Inclusion Criteria:

          -  Must have histologically confirmed FLC (fibrolamellar hepatocellular cancer) that is
             metastatic or unresectable.

          -  Presence of DNAJB1-PRKACA fusion transcript, assessed by RNA-sequencing, DNA
             sequencing, or in situ hybridization in the archival tissue.

          -  Age ≥12 years. Note: Subjects age ≥ 12 years but <18 are eligible to enroll only after
             6 adult patients have enrolled on the study.

          -  Patients < 18 years old must have a body weight ≥40 kg.

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

          -  Patients must have adequate organ and marrow function defined by study-specified
             laboratory tests prior to initial study drug.

          -  Patients must have measurable disease per RECIST 1.1.

          -  Patients ≥ 18 years old must have an accessible non-bone tumor lesion from which
             serial core biopsy specimens can be obtained.

          -  Must be willing to provide tissue and blood samples for mandatory translational
             research.

          -  Woman of childbearing potential must have a negative pregnancy test and follow
             contraceptive guidelines as defined per protocol.

          -  Men must use acceptable form of birth control while on study.

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

        Exclusion Criteria:

          -  Have had chemotherapy or other systemic therapy or radiotherapy, as follows:

               -  Have had chemotherapy, biological cancer therapy, or radiation 14 days prior to
                  the first dose of study drug.

               -  Have had surgery within 28 days of dosing of investigational agent, excluding
                  minor procedures (dental work, skin biopsy, etc.), celiac plexus block, and
                  biliary stent placement.

               -  Have received other approved or investigational agents or device within 28 days
                  of the first dose of study drug.

               -  Have not recovered from acute adverse events to grade ≤1 or baseline due to
                  agents administered

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

          -  Have received any non-oncology live vaccine therapy used for prevention of infectious
             diseases within 28 days of study treatment

          -  Known sensitivity to or history of allergic reactions to investigational drug (s).

          -  Hypersensitivity reaction to any monoclonal antibody.

          -  Has active autoimmune disease that has required systemic treatment in the past 2
             years, or a documented history of clinically severe autoimmune disease, or a syndrome
             that requires systemic steroids or immunosuppressive agents.

          -  Presence of any tissue or organ allograft, regardless of need for immunosuppression,
             including corneal allograft. Patients with a history of allogeneic hematopoeitic stem
             cell transplant will be excluded.

          -  Has a diagnosis of immunodeficiency.

          -  Systemic treatment with either corticosteroids (>10 mg daily prednisone equivalents)
             or other immunosuppressive medications within 7 days of study drug administration.

          -  Symptomatic interstitial lung disease.

          -  Has a pulse oximetry of <92% on room air or is on supplemental home oxygen.

          -  Active or untreated brain metastases or leptomeningeal metastases.

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

          -  Are pregnant or breastfeeding.

          -  Infection with HIV or hepatitis B or C.

          -  Have had evidence of active or acute diverticulitis, intra-abdominal abscess, or GI
             obstruction.

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

          -  Any other sound medical, psychiatric, and/or social reason as determined by the
             Investigator.

          -  Any illicit drugs or other substance abuse.

          -  Clinically meaningful ascites.