-4 acute GVHD was low (9%) and there was no steroid refractory GVHD or moderate-severe chronic GVHD. More than 90% of patients were off immunosuppressive therapy by 12 months. One patient died of TRM ( Conclusions A 7-day UM171 expansion CB protocol is feasible and provides clinical benefits beyond engraftment, such as very low TRM. If confirmed, UM171 expansion may overcome the shortcomings of CB transplants while maintaining its benefits of low risk of chronic GVHD and relapse. We have now embarked on a phase 2 trial to confirm if a UM171 modified graft, enriched in dendritic cells, will have a potent antileukemia effect in extremely high-risk patients such as refractory leukemias and high risk mutations (e.g.: p53, EVI-1).