A comparison of several other HDAC inhibitors currently in clinical development confirmed that panobinostat (LBH589) is also a highly potent inhibitor of both HDAC1 activity and tumour cell proliferation in vitro (Bali et al, 2005), while vorinostat (SAHA) showed lower potency towards both HDAC1 and tumour cell proliferation, which is in agreement with previous publications (Butler et al, 2000). This evidence concerns the gene HDAC9 and neoplasm.