The purpose of this study is to evaluate the efficacy of TXA127 to reduce the incidence (Grade II-IV) of acute Graft-vs.-Host Disease (aGVHD) in adult subjects undergoing double umbilical cord blood transplantation (UCBT). The study will also evaluate the effects of TXA127 on incidence, severity and duration of mucositis; neutrophil engraftment and platelet recovery; platelet transfusion requirements; immune reconstitution; and duration of corticosteroid use. TXA127 has shown to be well tolerated by patients and appears to induce rapid production of neutrophils and platelets in the bloodstream, as well as increase the immune system components. TXA127 has also been shown reduce the severity of chemotherapy-induced mucositis.