MGCD0103 and FB-MGCD0103 belong to a class of drugs known as histone deacetylase inhibitors (also called HDAC inhibitors). Azacitidine belongs to a class of anti-cancer drugs known as DNA de-methylating agents. Azacitidine (Vidaza®) was approved by the Food and Drug Administration (FDA) in 2004 for the treatment of myelodysplastic syndromes (MDS).