Study of IL-22 IgG2-Fc (F-652) for Subjects With Grade II-IV Lower GI aGVHD

This is a Phase IIa single arm open-label study to investigate the safety, tolerability, and PK of F-652 in combination with systemic corticosteroids in subjects who have undergone HSCT and have newly diagnosed grade II-IV lower GI aGVHD. The HSCT may be derived from bone marrow, peripheral blood stem cells, or cord blood. The PK of F-652 in this subject population will be investigated. Subjects may be replaced if subject withdrawal is not related to safety or treatment response. F-652 will be administered in conjunction with prednisone (or equivalent) at the time of the onset of clinical symptoms consistent with GI and/or liver aGVHD. Prednisone (or equivalent) will be given at a dose of 2 mg/kg/day and tapered as per protocol. F-652 will be administered intravenously at a rate of 100 mL/hour for one hour once per week for four weeks. A total of 4 doses will be administered at a dose of 45 μg/kg each. Subjects will be followed for safety and efficacy through Day 180, and subject survival status will be collected at Day 365. In the first stage of the trial, a total of 16 subjects will be enrolled. If six or fewer have a Day 28 treatment response, the trial will close due to a lack of efficacy. If seven or more have a response, an additional 11 subjects will be enrolled into study for a total sample size of 27. During the course of a subject's therapy, dose reduction may occur on an individual basis as per protocol.