Drug discovery in the past and, to a lesser extent, at present has been (is) based on molecular manipulation of natural products. In this way, selective local anesthetics have been developed from cocaine
From atropine via pethidine, potent morphinomimetics, anti‐tussives, anti‐diarrhea agents and neuroleptics of the butyrophenone type have been developed.
New lead compounds can also be discovered by general pharmacological screening of new chemical entities, synthesised with a certain pharmacological property in view, but lacking the expected potency. The discovery of the anti‐ulcer agent omeprazole is an example of this approach. Chemical manipulation of known bioactive compounds may also lead to new drugs. The possibility of rational design of new, highly sophisticated and specific drugs depends largely on progress made in the exact understanding, at the molecular level, of agonist/antagonist‐receptor and protein‐protein interactions.