Phase II Study of Tocilizumab for Patients With Glucocorticoid-refractory Acute GVHD After Allogeneic Hematopoetic Stem Cell Transplant (HSCT)

Inclusion Criteria: * Men or women ≥ 18 and ≤ 80 years of age * Karnofsky Performance Status Scale ≥ 50% * Glucocorticosteroid refractory acute GVHD Grade 2-4 by the Glucksberg functional classification. * Patients who had experienced aGVHD grade 2-4 and responded to glucocorticosteroids in the past then had a flare of aGVHD requiring increasing immune suppression to 1 mg/kg of prednisone or equivalent are eligible for this study if they are refractory to steroids and provided that they did not receive a second line therapy for aGVHD in the past. * Glucocorticosteroid refractory GVHD is defined as the following: * No response to corticosteroid therapy at ≥ 1.0 mg/kg methylprednisolone or equivalent after the onset of acute GVHD for a minimum of 3 and a maximum of 7 days OR * Progression of at least 1 overall grade within 3 days of glucocorticosteroid use OR * Incomplete response by 14 days of glucocorticosteroid use * Ability to comply with planned procedures * Ability to understand the information provided and to provide written evidence of informed consent * Willingness of females of childbearing potential to use adequate contraception. * Post-menopausal for at least 1 year or surgical sterilization or hysterectomy at least 3 months prior to screening Exclusion Criteria: * Subjects with only grade 1 acute GVHD * Concurrent medical condition or disease that may interfere with clinical trial participation * Relapsed or persistent malignancy. * Receiving other drugs for the treatment of glucocorticosteroid refractory GVHD. * Severe hepatic veno-occlusive disease or sinusoidal obstruction syndrome. * History of hypersensitivity or severe allergic reactions to humanized or murine monoclonal antibodies * Receipt of any experimental, unregistered therapy within or outside a clinical trial within 30 days or 5 plasma half-lives (whichever is shorter) before dosing * Planned or current participation in any other clinical trial for treatment of GVHD during this clinical trial. Subjects are permitted on this trial if 30 days (or 5 half-lives) have passed since enrollment on other investigational drugs. If a subject develops another condition, he/she is permitted on other clinical trials to treat that condition. Subjects are not permitted to go on other clinical trials for steroid refractory acute GVHD. Subjects are permitted to participate in trials for chronic GVHD. * Pregnancy (a negative serum or urine pregnancy test should be performed for all women of childbearing potential within 7 days of treatment) or lactation. * Pre-existing or recent onset of demyelinating disorders * Pre-existing or recent onset of gastrointestinal perforation * Treatment with any investigational agent within 4 weeks of screening or 5 half-lives of the investigational drug (whichever is longer) * Receipt of a live vaccine within 4 weeks prior to first infusion * Previous treatment with Natalizumab (Tysabri®) * History of severe allergic or anaphylactic reactions to humanized or murine monoclonal antibodies * Known active UNCONTROLLED bacterial, viral, fungal, mycobacterial, or other infection (including tuberculosis or atypical mycobacterial disease, but excluding fungal infections of nail beds). * Concomitant malignancies. * History of psychiatric disorder that would interfere with normal participation in this protocol * Significant cardiac or pulmonary disease (including obstructive pulmonary disease) * ANC \< 0.5 x 103 * History of drug, alcohol, or chemical abuse within 6 months prior to screening * Serum creatinine \> 1.9 mg/dL (168 µmol/L). Patients with serum creatinine values exceeding limits may be eligible for the study if their estimated glomerular filtration rates (GFR) are \>30 * Alanine aminotransferase (ALT) or aspartate aminotransferase (AST) \> 3 times upper limit of normal (ULN) unless liver GVHD is suspected * Any other disease, metabolic dysfunction, physical examination finding, or clinical laboratory finding giving reasonable suspicion of a disease or condition that contraindicates the use of an investigational drug or that may affect the interpretation of the results or render the patient at high risk from treatment complications