Rhenium 188-labeled anti-CD66 (a, b, c, e) monoclonal antibody to intensify the conditioning regimen prior to stem cell transplantation for patients with high-risk acute myeloid leukemia or myelodysplastic syndrome: results of a phase I-II study

The conditioning regimen prior to stem cell transplantation in 36 patients with high-risk acute myeloid leukemia (AML) and myelodysplastic syndrome (M DS) was intensified by treating patients with a rhenium 188-labeled anti-CD 66 monoclonal antibody. Dosimetry was performed prior to therapy, and a fav orable dosimetry was observed in all cases. Radioimmunotherapy with the lab eled antibody provided a mean of 15.3 Gy of additional radiation to the mar row; the kidney was the normal organ receiving the highest dose of suppleme ntal radiation (mean 7.4 Gy). Radioimmunotherapy was followed by standard f ull-dose conditioning with total body irradiation (12 Gy) or busulfan and h igh-dose cyclophosphamide with or without thiotepa. Patients subsequently r eceived a T-cell-depleted allogeneic graft from a HLA-identical family dono r (n = 15) or an alternative donor (n = 17). In 4 patients without an allog eneic donor, an unmanipulated autologous graft was used. Infusion-related t oxicity due to the labeled antibody was minimal, and no increase in treatme nt-related mortality due to the radioimmunoconjugate was observed. Day +30 and day +100 mortalities were 3% and 6%, respectively, and after a median f ollow-up of 18 months treatment-related mortality was 22%. Late renal toxic ity was observed in 17% of patients. The relapse rate of 15 patients underg oing transplantation in first CR (complete remission) or second CR was 20%; 21 patients not in remission at the time of transplantation had a 30% rela pse rate.