This is a phase II open-label trial designed to evaluate the efficacy of tocilizumab in improving GVHD-free/relapse-free survival (GRFS) after allogeneic hematopoietic cell transplantation (alloHCT) for hematologic malignancy.

The research team earlier hypothesized and demonstrated that tocilizumab could attenuate the incidence of acute GVHD (aGVHD) after myeloablative conditioning (MAC) and reduced intensity conditioning (RIC) Allogeneic hematopoietic cell transplantation (alloHCT), using matched sibling or unrelated donor. In this study, the research team hypothesizes that longer term interleukin 6 (IL-6) inhibition through treatment with tocilizumab by repeated dosing would mediate a beneficial effect not only on the risk of aGVHD, but also on chronic GVHD. This will be achieved by administering an additional dose of tocilizumab at Day +100 post-alloHCT, besides the pretransplant dose, as done in our previous clinical trial, thereby providing total prophylaxis against both acute and chronic GVHD.

Inclusion Criteria:

1. Age ≥18 years.
2. Patients with any hematologic malignancy for which alloHCT is indicated. Patients with acute myeloid leukemia (AML) and acute lymphoblastic leukemia (ALL) must be in complete remission at the time of alloHCT(<5% blasts in the bone marrow, normal maturation of all cellular components in the bone marrow and absence of extramedullary disease).
3. Myeloablative conditioning (MAC) regimen, based on Center for International Blood and Marrow Transplant Research (CIBMTR) criteria.
4. T cell-replete peripheral blood graft.
5. Patients must have a matched related or unrelated donor (at least 6/6 match at human leukocyte antigens (HLA) -A, -B and -C for related donors and at least 8/8 match at HLA-A, -B, -C and -DRB1 for unrelated donors).
6. Cardiac function: Left ventricular ejection fraction ≥45% for myeloablative conditioning.
7. Estimated creatinine clearance ≥40 mL/minute (using the Cockcroft-Gault formula and actual body weight).
8. Pulmonary function: Diffusing capacity of the lungs for carbon monoxide (DLCO) ≥40% (adjusted for hemoglobin) and Forced Expiratory Volume (FEV1) ≥50%.
9. Liver function: total bilirubin <3 x upper limit of normal and alanine aminotransferase (ALT) / aspartate aminotransferase (AST) <5 x upper normal limit.
10. Signed informed consent: Voluntary written consent must be given before patient registration and performance of any study related procedure not part of standard medical care, with the understanding that consent may be withdrawn by the patient at any time without prejudice to future medical care.
11. Female patient: A negative pregnancy test will be required for women of child bearing potential. Breast-feeding or lactation is not permitted.
12. Planned posttransplant maintenance therapy is allowed.

Exclusion Criteria:

1. Prior allogeneic HCT.
2. Active central nervous system (CNS) involvement with malignancy.
3. Patients receiving cord blood or haploidentical allograft.
4. Patients undergoing in vivo or ex vivo T cell-depleted alloHCT.
5. Karnofsky Performance Score <60%.
6. Patients with uncontrolled bacterial, viral or fungal infections (currently on treatment and with progression of infectious disease or no clinical improvement) at time of enrollment.
7. Active hepatitis B or C virus infection or known human immunodeficiency virus (HIV) positive.
8. Prior intolerance or allergy to tocilizumab.
9. Use of rituximab, alemtuzumab, anti-thymocyte globulin (ATG) or other monoclonal antibody planned as part of conditioning regimen for GVHD prophylaxis.
10. History of diverticulitis, Crohn's disease or ulcerative colitis.
11. History of demyelinating disorder.
12. Any current uncontrolled cardiovascular conditions, including uncontrolled ventricular arrhythmias, New York Heart Association (NYHA) class III or IV congestive heart failure, uncontrolled angina, or electrocardiographic evidence of active ischemia or active conduction system abnormalities.
13. Any serious medical or psychiatric illness that could, in the investigator's opinion, potentially interfere with the completion of treatment according to this protocol.

1 year