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

Patient Inclusion Criteria: * Timing of relevant evaluations: Taking in account the need for rapid intervention, if white blood count is less than 200 on day +20, bone marrow aspirate should be performed on day +21. Unless there is an increase in absolute neutrophil count (ANC) to \> 500 in the following 7 days, bone marrow aspirate should be repeated on day +28. If the white blood count is still less than 200 and bone marrow is acellular, bone marrow (BM) or peripheral blood stem cell (PBSC) donor should be reactivated and availability of cord blood (CB) units assessed. If the BM or PBSC donor is not confirmed within 14 days of the request for the donation (typically second donation from the same donor), CB unit should be used instead. Primary or secondary graft failure after hematopoietic stem cell transplantation defined as a \> 50% loss of donor chimerism from previous maximum or less than 25% donor beyond day +42 with pancytopenia and no evidence of relapse. Patients with any diagnosis, type of donor, hematopoietic cell graft or conditioning regimen should be considered for this study. * primary graft failure is defined as: * ANC \< 500 * BM \< 10% on two occasions (Day +21 and Day +28) * Donor chimerism need not to be considered, provided there is no evidence of malignancy * secondary graft failure is defined as \< 5% cellularity and ANC \< 500 for more than 7 days any time after primary engraftment). * Women of childbearing potential must agree to use adeq…