2-Chlorodeoxyadenosine activity in patients with untreated chronic lymphocytic leukemia

2-chlorodeoxyadenosine (2-CdA; cladribine) is a purine analog with activity in patients with chronic lymphocytic leukemia (CLL) who fail to respond to alkylator therapy. We conducted a phase II trial of 2-CdA in previously untreated CLL patients.

2-CdA was administered to 20 patients with previously untreated CLL as a 0.1-mg/kg/d 7-day continuous intravenous infusion every 28 to 35 days until maximum response or prohibitive toxicity.

A median of four courses (range, one to nine) was administered to each patient. Five patients (25%) achieved a complete response and 12 (60%) achieved a partial response, for an overall response rate of 85%. The median response follow-up duration was 8+ months (range, 3 to 27). Myelosuppression was the principal toxicity. Four of 20 patients (20%) experienced grade III or IV thrombocytopenia. Three patients, all of whom received corticosteroid therapy, developed opportunistic infections at a median of 19 months following discontinuation of 2-CdA therapy.

2-CdA has major activity in patients with previously untreated CLL, and the lower response rates seen in previously treated patients may be due in part to poor marrow reserve from prior therapy. Determination of the relative effectiveness of 2-CdA, fludarabine, and chlorambucil in the treatment of CLL patients will require a randomized trial.