Joel this is really one of the great stories in medicine. Farber is truly a hero. Using a folate look alike- poison was a conceptual breakthrough, The person who actually designed the molecule was Yellapragada Subbarow, from Lederle another giant of his times. His wikipedia page intro is below for those interested: "Yellapragada Subbarow (12 January 1895 – 8 August 1948) was an Indian biochemist who discovered the function of adenosine triphosphate as an energy source in the cell, and developed methotrexate for the treatment of cancer. Most of his career was spent in the United States. Despite his isolation of ATP, Subbarow was denied tenure at Harvard[1][2] though he would lead some of America's most important medical research during World War II. Subbarow died in the United States.[3] Subbarow is also credited with the first synthesis of the chemical compounds folic acid and methotrexate. Subbarow's colleague, George Hitchings, who shared the 1988 Nobel Prize in Physiology or Medicine with Gertrude Elion, said, "Some of the nucleotides isolated by Subbarow had to be rediscovered years later by other workers because Fiske, apparently, did not let Subbaow...