ERBB2 and neoplasm: Two phase-II studies evaluated bosutinib in combination with first-line letrozole or second-line exemestane in postmenopausal patients with HR-positive/HER2-negative MBC.21,22 Although these combinations demonstrated anti-tumor activity, both trials were terminated early due to unfavorable safety profiles, including a 26–38% incidence of hepatotoxicity, and with approximately two-thirds of patients experiencing diarrhea.