Biochemical approach to new medications

In this plenary symposium address, the author describes historically his progress from the antimetabolite 2,6-diaminopurine to 6-mercaptopurine as a useful drug against tumours and leukaemia. Subsequently a 6-mercaptopurine derivative, and eventually azathioprine, were discovered to be useful drugs to ensure kidney transplant acceptance. Several of his group's diaminopurines proved to be selective antifolates in combatting pathogenic bacteria when combined with sulfanilamide, a useful drug combination already estimated to have saved a million lives.