Gertrude Belle Elion (1918 – 1999) was the recipient of one-third of the Nobel Prize for Physiology or Medicine in 1988 for her development of drugs used to treat several major diseases. Working with Fellow Nobel Laureate George H. Hitchings, Elion developed a variety of new drugs that were effective against leukemia, autoimmune disorders, urinary-tract infections, gout, malaria, and viral herpes. Their innovative methods eventually lead to the development of the AIDS drug azydothymidine (AZT). Rather than relying on trial-and-error, Elion and Hitchings examined the differences in the biochemistry of normal human cells versus cancer cells, bacteria, viruses, and other pathogens to create drugs that could kill or inhibit the reproduction of particular pathogens without harming the host cells. This new approach enabled Elion and Hitchings to eliminate much of the guesswork and wasted effort that was typical in developing new therapeutic drugs.