Introduction: Cholangiocarcinoma (CCA) is rising in incidence while prognosis remains poor. CCA contains a collagen-rich, desmoplastic stroma that promotes an immunosuppressive tumor microenvironment (TME). Lysyl oxidases (LOX) consist of 5 secreted enzymes (LOX, LOXL1-4) that catalyze collagen cross-linking and high LOX expression correlates with poor prognosis across a variety of solid malignancies. Here, we show the benefit of combination therapy with pan-LOX inhibition in murine models of CCA. Methods: Mice with activated Kras and loss of p53 spontaneously develop CCA. A syngeneic CCA cell line was developed from a KPPC tumor and surgically implanted in livers of C57BL/6 mice. Disease onset was monitored with ultrasonography (US) and treatment consisted of chemotherapy with or without PXS-5505 (pan-LOX inhibitor, Pharmaxis, Ltd.). Immunohistochemistry was performed on tumors to characterize changes in the TME. Results: KPPC mice treated with combination therapy demonstrate significantly decreased tumor growth (p<0.0001) and delayed ascites onset (p=0.02) compared to chemotherapy alone (Figure 1A and 1B). KPPC mice treated with combination therapy show improved overall survival (p=0.011) compared to chemotherapy alone (Figure 1C). Orthotopic CCA tumors treated with combination therapy demonstrate decreased tumor cross-sectional area at day 25 (p=0.0002) after initiation of treatment and improved overall survival (p=0.04) compared to chemotherapy alone. Tumor-bearing mice treated with combination therapy demonstrated decreased activated fibroblast density compared to chemotherapy alone (p<0.0001). Conclusions: CCA highly expresses LOX and combination therapy with PXS-5505 delays tumor growth and improves overall survival in mouse models of CCA, representing an innovative strategy for treating CCA.