In the trial, 732 patients with HR+/HER2-negative advanced breast cancer who had experienced disease progression on endocrine therapy, for whom further endocrine therapy was unsuitable, and who had received 1-2 lines of prior chemotherapy were randomized to receive either Dato-Dx (365 patients) or investigator’s choice of chemotherapy (ICC) (eribulin, vinorelbine, capecitabine, or gemcitabine) (367 patients). The gene discussed is ERBB2; the disease is breast cancer.