A phase 1b study was conducted in patients with HER2+ breast cancer to evaluate the combination of entinostat and lapatinib with or without trastuzumab (ClinicalTrials.gov Identifier: NCT01434303; Phase I and Phase I Trastuzumab Cohort Study of Entinostat, Lapatinib and Trastuzumab in Patients With HER2-Positive Metastatic Breast Cancer in Whom Trastuzumab Has Failed; Table 1). This evidence concerns the gene ERBB2 and breast cancer.