Palazestrant (OP-1250)is under investigation in a phase I/II trial of heavily pretreated pre- and post-menopausal patients with HR+, HER2− MBC; preliminary results demonstrated anti-tumor activity (ORR 9%, CBR 21%) and drug tolerability (the majority of TEAEs were grade 1–2, with nausea, fatigue, and constipation being the most prevalent) [121] (Table 5). Here, ERBB2 is linked to neoplasm.