Preclinical in vivo antileukemia activity of FOXO1 inhibition by AS1842856. (A) Experimental layout, end point analysis. Recipient animals were transplanted with human BCP-ALL (PDX#1: B, D, F; PDX#7: C, E, G), and upon appearance of human ALL in peripheral blood (≥5% huCD19⁺ cells), recipients were treated with either AS1842856 (AS, 50 mg/kg) or DMSO (control, C). At the end of therapy after 11 days, animals were euthanized, and leukemia burden was analyzed in different organ compartments showing clearly decreased leukemia cell numbers in peripheral blood (PB) (B-C), reduced spleen size (D-E), and significantly lower leukemia loads in spleen, bone marrow (BM), and central nervous system (CNS) (F-G), compared with control treated animals. PDX#1 n = 4, PDX#7 n = 5 mice per group, Mann-Whitney U test. (H) Experimental layout, survival analysis. Upon manifestation of human ALL (≥5% huCD19⁺ cells in PB), recipient mice transplanted with PDX#1 were treated with AS1842856 (AS, 30 mg/kg) or DMSO (control, C). At the end of treatment (11 days), mice were followed up and monitored for onset of leukemia-related morbidity indicating leukemia reoccurrence. Reduction of ALL cells in PB (I) and prolonged times without leukemia reoccurrence (J) of recipients treated with AS1842856 compared with control treated recipients. N = 10 per group, Mann-Whitney U test (I) and Kaplan-Meier analysis, log-rank test (J).