[Cladribine].

Cladribine (2-chlorodeoxyadenosine: 2-CdA) is a chlorinated purine analogue that is resistant to degradation by adenosine deaminase. Phosphorylated derivatives of 2-CdA accumulate in lymphocytes with high deoxycytidine kinase activity, resulting in DNA strand breaks and cell death. Since the cytotoxic properties of 2-CdA are independent of cell division, 2-CdA is expected to be an effective agent in the treatment of indolent lymphoid malignancy with low-growth fraction. The agent was synthesized and has been investigated extensively by researchers at the Scripps Clinic and Research Foundation in the United States. The FDA approved cladribine for use against hairy cell leukemia, in 1993, and it was approved against hairy cell leukemia and indolent B-cell lymphoma in Japan in 2002 as Leustatin (Janssen Pharma Co. Ltd., Tokyo, Japan). The efficacy, toxicity and clinical usefulness of this agent against indolent lymphoid malignancies will be described according to the data from several clinical trials conducted in the United States, European countries and Japan.