Élie Metchnikoff
In the early 1900s, immunologist Paul Ehrlich proposed the idea of a "Zauberkugel" – "magic bullet", conceived of as a compound which selectively targeted a disease-causing organism, and could deliver a toxin for that organism. This underpinned the concept of monoclonal antibodies and monoclonal drug conjugates. Ehrlich and Élie Metchnikoff received the 1908 Nobel Prize for Physiology or Medicine for providing the theoretical basis for immunology.