To show general applicability of our heterotrivalent PROTAC strategy, we designed an AB3067-like compound for targeting BromoTag. 28, 43 BromoTag is our recently reported inducible degradation system that leverages an engineered Leu-Ala version of BRD4-BD2 as universal tag for targeted protein degradation. 28 We designed and synthesized compound AB3145 (97), which (analogously to VHL-based bifunctional degrader AGB1) bears an ethyl-"bump" into the BET ligand, allowing for exquisite selectivity towards the BromoTag while sparingly degrading of endogenous BET proteins. To make the heterotrivalent BromoTag PROTAC, we followed a similar synthesis to 27 (c.f. Scheme 3), but now using the BromoTag selective ligand ). Crucially, 97 proved to be 10 to 100-fold more potent than the current BromoTag degrader AGB1