Khaled et al. [20] reported that eight recipients with CYP3A5*1/*1 exhibited a significantly higher cumulative rate of grade 2–4 acute GVHD than recipients with CYP3A5*1/*3 (n = 40) and CYP3A5*3/*3 (n = 122) within 100 days after HSCT. Here, CYP3A5 is linked to acute graft versus host disease.