Inclusion Criteria:

          -  Male or female patients aged ≥18 years

          -  Patients with histologically confirmed advanced/metastatic RAS/RAF wild type colon or
             rectal adenocarcinoma who had a prior radiological response to EGFR blockade as a
             single agent or in combination with chemotherapy but have subsequently progressed/
             become refractory to this treatment based on physician judgment. Patients should not
             have received any other systemic anti-cancer therapy between the end of treatment with
             EGFR inhibitors as a single agents or in combination with chemotherapy and screening
             for the iSCORE study

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

          -  Estimated life expectancy of at least 3 months at the time of informed consent per
             Investigator assessment

          -  Adequate organ functioning including haematological, renal, liver and cardiac function

          -  Negative serum or urine pregnancy test at screening for women of childbearing
             potential and use of highly effective contraception for both male and female patients
             throughout the study

          -  Patient must consent and be eligible to undergo mandatory baseline and sequential
             biopsies

          -  Presence of measurable disease as defined by RECIST v 1.1 criteria for response
             assessment

        Exclusion Criteria:

          -  Systemic therapy within 4 weeks prior to the planned administration of the first study
             treatment dose

          -  Major surgery within 4 weeks or radiation therapy within 14 days prior to study entry.
             Prior palliative radiotherapy to metastatic lesion(s) is permitted, provided it has
             been completed 48 hours prior to study entry and there is at least one measurable
             lesion that has not been irradiated.

          -  Previous exposure to immune checkpoint inhibitors or immune co-stimulatory drugs

          -  Uncontrolled or significant cardiovascular disease including including patients with a
             history of myocarditis, regardless of aetiology

          -  Known severe hypersensitivity reactions (Grade ≥ 3 NCI CTCAE v 5.0) to monoclonal
             antibodies or related compounds or any of their components

          -  Current use of immunosuppressive medication, EXCEPT for the following: a. intranasal,
             inhaled, topical steroids, or local steroid injection (e.g., intra-articular
             injection); b. Systemic corticosteroids at physiologic doses ≤ 10 mg/day of prednisone
             or equivalent; c. Steroids as premedication for hypersensitivity reactions (e.g., CT
             scan premedication)

          -  Known history of testing positive test for human immunodeficiency virus (HIV) or known
             acquired immunodeficiency syndrome (AIDS)

          -  Positive test for HBV surface antigen and / or confirmatory HCV RNA (if anti-HCV
             antibody tested positive)

          -  Active, known or suspected autoimmune disease that might deteriorate when receiving an
             immuno-stimulatory agent. Patients with type I diabetes mellitis, hypothyroidism only
             requiring hormone replacement, skin disorders (such as vitiligo, psoriasis, or
             alopecia) not requiring systemic treatment, or conditions not expected to recur in the
             absence of an external trigger are permitted to enroll

          -  Patients with a history of interstitial lung disease or radiological evidence of
             pulmonary fibrosis

          -  Pregnancy or lactation

          -  Vaccination within 4 weeks of the first dose of study drugs and while on trial is
             prohibited except for administration of inactivated vaccines