Inclusion Criteria:

          -  Age ≥18 years.

          -  ECOG performance status 0 or 1

          -  Have metastatic or locally advanced microsatellite stable (MSS) colorectal
             adenocarcinoma.

          -  Cohort A: Primary lesion has a composite PD-L1/Mucin (CPM) score ≥ 15%.

          -  Cohort B: Primary lesion has a composite PD-L1/Mucin (CPM) score < 15%.

          -  Cohort C: Prior surgical resection of primary tumor. Prospective biomarker evaluation
             not required.

          -  Must have received at least one chemotherapy regimen.

          -  Patients with the presence of at least one measurable lesion using RECIST 1.1.

          -  Patients must have available archival tissue from the surgical resection of their
             primary tumor.

          -  Patient's acceptance of tumor biopsies.

          -  Life expectancy of greater than 3 months.

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

          -  Documented LVEF ≥ 50% - 6 month prior to drug administration.

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

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

        Exclusion Criteria:

          -  Known history or evidence of brain metastases. Patients with previously treated brain
             metastases may participate if they are stable for 4 weeks prior to beginning
             treatment, have no new or enlarging brain metastases, and are not using steroids for
             at least 1 week prior to initiation of study treatment.

          -  Require any antineoplastic therapy.

          -  History of prior treatment with anti-PD-1, anti-PD-L1, anti-PD-L2, anti-CTLA-4, or
             anti-Lag-3 antibodies.

          -  Had chemotherapy, radiation, or steroids within 14 days prior to study treatment.

          -  Had any cytotoxic drug within 4 weeks prior to initiation of study treatment.

          -  Hypersensitivity reaction to any monoclonal antibody.

          -  Has uncontrolled intercurrent acute or chronic medical illness.

          -  Has an active known or suspected autoimmune disease.

          -  Has a diagnosis of immunodeficiency.

          -  Prior tissue or organ allograft or allogeneic bone marrow transplantation.

          -  Requires daily supplemental oxygen

          -  History of interstitial lung disease.

          -  Significant heart disease

          -  History of encephalitis, meningitis, or uncontrolled seizures in the year prior to
             informed consent.

          -  Infection with HIV or hepatitis B or C at screening.

          -  Has an active infection.

          -  Unable to have blood drawn.

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

          -  Woman who are pregnant or breastfeeding.