Fludarabine phosphate is a purine arabinonucleoside monophosphate having 2-fluoroadenine as the nucleobase. A prodrug, it is rapidly dephosphorylated to 2-fluoro-ara-A and then phosphorylated intracellularly by deoxycytidine kinase to the active triphosphate, 2-fluoro-ara-ATP. Once incorporated into DNA, 2-fluoro-ara-ATP functions as a DNA chain terminator. It is used for the treatment of adult patients with B-cell chronic lymphocytic leukemia (CLL) who have not responded to, or whose disease has progressed during, treatment with at least one standard alkylating-agent containing regimenas. It has a role as an antimetabolite, an antineoplastic agent, an immunosuppressive agent, an antiviral agent, a prodrug and a DNA synthesis inhibitor. It is an organofluorine compound, a nucleoside analogue and a purine arabinonucleoside monophosphate. It is functionally related to a 2-fluoroadenine.