Phase 2 Poor Risk DLBCL of TLI and ATG Followed by Matched Allogeneic HT as Consolidation to Autologous HCT

The purpose of this study is to determine if double autologous then allogeneic hematopoietic cell transplant may offer an improved treatment option for patients with relapsed diffuse large B-cell lymphoma (DLBCL) who are not likely to be cured by the conventional transplantation regimen.

This study tests a tandem transplant approach that starts with transplantation of the participant's own hematopoietic (blood) cells, eg, autologous hematopoietic cell transplant (auto-HCT) as preparation for an subsequent matched-donor allogeneic HCT (allo-HCT). Participants will be have progenitor cells (stem cells) mobilized into the peripheral blood with rituximab, chemotherapy (cyclophosphamide or etoposide), and filgrastim (G-CSF); undergo apheresis to collect autologous peripheral blood stem cells (PBSC, aka hematopoietic cells); and be re-infused with ≥ 3 x 10e6 CD34+ cells/kg (auto-HCT). Subsequently, participants will receive therapeutic, non-myeloablative chemotherapy (carmustine + cyclophosphamide + etoposide), then transplant conditioning \[total lymphoid irradiation (TLI) + anti-thymocyte globulin (ATG)\] followed by ≥ 2 x 10e6 CD34+ cells/kg allogeneic PBSC obtained from a human leukocyte antigen (HLA)-matched or HLA single allele / antigen-mismatched donor (allo-HCT). Donors will be mobilized with 16 µg/kg filgrastim. Participant allo-HCT transplant is to occur within 150 days of auto-HCT. Post-allo-HCT infusion treatment includes cyclosporine and mycophenolate mofetil (MMF) Subject's participation ends if a suitable matched donor is not identified within the 150 days. Pre-medication treatments administered during this study may include acetaminophen; diphenhydramine; hydrocortisone; and methylprednisolone.