Antithymocyte Globulin, Clofarabine, and Rituximab in Treating Patients After an Unsuccessful Stem Cell Transplant

OBJECTIVES: Primary * To determine the rate of sustained donor engraftment at 42 days and survival at 100 days post transplantation in patients treated with anti-thymocyte globulin, clofarabine, and rituximab. Secondary * To determine incidence of treatment-related mortality at day 100 post transplantation. * To determine incidence of neutrophil recovery by day 42 post transplantation. * To determine survival at day 100 and 1 year post transplantation. * To determine the proportion of patients with chimerism at day 28 post transplantation. * To determine incidence and severity of grades II-IV acute graft-vs-host disease by day 100 post transplantation. OUTLINE: * Conditioning regimen: Patients receive rituximab intravenously (IV) on day -7, anti-thymocyte globulin IV over 4-6 hours on days -6 to -4, and clofarabine IV over 1 hour on days -4 to -2. * Hematopoietic stem cell transplantation (HSCT): Patients undergo HSCT on day 0. Patients may receive umbilical cord blood, peripheral blood stem cells, or bone marrow from unrelated or related donors. * Graft-vs-host disease (GVHD) prophylaxis: Patients receive oral cyclosporine twice daily or cyclosporine IV every 8 hours beginning on day -3 and continuing for 100 or 180 days post transplantation followed by a taper; mycophenolate mofetil IV every 8 hours beginning on day -3 and continuing for 30 days (or 7 days after engraftment with no evidence of GVHD); and filgrastim (G-CSF) IV once daily beginning on day 1 and continuing until blood counts recover. After completion of study therapy, patients are followed on days 100, 180, and 360.