Proteolysis targeting chimeras (PROTACs) are bivalent ligands in which a compound that binds to the protein target of interest is connected to a second molecule that binds an E3 ligase via a linker. Potentially, a mode of action whereby a target protein is degraded has several advantages over a more traditional therapeutic approach based on inhibition. First, a PROTAC compound only needs to bring the E3 protein close to the target of interest. The PROTAC ligand acts like a catalyst, and even sub-stoichiometric amounts of a PROTAC therapeutic can be expected to achieve (near) complete protein degradation. In the absence of small-molecule E3 binders, other peptidic PROTACs were developed that were sufficiently small to be cell permeable. E3 ligase ligands used for PROTACs including:  thalidomide derivatives targeting Cereblon. Bestatin and compound 7 are ligands of cIAP, nutlin is a ligand of MDM2.

References

1.Scheepstra M,et al. Comput Struct Biotechnol J. 2019;17:160–176.