However, 55% of patients developed GVHD already after 1–2 doses of anti-PD-1 treatment, including grade III-IV GVHD in 9 patients and 8 deaths related to treatment-emergent GVHD (4 acute GVHD and 4 chronic GVHD) (63). This evidence concerns the gene PDCD1 and graft versus host disease.