Prevention of acute graft-versus-host disease in adult T-cell leukemia-lymphoma patients who received mogamulizumab before allogeneic hematopoietic cell transplantation.

Mogamulizumab (Mog) is effective against adult T-cell leukemia-lymphoma (ATL), but as we reported previously, Mog increases the incidence of severe acute GVHD when administered before allogeneic hematopoietic cell transplantation (allo-HCT). Here, we report the cases of two ATL patients who did not develop acute GVHD despite receiving Mog before allo-HCT. Case 1: a 63-year-old female who underwent allo-HCT from an HLA-matched donor 2 months after the last dose of Mog. Case 2: a 47-year-old male with ATL that relapsed 3 months after first allo-HCT. He received eight doses of Mog and underwent a second allo-HCT from a haploidentical donor 4 months after the last dose of Mog. Mog blood levels were measured and lymphocytes analyzed by mass cytometry. Mog blood levels measured before starting the conditioning regimens were low. A small proportion of regulatory T cells (Tregs) was detected before and shortly after allo-HCT. When using Mog before allo-HCT, it is important to consider the number of Mog doses and the interval from the last dose of Mog to allo-HCT. Analyzing Mog blood levels and Treg counts before and after allo-HCT should also be useful.