On Dec. 7, 1953, the U.S. Food and Drug Administration (FDA) approved methotrexate, an antimetabolite derived from folic acid, and 6-mercaptopurine as anticancer drugs. 6-TG and 6-MP were codeveloped by Gertrude Elion and George Hitchings, who received the Nobel Prize for development of these and other anticancer agents.

Methotrexate was originally used to treat pediatric acute lymphoblastic leukemia (ALL). It’s an antimetabolite, a type of chemotherapy drug that prevents cancer cells from replicating. Methotrexate works by blocking the body’s use of folic acid.