Clofarabine, a purine nucleoside analog is metabolized to clofarabine 5′-triphosphate, which competes with deoxyadenosine triphosphate for binding to ribonucleotide reductase and DNA polymerase. Clofarabine inhibits DNA synthesis, terminates DNA chain elongation, and inhibits DNA repair resulting in decreased cell replication and repair. Clofarabine disrupts the mitochondrial membrane, which results in the release of proteins, cytochrome C and apoptosis-inducing factor leading to cell death.