Background. Acute myeloid leukemia (AML) accounts for approximately 25% of pediatric leukemia. The long term overall survival rate now approaches 70%, but up 30% relapse. The anti-leukemia properties of Natural Killer (NK) cells and its safety profile has been reported previously at different phases of AML treatment. We proposed a phase II open, a prospective multicenter, non-randomized clinical trial for adoptive infusion of haploidentical K562-mb15-41BBL activated and expanded Natural Killer (NKAE) cells as a consolidation strategy in children with favorable and intermediate-risk AML who were in first complete remission after chemotherapy (NCT02763475). Previous to NKAE cell infusion, patients received a lymphodepleting regimen. After NKAE cell infusion, patients received low doses (1×106/IU/m2) of IL-2 subcutaneously every 48 hours for 2 weeks. Procedure. Seven patients, median age 7.4 years (range, 0.78–15.98), received 13 infusions of NKAE cells, with a median of 36.44×106 NKAE cells/kg (range, 6.92–193.2×106 cells/kg). Results. Three pair donor-recipient were KIR–HLA-mismatched. Donor KIR haplotype score was better in two cases, and neutral in the rest of the cases. Chimerism was observed in 4 patients median chimerism 0.065%, (range 0.05-0.27%). With a median of follow up of 33 moths, 6 (85.7%) patients remain alive and in complete remission. The 3-year overall survival was 83.3% (95% confidence interval 68.1-98.5), and the 3-year relapse cumulative incidence was 28.6% (95% confidence interval 11.5-45.7). Conclusions. This study shows that NKAE cell infusion as a consolidation strategy was feasible and safe but could not improve the pediatric AML relapse rate in this small cohort.

Background: We retrospectively analyzed the data of children with non-malignant diseases who have received a haploidentical hematopoietic stem cell transplant (haplo-HSCT). A total of 31 haplo-HSCT were performed in 26 pediatric patients using ex vivo T cell-depleted (TCD) graft platforms or post-transplantation cyclophosphamide (PT-Cy) from January 2001 to December 2016 in 7 Spanish centres. Procedure: A total of five cases were unmanipulated PT-Cy haplo-HSCT, sixteen received highly purified CD34+ cells, ten were ex vivo TCD graft manipulated either with CD3+CD19+ depletion (n= 1), TCΡαβ+CD19+ selection (n= 7) or naive CD45RA+ T cells depletion (n=2). Peripheral blood stem cells were the only source in patients following TCD haplo-HSCT, and bone marrow was the source for one PT-Cy haplo-HSCT. The most common indications for transplant were primary immune deficiency disorders (PIDs) 18, severe aplastic anemia (SAA) 4, osteopetrosis 2 and thalassemia 2. Results: The 1-year cumulative incidence of graft failure was 27.4 %. The 1-year III-IV acute graft versus host disease (aGvHD) and 1-year chronic graft versus host disease (cGvHD) were 34.6% and 16.7% respectively. Besides, the 2-year overall survival (OS) and the 2-year GvHD-free and relapse-free survival (GRFS) were 44.9% for PIDS and 37.6% for the other NMDs. The TRM at day 100 was 30.8%. Conclusions : These results are discouraged and need to be improved to offer a guaranteed treatment for these patients. Improvements will come if procedures are centralized in centres of expertise. The decision between T-cell depletion platforms will depend on the patients’ underlying diseases, comorbidities, and conditioning regimens.