A proteolysis targeting chimera (PROTAC) is a small molecule composed of two active domain-binding molecules and a linker capable of removing specific unwanted proteins. one domain-binding molecule capable of engaging an E3 ubiquitin ligase, and another that binds to a target protein meant for degradation. Recruitment of the E3 ligase to the target protein results in ubiquitination and subsequent degradation of the target protein by the proteasome. Because PROTACs need only to bind their targets with high selectivity (rather than inhibit the target protein's enzymatic activity), there are currently many efforts to retool previously ineffective inhibitor molecules as PROTACs for next-generation drugs.