A hypomethylating agent (or demethylating agent) is a drug that inhibits DNA methylation. Currently available hypomethylating agents block the activity of DNA methyltransferase (DNA methyltransferase inhibitors / DNMT inhibitors). Because DNA methylation affects cellular function through successive generations of cells without changing the underlying DNA sequence, hypomethylating agents are considered a type of epigenetic therapy. Currently two members of the class, azacitidine and decitabine are FDA-approved for use in the United States in myelodysplastic syndrome and are being investigated for use in a number of tumors.
DNA methylation is the modification of DNA nucleotides by addition of a methyl group. These methyl groups are associated with changes in the ability of the corresponding DNA to be used. Patterns of DNA methylation are stable during cellular division. Excessive methylation of tumor suppressor genes in some cancers contributes to the growth and survival of the cancer. Hypomethylating agents decrease the amount of cellular DNA methylation and disrupt these patterns.
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