ESR1 and breast cancer: Phase I trials showed that seribantumab has a favorable toxicity profile as a single agent and in combination with chemotherapy or anti-EGFR and PI3K inhibitors.[116–118] A phase II trial evaluated the combination of exemestane +/- seribantumab in post-menopausal women with advanced ER- and/or PR-positive HER2-negative breast cancer (NCT01151046).