The use of inotuzumab ozogamicin in children with relapsed/refractory B-lineage acute lymphoblastic leukemia

Today, treatment results for acute lymphoblastic leukemia (ALL) look encouraging, yet 10–15% patients still end up relapsing. The success of relapse treatment is directly dependent on whether or not a tumor clone has been completely eradicated before hematopoietic stem cell transplantation (HSCT). Immunotherapy made it possible to achieve minimal residual disease (MRD) – negative remission even in refractory patients. One example of such immunotherapeutic agents is inotuzumab ozogamicin (InO), an anti-CD22 monoclonal antibody conjugated to the cytotoxic agent calicheamicin. We included 17 patients under the age of 18 with relapsed or refractory precursor B-cell ALL (pre-B ALL) who had been treated with InO at the Dmitry Rogachev National Medical Research Center of Pediatric Hematology, Oncology and Immunology of Ministry of Healthcare of Russia from 01.10.2016 to 01.09.2022. The study was approved by the Independent Ethics Committee and the Scientific Council of the Dmitry Rogachev National Medical Research Center of Pediatric Hematology, Oncology and Immunology. The efficacy of the therapy was assessed based on the patients’ morphological response, MRD negativity and overall survival. Treatment toxicity was assessed according to CTCAE 5.0 (Common Terminology Criteria for Adverse Events). Statistical analysis was performed using the XLSTAT 2016 software. The majority of the patients (75%) responded to the therapy. MRD negativity was achieved in 41.2% of the study patients. The one-year overall survival rate was 40.3% (95% confidence interval 14.8–65.7). The treatment was well tolerated but 33% of the patients treated with standard-dose InO and subsequent HSCT developed veno-occlusive disease/sinusoidal obstruction syndrome. In our study, we demonstrated the high efficacy of InO both when used as a rescue therapy in patients with relapsed/refractory pre-B ALL and as a bridging therapy in patients before HSCT.