The primary analysis of this hypothesis generation study is to estimate the composite endpoint of GVHD-free and corticosteroids-free survival at 12 months after randomization in both treatment arms. In fact, it is more and more established that such composite endpoint is a clinically very relevant one because it represents ideal recovery from allo-SCT (Stem Cell transplantation) (at 1 year after acute GVHD diagnosis) and a measure of cure without ongoing morbidity.