Efficacy and safety of inotuzumab ozogamicin as the definitive therapeutic option prior to allogeneic hematopoietic stem cell transplantation for pediatric relapsed/refractory B-cell acute lymphoblastic leukemia.

Among patients with relapsed/refractory (R/R) B-cell acute lymphoblastic leukemia (ALL), those who failed to respond to CD19-directed immunotherapies, there are limited options available pre-HSCT. This study aimed to evaluate the efficacy and safety of Inotuzumab ozogamicin (InO) as the definitive treatment pre-HSCT in patients with R/R B-cell B-ALL. Sixteen patients were enrolled, ten of whom failed treatment with prior CD19-directed immunotherapies, and two of whom relapsed after first HSCT. All patients achieved morphologic complete remission; 13 patients achieved negative measurable residual disease after InO. After bridging to HSCT, the 1-year probabilities of leukemia-free survival and overall survival were 66.5% and 80.8%. One patient developed sinusoidal obstruction syndrome post-HSCT. The prognosis for patients with R/R B-ALL, particularly those who do not respond to prior immunotherapies, is very poor. InO serves as an effective and safe bridging therapy prior to HSCT.