Inclusion Criteria:

          -  Has confirmed biliary tract cancer

          -  Ability to understand and willingness to sign a written informed consent document.

          -  Age ≥18 years

          -  Have biopsiable disease

          -  Eastern Cooperative Oncology Group (ECOG) performance status 0 or 1

          -  Patient must have adequate organ function defined by the study-specified laboratory
             tests.

          -  Must use acceptable form of birth control while on study.

        Exclusion Criteria:

          -  Has active autoimmune disease that requires systemic treatment.

          -  Has a known additional malignancy that is progressing or has required active treatment
             within the past 2 years or that is expected to require active treatment within two
             years.

          -  Prior treatment with immunotherapy agents (including, anti-PD-1, anti-PD-L1,
             anti-PD-L2, anti-CTLA4, etc.).

          -  Has known central nervous system (CNS) metastases and/or carcinomatous meningitis.

          -  Has evidence of interstitial lung disease or active, non-infectious pneumonitis.

          -  Has evidence of an uncontrolled, active infection requiring parenteral anti-bacterial,
             anti-viral or anti-fungal therapy ≤ 7 days prior to administration of study
             medication.

          -  Has received a blood transfusion within 72 hours prior to first dose of study drug
             administration

          -  Unwilling or unable to follow the study schedule for any reason.

          -  Major surgery within 4 weeks prior to initiation of study treatment.

          -  Patient with uncontrolled intercurrent illness including, but not limited to,
             uncontrolled infection, symptomatic congestive heart failure, unstable angina
             pectoris, cardiac arrhythmia, significant muscle disorders or psychiatric
             illness/social situations that would limit compliance with study requirements.

          -  Pregnant or breastfeeding women.

          -  Have known history of infection with HIV, hepatitis B, or hepatitis C.

          -  Received any prophylactic vaccine within 30 days of first dose of study drug
             treatment.

          -  Has a history of allergy to study treatments or any of its components of the study.