Wiley Acta Medica Okayama 2688-6146 5 4 2024 Combination of reduced post-transplant cyclophosphamide and early tacrolimus initiation increases the incidence of chronic graft-versus-host disease in human leukocyte antigen-haploidentical peripheral blood stem-cell transplantation 810 814 EN Toshiki Terao Department of Hematology and Oncology, Okayama University Hospital Takumi Kondo Department of Hematology and Oncology, Okayama University Hospital Makoto Nakamura Department of Hematology and Oncology, Okayama University Hospital Hiroki Takasuka Department of Hematology and Oncology, Okayama University Hospital Hideaki Fujiwara Department of Hematology and Oncology, Okayama University Hospital Noboru Asada Department of Hematology and Oncology, Okayama University Hospital Daisuke Ennishi Department of Hematology and Oncology, Okayama University Hospital Hisakazu Nishimori Department of Hematology and Oncology, Okayama University Hospital Keiko Fujii Department of Hematology and Oncology, Okayama University Hospital Nobuharu Fujii Department of Hematology and Oncology, Okayama University Hospital Yoshinobu Maeda Department of Hematology and Oncology, Okayama University Hospital Ken-Ichi Matsuoka Department of Hematology and Oncology, Okayama University Hospital We evaluated the clinical impacts of the concurrent modification of post-transplant cyclophosphamide (PTCy) dose and tacrolimus (Tac)-initiation timing in 61 patients with human leukocyte antigen-haploidentical transplantation. Reduced-dose PTCy (80 mg/kg) was associated with a higher incidence of moderate-to-severe chronic graft-versus-host disease (GVHD) than standard-dose PTCy (100 mg/kg) (35.0% vs. 26.6%, p = 0.053). Notably, early-initiation Tac (day -1) increased moderate-to-severe chronic GVHD than standard-initiation Tac (day 5) in the reduced-dose PTCy group (p = 0.032), whereas Tac-initiation timing did not impact chronic GVHD in the standard-dose PTCy group. These data indicate that the combination of reduced-dose PTCy and early-initiation Tac can amplify chronic GVHD. No potential conflict of interest relevant to this article was reported.