ESR1 and breast cancer: Lucitinib, an inhibitor of FGFR1-3, VEGFR1-3, and PDGFRα/β, was recently tested in a group of metastatic ER+/HER2- breast cancer patients, showing only modest antitumor activity and significant clinical toxicity; exploratory biomarker analyses suggested that patients with FGFR1 amplification or expression may derive a greater benefit from treatment [188].