Clofarabine in Chinese Pediatric Patients With Refractory or Relapsed Acute Lymphoblastic Leukemia

Inclusion Criteria: * Pediatric patients (younger than 21 years old) with acute lymphoblastic leukemia confirmed by histology * Refractory or relapsed acute lymphocytic leukemia who had received at least two drugs treatment * No prior chemotherapy within 2 weeks before entry and resolution of toxic effects from prior therapy * Normal cardiac function, adequate hepatic function \[total bilirubin ≤1.5× upper limit of normal (ULN), aspartate aminotransferase (AST) alanine aminotransferase (ALT) ≤ 3ULN\] and renal function (serum creatinine ≤ 2 ULN) * Eastern Cooperative Oncology Group (ECOG) performance status 0-2 * Life expectancy more than 3 months Exclusion Criteria: * AEs not recovered from prior therapy * Within 3 months from allogeneic or autologous stem cell transplantation * With central nervous involvement or uncontrolled infection * Patients who used clofarabine before or allergic to fludarabine or cladribine