Report of a phase II study of clofarabine and cytarabine in de novo and relapsed and refractory AML patients and in selected elderly patients at high risk for anthracycline toxicity.

PURPOSE: To determine the efficacy and safety of clofarabine and cytarabine (Ara-C) in adult patients with relapsed or refractory acute myeloid leukemia (AML) and in elderly patients with untreated AML and heart disease.

PATIENTS AND METHODS: Patients with relapsed/refractory AML and older patients for whom there was a concern over toxicity from additional anthracyclines received 5 days of clofarabine, 40 mg/m(2) per day i.v. over 1 hour, followed 4 hours later by Ara-C, 1,000 mg/m(2) per day i.v. over 2 hours.

RESULTS: Thirty patients were enrolled. The median age was 67 years (range, 38-82 years) and 18 (60%) had received at least one prior therapy. Eleven (37%) patients had a history of cardiovascular disease and were considered to be at high risk for anthracycline toxicity. High-risk cytogenetic abnormalities were present in 14 (47%) patients. The overall response rate (complete remission [CR] plus partial remission) was 53%, including a CR in 14 patients (47%). Responses were observed in all cytogenetic risk groups and in patients who had received up to five prior therapies. The median disease-free survival interval was 9.5 months. The 30-day mortality rate was 20% (de novo AML, 8%; relapsed/refractory AML, 28%). Of the 14 patients achieving a CR, half were able to proceed to curative hematopoietic stem cell transplantation.

CONCLUSIONS: Clofarabine in combination with Ara-C is effective in both untreated and previously treated patients with AML. In addition, it represents a useful remission induction strategy to serve as a bridge to transplantation in older patients with AML.