Cytosine arabinoside combines a cytosine base with an arabinose sugar. It is an antimetabolic agent with the chemical name of 1β-arabinofuranosylcytosine. 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 deoxycytosine to be incorporated into human DNA, but different enough that it kills the cell. Cytosine arabinoside interferes with the synthesis of DNA. Its mode of action is due to its rapid conversion into cytosine arabinoside triphosphate, which damages DNA when the cell cycle holds in the S phase (synthesis of DNA). Rapidly dividing cells, which require DNA replication for mitosis, are therefore most affected. Cytosine arabinoside also inhibits both DNA and RNA polymerases and nucleotide reductase enzymes needed for DNA synthesis.<unk>  is the first of a series of cancer drugs that altered the sugar component of nucleosides. Other cancer drugs modify the base.<unk>  is often given by continuous intravenous infusion, which follows a biphasic elimination – initial fast clearance rate followed by a slower rate of the analog.<unk>  is transported into the cell primarily by hENT-1. It is then monophosphorylated by deoxycytidine kinase and eventually<unk> -5´-triphosphate, which is the active metabolite being incorporated into DNA during DNA synthesis. Several mechanisms of resistance have been reported.<unk>  is rapidly deaminated by cytidine deaminase in the serum into the inactive uracil derivative.<unk> -5´-monophosphate is deaminated by deoxycytidylate deaminase, leading to the inactive uridine-5´-monophosphate analog.<unk> -5´-triphosphate is a substrate for SAMHD1. Furthermore, SAMHD1 has been shown to limit the efficacy of<unk>  efficacy in patients. When used as an antiviral,<unk> -5´-triphosphate functions by inhibiting viral DNA synthesis.<unk>  is able to inhibit herpesvirus and vaccinia virus replication in cells during tissue culture. However,<unk>  treatment was only effective for herpesvirus infection in a murine model.
Cytarabine
Fludarabine
Clofarabine
Cladribine
Nelarabine
Vincristine
Ifosfamide
Cyclophosphamide