BRD4 and breast cancer: A small number of MDM2‐based PROTACs have been developed by using either Nutlin‐3a (IC50 = 90 nM)[25] or Idasanutlin (RG7388, IC50 = 6 nM)[26] to degrade the androgen receptor (AR) in cervical carcinoma HeLa cells transiently expressing AR,[27] bromodomain‐containing protein 4 (BRD4) in colorectal cancer cell line HCT116,[28] poly (ADP‐ribose) polymerase 1 (PARP1) in breast cancer cell line MDA‐MB‐231,[29] and MDM2 itself in non‐small cell lung cancer cell line A549 (Figure 1A,B).[30]