ESR1 and breast cancer: As exemplified by the clinical candidates ARV‐110 and ARV‐471, respectively, it has been possible to develop PROTACs against targets previously considered undruggable, including androgen receptor (AR) in prostate cancer and estrogen receptor (ER) in breast cancer, as illustrated in (Figure 2) (Dogheim and Amralla 2023; Snyder et al. 2025).