Two of the proteolytic targeting chimeras, ARV-110 (NCT03888612) and ARV-471 (NCT04072952) have successfully made it to phase-II clinical trials, ARV-110 for metastatic castration-resistant prostate cancer, and ARV-471 for metastatic ER+/HER2− breast cancer.558. This evidence concerns the gene ESR1 and breast cancer.