ESR1 and breast cancer: In addition, the fact that the effect of Tel on ERα degradation is generally comparable to that of the antiestrogens (i.e., competitive ERα antagonists that induce ERα degradation via the 26S proteasome [23,24]) fulvestrant (ICI182,780-ICI), AZD9496 (AZD) and brilanestrant (GDC-0810 GDC) in MCF-7, T47D-1, BT-474 and Y537S cells (Figure 1c) indicates that this drug could work in a manner similar to that of SERDs in BC cells.