Cladribine for the treatment of hairy cell leukemia and chronic lymphocytic leukemia

Cladribine (Leustatin; Janssen-Cilag, Ortho Biotech Inc, Raritan, NJ) is a novel injectable nucleoside analogue with marked efficacy against hairy cell leukemia and considerable, although less dramatic, activity against chronic lymphocytic leukemia and non-Hodgkin's lymphoma. The effect is thought to be due to the drug's ability, after intracellular phosphorylation, to inhibit repair of single-strand DNA breaks in certain malignant lymphocyte and monocyte subtypes. We treated 49 patients with active hairy cell leukemia with continuous infusion of cladribine at a dose of 0.1 mg/kg/ d for 7 days. A single course of therapy gave a complete response rate of 76% and a partial response rate of 24%; the effect was durable for several years in most cases. We also treated 14 patients with chronic lymphocytic leukemia with cladribine and obtained an overall response rate of 43%; this required several courses of monthly treatment. These responses tended to be short-lived and did not substantially change life expectancy of chronic lymphocytic leukemia patients. In both diseases, myelosuppression and immunosuppression, sometimes resulting in neutropenic fever, were the only toxicities associated with cladribine.