The study will enroll approximately 44 subjects in three parts:~Part 1 is an open label 3+3 single dose escalation phase and will enroll approximately 30 subjects with aGVHD across 4 cohorts, where subjects will receive Itolizumab administered intravenously for 1 dose.~Part 2 is an open label phase and subjects from part 1 will receive Itolizumab administered intravenously every two weeks for a total of 4 doses.~Part 3 is a randomized phase and will enroll approximately 14 additional subjects, randomized in a 1:1 ratio to one of the 2 recommended doses provided by Part 1 and Part 2. Subjects will receive Itolizumab administered intravenously every two weeks for a total of 5 doses.
To evaluate the safety, tolerability, PK, PD, and clinical activity of Itolizumab in subjects with Newly diagnosed Acute Graft Versus Host Disease(aGVHD).