Targetingthese factors can significantly impact the treatment of specific malignancies, asexemplified by the clinical success of agents targeting the androgen receptor (AR)in prostate cancer and estrogen receptor (ER) in breast cancer.39 Conventional small-molecule drugs exerttheir effects by binding to defined pockets on target protein surfaces, such as theligand binding domains of AR and ER. The gene discussed is ESR1; the disease is prostate cancer.