HDAC9 and breast cancer: In contrast to SAHA and IDL, treatment of cells with the PI3‐Kδ/HDAC6 inhibitor and its NPs (HSB‐510) has been associated with the lowest IC50 values in all four breast cancer cell lines tested (Table 2), thereby confirming that dual inhibitor is more potent than HDAC inhibitor (SAHA) and the PI3‐K inhibitor (IDL) in a panel of breast cancer cell lines.