JAK1 and graft versus host disease: In the past decade, a number of methods have proved efficacy in the optimization of current GVHD prophylaxis regimens including the addition of tocilizumab [40] and vedolizumab [41] et al. As a selective JAK1/2 signaling inhibitor, ruxolitinib has been proven effective in the treatment of steroid-refractory GVHD [12, 13].