For example, the current two structurally distinct HDAC inhibitors – SAHA (vorinostat, ZolinzaTM) and FK228 (romidepsin, IstodaxTM), both are reported to have not been effective in clinical trials involving solid tumors i.e. refractory breast, colorectal, non-small cell lung and thyroid cancers [57] and most importantly, these drugs cause serious cardiac toxicity [58]. Here, HDAC9 is linked to thyroid cancer.