RecruitingPhase 2Drug trialOptimized Cord Blood Transplantation for the Treatment of Patients With High-risk Hematologic Malignancies Who Have Relapsed After First Allogeneic Stem Cell TransplantationThe goal of this clinical research study is to learn if intermediate-intensity conditioning therapy followed by a cord blood transplant can help to control high-risk hematological malignancies in patients who need a second allogeneic stem cell transplantation.