The results of therapy with venetoclax, daratumumab and plerixafor as part of the conditioning regimen in chemotherapy-refractory acute leukemia in children

The main outcomes of allogeneic hematopoietic stem cell transplantation (HSCT) in chemotherapy-refractory acute leukemia remain suboptimal due to a high relapse rate. The incorporation of targeted anti-leukemia agents into the conditioning regimens is a potential approach to improve the efficacy of HSCT. We assessed the safety and potential efficacy of the addition of venetoclax, daratumumab, and plerixafor to the conditioning regimens in children with chemotherapy-refractory acute leukemias who received allogeneic TCRab/CD19-depleted HSCT. We used data from a pilot study, as well as the data of patients from a retrospective cohort who received similar therapy according to the individual indications. 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. All 43 patients (33 acute myeloid leukemias (AML), 8 T-cell acute lymphoblastic leukemias (T-ALL) and 2 acute leukemias of ambiguous lineage) had active disease status at the time of transplantation. The preparative regimen included myeloablative conditioning based on either total body irradiation or treosulfan or melphalan. A haploidentical related donor was used as a graft source in 38 cases, while a fully matched related or unrelated donor was used in 5 cases. The engraftment was observed in 93% of cases, no excessive toxicity was noted. MRD-negative complete remission was achieved in 37 patients (86%). The cumulative incidence of grade II–IV acute graft-versus-host disease (GvHD) was 10%, and the cumulative incidence of chronic GvHD was 5%. At 2 years, transplant-related mortality was 7%, relapse incidence was 52%, event-free survival was 41%, and overall survival was 51%. The overall survival rate for the AML group was 58% and 25% for the T-ALL group. Our data show that the addition of targeted agents to the conditioning regimens is safe, however, does not significantly improve the results of HSCT in the study cohort of patients.