Demethylating agents are compounds that can inhibit methylation, resulting in the expression of the previously hypermethylated silenced genes (see Methylation#Cancer for more detail). Cytidine analogs such as 5-azacytidine (azacitidine) and 5-azadeoxycytidine (decitabine) are the most commonly used demethylating agents . These compounds work by binding to the enzymes that catalyse the methylation reaction, DNA methyltransferases; and titrate out these enzymes. Both compounds have been approved in the treatment of Myelodysplastic syndrome (MDS) by Food and Drug Administration (FDA) in United States. Azacitidine and decitabine are marketed as Vidaza and Dacogen respectively. Azacitidine is the first drug to be approved by FDA for treating MDS and has been given orphan drug status.Procaine is a DNA-demethylating agent with growth-inhibitory effects in human cancer cells.