By multivariable analysis (Table S2), active pretransplant disease (SD/PD) relative to CR status and HLA‐DRB1 mismatching in the GVHD direction remained independent predictors for increased risk of grade ≥3 CRS (HR: 14.3, P = .001, and HR: 17.2, P = .003, respectively). Here, HLA-DRB1 is linked to graft versus host disease.