CAY10398 is an inhibitor of histone deacetylase (HDAC1) with an IC50 value of 10 μM. Similar potency is observed with trapoxin A and B, whereas trichostatin A is more potent inhibitor of the enzyme. Trichostatin A also selectively inhibits the removal of acetyl groups from the amino-terminal lysine residues of core histones, which modulates the access of transcription factors to the underlying genomic DNA. However, trichostatin A is much more expensive than CAY10398. CAY10398 thus represents a selective and cost-effective compound for the inhibition of HDAC.