Thus, the therapeutic potential of HDAC inhibitors had been investigated in RA and many HDAC inhibitors have been developed, e.g., the pan HDAC inhibitors, such as ITF 2357 and SAHA, inhibit all HDACs, and the selective HDAC inhibitors, such as Tubastatin A and Tubacin, inhibit HDAC6 specifically [142]. This evidence concerns the gene HDAC9 and rheumatoid arthritis.