In 2001, the drug imatinib mesylate (Gleevec) was shown in a clinical trial to be effective against chronic myelogenous leukemia (CML). Imatinib mesylate was the first anticancer drug developed specifically to target the molecular defect that causes a particular type of cancer.

The preliminary results of an ongoing phase III multicenter randomized study that compared imatinib with interferon plus cytarabine as first-line treatment for CML favored imatinib in terms of efficacy and safety.