Second unrelated cord blood transplantation using a reduced-intensity conditioning regimen combined with gemtuzumab ozogamicin in patients with relapsed acute myelogenous leukemia

Gemtuzumab ozogamicin (GO) is an effective molecular-targeted agent for CD33-positive acute myelogenous leukemia (AML) patients who are resistant to conventional chemotherapy. Recent prospective trials have revealed the safety and efficacy of GO as part of conditioning following allogeneic bone marrow or peripheral blood stem cell transplantation (SCT). We report here for the first time three AML cases that relapsed after allogeneic SCT and underwent unrelated cord blood transplantation (UCBT) following reduced-intensity conditioning (RIC) comprising fludarabine, melphalan, and low-dose total body irradiation combined with GO. Primary neutrophil engraftment occurred in all cases, while recovery of platelet count was delayed. Only one case of reversible hepatic sinusoidal obstruction syndrome was documented. Non-relapse mortality at day 100 was not documented. Notably, one patient who responded to GO survived for 6 months after UCBT in remission with excellent performance status, while the remaining cases relapsed early. These data suggest that GO may be safely combined with RIC for UCBT after previous allogeneic SCT.