HDAC8 inhibition enhances elimination of FLT3-ITD⁺ AML in vivo in combination with TKIs. (A) T-cell–depleted primary human FLT3-ITD⁺ AML cells were injected into sublethally irradiated (250 cGy) NOG mice (2 × 10⁶ cells per mouse). After engraftment was confirmed, mice were treated for 4 weeks with vehicle (control), AC220 (10 mg/kg per day, by mouth), 22d (100 mg/kg per day, intraperitoneally), or AC220 + 22d (n = 20 per group). Engraftment of human cells was analyzed by flow cytometry. Survival analysis and secondary transplantation were also performed. (B) Representative results for CD45 and CD33 expression from AML #3 and AML #14. Percentage (C) and number (D) of human CD45⁺ cells from AML #3 and AML #14 in the bone marrow (BM) of treated mice. Percentage (E) and number (F) of human CD45⁺CD34⁺ cells from AML #3 and AML #14 in the BM of treated mice. (G) The survival of mice transplanted with 4 different samples was displayed respectively (n = 10 per group). (H) Percentage of CD34⁺ cells within the human CD45⁺ population from AML #3 and AML #14. Percentage (I) and number (J) of human CD45⁺ cells (AML #3 and AML #14) in the BM of secondary recipient mice at 12 weeks. Data are mean ± standard error of the mean. *P < .05, **P < .01, ***P < .001, ****P < .0001.