Suppression of alloreactive T cells in haplo-SCT by itacitinib. Haplo-SCT provides rapid and near universal donor availability, but comes with increased alloreactivity. PtCy depletes alloreactive T cells and thereby reduces GVHD and graft failure. Itacitinib suppresses alloreactive T cells further lowering GVHD damage in target organs (skin, liver, gut).