Cytarabine, or cytosine arabinoside, is a chemotherapy agent used mainly in the treatment of cancers of white blood cells such as acute myeloid leukemia (AML) and non-Hodgkin lymphoma. It is also known as Ara-C (Arabinofuranosyl Cytidine). It kills cancer cells by interfering with DNA synthesis.
It is called cytosine arabinoside because it combines a cytosine base with an arabinose sugar. Cytosine normally combines with a different sugar, deoxyribose, to form deoxycytidine, a component of DNA. Certain sponges, where it was originally found, use arabinoside sugars to form a different compound (not part of DNA). Cytosine arabinoside is similar enough to human cytosine deoxyribose (deoxycytidine) to be incorporated into human DNA, but different enough that it kills the cell. This mechanism is used to kill cancer cells. Cytarabine is the first of a series of cancer drugs that altered the sugar component of nucleosides.