CX-5461 exhibits therapeutic potential in mouse and human AML independent of their p53 status. (A) Leukemia progression and engraftment of M/E p53null AML in recipient C57Bl/6 mice was followed by bioluminescence imaging at day 7 (7 d) prior to initiation of treatment, 14 (14 d), and 21 (21 d) posttransplant (pt). Representative images from n = 20 per group. (B) Kaplan-Meier survival curves for CX-5461 (35 mg/kg every 3 days, start of therapy day 7 pt, and last dose day 31 pt) and vehicle-treated leukemic mice (median survival, 11 days for vehicle vs 24 days for CX-5461; ****P < .0001; n = 20 per group). Gray indicates time of CX-5461 and vehicle treatment. (C) Spleen weight of mice when euthanized (*P = .0132; n = 20 per group). Log-rank test (B) and unpaired 2-tailed Student t test (C) were performed. Graphs represent mean ± SEM. (D) Human leukemia cell lines differ in their sensitivity to Pol I inhibition 48 hours after drug treatment as assessed by PI exclusion (cell viability). IC₅₀ value, the concentration of CX-5461 that decreases cell viability by 50% compared to the control, was calculated using a three-parameter log vs the inhibition nonlinear regression method in GraphPad Prism software. AML cells are graphed in groups: IC₅₀ <100 nM (blue), IC₅₀ 100 nM to 1000 nM (green), and IC₅₀ >1000 nM (red). IC₅₀ values are expressed as the best-fit values for at least n = 3. Graph represents mean ± SEM. (E) The average IC₅₀ for CX-5461 does not correlate with p53 status according to an unpaired 2-tailed Student t test. TP53 mutation status was provided by the Cancer Cell Line Encyclopedia and the Catalogue of Somatic Mutations in Cancer. Only cell lines with known p53 status via these databases are shown in the figure. (F) Cell viability in response to BMH-21 (100 nM, 500 nM, and 1000 nM) and ActD (5 nM) in KASUMI-1, ML-2, MOLM-13, THP-1, MV4-11, SHI-1, and KG-1 was determined by PI exclusion after 48 hours of treatment. DMSO, dimethyl sulfoxide.