What was the first successful drug treatment for leukemia?

Aminopterin was the first successful drug treatment for leukemia.

In 1947, physician Sidney Farber reported temporary remissions in children with acute lymphoblastic leukemia after treating them with aminopterin. The drug blocks folate metabolism, a process rapidly dividing cells need to make DNA. This was one of the first demonstrations that a chemical agent could produce remission in a human cancer.

The responses were not permanent, and aminopterin could cause serious toxicity. Nevertheless, Farber's work established the principle of cancer chemotherapy and helped launch systematic drug treatment for leukemia and other cancers.

Aminopterin is closely related to methotrexate, which later became a more practical and widely used folate antagonist. Imatinib and vincristine are also important leukemia treatments, but they were developed decades after Farber's pioneering 1947 experiments.