The first synthetic antimicrobial drug, arsphenamine, discovered in 1909 by Sahachiro Hata in the laboratory of Paul Ehrlich, is not toxic to bacteria until it has been converted to an active form by the body.
4-Androstenediol, a steroid androgen which acts as a prodrug to testosterone
Codeine is an example of a prodrug, which is metabolized in the body to the opiate known as morphine.