Telotristat ethyl to enhance cytotoxic chemotherapy response in preclinical cholangiocarcinoma models.

Abstract

331 Background: Cholangiocarcinoma (CCA) is the second-most common primary liver cancer after hepatocellular carcinoma. It has a poor prognosis with a 5-year survival rate of 5-15%. The current standard first-line therapy for advanced unresectable CCA is a combination of gemcitabine and cisplatin (GemCis) chemotherapy that leads to a median survival of 6-12 months. Nanoparticle albumin-bound paclitaxel ( nab-paclitaxel, NPT) is an approved therapy for breast, NSCLC and pancreatic cancer. Elevated levels of serotonin have been reported in CCA that has protumorigenic activity. We tested the hypothesis that telotristat ethyl (TE), an inhibitor of serotonin biosynthesis, has antitumor activity in CCA and it augments GemCis and nab-paclitaxel response in preclinical CCA models. Methods: Tumor growth experiments were performed in mice subcutaneous CCA intrahepatic CCLP-1 xenografts, extrahepatic TFK-1 xenografts and patient-derived xenografts. Animal survival studies were performed using human CCA intrahepatic CCLP-1 cells in the peritoneal dissemination model in NOD/SCID mice. Results: In intrahepatic CCLP-1 subcutaneous xenografts, compared with controls, reduction in tumor growth was observed by TE (53%), GemCis (53%) or NPT (69%). The combination of TE with GemCis or NPT exhibited an additive tumor growth inhibition response, GemCis+TE (85%) and NPT+TE (90%). In extrahepatic TFK-1 subcutaneous xenografts, TE led to a significant reduction in tumor growth (51%), while GemCis and NPT reduced tumor growth by 37% and 56%, respectively. Again, an additive tumor growth inhibition effect was observed by the addition of TE to chemotherapy, GemCis+TE (67%) and NPT+TE (74%). In CCA patient-derived subcutaneous xenografts, GemCis caused the greatest tumor growth reduction (80%) followed by NPT (57%) and TE (40%). Combinations increased tumor inhibition further: GemCis+TE (95%) and NPT+TE (91%). Mouse survival in peritoneal dissemination xenografts was only marginally enhanced by TE (11%) or GemCis (9%) while NPT led to a substantial extension (60%). Interestingly, the combination of TE with GemCis or NPT demonstrated a further extension in mice survival: GemCis+TE (26%) and NPT+TE (68%). Conclusions: TE had antitumor activity and it enhanced chemotherapy effects in several CCA preclinical models indicating that this therapeutic combination has the potential to ameliorate clinical therapy for CCAs of different origin.