Since conventional chemotherapy (gemcitabine and cisplatin) has marginal survival benefit in patients with advanced cholangiocarcinoma (CCA), an effective targeted therapeutic agent is urgently required. Activation of the PI3K/Akt/mTOR signaling pathway is frequently observed in CCA, and thus, PI3K and mTOR are promising therapeutic targets in CCA. Recently a new dual PI3K/mTOR inhibitor GDC-0980 (apitolisib) was introduced. This study was undertaken to examine the activity of apitolisib against CCA cells in vitro and in vivo. Apitolisib treatment strongly reduced Akt and mTOR active phosphorylation levels and attenuated cell growth in two different CCA cell lines (SNU478 and SNU1196). In addition, the cytotoxic activity of apitolisib enhanced the effects of gemcitabine or cisplatin in vitro and increased PARP cleavage. Moreover, we observed these co-treatments significantly reduced colony formation by SNU478 and SNU1196 cells and potently inhibited tumor growth in a mouse xenograft model. The results of the present study show that apitolisib effectively reduces CCA cell growth by suppressing the PI3K/Akt/ mTOR pathway. In addition, co-treatments with apitolisib and gemcitabine or cisplatin synergistically enhanced apitolisib activity, which suggests a means of improving the chemotherapeutic sensitivity of CCA. (c) 2020 Elsevier Inc. All rights reserved.