* By Hitching and Elions in 1944
* Interest in the synthesis of folic acid, purines and pyrimidines as chemotherapeutic agents
* Identified dihydrofolate reductase which is necessary for DNA synthesis.
* Pyrimidine analogues inhibited the enzyme
* Emergent drugs include: Pyrimethamine, Trimethoprim, 6- mercaptopurine, Azathioprine, Aciclovir, Zidovudine