The purpose of this study is to find out whether siplizumab is safe and effective for
patients with SCD undergoing an allogeneic transplant and to prevent development of Graft
versus Host Disease (GVHD) and graft failure. The main goals of this study are :
- To determine if acute GVHD occurs and how severe the acute GVHD is in subjects receiving
the study drug
- To determine if graft failure occurs in subjects receiving the study drugs
In this study, participants will receive 5 infusions of the study drug, siplizumab, while
getting a stem cell transplant for SCD. Before siplizumab infusion, participants will be
given medications to reduce the risks of allergic reaction to the drug.