Pentostatin (Nipent) in the treatment of chronic lymphocyte leukemia and hairy cell leukemia.

Pentostatin (Nipent), formerly known as deoxycoformycin, is a profound inhibitor of the enzyme adenosine deaminase, resulting in the accumulation of metabolites that inhibit ribonucleotide reductase, which in turn inhibits DNA synthesis. Pentostatin was the first of the purine analogs to undergo extensive testing as an anticancer agent and the first to receive US Food and Drug Administration approval for a treatment indication. It is highly effective as first-line monotherapy in hairy cell leukemia, with a complete response rate of 80% and a 10-year survival rate of around 80%. Pentostatin is also active in chronic lymphocyte leukemia as a single agent, but appears even more promising in combination approaches with the alkylating agents chlorambucil or cyclophosphamide. Due to the increasing recognition of delayed severe stem cell and immune suppression following therapy with other purine analogs, there has been renewed interest in pentostatin, especially in combination with chemotherapy and/or the monoclonal antibody rituximab (Rituxan) in chronic lymphocyte leukemia.