Advancing target validation with PROTAC technology

Targeted protein degradation (TPD) is a cutting-edge technology that provides new avenues for drug discovery and development. PROteolysis TArgeting Chimeras (PROTACs) are the most established and advanced TPD strategy, enabling the selective degradation of disease-associated and 'undruggable' proteins of interest (POIs) by leveraging the cell's natural protein degradation machinery. To confirm that PROTAC-induced proximity drives protein degradation, target validation and ternary complex formation must be thoroughly assessed. In this perspective, the authors detail some of the most widely used in silico, structural, in vitro, and in cellulo methods to validate PROTAC target engagement and ternary complex formation. Additionally, they discuss the growing use of PROTACs as chemical probes for novel target identification and validation. Target validation is essential in the PROTAC approach, and ongoing PROTAC studies should prioritize confirming ternary complex formation using assays conducted under physiologically relevant cellular conditions. The authors believe that proteomics analyses are among the most valuable tools for elucidating the mechanism, selectivity, and outcomes of PROTACs. They also remain optimistic about the future of PROTACs in drug development and their use as probes to confirm target engagement. While PROTAC technology is rapidly advancing, it still holds vast opportunities for future exploration, offering significant potential to further both chemical and biological research and to drive the development of new drugs.