Background: Biliary tract cancers (including cholangiocarcinomas) are rare but aggressive malignancies with limited options for treatment. Currently, the combination of gemcitabine and cisplatin is considered the upfront systemic chemotherapy for patients with advanced and metastatic diseases. There is no ‘standard’ for second-line treatment. Several signaling pathways have been identified that might play a role in the development of biliary tract cancer and that may represent targets for directed therapies. Overexpression of VEGF and alterations of the Ras/Raf pathway have been identified in the majority of cholangiocarcinoma; some studies have shown these mutations to be associated with metastasis and poorer prognosis. Regorafenib is an oral multikinase inhibitor of multiple angiogenic and oncogenic kinases (VEGFR1-3, TIE2, PDGFR-β, FGFR1, KIT, RET, RAF) which has shown efficacy as a single agent in multiple solid tumors. This study evaluates the efficacy of regorafenib in patients with advanced/metastatic biliary tract cancer following the failure of first-line chemotherapy. Methods: Enrollment in this phase II, single-arm trial is ongoing. Eligible patients have unresectable advanced or metastatic biliary tract adenocarcinoma, and have failed first-line systemic chemotherapy. Patients receive regorafenib 120 mg orally daily in a 21 days on, 7 days off cycle. Tumor measurements take place every 3 cycles by CT or MRI imaging. Patients continue on therapy until disease progression or unacceptable toxicities. The primary end point of this study is median progression-free survival (PFS). To evaluate for evidence of activity, defined as a median PFS of 3.5 months or greater, with 83% power (one-sided test, α=0.10), target enrollment is 37 patients. Secondary endpoints include safety, overall response rate, disease control rate, median overall survival, and changes in biomarker levels. The correlation of these biomarkers and of tumor mutations with response to treatment is built into the study as well. As of September 2014, 9 patients had been enrolled. ClinicalTrials.gov Identifier: NCT02053376. Clinical trial information: NCT02053376