Fig. 4

Classic HDAC inhibitors, dual-target HDAC inhibitors, and RPOTAC for HDAC. HDAC inhibitors not only inhibit angiogenesis, cell migration, resistance to treatment, and cell proliferation but also stimulate cell differentiation, apoptosis, and tumor antigenicity. The development of HDAC-targeting treatment ranges from classic HDAC inhibitors, dual-target HDAC inhibitors, and PROTAC for HDACs. Classic HDAC inhibitors are divided into four groups based on structures. The first group is aliphatic carboxylic acid group. None of the HDAC inhibitors of this group have been approved for hematologic malignancy treatment. The second group is hydroxamic acid group and includes vorinostat, belinostat, and panobinostat, which has been approved for treatment of CTCL, PTCL, and MM, respectively. The third group is benzamide group and includes chidamide, which has been approved for the treatment of PTCL. The last group is the cyclic peptide group and includes romidepsin, which has been approved for the treatment of CTCL and PTCL. Furthermore, dual-target HDAC inhibitors have been explored in hematologic malignancy treatment, which also target RTK, JAK2, and PI3K. In additions, PROTAC for HDACs has been developed recently