Drug Discovery → Two Main Pathways

The distribution of new drugs discovered between 1999 and 2008, according to the discovery strategy. The graph illustrates the number of new molecular entities (NMEs) in each category. Phenotypic screening (i.e., using a disease relevant cellular or in vivo assay) was the most successful approach for first-in-class drugs, whereas target-based screening was the most successful for follower drugs during the period of this analysis.

First-in-class drugs are ones that use a new and unique mechanism of action for treating a medical condition. “Me-too” or “follow-on” drugs are medications similar to pre-existing drugs, usually by making minor modifications to the prototype, reflected in slight changes in the profiles of side effects or activity, and used to treat conditions for which drugs already exist.

Image source: Swinney DC, Anthony J. How were new medicines discovered? Nature Reviews Drug Discovery. 2011 Jun;10:507-19.