Background: There is no standard second-line therapy for advanced biliary tract carcinoma (BTC). Apatinib, a VEGFR2 tyrosine kynase inhibitor, showed an inhibitary effect on tumor formation in BTC tumorgraft mouse model in previous study, with tolerable toxicity in clinical trials for other types of advanced cancer such as gastric cancer. We conducted an exploratory study to evaluate the efficacy and safety of apatinib in patients with advanced BTC. Methods: This is a single-center, single-arm phase II study (NCT03427242). The key inclusion criteria were:(1) histologically confirmed advanced or metastatic BTC; (2) Prior lack of response or intolerance to at least one chemotherapeutic regimens; (3) At least one measurable lesion as defined by RECIST 1.1; (4) No prior use of anti-angiogenic targeted drugs. Eligible patients received oral apatinib 500mg each day continuously until unacceptable toxicity or tumor progression. The primary endpoint was progression free survival (PFS). The secondary endpoints were overall survival (OS), objective response rate (ORR), disease control rate (DCR) and treatment safety. Results: From Dec 1, 2017 to Jan 31, 2020, a total of 18 patients (12 males and 6 females) had been recruited, and 16 patients who had received the medication of apatinib were included in this analysis. Among these patients, 10 were previously treated with only first-line chemotherapy and 6 were treated with two or more lines of therapy. The median age was 65 (range 45-76) years old. Fourteen patients had received the efficacy evaluation after treatment. Two patients achieved partial response (PR, 14.3%), 6 patients with stable disease (SD, 42.9%),and 6 patients with progressive disease(PD). The ORR and DCR were 14.3% and 57.1%, respectively. At the last follow-up date on Jan 30, 2020, 4 patients are still on apatinib medication. The median PFS was 2.70 months (95% CI, 1.94 - 3.46), and the median OS was 7.03 months (95% CI, 3.16 - 10.9). Grade 3 or 4 adverse events were reported in 7 patients (43.8%). The detailed grade 3 or 4 adverse events were proteinuria in 5 patients, hand-foot syndrome in 2 patients, platelet count decrease in 1 patients, diarrhea in 1 patients and urine bilirubin in 1 patients (Table). Conclusions: For the patients with advanced biliary tract carcinoma, apatinib showed an anti-tumor activity with acceptable safety. Clinical trial information: NCT03427242.