Small molecules, big targets: drug discovery faces the protein–protein interaction challenge

The biological rationale for targeting protein–protein interactions as a therapeutic strategy is strong, but identifying viable small-molecule drugs to achieve this has proved highly challenging. This article uses examples of successful discovery efforts to illustrate the research strategies that have proved most useful for different classes of protein–protein interactions. Protein–protein interactions (PPIs) are of pivotal importance in the regulation of biological systems and are consequently implicated in the development of disease states. Recent work has begun to show that, with the right tools, certain classes of PPI can yield to the efforts of medicinal chemists to develop inhibitors, and the first PPI inhibitors have reached clinical development. In this Review, we describe the research leading to these breakthroughs and highlight the existence of groups of structurally related PPIs within the PPI target class. For each of these groups, we use examples of successful discovery efforts to illustrate the research strategies that have proved most useful.