The aim of this study was to assess the antitumor activity of duligotuzumab, an anti HER3/EGFR antibody or ipatasertib, an AKT inhibitor, combined with trastuzumab in a panel of HER2-positive human gastric cancer cells (GCC), and the efficacy of such combinations in HER2-resistant cells. Here, ERBB3 is linked to gastric cancer.