How Are Drugs Designed?

Drug design is the process of finding new drugs based on the understanding of the disease and the structure and function of a biological target molecule involved in the disease. Once these are known, chemical compounds  are  synthesized  with  structures that allow them to bind to and alter the behavior of the target. The structures of  these  compounds  are  progressively refined,  often  using  computer-modeling, to fit even better with the target. In addition to being able to bind to the target, a drug must be able to pass through barriers our body puts in its path. It must be able to adequately withstand the body’s protective mechanisms that reject or decompose it. Ultimately, the body should be able to eliminate and remove the drug. This systematic approach to new drug discovery is called rational drug design.

In  the  past,  most  drugs  were  discovered through a search of natural sources such as plants and microorganisms, or by the synthesis of an extensive number of compounds of varying structures. These synthetic  or  natural  compounds  were then tested for various kinds of biological activities  in  the laboratory.  This  type  of trial-and-error  approach,  called random screening, resulted in the discovery and development  of  many  important  drugs. It still has a place in drug discovery and is  often  used  by pharmaceutical  companies  to  identify lead  compounds.  These lead  compounds  are  then  synthetically modified  to  give  new  compounds  with improved properties.

Most drugs are small organic molecules produced through chemical synthesis, but biopharmaceutical drugs (also known as biologics)  produced  through  biological processes are becoming increasingly more common. [Source: Introduction to Pharmaceutical Sciences]