Current and future status of haploidentical hematopoietic stem cell transplantation.

Stem cell transplantation from HLA-haploidentical related donors (haploSCT) has been highlighted as an alternative donor source. The regimen consisting of post-transplant cyclophosphamide (PTCY) has been highly prevalent in the US, Europe, and Japan. Considering the status overseas and the current status in Japan, we aim to show our efforts in haploSCT. We initially established the "haplo-full (original)" regimen, which was found to be excessively toxic for general use. Thus, we added ATG to diminish the GVH reaction (haplo-full with ATG). Unfortunately, "haplo-mini (original)" was found to be relatively weak against refractory diseases. Thus, we intensified the preconditioning regimen, which has enabled us to deal with refractory and post-transplant relapse (FAMC-T).  One of the characteristics in haploSCT in Hyogo is the use of steroids from the beginning of SCT. The aim of this strategy is to diminish the inflammation affecting GVHD-target organs, and to suppress chemokine release. Since chemokines produced by the preconditioning regimen are well known to induce GVHD, chemokine suppression should effectively suppress GVHD development. The dependency of the GVL effect on chemokines is unclear, possibly serving as a therapeutic window to separate GVHD from the GVL effect.