The experimental design is a bicentric non-controlled fixed-dose Phase I/II study. A total of 20 adult patients with acute steroid-resistant GVHD will be enrolled in a 12 months period. The treatment consists of a standard dose of 4 infusions T-Guard (4 mg/m2), given 48-hours apart over a 4-hour period. The intended follow-up period is 6 months.