Inclusion Criteria:

   1. Diagnosis of skin, gut and/or liver steroid-refractory GVHD by clinical assessment of
   treating physician following allogeneic HCT. Patients who fail to respond to steroids
   by 7 days are considered steroid-refractory

   2. Previously-treated with any conditioning regimen and any GVHD immune suppression
   prophylaxis and formulation of steroids, except as noted in Exclusion Criteria #2.

   3. AbGn-168H (neihulizumab) therapy can begin not more than 14 days after diagnosis of
   aGvHD

   4. Karnofsky Performance Status (KPS) > 50%

   5. No evidence of HCT graft failure or multi-organ failure

   6. Ability to understand and the willingness to sign a written informed consent document

Exclusion Criteria:

   1. Uncontrolled infections not responsive to antimicrobial therapy requiring intensive
   critical care

   2. Progressive malignant disease, including post-transplant lymphoproliferative disease
   unresponsive to therapy

   3. Treatment with investigational GVHD prophylactic agents (eg, CCR5 inhibitors;
   lenalidomide; and/or bortezomib) within the 7 days prior to the 1st dose of
   neihulizumab

   4. Treatment with other investigational agents within the prior 7 days prior to the 1st
   dose of AbGn-168H (neihulizumab)

   5. CMV PCR > 500 copies/mL or evidence of end-organ damage due to CMV

   6. Pregnant or nursing

   7. HIV positivity (NOTE: patients positive for hepatitis B or hepatitis C are not
   excluded, and may be evaluated on a case-by-case basis)

   8. Renal clearance CCR < 40 mL/min