The central focus of this unit is on Paul Ehrlich’s imaginative idea that it should be possible to find chemicals that target and kill disease-causing organisms while leaving normal body cells unharmed – ‘magic bullets’. These ideas led to modern chemotherapy. Students look at  the first modern chemotherapeutic agent –  Paul Ehrlich's arsphenamine, an arsenic compound discovered in 1909 and used to treat syphilis. This was later followed by sulphonamides discovered by Gerhard Domagk and penicillin discovered by Alexander Fleming. Today monoclonal antibodies – many antibodies of the same type – are used to treat a wide array of human diseases including cancer.

There are two activities in this unit. The unit would be suitable after work on drugs and disease. The second activity could also be used for a cover lesson with the questions for homework, before or after the first activity. If students have access to computers, the first part of ‘A story of drug discovery’ could be done on screen.