We have previouslyobserved this preference for short BRD4 isoform degradation over thelong isoform in HEK293T cells with covalent degraders, which was notevident in other cell lines.,, Similarly, we observed potent degradation of both long and shortisoforms of BRD4 with HRG038 in MDA-MB-231 breast cancer cells (Figure b). Here, BRD4 is linked to breast cancer.