Southwest Oncology Group Study S0530: a phase 2 trial of clofarabine and cytarabine for relapsed or refractory acute lymphocytic leukaemia

Clofarabine and cytarabine target different steps in DNA synthesis and replication, are synergistic in vivo, and have non-overlapping toxicities, making this combination a potentially promising treatment for acute lymphocytic leukaemia. Thirty-seven patients were treated. The median age was 41 years, 44% of patients were either in ≥2nd relapse or had refractory disease and 59% of patients had poor risk cytogenetics. Six out of 36 patients (17%) achieved a complete remission with or without complete count recovery; median overall survival was 3 months. Nucleoside transporter expression did not predict outcome. This regimen lacked sufficient activity to warrant further testing.