Currently available drugs are: aromatase inhibitors Als (exemestane, anastrozole and letrozole) resulting in estrogen depletion by blocking the conversion of androgens to estrogens; luteinizing hormone-releasing hormone LH-RH analogs (leuprolide and goserelin), which block the production of hormone from the ovary; tamoxifen, a prodrug that blocks the uptake of estrogen by the endoplasmic reticulum ER; fulvestrant, a selective degrade of ER which is suitable for BC patients refractory to previous hormonal therapy. Here, ESR1 is linked to breast cancer.