The Emperor of All Maladies

by Siddhartha Mukherjee

The chemical reactions to make folic acid brought a serendipitous bonus. Since the reactions had several intermediate steps, Subbarao and Kiltie could create variants of folic acid through slight alterations in the recipe. These variants of folic acid—closely related molecular mimics—possessed counterintuitive properties. Enzymes and receptors in cells typically work by recognizing molecules using their chemical structure. But a “decoy” molecular structure—one that nearly mimics the natural molecule—can bind to the receptor or enzyme and block its action, like a false key jamming a lock. Some of Yella’s molecular mimics could thus behave like antagonists to folic acid. These were precisely the antivitamins that Farber had been fantasizing about. Farber wrote to Kiltie and Subbarao asking them if he could use their folate antagonists on patients with leukemia. Subbarao consented. In the late summer of 1947, the first package of antifolate left Lederle’s labs in New York and arrived in Farber’s laboratory.