I3 may be a potential HDAC inhibitor worthy of further investigation including the molecular mechanism of cell differentiation of KG-1, MOLM-13, and THP-1 cells and the anti-proliferation activity on other AML cell lines and development to surmount the differentiation block in AML patients with t (8; 21) translocation or MLLr and leukemic stem-like cells. Here, HDAC9 is linked to acute myeloid leukemia.